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Applied Catalysis B, Environmental (v.74, #1-2)

IFC Editorial Board (pp. co2).

Editorial Board (pp. i).

Contents (pp. co4).

Contents Continued (pp. iv).

Combustion of volatile organic compounds on manganese iron or nickel mixed oxide catalysts by María Roxana Morales; Bibiana P. Barbero; Luis E. Cadús (pp. 1-10).

Manganese iron or nickel mixed oxide catalysts (MnFe or MnNi, respectively) were obtained by coprecipitation varying the aging time. A detailed description of the bulk and surface structure of each system was achieved by means of measurements of specific surface area, XRD, XPS, FT-IR, and Mössbauer spectroscopies. The characterisation results show that MnNi catalysts are formed by NiMnO₃ and Ni₆MnO₈ mixed oxides besides a little amount of Mn₂O₃. In contrast, MnFe catalysts consist of an oxide mixture (Fe₂O₃, Mn₂O₃ and Mn₅O₈) forming incipiently a solid solution. The catalytic activity was evaluated in the combustion of propane and ethanol, selected as model volatile organic compounds. In propane combustion, the best results were obtained with MnNi catalysts whereas MnFe catalysts showed the best performance in ethanol combustion. The catalytic behaviour was correlated with catalyst affinity by oxygen, which was determined by studies of O₂-TPD and TPR. The variation of the precipitated aging time modifies neither the catalyst structure nor the catalytic performance.

Keywords: Manganese; Iron; Nickel; Oxides; Coprecipitation; Aging time; Combustion; VOCs

Catalytic wet peroxide photo-oxidation of phenolic olive oil mill wastewater contaminants by Wahiba Najjar; Samia Azabou; Sami Sayadi; Abdelhamid Ghorbel (pp. 11-18).

The catalytic photo-oxidation of tyrosol, a representative compound of the polyphenolic fraction typically found in olive processing wastewaters, has been investigated using Al–Fe pillared clay. The montmorillonite was pillared by mixed Al–Fe complexes, its properties being determined by DRX, BET surface area and chemical analysis techniques. The tests were performed on a laboratory scale set-up.Important factors affecting catalyst activity and tyrosol removal efficiencies were studied, mainly, the concentrations of the catalyst, tyrosol pollutant and H₂O₂ oxidant. The effect of pH and temperature was also investigated. A pseudo-first-order kinetics with respect to the tyrosol concentration was found to hold. The experimental results indicate that under mild conditions and oxidant contents lower than stoichiometric (28%), the use of (Al–Fe) pillared montmorillonite allows a significant TOC abatement and a total elimination of tyrosol, without significant leaching of Fe ions. The toxic potential of tyrosol degradation was investigated with the bioluminescence test using the LUMIStox and the results were expressed as relative toxicity index.

Keywords: Catalytic wet peroxide oxidation; Iron; Pillared clay; Toxicity; Tyrosol; UV light

A combinatorial approach for the discovery of low temperature soot oxidation catalysts by Nelson E. Olong; Klaus Stöwe; Wilhelm F. Maier (pp. 19-25).

High-throughput syntheses using a commercial pipetting robot with the aid of the software “Plattenbau” as well as a highly parallel screening technique were used in the search of low temperature soot oxidation catalysts. It has been shown that emissivity-corrected infrared thermography which monitors the heat changes resulting from the heat of reaction on catalyst surfaces is an efficient and fast screening technique of soot oxidation catalysts. It was found that alkali metal mixed oxides have the potential to decrease the soot oxidation temperature to diesel exhaust realistic temperatures. From the first generation, the oxides K₃Ce₉₇ and Cs₃Co₉₇ were found to be the most active and stable samples. Further doping and composition spread of the CsCo catalyst resulted in even more active samples. HT-screening experiment hits were successfully confirmed by thermogravimetric analysis.

Keywords: Diesel soot combustion; Combinatorial synthesis; High-throughput screening

Nanosized Ti–V mixed oxides: Effect of doping level in the photo-catalytic degradation of toluene using sunlight-type excitation by A. Kubacka; A. Fuerte; A. Martínez-Arias; M. Fernández-García (pp. 26-33).

In this report we investigate the behavior of nanosized Ti–V mixed oxides with anatase structure in the photo-elimination of toluene using sunlight-type excitation. These systems were prepared by a microemulsion method and their physico-chemical properties characterized by a multitechnique approach using X-ray diffraction, electron paramagnetic resonance, Raman, and UV–vis spectroscopies. The preparation method allows the incorporation of significant amounts of vanadium in the anatase structure and two well-differentiated structural/electronic situations occur for samples having a V content below/above ca. 5at.%. The photo-activity of the Ti–V samples reached a maximum for a sample having a vanadium content of ca. 2.5at.%, which displays a reaction rate 2.3/2.7 times larger than the parent-TiO₂/P25 references. The chemical/physical bases of such behavior are discussed in light of the characterization results.

Keywords: Photo-catalysis; Binary Ti–V mixed oxides; TiO; ₂; Anatase; Visible and sunlight light absorption and excitation; Pollutant and toluene mineralization and degradation

The role of Al and strong acidity in the selective catalytic oxidation of NH₃ over Fe-ZSM-5 by Aaron C. Akah; George Nkeng; Arthur A. Garforth (pp. 34-39).

Fe-ZSM-5 catalysts prepared using different techniques have been used to highlight the role of aluminium-associated sites and hence Bronsted acidity during the selective catalytic oxidation (SCO) of NH₃. NH₃–TPD was used to characterise the type of acidity and the number of acid sites in the Fe-ZSM-5 materials. Catalysis was carried out in a fixed bed Pyrex micro reactor operated at atmospheric pressure and a temperature range of 623–723K. Results show that catalysts with no Al and hence possessing only weak acidity had lower performance during the SCO of NH₃. The presence of Al in the zeolite framework is believed to be of importance in stabilising the Fe active species. The oxidative activity of the catalysts was thus found to depend on the presence or absence of Al, whilst only Fe-H-[Al]ZSM-5 catalyst was both active and selective.

Keywords: Selective catalytic oxidation (SCO); Fe-ZSM-5; Bronsted acidity; Aluminium; Ammonia; Ammonia-TPD

Estimating the temperatures of the NO_x storage sites in a lean NO_x trap during oxidation reactions by Joseph R. Theis; Erdogan Gulari (pp. 40-52).

The maximum temperatures of the potassium NO_x storage sites on a 0.64cm long monolithic platinum/potassium/alumina lean NO_x trap (LNT) have been estimated during propylene (C₃H₆) oxidation under net lean conditions. This was accomplished by saturating the LNT with NO_x, injecting a high concentration of C₃H₆ for a specified period of time, estimating the amount of NO_x released from the LNT as a result of the C₃H₆ injection by calculating the amount of NO_x restored during a second saturation period after the injection, and comparing the amount of NO_x remaining on the LNT after the injection to a capacity versus temperature calibration curve. The LNT was evaluated behind a thermally aged Pd/Al₂O₃ three-way catalyst, which provided negligible NO_x storage capacity but oxidized most of the C₃H₆. The projected temperature increase of the NO_x storage sites on the LNT was in reasonable agreement with the temperature increase of the exhaust gas exiting the sample for different C₃H₆ concentrations, injection times, and base temperatures, which validated the technique. When the TWC was removed and 1800ppm C₃H₆ was injected at a base temperature of 330°C, the measured temperature of the exit gas and the inferred temperature of the NO_x storage sites increased by approximately 65 and 102°C, respectively, under steady-state conditions. The elevated temperature of the NO_x storage sites relative to that of the exit gas was attributed to the very high temperatures generated on the neighboring precious metal sites of the LNT.

Keywords: Abbreviations; LNT; lean-NO; _x; trap; NS5; NO; _x; stored with final instantaneous storage efficiency of 5%; SCR; selective catalytic reduction; TWC; three-way catalystLNT; precious metal; NO; _x; storage site; Washcoat; Temperature; HC oxidation

Immobilization of TiO₂ on perlite granules for photocatalytic degradation of phenol by S.N. Hosseini; S.M. Borghei; M. Vossoughi; N. Taghavinia (pp. 53-62).

The photocatalytic degradiation of phenol by nanoTiO₂ particles coated on perlite as a new composite nano-catalyst was investigated. Titanium dioxide (Degussa P-25) was immobilized on three different supports (perlite granules, glass plates and steel fiber) by a very simple and inexpensive method. Perlite granules have a porosity of more than 95%, which allows them to stay afloat on water surface. This gives the medium a unique characteristic from the processing point of view, which enables it to get wetted with the polluted solution without requiring any pumping and simultaneously be exposed to the radiation source when coated with the photocatalyst.The photocatalytic activity of prepared catalysts was tested in appropriate batch reactors. HPLC analyses was used for measuring the concentration of components, XRD and SEM analyses was carried out for characterization including anataze-rotile phase ratio, crystal size and morphology of prepared catalysts.The XRD results did not reveal any significant changes in the structure of P-25 as a consequence of the applied immobilization process. Also, well and uniform coating of TiO₂ on supports were confirmed by SEM method. The obtained results of the photocatalytic treatment experiments of water synthetically polluted with phenol showed a fairly good performance for the three immobilized catalysts. The rate of phenol degradation was positively affected by UV light intensity, according to different intensity of UV lamps, the kinetics of photocatalytic reaction follows a pseudo-first-order model.Also control experiments confirmed that the effects of adsorption and degradation of phenol onto the TiO₂/perlite catalysts in the dark conditions were negligible.

Keywords: Photocatalysis; Phenol; Titanium dioxide (TiO; ₂; ); Perlite; Steel Fiber

Sonolytic, photocatalytic and sonophotocatalytic degradation of malachite green in aqueous solutions by C. Berberidou; I. Poulios; N.P. Xekoukoulotakis; D. Mantzavinos (pp. 63-72).

The degradation of malachite green (MG) in water by means of ultrasound irradiation and its combination with heterogeneous (TiO₂) and homogeneous photocatalysis (photo-Fenton) was investigated. Emphasis was given on the effect of key operating conditions on MG conversion and mineralization rates and the elucidation of major reaction by-products. Eighty-kilohertz of ultrasound irradiation was provided by a horn-type sonicator, while a 9W lamp was used for UV-A irradiation. The extent of sonolytic degradation increased with increasing ultrasound power (in the range 75–135W) and decreasing initial concentration (in the range 2.5–12.5mgL⁻¹), while the presence of TiO₂ in the dark generally had little effect on degradation. Sonolysis under argon was substantially faster than under air, oxygen or helium leading to complete MG degradation after 120min at 10mgL⁻¹ initial concentration and 135W ultrasound power. On the other hand, TiO₂ photocatalysis or photo-Fenton led to complete MG degradation in 15–60min with the rate increasing with increasing catalyst loading (in the range 0.1–0.5gL⁻¹ for TiO₂ and 7–20mgL⁻¹ for Fe³⁺) and also depending on the gas used. TiO₂ sonophotocatalysis was always faster than the respective individual processes due to the enhanced formation of reactive radicals as well as the possible ultrasound-induced increase of the active surface area of the catalyst. For instance, the pseudo-first order rate constant for the sonophotocatalytic degradation at 0.5mgL⁻¹ TiO₂ under air was 136.7×10⁻³min⁻¹ with the respective values for photocatalysis and sonolysis being 112.6×10⁻³ and 11.6×10⁻³min⁻¹. Irrespective of the process employed, mineralization was slower than MG decomposition implying the formation of stable by-products accompanied by the release of nitrates in the solution. GC/MS analysis verified the identity of primary intermediates and a reaction pathway based on them was proposed. Depending on the conditions employed, ecotoxicity of MG to marine bacteria was partly or fully eliminated.

Keywords: Intermediates; Malachite green; Photocatalysis; Sonolysis; Toxicity; Water

Dual-catalyst aftertreatment of lean-burn natural gas engine exhaust by Erik M. Holmgreen; Matthew M. Yung; Umit S. Ozkan (pp. 73-82).

A dual-catalyst system for the reduction of NO with CH₄ under lean conditions was investigated. The system is comprised of a mixed bed containing a Co/ZrO₂ catalyst, active for the oxidation of NO to NO₂, and a Pd/sulfated zirconia (SZ) catalyst that is active for the reduction of NO₂ with CH₄. Such a system is capable of taking advantage of higher reduction rates for NO₂, as compared to NO, that have been previously observed. When simulated exhaust streams from lean-burn natural gas engines are used as feed, the dual-catalyst system is simultaneously active for the reduction of NO_x and the oxidation of unburned hydrocarbons and CO.

Keywords: NO; _x; reduction; Hydrocarbon oxidation; Cobalt; Palladium; ZrO; ₂; Lean-burn; Natural gas; Sulfated zirconia

Influence of Zr as TiO₂ doping ion on photocatalytic degradation of 4-chlorophenol by J. Lukáč; M. Klementová; P. Bezdička; S. Bakardjieva; J. Šubrt; L. Szatmáry; Z. Bastl; J. Jirkovský (pp. 83-91).

Nanosized Zr-doped TiO₂ photocatalysts were prepared using the homogenous co-precipitation method from aqueous solutions containing TiOSO₄ and ZrCl₄ by urea as a precipitation agent, with subsequently annealing at various temperatures of 400–1100°C. Structural changes of the photocatalysts upon heating were studied by X-ray powder diffraction. Anatase-to-rutile phase transformation is shifted to higher temperatures in comparison with undoped TiO₂. Spherical clusters morphology was revealed by scanning electron microscopy. Energy dispersive X-ray spectrometry confirmed a Zr content of 0.8mol% in all samples. The band-gap energies were determined from diffuse reflectance UV–vis spectra. The spectral thresholds are shifted toward visible region, except for the unheated catalyst. X-ray photoelectron spectroscopy measurements revealed that the binding energy of Ti 2p_3/2 electrons is not influenced by Zr doping. On the contrary, the binding energy of Zr 3d_5/2 electrons is lower than that of Zr ions in ZrO₂. Photocatalytic degradation of 4-chlorophenol was employed to test photoactivity of the catalyst. The photocatalyst annealed at 900°C has a 1.5 times higher degradation rate than the standard TiO₂ P25 (Degussa).

Keywords: Zr-doped TiO; ₂; Anatase; Rutile; Photocatalysis; Urea; Homogenous co-precipitation; 4-Chlorophenol

The influence of Ni load and support material on catalysts for the selective catalytic oxidation of ammonia in gasified biomass by S. Nassos; E. Elm Svensson; M. Boutonnet; S.G. Järås (pp. 92-102).

The effect of nickel (Ni) load (0, 5 and 10wt.%) and support material (Ce_0.9La_0.1O₂, Ce_0.9Zr_0.1O₂ and γ-Al₂O₃), together the amount of oxygen ( λ=0.25 and λ=0.5) and gas hourly space velocity (50000, 100000 and 150000h⁻¹) were investigated for the selective catalytic oxidation of ammonia in gasified biomass. The mixed metal oxide support materials were prepared by microemulsion, whereas the alumina was a commercial product. Ni was added to the different supports by incipient wetness. All the obtained catalysts were characterised by BET and XRD analysis. Cordierite monoliths coated with 20wt.% catalytic material were tested in a tubular quartz reactor. For simulating the gasified biomass fuel, 500ppm of NH₃ was added to the fuel. Water was also present during the activity tests, which were carried out between 500 and 750°C.The results from the activity tests at λ=0.25 and gas hourly space velocity of 100000h⁻¹ indicated that the 10wt.% Ni on Ce_0.9La_0.1O₂ was the best catalyst obtaining 65 and 97% N₂ yield at 500 and 750°C, respectively. By increasing λ to 0.5 and decreasing the gas hourly space velocity, the N₂ yield improved considerably at low temperature level (500°C). Moreover, NO_x emissions maintained at low levels depending on the experimental conditions. Constant conversion and negligible carbon deposition were also two other important observations from the mixed metal oxide supported catalysts. On the contrary, all the alumina-based catalysts displayed the lowest performance.

Keywords: Selective catalytic oxidation; Biomass; Microemulsion; Mixed metal oxides; Nitrogen yield; Lambda; Gas hourly space velocity

Photocatalytic reduction of 4-nitrophenol with arginine-modified titanium dioxide nanoparticles by Won-Young Ahn; Sarah A. Sheeley; Tijana Rajh; Donald M. Cropek (pp. 103-110).

The surface charge of titanium dioxide (TiO₂) affects the adsorption rates of target molecules, thereby influencing the associated photocatalytic degradation rates of these molecules. This study describes the specific photocatalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with arginine-modified TiO₂ (Arg–TiO₂) nanoparticles. 4-AP was the only identifiable by-product detected by chromatographic analysis. The terminal amine groups of the arginine monolayer create a positive TiO₂ surface charge over a wide range of pH values. At high pH, the degradation rate of 4-NP increased due to improved target adsorption. Furthermore, the presence of the arginine monolayer perturbs the degradation mechanism distribution of 4-NP away from indiscriminant oxidation toward selective reduction. Photocatalysis of a target molecule such as benzenesulfonic acid (BSA) showed that while electrostatic attraction of the target to the photocatalyst is important, the reduction potential of the target molecule dictates efficient degradation on Arg–TiO₂.

Keywords: Photocatalysis; Nitrophenol; Surface-modified titanium dioxide

The removal of dichloromethane from atmospheric pressure nitrogen gas streams using plasma-assisted catalysis by Anna E. Wallis; J. Christopher Whitehead; Kui Zhang (pp. 111-116).

A non-thermal, atmospheric pressure plasma utilising a dielectric packed bed was used to study the destruction of dichloromethane, CH₂Cl₂, (DCM) in gas streams of nitrogen with the presence of catalysts. The effect of plasma-assisted catalysis was investigated in two configurations; one where the catalyst was incorporated into the packed bed itself and the other where the catalyst was downstream of the plasma. The combination of plasma and a catalyst allowed improved destruction of DCM. γ-Al₂O₃ in a one-stage reactor configuration was the most successful in terms of the total destruction of DCM as well as providing the best result in the two-stage reactor configuration compared with the eight catalysts chosen which included alumina, TiO₂ and various zeolites. Products as detected by FTIR were CO, CO₂, HCN, HCl and H₂O with the by-product of N₂O. The nature of the catalyst plays a vital role with respect to the effectiveness of DCM destruction and the selectivity of the end-products.

Keywords: Dichloromethane; FTIR; Non-thermal plasma; Catalysis; Alumina; Titanium dioxide; Zeolites

The effects of regeneration conditions on NO_X and NH₃ release from NO_X storage/reduction catalysts by William S. Epling; Aleksey Yezerets; Neal W. Currier (pp. 117-129).

A standard protocol developed by the Cross-Cut Lean Exhaust Emissions Reduction Simulations (CLEERS) group was used to investigate the evolution of N-byproduct species and the release of unreduced NO_X from a commercial NO_X storage/reduction (NSR) catalyst. NH₃ was readily formed at temperatures below 375°C, and the onset of its formation was typically observed coincident with reductant breakthrough. N₂O was also observed at these lower test temperatures. The rate of NO_X release, as both NO and NO₂, increased with increasing temperature due to decreasing nitrate stability. Reduction of NO_X necessarily involved the presence of reductant, which was also used to titrate oxygen species from oxygen-storage components such as ceria. Changes in the release of unreduced NO_X from the catalyst as a function of temperature were directly attributable to the temperature dependencies of nitrate stability and decomposition, NO_X diffusion to the precious metal sites, the rate of the NO_X reduction reaction and the rate of reduction of these oxygen-storage components. Furthermore, by accounting for the amount of reductant needed for titration of the oxygen-storage components and the amount of NO_X trapped, mass balance calculations were performed and used to estimate the amounts of residual nitrates on the catalyst surface after regeneration. These calculations indicate that only at the lower temperatures were the regenerations not effective enough to remove all the trapped NO_X.

Keywords: NO; _X; reduction; NO; _X; storage; Diesel emissions

The photodecomposition of phosmet over UV irradiated silver nanoclusters doped in mordenite zeolite by Sofian M. Kanan; Imad A. Abu Yousef; Naser M. Abdo (pp. 130-136).

Ag(I) nanoclusters doped in mordenite zeolite were prepared and spectroscopically analyzed. Both experimental and theoretical results show the presence of silver nanoclusters with various sizes and environments in the zeolite hosts. The study indicates that the low energy emission mode (at 520nm) was gradually activated and the high energy mode (at 415nm) was deactivated upon increasing the excitation wavelength from 250 to 300nm. The catalyzed system increases the photodecomposition of phosmet in comparison with the uncatalyzed experiment upon irradiation with different UV lights. Moreover, the largest catalytic activity was observed upon the irradiation of the catalyzed solution with 302nm where an increase in the decomposition rate by 40-fold was observed. The photodecomposition products are similar for all systems but variations in the relative amount of these products were observed at different conditions. Both catalyzed systems indicate the formation of phosphorothionic acid (3) as the major product.

Keywords: Zeolites; Silver nanoclusters; Phosmet; Photodecomposition; Pesticides; DMMP

NO adsorption/desorption property of TiO₂–ZrO₂ having tolerance to SO₂ poisoning by Kazuhiro Ito; Shuichi Kakino; Keita Ikeue; Masato Machida (pp. 137-143).

The effect of SO₂ on the adsorption and desorption properties of NO was studied over TiO₂–ZrO₂ and γ-Al₂O₃. The microporous binary oxide, TiO₂–ZrO_2, exhibited a large amount of sorptive NO_x uptake (ca. 1mmolg⁻¹) at 25°C in the presence of O₂ and SO₂. The irreversible chemisorption as nitrate (NO₃) is a main cause for the large NO uptake. Desorption of NO_x from TiO₂–ZrO₂ occurred at lower temperature of ca.450°C, compared to ≥500°C required for that from γ-Al₂O₃. A similar trend was observed for the SO_x desorption, because SO₂ adsorbed on γ-Al₂O₃ is a stable sulfate-type (SO₄), whereas less stable sulfite (SO₃) is dominant species on the surface of TiO₂–ZrO₂. The SO_x desorption could further be facilitated in the presence of reducing agents like CO. The thermal swing adsorption/desorption cycle experiment demonstrated that TiO₂–ZrO₂ can be used as an NO_x adsorbent having improved tolerance to SO₂. The SO₂ tolerance can be explained by the weak basicity of TiO₂–ZrO₂ and the low activity to oxidize SO₂ to form sulfate species on the surface.

Keywords: TiO; ₂; –ZrO; ₂; Nitric oxide; Oxidative adsorption; SO; _x; -tolerance

Hydrogen production from dimethyl ether steam reforming over composite catalysts of copper ferrite spinel and alumina by Kajornsak Faungnawakij; Yohei Tanaka; Naohiro Shimoda; Tetsuya Fukunaga; Ryuji Kikuchi; Koichi Eguchi (pp. 144-151).

Dimethyl ether steam reforming (DME SR) was performed over composite catalysts of copper ferrite spinel (CuFe₂O₄) and alumina for hydrogen production, applicable to fuel cell. A highly active composite was achieved when the calcination temperature of the Cu spinel was at 900°C and that of the alumina was at or below 700°C. The calcination temperature strongly affected the crystallinity and reducibility of the copper ferrite spinel and the acidity of alumina. The composite catalysts both with and without pre-reduction were active for DME SR when the pre-reduced catalyst exhibited higher initial activity, but longer activation process was observed for the composite catalyst without pre-reduction. DME conversion and hydrogen production significantly depended on gas hourly space velocity (GHSV) and reforming temperatures ( T_r). DME conversion (>95%), H₂ production rate (∼50molkg_cat⁻¹h⁻¹), and H₂ concentration (ca. 73%) were achieved at T_r of 350°C and GHSV of 1500h⁻¹. The maximum H₂ production rate of 120molkg_cat⁻¹h⁻¹ was found at T_r of 450°C and GHSV of 4000h⁻¹. Mixing state of the copper spinel and the alumina was also investigated. After mixing with alumina, the present CuFe₂O₄ markedly exhibited excellent activity for DME SR in comparison to the commercial CuFe₂O₄ and Cu/ZnO/Al₂O₃.

Keywords: Copper ferrite spinel; Steam reforming; Dimethyl ether; Hydrogen; Fuel cell

Solar photocatalytic disinfection of agricultural pathogenic fungi: Fusarium species by C. Sichel; M. de Cara; J. Tello; J. Blanco; P. Fernández-Ibáñez (pp. 152-160).

The ability of solar-only and solar photocatalytic (TiO₂) disinfection batch-process reactors to inactivate fungal pathogens was evaluated. The photocatalytic disinfection of five wild strains of the Fusarium genus ( F. equiseti, F. oxysporum, F. anthophilum, F. verticillioides, and F. solani), a common plant pathogen in Spain and around the world, was successfully achieved. Different disinfection times (1–6h) were necessary to inactivate a fungus concentration in water of 10³CFU/mL to almost zero by solar photocatalysis. The order of sensitivity to solar disinfection was F. oxysporum> F. solani> F. verticillioides> F. anthophilum> F. equiseti. The presence of the TiO₂ photocatalyst under solar radiation showed a positive effect on lost fungus viability. The photocatalytic disinfection times were shorter and disinfection better than for solar-only disinfection. The order of photocatalytic sensitivity was different from solar disinfection: F. verticillioides> F. oxysporum> F. solani> F. anthophilum> F. equiseti.

Keywords: Solar disinfection; TiO; ₂; photocatalysis; Fusarium; Soilborne fungus

Efficient toluene abatement in indoor air by a plasma catalytic hybrid system by J. Van Durme; J. Dewulf; W. Sysmans; C. Leys; H. Van Langenhove (pp. 161-169).

Numerous indoor sources emit volatile organic compounds, NO_x and O₃ which all have a negative effect on human health. Previous work proved that plasma technology seems promising. However, some disadvantages occur such as high energy cost and the formation of by-products.In this work in-plasma (IPC) and post-plasma (PPC) catalysis was investigated for indoor air purification. Introducing a TiO₂ catalyst in-plasma was not effective in ozone reduction. Adding only 10g of CuOMnO₂/TiO₂ post-plasma position, resulted in a reduction of the ozone outlet concentration by a factor 7. Humidity proved to have a limiting effect on ozone removal rates.In dry air toluene ( C_in=0.5ppm_v) was removed three times more efficient by introducing Aerolyst^®7706 TiO₂ (IPC). In humid conditions (RH=27%) performance of this IPC decreased: toluene abatement was only 1.5 times more efficient compared with the non-catalytic plasma oxidation. For dry air inserting 10g CuOMnO₂/TiO₂ down flow the plasma reactor modules (PPC), resulted in toluene removal efficiencies up to 40 times higher. In humid gas streams, PPC toluene removal efficiency decreased by competitive adsorption.NO_x production by the corona discharge was monitored. In dry air and for an energy density of 10JL⁻¹, the NO₂ outlet concentration was 1500ppb_v, while this is three times lower at 50% RH. Both heterogeneous catalysts (TiO₂ and CuOMnO₂/TiO₂) proved capable to reduce NO_x levels in the outlet gas stream by up to 90%.Deactivation of the catalyst material may be explained by the formation of HNO₃ in the plasma discharge. These molecules adsorb on the catalyst, surface nitrate ion concentrations were 0.184mg/m² and 0.143mg/m² for TiO₂ and MnO₂–CuO/TiO₂ catalysts, respectively.

Keywords: Abbreviations; dc; direct current; PDMS; polydimethylsiloxane; RH; relative humidity; SPME; solid-phase microextraction; VOC; volatile organic compound; PM; particulate matter; WHO; World Health Organization; IAQ; indoor air quality; IC; ion chromatograph; PAH; poly cyclic aromatic hydrocarbon; NTP; non-thermal plasma; IPC; in plasma catalysis; PPC; post-plasma catalysis; FID; flame ionisation detector; GC; gas chromatograph; ppb; _v; parts per billion (volumetric/gas); =; 1; μL; m; ⁻³; ppm; _v; parts per million (volumetric/gas); =; 1; mL; m; ⁻³; C; _in; inlet concentration (ppm; _v; 1; mL; m; ⁻³; ); C; N; O; 2; ,; out; outlet concentration of NO; ₂; (ppm; _v; 1; mL; m; ⁻³; ); Q; _air; gas flow rate (m; ³; /h); P; pressure (Pa); T; temperature (K)Corona discharge; Nitrogen oxides; Ozone degrading catalyst; Photocatalyst; Toluene

Nanocrystalline cobalt oxide immobilized on titanium dioxide nanoparticles for the heterogeneous activation of peroxymonosulfate by Qiujing Yang; Hyeok Choi; Dionysios D. Dionysiou (pp. 170-178).

Recently, sulfate radical-based advanced oxidation technologies have shown significant implications for environmental remediation to decompose water pollutants. In this study, we evaluated the performance of heterogeneous activation of peroxymonosulfate (PMS) to generate sulfate radicals using cobalt catalyst immobilized on titanium dioxide nanoparticles (Co/TiO₂). The Co/TiO₂ catalyst was prepared via an incipient wetness impregnation method employing Degussa P-25 TiO₂ and Co(NO₃)·6H₂O. The activity of Co/TiO₂ system was compared with those of Co(NO₃)₂ solution for homogeneous PMS activation and neat Co₃O₄ for heterogeneous PMS activation. More emphasis was given to the effect of cobalt loading and heat treatment on the physicochemical properties of Co/TiO₂ and cobalt leaching. The results showed that heat treatment of Co/TiO₂ at 500°C, where cobalt existed as Co₃O₄, induced negligible Co leaching and enhanced catalytic activity to decompose 2,4-dichlorophenol. The Co/TiO₂ catalyst at Co/Ti molar ratio of 0.1 showed the highest activity via heterogeneous PMS activation. On the other hand, Co/TiO₂ catalysts with Co/Ti molar ratio of above 0.2 exhibited rather much lower activity which was initiated predominantly via a homogeneous pathway from leached cobalt, although they contained considerable amounts of Co₃O₄. The formation of CoOH complexes at the surface of Co/TiO₂ nanoparticles, due to the ability of TiO₂ to dissociate H₂O for the formation of surface hydroxyl groups, was proposed to facilitate the heterogeneous PMS activation. However, high cobalt loading covering the TiO₂ surface diminished the beneficial role of TiO₂ due to the reduction in the concentration of surface hydroxyl groups and thus decreased the heterogeneous PMS activation. The activity of Co₃O₄ in Co/TiO₂ catalysts was much higher than that of neat Co₃O₄ due to the presence of surface hydroxyl groups and uniform distribution of well-defined 10−15nm nanocrystalline Co₃O₄ particles at the surface of 30−40nm TiO₂ nanoparticles.

Keywords: 2,4-Dichlorophenol; Advanced oxidation processes (AOPs); Advanced oxidation technologies (AOTs); Calcination; Co; ₃; O; ₄; Cobalt; Co; OH complexes; Heterogeneous reaction; Homogeneous reaction; Leaching; Nanoparticles; Oxone; Peroxymonosulfate; Sulfate radicals; Surface hydroxyl groups; Titanium dioxide; Titania

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Applied Catalysis B, Environmental (v.74, #1-2)

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Applied Catalysis B, Environmental (v.74, #1-2)