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Applied Catalysis B, Environmental (v.129, #)

Editorial Board (pp. i).

Outside Back Cover (pp. co4).

Editorial Board (pp. co2).

Continuous-flow photocatalytic treatment of pharmaceutical micropollutants: Activity, inhibition, and deactivation of TiO₂ photocatalysts in wastewater effluent by Sean Carbonaro; Matthew N. Sugihara; Timothy J. Strathmann (pp. 1-12).

Display Omitted► Benchtop continuous-flow reactor with thin film TiO₂ photocatalysts developed. ► Treatment of four model pharmaceutical micropollutants simultaneously monitored. ► Catalysts inhibited and deactivated by non-target wastewater effluent constituents. ► A large fraction of effluent-promoted catalyst inhibition reversible after 4d.Titanium dioxide (TiO₂) photocatalysts have been shown to be effective at degrading a wide range of organic micropollutants during short-term batch experiments conducted under ideal laboratory solution conditions (e.g., deionized water). However, little research has been performed regarding longer-term photocatalyst performance in more complex matrices representative of contaminated water sources (e.g., wastewater effluent, groundwater). Here, a benchtop continuous-flow reactor was developed for the purpose of studying the activity, inhibition, and deactivation of immobilized TiO₂ photocatalysts during water treatment applications. As a demonstration, degradation of four pharmaceutical micropollutants (iopromide, acetaminophen, sulfamethoxazole, and carbamazepine) was monitored in both a pH-buffered electrolyte solution and a biologically treated wastewater effluent (WWE) to study the effects of non-target constituents enriched in the latter matrix. Reactor performance was shown to be stable over 7d when treating micropollutants in buffered electrolyte, with 7-d averaged k_obs values (acetaminophen=0.97±0.10h⁻¹; carbamazepine=0.50±0.04h⁻¹; iopromide=0.49±0.03h⁻¹; sulfamethoxazole=0.79±0.06h⁻¹) agreeing closely with measurements from short-term circulating batch reactions. When reactor influent was switched to WWE, treatment efficiencies decreased to varying degrees (acetaminophen=40% decrease; carbamazepine=60%; iopromide=78%; sulfamethoxazole=54%). A large fraction of the catalyst activity was recovered upon switching back to the buffered electrolyte influent after 4d, suggesting that much of the observed decrease resulted from reversible inhibition by non-target constituents (e.g., scavenging of photocatalyst-generatedOH). However, there was also a portion of the decrease in activity that was not recovered, indicating WWE constituents also contributed to photocatalyst deactivation (acetaminophen=6% deactivation; carbamazepine=24%; iopromide=16%; sulfamethoxazole=25%). Experiments conducted using pretreated WWE and synthetic WWE mimic solutions indicated that both effluent organic matter and inorganic constituents in WWE contributed to the observed photocatalyst inhibition/deactivation. Analysis of immobilized TiO₂ thin films after 4d of continuous treatment of the WWE matrix indicated minor deterioration of the porous film and formation of surface precipitates enriched in Al and Ca. Results demonstrated the marked influence of non-target constituents present in complex matrices on long-term photocatalyst activity and highlighted the need for further study of this important issue to advance the development of practical photocatalytic water treatment technologies.

Keywords: Wastewater treatment; Water reuse; Emerging contaminant; Photocatalyst; Thin film

Transformation products and reaction kinetics in simulated solar light photocatalytic degradation of propranolol using Ce-doped TiO₂ by Javier Santiago-Morales; Ana Agüera; María del Mar Gómez; Amadeo R. Fernández-Alba; Jaime Giménez; Santiago Esplugas; Roberto Rosal (pp. 13-29).

Display Omitted► We studied the visible-light photocatalytic degradation of propranolol. ► We used cerium-doped titanium dioxide as photocatalyst. ► Oxidation through catalyst holes was the prevailing mechanism. ► We detected over thirty transformation products using LC-ESI-QTOF–MS/MS. ► Toxic transformation products accumulated, displaying toxicity to microorganisms.The visible light photocatalytic degradation of propranolol was studied using cerium doped titanium dioxide, a catalyst that showed an increased light absorption in the visible region. The experiments were carried out in ultrapure water and in a biologically treated wastewater from the secondary effluent of a treatment plant spiked with propranolol. The best results were obtained for a cerium loading of 0.5wt.% and a bulk catalyst concentration of 0.14g/L, with which propranolol became essentially depleted after 1.5h of irradiation. The extent of mineralization reached 17.4% after 6h on stream under the same conditions. Both oxidation on catalyst holes and reaction with hydroxyl radicals contribute to propranolol depletion, but for the reaction conditions tested in this study, the first mechanism predominated and accounted for 60% of the propranolol rate constant. The runs performed in wastewater matrix led to a very low photocatalytic rate compared with pure water, which was attributed to the presence of radical scavengers and competing substances. Over thirty reaction intermediates were detected by means of exact mass measurements performed by liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (LC-ESI-QTOF–MS/MS) based on the characteristic fragmentation of oxidation by-products. Their relative abundance was also assessed in catalytic and non-catalytic runs. The most abundant transformation products could be attributed to the cleavage of the ether bond of propranolol. Other compounds detected derived from the addition of hydroxyl groups to the aromatic nuclei or to the ring-opening attack of hydroxyl radicals on the naphthol moiety. Finally, the toxicity of oxidized mixtures was determined using the green algae Pseudokirchneriella subcapitata and the bioluminescent marine bacterium Vibrio fischeri. Although the toxicity of treated mixtures tended to decrease as propranolol was depleted, mixtures treated in pure water may lead to the accumulation of toxic transformation products.

Keywords: Propranolol; Solar photocatalysis; Transformation products; Liquid chromatography; Mass spectrometry

Promoting effect of calcium doping on the performances of MnO_x/TiO₂ catalysts for NO reduction with NH₃ at low temperature by Tingting Gu; Ruiben Jin; Yue Liu; Hongfeng Liu; Xiaole Weng; Zhongbiao Wu (pp. 30-38).

Display Omitted► The addition of Ca has strong promoting effect on low temperature SCR activity over MnO_x/TiO₂. ► The strong interaction after Ca doping leads to the increase in surface area and dispersion. ► The doping of Ca greatly increases the adsorption and oxidation of NO.In this paper, the Ca doped MnO_x/TiO₂ catalysts were synthesized through a sol–gel method, which exhibited promoting effects on selective catalytic reduction (SCR) of NO with NH₃ at low temperature. The NO conversion of MnO_x/TiO₂ had been greatly improved from ca. 40% to 90% at 140°C after Ca doping. After the catalysts being subjected to a variety of analytical measurements, we observed that the addition of Ca could result in better dispersion of MnO_x on TiO₂, leading to the enhancement of BET surface area and pore volume. This could be attributed to the strong interactions among calcium, manganese oxides and titania. Furthermore, an obvious increase in the amounts of ad-NO_x species, especially monodentate nitrate and NO₂⁻ species, was also observed. All of these would give the contributions to the great improvement of catalytic activity by the addition of Ca.

Keywords: NH; ₃; -SCR; Low temperature; Ca doping; MnO; _x; /TiO; ₂

Biodiesel production from Jatropha curcas crude oil using ZnO/SiO₂ photocatalyst for free fatty acids esterification by Grisel Corro; Umapada Pal; Nallely Tellez (pp. 39-47).

The use of heterogeneous photocatalytic process at room temperature can be a new way to perform the esterification of free fatty acids in vegetable oils for the efficient production of biodiesel. ZnO/SiO₂ as a heterogeneous photocatalyst presented high activity and stability for the esterification of free fatty acids present in Jatropha curcas oil with methanol. The process led to the production of high quality biodiesel.Display Omitted► Production of biodiesel from Jatropha curcas oil by photocatalytic esterification. ► Use of ZnO/SiO₂ as highly active catalyst for photocatalyic esterification of FFA. ► The catalyst is reusable even after 10 cycles of utilization. ► The process can generate biodiesel of high purity that meets the quality demands.We report the production of biodiesel from Mexican Jatropha Curcas crude oil (JCCO) by a two step catalytic process. The high content of free fatty acids (FFA) present in JCCO was first esterified with methanol by a photocatalytic process under UV irradiation using ZnO/SiO₂ as the heterogeneous photocatalyst. The solid catalyst was found to be highly active for the heterogeneous photocatalyic esterification of FFA with methanol. The activity of the solid catalyst remained unchanged even after 10 esterification runs, indicating that the heterogeneous photocatalysis is a viable option for FFA esterification reactions for biodiesel production. Transesterification step was catalyzed by NaOH through thermal activation process. Produced biodiesel fulfills all the international requirements for its utilization as a fuel. A probable reaction mechanism for the esterification process is proposed considering the generation of H⁺, CH₃O· and R-COOH on the photocatalyst surface.

Keywords: Biodiesel; Photocatalytic esterification; Jatropha curcas; oil; Heterogeneous photocatalyst

Enhanced photoactivity of Cu-deposited titanate nanotubes for removal of bisphenol A by Ruey-an Doong; Sue-min Chang; Chia-wei Tsai (pp. 48-55).

Display Omitted► The one-dimensional titanate nanotubes (TNTs) have been successfully fabricated at 150°C for 24h. ► The photodeposition of 0.5–2wt% Cu(II) enhances the photocatalytic activity of TNTs. ► The pseudo-first-order rate constants for BPA photodegradation were 1.8–5.2 times higher than those of P25. ► The copper ions serve as the electron mediators to prolong the retention time of photo-generated radicals.One-dimensional nanotubes are promising nanostructured materials for a wide variety of environmental applications. In this study, the Cu-deposited titanate nanotubes (TNTs) were fabricated using an alkaline hydrothermal method at 150°C and then 0.5–2wt% Cu(II) ions were photodeposited onto the calcined TNTs at 500°C for enhanced photodegradation of bisphenol A (BPA) under illumination of 365nm UV light. The as-synthesized TNTs showed tubular structures with the outer diameter and inter-layer spacing of 7–10 and 0.8nm, respectively. The X-ray absorption near-edge spectral results provided a strong support on the partially structural change from layered trititanate to anatase TiO₂ through the distortion of octahedral TiO₆ unit at 500°C and the production of mixture of CuO and Cu₂O after photodeposition of Cu ions, resulting in the formation of Cu-deposited TiO₂/TNT nanocomposites to enhance the photocatalytic activity. A nearly complete removal of BPA by the Cu-deposited TiO₂/TNTs was observed, and the pseudo-first-order rate constants ( k_obs) for BPA photodegradation by Cu-deposited TiO₂/TNTs at pH 7.0 were 1.8–5.2 and 4.3–12.7 times higher than those of pure Degussa P25 and ST01 TiO₂, respectively. In addition, the k_obs for BPA photodegradation reached the maximum value of 0.253±0.032min⁻¹ at 1wt% Cu(II). The X-ray photoelectron spectra showed that the ratio of Cu₂O to total Cu increased from 3.2% in the dark to 35.2% after illumination of 365nm UV light for 5min. In addition, electron paramagnetic resonance results indicated that the copper ions could serve as the electron mediators to prolong the retention time of photo-generated radicals, resulting in the enhancement of photodegradation efficiency and rate of BPA by Cu-deposited TiO₂/TNTs.

Keywords: Copper ions; Titanate nanotubes (TNTs); Bisphenol A; Photodeposition; Photocatalytic activity

Photocatalytic activity of Cu²⁺/TiO₂-coated cordierite foam inactivates bacteriophages and Legionella pneumophila by Hitoshi Ishiguro; Yanyan Yao; Ryuichi Nakano; Masayuki Hara; Kayano Sunada; Kazuhito Hashimoto; Jitsuo Kajioka; Akira Fujishima; Yoshinobu Kubota (pp. 56-61).

.Display Omitted► Cu²⁺/TiO₂-coated cordierite foam was developed. ► Cu²⁺/TiO₂ cordierite foam has antiviral activity. ► High antiviral activity with Cu²⁺/TiO₂-coated cordierite foam than TiO₂-coated foam. ► Application of the methodology for the evaluation of antibacterial to antiviral.We investigated the antiviral activity of TiO₂-coated cordierite foam used in air cleaners, as well as the evaluation methodology. Furthermore, we developed Cu²⁺/TiO₂-coated cordierite foam and investigated the reduction in viral infection ratio. The method for evaluation of antibacterial activity of TiO₂-coated cordierite foam could also be applied to evaluation of antiviral activity. We showed that Cu²⁺/TiO₂-coated cordierite foam reduced the viral infection ratio to a greater extent than TiO₂-coated cordierite foam. Our findings suggest that the infection risk by polluted air could be decreased using Cu²⁺/TiO₂-coated cordierite foam in air cleaners.

Keywords: Abbreviations; EDS; energy dispersive X-ray spectroscopy; SEM; scanning electron microscopy; TiO; ₂; titanium dioxide; UV; ultravioletBacteriophages; Photocatalysis; Cu; ²⁺; TiO; ₂; Air cleaning filters

TiO₂ decoration of graphene layers for highly efficient photocatalyst: Impact of calcination at different gas atmosphere on photocatalytic efficiency by Adel A. Ismail; R.A. Geioushy; Houcine Bouzid; Saleh A. Al-Sayari; Ali Al-Hajry; Detlef W. Bahnemann (pp. 62-70).

Display Omitted► A facile decoration of graphene oxide (GO) with TiO₂ (1–10%) has been demonstrated. ► HRTEM images show the multi-layers TiO₂–GO sheets with thicknesses ∼2.4nm. ► TiO₂–GO calcining in N₂/H₂, shows a higher photocatalytic activity than those treated in N₂ and O₂. ► The photoactivity by TiO₂–G are faster 6 and 2 times than that by P25 and TiO₂–GO respectively.Graphene based two-dimensional carbon nanostructures serve as a support to disperse TiO₂ nanoparticles. Here, a facile decoration of graphene oxide (GO) and reduced graphene oxide (G) sheets with TiO₂ nanoparticles at different contents (1–10%) has been demonstrated. Then the as-prepared TiO₂–GO samples were heat treated at 450°C under oxidizing (O₂), inert (N₂) and (Ar) and reducing (N₂/H₂) conditions to obtain multi-layers TiO₂–GO and TiO₂–G nanocomposites. The findings indicated that the lattice fringes of TiO₂ anatase exhibit the typical distances of (101) (3.54Å) with high crystallinity. HRTEM images show the multi-layers TiO₂–G sheets with thicknesses ∼2.4nm. The newly prepared multi-layers TiO₂–GO and TiO₂–G nanocomposites have been compared with a commercial photocatalyst P-25 by the determination of their photocatalytic efficiencies for degradation of methylene blue. It can be observed that when TiO₂–GO calcining in N₂/H₂, the produced TiO₂–G shows a higher photocatalytic activity than those treated in N₂ and O₂. Also, the photocatalytic degradation rates of MB by TiO₂–G are faster 6 and 2 times than that by P25 and TiO₂–GO respectively, which is due to the better contact between G and TiO₂ and the more effective charge transfer from TiO₂ to G multi-layers. From the economic point of view, the consumed amount of TiO₂–G sheets in photocatalysis process is one fifth of commercial photocatalyst P-25 without loss of photocatalytic performance. Incorporation of TiO₂ nanoparticles onto multi-layers graphene sheets provide greater versatility in carrying out photocatalytic processes.

Keywords: TiO; ₂; Graphene; Layers; Calcination; Gas atmosphere; Photocatalysts

Chemometric assessment and investigation of mechanism involved in photo-Fenton and TiO₂ photocatalytic degradation of the artificial sweetener sucralose in aqueous media by P. Calza; V.A. Sakkas; C. Medana; A.D. Vlachou; F. Dal Bello; T.A. Albanis (pp. 71-79).

Display Omitted► Photocatalytic degradation of sucralose was quick with both AOPs. ► Optimization of photocatalytic efficiencies were determined by DoE and RSM. ► Intermediates were easily degraded and complete mineralization was achieved within 4h. ► Toxicity evaluation showed detoxification of the irradiated solution after 120min.Chemometric optimization tools were employed, such as experimental design and response surface methodology (RSM) to assess the efficiency of two advanced oxidation processes (AOPs): homogeneous Fenton (Fe^II/H₂O₂) and heterogeneous (TiO₂) photocatalysis for the degradation of the artificial sweetener sucralose. The aqueous samples were irradiated under a variety of experimental conditions (pH, light intensity) and with different amounts of H₂O₂, Fe(II), TiO₂. The use of RSM allowed fitting the optimal values of the parameters leading to the degradation of the contaminant. Also, a single polynomial expression modeling the reaction was obtained for both AOPs.The intermediates formed during the photocatalytic and photo-Fenton process were investigated and characterized by means of HPLC/HRMS. The photocatalysed transformation of sucralose proceeds through the formation of few (eight) products, involving four different pathways: hydroxylation of the molecule, oxidation of the alcohol function, dechlorination and the cleavage of glycoside bond. All the identified intermediates were easily degraded and within four hours of irradiation complete mineralization was achieved. A comparison with Photo-Fenton reaction was also reported.In addition Microtox bioassay ( Vibrio fischeri) was employed in evaluating the ecotoxicity of solutions treated by heterogeneous photocatalysis. Results clearly demonstrate the efficiency of the photocatalytic process in the detoxification of the irradiated solutions.

Keywords: Photocatalysis; Photo-Fenton; TiO; ₂; Experimental design; Sucralose

One-pot synthesis of In₂S₃ nanosheets/graphene composites with enhanced visible-light photocatalytic activity by Xiaoqiang An; Jimmy C. Yu; Feng Wang; Chuanhao Li; Yecheng Li (pp. 80-88).

Novel In2S3 nanosheets/graphene photocatalysts with superior visible light activity were fabricated by a cysteine-assisted hydrothermal method. This work provides new insights into the development of high-efficiency photocatalysts for environmental and energy applications.Display Omitted► In₂S₃ nanosheets/graphene photocatalysts are fabricated by a one-pot synthesis. ► Graphene allows intimate interfacial contact and efficient charge separation. ► The composite shows superior activity for degrading organic dyes and reducing Cr(VI).Novel In₂S₃ nanosheets/graphene photocatalysts were fabricated by a cysteine-assisted one-pot hydrothermal method. Due to the intimate interfacial contact and efficient charge separation, superior visible-light activity for degrading organic dyes and reducing Cr(VI) were achieved. During the decoloring process of methyl orange, the average apparent rate for the as-synthesized composites with 1% graphene was almost 5 times higher than that of pure In₂S₃. This work provides new insights into utilizing In₂S₃/graphene composites as high-efficiency visible-light-driven photocatalysts for environmental remediation and energy conversion.

Keywords: Graphene; Photocatalyst; Indium sulfide

Photocatalytic degradation of 2,4,6-tribromophenol over Fe-doped ZnIn₂S₄: Stable activity and enhanced debromination by Bo Gao; Lifen Liu; Jiadong Liu; Fenglin Yang (pp. 89-97).

Display Omitted► Doping zero valent iron nanoparticles reduced the band gap of ZnIn₂S₄. ► Photocatalytic degradation of 2,4,6-TBP and TOC removal on ZnIn₂S₄ was enhanced by Fe doping. ► Fe-ZnIn₂S₄ was stable, reusable and durable in photocatalysis.Fe doped ZnIn₂S₄ catalyst was prepared and tested for photocatalytic degradation of 2,4,6-tribromophenol (2,4,6-TBP), it was more efficient in debromination and total organic carbon (TOC) removal, compared with TiO₂ (P25) and ZnIn₂S₄. The preparation of Fe-ZnIn₂S₄ involved a facile hydrothermal ZnIn₂S₄ synthesis process at low temperature and without templates, followed by chemical reductive deposition of Fe. The catalysts were characterized using scanning electron microscopy (SEM) equipped with an X-ray energy dispersive spectroscopy (EDS), TEM and HRTEM, FT-IR spectra, X-ray diffraction (XRD) and UV–vis diffuse reflectance spectra. The band gaps of ZnIn₂S₄ and Fe-ZnIn₂S₄ calculated from the onset of the absorption edges were 2.12eV and 2.05eV, respectively. The calculated pseudo-first-order constants ( K_r) were in the order of TiO₂ (0.022min⁻¹)<0.5wt% Fe-TiO₂ (0.0369min⁻¹)2S₄ (0.362min⁻¹)<0.5wt% Fe-ZnIn₂S₄ (0.436min⁻¹). After 1h reaction by Fe-ZnIn₂S₄, the released bromide concentration was 17.6mgl⁻¹, which was 1.11 and 2.69 times higher than ZnIn₂S₄ and TiO₂ (P25), respectively. The increase in TOC removal was 7% and 33% compared to ZnIn₂S₄ and TiO₂ (P25), respectively. The repeated tests proved that the synthesized Fe-ZnIn₂S₄ was stable, reusable and durable in degradation of 2,4,6-TBP. The possible cycle of iron species and a tentative debromination pathway were proposed.

Keywords: Abbreviations; 2,4,6-TBP; 2,4,6-tribromophenol; DBP; dibromophenol; BP; bromophenol; MB; methylene blue; ZVI NPs; zerovalent iron nanoparticles; NZVI; nanoscale zerovalent ironZerovalent iron nanoparticles; Band gap; Photocatalysis; LC MS

Total oxidation of naphthalene using palladium nanoparticles supported on BETA, ZSM-5, SAPO-5 and alumina powders by Francisco J. Varela-Gandía; Ángel Berenguer-Murcia; Dolores Lozano-Castelló; Diego Cazorla-Amorós; David R. Sellick; Stuart H. Taylor (pp. 98-105).

.Display Omitted► Catalysts based on Pd nanoparticles on BETA, ZSM-5, SAPO-5 and γ-Al₂O₃ were prepared. ► These catalysts were tested in the naphthalene total oxidation. ► The catalysts can completely oxidize naphthalene to CO₂ at low temperatures. ► Pd/BETA catalyst is very promising for naphthalene total abatement.A range of catalysts based on Pd nanoparticles supported on inorganic supports such as BETA and ZSM-5 zeolites, a silicoaluminophosphate molecular sieve (SAPO-5) and γ-alumina as a standard support have been tested for the total oxidation of naphthalene (100ppm, total flow 50ml/min) showing a conversion to carbon dioxide of 100% between 165 and 180°C for all the analysed catalysts. From the combined use of zeolites with PVP polymer protected Pd based nanoparticles, enhanced properties have been found for the total abatement of naphthalene in contrast with other kinds of catalysts. A Pd/BETA catalyst has been demonstrated to have excellent activity, with a high degree of stability, as shown by time on line experiments maintaining 100% conversion to CO₂ during the 48h tested.

Keywords: Catalytic oxidation; Zeolite BETA; ZSM-5; Pd nanoparticles; Naphthalene

Highly visible-light active nanoporous TiO₂ photocatalysts for efficient solar photocatalytic applications by Hyun Uk Lee; Soon Chang Lee; Sae Hae Choi; Byoungchul Son; Soo Jae Lee; Hae Jin Kim; Jouhahn Lee (pp. 106-113).

Display Omitted► The nanoporous C- and S-TiO₂ photocatalysts were successfully synthesized at room-temperature. ► The photocatalytic activity of C- and S-TiO₂ was found to be higher than that of other TiO₂ photocatalysts. ► Moreover, C- and S-TiO₂ exhibited excellent antibacterial activity.We report highly visible-light active nanoporous carbon-doped TiO₂ (C-TiO₂) and sulfur-doped TiO₂ (S-TiO₂) for environmental and biomedical applications. C-TiO₂ and S-TiO₂ were synthesized at room temperature without thermal treatment using modified sol–gel processing and ultrasound irradiation. Under visible-light irradiation, the highest photocatalytic activity for S-TiO₂ ([ k]=3.121h⁻¹) was found to be 28 times higher than that of undoped nanoporous TiO₂ ([ k]=0.112h⁻¹). The recyclability of the S-TiO₂ photocatalyst was found to be high with the decolorization rate at ∼92% of the initial value after fifteen cycles. Very interestingly, the C-TiO₂ and S-TiO₂ photocatalysts (crystallite size∼5.5nm) showed very strong antimicrobial properties against both Gram-negative Escherichia coli ( E. coli) and Gram-positive Staphylococcus aureus ( S. aureus) compared to 5nm anatase TiO₂ and undoped TiO₂ photocatalysts after visible-light exposure for 3h. More than ∼95% of E. coli was killed, even after ten cycles of use for the S-TiO₂ photocatalyst. Thus, we have demonstrated that C-TiO₂ and S-TiO₂ can serve as multifunctional generic bactericides, as well as highly visible-light active photocatalysts.

Keywords: Titanium dioxide; Photocatalyst; Sol–gel method; Photocatalytic activity

TiO₂-photocatalyzed transformation of the recalcitrant X-ray contrast agent diatrizoate by Matthew N. Sugihara; Diane Moeller; Tias Paul; Timothy J. Strathmann (pp. 114-122).

Display Omitted► Diatrizoate, an ionic x-ray contrast agent, transformed by UV-TiO₂ photocatalysis. ► In oxic solutions, oxidation mediated by adsorbed hydroxyl radicals. ► Reductive deiodination pathway confirmed in anoxic solutions. ► Iodide released by both oxidative and reductive transformation pathways. ► Reaction rates influenced by solution conditions and non-target water constituents.Iodinated X-ray contrast media (ICM) are biologically recalcitrant chemicals that are often detected in wastewater-impacted environments at higher concentrations than other pharmaceutical micropollutants of concern. Diatrizoate is an anionic ICM that is especially resistant to conventional wastewater and drinking water treatment processes. This study examined the aqueous photocatalytic treatment of diatrizoate using nanophase titanium dioxide (TiO₂). Experiments demonstrated that diatrizoate can be degraded in aqueous TiO₂ suspensions illuminated with ultraviolet-A (UVA) light. In oxic solutions, diatrizoate degraded principally via oxidation by adsorbed hydroxyl radicals (OH), releasing iodine substituents stoichiometrically, but causing little mineralization of organic carbon and nitrogen. Introduction ofOH scavengers significantly slowed the rate of photocatalytic degradation. At circumneutral pH, diatrizoate was oxidized much more slowly than iopromide, a nonionic ICM, in part because of unfavorable electrostatic interactions with the negatively charged TiO₂ surface; increased rates of oxidation observed at lower pH conditions can be attributed to more favorable diatrizoate-TiO₂ sorptive interactions. Experiments also demonstrated that diatrizoate was degraded at appreciable rates in anoxic solutions, and reductive dehalogenation products are identified by liquid chromatography–mass spectrometry. The higher selectivity of reductive processes suggests a promising strategy for targeted treatment of recalcitrant ICM in organic-rich matrices like wastewater effluent.

Keywords: X-ray contrast media; Iodinated; Titanium dioxide; Advanced oxidation; Reductive dehalogenation

Adsorptive denitrogenation of model fuels with porous metal-organic frameworks (MOFs): Effect of acidity and basicity of MOFs by Imteaz Ahmed; Zubair Hasan; Nazmul Abedin Khan; Sung Hwa Jhung (pp. 123-129).

Display Omitted► Acid sites of MOFs have a beneficial effect on adsorptive denitrogenation of fuels. ► Acid–base interaction may control efficiency of adsorption of N/S-compounds. ► MOFs can be easily modified with grafting to impart acidity or basicity.To understand the effect of the acidity or basicity of porous metal-organic frameworks (MOFs) on the adsorptive removal of nitrogen-containing compounds (NCCs), an MOF (MIL-100(Cr)) was modified to impart acidity or basicity onto the MOFs. The modification was done by grafting ethylenediamine and aminomethanesulfonic acid onto coordinatively unsaturated sites of the MOF, MIL-100(Cr). The adsorptive removal of a basic quinoline or benzothiophene can be improved noticeably, especially at low concentrations, with the introduction of an acidic site; however, a basic MOF causes a severe decrease in the adsorptive performance for a basic adsorbate such as quinoline. The effect of the interaction of the base–base on adsorption was more severe or detrimental for a hard base quinoline than for a soft base benzothiophene. Functionalized MOFs show a slightly decreased adsorption for a neutral adsorbate such as indole probably because of the decreased porosity of the MOFs compared with the virgin MOF without functionalization. Moreover, a functionalized MOF (withSO₃H group) can be used several times after simple washing with acetone. From the present research, it may be concluded that acid–base interactions between NCCs and MOFs will lead to favorable adsorptive removal of NCCs. However, for the adsorptive removal of a neutral adsorbate such as indole, another adsorption mechanism (such as π-complexation or hydrogen-bonding) is needed for high uptake and efficient removal.

Keywords: Acid–base interaction; Adsorptive denitrogenation; Functionalization; Metal organic framework (MOF)

Removal of arsenite by coupled electrocatalytic oxidation at polymer–ruthenium oxide nanocomposite and polymer-assisted liquid phase retention by Juan Francisco Rivera; Christophe Bucher; Eric Saint-Aman; Bernabé L. Rivas; María del Carmen Aguirre; Julio Sanchez; Isabelle Pignot-Paintrand; Jean-Claude Moutet (pp. 130-136).

Display Omitted► A polymer–ruthenium oxide nanocomposite was electrosynthesized and fully characterized. ► Carbon electrodes were modified with films of this nanocomposite. ► The modified electrodes exhibited high catalytic activity toward As(III) oxidation. ► As(III) oxidation combined with ultrafiltration allowed efficient arsenic removal.Nanocomposite materials synthesized by incorporation of ruthenium oxide nanoparticles into a poly(pyrrole-alkylammonium) matrix have been characterized by transmission electron microscopy and by electrochemistry. Ruthenium oxide-based nanocomposites films coated onto carbon appeared efficient electrocatalysts for the oxidation of arsenic(III) into arsenic(V) species at a remarkable low potential, i.e. in the 0.3–0.5V vs. Ag/AgCl range. Bulk electrocatalytic oxidation of arsenite solutions could be performed in the presence of a water-soluble poly(quaternary ammonium) salts acting as the supporting electrolyte and also as an As(V) complexing agent, which allowed to combine electrocatalytic oxidation of As(III) with the liquid phase polymer-assisted retention (LPR) technique to efficiently remove arsenic from polluted solutions.

Keywords: Ruthenium oxide composites; Electrocatalytic oxidation; Arsenic; Ultrafiltration

Citric acid loading for MoS₂-based catalysts supported on SBA-15. New catalytic materials with high hydrogenolysis ability in hydrodesulfurization by Diego Valencia; Tatiana Klimova (pp. 137-145).

Display Omitted► NiMo catalysts supported on SBA-15 were prepared with different citric acid (CA) loading. ► CA modifies the catalysts’ properties when its amount is increased. ► High hydrogenolysis ability of these catalysts in hydrodesulfurization of dibenzothiophene was observed due to CA amount.The aim of this work is to get a deeper insight into the effect of citric acid (CA) loading in NiMo sulfided catalysts supported on SBA-15 on their behavior in hydrodesulfurization (HDS). Catalysts were prepared by simultaneous impregnation of Ni, Mo and CA species, varying the CA amount in aqueous solution. After the impregnation, NiMoCA catalysts were dried at 100°C under air atmosphere without calcination. Catalysts were characterized by several techniques (TGA, N₂ physisorption, small-angle and powder XRD, FT-IR, UV–vis DRS, TPR, elemental analysis and HRTEM) and tested in HDS of dibenzothiophene (DBT). N₂ physisorption, small-angle XRD and FT-IR showed the adsorption of CA on the SBA-15 surface. XRD characterization demonstrated that Ni and Mo oxide species were well dispersed in all catalysts. UV–vis DRS revealed better dispersion of Mo species with the increase of CA loading. TPR experiments exhibited an important effect of CA under reducing atmosphere; it can be reduced to leave carbon on the catalytic materials. This observation was confirmed by carbon analysis which showed an increase in the amount of carbon in the same direction than the CA loading. HDS of DBT showed differences in activity and selectivity of the catalysts prepared with different CA loading. We observed outstanding promotion of direct desulfurization (DDS) route with increasing the CA amount. The preference of DBT to react over NiMoCA catalysts toward DDS route was an unexpected behavior.

Keywords: Hydrodesulfurization; SBA-15; Citric acid; Dibenzothiophene; Carbon

Surface reconstruction enhancing activity of Pt/C for formic acid electrooxidation by ultrasonic mixing with Pb/C and electrochemical activation process by Xiao Zhao; Jianbing Zhu; Liang Liang; Chenyang Li; Changpeng Liu; Wei Xing (pp. 146-152).

Display Omitted► Pt/C+Pb/C catalyst was obtained by ultrasonic mixing of Pt/C and Pb/C. ► Surface reconstruction of Pt/C+Pb/C catalyst occurred in acidic electrolyte. ► Pt/C+Pb/C catalyst exhibited enhanced activity for formic acid electrooxidation. ► The direct pathway is preferably occurred on Pt/C+Pb/C catalyst. ► Third-body effect and electronic effect are responsible for this enhancement.The control for surface of catalysts is intrinsically required to improve catalytic efficiency. In current work, we demonstrate that the surface of Pt/C catalyst can be effectively reconstructed by ultrasonic mixing with Pb/C in an acidic environment and electorchemical activation process. As a result, the surface-reconstructed Pt/C catalyst exhibits a significant enhancement of activity of a ca. 10-fold improvement in mass activity and a ca. 38-fold improvement in specific activity as compared with a pure Pt/C catalyst for formic acid electroxidation (FAEO). The evidences show that some of Pb species are transferred from Pb/C to surface of Pt/C catalyst probably through the dissolution–adsorption pathway during ultrasonic mixing and electorchemical activation processes. The presence of Pb on surface of Pt not only isolates the continuous Pt sites through the third-body effect but also modifies electronic band structure of platinum via electronic effect, which leads to that the direct pathway is preferably occurred and the CO formation is effectively inhibited. These results provide useful information for further understanding the promotion mechanism of Pb ad-atom during FAEO and rationally controlling the catalytic surface to improve catalytic efficiency.

Keywords: Surface reconstruction; Formic acid fuel cell; Platinum; Lead; Ultrasonic mixing; Electronic effect; Third-body effect

Sulfate radicals induced degradation of tetrabromobisphenol A with nanoscaled magnetic CuFe₂O₄ as a heterogeneous catalyst of peroxymonosulfate by Yaobin Ding; Lihua Zhu; Nan Wang; Heqing Tang (pp. 153-162).

Display Omitted► CuFe₂O₄ particles could efficiently catalyze the activation of peroxymonosulfate. ► Radical quenching studies confirmed sulfate radicals as the major reactive radicals. ► Both Cu(II) and Fe(III) made contributions to the catalytic activity of CuFe₂O₄. ► The new CuFe₂O₄/peroxymonosulfate system degraded fully tetrabromobisphenol A. ► The degradation pathways of tetrabromobisphenol A in the new system were proposed.CuFe₂O₄ magnetic nanoparticles (MNPs) were prepared by sol–gel combustion method with copper and iron nitrates as metal precursors and citrate acid as a complex agent. The obtained CuFe₂O₄ MNPs were characterized by scanning electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy, Fourier transform Raman spectroscopy and X-ray photoelectron spectroscopy. It was found that CuFe₂O₄ MNPs could effectively catalyze peroxymonosulfate (PMS) to generate sulfate radicals (SO₄⁻) to degrade tetrabromobisphenol A (TBBPA). The added TBBPA (10mgL⁻¹) was almost completely removed (with a removal of 99%) in 30min by using 0.1gL⁻¹ CuFe₂O₄ MNPs and 0.2mmolL⁻¹ PMS. With higher addition of PMS (1.5mmolL⁻¹), the degradation yielded a TOC removal of 56% and a TBBPA debromination ratio of 67%. The effect of catalyst calcination temperature, catalyst load, PMS concentration and reaction temperature was investigated on the catalytic activity of CuFe₂O₄ MNPs. The highly catalytic activity of CuFe₂O₄ MNPs possibly involved the activation of PMS by both Cu(II) and Fe(III) in CuFe₂O₄ MNPs. Based on intermediate detections, the degradation pathway of TBBPA in the CuFe₂O₄ MNPs/PMS system was proposed.

Keywords: Tetrabromobisphenol A; Oxidative degradation; Peroxymonosulfate; CuFe; ₂; O; ₄; Sol–gel combustion method

The graphene-supported palladium and palladium–yttrium nanoparticles for the oxygen reduction and ethanol oxidation reactions: Experimental measurement and computational validation by Min Ho Seo; Sung Mook Choi; Joon Kyo Seo; Seung Hyo Noh; Won Bae Kim; Byungchan Han (pp. 163-171).

Display Omitted► Uniformly dispersed Pd and Pd₃Y nanoparticles on GNS at loadings up to 60wt.%. ► Electrocatalytic activities of the Pd and bimetallic Pd–Y alloy for ORR and EOR. ► Experimental and theoretical validation of electronic structure on Pd in the Pd and Pd₃Y. ► Fundamental relationship between d-band center position and activity for ORR and EOR.Oxygen reduction and ethanol oxidation reaction (ORR and EOR) have been studied on graphene nanosheet-supported (GNS) pure Pd and Pd₃Y nanoscale-alloy (Pd/GNS and Pd₃Y/GNS) electrocatalysts. The electrochemical studies were carried out for ORR both in acidic and alkaline solutions employing a rotating disk electrode (RDE), and performed for EOR in alkaline media with cyclic voltammetry method. The structure and composition of the Pd and Pd₃Y nanoparticles were verified using TEM, XRD and XPS. We combine the experimental measurements with ab initio density functional theory (DFT) calculations to identify the d-band center position of Pd atom in the pure Pd and Pd₃Y alloys as a function of site on near the surface. Both approaches clearly show that alloying the Pd with Y significantly modifies the electronic structures of Pd atoms. Core-level of Pd 3d_5/2 shifts to a negative value, which increases the d-band center of Pd atom and enhances the bond strength of PdO, which implies good catalysts for EOR but ORR. Our results indicate that the electronic structure of the Y-modified bimetallic Pd alloy is a good descriptor for the catalytic activity.

Keywords: Electrocatalyst; Graphene; Palladium; Oxygen reduction reaction; Ethanol oxidation reaction; Alkaline fuel cell; Density functional theory

Catalytic performance of MnO_x–NiO composite oxide in lean methane combustion at low temperature by Yagang Zhang; Zhangfeng Qin; Guofu Wang; Huaqing Zhu; Mei Dong; Shuna Li; Zhiwei Wu; Zhikai Li; Zhonghua Wu; Jing Zhang; Tiandou Hu; Weibin Fan; Jianguo Wang (pp. 172-181).

A prominent synergism between NiO and MnO_x in MnO_x–NiO composite oxide was observed. Compared with the single NiO and MnO_x oxides, the MnO_x–NiO composite oxide with proper composition exhibits much higher catalytic performance in the lean methane oxidation.Display Omitted► MnO_x–NiO composite oxide is prepared by doping of MnO_x in NiO. ► MnO_x–NiO as a non-noble metal catalyst exhibits outstanding activity in lean methane combustion. ► A prominent synergism between NiO and MnO_x in the MnO_x–NiO was observed. ► MnO_x(0.13)–NiO is provided with abundant dispersed Mn⁴⁺ species and certain nickel vacancies. ► Oxygen mobility and redox capacity of MnO_x–NiO are enhanced by the doping of MnO_x in NiO.A series of MnO_x–NiO composite oxide catalysts were prepared by co-precipitation method and used in the catalytic combustion of lean methane at low temperature. Compared with the corresponding single NiO and MnO_x oxides, the MnO_x–NiO composite oxide with proper composition exhibits much higher catalytic performance in the lean methane oxidation. XRD and HRTEM results demonstrate that MnO_x–NiO is in the form of a Ni–Mn–O solid solution. XAFS and XPS results indicate that the content of manganese in MnO_x–NiO has a significant influence on the oxidation state of manganese and the crystal defect of nickel oxide. MnO_x–NiO catalyst with an atomic Mn/(Mn+Ni) ratio of 0.13 is provided with abundant highly dispersed manganese species of higher valence (Mn⁴⁺) and higher coordination number as well as certain nickel vacancies, due to the strong interaction between Ni and Mn species. H₂-TPR and O₂-TPD results show that the MnO_x–NiO composite oxide exhibits better reducibility and oxygen mobility than NiO. All these characterizations suggest a prominent synergism between NiO and MnO_x in the MnO_x–NiO composite oxide, which contributes to its high performance in the lean methane combustion.

Keywords: Nickel oxide; Manganese oxide; MnO; _x; –NiO composite oxide; Lean methane; Catalytic combustion

Novel visible-light-driven AgX/graphite-like C₃N₄ (X=Br, I) hybrid materials with synergistic photocatalytic activity by Hui Xu; Jia Yan; Yuanguo Xu; Yanhua Song; Huaming Li; Jiexiang Xia; Chuanjing Huang; Huilin Wan (pp. 182-193).

Display Omitted► AgX/g-C₃N₄ hybrid materials displayed the much higher photocatalytic activity. ► The increasing activity of materials was attributed to the synergic effect. ► The heterostructures were superior for the transfer of electrons and holes.Novel visible-light-driven AgX/g-C₃N₄ (X=Br, I) hybrid materials were synthesized by the facile water bath method. The AgX/g-C₃N₄ hybrid materials were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL), Fourier transform infrared spectra (FTIR), Raman and the special surface area. The XRD, EDS, TEM, FTIR, Raman and XPS analyses indicated that AgX nanoparticles were evenly distributed on the surface of g-C₃N₄ and the heterostructures were formed. The photocatalytic activity of the AgX/g-C₃N₄ hybrid materials was evaluated using methyl orange as a target organic pollutant. The as-prepared AgX/g-C₃N₄ hybrid materials displayed much higher photocatalytic activity than the pure g-C₃N₄ and AgX nanoparticles. After the introduction of AgX nanoparticles, the photocurrent of the AgBr/g-C₃N₄ and AgI/g-C₃N₄ hybrid materials was found to increase by 21 and 8 times than that of the pure g-C₃N₄, respectively. The increased photocatalytic activity of the AgX/g-C₃N₄ hybrid materials was attributed to the synergic effect between g-C₃N₄ and AgX, which included the optical property, the better dispersion and the small size. A photocatalytic mechanism and the kinetics of AgX/g-C₃N₄ hybrid materials were also proposed.

Keywords: g-C; ₃; N; ₄; Silver halide; Graphite-like structure; Hybrid material; Photocatalytic

Highly efficient bacteria inactivation and phenol degradation by visible light irradiated iodine doped TiO₂ by G. Veréb; L. Manczinger; A. Oszkó; A. Sienkiewicz; L. Forró; K. Mogyorósi; A. Dombi; K. Hernádi (pp. 194-201).

Display Omitted► TiO₂-I decomposes phenol with much higher efficiency than P25 under VIS irradiation. ► TiO₂-I kills E. coli more effectively than P25 under visible light. ► Iodine doped TiO₂ can generate OH radical under VIS irradiation. ► Dissolved iodine was derived from the irradiated titanium dioxide.In this study visible light active iodine doped titanium dioxide samples prepared by sol–gel method were investigated. Photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence spectroscopy (XFS), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and by Brunauer–Emmett–Teller (BET) surface area technique.Different iodine/titanium ratios ( n_I/ n_Ti=0.0–2.6) were applied during the synthesis and the optimum value was determined by phenol degradation under UV and VIS irradiations. The photocatalytic efficiency towards phenol degradation and the inactivation of Escherichia coli ( E. coli) contaminated water under visible light illumination (conventional 24W energy-saving compact fluorescence lamps) of the most active iodine-doped TiO₂ ( n_I/ n_Ti=0.5; 79.5m²/g; 98wt% anatase) was compared with well known reference photocatalysts, that are Aeroxide P25 and Aldrich anatase (>85nm primary crystallite size). Results showed that our iodine doped TiO₂ was far more efficient at inactivating the E. coli and decomposing the phenol than Aeroxide P25. Electron spin resonance (ESR) measurements confirmed the formation of highly reactive OH radicals by the iodine doped titania under VIS irradiation. In contrast, singlet oxygen and superoxide radical ions were not detected. The performed experiments also proved that dissolved iodine was produced in very low concentrations (about 0.01–0.025mg/L) from the irradiated titanium dioxide. The dissolved iodine could have some contribution to the phenol oxidation and the disinfection effects. This study demonstrated this property of iodine-doped titanias for the first time.

Keywords: Photocatalysis; Iodine doped; Visible light; Disinfection; Escherichia coli; Titanium dioxide; Spin trapping

Study on the effect of metal types in (Me)-Al-MCM-41 on the mesoporous structure and catalytic behavior during the vapor-catalyzed co-pyrolysis of pubescens and LDPE by Wen-Wu Liu; Chang-Wei Hu; Yu Yang; Dong-Mei Tong; Liang-Fang Zhu; Rui-Nan Zhang; Bo-Han Zhao (pp. 202-213).

Display Omitted► Me introduced into Al-MCM-41 caused some changes in structure and catalytic behavior. ► Interactions between intermediate species from co-pyrolysis were confirmed again. ► Catalysts except Ni-Pd-Al-MCM-41 exerted an effect of alkanisation on intermediates. ► Ni–Pd created a strong synergistic effect on producing hydrogen during co-pyrolysis.The catalysts (Me)-Al-MCM-41 (Me=Ni, Pd and their combination) were synthesized hydrothermally, characterized with XRD, BET, NH₃-TPD, SEM, TEM, XPS, H₂-TPR, chemisorption of hydrogen, and tested by experiments of co-pyrolysis of pubescens and LDPE under vapor-catalyzed condition. Characterization results suggested that the synthesis of Al-MCM-41 was successful, but the introduction of Me into Al-MCM-41 caused some changes in structure of catalyst to a certain degree, resulting in significant changes in their properties and catalytic behavior. The results obtained from vapor-catalyzed co-pyrolysis over these catalysts showed that there were some interactions between the intermediate species from the co-pyrolysis, as the relative content of aromatics in oil was high, whereas that of phenol in corresponding aqua was low, and vice versa. The type of metal in catalysts was of more importance than the metal siting. Moreover, all catalysts except Ni-Pd-Al-MCM-41 exerted strong effect of alkanisation on the primary intermediate species from the pyrolysis of LDPE, which demonstrated that the pore architecture of parent Al-MCM-41 and (Me)-Al-MCM-41 containing single Me strongly favored the reactions in relation to alkanisation; on the contrary, Ni-Pd-Al-MCM-41 exerted a strong effect of dehydrogenation on those primary intermediate species. More importantly, the synergistic effect on producing hydrogen, based on the 61.8vol.% of H₂ in gaseous mixture, indicated that the combination of Ni and Pd in (Me)-Al-MCM-41 might bring about a novel performance during the vapor-catalyzed co-pyrolysis of biomass and plastics. It was predicted that Ni-Pd-Al-MCM-41 might play its special application in development of hydrogen energy, exploitation and utilization of biomass as well as municipal solid waste (MSW) such as waste plastics, etc. The major schemes of reactions involved in the vapor-catalyzed co-pyrolysis had been proposed.

Keywords: Co-pyrolysis; Alkanisation; Aromatization; (Me)-Al-MCM-41; Synergistic effect

The impact of aging environment on the evolution of Al₂O₃ supported Pt nanoparticles and their NO oxidation activity by Santhosh Kumar Matam; Evgenii V. Kondratenko; Myriam H. Aguirre; Paul Hug; Daniel Rentsch; Alexander Winkler; Anke Weidenkaff; Davide Ferri (pp. 214-224).

Display Omitted► The evolution of Pt nanoparticles supported on alumina is sensitive to the aging environment. ► NO oxidation is structure sensitive. ► Cuboctahedral Pt nanoparticles show better activity than spherical and truncated cubic structures.The impact of the aging environment on the size, morphology and distribution of Pt nanoparticles supported on Al₂O₃ and on their NO oxidation activity is studied. To this end, the fresh catalyst Pt/Al₂O₃ (Pt/Al/F) is aged under different aging environments mimicking the aging process of a real diesel oxidation catalyst (DOC) including phosphorus (P) poison as a chemical contaminant. These catalysts are characterized by N₂-physisorption, CO chemisorption, XRD, solid state²⁷Al MAS NMR, HAADF-STEM, HR-TEM, EDX analyses and CO-DRIFTS. The characterization results reveal that the thermal aging in air at 800°C leads to a heterogeneous size and spatial distribution of Pt nanoparticles in the catalyst (Pt/Al/O). The morphology is mainly limited to truncated cubic structures that are dominated with (100) crystal facets. Differently, aging in a lean diesel exhaust environment (Pt/Al/R) restricts the extensive Pt particle growth, size distribution to narrow and morphology predominantly to cuboctahedral that contains both (111) and (100) planes, though the former tends to dominate the surface. P seems to control both the growth of Pt particles and the morphology that is mainly limited to spherical irrespective of the aging environment (P/Pt/Al/O or P/Pt/Al/R). The normalized (per surface Pt atoms) forward rate constant of NO oxidation and the corresponding activation energy are determined for the differently treated catalysts and compared them with those reported in previous relevant studies. From these results it is evident that the reaction is indeed structure sensitive. The catalyst treated in lean diesel exhaust environment (Pt/Al/R) presents the best activity followed by the fresh Pt/Al/F and thermally Pt/Al/O aged catalysts. The difference in the NO oxidation activity of the catalysts is attributed to the morphology of Pt nanoparticles. These results correlate very well with the real DOC monolith that was aged on a heavy duty small truck for 250h under different driving profiles.

Keywords: Diesel oxidation catalyst; Aging environment; Thermal aging; Chemical aging; Phosphorus poison; Pt nanoparticles; Particle size; Particle morphology; NO oxidation; Structure sensitivity

Promoted activity of sulphated Ce/Zr mixed oxides for chlorinated VOC oxidative abatement by B. de Rivas; C. Sampedro; M. García-Real; R. López-Fonseca; J.I. Gutiérrez-Ortiz (pp. 225-235).

Display Omitted► Sulphation of Ce/Zr oxides promoted the decomposition of chlorinated VOCs. ► T₅₀ and T₉₀ were considerably lowered by 80°C ( T₅₀) and 120°C ( T₉₀). ► Sulphated Ce_0.5Zr_0.5O₂ and Ce_0.15Zr_0.85O₂ showed the highest activity. ► Overall acidity and concentration of sites with a moderate strength were increased. ► No marked impact on Ce⁴⁺/Ce³⁺ reduction step was found.The catalytic oxidative decomposition of 1,2-dichoroethane was examined over a series of Ce/Zr mixed oxides (CeO₂, Ce_0.8Zr_0.2O₂, Ce_0.5Zr_0.5O₂, Ce_0.15Zr_0.85O₂ and ZrO₂) treated with a 1M aqueous solution of H₂SO₄ or HNO₃. After calcination at 550°C, the doped samples were characterised by dynamic thermogravimetry, X-ray diffraction, N₂-physisorption, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of ammonia, adsorption of pyridine followed by Raman spectroscopy and temperature-programmed reduction with hydrogen. A noticeable promotion of activity was found for all sulphated oxides, which was associated with an increase of the total acidity and more particularly with a higher concentration of sites with a moderate/strong acid strength. Also the generation of new Brönsted acid sites was found. Interestingly, sulphation did not lead to a significant loss of surface area (except for sulphated ceria) and redox properties linked to the Ce⁴⁺/Ce³⁺ cycle were not apparently affected. Sulphated Ce_0.5Zr_0.5O₂ and Ce_0.15Zr_0.85O₂ samples showed the highest catalytic activity. Hence, the temperatures for DCE removal (in terms of T₅₀ and T₉₀) were considerably lowered by 80°C ( T₅₀) and 120°C ( T₉₀). This behaviour evidenced that sulphation was an effective tool to improve the performance of Ce/Zr mixed oxides for chlorinated VOC abatement. In contrast, the activity of the samples modified with nitric acid hardly showed any variation.

Keywords: Chlorinated VOCs; Catalytic oxidation; 1,2-Dichloroethane; Ce/Zr mixed oxides; Sulphation; Acidity

Catalytic decomposition of polystyrene. The role of acid and basic active centers by M. Marczewski; E. Kamińska; H. Marczewska; M. Godek; G. Rokicki; J. Sokołowski (pp. 236-246).

Display Omitted► Catalytic decomposition of polystyrene over acidic and basic catalysts was studied. ► PS reaction consist of: thermal degradation and consecutive catalytic cracking. ► Solid acids transform linear styrene dimers to aromatics and cyclic styrene dimers. ► Solid acids transform cyclic styrene dimers to indane, indene and naphthalene. ► Acidic and basic catalysts transform higher styrene oligomers to styrene.The influence of the acid and basic properties of a catalyst on the selectivity of polystyrene transformation was studied. The properties of silicaalumina SiO₂–Al₂O₃(45%) dotted with NaOH from 1 to 20wt% and γ-Al₂O₃ containing 1 to 8wt% NaOH or H₂SO₄ were examined using the test reactions of cumene (acid) and diacetone alcohol (base) transformation. These catalysts were used in polystyrene transformations. It was found that polystyrene decomposition involves thermal and catalytic transformation. In the first case, two main reaction pathways are involved: gradual depolymerization to the monomer (styrene) and pyrolysis leading to the formation of different volatile oligomers (dimers, trimers, tetramers.). The latter species react solely over the catalyst active centers. Linear dimers of styrene activated by Brønsted acid sites undergo decomposition to styrene and ethylbenzene as well as to toluene and α-methylstyrene. Consecutive transformation of the products leads to a simultaneous hydrogen (H⁺ and H⁻) production and coke formation. The latter ions are active in hydrogen transfer reactions which causes hydrogenation of styrene to ethylbenzene. In the presence of base catalysts selective styrene formation takes place and transformation leading to coke are slower hence ethylbenzene formation is suppressed. In the presence of acid catalysts linear dimers can also isomerize to cyclic derivatives which after dealkylation give benzene and methylindane. The later product in isomerization and hydrogen transfer reactions forms methylindene and naphthalene. The higher styrene oligomers reactions are catalyzed by both acid and basic sites leading mainly the monomer, i.e. styrene formation.

Keywords: Polystyrene recycling; Polystyrene decomposition; Solid acids; Solid bases; Test reactions; Alumina; Alkalized alumina; Sulfated alumina; Silicaalumina; Alkalized silicaalumina

Oxidative removal of phenol from water catalyzed by nickel hydroxide by Muhammad Saeed; Mohammad Ilyas (pp. 247-254).

Kinetic expression for oxidative degradation of phenol in aqueous medium catalyzed by nickel hydroxide.Display Omitted► Preparation of nickel hydroxide catalyst. ► Characterization of the catalyst by various techniques. ► Catalytic efficiency of nickel hydroxide for oxidative degradation of phenol. ► Effect of various parameters on catalytic degradation of phenol. ► Heterogeneous kinetics of oxidative degradation of phenol.This work explores the preparation and characterization of nickel hydroxide catalyst and investigation of its catalytic activities for oxidative degradation of phenol in aqueous medium using batch reactor. The catalyst was prepared by reaction of sodium hypochlorite, sodium hydroxide and nickel sulfate hexahydrate in distilled water. The prepared catalyst was characterized by surface area, particle size, FTIR, XRD, SEM, and determination of oxygen content measurements. The prepared nickel hydroxide was used as catalyst for oxidative degradation of phenol in aqueous medium by taking 15mL of 0.71M phenol solution. The catalytic performance of nickel hydroxide was explored in terms of effect of time, temperature, partial pressure of oxygen, initial concentration of phenol, catalyst loading and effect of stirring speed on degradation of phenol. The catalyst was separated from the reaction mixture by filtration. Langmuir–Hinshelwood type of mechanism was followed in the reaction where adsorption of phenol and oxygen at the surface of catalyst was taking place according to competitive Langmuir and Temkin adsorption isotherm, respectively.

Keywords: Phenol; Nickel hydroxide; Kinetic studies; Adsorption isotherms

Synthesis of g-C₃N₄/SmVO₄ composite photocatalyst with improved visible light photocatalytic activities in RhB degradation by Tingting Li; Leihong Zhao; Yiming He; Jun Cai; Mengfei Luo; Jianjun Lin (pp. 255-263).

Display Omitted► A series of g-C₃N₄/SmVO₄ composite is prepared by milling and heating method. ► The optimal g-C₃N₄ content and heating temperature is determined. ► The g-C₃N₄/SmVO₄ composite degraded RhB 2× faster than g-C₃N₄ under visible light. ► The high activity can be attributed to the synergy of SmVO₄ and g-C₃N₄.This paper reported novel graphitic carbon nitride (g-C₃N₄) and SmVO₄ composite photocatalysts which were prepared through a simple mixing–calcination method. Multiple techniques, such as Brunauer–Emmett–Teller (BET) method, thermogravimetric/differential thermal analysis (TG–DTA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy were applied to investigate the physical and photophysical properties of the catalysts. The XRD and FT-IR results indicate that the prepared sample is a two-phase composite of SmVO₄ and g-C₃N₄. The TG–DTA result suggests that the real g-C₃N₄ concentration in the composite is lower than the theoretical value due to the catalysis of SmVO₄. The DRS result shows that the addition of SmVO₄ to g-C₃N₄ slightly changes the optical properties. The photocatalytic activity of the novel composite was investigated using rhodamine B (RhB) as a target pollutant. Results show that the g-C₃N₄/SmVO₄ photocatalysts exhibit a significantly enhanced photocatalytic activity in degrading RhB. The optimal SmVO₄ concentration and calcination temperature were also determined. Based on the band position, the synergetic effect of SmVO₄ and g-C₃N₄ is the source of the enhanced photocatalytic activity, as proven by PL spectroscopy and transient photocurrent response.

Keywords: Photocatalytic activity; g-C; ₃; N; ₄; SmVO; ₄; Photoluminescence

New insight about orange II elimination by characterization of spent activated carbon/Fe Fenton-like catalysts by Filipa Duarte; Francisco J. Maldonado-Hódar; Luis M. Madeira (pp. 264-272).

Display Omitted► Orange II molecules are adsorbed on the AC surface without degradation. ► Clear differences between spent AC adsorbent and Fe/AC catalysts were found by TPD. ► The increase of the H₂O₂ load in catalytic runs did not favor the OII elimination. ► Species formed at high H₂O₂ load are more oxidized, having difficult to be adsorbed.This work is focused on the characterization of heterogeneous Fe-based catalysts supported on activated carbons (ACs) that are used in elimination of the azo-dye orange II (OII) from an aqueous solution. The main goal is to clarify the process of OII removal by analyzing textural and chemical surface properties of the fresh and spent activated carbon and Fenton-like catalysts upon using as adsorbents and/or catalysts. Textural changes were analyzed based on the corresponding N₂ adsorption isotherms and the nature of the adsorbed products by TG-DTG and TPD. It was found that OII was adsorbed filling the microporosity without degradation, although interactions between OII molecules and the AC surface groups have been detected. The total organic carbon (TOC) removal is complete in adsorption experiments. In the catalytic experiments using different H₂O₂ concentrations (in the range 6–24mM) the TOC elimination was never complete and got worse when increasing the H₂O₂ load. The OII molecules were partially oxidized and the adsorption of these products also leads to some blockage of the porosity; higher blockage and higher TOC removals was noticed after experiments carried out with low H₂O₂ concentration. The different TOC removal was related to the interactions of the oxidation products with the carbon surface. When using the highest concentration of the oxidant (24mM), the highest biodegradability and the lowest toxicity of the treated solution were reached, corroborating again the different nature of the oxidation by-products formed in each case.

Keywords: Heterogeneous Fenton; Activated carbon; Spent catalyst; TPD; TG

Platinum oxide formation and reduction during NO oxidation on a diesel oxidation catalyst—Macrokinetic simulation by K. Hauff; H. Dubbe; U. Tuttlies; G. Eigenberger; U. Nieken (pp. 273-281).

► Macro kinetic model taking into account PtO formation (Pt+0.5O₂↔PtO) and reduction (PtO+NO↔Pt+0.5NO₂). ► NO oxidation rate depends on platinum oxide fraction. ► Model is validated by several experiments with either constant temperature or linear temperature ramp.The activity of a diesel oxidation catalyst (Pt- γ-Al₂O₃) is strongly influenced by the reaction conditions due to platinum oxidation, which drastically decreases the NO oxidation activity. Reactivation is possible with normal exhaust gas since platinum oxide can be reduced by NO in an atmosphere with high oxygen content at temperatures below 200°C. A macrokinetic model is presented which takes into account the deactivation due to platinum oxidation. A standard model is extended by an additional balance of the platinum fraction and by reactions for platinum oxide formation (Pt+0.5 O₂⇌PtO) and reduction (PtO+NO→Pt+0.5 NO₂). It is assumed (1) that platinum oxide is not inactive but has a lower activity, (2) that small amounts of NO₂ have no impact on the oxidation in the presence of high oxygen concentrations and (3) that formation of PtO₂ is negligible and that PtO is the main platinum oxide species formed. The NO oxidation rate is calculated for highly active sites (platinum) and sites with lower activity (platinum oxide). The actual reaction rate is calculated as a function of the platinum oxide fraction. With this extended macrokinetic model a good prediction of NO conversion is achieved. For model calibration and validation, isothermal experiments with either constant temperature or linear temperature ramps are employed. The model can be transferred to catalysts with lower platinum loading or aged catalysts, if only the NO oxidation on platinum and platinum oxide is reparameterised.

Keywords: NO oxidation; Platinum oxidation; Deactivation; Macrokinetic model; Inverse hysteresis

Effects of silica coating on photocatalytic reactions of anatase titanium dioxide studied by quantitative detection of reactive oxygen species by Junichi Oguma; Yusuke Kakuma; Seigo Murayama; Yoshio Nosaka (pp. 282-286).

Display Omitted► Active oxygens were quantitatively detected for UV-irradiated anatase TiO₂ suspension. ► H₂O₂ was produced from both oxidation of water and reduction of O₂. ► By silica coating, the photocatalytic formation of H₂O₂ was significantly suppressed. ► The weather resistance by silica coating may be explained by the suppression of H₂O₂.The effects of silica coating on the photocatalytic properties of anatase titanium dioxide (TiO₂) were studied by quantitative detection of reactive oxygen species under UV-irradiation, because the surface modification with silica has been practically used to suppress the photocatalytic activity in organic supports. For reactive oxygen species such as superoxide radicals (O₂⁻), H₂O₂, and OH radicals, the detection methods using MCLA chemiluminescence, lucigenin chemiluminescence, and coumarin fluorescence were employed respectively. By comparing silica-coated TiO₂ with uncoated TiO₂ powders, the amount of H₂O₂ detected under UV irradiation was significantly decreased by silica coating. Thus the silica modification suppressed the release of H₂O₂, which may be the nature of the effect of silica coating for suppressing photocatalytic activity against organic supports.

Keywords: Titanium dioxide; Silica coating; Photocatalytic reaction; Reactive oxygen species

Au/ZrO₂: an efficient and reusable catalyst for the oxidative esterification of renewable furfural by M. Signoretto; F. Menegazzo; L. Contessotto; F. Pinna; M. Manzoli; F. Boccuzzi (pp. 287-293).

Display Omitted► The oxidative esterification of furfural was investigated on Au/ZrO₂ catalyst. ► Au/ZrO₂ is active and selective. ► Au/ZrO₂ is recyclable by thermal oxidation at a proper temperature. ► The calcination at a proper temperature allows to obtain the ideal catalyst.Highly dispersed gold based catalysts supported on zirconia were employed in the oxidative esterification of furfural by an efficient and sustainable process. Au/ZrO₂ catalysts were calcined at different temperatures in order to modulate gold nanosize. A detailed characterization was carried out for the sake of ascertaining if micro structural changes occurred, and the size issue was discussed. Catalysts stability and recycling were investigated too, and the opportunity of reusability by thermal oxidation at a proper temperature was successfully proved.

Keywords: Gold catalyst; Furfural; Oxidation; Biomass esterification; Zirconia

Facile synthesis of hierarchically meso/nanoporous s- and c-codoped TiO₂ and its high photocatalytic efficiency in H₂ generation by Hongwei Bai; Keith Shan Yao Kwan; Zhaoyang Liu; Xiaoxiao Song; Siew Siang Lee; Darren Delai Sun (pp. 294-300).

Display Omitted► Hierarchically meso/nanoporous TiO₂ was codoped with S and C via a facile method. ► Hierarchically meso/nanoporous TiO₂ exhibited high photocatalytic H₂ generation activity because of many merits. ► Hierarchical meso/nanoporous structure facilitating fast mass transport. ► Co-doping of S and C, and well crystallized TiO₂ after calcination. ► Large specific surface and enhanced light absorption capability.Here, hierarchically meso/nanoporous TiO₂ was successfully fabricated by a facile and efficient hydrolysis and calcination method using Ti(OC₄H₉)₄ and K₂S₂O₈ as precursors. The hydrosol was firstly prepared by drop-wise adding ethanol dissolved Ti(OC₄H₉)₄ solution into acetone dissolved K₂S₂O₈ solution under a vigorous stirring and heating condition. After being sufficiently hydrolyzed, the hydrosol was calcined to promote the crystallization of TiO₂ and successfully dope S and C on TiO₂. The calcination temperature significantly affects the doping of S and C on TiO₂, crystallization of TiO₂, formation of hierarchically meso/nanoporous structure of TiO₂ and its light absorption capability. The S- and C-codoped TiO₂ exhibits high photocatalytic H₂ generation efficiency in a water/methanol sacrificial reagent system under the irradiation of UV light. The high photocatalytic efficiency is dependent on the comprehensively competing effects of the codoping of S and C, crystallization, specific surface area and light absorption capability. The S- and C-codoped TiO₂ calcined at 600°C demonstrates the highest photocatalytic H₂ generation efficiency, which is ascribed to the balanced synergy of the abovementioned factors.

Keywords: Hierarchically meso/nanoporous structure; H; ₂; generation; Photocatalysis; S- and C-codoped TiO; ₂

Catalytic degradation of tobacco-specific nitrosamines by ferric zeolite by Wei Gang Lin; Yu Zhou; Fang Na Gu; Shi Lu Zhou; Jian Hua Zhu (pp. 301-308).

Display Omitted► Ferric zeolite can catalyze the degradation of nitrosamines in tobacco smoke. ► Up to 26% of TSNAs is selectively removed in smoke for the first time. ► The state of ferric species and their catalytic function in zeolite are determined. ► Laboratorial TPSR test can screen the cig-catalyst candidates.New strategy of using ferric zeolite ZSM-5 and Y to adsorb and catalytically degrade tobacco-specific nitrosamines (TSNA) is reported in this article. These zeolites were modified by both aqueous ion-exchange with FeSO₄ solution and wet-impregnation of Fe(NO₃)₃, and characterized by XRD, UV–vis DRS, H₂-TPR and temperature-programmed surface reaction (TPSR). Apart from laboratory tests, these samples were put into tobacco rods of cigarette to assess their real performance of reducing TSNA content in smoke, and the determination of TSNA was carried out by LC–MS/MS technique with the assistance of internal-standards. The ion-exchanged zeolites are more active than their impregnated analogs, and the ferric Y zeolite could selectively reduce 26% of total TSNA in mainstream smoke of Burley type tobacco. Catalytic breaking of the chemical bond in NNO group of nitrosamines by zeolite is the key step of decomposition of these carcinogens.

Keywords: Ferric zeolite; Tobacco-specific nitrosamines (TSNA); Ion-exchange and impregnation; Catalytic degradation; Cigarette-catalyst (cig-cat)

Inactivation by solar photo-Fenton in pet bottles of wild enteric bacteria of natural well water: Absence of re-growth after one week of subsequent storage by J. Ndounla; D. Spuhler; S. Kenfack; J. Wéthé; C. Pulgarin (pp. 309-317).

Display Omitted► Inactivation of wild enteric bacteria by near to neutral photo-Fenton. ► Evaluation of the photo-Fenton disinfection efficiency in natural well water. ► Description of the photo-Fenton disinfection mechanism at near to neutral pH. ► No bacterial regrowth observed after one week subsequent storage.Iron photo-assisted inactivation of wild enteric bacteria (total coliforms/ E. coli and Salmonella spp.) was carried out in water from the Sahelian wells having different pH (W1: 4.9 and W2: 6.3) and a natural iron content of 0.07mg/L. We evaluate the efficiency of the disinfection on different systems containing both or only one Fenton reagent (H₂O₂/Fe²⁺): (i) H₂O₂/Fe²⁺/ hv, (ii) Fe²⁺/ hv, (iii) H₂O₂/ hv, and (iv) only light irradiation ( hv) at lab and field scale. Generally, 0.6mg/L of Fe²⁺ and/or 8.5mg/L of H₂O₂ were used in the Fenton reagent. The systems H₂O₂/Fe²⁺/ hv and H₂O₂/ hv led to total inactivation of Salmonella and E. coli. The natural iron content (0.07mg/L) was enough to drive an efficient photo-Fenton process leading to total bacterial inactivation. Our results show that: (i) the iron salt present in Sahelian water is enough to perform a photo-Fenton disinfection of drinking water when adding H₂O₂, (ii) addition of external iron salts at near neutral pH has no additional effect on the bacterial photo-Fenton inactivation process. After one week of storage, no enteric bacteria re-growth was observed in treated waters. Mechanistic suggestions are presented to explain the observed results.

Keywords: Photo-Fenton; Inactivation; Enteric bacteria; Drinking water

Fast purification of air from diethyl sulfide with nanosized TiO₂ aerosol by Alexander V. Vorontsov; Alexey S. Besov; Valentin N. Parmon (pp. 318-324).

Display Omitted► Diethyl sulfide (DES) is removed from gas phase by adsorption on TiO₂ aerosol only at low air humidity. ► DES is efficiently removed by photocatalytic oxidation at moderate air humidity. ► The minimum surface area of TiO₂ to remove one DES molecule is about 2nm². ► Air purification from DES by aerosol is obtained within 10min.TiO₂ aerosol generated by a sonic method has been applied for fast purification of air from diethyl sulfide (DES) vapors inside a closed chamber. Two types of experiments modeling the possible real situations were conducted – (1) aerosol spraying without irradiation followed by UV irradiation after aerosol deposition and (2) aerosol spraying under UV irradiation. Adsorption of DES on TiO₂ particles was complete and fastest at the lowest air relative humidity (RH) while photocatalytic oxidation was fastest at RH 37%. The minimal TiO₂ aerosol surface area needed to remove from air one DES molecule is 2.3nm² at the adsorption and 1.5nm² at the photocatalytic oxidation. The quantum efficiency of the DES consumption increases from 4.7 to 20% when the initial DES concentration increases from 100 to 1000ppm. The overall quantum efficiency of the DES deep oxidation reached 41 and 58% for the initial concentration 100 and 1000ppm, respectively. The results demonstrate unusually high activity of TiO₂ aerosol for the adsorption-photocatalytic air purification from DES.

Keywords: Atmospheric chemistry; CWA; Photocatalysis; Titanium dioxide; Titania; Decontamination; Anti-terrorism; Water concentration; Gas phase; Static; Nanoparticles; Sulfide; Troposphere

Superoxide radical driving the activation of persulfate by magnetite nanoparticles: Implications for the degradation of PCBs by Guo-Dong Fang; Dionysios D. Dionysiou; Souhail R. Al-Abed; Dong-Mei Zhou (pp. 325-332).

Display Omitted► MNPs exhibited the excellent catalytic reactivity toward persulfate for the degradation of PCB28. ► The generation of reactive oxygen species by MNPs was observed. ► Superoxide radical drives the catalysis of persulfate by persulfate. ► Reaction pH and sorbed Fe(II) on MNPs surface affects the generation of radical species and the degradation of PCB28.Magnetite nanoparticles (MNPs) are ubiquitous components of the subsurface environment, and increasing attention has been paid to MNPs due to their highly reductive and heterogeneous catalysis reactivity for the degradation of organic contaminants. However, most previous research studies neglected the generation of reactive oxygen species (ROS) by MNPs, which plays an important role in the transformation of contaminants. In this paper, we investigated the activation of persulfate (PS) by MNPs for the degradation of 2,4,4′-CB (PCB28), a selected model compound, and the underlying mechanism was elucidated. The results indicated that the PS can be activated by MNPs efficiently for the degradation of PCB28 at neutral pH. Electron paramagnetic resonance (EPR) technique was used to detect and identify the radical species in these processes. The mechanism of the activation of PS by MNPs was that superoxide radical anion (O₂⁻) generated by MNPs could activate the PS to produce more sulfate radicals (SO₄⁻), which favored the degradation of PCB28. The conclusion was further confirmed by quenching studies with the addition of superoxide dismutase (SOD). The effects of Fe(II) and pH on the degradation of PCB28 by PS/MNPs as well as the generation of ROS by MNPs were also studied. Both sorbed Fe(II) on MNPs surface and increased pH led to production of more O₂⁻, which activated the PS to give more SO₄⁻ to degrade PCB28. In addition, increasing the oxygen concentration in the reaction solution favored the generation of O₂⁻ as well as the degradation of PCB28. The findings of this study provide new insights into the mechanism of heterogeneous catalysis based on MNPs and the reactivity of MNPs toward environmental contaminants.

Keywords: MNPs; Superoxide radical; Activation; PS; Sulfate radical; PCB28

Bi₂O₃ quantum dots decorated anatase TiO₂ nanocrystals with exposed {001} facets on graphene sheets for enhanced visible-light photocatalytic performance by Jungang Hou; Chao Yang; Zheng Wang; Shuqiang Jiao; Hongmin Zhu (pp. 333-341).

Bi₂O₃ quantum dots decorated anatase TiO2 with exposed {001} high energy facets had been firstly prepared on graphene sheets by a simple and feasible strategy using the hydrofluoric acid and methanol joint assisted solvothermal reactions and their visible-light photocatalytic performance were systematically investigated.Display Omitted► Bi₂O₃ quantum dots decorated TiO₂ nanosheets were prepared on graphene sheets by a simple strategy. ► Enhanced photocatalytic activities of Bi₂O₃/TiO₂ were obtained for RhB degradation. ► Significantly enhanced photocatalytic activities of Bi₂O₃/TiO₂ on graphene were achieved. ► Tentative photocatalytic performance for various systems were proposed.Due to its great importance in fundamental research and practical applications, tailored synthesis of anatase TiO₂ dominated with highly energetic {001} facets has attracted extensive interest. Here, Bi₂O₃ quantum dots decorated anatase TiO₂ with exposed {001} high energy facets had been firstly prepared on graphene sheets by a simple and feasible strategy using the hydrofluoric acid. During the synthesis process, TiO₂ nanosheets were homogeneously decorated with surface enrichment of Bi₂O₃ quantum dots and graphene was uniformly covered with a large number of Bi₂O₃/TiO₂ composites. The morphologies, structural properties and photocatalytic performance of the resultant Bi₂O₃/TiO₂/graphene composites were investigated and were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, UV–vis diffuse reflectance spectrum and photoluminescence spectra. A certain amount of Bi₂O₃ quantum dots coating on TiO₂ nanosheets exhibited significant improvement in photocatalytic degradation of the azo dye Rhodamine B under visible-light irradiation than TiO₂ nanosheets, which could be attributed to the extending spectral response from UV to visible area, the enhanced photosensitizing effect of the surface enriched Bi₂O₃ quantum dots and the strong interaction between Bi₂O₃ and TiO₂. Furthermore, the Bi₂O₃/TiO₂/graphene hybrids could be used as a stable photocatalyst for the highest photocatalytic activity for Rhodamine B degradation, which is ascribed predominantly to the efficient reduction of electron–hole pair recombination in the heterostructures. This investigation likely opens up new possibilities for the development of highly efficient TiO₂ based photocatalysts that utilize visible-light as an energy source.

Keywords: Bi; ₂; O; ₃; quantum dots; TiO; ₂; nanosheets; Graphene; Visible light photocatalyst; Degradation

Sulfonic acid functionalized mesoporous SBA-15 catalysts for biodiesel production by Donghua Zuo; James Lane; Dan Culy; Michael Schultz; Allison Pullar; Michael Waxman (pp. 342-350).

Display Omitted► Organosulfonic acid functionalized SBA-15 catalysts for biodiesel production. ► Catalyst activity largely dependent on acid strength rather than number of acid sites. ► Perfluoro-sulfonic acid group is readily leached in the reaction medium. ► Reaction parameters have been optimized over the arene-SO₃H SBA-15 catalyst. ► Arene-SO₃H SBA-15 catalyst shows promising results for low quality feedstocks.Sulfonic acid functionalized mesoporous SBA-15 catalysts have been studied in the microwave-assisted transesterification of soybean oil with 1-butanol in order to produce low freezing point biodiesel. Small-angle powder XRD and nitrogen adsorption analysis revealed the formation of mesoporous materials with high surface area and uniform porosity. Catalytic activity was found to be largely dependent on the acid strength rather than the number of acid sites. Propyl-SO₃H and arene-SO₃H functionalized SBA-15 catalysts showed high activity and stability in transesterification reactions whereas perfluoro-SO₃H functionalized SBA-15 catalyst exhibited a complete loss of activity after recycling due to complete leaching of perfluoro-SO₃H groups in the reaction medium. The results over arene-SO₃H functionalized catalysts showed that the optimal loading of arene-SO₃H groups is approximately 15% (molar percent of functional group to total silicon) and the optimal oil to alcohol molar ratio is 1:6. Increases in catalyst to oil weight ratio and reaction temperature significantly enhance the reaction rates. Simultaneous transesterification and esterification of soybean oil with up to 20 wt% oleic acid over arene-SO₃H functionalized catalyst indicated that this catalyst could be a promising candidate for processing low quality feedstocks containing high fraction of free fatty acids. Further modification of Ar-SO₃H SBA-15 catalyst with hydrophobic groups did not significantly improve its catalytic performance.

Keywords: Mesoporous SBA-15 catalysts; Organosulfonic acid functionalization; Biodiesel; Transesterification; Esterification

A preliminary research on V/N–TiO₂ self-cleaning thin film by sol–gel method under the guidance of first principle method density functional theory (DFT) by MaoMeng Wu; Hao Yu; Meng Xu (pp. 351-366).

Display Omitted► The doping up-limitation of vanadium in TiO₂ was derived by the binding energy change. ► The greatest RMS (13.9nm) self-cleaning film possesses impurity band between the VB and CB was successfully prepared. ► The photocatalytic and wetting properties were studied upon UV and Vis irradiation. ► V/N–TiO₂ films show superior self-cleaning activity. ► The mechanisms have been elaborated for this photoreaction.A series of Ti1−_xV_xO2−_yN_y self-cleaning thin films, which can be activated driven by visible-light (VL), have been successfully immobilized on quartz glasses by sol–gel and dip-coating methods. The First Principle Method acts as guidance and reference for getting the critical (up-limitation) vanadium doping quantity in accordance with the binding energy change. Results of the band structure calculations and the doped density of states (DOS) reveal that localized impurity bands obviously existed in the band gap of TiO₂ when the V doping quantity was ca.6at%, this film possesses the optimal visible light absorption by facilitating the transition of electron from the localized impurity band to the conduction band. Anatase crystalline phase was detected by the characterization of X-ray diffraction (XRD). TG/DTA, AFM, XPS, UV–vis, MB degradation and surface contact angle (CA) tests were also conducted for the film structural and optical properties. It is found that the mean square root (RMS) roughness of Ti_0.94V_0.06O_1.94N_0.06 (13.9nm) is ca.33 times than the others, the V, N mono-doping can increase visible light absorption (403nm), while V/N co-doping can greatly enhance absorption in lower frequency visible region (496nm). The MB degradation rate of Ti_0.94V_0.06O_1.94N_0.06 is 7.7×10⁻³molL⁻¹min⁻¹, while the rates of N-doped and pure TiO₂ film were (1.94×10⁻³molL⁻¹min⁻¹) (0.8×10⁻³molL⁻¹min⁻¹), respectively. The CA on this kind of film can approach to ca. 5°. All these results indicated that the Ti1−_xV_xO_1.94N_0.06 does well in photocatalysis and photohydrophilicity within the region of visible light. It would be a promising practical self-cleaning function and application.

Keywords: DFT; V/N-doping; Impurity band; AFM; Photocatalysis; Photohydrophilicity; Self-cleaning

Preparation of graphitic mesoporous carbon for the simultaneous detection of hydroquinone and catechol by Xiaoli Yuan; Dingsheng Yuan; Fulong Zeng; Wujun Zou; Fotini Tzorbatzoglou; Panagiotis Tsiakaras; Yi Wang (pp. 367-374).

Display Omitted► Simultaneous identification of HQ and CC by using CV and DPV has been achieved. ► Highly graphitic mesoporous carbon (GMC) modified electrode with high specific surface area was prepared. ► A simple solid-phase technique under a relatively low pyrolysis temperature is used.A graphitic mesoporous carbon (GMC) had been successfully synthesized using Ni–Fe layered double hydroxide (LDH) as both template and catalyst under a relatively low pyrolysis temperature. The techniques of X-ray diffraction, transmission electron microscopy, Raman spectrum and N₂ adsorption/desorption were used to characterize the physico-chemical properties of the as-prepared GMC. Meanwhile, the voltammetric behaviors of hydroquinone (HQ) and catechol (CC) were studied at the GMC modified glassy carbon electrode (GMC/GCE). The separation of the oxidation and reduction peak (Δ E_p) for HQ and CC were decreased from 369 to 42mV and from 365 to 52mV, respectively, and the anodic peak currents for the oxidation of both HQ and CC were also remarkably increased at the GMC/GCE. Furthermore, at the GMC/GCE, the two components could be entirely separated with a large oxidation peak potential separation between HQ and CC. Under the optimized condition, the peak currents of HQ and CC increased linearly with increasing HQ and CC contents. The detection limit for HQ and CC was 3.7×10⁻⁷ and 3.1×10⁻⁷molL⁻¹, respectively.

Keywords: Graphitic mesoporous carbon; Layered double hydroxides; Simultaneous detection of hydroquinone and catechol

Enhancement of oxygen reduction reaction on PtAu nanoparticles via CO induced surface Pt enrichment by Hee-Young Park; Tae-Yeol Jeon; Jong Hyun Jang; Sung Jong Yoo; Kwang-Hyun Choi; Namgee Jung; Yung-Hoon Chung; Minje Ahn; Yong-Hun Cho; Kug-Seung Lee; Yung-Eun Sung (pp. 375-381).

Display Omitted► Surface enrichment of Pt in PtAu nanoparticles was achieved by CO induced segregation. ► The Pt enrichment was characterized by XPS and electrochemical analysis. ► A higher Pt area and weaker OH adsorption enhanced oxygen reduction reaction.To investigate the enhancement of the oxygen reduction reaction (ORR) activity on a carbon-supported PtAu alloy nanoparticle catalyst, the catalyst was subject to heat treatment at 423K under a CO or Ar atmosphere. The surface composition was analyzed by XPS and the composition was shown to increase from 66±2% (PtAu-AP) to 74±2% (PtAu-CO) after heat treatment under a CO atmosphere, which was confirmed by electrochemical techniques, while the bulk composition was invariant at 55%. For the oxygen reduction reaction (ORR), the mass activity of PtAu-CO increased by 75.6% (33.2 A/g_Pt) when compared to that of PtAu-AP (18.9 A/g_Pt). Since the increase in EAS was only 15.8%, it was concluded that the specific activity was enhanced by 52.6% due to surface Pt segregation after heat treatment under a CO atmosphere. The enhanced specific activity was attributed to the reduced OH adsorption energy which was characterized by measuring the potential of total zero charge. The weaker OH adsorption was resulted from the higher Pt/Au ratio at the surface layers.

Keywords: Polymer electrolyte membrane fuel cell; Electrocatalysis; PtAu; Surface segregation; Pt enrichment; Oxygen reduction reaction

Stabilization mechanism and crystallographic sites of Ru in Fe-promoted barium hexaaluminate under high-temperature condition for N₂O decomposition by Yan Zhang; Xiaodong Wang; Yanyan Zhu; Tao Zhang (pp. 382-393).

The stabilization mechanism and crystallographic sites of Ru in β_I-Al₂O₃ type Fe-promoted barium hexaaluminates and the effect on the performance for N₂O decomposition was proposed for the first time.Display Omitted► The evaporation of Ru species under high-temperature condition was suppressed. ► The addition of Fe ions promoted the formation of intermediate BaRuO₃ phase. ► More Ru species were stabilized due to the formation of BaRuO₃ phase. ► Framework Ru ions only occupied the distorted Al(5) sites in the mirror plane. ► Ru ions in the Al(5) sites were highly active for N₂O decomposition.The stabilization of volatile ruthenium from catalysts at high temperatures is an important issue in both academia and industry. In this paper, Ru-substituted barium hexaalumimates (BaRu_0.2FeAl_10.8O₁₉) with β_I-Al₂O₃ structure were prepared using the carbonates route and investigated for high-concentration of N₂O decomposition. It was for the first time found that the evaporation of ruthenium species under high-temperature condition (1100–1200°C) could be effectively suppressed by the addition of Fe in the hexaaluminate precursor. Fe promoted the formation of intermediate stable BaRuO₃ phase, which greatly alleviated the evaporation of Ru species during calcination, and thus allowed more Ru species enter into the final sintering-resistant hexaaluminate lattice after high-temperature treatment. Ru ions in the hexaaluminate structure only occupied the distorted tetrahedral interstitial Al(5) sites in the loosely packed mirror plane, which originated from Ru species in oxidic entities dispersed on the Ba-modified γ-Al₂O₃ and the intermediate BaRuO₃ in the precursors. Ru ions in the Al(5) sites were key factors responsible for the high activity of N₂O decomposition.

Keywords: Stabilization of ruthenium; Hexaaluminate; Iron; Rietveld refinement; N; ₂; O decomposition

Efficient anchorage of highly dispersed and ultrafine palladium nanoparticles on the water-soluble phosphonate functionalized multiwall carbon nanotubes by Min Zheng; Pan Li; Gengtao Fu; Yu Chen; Yiming Zhou; Yawen Tang; Tianhong Lu (pp. 394-402).

The water-soluble phosphonate functionalized MWCNTs are deposited with Pd nanoparticles (Pd-NPs) as electrocatalyst for formic acid oxidation.Display Omitted► A facile noncovalent approach is proposed to graft phosphonate groups onto the MWCNTs surface. ► The phosphonate functionalized MWCNTs are further deposited with Pd nanoparticles. ► Pd nanoparticles are highly dispersed and effectively anchored on the MWCNTs surface. ► Pd/NYPA-MWCNTs catalyst shows excellent electrocatalytic activity for formic acid oxidation.A facile noncovalent approach is proposed to graft phosphonate groups onto the surface of the multiwall carbon nanotubes (MWCNTs) by π–π stacking interaction between naphthalen-1-ylmethylphosphonic acid (NYPA) and MWCNTs. Noncovalently attachment of phosphonate groups on the MWCNTs surface is confirmed by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and zeta potential analysis. The water-soluble phosphonate functionalized MWCNTs are further deposited with Pd nanoparticles (Pd-NPs) as electrocatalyst for formic acid oxidation. The morphology and structure of Pd-MWCNTs nanocomposites are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and XPS measurements. It is observed that Pd-NPs are highly dispersed and effectively anchored on the side walls of the phosphonate functionalized MWCNTs. The Pd-MWCNTs nanocomposites exhibit better electrocatalytic activity and long-term stability for formic acid electrooxidation than the un-phosphonated counterpart.

Keywords: Carbon nanotubes; Noncovalent functionalization; Phosphonic acid groups; Solubilization; Formic acid electrooxidation

A promising new photocatalyst CdSnO₃·3H₂O for air purification under ambient condition by Yibin Chen; Danzhen Li; Jing Chen; Jinxiu Wang; Sugang Meng; Jiangjun Xian; Xianzhi Fu; Yu Shao (pp. 403-408).

A promising new photocatalyst CdSnO₃·3H₂O with remarkable photocatalytic performance have been synthesized by means of a facile homogenous precipitation method. The results demonstrated that, the conversion ratio and mineralization ratio in the photocatalytic degradation of benzene were up to 45% and 60%. This catalyst also presented notably high photocatalytic activities toward cyclohexane and acetone under UV light irradiation. The conversion of cyclohexane on CdSnO₃·3H₂O was relatively reduced to 15%, but the mineralization of cyclohexane on CdSnO₃·3H₂O was high up to 75%. As to acetone, the conversion over CdSnO₃·3H₂O was about 25%, and the mineralization was about 58%. Hence, the high photocatalytic performance of the new photocatalyst CdSnO₃·3H₂O was very important for practical environmental remedial application.Display Omitted► CdSnO₃·3H₂O cubes were synthesized by a facile homogenous precipitation. ► Attention to its remarkable photocatalytic activity for benzene. ► The catalyst also performs high mineralization of cyclohexane and acetone. ► It was possible for the environmental remedy application of the behind.A new binary metal hydrate photocatalyst CdSnO₃·3H₂O was synthesized from Cd(CH₃COO)₂ and SnCl₄·5H₂O via a facile homogenous precipitation method. The photocatalytic activities of samples were evaluated by the photocatalytic degradation of volatile organic compounds (VOCs) in O₂ gas stream under ultraviolet light irradiation. The results demonstrated that the typical CdSnO₃·3H₂O sample had an average particle size of about 16nm, a band gap of 4.4eV, and a specific surface area of 91.8m²g⁻¹. The comparison of CdSnO₃·3H₂O synthesized at different pH values showed that the photocatalytic activities of CdSnO₃·3H₂O synthesized at pH 7 and 8 were higher than that of the samples synthesized at pH 6 and 9. Contrast to commercial P25-TiO₂, the activity of this new photocatalyst was better. The conversion ratio of benzene was about 45% and 5%, corresponding to the mineralization ratio was about 60% and 25%, respectively. CdSnO₃·3H₂O also exhibited high photocatalytic activities towards cyclohexane and acetone. Then, the mechanism of the reaction on the new photocatalyst was discussed. Hence, the facile synthesis of this photocatalyst and its outstanding photocatalytic performance for VOCs are favorable to its potential application in the environmental remedy field.

Keywords: CdSnO; ₃; ·3H; ₂; O; Photocatalysis; Homogenous precipitation; Volatile organic compounds

Removal of 4-chlorophenol from wastewater: Preparation, characterization and photocatalytic activity of alkaline earth oxide doped TiO₂ by Gulin Selda Pozan; Ayca Kambur (pp. 409-415).

Display Omitted► The addition of alkaline earth oxide effects on the photocatalytic degradation reaction. ► The incipient wetness impregnation for photocatalysis. ► The entry of Mg²⁺ into the lattice of nano TiO₂ for enhancing of the activity.Alkaline earth oxide (MgO, CaO, SrO) doped TiO₂ catalysts prepared by impregnation method were successfully used in the photocatalytic degradation of 4-chlorophenol (4-CP) under UV irradiation. The materials were characterized by XRD, BET, FT-IR, DRS, PL, SEM and TEM techniques. Alkaline earth metal oxides resulted in an enhanced efficiency of the TiO₂ photocatalyst. The 10wt% MgO TiO₂ showed the highest percentage of 4-CP degradation (100%) and highest reaction rate (0.82mgL⁻¹min⁻¹) in 1h. It was also found that the catalytic activity of 10MgO-TiO₂ was found to be higher than nano TiO₂ and P-25 photocatalyst. The photocatalytic performances are in the orders of: 10MgO/TiO₂>10CaO/TiO₂>10SrO/TiO₂. Alkaline earth oxide effectively decreases the band gap of the TiO₂. The enhanced adsorption of 4-CP over the catalyst surface and decrease in particle size as a result of Mg²⁺ loading is suggested to be the cause for higher activity of the catalyst. The profound effect of alkaline earth oxide doped TiO₂ for 4-chlorophenol is generally considered due to the entry of Mg²⁺ into the lattice of nano TiO₂ and high dispersion.

Keywords: Photocatalysis; 4-Chlorophenol; Alkaline earth oxide; TiO; ₂; UV irradiation; Characterization

Microreactors based on CuO–CeO₂/zeolite films synthesized onto brass microgrids for the oxidation of CO by Nicolás C. Pérez; Eduardo E. Miró; Juan M. Zamaro (pp. 416-425).

Display Omitted► Zeolite-based microreactors for CO oxidation. ► Synthesis of continuous and stable catalytic films on brass microgrids. ► Highly dispersed phases of Cu and Ce on the zeolite-coated microreactors. ► Superior performance in COTox and COProx reactions than powder catalysts.Microreactors based on Cu, Ce oxides dispersed onto zeolite films grown on brass microgrids were developed. Secondary synthesis conditions were regulated in order to obtain thin, homogeneous and adherent coatings of mordenite to which Cu and Ce were later incorporated. The systems were characterized by XRD, SEM-EPMA, H₂-TPR, LRS and XPS. The catalytic coatings were mechanically and chemically stable under reaction. Cu, Ce/zeolite microreactors were evaluated in the CO total oxidation (COTox) and in the preferential CO oxidation (COProx) showing a superior performance when compared with the same powder catalyst.

Keywords: Microreactor; Brass support; Mordenite; Wire mesh; Total CO oxidation; Preferential CO oxidation

Liquid–solid heterogeneous synthesis of highly dispersed and PdPt surface enriched PdPtCu/C as methanol tolerant oxygen reduction reaction catalysts by Wei Li; Xinsheng Zhao; Thomas Cochell; Arumugam Manthiram (pp. 426-436).

Display Omitted► We present a solid–liquid heterogeneous synthesis with switchable etching effects. ► Copper nanoparticles work as a reducing agent. ► Highly dispersed, PdPt surface enriched PdPtCu nanoparticles are deposited on carbon black. ► The prepared PdPtCu/C catalysts have composition-dependent catalytic activities.We present a liquid–solid heterogeneous synthesis with switchable etching effects to prepare highly dispersed, PdPt surface enriched PdPtCu alloy nanoparticles (NPs) supported on carbon black (PdPtCu/C) by using Cu NPs as a heterogeneous reducing agent. A mixture of the Pd and Pt precursors and nanosized particles of Cu are required to form the highly dispersed PdPtCu alloy NPs and scatter them on the carbon black. Oxidative etching of the surface Cu with the reaction solution triggered by switching the reaction solution atmosphere from N₂ to air results in an enrichment of the surface of PdPtCu by PdPt. The activity towards the oxygen reduction reaction and methanol tolerance is tuned by controlling the Pd/Pt ratio. The PdPtCu/C catalyst with a Pd/Pt molar ratio of 1:1 exhibits noble metal and Pt mass activities of, respectively, 2 and 3 times that of a commercial Pt/C at 0.85V vs. RHE with much superior methanol tolerance. It also shows better performance than Pt/C with comparable durability in a direct methanol fuel cell.

Keywords: Platinum palladium copper alloy; Heterogeneous synthesis; Surface enrichment; Oxygen reduction reaction; Methanol tolerance

Mechanisms of catalytic ozonation: An investigation into superoxide ion radical and hydrogen peroxide formation during catalytic ozonation on alumina and zeolites in water by Amir Ikhlaq; David R. Brown; Barbara Kasprzyk-Hordern (pp. 437-449).

Display Omitted► Different mechanisms govern aqueous ozone reactions on Al₂O₃ and on ZSM-5 zeolites. ► Ozone decomposition on Al₂O₃ leads to the formation of^oOH,^oO₂⁻ and H₂O₂. ► ZSM-5 do not facilitate ozone decomposition but act as ozone reservoirs. ► Adsorption of O₃ and organics on ZSM-5 is the determining step. ► Activity of ZSM-5 is independent of the nature of counter ions and their acidity.This study aims to investigate mechanisms of ozonation in the presence of ZSM-5 zeolites and γ-alumina in water. Four ZSM-5 zeolites with varying silica to alumina ratios and with both hydrogen and sodium counter ions were used in the study (Z1000H:SiO₂/Al₂O₃=1000, Z900Na:SiO₂/Al₂O₃=900, Z25H:SiO₂/Al₂O₃=25 and Z25Na:SiO₂/Al₂O₃=25). The formation of reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) and superoxide ion radical (^oO₂⁻) was investigated during ozonation in the presence of ZSM-5 zeolites and alumina using amplex red and 4-chloro-7-nitrobenzo-2-oxa-1,3-dizole (NBD-Cl) as probe molecules. To the authors’ knowledge, this is the first report utilising NBD-Cl and amplex red to study mechanisms of catalytic ozonation. The results showed that alumina promotes much higher formation of ROS in aqueous solutions when compared to ozonation alone and ozonation in the presence of ZSM-5 zeolites. The process was found to be pH dependent. Furthermore, alumina showed its highest activity at a pH close to its point of zero charge. The presence of tertiary butyl alcohol (TBA) and phosphates in the reaction solution did not have a significant effect on ROS production in the presence of ZSM-5 zeolites. However, in the case of alumina, the presence of phosphates significantly lowered ROS formation. This indicates the critical importance of surface hydroxyl groups of alumina in ozone decomposition and ROS formation. In contrast to H₂O₂ formation, TBA did not have a significant effect on^oO₂⁻ production in the case of alumina. This suggests that^oO₂⁻ plays a significant role in the formation of hydroxyl radicals. Furthermore, both zeolites and alumina were found to catalyse the removal of NBD-Cl from aqueous solution. Therefore, it is suggested that alumina operates through a radical mechanism leading to the production of ROS. On the other hand, zeolites serve as reservoirs of ozone and adsorbents of organic compounds, which interact via direct ozonation pathways. The activity of zeolites depends on the silica to alumina ratios of the zeolite and is independent of the nature of the zeolite counter ions.

Keywords: Catalytic ozonation; Mechanisms; Water; Superoxide ion radical; Hydrogen peroxide; ZSM-5 zeolites; Alumina

Transient studies of low-temperature dry reforming of methane over Ni-CaO/ZrO₂-La₂O₃ by B. Bachiller-Baeza; C. Mateos-Pedrero; M.A. Soria; A. Guerrero-Ruiz; U. Rodemerck; I. Rodríguez-Ramos (pp. 450-459).

Display Omitted► TAP investigation of the low temperature methane dry reforming reaction mechanism. ► Deactivating carbon deposits arise from methane cracking on nickel metal. ► Boudouard reaction does not occur in spite of the low temperature reaction. ► On Ni-ZrLa the reactants (CH₄ and CO₂) are activated on the metallic phase. ► On Ni-Ca-ZrLa the CO₂ is activated on the promoter enabling a bifunctional mechanism.The low temperature reforming of methane by carbon dioxide is studied over a calcium oxide promoted Ni catalyst supported on a tetragonal zirconia stabilized by lanthana, which presents an improved stability compared to the non-promoted catalyst. Steady-state catalytic activity measurements, diffuse reflectance infrared Fourier transform spectroscopic analysis and isotopic temporal analysis of products experiments reveal the occurrence of a bifunctional mechanism on the promoted catalyst: methane is activated on the Ni particles, carbon dioxide interacts with the calcium oxide to form carbonates which scavenge carbon from nickel at the Ni-O-Ca interphase, thus restoring Ni particles to the original state. This is assumed to hinder the formation of deactivating coke, which explains the improved catalytic stability of the promoted catalyst. The main route for the carbon deposit formation is found to be the methane cracking in spite of the low temperature reaction.

Keywords: Dry reforming methane; TAP reactor; DRIFTS; Ni catalyst; Calcium oxide promoter

Steam reforming of ethanol–phenol mixture on Ni/Al₂O₃: Effect of Ni loading and sulphur deactivation by Gabriella Garbarino; Alberto Lagazzo; Paola Riani; Guido Busca (pp. 460-472).

Display Omitted► Steam reforming of ethanol–phenol mixture is studied as model of biomass tar SR. ► Ethanol–phenol mixture is completely steam reformed over 39% Ni–alumina at 873K ► H₂ yields of 85% are obtained. ► Catalysts undergo conditioning upon working few hours at 873–1023K, without evident deactivation. ► Catalysts are deactivated if 210ppm S are present, but are regenerated in the S-free stream.The steam reforming of ethanol/phenol mixture (168g_TOT/Nm³, ethanol:phenol 2:1mol, GHSV=54,000h⁻¹) assumed as a model for tar mixtures, has been studied over Ni/Al₂O₃ catalysts. The effects of reaction temperature, Ni loading (from 0 to 39 (wt%/wt%)) and of the presence of sulphur has been investigated. If sufficiently charged with Nickel (e.g. 39% Ni with 107m²/g surface area), Ni/Al₂O₃ catalysts are effective in complete steam reforming of the tar model molecules at 873K, with CO₂ as the main C-containing reaction product and H₂ yield of 85%. The 5% Ni/Al₂O₃ can also produce the complete destruction of the molecules but at 973K. These catalysts do not deactivate significantly by coking in the timescale of some hours at 873–1023K. Starting with unreduced catalysts, a conditioning effect is evident on stream, supposed to be associated to the formation of “optimal” nickel metal particles. At lower temperatures the steam reforming activity towards phenol+ethanol mixture vanishes, with the appearance of reactions producing ethylene, acetaldehyde, and mono- and di-alkyl-phenols. Working at 973K, all Ni/Al₂O₃ catalysts are strongly deactivated by 210ppm of tetrahydrthiophene. However, catalytic activity is recovered by flowing with sulphur-free steam reforming feed, although the CO₂/CO product ratio, and consequently also the final hydrogen yield, is permanently altered. It is proposed that the last reaction step, i.e. the oxidation of adsorbed CO to CO₂ previous of its desorption, involves isolated cationic Ni centres that are irreversibly deactivated by sulphur or during the poisoning/regeneration cycle.

Keywords: Steam reforming of tars; Tar model molecules; Biomass tar; Ni/Al; ₂; O; ₃; catalysts; Sulphur poisoning of Ni/Al; ₂; O; ₃; Regeneration of Ni/Al; ₂; O; ₃; catalysts

Fe³⁺ doped TiO₂ nanotubes for combined adsorption–sonocatalytic degradation of real textile wastewater by Yean Ling Pang; Ahmad Zuhairi Abdullah (pp. 473-481).

Display Omitted► Fe-doped TiO₂ nanotubes catalyst with low band gap energy. ► Combined adsorption–sonocatalytic degradation of real textile wastewater. ► Pre-adsorption followed by sonocatalysis reaction produced better results. ► Elucidation of effects of important process variables. ► Fe-doped TiO₂ nanotubes showed great potential for wastewater treatment.Fe-doped titanium dioxide (TiO₂) nanotubes catalyst with large specific surface area and low band gap energy were successfully synthesized using sol–gel followed by hydrothermal method. The activity of the catalyst was assessed by examining the treatment of real textile wastewater through combined adsorption and heterogeneous sonocatalysis. Fe-doped TiO₂ nanotubes exhibited better removal efficiency in the case of pre-adsorption followed by sonocatalytic reaction as compared to the simultaneous adsorption and sonocatalysis system. Pre-adsorption on TiO₂ nanotubes was found to promote sonocatalytic degradation and the latter process could be considered as a surface-catalyzed reaction. Effect of the solution pH (3–11), catalyst dosage (2–10g/L) and hydrogen peroxide (H₂O₂) dosage (20–80mM) on the adsorption–sonocatalysis for the treatment of a real textile wastewater were investigated in detail. The best degradation efficiency can be achieved at solution pH of 3, 6g/L of Fe-doping, 40mM of H₂O₂, an ultrasonic frequency of 35kHz and an output power of 50W after 1h of adsorption followed by 3h of ultrasonic irradiation under continuous aeration. The color, COD and TOC removals were 79.9%, 59.4% and 49.8%, respectively. In short, adsorption followed by sonocatalytic degradation in the presence of Fe-doped TiO₂ nanotubes showed great potential for efficient treatment of real textile wastewater.

Keywords: Combined adsorption–sonocatalysis; Fe-doped TiO; ₂; nanotubes; Characteristics; Catalytic activity; Real textile wastewater

CdIn₂S₄ microsphere as an efficient visible-light-driven photocatalyst for bacterial inactivation: Synthesis, characterizations and photocatalytic inactivation mechanisms by Wanjun Wang; Tsz Wai Ng; Wing Kei Ho; Jianhui Huang; Shijing Liang; Taicheng An; Guiying Li; Jimmy C. Yu; Po Keung Wong (pp. 482-490).

Display Omitted► CdIn₂S₄ microsphere was synthesized by a facile ultrasonic spray pyrolysis method. ► Bacterial cells could be inactivated without direct contact with CdIn₂S₄. ► Large amount of H₂O₂ was produced with the involvement ofO₂⁻. ► A partition system was used to easily recycle and reuse the photocatalyst. ► Destruction of bacterial cells started from cell wall to intracellular components.New types of visible-light-driven photocatalysts with high activity for bacterial inactivation are needed to address the problems caused by outbreak of harmful microorganisms. In this study, cadmium indium sulfide (CdIn₂S₄) microsphere, which can be synthesized continuously by a facile ultrasonic spray pyrolysis method, was used as an efficient photocatalyst in inactivation of Escherichia coli K-12 under visible light (VL) irradiation for the first time. The as-prepared CdIn₂S₄ showed a micro-spherical morphology with diameter of 0.5–1.0μm. It had an energy band gap of 2.02eV and BET surface area of 34.8m²/g. It was found that bacterial cells could also be effectively inactivated inside a partition system without the direct contact with the photocatalyst, which was attributed to the diffusible photon-generated hydrogen peroxide (H₂O₂) rather than hydroxyl radicals (OH). Large amounts of H₂O₂ were produced from both conduction and valance bands with the involvement of superoxide (O₂⁻). The used CdIn₂S₄ could be easily recycled by the partition system without loss of activity. The destruction process of bacterial cells was from the cell wall to the intracellular components as confirmed by TEM study. In addition, theO₂⁻ andOH radicals were also detected in the CdIn₂S₄-VL system by ESR spin-trap with DMPO trapping technology.

Keywords: Photocatalytic inactivation; CdIn; ₂; S; ₄; Ultrasonic spray pyrolysis; Partition system; Hydrogen peroxide

Selective catalytic reduction of nitrogen oxides by ammonia over Co₃O₄ nanocrystals with different shapes by Bo Meng; Zongbin Zhao; Xuzhen Wang; Jingjing Liang; Jieshan Qiu (pp. 491-500).

.Display Omitted► Co₃O₄ nanocrystals (NCs) with controllable morphology have been synthesized. ► Co₃O₄ nanorods show higher NO_x conversion than nanoparticles in NH₃-SCR reaction. ► Co₃O₄ nanorods can absorb much more ammonia than nanoparticles during NH₃-SCR reaction. ► Co₃O₄ nanorods predominantly expose {110} planes that are rich in Co³⁺ sites. ► Co³⁺ cations facilitate NH₃ chemisorption and promote the catalytic activity.In this work, single-crystalline one-dimensional Co₃O₄ nanorods with well-defined crystal planes as catalysts in the selective catalytic reduction of NO by ammonia are investigated. The Co₃O₄ nanorods synthesized by ethylene glycol-mediated precipitation at 160°C predominantly expose {110} planes which are rich in Co³⁺ species, while the traditional Co₃O₄ nanoparticles expose the {001} and {111} planes which contain mainly Co²⁺ species. Compared with Co₃O₄ nanoparticles, Co₃O₄ nanorods show much higher NO_x conversion in NH₃-SCR reaction. TPD of various reactant gases, including NH₃, NO, NO/NH₃, NO/O₂, NO/NH₃/O₂, and transient experiment reveals Co₃O₄ nanorods adsorb a large amount of ammonia on their surface. Slight surface H₂ reduction significantly decreases the activity of Co₃O₄ nanocrystals, while O₂ re-oxidation partially recovers their catalytic activity, demonstrating the presence of Co³⁺ cations on the surface of Co₃O₄ nanocatalysts actually acts as the active sites in NH₃-SCR reaction. The present results indicate that novel catalyst with high activity can be designed by morphology control at nanoscale.

Keywords: Co; ₃; O; ₄; nanorods; NO; _x; reduction; Catalyst morphology; Catalytic activity

Modelling of the kinetics of the catalytic soot oxidation on Fe₂O₃ by Steffen Wagloehner; Sven Kureti (pp. 501-508).

Display Omitted► Fe₂O₃ model catalyst was used for the modelling of the kinetics of soot oxidation. ► A stationary 1-D and a transient 2-D model was developed and validated by simulations. ► The gradients of concentrations of gas species as well as solid soot are driven by the fluid dynamics. ► No hot spots and drastic concentration gradients appear due to convective mass transport.This paper addresses the kinetic modelling of the soot oxidation on a Fe₂O₃ model catalyst. The kinetics was evaluated by temperature programmed oxidation using a packed bed of tight contact mixtures of Fe₂O₃ and soot. The reaction rate was expressed by a global-kinetic approach taken from a previous paper. Some kinetic parameters were determined by a fit to experimental TPO data using a stationary 1-D CSTR model with coupled mass and heat balance. The fitting led to an apparent activation energy of 73kJ/mol, while the pre-exponential factor was calculated to be 1.6×10³m³/(mols). The kinetic model was validated by simulations and was then implemented into a transient 2-D model of the fixed-bed reactor. This model implied the conservation of mass, heat and momentum and was checked by temperature measurements conducted with an IR camera. Finally, the 2-D model was validated by simulating some TPO investigations. The simulations provide local concentrations of CO₂, O₂ and soot as well as local temperature and gas velocity. Particularly, these results suggest the absence of any drastic gradients of concentration and temperature in the packed bed due to the convection of the gas stream.

Keywords: Kinetic modelling; Soot oxidation; Fe; ₂; O; ₃; Model catalyst; Fluid dynamics

Catalytic oxidation of vinyl chloride emission over LaMnO₃ and LaB_0.2Mn_0.8O₃ (B=Co, Ni, Fe) catalysts by Chuanhui Zhang; Chao Wang; Wangcheng Zhan; Yanglong Guo; Yun Guo; Guanzhong Lu; Alexandre Baylet; Anne Giroir-Fendler (pp. 509-516).

Display Omitted► LaMnO₃ and LaB_0.2Mn_0.8O₃ (B=Co, Ni, Fe) were prepared by co-precipitation method. ► The B-site substitution increased the amounts of Mn⁴⁺ on the surface. ► No by-products were formed but only CO₂, H₂O and HCl. ► LaNi_0.2Mn_0.8O₃ presented the best catalytic activity for vinyl chloride abatement. ► Reducibility, surface adsorbed oxygen and O₂ mobility were the main parameters.The LaMnO₃ and LaB_0.2Mn_0.8O₃ (B=Co, Ni, Fe) perovskite-type oxides were prepared by the conventional co-precipitation method and studied as catalysts for the oxidation of vinyl chloride emission in the temperature range of 50–350°C. Their physicochemical properties were characterized by ICP-AES, N₂ adsorption, XRD, H₂-TPR, O₂-TPD and XPS. Catalytic performances were evaluated for the oxidation of 1000ppm of VC in air at a GHSV of 15,000h⁻¹. The substituted LaB_0.2Mn_0.8O₃ samples showed higher catalytic activity than pure LaMnO₃. Characterization results revealed that the catalytic activity of the perovskite oxides was greatly related to the low-temperature reducibility of the B site and the amount of adsorbed oxygen species and vacancies on the surface. The surface adsorbed oxygen species played a key role in the catalytic reaction and oxygen vacancies promoted the oxygen mobility. A reaction mechanism of vinyl chloride oxidation over LaMnO₃-based perovskite oxides was proposed.

Keywords: CVOCs; Vinyl chloride; Catalytic oxidation; Perovskite; Reducibility; Adsorbed oxygen

The effect gas composition during thermal aging on the dispersion and NO oxidation activity over Pt/Al₂O₃ catalysts by Xavier Auvray; Torben Pingel; Eva Olsson; Louise Olsson (pp. 517-527).

Display Omitted► Sintering is influenced by aging atmosphere. ► Larger Pt particles have higher activity for NO oxidation. ► Similar dispersion results in different activity, depending on aging atmosphere. ► SO₂ promotes platinum sintering, even at 250°C. ► Similar activities can be obtained after different treatments involving SO₂.The aging of a model 1wt.% Pt/Al₂O₃ catalyst was performed stepwise under different reactive atmosphere to study the evolution of metal dispersion and NO oxidation activity. After each aging step the dispersion was evaluated by CO chemisorptions and the activity of the catalyst for NO oxidation was measured using 500ppm NO and 8% O₂ diluted in Ar. After a degreening step at 500°C, aging was performed at 600, 700, 800 and 900°C. Five wash-coated cordierite monoliths were aged in Ar, 10% O₂, 1% H₂, 30ppm SO₂ and 30ppm SO₂+10% O₂, respectively. The general trend showed a linear decrease in dispersion when increasing the aging temperature for the lower aging temperatures and for the highest ones the dispersion levels off. When the platinum dispersion decreased the NO oxidation activity increased, due to that the reaction is structure sensitive. H₂ seemed to hinder sintering at low aging temperature. Interestingly, after aging in 10% oxygen at 600°C the NO oxidation activity was significantly higher compared to the Ar aged sample, although the dispersions were similar. Aging in oxygen at higher temperatures resulted in a decrease of dispersion and a slightly decreasing NO oxidation activity. Moreover lower dispersion limit was reached with oxygen aging. Aging in SO₂ provoked a severe dispersion drop at low aging temperature meanwhile the activity increased only moderately. However, activity kept increasing with further treatments at higher temperature. The combination of O₂ and SO₂ enabled to decrease rapidly the dispersion and to greatly enhance the catalytic NO oxidation activity after the first aging step at only 600°C. The best overall conversion was obtained for the catalyst treated with this mixture after aging at 800°C. A 22-h aging at 250°C in a mixture containing 500ppm NO, 10% O₂ and 30ppm SO₂ led to a significant decrease of Pt dispersion, which shows the ability of SO₂ to promote platinum sintering already 250°C. The low temperature sintering was confirmed with STEM measurements. Several larger particles were observed, but also many small particles remained. Thus the SO₂+O₂ induced low temperature sintering results in a large variation of particle sizes. This treatment resulted in an increase of the maximum NO conversion (after reduction of the sample) from 45% to 76%. The different aging experiments show that it is beneficial to add SO₂ during aging and the reason is the increased particle size, but also a clear chemical effect was observed.

Keywords: NO oxidation; NO; ₂; Pt/Al; ₂; O; ₃; DOC; Diesel oxidation catalyst; Aging; Deactivation; SO; ₂; Flow reactor; TEM

Gas-phase hydrodeoxygenation of guaiacol over iron-based catalysts. Effect of gases composition, iron load and supports (silica and activated carbon) by R. Olcese; M.M. Bettahar; B. Malaman; J. Ghanbaja; L. Tibavizco; D. Petitjean; A. Dufour (pp. 528-538).

Display Omitted► Hydrodeoxygenation (HDO) of guaiacol is a model reaction for lignin pyrolysis vapours HDO. ► The effect of gases (H₂, H₂O, CO, CO₂, CH₄) on HDO selectivity and catalyst composition was studied. ► Iron speciation was analysed by XRD and Mössbauer analysis. Carbon deposit was analysed by TPO as a function of gas composition. ► Fe/SiO₂ and Fe/Active carbon are selective catalysts for guaiacol HDO into benzene or phenol respectively.Fe/SiO₂ is shown to be a selective catalyst for guaiacol hydrodeoxygenation (HDO). Guaiacol is used as a model compound to study the conversion of lignin pyrolysis vapours into aromatics (benzene, phenols). The effect of each individual gas present in a pyrolysis gas (H₂, CO, CO₂, H₂O, CH₄) on the selectivity of a 10wt% Fe/SiO₂ catalyst is studied (673K, atmospheric pressure, 50mol% H₂, 1/WHSV=0.6g_cath/g_gua). The speciation of the iron phase (metallic (α-Fe), carbide (Fe₅C₂), oxide (Fe₃O₄), and super-paramagnetic) in spent catalysts is revealed by XRD and Mössbauer spectroscopy as a function of gases composition. At least 3 types of carbonaceous deposit were evidenced by TPO analysis. TEM observations showed that iron particles size is not markedly affected by the reaction and that carbon deposit mainly occurs in the vicinity of iron particles. When all the gases except methane (Guaiacol+H₂+CO+CO₂+H₂O) are simultaneously in the feed stream, the conditions are still sufficiently reducing to maintain the activity of the catalyst (66% of benzene and toluene carbon yield, 7.5g_cath/g_gua). The effects of support (silica or activated carbon-AC) and iron loading (5, 10, 15wt% Fe/SiO₂) were also studied. 10wt% Fe/AC has a higher selectivity in phenol and cresols production than Fe/SiO₂. Active sites and reaction mechanisms are discussed.

Keywords: Biorefinery; Lignin; Hydrotreatment; Chemicals; Aromatic

Three-dimensionally ordered macroporous Eu_0.6Sr_0.4FeO₃ supported cobalt oxides: Highly active nanocatalysts for the combustion of toluene by Kemeng Ji; Hongxing Dai; Jiguang Deng; Liyun Song; Baozu Gao; Yuan Wang; Xinwei Li (pp. 539-548).

yCoO_x/3DOM-ESFO ( ywt%=1, 3, 6, and 10) are prepared using the incipient wetness impregnation method. It is found that high oxygen adspecies concentrations, strong low-temperature reducibility, and good dispersion of cobalt oxide nanoparticles are responsible for the good catalytic performance of 3–6CoO_x/3DOM-ESFO.Display Omitted► yCoO_x/3DOM-ESFO catalysts are prepared using incipient wetness impregnation method. ► Cobalt oxide nanoparticles are highly dispersed on the surface of 3DOM-ESFO. ► 3–6CoO_x/3DOM-ESFO exhibits high O_ads concentration and good reducibility. ► 3–6CoO_x/3DOM-ESFO performs well in the combustion of toluene. ► Activity is governed by O_ads concentration, reducibility, and CoO_x dispersion.Three-dimensionally ordered macroporous (3DOM) Eu_0.6Sr_0.4FeO₃-supported cobalt oxide nanocatalysts ( yCoO_x/3DOM-ESFO; ywt%=1, 3, 6, and 10) were prepared using the incipient wetness impregnation method. Physicochemical properties of the composite materials were characterized by means of numerous techniques, and their catalytic performance was evaluated for the combustion of toluene. It is shown that all of the samples displayed a well-defined 3DOM architecture with a surface area of 22–31m²g⁻¹ and the loaded cobalt oxide nanoparticles with a diameter of 7–11nm were well dispersed on the surface of the 3DOM-ESFO support. Among the yCoO_x/3DOM-ESFO samples, the 3CoO_x/3DOM-ESFO and 6CoO_x/3DOM-ESFO ones possessed the highest oxygen adspecies concentration and the best reducibility at low temperature, and hence showing the best catalytic performance (the temperatures required for 50 and 90% toluene conversions were ca. 250 and 270°C at a space velocity of 20,000mLg^–1h^–1, respectively) for toluene combustion. The apparent activation energies (ca. 72kJmol⁻¹) of 3CoO_x/3DOM-ESFO and 6CoO_x/3DOM-ESFO were lower than that (81kJmol⁻¹) of 3DOM-ESFO. It is concluded that the enhanced catalytic performance of 3CoO_x/3DOM-ESFO and 6CoO_x/3DOM-ESFO for toluene combustion was mainly related to their higher oxygen adspecies concentrations, stronger reducibility at low temperature, and better dispersion of cobalt oxide nanoparticles.

Keywords: Three-dimensionally ordered macroporous perovskite-type oxide; Toluene combustion; Templating preparation method; Supported cobalt oxide catalyst

A high-efficiency microwave approach to synthesis of Bi-modified Pt nanoparticle catalysts for ethanol electro-oxidation in alkaline medium by Yiyin Huang; Jindi Cai; Yonglang Guo (pp. 549-555).

Display Omitted► The microwave way can accelerate the Bi³⁺ diffusion in the solution. ► Abundant OH_ad species were formed on the Bi-containing catalyst. ► Current of EOR on Bi–Pt/CNTs (0.1:1) was 2.6 times higher than that on Pt/CNTs. ► Anti-poisoning ability of this novel catalyst was greatly improved. ► The Bi deposition mechanism on Pt/CNT catalysts was studied in its synthesis.The Bi-modified Pt nanoparticle catalysts using multi-walled carbon nanotubes as supports are prepared through microwave treatment and long-term standing approaches. Bi can easily modify Pt catalyst because of the strong affinity between Bi and Pt. However, only limited amount of Bi and uneven Bi-modified Pt catalyst are obtained through the long-term standing approach. The microwave approach can complete the synthesis rapidly and get uniform Bi–Pt/CNT catalysts. X-ray photoelectron spectroscopy shows that Bi (III) and Pt (0) species are the main form in the Bi–Pt/CNT catalyst. Cyclic voltammetry indicates that the modification of Bi on Pt/CNTs leads to an enhanced activity up to 260% compared to Pt/CNTs for ethanol electro-oxidation. The current of Bi–Pt/CNTs (0.1:1) is 44.8 times higher than that of Pt/CNTs at −0.3V for 1800s. Linear current sweep results reveal that the electro-oxidation of residual intermediate species can be effectively promoted because the adsorption of OH_ad species is enhanced by the addition of Bi to Pt/CNTs, which is characterized by the higher open circuit potential.

Keywords: Alkaline fuel cell; Bi modification; Ethanol oxidation; Microwave synthesis; Pt catalyst

Influence of synthesis parameters on the performance of CeO₂–CuO and CeO₂–ZrO₂–CuO systems in the catalytic oxidation of CO in excess of hydrogen by Elisa Moretti; Maurizio Lenarda; Piero Riello; Loretta Storaro; Aldo Talon; Romana Frattini; Alvaro Reyes-Carmona; Antonio Jiménez-López; Enrique Rodríguez-Castellón (pp. 556-565).

TEM images of the sample FCZCu, a Ce–Zr–Cu oxide system with flower like morphology, prepared by slow co-precipitation in the absence of any structure directing agent.Display Omitted► Nanostructured Ce/Cu and Ce/Zr/Cu oxide systems were prepared. ► The effect of the different morphology and of the role of Zr doping on the active species was evaluated. ► The CO-PROX catalytic activity was correlated with the structural characteristics.Ce–Cu and Ce–Zr–Cu oxide systems with a flower-like morphology were prepared by slow co-precipitation in the absence of any structure directing agent. For the sake of comparison, Ce–Cu and Ce–Zr–Cu oxide samples were also prepared by a classic co-precipitation method. All the samples were calcined in air flow at 650°C. The materials were characterized by SEM and TEM microscopy, quantitative X-ray diffraction, N₂ physisorption, H₂-TPR, O₂-TPD and XPS. The catalytic activity of the prepared samples was evaluated in the preferential oxidation of CO in excess of H₂ (CO-PROX), in the 40–190°C temperature range.

Keywords: Hydrogen; CO-PROX; Copper; Ceria; Ceria–zirconia; Flower-like morphology

Comparison of the photocatalytic efficiencies of bare and doped rutile and anatase TiO₂ photocatalysts under visible light for phenol degradation and E. coli inactivation by G. Veréb; L. Manczinger; G. Bozsó; A. Sienkiewicz; L. Forró; K. Mogyorósi; K. Hernádi; A. Dombi (pp. 566-574).

Display Omitted► OH generation on VIS irradiated TiO₂ is crucial for disinfection processes. ► VLP7000 titania has high efficiency for phenol degradation under VIS irradiation. ► Large rutile particles (100–700nm) have high photocatalytic activity under VIS light. ► Rutile particles have excellent antibacterial property under solely VIS irradiation. ► Intensity of the lamps at 400–420nm is crucial for indoor photocatalytic processes.This study aimed at comparing the photocatalytic efficiencies of various TiO₂ based photocatalysts for phenol degradation and bacteria inactivation under illumination with visible light. Commercial undoped anatase and rutile (both from Aldrich), Aeroxide P25 (Evonik Industries), nitrogen-doped anatase (Sumitomo TP-S201, Sumitomo Chemical Inc.), nitrogen and sulphur co-doped anatase (Kronos VLP7000, Kronos Titan GmbH), and our custom-synthesized nitrogen- and iron-doped TiO₂, as well as nitrogen and sulphur co-doped Aeroxide P25 and silver- and gold-deposited Aeroxide P25 were studied. The photocatalytic efficiency of different types of titanium dioxide based photocatalysts was determined by inactivation of Escherichia coli K12 bacteria and by phenol decomposition. Electron spin resonance (ESR) in combination with spin trapping was used to get insight into the reactive oxygen species (ROS)-mediated photocatalytic processes in the presence of TiO₂-based photocatalysts. ESR results confirmed that titanias which generated OH radicals were efficient in E. coli disinfection, whereas titanias that were unable to produce OH radicals did not reveal significant bactericidal action. Three of our home-made titanias (iron-, nitrogen-, nitrogen/sulphur) as well as the commercial nitrogen/sulphur codoped Kronos VLP7000 TiO₂ showed higher efficiency of phenol degradation than the well-established reference photocatalyst, Aeroxide P25, but showed much lower (if any) activity for bacteria inactivation, including Kronos VLP7000, which revealed extremely high efficiency for phenol decomposition. Interestingly undoped Aldrich rutile (with large particles - 100–700nm) had the highest efficiency for inactivation of E. coli and also had fairly high activity of phenol degradation.

Keywords: Photocatalysis; Visible light; Disinfection; Hydroxyl radical; Doped titania; ESR; Singlet oxygen

New concepts for process intensification in the conversion of glycerol carbonate to glycidol by C.L. Bolívar-Diaz; V. Calvino-Casilda; F. Rubio-Marcos; J.F. Fernández; M.A. Bañares (pp. 575-579).

Display Omitted► Glycerol carbonate is an important glycerol derivative for the production of glycidol. ► Solvent-free conventional thermal activation, ultrasound- and microwave-activation. ► Selective transformation of glycerol carbonate into glycidol under mild conditions. ► ZSM-5 zeolite catalyst and a zinc oxide-supported nanoscaled cobalt oxide catalyst.Glycerol is a major by-product in biodiesel manufacturing, which surplus raises a critical need to transform it into high added-value products. In particular, glycerol carbonate is an important glycerol derivative being the most valuable intermediate for the production of glycidol, which is an added-value product of major industrial interest used, for example, as a precursor for the synthesis of a large number of polymers. Solvent-free conventional thermal activation, ultrasound-activation and microwave-activation in the liquid phase are able to selectively transform glycerol carbonate into glycidol under mild conditions using a ZSM-5 zeolite catalyst and a zinc oxide-supported nanoscaled cobalt oxide catalyst with short reaction times and in the absence of solvent. To the best of our knowledge, we report the highest selectivity to glycidol (>99%) from glycerol carbonate at high conversion values (71%).

Keywords: Glycidol; Glycerol carbonate; Biomass; Microwave activation; Ultrasonic activation

Catalytic combustion of chlorobenzene over Ru-doped ceria catalysts: Mechanism study by Qiguang Dai; Shuxing Bai; Xingyi Wang; Guanzhong Lu (pp. 580-588).

The mechanism of the catalytic combustion of chlorobenzene over pure CeO₂ and Ru doped CeO₂ catalysts can be described as that the CCl bond in chlorobenzene is dissociated easily on Ce³⁺/Ce⁴⁺ active sites, and the splitting chlorobenzene is rapidly oxidized into CO₂ and H₂O by surface reactive oxygen or lattice oxygen. The chlorine species adsorbed on the active sites can result in the rapid deactivation of catalysts and be removed in form of Cl₂ via the Deacon Reaction catalyzed by RuO₂ or CeO₂, improving the catalyst stability.Display Omitted► The mechanism of chlorobenzene catalytic combustion over CeO₂ based catalyst is proposed. ► The dissociatively adsorbed Cl can be removed in form of Cl₂ via the Deacon process. ► The Deacon Reaction is crucial for the stability of CeO₂ based catalysts. ► 1,4 and 1,2-dichlorobenzenes are the main by-products and from the partial chlorination of RuO₂ or CeO₂.To investigate the mechanism of the catalytic combustion of chlorobenzene over pure CeO₂ and Ru doped CeO₂ catalysts, we examined the oxidation reaction in depth by temperature-programmed surface reaction (TPSR) technique and a series of supplementary experiments. The results suggest that the CCl bond in chlorobenzene molecule can be dissociated easily on Ce³⁺/Ce⁴⁺ active sites, and the dissociated chlorobenzene can be rapidly oxidized into CO₂ and H₂O by surface reactive oxygen or lattice oxygen. The chlorine species dissociatively adsorbed on the active sites can result in the rapid deactivation of catalysts and be removed in form of Cl₂ via the Deacon Reaction catalyzed by RuO₂ or CeO₂, which would improve the catalyst stability. Additionally, the partial chlorination of RuO₂ or CeO₂ possibly occurs during the long reaction, which is responsible for the production of dichlorobenzene by-products.

Keywords: Chlorobenzene; Ceria; Ru; Catalytic combustion; Deacon Reaction; TPSR

Photocatalytic decomposition of pharmaceutical ibuprofen pollutions in water over titania catalyst by J. Choina; H. Kosslick; Ch. Fischer; G.-U. Flechsig; L. Frunza; A. Schulz (pp. 589-598).

Display Omitted► The photocatalytic decomposition of ibuprofen over TiO₂ was studied at low concentration. ► IBP and catalyst concentration and catalyst-to-substrate ratio were varied over a wide range. ► Rapid depollution under UV–Vis light is accompanied by formation of temporary by-products. ► ESI-TOF-MS analysis points to the formation of recalcitrant oligomeric intermediates. ► Re-use experiments show catalyst poisoning and increase of reaction intermediates.Due to the growing importance of low concentrated pollution of surface, ground and drinking, the photocatalytic decomposition of ibuprofen down to low ppm concentrations over titania catalyst has been investigated in detail. The catalyst was characterized by XRD, TEM, diffuse reflection UV–Vis and nitrogen adsorption measurement. The photocatalytic abatement of ibuprofen was monitored by UV–Vis spectrometry, chromatographic by GC/MS, and HPLC coupled electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). Catalytic performance has been studied by varying the catalyst and substrate concentration as well as decreasing the catalyst-to-substrate mass ratio over a wide range. The photocatalytic treatment with titania catalyst leads to rapid mineralization of ibuprofen. Formation of intermediate reaction products has been investigated. It is proposed that intermediates in part form oligomeric species, which are responsible for catalyst poisoning. Additional, the influence of the pH value, oxygen supply and catalyst re-use have been checked.

Keywords: Photocatalytic degradation; Ibuprofen; Pharmaceutical; Titania; Reaction intermediates; Oligomerization

Photocatalytic reduction of carbon dioxide to formic acid, formaldehyde, and methanol using dye-sensitized TiO₂ film by Guohui Qin; Yue Zhang; Xuebin Ke; Xinli Tong; Zhe Sun; Mao Liang; Song Xue (pp. 599-605).

Photocatalytic reduction of carbon dioxide to formic acid, formaldehyde, and methanol using dye-sensitized TiO₂ film.Display Omitted► A system mimics natural photosynthesis process on the principle of dye-sensitized solar cells. ► Light absorption and charge separation are performed in the DSC zone. ► The CO₂ reduction with transferring electrons was conducted at the catalysis zone. ► A highly efficient photo-reactor is designed for converting CO₂ to chemicals. ► The present results afford a promising platform for realization of renewable energy cycle.A bifunctionalized TiO₂ film containing a dye-sensitized zone and a catalysis zone is designed for visible-light photocatalytic reduction of CO₂ to chemicals continuously. Charge separation can be accomplished with electron transferring to catalysis zone and positive charge transforming to anode. Highly efficient conversion of CO₂ to formic acid, formaldehyde, and methanol is achieved through the transferring electrons on conduction bands (CB) of TiO₂. Reduction of CO₂ and O₂ evolution take place in separated solutions on different catalysts. The separated solution carried out in this photo-reactor system can avoid CO₂ reduction products being oxidized by anode. The yields of reduction products were enhanced remarkably by external electrical power. This study provides not only a new photocatalytic system but also a potential of renewable energy source via carbon dioxide.

Keywords: Photocatalysis; Dye-sensitized TiO; ₂; CO; ₂; reduction; Electron transfer

Fabrication of CNTs and GP/AuGP modified TiO₂ photocatalyst with two-channel electron conduction path for significantly enhanced photocatalytic activity by Wei Wang; Chunhua Lu; Yaru Ni; Zhongzi Xu (pp. 606-613).

Display Omitted► GP/AuGP and CNTs comodified TiO₂ was obtained. ► There was a strong interaction between TiO₂ and carbon materials. ► The introduced two-channel path was very effective for electrons transformation. ► The solar light was used sufficiently. ► The photoactivity was significantly enhanced compared to P25.A systematic study has been devoted to fabricate carbon nanotubes (CNTs), graphene (GP), and Au deposited graphene (AuGP) modified semiconductor photocatalysts with specific structures. We show a systematic investigation on improving the photocatalytic activity of TiO₂ via a strategy of locating CNTs inside and GP/AuGP outside TiO₂ nanoparticles, respectively. To enhance the interaction between TiO₂ and CNTs/GP/AuGP, TiO₂ was directly grown on the surface of CNTs and GP/AuGP was covered on the entire surface of CNTs modified TiO₂ by the hydrothermal method. Au was used to fabricate a Schottky barrier on the TiO₂ and Au interface, resulting more efficient electron transfer by the Au particles and GP. The CNTs@TiO₂@GP and CNTs@TiO₂@AuGP nanocomposites which show higher photoactivity than P25 prepared by this method is able to make efficient use of the electron conductivity of Au, GP, and CNTs, resulting in more efficient transfer of the photogenerated electrons and, hence, inhibit the photogenerated electron–hole pair recombination, thus the solar energy was more efficiently used to decompose the pollutants. This simple method is of great significance for the design and preparation of high active photocatalysts with specific structures for pollutant decomposition.

Keywords: Graphene; Carbon nanotube; TiO; ₂; Au deposition; Photoactivity

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Applied Catalysis B, Environmental (v.129, #)