Chemical Engineering Journal (v.173, #2)
Treatment of simulated industrial wastewater by photo-Fenton process. Part I: The optimization of process parameters using design of experiments (DOE)
by Marina Dopar; Hrvoje Kusic; Natalija Koprivanac (pp. 267-279).
The study reported the application of the photo-Fenton process for the treatment of simulated industrial wastewater upon pretreatment by the dark-Fenton process. The process efficiency which depends on several important process parameters such as initial pH, iron catalyst and oxidant concentration, and the UV irradiation type, was investigated. To consider the combined effects of studied process parameters, three-factor three-level Box–Behnken experimental design combined with response surface modeling was applied. The quadratic models predicting the mineralization of simulated industrial wastewater by the applied photo-Fenton processes were developed. ANOVA was applied to evaluate the significance of models and models’ components. The obtained results indicated that both models can be characterized as highly accurate and predictive for the mineralization of simulated industrial wastewater. Our results show that both photo-Fenton processes can be successfully applied for the treatment of the studied simulated industrial wastewater. The presence of oxalates in simulated industrial wastewater strongly influenced the conditions for the maximal efficiency of applied photo-Fenton processes regarding the type of UV irradiation. The optimal conditions were determined to be: initial pH 3.88, [Fe2+]=5.01mM (along with [Fe3+]=8.0mM) and [H2O2]=30mM in the case of photo-Fenton process operated with UV-C irradiation; and pH 1.9, [Fe2+]=8.39mM (along with [Fe3+]=8.0mM) and [H2O2]=30mM in the case of UV-A light application. The “pseudo”-second order mineralization kinetic of simulated industrial wastewater was determined in both cases with the calculated rate constants at determined optimal conditions: k1obs=12.94×10−2M−1s−1 and k2obs=9.71×10−2M−1s−1 for UV-C/Fe/H2O2 and UV-A/Fe/H2O2 processes, respectively.
Keywords: Industrial wastewater; Photo-Fenton; Ferrioxalate; Process optimization; Design of experiments; Statistical analysis
Treatment of simulated industrial wastewater by photo-Fenton process: Part II. The development of mechanistic model
by Marina Simunovic; Hrvoje Kusic; Natalija Koprivanac; Ana Loncaric Bozic (pp. 280-289).
The aim of the study was to develop the mechanistic model describing the behavior of photo-Fenton process treating the simulated industrial wastewater containing oxalates and formates. In Part I of the study, the optimal conditions for each of applied photo-Fenton processes (UV-C/Fe/H2O2 and UV-A/Fe/H2O2) were determined and used in this study for model development and verification. The mechanistic model simulates the influence of various factors: the type of UV irradiation, the changes in concentrations of pollutants, catalysts and oxidant, on photo-Fenton process performance. pH dependent equilibrium of ferrous, ferric, oxalate and formate species was simulated as well. The model was tested to evaluate its accuracy in predicting the system behavior at different pollutant concentrations. Good agreement of the data predicted by model and the empirically obtained values was confirmed by calculated standard deviation for each experimentally monitored parameter. The developed mechanistic model describing the behavior of photo-Fenton process treating simulated wastewater can be characterized as interpretable, transparent, flexible and accurate. The comparison of electrical energy costs for each of the studied processes was performed. The obtained results indicate that the process using UV-C source is more efficient and cheaper. However, the simulation of process effectiveness using the solar UV-A irradiation recorded at annual basis for the location of proposed wastewater treatment plant speaks in the favor of solar UV-A/Fe/H2O2 process application instead of artificial UV irradiation.
Keywords: Simulated industrial wastewater; Photo-Fenton; Ferrioxalate; Mechanistic model; Cost evaluation; Solar irradiation
Oxidation of methylated arsenic species by UV/S2O82−
by Sung-Hwan Yoon; Seockheon Lee; Tae-Hun Kim; Myunjoo Lee; Seungho Yu (pp. 290-295).
UV/S2O82− process was studied for the oxidation of monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in aqueous solution. UV/H2O2 and UV/TiO2 were also applied to the oxidation of the target compounds. TiO2 was added at a low dosage (50mg/L), considering a condition advantageous for catalyst separation. Under the experimental condition of this study ([S2O82−]0=[H2O2]0=1mM, [TiO2]0=50mg/L), UV/S2O82− was more effective for oxidizing MMA and DMA than UV/H2O2 and UV/TiO2. The oxidation rate of DMA by UV/S2O82− could be accelerated by increasing the ratio of [S2O82−]/[DMA]. The oxidation efficiencies of MMA and DMA by UV/S2O82− were lower at initial pH 7 than at initial pH 3 and 10. This phenomenon was attributable to the radical-scavenging effect of bicarbonate, which was added as a pH-buffering solute. The results shown in this study show that UV/S2O82− is an effective oxidation process for MMA and DMA.
Keywords: UV/S; 2; O; 8; 2−; UV/H; 2; O; 2; UV/TiO; 2; SO; 4; −; radical; OH; radical; Monomethylarsonic acid (MMA); Dimethylarsinic acid (DMA)
A multistage NO x reduction process for a FCC regenerator
by Jun Li; Guohua Luo; Fei Wei (pp. 296-302).
► A new NO x reduction technology for FCC regeneration process. ► NO reduction by CO under simulated FCC regeneration conditions. ► A phase diagram of the NO+O2+CO reaction system. ► Comparison of NO conversion between single-stage and two-stage regenerator. ► A multistage regenerator give a higher efficiency for NO reduction than a single stage regenerator.NO x emission from a fluid catalytic cracking (FCC) regenerator is of environmental concern. A new NO x reduction technology that comprised only a simple change in the configuration and operating condition of a commercial FCC regeneration process was proposed. NO reduction by CO in a lab scale fluidized bed reactor under simulated FCC regeneration conditions was investigated. The results indicated that a multistage regenerator would give a higher efficiency for NO reduction than a single stage regenerator. The conversion of NO was increased to 90% in a multistage regenerator as compared to 50% in a single stage regenerator under the same operation conditions. The carbon content of the regenerated catalyst was less than 0.02wt%. In the range of 400–700°C, a higher temperature gave more NO conversion to N2. The O2 and CO concentrations were crucial factors that affected the conversion of NO. The catalyst in the FCC process limits the use of the regeneration temperature to less than 700°C and mole ratio of O2/CO to less than 0.25% in the reduction stage of the regenerator. A phase diagram of the NO+O2+CO reaction was obtained that was divided into a slow reaction zone and a rapid reaction zone. The regenerator can also be used as a flue gas denitrification facility located downstream of the catalyst regenerator or a coal-burning boiler to reduce the NO concentration in the flue gas to under 20ppm.
Keywords: NO; x; FCC; Regenerator; Reduction; Multi-redox-stage
Pollution control of surface waters by coupling gliding discharge treatment with incorporated oyster shell powder
by E. Njoyim-Tamungang; S. Laminsi; P. Ghogomu; D. Njopwouo; J.-L. Brisset (pp. 303-308).
►NO,OH and derivatives form in electric discharges in air at atmospheric pressure. ► The oxidizing plasma species degrade organic wastes sampled from surface waters. ► The process is followed by BOD, COD and TOC measurements for exposures up to 30min. ► Incorporating powdered oyster shell (OS) controls acidity and hence the kinetic rate. ► Treatment time and OS mass are optimized around 36% TOC abatement within 10min.Highly oxidizing gaseous species (OH,NO and derivatives) formed in an electrical discharge (a gliding discharge burning in humid air), are suitable for abating the organic pollutant concentration of surface waters sampled in Cameroonian brooks, e.g., 47% (Total Organic Carbon, TOC) within 10min exposure. The plasma technique coupled with the use of finely powdered oyster shell (OS) acting as a catalyst and an acidity control agent thus yields improved results. This paper is devoted to determining the optimum amount m (gL−1) of incorporated OS before switching on the discharge for given exposure times t* (min). The process effects are controlled by means of pH, Biological and Chemical Oxygen Demands (BOD, COD), and Total Organic Carbon (TOC) measurements performed for various t* and m values and the results are compared with a mere plasma treatment on the same samples. The BOD5 and TOC values respectively decrease by 86% and 36% for 10min exposure with 1gL−1 incorporated OS. Treatments with OS stabilize acidity around pH: 6.5 while the pH decrease is more important without OS. BOD5 and TOC exponentially decrease with t* with or without incorporated OS, as does COD with OS only. BOD5 exponentially decreases with increasing m while COD linearly depends on t* and m, and TOC on m only. Optimized treatment parameters are t*=30min, m=0.1gL−1.
Keywords: Gliding electric discharge; Non-thermal air plasma; Industrial effluents; Domestic pollutant abatement; Wastes water degradation; Oyster shells powder
TNT oxidation by Fenton reaction: Reagent ratio effect on kinetics and early stage degradation pathways
by Kaidar Ayoub; Sylvie Nélieu; Eric D. van Hullebusch; Alessandra Maia-Grondard; Michel Cassir; Alain Bermond (pp. 309-317).
► TNT degradation by Fenton reaction at laboratory scale was investigated. ► The absolute rate constant between TNT and hydroxyl radicals was determined. ► Early stage TNT degradation by-products were identified by LC–ESI-MS/MS. ► Four intermediates never described in the literature were identified.The removal of TNT from contaminated water can be achieved through advanced oxidation treatment. In the present study, its degradation by Fenton reaction was investigated at laboratory scale. Degradation efficiencies were compared by varying Fenton's reagents concentration and ratios. The parallel monitoring of Fenton's reagents concentrations allowed evidencing hydrogen peroxide or ferrous ion contents as limiting factors for TNT removal. The absolute rate constant of the reaction between TNT and hydroxyl radicals was also determined. TNT by-products corresponding to early stage degradation were identified by LC–ESI-MS and LC–ESI-MS/MS after solid phase pre-concentration. For the first time, formation of 2,4,6-trinitro-cyclohexa-2,4-dienol (uncommon), 2,4,6-trinitrobenzylalcohol, 2,4,6-trinitro-benzaldehyde, and one of the dinitro-hydroxy-benzaldehyde isomers were evidenced. Degradation pathways involving hydroxyl radical attacks resulting in methyl group oxidation, decarboxylation, aromatic ring breakage and hydrolysis, were finally proposed.
Keywords: Advanced oxidation process; Fenton reaction; 2,4,6-trinitrotoluene; Degradation pathway; LC–MS
Studies on the effect of flocculant adsorption on the dewatering of iron ore tailings
by M. Dash; R.K. Dwari; S.K. Biswal; P.S.R. Reddy; P. Chattopadhyay; B.K. Mishra (pp. 318-325).
► Adsorption of polyacrylamide flocculants onto the iron ore tailings is established. ► Effects of pH and flocculant doses on zeta potential of the tailings were studied. ► Adsorption data was validated with Langmuir and Freundlich isotherm models. ► Flocculation and settling studies were carried out to optimize dewatering conditions. ► The investigation outcomes are directly applicable to dewatering practice in mineral industries.The adsorption characteristics of polyacrylamide polymer on iron ore tailings have been studied to understand the mechanism of adsorption. Adsorptions of both the anionic and non-ionic flocculants were analyzed using Langmuir isotherm and Freundlich isotherm. It was found that in comparison to the Langmuir model the Freundlich model was a better fit to the adsorption data according to the minimum variance criterion. It was established with the support of the Langmuir model that the adsorption of anionic and non-ionic flocculants is facilitated by hydrogen bonding. The zeta potential affects the settling rate and in this case the isoelectric point of the tailings which is basically a mixture of various oxides was measured to be 4.66. The settling rate was found to increase when the pH decreased from 10 to 5. The settling rate increased with increasing flocculant dosage up to a maximum value at 80g polymer/t solid corresponding to the maximum adsorption of polymer. However, at higher pH the clarity of supernatant liquid was very poor and flocculation was not effective for ultrafine particles at that pH.
Keywords: Iron ore tailings; Flocculation; Dewatering; Adsorption; Polyacrylamide
Adsorption of Ni2+, Zn2+ and Pb2+ onto dry biomass of Arthrospira ( Spirulina) platensis and Chlorella vulgaris. I. Single metal systems
by Lívia Seno Ferreira; Mayla Santos Rodrigues; João Carlos Monteiro de Carvalho; Alessandra Lodi; Elisabetta Finocchio; Patrizia Perego; Attilio Converti (pp. 326-333).
► A. platensis and C. vulgaris are potential biosorbents of Ni2+, Zn2+ and Pb2+. ► Pb2+ removal efficiency was 78.0% with A. platensis and 86.5% with C. vulgaris. ► Both Freundlich and Langmuir equilibrium models well described the sorption process. ► Carboxylate groups were mainly responsible for metal sorption onto cells surfaces.Adsorption of Ni2+, Zn2+ or Pb2+ by dry biomass of Arthrospira (Spirulina) platensis and Chlorella vulgaris was studied as a function of contact time and initial metal concentration. The zero point of charge calculated for these biosorbents (pHzpc 4.0 and 3.4, respectively) and additional pH tests suggested the use of pH in the range 5.0–5.5 for the experiments. The equilibrium isotherms were evaluated in terms of maximum sorption capacity and sorption affinity. The pseudo first and second order kinetic models were considered to interpret the experimental data, and the latter best described the adsorption system. Both the Freundlich and Langmuir models were shown to well describe the sorption isotherms, thus suggesting an intermediate mono/multilayer sorption mechanism. Compared to A. platensis ( q e=0.354, 0.495 and 0.508mmolg−1 for Ni2+, Pb2+ and Zn2+, respectively), C. vulgaris behaved as a better biosorbent because of higher equilibrium sorption capacity ( q e=0.499, 0.634 and 0.664mmolg−1, respectively). The removal efficiency decreased with increasing metal concentration, pointing out a passive adsorption process involving the active sites on the surface of the biomasses. The FT-IR spectroscopy evidenced that ions removal occurred mainly by interaction between metal and carboxylate groups present on both the cell walls.
Keywords: Heavy metals sorption; Arthrospira (Spirulina) platensis; Chlorella vulgaris; Kinetics; Isotherms; FT-IR spectroscopy
Removal of textile dyes from aqueous solution by babassu coconut epicarp ( Orbignya speciosa)
by Adriana P. Vieira; Sirlane A.A. Santana; Cícero W.B. Bezerra; Hildo A.S. Silva; José A.P. Chaves; Júlio C.P. Melo; Edson C. Silva Filho; Claudio Airoldi (pp. 334-340).
► Babassu coconut ( Orbignya speciosa) epicarp as biomass to remove textile dyes. ► The effects of contact time and concentration were investigated. ► Equilibrium between the dyes in the solution and epicarp was achieved in until 60min. ► The equilibrium data showing physical interactions between the species.Babassu coconut ( Orbignya speciosa) epicarp (BCE) was used as biomass to remove textile dyes from aqueous solution. Physical characteristics of the BCE were investigated using infrared spectroscopy (IR), point of zero charge (p Hpzc), surface area, pore volume and diameter. A batch system was applied to study the sorption of Blue Remazol R160 (BR 160), Rubi S2G (R S2G), Red Remazol 5R (RR 5), Violet Remazol 5R (VR 5) and Indanthrene Olive Green (IOG) dye solutions by BCE. The effects of contact time and concentration on the sorption of the textile dyes onto the BCE were investigated. The interactions were assayed with respect to the pseudo-first-order, pseudo-second-order and the Elovich kinetic models by linear and non-linear regression methods, and were found to follow closely the pseudo-second-order. The ability of babassu coconut epicarp to sorb dyes gave the ordered set BR 160>VR 5>RR 5>R S2G>IOG. Equilibrium data also were fitted by linear and non-linear regression methods through the Langmuir, the Freundlich, the Temkin and the Dubinin–Radushkevich isotherm models. The equilibrium data were best represented by the Dubinin–Radushkevich, showing physical interactions between the species.
Keywords: Abbreviations; BCE; babassu coconut epicarp; C; i; initial dye concentration (mg; dm; −3; ); C; f; equilibrium dye concentration (mg; dm; −3; ); E; mean energy of Dubinin–Radushkevich (kJ; mol; −1; ); F; error; average percentage error (%); H; initial rate of sorption (mmol; g; −1; min; −1; ); k; f; rate constant of the pseudo-first-order model (min; −1; ); k; s; rate constant of the pseudo-second-order model (g; mmol; −1; min; −1; ); K; F; Freundlich constant representing sorption capacity (mmol; g; −1; (dm; 3; mmol; −1; ); 1/; n; ); K; L; Langmuir constant related to the apparent energy of sorption (dm; 3; mmol; −1; ); K; T; equilibrium constant corresponding to the maximum bonding energy (dm; 3; g; −1; ); K; DR; equilibrium constant of Dubinin–Radushkevich model (mol; 2; kJ; −2; ); M; mass of the sorbent (g); N; Freundlich constant; P; number of experimental data points; q; m; maximum sorption capacity of the sorbents (mg; g; −1; ); q; t; amount of dye sorbed at time; t; (mg; g; −1; ); q; e; amount sorbed at equilibrium (mg; g; −1; ); T; contact time (min); V; volume of the solution (dm; 3; ); A; initial sorption rate (mg; g; −1; min; −1; ) of Elovich equation; B; Elovich constant related to the extent of surface coverage and also to the activation energy involved in chemisorption (g; mg; −1; ); β; T; Temkin constant related to heat of sorption (J; mol; −1; ); χ; 2; Chi-squareBabassu coconut epicarp; Sorption; Low-cost sorbents; Dye removal
A new material for airborne virus filtration
by G. Tiliket; D. Le Sage; V. Moules; M. Rosa-Calatrava; B. Lina; J.M. Valleton; Q.T. Nguyen; L. Lebrun (pp. 341-351).
► In this study we modify the surface of low-cost filters by fixing poly(ethylenimine) (PEI) to give them an antiviral property. ► Two layers of Kimwipes® functionalized with PEI give the best virus retention. ► Two layers of Kimwipes® functionalized with PEI placed inside a commercial medical mask strongly improve the virus retention. ► The new medical mask with additional antiviral properties represents a significant improvement over conventional medical masksOnly facepiece respirators of FFP2 or FFP3 type by European standards (N95 by US standards) can provide effective protection against airborne viruses. However, these respirators are expensive and many third-world countries would be unable to afford them if a severe pandemic starts. The present study reports a chemical modification of the surface of low-cost non-woven cellulosic fiber filters by fixing poly(ethylenimine) (PEI) in order to give them an antiviral property. The virus filtration experiments were performed by spraying an aerial suspension of T4D bacteriophage virus of Escherichia coli B through the filter. The coating of the non-woven fiber by the antiviral entity was optimized. The best virus capture factor f (ratio of mother-solution virus content to downstream virus content) was obtained with 2 layers of Kimwipes® functionalized with a PEI solution (4.4% w/v) ( f=3×105). When these 2 layers were placed inside a commercial medical mask in place of its cellulosic layer (Kolmi M24001 mask) ( f=3.5×104), the f ratio reached 1.8×10,7for 1h of filtration. This novel medical mask with additional antiviral properties represents a significant improvement over conventional medical masks. The system was also tested with respect to the respiratory low pathogenic A (H5N2) influenza virus. No virus was detected on the downstream side of the filters during the filtration. Moreover, the system captured alive the virus making possible applications to pre-concentration of airborne viruses for medical tests or research experiments.
Keywords: Virus; Filter; Non-woven material; Mask; Poly(ethylenimine)
Cu(II) transport through soybean oil-based bulk liquid membrane: Kinetic study
by Siu Hua Chang; Tjoon Tow Teng; Ismail Norli (pp. 352-360).
► Cu(II) transport in soybean oil-based BLM was governed by the stripping process. ► Cu(II) extraction process in soybean oil-based BLM was diffusion-controlled. ► Cu(II) stripping process in soybean oil-based BLM was chemical reaction-controlled. ► Cu(II) transport rates were similar for both soybean oil- and kerosene-based BLMs. ► Cu(II) transport in soybean oil-based BLM was unaffected by use of real wastewater.Kinetic study of Cu(II) transport through a soybean oil-based bulk liquid membrane (BLM) containing di-2-ethylhexylphosphoric acid (carrier) and tributylphosphate (phase modifier) diluted in soybean oil (diluent) was conducted. Effects of initial Cu(II) concentration in the feed phase and temperature were investigated and their kinetic parameters were determined from the kinetic models of two consecutive irreversible first-order reactions. Various initial Cu(II) concentrations in the feed phase (50–500mg/L (0.788–7.88mM)) and temperatures (27–43°C) were found not to affect the rate of extraction process significantly, but enhanced the rate of stripping process with decreasing initial Cu(II) concentration in the feed phase and increasing temperature. The rate-controlling steps of both extraction (diffusion-controlled) and stripping (chemical reaction-controlled) processes were determined and a plausible transport mechanism was proposed. The kinetics of Cu(II) transport through soybean oil-based BLM was then compared with that of a similar kerosene-based BLM and their extraction ( k1) and stripping ( k2) rate constants (soybean oil-based BLM: k1=1.94h−1, k2=0.11h−1; kerosene-based BLM: k1=1.73h−1, k2=0.13h−1) were determined. Application of soybean oil-based BLM in real industrial wastewater was also studied.
Keywords: Cu(II); Transport; Soybean oil; Bulk liquid membrane; Kinetic
Bentazon and carbofuran adsorption onto date seed activated carbon: Kinetics and equilibrium
by J.M. Salman; V.O. Njoku; B.H. Hameed (pp. 361-368).
► Date seed activated carbon (DSAC) was prepared by activation using KOH and CO2. ► DSAC was characterized by surface characteristics, SEM and FTIR spectroscopy. ► DSAC was used in the removal of bentazon and carbofuran from aqueous solutions. ► Kinetic and isotherm models were used to interpret adsorption mechanisms. ► The adsorption capacities of DSAC for bentazon and carbofuran were compared.Date seed (DS), an abundant and inexpensive natural resource in Iraq, was used to prepare DS activated carbon (DSAC) by physiochemical activation with potassium hydroxide (KOH) and carbon dioxide (CO2) as the activating agents at 850°C for 3h and 37min. The adsorption kinetics and equilibrium of bentazon and carbofuran onto DSAC were examined in batch process. Adsorption studies were conducted in the pesticides initial concentration range of 25–250mg/L, temperature of 30°C and pH of 5.5. The pH studies were undertaken in the pH range 2–12. The adsorption kinetic data were analyzed by non-linear fitting using the pseudo-first-order and pseudo-second-order models. The adsorption of bentazon and carbofuran was better described by the pseudo-second-order equation. The experimental equilibrium data were analyzed by non-linear fitting using Langmuir and Freundlich isotherm models. Equilibrium data fitted better with the Freundlich model for both pesticides. DSAC showed higher adsorption in the case of carbofuran than for bentazon. Desorption of the used DSAC was studied using ethanol as solvent and percent desorption efficiencies of 84.1 and 82.2% were obtained after three cycles for bentazon and carbofuran, respectively. The high adsorption capacity of DSAC obtained for both pesticides showed that DS is a good precursor for the preparation of activated carbon for the adsorptive removal of bentazon and carbofuran.
Keywords: Desorption; Functional groups; Isotherms; Pesticides
Photocatalytic degradation of 2,4-dichlorophenoxyacetic acid by Ca–Ce–W–TiO2 composite photocatalyst
by U.G. Akpan; B.H. Hameed (pp. 369-375).
► Development of Ca–Ce–W–TiO2 composite by sol–gel and hydro-treated at 200°C for 8h. ► The composite catalyst was used in degradation of 2,4-D and was very effective. ► First order kinetic was obtained for the degradation. ► The process did not obey Langmuir–Hinshelwood kinetic model. ► The ratio of adsorption to reaction is in the order of 1:287.A Ca–Ce–W–TiO2 composite photocatalyst has been developed which was efficient in the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The adsorption rate constant obtained from the Langmuir–Hinshelwood kinetic model was in the order of 1:287:adsorption:reaction, which is so negligible. This is an indication that the process did not obey the Langmuir–Hinshelwood kinetic model. Therefore, the degradation recorded in this study was as a result of the properties of the composite photocatalyst. Large specific surface area, reduced band gap which also inhibited electron–hole recombination, high crystallinity of the composite photocatalyst were responsible for its efficiency. The photocatalytic process in this study is best described by the first order irreversible reaction rate/order. A comparison of the efficiency of the photocatalyst with a commercially available photocatalyst, TiO2–Sigma product and other photocatalysts in literature placed the composite photocatalyst at an excellent position above the commercial and others available in literature for the degradation of 2,4-D. Within the limits of the experiment, the amount of 2,4-D degraded per unit time was found to be proportional to its initial concentrations, and the unadjusted solution pH 4.232 was found to be the best for the process.
Keywords: Kinetic; 2,4-D; Degradation; Composite photocatalyst; Band gap
The impacts of coagulant aid-polydimethyldiallylammonium chloride on coagulation performances and floc characteristics in humic acid–kaolin synthetic water treatment with titanium tetrachloride
by Y.X. Zhao; B.Y. Gao; H.Y. Rong; H.K. Shon; J.-H. Kim; Q.Y. Yue; Y. Wang (pp. 376-384).
► HA removal was enhanced by PD, PD–TiCl4 performed better than TiCl4–PD. ► TiCl4 plus PD exhibited an apparent improvement on floc size and floc grow rate. ► The dual-coagulants significantly improved the floc recoverability. ► The dual-coagulants gave more compact floc structure than TiCl4 coagulant.Coagulation of humic acid–kaolin synthetic water was conducted with Titanium tetrachloride (TiCl4) and/or polydimethyldiallylammonium chloride (PD) to assess the effect of coagulant aid PD on coagulation behavior and floc characteristics. Coagulation behavior was investigated in terms of the reduction of turbidity and the removal of natural organic matter (NOM). The results show that the humic acid (HA) removal increased with the addition of PD depending on the doses of it and TiCl4, and the HA removal was more enhanced by PD at low TiCl4 doses than at higher ones. In addition, PD–TiCl4 (PD dosed firstly, followed by TiCl4 addition) gave better turbidity and HA removal than TiCl4–PD (TiCl4 dosed firstly, followed by PD addition) in this investigation. The growth, breakage, regrowth and fractal nature of flocs was investigated by use of Mastersizer 2000. TiCl4 plus cationic polymer PD exhibited an apparent improvement on floc size and floc grow rate, and they were both in the following order: PD–TiCl4>TiCl4–PD>TiCl4. Compared with TiCl4, the dual-coagulants significantly improved the floc recoverability. Besides, the dual-coagulants gave more compact floc structure than TiCl4 coagulant at each coagulant dose under investigation and the values of fractal dimension ( Df) were in the order of TiCl4–PD>PD–TiCl4>TiCl4.
Keywords: Titanium tetrachloride; Polydimethyldiallylammonium chloride; Fractal dimension; Floc strength; Floc regrowth
Microwave assisted preparation of activated carbon from pomelo skin for the removal of anionic and cationic dyes
by K.Y. Foo; B.H. Hameed (pp. 385-390).
► Highlight the renewable use of pomelo skin. ► Activation time of 5min at the microwave input power of 800W. ► High BET and Langmuir surface area of 1335 and 2057m2/g. ► A comparison of linear and non-linear isotherm models was elucidated. ► High monolayer adsorption capacity for both anionic and cationic dyes.In this work, pomelo skin, an industrial effluent abundantly available from the fruit juice processing plants, was utilized as a feedstock for preparation of activated carbon (PSAC) via microwave induced NaOH activation. The activation process was performed at the input power of 800W and irradiation time of 5min. The porosity, functional and surface chemistry were featured by means of low temperature nitrogen adsorption, elemental analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and evaluation of surface acidity/basicity. The adsorptive property of PSAC was tested using methylene blue and acid blue 15 dyes as the model adsorbates. Equilibrium data was examined using a comparison of linear and non-linear isotherm models. The adsorption behavior was well described by the non-linear Langmuir isotherm model, showing a monolayer adsorption capacity for methylene blue and acid blue 15 of 501.10mg/g and 444.45mg/g, respectively. The findings revealed the potential use of pomelo skin derived activated carbon for removal of cationic and anionic dyes.
Keywords: Acid blue; Activated carbon; Adsorption; Methylene blue; Microwave; Pomelo skin
Preparation and characterization of activated carbon from corncob by chemical activation with H3PO4 for 2,4-dichlorophenoxyacetic acid adsorption
by V.O. Njoku; B.H. Hameed (pp. 391-399).
► Corncob was a suitable precursor for the production of activated carbon. ► The corncob activated carbon (CCAC) was produced by chemical activation with H3PO4. ► High percent removal of 2,4-D from aqueous solutions was obtained with CCAC. ► Kinetic and isotherm models were used to interpret adsorption mechanisms. ► The adsorption was found to be spontaneous and endothermic in nature. ► A diffusion-controlled process indicating physisorption mechanism was inferred.Corncob activated carbon (CCAC) was prepared and its ability to remove 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions was studied. The BET surface area, Langmuir surface area and cumulative pore volume of CCAC were 1273.91m/g, 2010.12m2/g and 0.900cm3/g, respectively. The adsorption kinetics was best represented by the pseudo-second-order model. The superiority of the Freundlich isotherm model in describing the equilibrium adsorption data was shown by the adjusted correlation coefficients ( R2adj) and root-mean squared error (RMSE) values. High percent removal of 69.10, 69.58 and 73.86% were achieved for 2,4-D initial concentration of 400mg/L at 30, 40 and 50°C, respectively. Activation energy, E a for the adsorption was determined to be 39.87kJ/mol and a diffusion-controlled process indicating physisorption mechanism was proposed. From the thermodynamic parameters determined, the adsorption was found to be spontaneous and endothermic in nature. Intraparticle diffusion and Boyd kinetic models confirmed film diffusion as the rate-controlling step. A single-stage batch adsorber was designed to obtain the mass of CCAC required to achieve desired percent removal of 2,4-D from effluent solutions of different volumes using the Freundlich equation.
Keywords: 2,4-; D; Chemical activation; Isotherm; Pesticide; Equilibrium
Coagulation performance and floc properties of compound bioflocculant-aluminum sulfate dual-coagulant in treating kaolin-humic acid solution
by Xiaowen Bo; Baoyu Gao; Nana Peng; Yan Wang; Qinyan Yue; Yingcan Zhao (pp. 400-406).
► AS-CBF, CBF-AS and AS were comparatively investigated in synthetic water treatment. ► Compared with AS, AS-CBF and CBF-AS enhanced the coagulation efficiency. ► The addition of CBF showed obvious positive effect on floc growth rate and size. ► Flocs formed by AS-CBF showed the largest strength and the best recoverability. ► Coagulation with AS-CBF was achieved by the combination of charge neutralization and bridging.The coagulation performance and floc properties of compound bioflocculant (CBF)-aluminum sulfate (AS) dual-coagulant were compared with that of AS in the treatment of synthetic kaolin-humic (HA) water. Results showed that AS-CBF dual coagulant was more efficient for HA removal. The floc formation, breakage and reformation were investigated under different dosages and shear rates. Increasing coagulant dosage resulted in the increase of floc growth rate and size. But the floc recoverability was found to decrease with increasing coagulant dosage. Furthermore, flocs formed by AS-CBF (AS dosed firstly) had faster growth rate, larger size and better recoverability than AS and CBF-AS (CBF dosed firstly) in the dosage range investigated. Similar results were obtained when the shear force was changed. Precipitate charge neutralization was a dominant mechanism of AS, and CBF had good adsorption bridging effect. Due to the combination of two advantages, coagulation efficiency could be enhanced significantly.
Keywords: Compound bioflocculant; Dual-coagulant; Floc formation; Floc strength; Floc regrowth
Deep H2S removal from biogas for molten carbonate fuel cell (MCFC) systems
by Giulia Monteleone; Massimo De Francesco; Stefano Galli; Marcello Marchetti; Valentina Naticchioni (pp. 407-414).
.Display Omitted► Basicity of impregnated active carbon enhances adsorption capacity. ► Microporous component of carbon has the crucial role in H2S adsorption. ► CO2 did not affect adsorption capacity of specific activated carbon as AC1. ► Activated carbon impregnated with metals can achieve fuel cell purity requirements.The growing attention on efficient and sustainable energy technologies and the use of renewable sources promoted many researches on green technologies. Among them, the molten carbonate fuel cells (MCFCs) are attractive for their possibility to be supplied by biogas . Biogas contains up to 70% of methane, 30–40% of carbon dioxide and contaminants like sulphur compounds, siloxanes and halogenated organic compounds. The most harmful for environment and equipments is the hydrogen sulphide (H2S). In MCFCs applications H2S poisons both the reformer and the electrodes catalysts of the fuel cell reacting with nickel. Consequently, the biogas should be purified and H2S fraction reduced to the MCFCs tolerance limit (<0.5ppm) to allow its safe use.The presented activities are focused on H2S adsorptive abatement using commercial adsorbents under anaerobic conditions. The present work provides information on nature of the anaerobic H2S adsorption on activated carbons, the influence of thermal treatment on adsorption capacity, the feasibility of regeneration and the competitive adsorption of H2S and CO2.The selected materials were characterized before and after adsorption tests, using the following techniques: sorption of nitrogen, XRPD, TGA–DTA, SEM and EDX.All tested carbons showed a better adsorption capacity before thermal treatment, confirming the crucial role of water in absorption mechanism. Alkaline carbons confirm low adsorption capacity and selectivity in H2S adsorption when CO2 is present. Activated carbon impregnated with metal salts, revealed the highest adsorption capacity due to the combination of microporosity and oxidative properties, matching the MCFCs requirements.
Keywords: Biogas; Desulphurization; Hydrogen sulphide; Activated carbons; Breakthrough curves; Co-adsorption
Base-catalyzed destruction of hexachlorobenzene with zero-valent iron
by Xiao Ye; Jiang Jianguo; Yang Yong; Gao Guolong (pp. 415-421).
► Decomposition of HCB with zero-valent iron was investigated with a BCD reactor. ► The dechlorination efficiency of HCB improved with the addition of zero-valent iron. ► The removal of HCB achieved almost 100% at the best condition. ► The HCB dechlorination pathway were examined and discussed. ► The present study is significant for the disposal of POPs waste.The dechlorination pathways and detoxification mechanism of base-catalyzed decomposition (BCD) of hexachlorobenzene (HCB) with zero-valent iron were investigated. Results showed that HCB was effectively destructed using the BCD technology. The thorough dechlorination efficiencies of HCB (HDEs) improved with increasing reaction time and the addition of zero-valent iron. HCB remaining in the reaction system was almost 100% removed, and HDE reached 93% after 4h at 360°C with a zero-valent iron catalyst. The chlorinated intermediates contained pentachlorobenzene (PeCB), three tetrachlorobenzene (TeCB) isomers, three trichlorobenzene (TCB) isomers, three dichlorobenzene (DCB) isomers, and monochlorobenzene (MCB). The base-catalyzed dechlorination of HCB was observed as a stepwise dechlorination process. The main dechlorination pathway for HCB was proposed as HCB→PeCB→1,2,3,5-TeCB→1,2,4-TCB→1,2-DCB→MCB. The residual HCB and chlorobenzenes were mainly distributed in the condensate and active carbon. Chlorobenzenes made up only 0.02% and 0.04% of the paraffin oil and residues, respectively. The innocuous treatment should be further considered for these trace amounts of chlorinated intermediate products.
Keywords: Base-catalyzed decomposition; Dechlorination; HCB; Zero-valent iron
Biosorption of lead from aqueous solutions by Bacillus strains possessing heavy-metal resistance
by Ferdağ Çolak; Necip Atar; Demet Yazıcıoğlu; Asim Olgun (pp. 422-428).
► The biosorption capacity and heavy metal tolerance of Bacillus cereus and Bacillus pumilus. ► Biosorption of Pb2+ from aqueous solution. ► The Langmuir isotherm model and Thomas model fit well with the experimental results. ► Kinetic aspect of lead biosorption.In this study, bacterial strains were investigated in order to determine their heavy metal tolerance. The bacterial strains were identified as Bacillus cereus and Bacillus pumilus. In the batch system, the effects of operating variables such as solution pH, initial metal concentration, contact time, and adsorbent dosage were investigated. Both isolates were highly resistance to copper and lead in comparison with the control strain examined. The adsorption capacities of B. cereus and B. pumilus were found to be 22.1mg/g and 28.06mg/g, respectively. The biosorption follows pseudo-second order kinetics and the isotherm fits well to the Langmuir isotherm model. In column experiments, the biosorption was fitted well by the Thomas model. The breakthrough and exhaustion capacity of each biosorbent decreased with increasing flow rate. In the fixed-bed system, the biosorption capacities of, B. cereus and B. pumilus were observed to be higher than that of the batch system.
Keywords: Biosorption; Heavy metal resistance; Bacillus cereus; Bacillus pumilus; Lead
Removal of methylene blue from aqueous solutions by straw based adsorbent in a fixed-bed column
by Wenxuan Zhang; Lei Dong; Han Yan; Haijiang Li; Ziwen Jiang; Xiaowei Kan; Hu Yang; Aimin Li; Rongshi Cheng (pp. 429-436).
► Applications of carboxymethyl straw adsorbent in the removal of methylene blue in a fixed-bed column. ► Investigation of the effects of various factors on the column adsorption. ► Study on the adsorption mechanisms by various theoretic models. ► The adsorption behaviors obeying the monolayer chemical adsorption mechanisms.In this paper, carboxymethyl straw has been applied to eliminate methylene blue (MB) in a fixed-bed column. The straw based adsorbent has shown high MB uptake in column. Various models such as Thomas, Clark, Adams–Bohart, Yoon–Nelson, Wolborska, and BDST model have been employed to fit the experimental data carefully. Among them, Thomas model is found to be the most suitable one to describe the adsorption behaviors, according with the monolayer chemical adsorption mechanism. Then the effects of initial solution pH, bed height, temperature, initial MB concentration and flow rate on column adsorption have been studied in detail based on Thomas model. It has been found that initial solution pH, bed height, initial MB concentration and flow rate can affect the breakthrough curves obviously, while temperature has no evident influence on the MB adsorption of the modified straw.
Keywords: Modified straw adsorbent; Adsorption of methylene blue; Column study; Thomas model
Indirect CO2 mineral sequestration by steelmaking slag with NH4Cl as leaching solution
by Yong Sun; Ming-Shun Yao; Jing-Ping Zhang; Gang Yang (pp. 437-445).
► The steelmaking slag leached by NH4Cl was employed for CO2 mineral sequestration. ► We explore effects of operational conditions upon carbonation. ► Kinetics of a diffusion determined core-shrinking reaction was modeled. ► Increasing temperature favors formation of crystal with rhombohedral morphology.The steelmaking slag (SL) is used for indirect CO2 mineral sequestration. The optimized carbonation conditions include: initial pressure 10bar, 60°C, 400rpm/min, 60min duration. The high purity (96±2wt%) calcium carbonate is obtained under the optimized carbonation condition. The crystallite magnesium carbonate together with other impurities such as aluminum oxide, ferrous oxide, silica oxide, also exists in the precipitate with composition percentage below 2wt%. The characterization of the obtained precipitates at different temperatures by SEM shows the gradual morphological changes from scalenohedral to rhombohedral crystal with increase of carbonation temperature (within 20–80°C). The kinetic shows a fast reaction rate with 11.8kJ/mol apparent activation energy, indicating a diffusion determined core-shrinking reaction during carbonation. The CO2 capture capacity was compared to different sequestration routes using different industrial wastes. The maximum capacity from our experimental result could reach 211kg CO2/ton SL with the contribution of CaCO3/MgCO3 together with Mg(HCO3)2 in capturing CO2.
Keywords: Steelmaking slag; Mineralization; CO; 2; sequestration
Preparation of novel spherical PVA/ATP composites with macroreticular structure and their adsorption behavior for methylene blue and lead in aqueous solution
by Liuqing Yang; Yanfeng Li; Huaiyuan Hu; Xinliang Jin; Zhengfang Ye; Yingxia Ma; Sidi Zhang (pp. 446-455).
► A novel spherical PVA/ATP nano-composite material with macroreticular structure was prepared firstly. ► Different from the major studies of ATP focusing on graft modification, it holds the advantages of PVA and ATP in the same time. ► By introducing macro-reticular structure, it shows good mass transfer performance. ► The resulting adsorbent has been proved with easy separation and excellent adsorption for methylene blue and lead in aqueous solution. ► With simultaneously adsorbing dyes and heavy metal, it could reduce the energy consumption and cost both in preparation and application.A novel spherical composite of polyvinyl alcohol (PVA) and attapulgite (ATP) with macroreticular structure, i.e. MR-PVA/ATP composites, was prepared as an adsorbent for some contaminations from aqueous environment, which would hold the advantages of PVA and ATP in the same time. The resulting adsorbents hold uniform and rich aperture with good mass transfer property, processing properties and stability. It has been proved with easy separation and excellent adsorption for methylene blue and lead in aqueous solution, and the adsorption rate will be accelerated when increasing porogen in its preparation. The adsorption process of methylene blue and lead on it includes both chemo-adsorption and physical adsorption. The adsorption process all fits the pseudo second order kinetics very well with rapid initial adsorption rate. The addition of attapulgite increased the adsorption capacity of lead ions significantly. By further graft functional groups on the ATP, it has potential to prepare various adsorbents to satisfy specific requirements. Such kind of adsorption material will perform a wide application prospect in the purification treatment for wastewater.
Keywords: PVA; Attapulgite; Composite; Dyes adsorption; Heavy metal removal
Adsorption dynamics of toluene in composite bed with microfibrous entrapped activated carbon
by Jian Liu; Ying Yan; Huiping Zhang (pp. 456-462).
► The microfibrous entrapped activated carbon composites with high adsorption rate were prepared. ► The breakthrough time of toluene in the composite bed clearly increased compared with that of the fixed bed. ► The adsorption rate constant of the composite bed increased compared with that of the fixed bed. ► The length of unused bed (LUB) of the composite bed significantly decreased compared with that of the fixed bed.Stainless steel microfibrous entrapped activated carbon composites were prepared by wet layup papermaking and sintering process. The composite beds were filled with granular activated carbons and microfibrous composites in the inlet and outlet of the fixed bed, respectively. The adsorption breakthrough curves of toluene in the composite bed were measured, and compared with that in the fixed bed with granular activated carbons (GAC) alone. The effects of different operation parameters such as flow rate, bed height and inlet concentration on the breakthrough curves of toluene in the composite bed were investigated. The length of unused bed (LUB) was determined by analysis of the breakthrough curves. The experimental results showed that the breakthrough time of toluene in the composite bed increased 15min compared with that in the individual GAC bed at the same volume. The breakthrough time increased with decrease in both flow rate and inlet concentration but increased with increase in bed height. The LUB values were 1.59 and 1.14cm for 5cm individual GAC bed and composite bed, respectively. The LUB values increased with increase in both flow rate and inlet concentration. The experimental data were fitted to two fixed bed adsorption models namely, Yoon–Nelson and Bed Depth Service Time (BDST) models. The results fitted well to Yoon–Nelson model and the rate constant ( k′) values computed using Yoon–Nelson model were 0.1 and 0.151 for the individual GAC bed and composite bed, respectively. Also BDST model was found to show good agreement with the experimental results and the adsorption capacity ( N0) values calculated using BDST model were 175.47 and 182.19g/L for the individual GAC bed and composite bed, respectively.
Keywords: Microfibrous composite; Activated carbon; Composite bed; Toluene; Adsorption dynamics
Kinetics of the ozone oxidation of Reactive Orange 16 azo-dye in aqueous solution
by Chedly Tizaoui; Naser Grima (pp. 463-473).
► RO16 azo-dye is difficult to biodegrade and may present environmental and health concerns. ► The effect of the operating parameters on RO16 degradation was studied. ► Ozone was effective to degrade RO16 and the rate constant increased with increasing pH. ► The kinetic data were determined and a degradation pathway was proposed.Reactive azo-dyes present environmental concerns since they are persistent organics which are difficult to remove with conventional treatment processes. In this study, the ozonation of Reactive Orange 16 dye, C.I. 177757 (synonym Remazol Brilliant Orange 3R) was investigated at different experimental conditions in a semi-batch ozone reactor (25–100mg/L dye; 20–80g/m3 NTP O3 gas (NTP: 0°C and 1atm); pH 2, 7, 11). Ozone was very effective to remove completely the colour within a short period of time (few minutes). High gas-phase ozone concentrations and low dye concentrations resulted in high decolourisation rates. The decolourisation of the dye has also improved as pH increased from 2 to 11. Direct ozone reactions are assumed to predominate and hydroxyl radicals formed as a result of ozone decomposition at high pH reacted mostly with the products of the main decolourisation reaction. The reaction was assumed second order and Danckwerts model was used to determine the values of its rate constant, k2, at different pHs. Values of k2 were 2.5×105, 3.2×105, and 1.4×106L/mols for pH values of 2, 7, and 11, respectively. The stoichiometric ratio of the reaction was found equal to 3mol O3/mol dye and a degradation pathway was proposed.
Keywords: Ozone; Reactive Orange 16; Gas–liquid reaction; Danckwerts model; Mass transfer
Desorption of β-carotene from mesoporous carbon coated monolith: Isotherm, kinetics and regeneration studies
by Muhammad; Moonis Ali Khan; Thomas S.Y. Choong; T.G. Chuah; Robiah Yunus; Y.H. Taufiq Yap (pp. 474-479).
► β-carotene recovery studies form mesoporous carbon coated monolith (MCCM) were carried out by batch process. ► Desorption kinetics, equilibrium and regeneration of MCCM were studied. ► Homogeneous sites over the surface were actively involved in desorption. ► Desorption process is endothermic and diffusion might occur through micropores. ► For chemical and thermal processes, regeneration efficiency (RE%) after three consecutive cycles reduced to 60.04% and 81.62%, respectively.β-carotene, a natural antioxidant, beneficial form human health prospective. In this study we had examined the recovery of β-carotene form mesoporous carbon coated monolith (MCCM) by batch process. Desorption kinetics and isotherm studies were carried out by using n-hexane as an eluent. Isotherm studies showed better applicability of Langmuir model. The first-order two-compartment three-parameter kinetics model as a function of initial loading concentration and reaction temperature was applied. It was observed that β-carotene desorption process is controlled by both rapid and slow desorption. Results showed that the slow desorption fraction increases from 0.8446 to 0.9007 with increase in initial loading concentration from 10.83 to 39.72mg/g while, the slow desorption fraction decreases from 0.9261 to 0.8684 with increase in reaction temperature form 30 to 50°C. The activation energies for rapid and slow desorption were 7.88 and 44.47kJ/mol, respectively. The regeneration studies were carried out by both chemical and thermal process. The regeneration efficiency (RE%) for the three consecutive cycles reduced from 96.24 to 60.04% and 94.51 to 81.62% for chemical and thermal regeneration processes, respectively.
Keywords: Mesoporous carbon coated monolith; β-carotene; Desorption; Regeneration
Removal of hexavalent chromium in aquatic solutions by iron nanoparticles embedded in orange peel pith
by Gustavo López-Téllez; Carlos E. Barrera-Díaz; Patricia Balderas-Hernández; Gabriela Roa-Morales; Bryan Bilyeu (pp. 480-485).
► An iron nanoparticles in orange peel pith biocomposite is an effective Cr(VI) sorbent. ► The biocomposite removes 71% of Cr(VI) from a 10mg/L solution vs. 34% for unmodified biomass. ► The biocomposite has a Cr(VI) capacity of 5.37mg/g vs. 1.90mg/g for unmodified biomass. ► The two-step adsorption involves reduction of Cr(VI) by Fe then adsorption of the Cr(III). ► The biocomposite is economical, easy to synthesize, environment friendly, and effective.The aim of this work was to create a biocomposite which coupled the reducing capability of iron nanoparticles with the adsorption capacity of cellulose to effectively remove hexavalent chromium from industrial wastewater. The iron nanoparticles were synthesized on the orange peel pith using a simple redox precipitation reaction to ensure the biocomposite was inexpensive and easy to produce. The nanoparticles were characterized for size, composition, oxidation state, and distribution before and after the Cr(VI) exposure. The nanoparticles were mostly 20×80nm tubular shapes, but there were also some octahedral crystals around 20–40nm. The biocomposite with the nanoparticles exhibited twice the Cr(VI) removal of the unmodified orange peel pith and also possesses over twice the adsorption capacity −5.37mg/g vs. 1.90mg/g.
Keywords: Iron oxide nanoparticles; Orange peel; Chromium removal
Solution-phase adsorption of 1-pyrenebutyric acid using single-wall carbon nanotubes
by Reginald E. Rogers; Travis I. Bardsley; Steven J. Weinstein; Brian J. Landi (pp. 486-493).
► Adsorption capacity found to be 0.27mg PBA/mg SWCNT; highest capacity for polyaromatic compounds to date. ► Mass transport model developed to correlate product of the mass transfer coefficient and specific surface area (0.0066mL/mgmin). ► Proper preparation and handling of SWCNTs critical for achieving maximum adsorption capacity given variations in environmental settings.The time-dependent adsorption of 1-pyrenebutyric acid (PBA) from an aqueous solution onto single-wall carbon nanotubes (SWCNTs) is analyzed experimentally based upon relative changes in optical absorption spectra for PBA and modeled on the basis of mass transport theory. A linear dependence at short time (≤3h) is observed for PBA adsorption onto SWCNTs as a function of PBA concentration and solution temperature between 20 and 70°C. Equilibrium data after 78 days obeys a Langmuir isotherm, and suggests strongly favorable adsorption of PBA onto SWCNTs at low solution concentrations (<1μg/mL) with a maximum adsorption of 0.27mg PBA/mg SWCNT, the highest reported amount for a chemical species and SWCNTs to date. A mass transport model is also developed to correlate the experimental results into physical parameters, including the product of the mass transfer coefficient, K, and the specific surface area of SWCNTs, Ŝ, which equals 0.0066mL/mgmin at 20°C. This approach is coupled with the adsorption measurements as a function of temperature to determine the Arrhenius activation energy for the PBA–SWCNT system, which equals 20.3kJ/mol and is consistent with a physisorption process. The model and experiments combine to fully describe the kinetic response of PBA onto SWCNTs from an aqueous solution and demonstrate the utility of this framework in studying adsorption applications for SWCNTs with organic compounds.
Keywords: Batch adsorption; Carbon nanotubes; 1-Pyrenebutyric acid; Physisorption process
Adsorption removal of congo red onto magnetic cellulose/Fe3O4/activated carbon composite: Equilibrium, kinetic and thermodynamic studies
by H.-Y. Zhu; Y.-Q. Fu; R. Jiang; J.-H. Jiang; L. Xiao; G.-M. Zeng; S.-L. Zhao; Y. Wang (pp. 494-502).
► The m-Cell/Fe3O4/ACCs prepared showed the characteristics of superparamagnetism. ► The m-Cell/Fe3O4/ACCs could be separated from the treated solution by a magnetic process. ► The thermodynamic analysis indicated an exothermic nature and a spontaneous and favorable process for congo red adsorption onto m-Cell/Fe3O4/ACCs. ► The m-Cell/Fe3O4/ACCs might be a promising candidate of high efficiency, low cost, and convenient separation under magnetic field.Magnetic cellulose/Fe3O4/activated carbon composites (m-Cell/Fe3O4/ACCs) were prepared successfully and characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The adsorption of congo red onto the novel m-Cell/Fe3O4/ACCs was studied as a function of contact time, initial concentration of congo red, adsorbent dosage, and pH of solution. The saturated magnetization of m-Cell/Fe3O4/ACCs reached 48.2emug−1 and the magnetic adsorbent showed characteristics of superparamagnetism, which indicated that m-Cell/Fe3O4/ACCs could be separated from treated solution by a magnetic process. A comparison of kinetic models showed that the overall adsorption process was best described by pseudo-second-order kinetic model. Thermodynamic analysis indicated an exothermic nature of adsorption and a spontaneous and favorable process. The m-Cell/Fe3O4/ACCs might be a promising candidate of high efficiency, low cost and convenient separation under magnetic field.
Keywords: Cellulose; Activated carbon; Azo dye; Adsorption; Magnetic material
Degradation of organic matter in olive-oil mill wastewater through homogeneous Fenton-like reaction
by Leopoldo Martínez Nieto; Gassan Hodaifa; Salvador Rodríguez; José A. Giménez; Javier Ochando (pp. 503-510).
► This work was treated the application of Fenton-like oxidation to the depuration of a real OMW. ► This problem is still an important issue to emerging needs to achieve solutions that offer new alternatives with minimum cost. ► Moreover, kinetic studies involving such wastewater were performed, which is not usually found in literature.The degradation of organic matter present in olive-oil mill wastewater from two-phase olive-oil extraction process was carried out by chemical oxidation reaction. It was shown that organic matter is efficiently degraded through a Fenton-like reaction using FeCl3 as catalyst in the presence of hydrogen peroxide. Oxidation was carried out in a batch reactor with controlled temperature. Operating at pH 3.0, H2O2 concentration=100gdm−3, [FeCl3]/[H2O2] ratio=0.04, and ambient temperature (281–285K), 92.6% of chemical oxygen demand and 99.8% of total phenols were removed. Kinetics can be described by a two step first order model. The kinetic parameters at ambient temperature and pH 3 were calculated. In the temperature range 278–313K, the best performance was obtained at 303K. The experiments performed at different temperatures allowed to calculate the apparent activation energy Ea=8.7kJmol−1.
Keywords: Fenton's reagent; Oxidation; COD; Phenols compounds; Kinetics study; Olive-oil mill wastewater
Adsorption mechanism of Cu(II) ions from aqueous solution by glutaraldehyde crosslinked humic acid-immobilized sodium alginate porous membrane adsorbent
by Jian Hua Chen; Qing Lin Liu; Shi Rong Hu; Jian Cong Ni; Ya Shan He (pp. 511-519).
► The uptake capacity of GA-HA/SA for Cu(II) ions was encouraging. ► Adsorption equilibrium was obtained within 60min. ► Ionic strength and solution pH greatly affected uptake capacity of the GA-HA/SA. ► Adsorption of Cu(II) ions was mainly controlled by the intraparticle diffusion.A novel porous composite membrane adsorbent GA-HA/SA was prepared by glutaraldehyde (GA) crosslinked humic acid (HA) immobilized sodium alginate (SA) and used to remove Cu(II) ions from wastewater. Compared with traditional centrifugation or filtration methods for separating adsorbent from solution, the Cu-HA/SA can be used more conveniently. The physico-chemical properties of GA-HA/SA before and after adsorption were investigated by FT-IR, SEM and EDX methods. To investigate the effects of experimental parameters on adsorption behavior, a batch of experiments were performed by changing the concentration of porogen polyethylene glycol in the GA-HA/SA, solution pH, ionic strength, initial Cu(II) ions concentration and contact time. The GA-HA/SA showed the maximum uptake of 63.1mg/g under the optimal adsorption condition. Based on adsorption experiment, it can be found that uptake capacity of the GA-HA/SA for Cu(II) ions decreased with an increasing of ionic strength, and solution pH decreased until the adsorption equilibrium. Kinetics experiments indicated the pseudo-second-order model displayed the best correlation with adsorption kinetics data. The Crank model showed that the intraparticle solute diffusion is the rate-controlling adsorption step. Besides, adsorption experimental data could be better described by the Freundlich isotherm model.
Keywords: Humic acid; Sodium alginate; Membrane; Adsorption mechanism; Cu(II)
Chitosan as an effective low-cost sorbent of heavy metal complexes with the polyaspartic acid
by Dorota Kołodyńska (pp. 520-529).
Display Omitted► Chitosan for removal of heavy metal complexes with DS. ► CS is the most effective for Cu(II) sorption. ► Kinetic data were well described by the pseudo-second order model. ► Process is pH, temperature, concentration dependent.Chitosan (CS) was used for the adsorption of Cu(II), Zn(II), Cd(II) and Pb(II) complexes with the ‘green’ chelating agent – polyaspartic acid (DS) from waste water effluents. CS samples were characterized using FT-IR spectroscopy and AFM analysis. Among different factors that influence the sorption process, the following were studied in detail: solution pH, initial concentration, phase contact time, temperature and effect of competitive ions. The most important factor affecting the effectiveness of sorption is pH and concentration. From the Langmuir adsorption model, the adsorption capacity of CS for Cu(II), Zn(II), Cd(II) and Pb(II) complexes was equal to: 85.21mg/g, 46.82mg/g, 89.58mg/g and 79.05mg/g, respectively. The results showed that the pseudo second-order model was more suitable to describe the sorption kinetics on CS. The rate constant ( k2) decreases with the increasing metal complexes concentration, whereas the equilibrium sorption capacity ( q2) and the initial sorption rate ( h) increase.
Keywords: Adsorption; Biodegradable; Biopolymers; Chitosan
Effect of temperature and NO x concentration on nitric oxide removal from simulated lean-burn engine exhaust via electrochemical-catalytic cells
by Ta-Jen Huang; Chun-Hsiu Wang (pp. 530-535).
► An electrochemical-catalytic cell can be used for automotive emissions control. ► The electrochemical-catalytic cell (ECC) does not consume any reductant. ► Very high concentration of NO x can be treated in the ECC. ► Higher oxygen and NO x concentrations can result in higher NO conversion. ► Higher NO conversion is associated with higher oxygen mobility.An electrochemical-catalytic cell (ECC) was constructed with Ni–YSZ as the anode, YSZ as the electrolyte, and La0.8Sr0.2MnO3 (LSM) or La0.6Sr0.4Co0.8Cu0.2O3 (LSCC) as the cathode materials. The ECC is simplified from solid oxide fuel cell by deleting the current collecting parts and does not consume any reductant. Very high concentration of NO x can be treated in the ECC. Higher oxygen concentration results in higher NO conversion. In the high NO x concentration range, higher NO x concentration also results in higher NO conversion. This higher NO conversion is associated with larger rate of oxygen desorption induced by higher oxygen mobility during direct NO decomposition. The beneficial effect of temperature is to increase the oxygen mobility.
Keywords: Nitric oxide; NO; x; concentration; Oxygen mobility; Automotive emissions control; Lean-burn engine; Electrochemical-catalytic cell
Paramagnetic ionic liquids as “liquid fixed-bed” catalysts in flow application
by V. Misuk; D. Breuch; H. Löwe (pp. 536-540).
Display Omitted► Paramagnetic ionic liquid [BMIM]Fe2Cl7 used as fixed liquid catalyst in micro-structured reactors for esterification reaction.► Catalysts is fixed by external magnetic forces of NdFeB magnets.► The magnetically fixed liquid forms a new type of a liquid fixed-bed (LFB) catalyst.► The esterification of cyclohexanol with acetic acid gives 78.5% (GC) yield of the respective ester within 1.3s.► LFBs with additional functional groups or ligands opens-up new and unusual processing in continuous micro flow applications.The structural diversity of Ionic Liquids is well-known and widely used to generate solvents designed for special applications. Magnetic as well as catalytic properties have been described previously. To our best knowledge we report the first time about the combination of both, the magnetic and catalytic behaviour of imidazole based magnetic ionic liquids was used to establish a so-called liquid fixed-bed (LFB) in a micro-/meso-structured reactor. As proof of priciple the esterification of Ac2O with cyclohexanol was investigated by bubbling generated regular microdroplets of the reaction mixture through the magnetically fixed ionic liquid catalyst. With residence times of approx. 1.4s a yield of 78.5% of the target ester molecule was achieved.
Keywords: Magnetic ionic liquids; Liquid fixed-bed; Flow chemistry; Micro-structured reactor
Methodology for multi-scale design of isothermal laminar flow networks
by J.-M. Commenge; M. Saber; L. Falk (pp. 541-551).
► Design methodology for uniform flow distribution in multi-scale channel networks. ► Multi-scale design for minimum flow maldistribution and pressure drop. ► Rapid design process based on charts, with detailed step-by-step methodology. ► Tools to design optimized geometries for highly parallel microreactors. ► Rapid and flexible numbering-up method.The use of microchannels in industrial-scale reactors requires a very large number of parallel microchannels. In order to maintain the performance of this multi-scale reactor, a uniform flow distribution must be ensured, while maintaining an acceptable pressure drop. This work presents a step-by-step methodology that enables to calculate the flow characteristics (maldistribution and flow resistance) of multi-scale microchannel reactors, under laminar and isothermal conditions.A successive assembling of two-scale networks is considered to build the entire multi-scale network. Thus, based on a resistive model and taking into account the self-similar topology of the network, this methodology simplifies the multi-scale network into a two-scale equivalent network, whose characteristics can be read on design charts. Combination of intermediate values obtained at each step of the method then enables to calculate the global characteristics of the entire network. Successive applications of this methodology on various network arrangements finally enable to discriminate them and choose the most-appropriate design.
Keywords: Multi-scale design; Flow network; Microchannel; Manifold; Microstructured reactor; Laminar; Numbering-up; Scale-up
The influence of an exothermic reaction on the spatial distribution of the liquid phase in a trickle bed reactor: Direct evidence provided by NMR imaging
by Anna A. Lysova; Agnes von Garnier; Edme H. Hardy; Rainer Reimert; Igor V. Koptyug (pp. 552-563).
Display Omitted► NMR imaging to study liquid phase distribution in operating catalyst bed. ► 2D external and internal liquid holdup maps during reaction. ► Exothermic reaction in trickle bed affected liquid phase distribution. ► During reaction catalyst bed characterized by non-uniform liquid phase distribution. ► Without reaction bed largely filled with liquid phase.In this paper, NMR imaging was applied to study the distribution of the liquid phase in a fixed catalyst bed of an operating multiphase reactor with a cocurrent gas–liquid flow under conditions when the heterogeneous catalytic hydrogenation of 1-octene was taking place in the reactor. The 2D maps of the spatial distribution of the external and internal liquid holdups in the various regimes of the catalyst bed operation have been obtained for the first time in the course of the reaction. It was shown by a direct in situ method that an exothermic reaction taking place in a trickle bed reactor dramatically affected the distribution of the liquid phase in the catalyst bed. In particular, in the presence of the reaction, the catalyst bed was characterized by a non-uniform distribution of the liquid phase, as revealed by evaluating the external and internal liquid holdups. In the absence of the reaction, the bed was largely filled with the liquid phase.
Keywords: NMR imaging; Trickle bed reactor; 1-Octene hydrogenation; Liquid holdup
Two-dimensional computational fluid dynamics simulation of nitrogen and sulfur oxides emissions in a circulating fluidized bed combustor
by W. Zhou; C.S. Zhao; L.B. Duan; X.P. Chen; C. Liang (pp. 564-573).
► Coal combustion in CFB is successfully simulated by a comprehensive CFD model. ► Two separate energy equations can predict local high temperature regions. ► The 70s simulation achieves a steady state for gas compositions. ► Predictions of N and S dioxides agree well with experiments. ► Secondary air has important impacts on distributions of temperature, NO and SO2.Based on the previously established two-dimensional computational fluid dynamics (CFD) model which described processes of coal devolatilization, volatile combustion and char combustion in circulating fluidized bed (CFB) combustors, nitrogen and sulfur oxides emissions are numerically simulated and investigated in the present paper. First of all, a more accurate heat transfer model was established by applying energy conservation equations to gas and solid phases separately, rather than one conservation equation of the mixture enthalpy in our previous model. Interphase heat transfer mechanism was considered as well as bed-to-wall heat transfer. For the constant wall temperature boundary condition, proportional heat sinks were adopted in the furnace to compensate the missing heat transfer surfaces from 3-D cylinder riser to 2-D planar model. Results of temperature distributions agreed well with the experimental data.Secondly, processes related to nitrogen and sulfur oxides emissions are included. Results from our previous studies showed that, no NH3 was detected during pyrolysis of this bituminous coal by TG-FTIR (Thermogravimetry coupled with Fourier Transform Infrared) analysis. So it was assumed that fuel N and S partially released to the volatile as HCN and SO2, and partially retained in the char. HCN converted to NO and N2O quickly through homogenous reactions. Char N and S converted to NO and SO2 during char combustion. NO x was reduced to N2 by char carbon or CO. SO2 was retained by CaO calcined from CaCO3. By converting reaction rate expressions to suitable forms for Eulerian–Eulerian modeling, sulfation reaction rates from two different literatures were compared. Performances of SO2 emission were evaluated for conditions with/without considering sulfur self-retention. Distributions of gas components in the furnace were predicted and the outlet gas concentrations were validated by the experimental data. Distributions of certain reaction rates in the riser were also illustrated.
Keywords: Computational fluid dynamics; Circulating fluidized bed; Combustion; NO emission; SO; 2; emission
Partial oxidation of methane to syngas with air by lattice oxygen transfer over ZrO2-modified Ce–Fe mixed oxides
by Kongzhai Li; Hua Wang; Yonggang Wei; Dongxia Yan (pp. 574-582).
► Addition of ZrO2 into Ce–Fe system could enhance the interaction between iron and cerium oxides. ► This interaction creates more oxygen vacancies on the material and improves the dispersion of surface iron species. ► These modifications make the Ce–Fe–Zr catalysts more active for methane partial oxidation. ► Repetitive redox treatment can improve the lattice oxygen mobility of the Ce–Fe–Zr oxides. ► Ce–Fe–Zr material shows high activity and stability in the redox process for successive production of syngas.Catalytic performance of Ce–Fe mixed oxides promoted with ZrO2 was investigated for methane partial oxidation to syngas via gas–solid reactions. The results showed that moderate amounts of ZrO2 could strongly enhance the interaction between iron and cerium oxides via increasing the oxygen vacancy concentration and improving the dispersion of free Fe2O3, which improved the activity of Ce–Fe material for methane partial oxidation. However, heavy loading of ZrO2 would lead to a phase segregation of CeO2 and Fe2O3 from the Ce–Fe solid solution, resulting in a decrease in syngas selectivity. Among the tested samples, Ce–Fe–Zr (0.05) sample showed the best catalytic performance (with both high methane conversion and syngas selectivity). Despite severe sintering, the Ce–Fe–Zr (0.05) oxides presented high catalytic stability during the repetitive redox process (methane reduction/air re-oxidation) for the continuous production of syngas. This property should be attributed to the increased oxygen vacancy concentration on the mixed oxides after cycling, which could improve the lattice oxygen mobility, counteracting the native effect of material sintering on the catalytic activity for methane partial oxidation.
Keywords: Methane partial oxidation; Syngas; Gas–solid reaction; Ce–Fe–Zr mixed oxides; Redox
Production of n-butyl stearate over PA/NaY catalyst
by Lei Chen; Ping Yin; Rongjun Qu; Xianyang Chen; Qiang Xu; Qinghua Tang (pp. 583-591).
► n-Butyl stearate production over PA/NaY (PA=1-hydroxyethylidenediphosphonic acid). ► Response surface methodology was employed to optimize the experimental conditions. ► The conversion ratio could reach 88.0±0.8% under the optimal conditions. ► The LH and PH kinetic models for this esterification reaction catalyzed by PA/NaY.In the present study, the possibility of using PA/NaY (PA=1-hydroxyethylidenediphosphonic acid) in the esterification reaction of n-butyl acetate production has been investigated. The process optimization using response surface methodology (RSM) was performed and the interactions between the operational variables were elucidated. The optimum values for maximum conversion ratio of stearic acid could be obtained by using a Box–Behnken center-united design with a minimum of experimental work, and the conversion ratio reached 88.0±0.8% with the molar ratio of alcohol to stearic acid being 4:1 and 1.5g of PA/NaY catalyst at 125°C for 2h. Moreover, kinetic models for the esterification reaction catalyzed by PA/NaY were established, and the results were found that the PH mechanism was better at describing the kinetics of this esterification than the LH mechanism. By fitting the kinetic model with the experimental results, it was found that the reaction order n=2, activation energy of the positive reaction Ea+=34.18kJ/mol and that of the reverse reaction Ea−=57.70kJ/mol.
Keywords: n; -Butyl stearate; Esterification; Response surface methodology; Kinetic model; PA/NaY catalyst
Effects of pressure on CO2 reforming of CH4 over carbonaceous catalyst
by Yongfa Zhang; Guojie Zhang; Bingmo Zhang; Fengbo Guo; Yaling Sun (pp. 592-597).
► Effects of pressure on CO2 reforming of CH4 was studied. ► The higher pressure decreased CO2 and CH4 conversion. ► Some process adjustment methods could improve catalysts activity and stability. ► oxygen containing group is attributed to H-abstraction of methane and CO2 adsorption.CO2 reforming of CH4 was studied over laboratory-prepared carbonaceous catalysts at atmospheric pressure (0.1MPa) and high pressure (3.6MPa). The catalysts were characterized by BET and FITR techniques. The catalytic activity and stability of catalysts were closely related to the reaction pressure. It was observed that the use of higher pressure substantially decreased CO2 and CH4 conversion and increased catalyst deactivation during CO2 reforming of CH4, compared to runs at 0.5MPa for carbonaceous catalysts. Deactivation was related to carbon formation. Some process adjustment methods, such as increasing the reaction temperature, prolonging reaction residence time, and increasing CO2 and CH4 molar ratio, which could improve catalysts activity and stability. Besides, the positive effect of surface oxygen containing groups (C–O) on catalyst activity had been demonstrated over carbonaceous catalysts. The basic function of the carbonaceous materials surface area also seemed to increase H-abstraction of methane and CO2 adsorption.
Keywords: Methane reforming; Carbon dioxide; Pressure; Carbonaceous catalyst
Thermo-diffusion and diffusion-thermo effects on MHD free convection flow past a vertical porous plate embedded in a non-Darcian porous medium
by V. Ramachandra Prasad; B. Vasu; O. Anwar Bég (pp. 598-606).
► Thermo-diffusion and diffusion-thermo effects. ► Non-Darcy porous medium. ► Implicit finite difference Keller Box method. ► Free convection heat and mass transfer.An analysis is presented for the steady free convection heat and mass transfer past a vertical porous plate in a non-Darcy porous medium subjected to uniform magnetic field with Soret (thermo-diffusion) and Dufour (diffusion-thermo) effects included. The non-Darcy effects are simulated via second order Forchheimer drag force term in the momentum boundary layer equation. The governing boundary layer equations are transformed into a non-dimensional form and the resulting non-linear system of partial differential equations are solved using the efficient Keller-box implicit numerical finite difference method. Increasing magnetohydrodynamic body force parameter ( M) is found to decelerate the flow. Increasing Soret number and simultaneously decreasing Dufour number enhances the local heat transfer rate (local Nusselt number) at the plate surface with the opposite effect sustained for the mass transfer rate (local Sherwood number). Increasing Forchheimer inertial drag parameter ( Λ) retards the flow considerably but enhances temperatures. Increasing Darcy number accelerates the flow due to a corresponding rise in permeability of the regime and concomitant decrease in Darcian impedance. Applications of the model arise in metallurgical materials processing, chemical engineering flow control, geothermal hydromagnetics, etc.
Keywords: Porous media transport; Magnetic field; Heat and mass transfer; Non-Darcy; Vertical porous plate; Soret number; Dufour number; Buoyancy; Implicit numerical method
Effect of gas and liquid flowrates on the size distribution of barium sulfate nanoparticles precipitated in a two phase flow capillary microreactor
by D. Jeevarathinam; A.K. Gupta; B. Pitchumani; Ratan Mohan (pp. 607-611).
► Barium sulfate nanoparticles precipitation. ► Two phase flow capillary microreactor. ► Each liquid slug a microreactor. ► BaSO4 product mean size found to decrease as liquid or gas flowrate is increased.Production of fine particles by precipitation is a relatively simple process but the control of product particle size distribution can be difficult. In recent years microreactors are being seen as effective devices to achieve this aim and in that the two-phase flow microreactor is a promising alternative. In the present work, fine (nano/micro) particles of barium sulfate have been produced by reacting barium chloride and sodium sulfate solutions in a 30cm long and 830μm inner diameter glass capillary microreactor. The T-inlet section has all three limbs 15mm long and 1mm in diameter. Particle sizes produced ranged from about 200nm to 1100nm, with mean sizes between 300nm and 670nm. Results show that an increase in the flowrate of any of the three streams, the two reactant liquid streams and one inert gas stream, led to a decrease in the mean particle size of the precipitated barium sulfate product. Increased mixing and higher Ba2+ ion concentrations in the small microreactor (liquid slugs) are believed to shift rates in favour of nucleation as compared to agglomeration, yielding smaller particles in the product. Size variation results show a trend similar to that reported in earlier researches on BaSO4 precipitation in single (liquid) phase microreactors but the actual sizes obtained in the present work are bigger. Other geometries and flow conditions may yield smaller particles, hence the need for further investigation of the two-phase flow system.
Keywords: Nanoparticles; Microreactors; Gas–liquid slug flow; BaSO; 4; precipitation
Supported undecatungstophosphate: An efficient recyclable bi-functional catalyst for esterification of alcohols as well as selective oxidation of styrene
by Pragati A. Shringarpure; Anjali Patel (pp. 612-619).
Display Omitted► Development of neutral alumina supported undecatungstophosphate as a bi-functional catalyst. ► Used for esterification of 1° and 2° alcohols as well as for solvent free liquid phase oxidation of styrene. ► Designed heterogeneous catalyst is a clean and a promising alternative for environmentally hazardous stiochiometric catalysts. ► The present solid catalyst is effective in waste minimization, especially for oxidation reactions.A versatile bi-functional solid catalytic system comprising undecatungstophosphate and neutral alumina has been introduced for acid catalysis as well as oxidation reactions. The catalytic activity of calcined catalysts was also evaluated for esterification as well as oxidation reactions under optimized conditions. The supported undecatungstophosphate can be regenerated after a simple workup and can be reused up to 3 cycles. The Koros Nowak Test was also performed and it was found that the catalytic performances were not mass and heat transfer limited. The present solid catalytic system is a promising clean alternative not only for esterification of alcohols but also for oxidation of styrene under mild reaction conditions.
Keywords: Undecatungstophosphate; Neutral alumina; Esterification; Oxidation
Heteropolyanion-based ionic hybrid solid: A green bulk-type catalyst for hydroxylation of benzene with hydrogen peroxide
by Yan Leng; Jun Wang; Dunru Zhu; Lei Shen; Pingping Zhao; Mingjue Zhang (pp. 620-626).
A new heteropolyacid (HPA)-based ionic hybrid nanospheric catalyst is synthesized by combining divalent ionic liquid (IL) cations with Keggin heteropolyanions, leading to liquid–solid biphasic hydroxylation of benzene with H2O2, and offering advantages of high catalytic activity, convenient recovery, steady reuse, and simple preparation.Display Omitted► A new ionic hybrid is prepared with dicationic ionic liquid and heteropolyacid. ► The hybrid catalyst leads to the heterogeneous hydroxylation of benzene with H2O2. ► The hybrid catalyst gives high phenol yield and selectivity in the hydroxylation. ► The catalyst shows convenient recovery, steady reuse, and simple preparation. ► The bulk-type catalysis accounts for the hybrid's excellent catalytic performance.A novel heteropolyanion-based ionic hybrid was prepared by combining the divalent ionic liquid (IL) cation of 1,1′-(butane-1,4-diyl)-bis(3-methylimidazolium) with the Keggin-structured V-containing heteropolyanion, and characterized by1H NMR, FT-IR, ESI-MS, XRD, SEM, TG, BET surface area, melting point, and elemental analysis. Its catalytic activity was evaluated in the hydroxylation of benzene with aqueous H2O2, including the testing of the influence of organic cations, catalytic reusability and optimization of reaction conditions. This hybrid is characterized to be semi-amorphous nanoparticles with a IL-like composition. The hybrid catalyst leads to the liquid–solid biphasic reaction system for hydroxylation of benzene with H2O2, presenting such advantages as high catalytic activity, convenient recovery, and steady reuse. The strong ionic interaction between the divalent IL cation and the heteropolyanion is responsible for the catalyst's solid nature and insolubility, and moreover, the bulk-type catalysis involving the V5+/V4+ redox pairs as active centers accounts for the hybrid's excellent catalytic performance.
Keywords: Hybrid catalysts; Heteropolyacids; Hydroxylation of benzene; Heterogeneous catalysis; Phenol
Kinetic and Raman spectroscopic study on catalytic characteristics of carbon blacks in methane decomposition
by Yuki Kameya; Katsunori Hanamura (pp. 627-635).
► Significance of carbon deposition in a kinetic study was demonstrated. ► A new evaluation method of activation energies was presented. ► Activation energy invariant in all stages of time-varying behavior was obtained. ► Raman spectroscopy was applied to carbon blacks used in the reaction. ► Initial structural evolution of carbon blacks was successfully characterized.Carbon blacks have been known to exhibit catalytic activities in methane decomposition. However, there remain problems in determining the activation energy and the time-varying catalytic characteristics. In the present study, the significance of carbon deposition on carbon black in a kinetic study was investigated, and the applicability of Raman spectroscopy to the characterization of carbon blacks was examined. First, the activation energy of carbon black was determined at two temperature ranges without taking into account the effect of carbon deposition, and the significant difference between them was observed. Then, the amount of deposited carbon was introduced in a kinetic study to represent the degree of change in catalyst properties due to carbon deposition. On the basis of the observation that the time-varying catalytic characteristics had clear correlations with the amount of deposited carbon, the evaluation method of the activation energy in which the effect of carbon deposition is taken into account was presented. The constant activation energy for each carbon black was obtained in the wide range of the amount of deposited carbon. The presented method was demonstrated to be useful in determining activation energies of carbon blacks which exhibit the time-varying catalytic characteristics. Finally, Raman spectroscopy was applied to carbon blacks, which included fresh ones and those used in the methane decomposition experiment for specified reaction times. The obtained Raman spectra exhibited significant changes in the initial deactivation stage. It was demonstrated that Raman spectroscopy was useful to characterize the initial structural evolution of carbon blacks.
Keywords: Methane catalytic decomposition; Carbon black; Kinetic study; Carbon deposition; Activation energy; Raman spectroscopy
Recursive GPR for nonlinear dynamic process modeling
by Wangdong Ni; Soon Keat Tan; Wun Jern Ng (pp. 636-643).
► We developed a recursive GPR model for nonlinear dynamic system modeling. ► RGPR model could effectively track the process dynamics with high adaptability. ► The ARX structure and bias correction can further improve adaptability of model. ► A polymerization process is used to present the performance of RGPR model.With its added features in the measurement of confidence, and lower demands on the training parameters, the Gaussian process regression (GPR) model has been shown to be a powerful dynamic process model for nonlinear dynamic systems. The authors have developed a recursive GPR model which effectively tracks process dynamics in both sample-wise and block-wise manners. By incorporating an appropriate bias correction technique, the recursive GPR model was further developed to provide better match between the predicted and measured process parameter values. Then the adaptation strategy based on autoregression with exogenous inputs structure was incorporated into the recursive GPR model. The simulation results showed that the recursive GPR model effectively tracked the process dynamics of nonlinear dynamic systems and improve the adaptability of dynamic models. The results of application of the recursive GPR algorithms developed to an industrial propylene polymerization process are presented and discussed.
Keywords: Gaussian process regression; Nonlinear system modeling; Recursive GPR; Bias correction
Simple high-order approximations for unsteady-state diffusion, adsorption and reaction in a catalyst: A unified method by a continued fraction for slab, cylinder and sphere geometries
by Jietae Lee; Dong Hyun Kim (pp. 644-650).
► We developed a continued fraction for unsteady-state diffusion, adsorption and a first-order reaction in a slab, cylinder and sphere catalyst. ► Truncated continued fractions yield approximations of the exact pore diffusion model. ► The approximations are very easy to construct and easy to use to simplify modeling of adsorbers and packed-bed reactors.For unsteady-state diffusion, adsorption and a first-order reaction in a slab, cylinder and sphere catalyst, high-order approximations in the form of coupled ordinary differential equations are developed to substitute the exact partial differential equations. An infinite continued fraction is developed, which unifies the exact transfer functions of the three geometries as a function of the shape factor and the Thiele modulus in the Laplace domain. The time-domain approximations are obtained from the truncated continued fractions. The coefficients in the time-domain approximations are very easy to determine, and increasing the order of approximation is simple and straightforward.
Keywords: Continued fraction; Linear driving force formula; High-order approximation; Shape factor; Pore diffusion model
Oxovanadium(IV) salophen complex covalently anchored to multi-wall carbon nanotubes (MWNTs) as heterogeneous catalyst for oxidation of cyclooctene
by Masoud Salavati-Niasari; Alireza Badiei; Kamal Saberyan (pp. 651-658).
► [VO(OH)2-salophen] complex was covalently grafted on the MWNTs. ► The catalytic activity was tested in the oxidation of cyclooctene. ► Nanocomposites indicate good catalytic activity and selectivity in the oxidation.The chemical modification of multi-wall carbon nanotubes (MWNTs) is an emerging area in material science. In the present study, hydroxyl functionalized oxovanadium(IV) Schiff-base; ( N, N-bis(4-hydroxysalicylidene)phenylene-1,2-diamine)oxovanadium(IV), [VO((OH)2-salophen)]; has been covalently anchored on modified MWNTs. The new modified MWNTs ([VO((OH)2-salophen)]@MWNTs]) have been characterized by transmission electron microscopy (TEM), atomic absorption spectroscopic (AAS) analysis, X-ray diffraction (XRD), Diffuse reflectance (DRS) UV–vis, FT-IR spectroscopy and elemental analysis. The analytical data indicated a composition corresponding to the mononuclear complex of tetradentate Schiff-base ligand. The characterization of the data showed the absence of extraneous complex, retention of MWNTs and covalently anchored on modified MWNTs. Liquid-phase oxidation of cyclooctene with molecular oxygen to a mixture of cyclooctene-1-one, cyclooctene-1-ol and cyclooctene epoxide in CH3CN have been reported using oxovanadium(IV) Schiff-base complex covalently anchored on modified MWNTs as catalysts.
Keywords: Multi-wall carbon nanotubes; Oxovanadium(IV); Heterogeneous catalyst; Oxidation of cyclooctene
Improvement of tensile and thermal properties of poly(lactic acid) composites with admicellar-treated rice straw fiber
by Yang Zhao; Jianhui Qiu; Huixia Feng; Min Zhang; Lin Lei; Xueli Wu (pp. 659-666).
► Rice straw fiber (RSF) was treated by admicellar polymerization with a poly(methyl methacrylate) (PMMA) film coating. ► Admicellar-treated RSF reinforced poly(lactic acid) (PLA) composite was prepared for the first time. ► MMA was selected as the monomer because it has better compatibility with PLA calculated by Hansen solubility parameters. ► Mechanical and thermal properties of composite were obviously improved by RSF treatment.Natural fiber reinforced poly(lactic acid) (PLA) composites have received great attention. However, the poor interfacial adhesion between strong polar natural fibers and the non-polar PLA matrix limited its applications. In the present study, rice straw fiber (RSF) was pre-treated to improve its compatibility with PLA. Methyl methacrylate (MMA) was selected as the monomer in the admicellar polymerization for the RSF treatment, because RSF coated with poly(methyl methacrylate) (PMMA) thin film would have better compatibility with the PLA matrix according to a preliminary estimated using Hansen solubility parameters. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) indicated the evidence that PMMA film was coated on RSF. Then, the influences of treatment on electrophoretic properties and crystallinity of admicellar-treated RSF (TRSF) were examined by zeta ( ζ) potential and X-ray diffraction (XRD) measurements, respectively. The (T)RSF-PLA composites were prepared by injection molding machine, the mechanical properties showed that the tensile strength of TRSF-PLA increased significantly at all TRSF contents (10, 20, 30% v/v). The elongation of TRSF-PLA (0.1%, v/v MMA) composites was increased 60.8% compared with RSF-PLA composite (30%, v/v fiber content). The significantly improved mechanical properties were attributed to the interfacial adhesion improvement between TRSF and PLA which was investigated by SEM. The thermal properties of (T)RSF-PLA were investigated by thermogravimetric analysis (TGA), and the TGA results confirmed that the thermal stability of TRSF-PLA was improved compared with RSF-PLA composite.
Keywords: Natural fiber composites; Admicellar polymerization; Hansen solubility parameters; Zeta potential; Mechanical property; Rice straw fiber; Poly(lactic acid); Poly(methyl methacrylate)
Comparative investigation of hydrogen production over Ag-, Ni-, and Cu-loaded mesoporous-assembled TiO2–ZrO2 mixed oxide nanocrystal photocatalysts
by Surakerk Onsuratoom; Tarawipa Puangpetch; Sumaeth Chavadej (pp. 667-675).
Display Omitted► Ag, Ni, and Cu loadings on 0.93TiO2–0.07ZrO2 mixed oxide were achieved via photochemical deposition. ► The photocatalytic H2 production activity of the loaded 0.93TiO2–0.07ZrO2 mixed oxides was investigated. ► The photocatalytic activity enhancement was attained in the following order: Cu>Ni>Ag. ► The properties of these metals were related to their photocatalytic activity enhancement.This work focused on the enhancement of photocatalytic hydrogen production activity under UV light irradiation of mesoporous-assembled 0.93TiO2–0.07ZrO2 mixed oxide nanocrystal photocatalysts (having the TiO2-to-ZrO2 molar ratio of 93:7) by non-precious metal (Ag, Ni, and Cu) loadings via a photochemical deposition method. The mesoporous-assembled 0.93TiO2–0.07ZrO2 mixed oxide was synthesized by a sol–gel process with the aid of a structure-directing surfactant prior to the metal loadings. The prepared photocatalysts were characterized by N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive analysis, X-ray diffraction, UV–visible spectroscopy, and H2 chemisorption. The most efficient loaded metal was found to be Cu due to its suitable physical, chemical, and electrochemical properties with the 0.93TiO2–0.07ZrO2 mixed oxide-based photocatalyst. The 0.15wt.% Cu-loaded 0.93TiO2–0.07ZrO2 mixed oxide photocatalyst exhibited the highest photocatalytic hydrogen production activity with a hydrogen production rate of 12.8cm3h−1gcat−1.
Keywords: Photocatalytic hydrogen production; Sol–gel process; Mesoporous assembly; TiO; 2; –ZrO; 2; mixed oxide; Metal loading