Wet peroxide oxidation and catalytic wet oxidation of stripped sour water produced during oil shale refining

Catalytic wet oxidation (CWO) and wet peroxide oxidation (WPO) of stripped sour water (SSW) from an oil shale refinery was investigated. Greater than 70% total organic carbon (TOC) removal from SSW was achieved using Cu(NO(3))(2) catalysed WO under the following conditions using a glass lined reaction vessel: 200 degrees C, pO(2)=0.5MPa, 3h, [Cu(NO(3))(2)]=67mmol/L. Significant TOC removal ( approximately 31%) also occurred in the system without added oxygen. It is proposed that this is predominantly due to copper catalysed oxidative decarboxylation of organics in SSW based on observed changes in copper oxidation state. Greater than 80% TOC removal was achieved using WPO under the following conditions: 150 degrees C, t=1.5h, [H(2)O(2)]=64g/L. Significantly more TOC could be removed from SSW by adding H(2)O(2) in small doses as opposed to adding the same total amount in one single dose. It was concluded that WPO was a far more effective process for removing odorous compounds from SSW.     

Abatement of phenolic mixtures by catalytic wet oxidation enhanced by Fenton's pretreatment: effect of H2O2 dosage and temperature

Catalytic wet oxidation (CWO) of a phenolic mixture containing phenol, o-cresol and p-cresol (500mg/L on each pollutant) has been carried out using a commercial activated carbon (AC) as catalyst, placed in a continuous three-phase reactor. Total pressure was 16 bar and temperature was 127 degrees C. Pollutant conversion, mineralization, intermediate distribution, and toxicity were measured at the reactor outlet. Under these conditions no detoxification of the inlet effluent was found even at the highest catalyst weight (W) to liquid flow rate (Q(L)) ratio used. On the other hand, some Fenton Runs (FR) have been carried out in a batch way using the same phenolic aqueous mixture previously cited. The concentration of Fe(2+) was set to 10mg/L. The influence of the H(2)O(2) amount (between 10 and 100% of the stoichiometric dose) and temperature (30, 50, and 70 degrees C) on phenols conversion, mineralization, and detoxification have been analyzed. Phenols conversion was near unity at low hydrogen peroxide dosage but mineralization and detoxification achieved an asymptotic value at each temperature conditions. The integration of Fenton reagent as pretreatment of the CWO process remarkably improves the efficiency of the CWO reactor and allows to obtain detoxified effluents at mild temperature conditions and relatively low W/Q(L) values. For a given phenolic mixture a temperature range of 30-50 degrees C in the Fenton pretreatment with a H(2)O(2) dosage between 20 and 40% of the stoichiometric amount required can be proposed.     

载体炭对CuO/AC(F)催化-吸附剂干法催化氧化苯酚的影响

为了探讨载体炭对CuO／AC(F)催化-吸附剂干法催化氧化苯酚的影响，选择四种性质不同的活性炭(纤维)作载体，制得双功能材料CuO／AC(F)催化一吸附剂。通过TG-MS联用系统研究了CuO,／AC(F)催化-吸附剂的苯酚催化氧化活性及其自身的烧蚀活性，采用BET、XRD等手段表征了载体炭和CuO／AC(F)催化-吸附剂的物理化学特性。结果表明，载体炭中的灰分影响CuO／AC(F)催化-吸附剂的苯酚催化氧化活性，中孔促进苯酚的催化氧化，表面含氧官能团对苯酚催化氧化活性的影响不大，但表面含氧官能团和灰分均能促进催化-吸附剂的烧蚀。苯酚的催化氧化和炭的催化氧化可能遵循不同的反应历程。     

Kinetic and wet oxidation of phenol catalyzed by non-promoted and potassium-promoted manganese/cerium oxide

The wet oxidation of organic compounds to CO2 and H2O has been shown to be a very efficient technique in the outflows treatment. This work focuses on the interaction of the chemical element potassium with the catalyst MnO2-CeO2 in the wet degradation of phenol. The reaction has been carried out in an autoclave with a controlled system of agitation, pressure, temperature and sampling of the liquid phase. The experiments were performed in the presence of the catalysts MnO2-CeO2 and K-MnO2-CeO2 in the following operational conditions: temperature of 130 degrees C, P = 20.4 atm, catalyst concentration in the range 1.5-5.0 g/L, initial phenol concentration of 0.5 g/L, initial pH varying between 6.8 and 8.5, and percentage of potassium in the catalyst MnO2-CeO2 ranging between 0% and 10%. Curves indicating the profile of conversion of total organic carbon show that the phenol degradation is favored when the potassium quantity is reduced. This behaviour is confirmed by BET analysis, whereby the catalyst presents larger specific area when compared to the percentages of other components. Regardless of the catalyst used in the phenol oxidation, the kinetic constant of reaction had the same order of magnitude for two parallel stages proposed by a first-order kinetic model.     

Catalytic wet peroxide oxidation of azo dye (Congo red) using modified Y zeolite as catalyst

The present study explores the degradation of azo dye (Congo red) by catalytic wet peroxide oxidation using Fe exchanged commercial Y zeolite as a catalyst. The effects of various operating parameters like temperature, initial pH, hydrogen peroxide concentration and catalyst loading on the removal of dye, color and COD from an aqueous solution were studied at atmospheric pressure. The percent removals of dye, color and COD at optimum pH₀ 7, 90 °C using 0.6 ml H₂O₂/350 ml solution and 1 g/l catalyst was 97% (in 4 h), 100% (in 45 min) and 58% (in 4 h), respectively. The % dye removal has been found to be less in comparison to % color removal at all conditions, e.g. dye removal in 45 min and at above conditions was 82%, whereas the color removal was 100%. The results indicate that the Fe exchanged Y zeolite is a promising catalyst for dye removal. Fe exchanged catalyst is characterized using XRD, SEM/EDAX, surface area analyzer and FTIR. Though the dye, color and COD removals were maximum at pH₀ 2 but as the leaching of Fe from the catalyst was more in acidic pH range, pH₀ 7 was taken as operating pH due to almost comparable removals as of pH₀ 2 and no leaching of Fe ions.     

甲醛湿式氧化催化剂的制备及性能研究

用FTIR和N2吸附法对活性炭进行表面分析,通过原子吸收光谱考察了铜在活性炭表面的吸附行为,制备了几种甲醛湿式氧化的催化剂,对比研究了它们在常温常压下对甲醛氧化的催化性能。结果表明,活性炭氧化改性后表面含氧基团增加,对铜和甲醛的吸附性能提高。活性炭表面负载的铜、银、铁对甲醛湿式氧化都有一定的催化能力,其中栽铜活性炭的催化效果最好,载铁活性炭的催化性能优于载银活性炭,催化动力学曲线表明,氧化改性后,载铜活性炭的催化性能进一步提高。     

Characteristics of titania supported copper oxide catalysts for wet air oxidation of phenol

Various techniques have been used to characterize the CuO(x)/TiO(2) catalysts with different copper loading. Surface area, pore volume and pore size distribution of the prepared catalysts were estimated from nitrogen adsorption isotherm. Temperature programmed reduction (TPR), X-ray diffraction (XRD), electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) experiments were performed to investigate the chemical state of the copper species. The chemical state of copper in the CuO(x)/TiO(2) catalysts varied with copper loading (1-25wt.%): highly dispersed Cu(2+) cluster for 1 and 5wt.%, and bulk CuO for 7-25wt.%. The activity and mineralization selectivity of the CuO(x)/TiO(2) catalysts increased with copper loading up to 20wt.%, and remained almost constant for higher copper loading. The optimum copper loading was 20wt.% for the wet air oxidation of phenol over the CuO(x)/TiO(2) catalysts in this work. The stability of the CuO(x)/TiO(2) catalysts with different copper loading was also studied with respect to carbonaceous deposits and copper leaching.     

Catalytic and non-catalytic wet air oxidation of sodium dodecylbenzene sulfonate: kinetics and biodegradability enhancement

Wet air oxidation (WAO) and catalytic wet air oxidation (CWAO) were investigated as suitable precursors for the biological treatment of industrial wastewater containing sodium dodecylbenzene sulfonate (DBS). Two hours WAO semi-batch experiments were conducted at 15 bar of oxygen partial pressure (P(O2)) and at 180, 200 and 220 degrees C. It was found that the highest temperature provides appreciable total organic carbon (TOC) and chemical oxygen demand (COD) abatement of about 42 and 47%, correspondingly. Based on the main identified intermediates (acetic acid and sulfobenzoic acid) a reaction pathway for DBS and a kinetic model in WAO were proposed. In the case of CWAO experiments, seventy-two hours tests were done in a fixed bed reactor in continuous trickle flow regime, using a commercial activated carbon (AC) as catalyst. The temperature and P(O2) were 140-160 degrees C and 2-9 bar, respectively. The influence of the operating conditions on the DBS oxidation, the occurrence of oxidative coupling reactions over the AC, and the catalytic activity (in terms of substrate removal) were established. The results show that the AC without any supported active metal behaves bi-functional as adsorbent and catalyst, giving TOC conversions up to 52% at 160 degrees C and 2 bar of P(O2), which were comparable to those obtained in WAO experiments. Respirometric tests were completed before and after CWAO and to the main intermediates identified through the WAO and CWAO oxidation route. Then, the readily biodegradable COD (COD(RB)) of the CWAO and WAO effluents were found. Taking into account these results it was possible to compare whether or not the CWAO or WAO effluents were suitable for a conventional activated sludge plant inoculated with non adapted culture.     

TiO2在微孔型活性炭纤维上的固载及其对苯酚的光催化降解

以环氧树脂作为TiO2与活性炭纤维(ACF)之间联结的前驱体，使TiO2粘附于纤维表面。后经氮气氛下400℃-580℃不同温度的煅烧处理，制得TiO2／ACF复合体。采用BET，SEM，XRD及UV—Vis光谱等手段对复合体的物理化学特性进行了表征。以水中苯酚为目标污染物考察了TiO2／ACF样品的光催化性能、结果表明，460℃煅烧品较其他样品对苯酚具有更好的去除能力。在其重复利用过程中，始终保持了高的光催化效率，直至第三次循环，其最终对苯酚的去除量仍与P25粉体相当。而且，牢固负载的TiO2更具实用性，易于从水中回收。     

The dynamic adsorption characteristics of phenol by granular activated carbon

The objective of the present work is to determine the operating conditions of an activated carbon filter, based on the characteristics of breakthrough curves. For this we apply the technical developed by Mickaels for the ionic exchange and applied by Luchkis for the adsorption, and which is the mass transfer zone. To reach our goal, an evaluation of the operating conditions (height of the bed, flow and concentration of effluent) on the characteristics of the mass transfer zone was made and an explanation of the mechanism of adsorption was given. Thereafter a modeling of the experimental results was done.     

Investigation of the catalytic wet peroxide oxidation of phenol over different types of Cu/ZSM-5 catalyst

In this work oxidation of phenol with hydrogen peroxide on Cu/ZSM-5 catalysts was studied. The catalysts samples were prepared by two different methods: by ionic exchange from the protonic form of commercial ZSM-5 zeolite, and by direct hydrothermal synthesis. Characterization of the catalysts extends to X-ray diffraction (XRD), while the adsorption techniques were used for the measurement of the specific surface area. The catalytic tests were carried out in a stainless steel Parr reactor in batch operation mode at the atmospheric pressure and the temperature range from 50 to 80 degrees C. The mass ratio of the active metal component on the zeolite was in the range of 1.62-3.24 wt.%. for catalyst prepared by direct hydrothermal synthesis and 2.23-3.52 wt.% for catalyst prepared by ion exchange method. The initial concentration of phenol and hydrogen peroxide was 0.01 and 0.1 mol dm(-3), respectively. The influence of different methods of Cu/ZSM-5 preparation on their catalytic performance was monitored in terms of phenol conversion and degree of metal leached into aqueous solution.     

Immobilization of phenol in cement-based solidified/stabilized hazardous wastes using regenerated activated carbon: role of carbon

The use of regenerated activated carbon as an immobilizing additive for phenol in solidification/stabilization (S/S) processes was investigated. The adsorption capacity of regenerated carbon was compared to that of the virgin form and was found to be very close. The effects of pH and Ca(OH)₂ concentration within the S/S monolith on the adsorption process were also examined. Kinetic tests were performed to evaluate the adsorption of phenol on different forms of F400 carbon, including the regenerated form. Kinetic tests were performed in aqueous solutions as well as in liquid–sand mixtures. In both cases, it was found that phenol adsorption on F400 carbon was fairly fast. More than 60% of the equilibrium adsorption amount could be achieved within the first hour for aqueous solutions. For sand-solution kinetics, it was found that 1% carbon (based on dry sand weight) was capable of achieving more than 95% removal of the initial amount of phenol present in solution (1000 and 5000 ppm). Fourier transform infrared (FT-IR) spectroscopy and X-ray mapping tests indicated a homogenous mixing of the carbon into the cement matrix. The carbon was also found to enhance the hydration of cement, which was retarded by the existence of phenol.     

Microwave assisted catalytic wet air oxidation of H-acid in aqueous solution under the atmospheric pressure using activated carbon as catalyst

Catalytic wet air oxidation (CWAO) is a promising method for the treatment of heavily contaminated wastewater. However, its application is restricted due to severe operation conditions (high pressure and high temperature). A microwave (MW) assisted oxidation method was investigated aiming to treat heavily contaminated wastewater under milder conditions. H-acid (1-amino-8-naphthol-3, 6-disulfonic acid) was selected as target compound to evaluate the performance of this novel process. The removal of H-acid and TOC (total organic carbon) for H-acid solution of 3000 mg/L reached as high as 92.6% in 20 min and 84.2% in 60 min, respectively under optimal conditions. The existence of activated carbon and oxygen proved to be critical for effective treatment. The activated carbon acted not only as a catalyst for H-acid decomposition, but also as a special material for the absorption of MW energy. Air was supplied to the reactor as an oxygen source at constant flows. The amino group in H-acid was converted ultimately into nitrate, and sulfonic group into sulfate. This observation gave an evidence of H-acid mineralization although other organic intermediates were unable to be determined. The value of BOD(5)/COD (ratio of 5d biochemical oxygen demand to chemical oxygen demand) increased from 0.008 to 0.467 indicating a significant improvement of biodegradability for the solution, which is beneficial for the further biological treatment of the wastewater.     

Removal of phenol from aqueous solutions by adsorption onto activated carbon prepared from biomass material

Activated carbon derived from rattan sawdust (ACR) was evaluated for its ability to remove phenol from an aqueous solution in a batch process. Equilibrium studies were conducted in the range of 25–200 mg/L initial phenol concentrations, 3–10 solution pH and at temperature of 30 °C. The experimental data were analyzed by the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. Equilibrium data fitted well to the Langmuir model with a maximum adsorption capacity of 149.25 mg/g. The dimensionless separation factor R_L revealed the favorable nature of the isotherm of the phenol-activated carbon system. The pseudo-second-order kinetic model best described the adsorption process. The results proved that the prepared activated carbon was an effective adsorbent for removal of phenol from aqueous solution.     

Catalytic wet peroxide oxidation of phenol solutions over CuO/CeO2 systems

Three 5% CuO/CeO(2) catalysts were synthesized by sol-gel, precipitation and combustion methods, followed by incipient wetness impregnation with copper nitrate. The samples were characterized by XRD, TPR, BET and tested for the catalytic wet peroxide oxidation of a phenol solution (5 g/L). The reaction took place in a batch reactor at atmospheric pressure, in a temperature range of 60-80°C, during 4h. Phenol conversion, H(2)O(2) consumption, pH and chemical oxygen demand were determined. The reaction temperature and the catalyst loading did improve the phenol and the H(2)O(2) conversions. The effect on the selectivity towards complete mineralization was less marked, with levels among 60-70%. Stepwise addition of H(2)O(2) was also tested.     

Heterogeneous catalytic wet air oxidation of refractory organic pollutants in industrial wastewaters: a review

Catalytic wet air oxidation (CWAO) is one of the most economical and environmental-friendly advanced oxidation process. It makes a promising technology for the treatment of refractory organic pollutants in industrial wastewaters. Various heterogeneous catalysts including noble metals and metal oxides have been extensively studied to enhance the efficiency of CWAO. The present review is concerned about the literatures published in this regard. Phenolics, carboxylic acids, and nitrogen-containing compounds were taken as model pollutants in most cases, and noble metals such as Ru, Rh, Pd, Ir, and Pt as well as oxides of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and Ce were applied as heterogeneous catalysts. Reports on their characterization and catalytic performances for the CWAO of aqueous pollutants are reviewed. Discussions are also made on the reaction mechanisms and kinetics proposed for heterogeneous CWAO and also on the typical catalyst deactivations in heterogeneous CWAO, i.e. carbonaceous deposits and metal leaching.     

Catalytic wet air oxidation of chlorophenols over supported ruthenium catalysts

A series of noble metal (Pt, Pd, Ru) loaded zirconia catalysts were evaluated in the catalytic wet air oxidation (CWAO) of mono-chlorophenols (2-CP, 3-CP, 4-CP) under relatively mild reaction conditions. Among the investigated noble metals, Ru appeared to be the best to promote the CWAO of CPs as far as incipient-wetness impregnation was used to prepare all the catalysts. The position of the chlorine substitution on the aromatic ring was also shown to have a significant effect on the CP reactivity in the CWAO over 3wt.% Ru/ZrO(2). 2-CP was relatively easier to degradate compared to 3-CP and 4-CP. One reason could be the higher adsorption of 2-CP on the catalyst surface. Further investigations suggested that 3wt.% Ru/ZrO(2) is a very efficient catalyst in the CWAO of 2-CP as far as high 2-CP conversion and TOC abatement could still be reached at even lower temperature (393K) and lower total pressure (3MPa). Additionally, the conversion of 2-CP was demonstrated to increase with the initial pH of the 2-CP solution. The dechlorination reaction is promoted at higher pH. In all cases, the adsorption of the reactants and the reaction intermediates was shown to play a major role. All parameters that would control the molecule speciation in solution or the catalyst surface properties would have a key effect.     

Boron removal from aqueous solutions by activated carbon impregnated with salicylic acid

In this study, the removal of boric acid from aqueous solution by activated carbon impregnated with salicylic acid was studied in batch system. pH, adsorbent amount, initial boron concentration, temperature, shaking rate and salicylic acid film thickness were chosen as parameters. Boron removal efficiencies increased with increasing adsorbent amount, temperature and pH, decreasing initial boron concentration. As thickness of salicylic acid film on activated carbon becomes thin up to 0.088nm, the efficiency increased, and then, the efficiency decreased with becoming thinner than 0.088nm of salicylic acid film. Shaking rate was no effect on removal efficiency. In result, it was determined that the use of salicylic acid as an impregnant for activated carbon led to the increase of the amount of boron adsorbed. A lactone ring, being the most appropriate conformation, forms between boric acid and -COOH and -OH groups of salicylic acid.     

Persulfate oxidation of MTBE- and chloroform-spent granular activated carbon

Activated persulfate (Na₂S₂O₈) regeneration of methyl tert-butyl ether (MTBE) and chloroform-spent GAC was evaluated in this study. Thermal-activation of persulfate was effective and resulted in greater MTBE removal than either alkaline-activation or H₂O₂-persulfate binary mixtures. H₂O₂ may serve multiple roles in oxidation mechanisms including Fenton-driven oxidation, and indirect activation of persulfate through thermal or ferrous iron activation mechanisms. More frequent, lower volume applications of persulfate solution (i.e., the persulfate loading rate), higher solid/solution ratio (g GAC mL⁻¹ solution), and higher persulfate concentration (mass loading) resulted in greater MTBE oxidation and removal. Chloroform oxidation was more effective in URV GAC compared to F400 GAC. This study provides baseline conditions that can be used to optimize pilot-scale persulfate-driven regeneration of contaminant-spent GAC.     

通过再活化浸渍金属盐的活性炭来发展中孔结构

研究了在椰子壳活性炭上浸渍金属盐（硝酸铁和硫酸铁）后，在二氧化碳气氛中催化活化对中孔结构的影响。发现硝酸铁对活性炭比表面积（-1930m^2／g）的增加和中孔结构（-10nm）的发展更有效。改性活性炭具有发达的中孔结构，显示了更大的维生素B12吸附容量（是改性前的5倍～8倍）和更快的吸附速度。中孔结构的发展基于三个方面的原因：（1）在活化过程中，浸渍在活性炭微孔内的金属盐分解所释放的氧化性气体与微孔碳壁反应，扩大了孔径；（2）在高温下，来自于金属盐的金属氧化物被碳还原，扩大了孔径；（3）在金属铁存在下，碳壁被催化活化，大大提高了活性炭的中孔率。由此提供了一种廉价的从商业活性炭制备中孔活性炭的有效途径。