Catalytic Wet Oxidation Process Research Articles

Treatment of Dyes Wastewater by the Catalytic Wet Persulfate Oxidation Process in Reactors Using Red Mud Combined with Biochar as Catalyst

Treatment of Dyes Wastewater by the Catalytic Wet Persulfate Oxidation Process in Reactors Using Red Mud Combined with Biochar as Catalyst

Removal efficiency and reaction kinetics of phenolic compounds in refinery wastewater by nano catalytic wet oxidation

A novel nano-catalyst based on iron oxide (MnO2/Fe2O3) was developed to promote wet oxidation of phenol. MnO2 was doped in Fe2O3 matrix to prepare composite nano-catalyst with different doping percentage (0, 2 and 5%). The catalytic phenol oxidation was conducted under different reaction temperatures and residence times. To evaluate the optimal kinetic parameters aiming to maximize phenol removal under the optimal conditions for the catalytic wet phenol oxidation process, modeling was applied on the batch reactor using the novel synthesis nano-catalyst (MnO2/Fe2O3) and the model developed was fed with the experimental data. gPROMS package was used to model the process of phenol oxidation and to optimize the experimental data. The error predicted between the simulated and experimental data was less than 5%. The optimal operating conditions were 294 min residence time, 70oC reaction temperature, and 764 ppm initial concentration of phenol over the prepared 5% MnO2/Fe2O3. Running of wet oxidation of phenol under the optimal operating conditions resulted in 98% removal of phenol from refinery wastewater.

Catalytic Wet Oxidation of Glucose over Oxidized Transition Metal and Alloy Catalysts

AbstractThe catalytic wet oxidation process was used to study the degradation of carbohydrates in wastewater with glucose as a model compound. The transition metals Co and Mo were transformed into their insoluble metal oxide forms, Co3O4 and MoO3. A novel catalyst was prepared by using a CuNiIn alloy, which was oxidized at 700 °C to generate an insoluble CuNiIn mixed oxide. Wet oxidation reactions were performed at 150–210 °C for 60 min at 20 bar O2 pressure. The catalytic performance of the CuNiIn oxide powder reached a reduction in chemical oxygen demand of > 80 %. Molybdenum and cobalt were highly leached into the reaction media, confirming CuNiIn oxide as the best catalyst used in terms of its performance and acetic acid production.

Use of heterogeneous activated carbon supported copper catalyst for catalytic wet oxidation of biomethanated spent wash: Reaction kinetics, catalyst stability, catalyst deactivation kinetics and biochemical methane potential

In the present study, the potential of activated carbon (AC) supported copper catalyst was investigated during catalytic wet oxidation (CWO) of pretreated high strength biomethanated spent wash (BMSW) stream which is originated from alcohol distillery. Prior to wet oxidation (WO) treatment, the BMSW was centrifuged to remove suspended solids. During CWO treatment at 220 °C temperature, the chemical oxygen demand and color removals of 72% and 97%, respectively, were observed from the centrifuged BMSW (catalyst dose = 3.4 g L−1, reaction time = 3 h). The analysis of treated liquid samples confirmed the formation of acetic acid in large concentrations which is one of the major precursors of methane during post anaerobic treatment. The kinetic expressions for WO and CWO processes were also developed using initial rate method. However, the recovered and regenerated catalyst could only be reused twice in CWO runs. The biochemical methane potential (BMP) test results showed significant production of biogas from the treated BMSW. Based on the findings, it can be inferred that the CWO of BMSW can be a potential treatment method before its disposal in the environment.

Optimization of catalytic wet oxidating fulvic acid with zero-valent copper chitosan activated carbon ball as the catalyst

The degradation efficiency of fulvic acid (FA) was investigated in the catalytic wet oxidation process (CWPO) by zero-valent copper chitosan activated carbon ball (ZVC/CTS-ACB). Characterization of ZVC/CTS-ACB shows that zero-valent copper was loaded successfully on the chitosan activated carbon. Plackett–Buiman (PB) design and response surface methodology (RSM) were employed to determine the influence factors and the optimum processing parameters. The model was well fitted to the actual data and the correlation coefficients of R2 and R2-adj were 0.9359 and 0.9039, respectively. Under the obtained optimum conditions for FA degradation: temperature = 94 °C and pH 3.8, the average FA removal by three replicate experiments was 93.02%, which has a high consistency to the RSM optimal target response of 93.86%. The comparison of catalytic performance showed that the addition of catalyst ZVC/CTS-ACS could increase the removal rate of FA, color number (CN) and TOC by 93.6%, 83.5% and 81.9% respectively. The high TOC removal rate indicated the good performance of the catalyst to FA mineralization. Additionally, the ICP analysis of copper ion leaching was only 0.08 mg/l after 5 repeated recycles of the catalyst, demonstrating the high stability of ZVC/CTS-ACB that is beneficial for the actual application.

Effective treatment of oily scum via catalytic wet persulfate oxidation process activated by Fe2+

Oily scum, a hazardous by-product of petroleum industry, need to be deposed urgently to reduce environmental risks. This paper introduces catalytic wet persulfate oxidation (CWPO) process in the treatment of oily scum to realize risk relief. Under the activation of heat and Fe2+, persulfate (PS) was decomposed into sulfate radicals and hydroxyl radicals, which played a major role on the degradation of petroleum hydrocarbons. The effects of wet air oxidation (WAO) and CWPO process on the degradation of oily scum were compared. In CWPO process, the total petroleum hydrocarbons (TPHs) content of oily scum was decreased from 92.63% to 16.75%, which was still up to 70.19% in WAO process. The degradation rate of TPHs in CWPO process was about 3.38 times higher than that in WAO process. The great performance of CWPO process was also confirmed by elemental analysis, which indicated that the C and H contents of oily scum were reduced significantly by CWPO process. These results indicated that CWPO process has high potential on the degradation of oily scum for environmental protection.

Investigation on the removal of H2S from microwave pyrolysis of sewage sludge by an integrated two-stage system.

In this study, an integrated two-stage system, including the in-situ catalytic microwave pyrolysis (ICMP) and subsequent catalytic wet oxidation (CWO) processes, was proposed to remove H2S released from microwave-induced pyrolysis of sewage sludge. The emission profile and H2S removal from the pyrolysis of raw sewage sludge (SS) and sewage sludge spiked with conditioner CaO (SS-CaO) were investigated. The results showed that CaO played a positive role on sulfur fixation during the pyrolysis process. It was found that SS-CaO (10wt.%) contributed to about 35% of H2S removal at the first stage (ICMP process). Additionally, the CWO process was demonstrated to have promising potential for posttreatment of remaining H2S gas. At the Fe3+ concentration of 30g/L, the maximum H2S removal efficiency of 94.8% was obtained for a single Fe3+/Cu2+ solution. Finally, at the pyrolysis temperature of 800°C, 99.7% of H2S was eliminated by the integrated two-stage system meeting the discharge standard of China. Therefore, the integrated two-stage system of ICMP+CWO may provide a promising strategy to remove H2S dramatically for the biomass pyrolysis industry.

Honeycomb nano cerium oxide fabricated by vacuum drying process with sodium alginate

Nano cerium oxide (CeO2) with honeycomb structure were synthesized simply and rapidly by vacuum drying method with sodium alginate as the biological template agent, Ce(NO3)3·6H2O as cerium source. The composition, aperture size, specific surface area and morphology of the prepared samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), N2 adsorption-desorption and scanning electron microscopy (SEM). Simultaneously, the effects on the morphology of the samples, which were caused by the drying method and the concentration of sodium alginate, were investigated. The results indicate that the prepared samples were nano CeO2 with high crystallinity and uniform dispersion, most of which had mesoporous, macroporous and honeycomb structure. The specific surface area of CeO2 is 210.0 m2/g, and the average aperture is 12.77 nm. The prepared samples can act as catalyst in the catalytic wet oxidation process for the treatment of high concentration organic wastewater, and the COD removal rate could exceed 90%.

Catalytic oxidation of pulping effluent by activated carbon-supported heterogeneous catalysts

ABSTRACTThe present study deals with the non-catalytic and catalytic wet oxidation (CWO) for the removal of persistent organic compounds from the pulping effluent. Two activated carbon-supported heterogeneous catalysts (Cu/Ce/AC and Cu/Mn/AC) were used for CWO after characterization by the following techniques: temperature-programmed reduction, Fourier transform infrared spectroscopy and thermo-gravimetric analysis. The oxidation reaction was performed in a batch high-pressure reactor (capacity = 0.7 L) at moderate oxidation conditions (temperature = 190°C and oxygen pressure = 0.9 MPa). With Cu/Ce/AC catalyst, the maximum chemical oxygen demand (COD), total organic carbon (TOC) and lignin removals of 79%, 77% and 88% were achieved compared to only 50% removal during the non-catalytic process. The 5-day biochemical oxygen demand (BOD5) to COD ratio (a measure for biodegradability) of the pulping effluent was improved to 0.52 from an initial value of 0.16. The mass balance calculations for solid recovered after CWO reaction showed 8% and 10% deduction in catalyst mass primarily attributed to the loss of carbon and metal leaching. After the CWO process, carbon deposition was also observed on the recovered catalyst which was responsible for around 3–4% TOC reduction.

Catalytic Wet Peroxide Oxidation of Olive Oil Mill Wastewater over Zeolite Based Catalyst

Olive oil mill wastewater (OOMW) – the liquid waste generated in the process of olive oil extraction contains significant amounts of phenolics. Their high polluting charges that are measured in BOD5 and COD levels up to 35 g dm -3 and the presence in the concentrations up to 10 g dm -3 are of special concern to the environment. These compounds make OOMW biorefractory in nature and unsusceptible to a conventional biological treatment. Reducing their toxicity prior to the conventional treatment is therefore of the uttermost importance. The non-selective catalytic wet peroxide oxidation (CWPO) process is one of the methods that can be used for that purpose in practice. With the use of catalysis the process can be successfully operated under mild conditions with low energy consumption. In this work, the influence of the reaction parameters and the catalyst preparation method on the activity and stability of zeolite (13X) based catalyst in the reaction of hydrogen peroxide oxidation of phenolic compounds present in wastewater from industry for processing olives and olive oil was examined. The reaction was carried out in a batch reactor at different stirring speed, particle sizes, temperatures, catalyst loadings and initial concentrations of hydrogen peroxide. The catalyst Cu/13X was prepared by ion exchange of commercial 13X zeolite. Characterization of the catalyst included N2 physisorption, XRD, TPD-CO2 and FTIR-Pyridine desorption. In order to increase the catalyst’s stability, it was subjected to a thermal post-synthesis treatment at 1273 K. The justification for post synthesis treatment of the catalyst is reflected in the enhanced stability of the catalytically active material which is removed from the carrier, i.e. larger resistance of Cu/13X - K1273 to leaching. Examining the effect of the mixing rates and catalyst particle sizes on reaction rate it was found that the reaction is carried out in the kinetic regime, with the total phenols content diminished by more than 80 % with a 20 % decrease in wastewater’s TOC content and leaching below 3 wt. %.

Optimal Decolorization Efficiency of Reactive Red 3 by Fe-RH-MCM-41 Catalytic Wet Oxidation Coupled with Box-Behnken Design

The reactive red 3 was degraded by catalytic wet oxidation process over Fe-RH-MCM-41 prepared by Direct Hydrothermal Technique (DHT) at Si/Fe molar ratio of 10 using silica from rice husk. The extended reaction conditions were studied as a function of reaction temperatures, initial H2O2 concentrations and initial pH of solutions designed by Box-Behnken design (BBD) based on Response Surface Methodology (RSM) to achieve the optimal condition and interaction of independent variables. The characterizations of catalyst were studied by XRD, BET surface area and TEM to explain the morphology of surface and to confirm the hexagonal structure. The results showed the 2theta peak can be indexed to hexagonal lattice that also confirmed by TEM result and surface area about 650 m2/g. All of independent variables showed significant on the degradation of reactive red 3 except for initial H2O2 concentration.

Efficacy of Chemical Oxidation and Coagulation for COD and Color Reduction from Pulp Mill Effluent

AbstractIn a pulp and paper mill, the highly colored wastewater generated from the pulping process requires pretreatment before the biological purification process because of the presence of recalcitrant lingo-cellulosic compounds. For the present study, the black liquor was prepared in the laboratory by digesting the sugarcane baggase using the soda process, which was further diluted before use in the experimental study. The wastewater [pH=13.0, chemical oxygen demand (COD)=5,120 mg/L] was treated by two processes: wet oxidation (WO) (both noncatalytic and catalytic) and coagulation. Catalytic WO (CWO) experiments were conducted in the presence of 60% CuO/40% CeO2 at temperatures ranging from 130 to 170°C and total pressures of 0.95 MPa. During the CWO process, the maximum COD and color removals were found to be approximately 51 and 71%, respectively. Coagulation followed by noncatalytic WO exhibited the best performance with overall COD and color reductions of approximately 77.5 and 87%, respectively. ...

Wet Oxidation: A Promising Option for the Treatment of Pulp and Paper Mill Wastewater

Wet oxidation (WO) is used to degrade persistent organic or inorganic impurities present in industrial wastewater. The process utilizes severe oxidation conditions (i.e., high temperature and pressures) to achieve the efficient degradation of pollutants. To obtain high degradation at lower operation conditions, catalytic WO process is being suggested. The wastewater generated from a pulp and paper mill contains several recalcitrant compounds like lignin, hemi-cellulose, phenols, sulfides etc. Therefore, pulp and paper mill effluent have low biodegradability and are not amenable for conventional biological process. With the implementation of stringent regulations, pulp and paper mill operators need a cleaner disposal route for the wastewater. In this mini-review, the results obtained from the recently published studies on WO treatment for pulp and paper mill effluent are compiled and presented. Finally, the recommendations for the future work are also given.

A study on ruthenium-based catalysts for pharmaceutical wastewater treatment

Ruthenium-based catalysts were prepared by a saturation-dip method. Their catalytic activity was evaluated by a catalytic wet oxidation (CWO) process. The ruthenium-based catalysts were used to purify organic pharmaceutical wastewater with high concentration pyridine and pyridine derivatives that have high chemical oxygen demand (COD). In the CWO process, organic pharmaceutical wastewater was continuously pumped into fixed-bed reactors filled with Ru-based catalysts, while the organic components in wastewater were catalytically degraded by oxygen at high temperatures and pressures (temperature, 170-300 degrees C; pressure, 1.0-10 MPa). The experimental results showed that the prepared catalysts could effectively purify pharmaceutical wastewater with high concentration organic components, which are difficult to degrade biochemically, and that the removal rates of both COD and total nitrogen were over 99%.

Catalytic Properties of Cu/13X Zeolite Based Catalyst in Catalytic Wet Peroxide Oxidation of Phenol

Copper bearing 13X zeolite was prepared from commercial 13X zeolite via ion-exchange with copper acetate solutions. After the incorporation of copper, Cu/13X catalyst was exposed to post synthesis thermal treatment at different temperatures. The prepared catalysts were characterized by XRD and FTIR, while the adsorption techniques were used for the measurement of the specific surface area and pore volume. The catalytic tests were carried out in a stainless steel Parr reactor in batch operation mode at atmospheric pressure in temperature range from 333 to 353 K. Influence of postsynthesis thermal treatment and reaction temperature on activity and stability of prepared catalysts in the catalytic wet oxidation process with hydrogen peroxide as oxidant was investigated. The experimental results showed that total degradation of phenol can be achieved under mild operating conditions at temperatures bellow 353 K. All catalysts exhibited higher activity in terms of hydrogen peroxide and phenol abatement with the increasing temperature of the reaction. The postsynthesis thermal treatment resulted in more stable catalyst with respect to stability of both catalysts’ active metal component (copper) and support, while the activity of catalysts in terms of TOC conversion remained unaltered.

Catalytic Wet Oxidation of Paper Mill Debarking Water: Factors Affecting it

The research seeks to investigate the effect of catalyst (1-wt % Platinum on activated carbon) on the wet oxidation process of treating paper mill effluent. The study also assesses the effect of temperature, oxygen partial pressure and initial Chemical Oxygen Demand (COD) concentration of debarking wastewater on the contaminants during the catalytic wet oxidation process. Catalytic wet oxidation process was studied at 120-180°C temperature, 0-10 bar oxygen partial pressure, 0-1 g/L catalyst concentration and 1000-3000 mg/L initial COD concentrations. Responses such as COD, Total Organic Carbon (TOC), Color, Lignin/Tannin, Biochemical Oxygen Demand (BOD) and pH were measured and analyzed. In the study, it was realized that changes in temperature, oxygen partial pressure, catalyst concentration and initial COD influenced the oxidation process with the best combination occurring at a temperature of 180°C, 10 bar oxygen partial pressure, 1 g/L catalyst concentration and 3000 mg/L initial COD concentration. At these conditions; 74% of COD, 97% of lignin/tannin, 54% of TOC and 90% of color were removed from the wastewater.

Catalytic Wet Oxidation of Wastewater from Pulping Industry Using Solid Waste Containing Iron Oxides

The pulping industry generates great quantities of wastewaters (WW), where a small amount of black liquor accounts for more than 90% of its entire manufacturing process load in organics. Treatment of the black liquor from pulping manufacture in ThaiNguyen province (Vietnam) by catalytic wet oxidation (CWO) under mild reaction conditions (150–180°C, 15 bar) using solid wastes containing iron oxide as heterogeneous catalysts is communicated herein. These solid wastes have been found to be active in the oxidation of pollutants in the black liquor and show a high application potential in CWO processes for the treatment of this kind of industrial wastewater.

Treatment of Ammonia by Catalytic Wet Oxidation Process Over Platinum-Rhodium Bimetallic Catalyst in a Trickle-Bed Reactor: Effect of pH

This work adopted aqueous solutions of ammonia for use in catalytic liquid-phase reduction in a trickle-bed reactor with a platinum-rhodium bimetallic catalyst, prepared by the co-precipitation of chloroplatinic acid (H2PtCl6) and rhodium nitrate [Rh(NO3)3]. The experimental results demonstrated that a minimal amount of ammonia was removed from the solution by wet oxidation in the absence of any catalyst, while approximately 97.0% of the ammonia was removed by wet oxidation over the platinum-rhodium bimetallic catalyst at 230 degrees C with an oxygen partial pressure of 2.0 MPa. The oxidation of ammonia has been studied as a function of pH, and the main reaction products were determined. A synergistic effect is manifest in the platinum-rhodium bimetallic structure, in which the material has the greatest capacity to reduce ammonia. The reaction pathway linked the oxidizing ammonia to nitric oxide, nitrogen, and water.

ZnO/MoO 3 mixed oxide nanotube: A highly efficient and stable catalyst for degradation of dye by air under room conditions

As a continuation of our work to develop catalysts with high activity for catalytic air wet oxidation process under mild conditions, degradation of wastewater containing 0.3 g/L Safranin-T (ST) by air oxidation over ZnO/MoO 3 nanotube catalyst was studied. It was found the decolorization efficiency and the chemical oxygen demand (COD) removal of ST reached above 98% and 95%, respectively, within 18 min at room temperature and atmospheric pressure. And the organic pollutants were totally mineralized to simple inorganic species such as HCO 3 −, Cl − and NO 3 −, while the total organic carbon (TOC) decreased 99.3%. The structure and morphology of the catalyst after ten cycling runs showed that the catalyst was stable under such operating condition and the leaching test showed negligible leaching effect. This ZnO/MoO 3 nanotube is proved to be an active and stable heterogeneous catalyst in CWAO of ST under extremely mild conditions.

Wet Oxidation—An Option for Enhancing Biodegradability of Leachate Derived From Municipal Solid Waste (MSW) Landfill

The present study reports the treatment of municipal solid waste (MSW) derived landfill leachate (initial pH = 7.82 and chemical oxygen demand (COD) = 6400 mg L−1) using catalytic wet oxidation (WO) process. The reaction was performed under moderate conditions (110−150 °C temperature and 0.7 MPa total pressures) in the presence of a CuSO4 catalyst. The effect of the promoter (Na2SO3) was also seen on the COD removal. The results were compared with that obtained for Fe2+ and H2O2 combination. Among all tested combinations, (CuSO4 + Na2SO3 + air) exhibited the best performance with ∼90% COD reduction at 150 °C temperature and 0.7 MPa pressures. Under these conditions, the biodegradability of the treated effluent was improved to 0.66 (from an initial value of 0.38). The average oxidation state of carbon (AOSC) value and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of carboxylic acids in the treated effluent.