Showing papers on "Wet oxidation published in 2015"
TL;DR: In this article, a review on the traditional techniques and recent advances in the separation of phenol from its contaminated streams is carried out, and the most commonly used methods classified based on the phenol concentrations (high, medium, and low), and also, their advantages and disadvantages that should be considered in the design of industrial wastewater treatment systems are discussed.
Abstract: The toxicity of phenol even at low concentrations in industrial effluents is high enough to meet its needs for separation. In this paper, a review will be carried out on the traditional techniques and recent advances in the separation of phenol from its contaminated streams. The most commonly used methods classified based on the phenol concentrations (high, medium, and low), and also, their advantages and disadvantages that should be considered in the design of industrial wastewater treatment systems will be discussed. Finally, the best methods will be suggested for each concentration range at the influent and, of course, that is allowable in the final effluent. The survey results recommended that biodegradation, chemical, electrochemical, and photocatalytic oxidation, solid phase extraction, ozonation, reverse osmosis/nanofiltration, and wet air oxidation are useful methods in low phenol concentrations, whereas liquid–liquid extraction, pervaporation, membrane-based solvent extraction, adsorption...
281 citations
TL;DR: The main physico-chemical processes for nitrogen removal from wastewaters, considering both those that have been long known and still widely applied at the industrial scale, and those that are still at the research level, were examined in this paper.
Abstract: The paper examines the main physico-chemical processes for nitrogen removal from wastewaters, considering both those that have been long known and still widely applied at the industrial scale, and those that are still at the research level. Special attention is paid to the latest technological developments, as well as to operational problems and fields of application. The processes considered are briefly summarized as follows: ammonia air and steam stripping; ammonia vacuum distillation; ammonia precipitation as struvite; ammonia and nitrate removal by selected ion exchange; breakpoint chlorination; chloramine removal by selected activated carbon; ammonia adsorption on charcoal; chemical reduction of nitrate; advanced oxidation processes to convert ammonia and organic-N into nitrogen gas or nitrate. Special attention is given to advanced oxidation processes, as great research efforts are currently addressed to their implementation. These specifically include ozonation, peroxon oxidation, catalytic wet air oxidation, photo-catalytic oxidation and electrochemical oxidation.
108 citations
TL;DR: In this paper, a review on the traditional techniques and recent advances in the separation of phenol from its contaminated streams is carried out, and the most commonly used methods classified based on the phenol concentrations (high, medium, and low), and also, their advantages and disadvantages that should be considered in the design of industrial wastewater treatment systems are discussed.
Abstract: The toxicity of phenol even at low concentrations in industrial effluents is high enough to meet its needs for separation. In this paper, a review will be carried out on the traditional techniques and recent advances in the separation of phenol from its contaminated streams. The most commonly used methods classified based on the phenol concentrations (high, medium, and low), and also, their advantages and disadvantages that should be considered in the design of industrial wastewater treatment systems will be discussed. Finally, the best methods will be suggested for each concentration range at the influent and, of course, that is allowable in the final effluent. The survey results recommended that biodegradation, chemical, electrochemical, and photocatalytic oxidation, solid phase extraction, ozonation, reverse osmosis/nanofiltration, and wet air oxidation are useful methods in low phenol concentrations, whereas liquid–liquid extraction, pervaporation, membrane-based solvent extraction, adsorption...
68 citations
TL;DR: The feasibility of a multi-barrier treatment for the regeneration of synthetic industrial wastewater (SIWW) was evaluated and the wastewater toxicity was studied using Vibrio fischeri and Sparus aurata larvae.
64 citations
TL;DR: In this paper, the catalytic performance of Ru and Pt supported on TiO 2 − x ǫ wt% CeO 2 was studied in catalytic wet air oxidation (CWAO) of phenol at 160°C and 20 bar of pure oxygen pressure.
62 citations
TL;DR: In this paper, a modified Hummers method using natural graphite as primary precursor was used, followed by chemical and thermal reduction processes, and finally ball milled with urea or melamine.
60 citations
59 citations
TL;DR: Pt/TiO2-Ce catalysts were synthesized with different concentrations of Ce at 1, 3, 5 and 10% for being used in catalytic wet air oxidation (CWAO) of aqueous solution of phenol (1000ppm) as mentioned in this paper.
58 citations
TL;DR: In this article, a digested sludge consisting of primary and secondary sludges was subjected to 60min wet oxidation at temperatures ranging between 220 and 240°C and oxygen to biomass ratios of 1:1-2:1.
57 citations
TL;DR: The resulting Si/Al2O3 foam anodes exhibit outstanding cycling stability, excellent rate capability, and excellent cycling stability after 300 cycles at the C/5 rate.
55 citations
TL;DR: In this paper, Nitrogen-doped carbon xerogels were tested as metal-free catalysts for the mineralization of oxalic acid by ozonation and by wet air oxidation.
TL;DR: In this article, high active and selective supported noble metal catalysts were studied in the catalytic wet air oxidation of ammonia and only nitrites and molecular nitrogen were detected as primary products.
TL;DR: In this paper, a WO treatment was performed on process waters obtained from hydrothermal carbonization (HTC) of sucrose, cellulose, wood, and brewer's spent grains with oxygen at 3MPa and temperatures of 120-200°C. The aim was to reduce the dissolved organic carbon (DOC) content and chemical oxygen demand (COD) of the process water in order to reduce toxicity, enhance biodegradability and supply heat to improve the preceding HTC process.
TL;DR: In this article, the role of acid-base properties on CWAO reactions (acetic acid, aniline and phenol) is reviewed. But, the acid base properties of the supports are not considered.
TL;DR: In this article, the performance of different Ce x Zr 1 − x O 2 mixed oxides, prepared by co-precipitation and Ce xZr 1−x O 2 -supported platinum and ruthenium catalysts, synthesised by impregnation, were investigated in the catalytic wet air oxidation (CWAO) of succinic acid at 190°C under 50 bar total pressure.
Abstract: Different Ce x Zr 1 − x O 2 mixed oxides, prepared by co-precipitation and Ce x Zr 1 − x O 2 -supported platinum and ruthenium catalysts, synthesised by impregnation, were investigated in the catalytic wet air oxidation (CWAO) of succinic acid at 190°C under 50 bar total pressure. The catalytic activity of these solids was demonstrated to be strongly influenced by the Ce content in the Ce x Zr 1 − x O 2 support. The higher the Ce content in the mixed oxide support, the higher the succinic acid removal rate. The ruthenium catalysts exhibited the best performances in terms of succinic conversion at a given time of reaction; but, when the activity was expressed per mole of metal, the platinum catalysts were observed to perform better (435 mol acid h −1 mol Pt −1 ). Upon recycling reactions, the Ce 0.9 Zr 0.1 O 2 support and the 0.5 wt% Ru/Ce 0.9 Zr 0.1 O 2 catalyst maintained some good performances even though the conversion of succinic acid gradually decreased. It was demonstrated that the leaching of the metallic phase, the formation of carbonaceous deposits on the catalyst surface and the decrease of the specific surface area did not play a major role in the deactivation, which was more likely related to modifications of the chemical state of the active phase. Finally, the reaction was shown to be +0.1 order with respect to succinic acid and +0.4 order with respect to oxygen, indicating some major changes in the reaction kinetics and mechanism of the reaction over such catalysts containing ceria.
TL;DR: Nano-structured Ce1−xFexO2 mixed oxides with different Fe loading have been synthesized via co-precipitation route and were evaluated as heterogeneous catalysts for catalytic wet air oxidation of wastewater as discussed by the authors.
TL;DR: In this article, a two-step pathway was proposed for the formation of value-added aromatic aldehydes from lignin via degradation of acetoderivatives, which could become a potential new route for the recovery of value added products.
TL;DR: The efficiency of the materials as environmental oxidation catalysts were tested with respect to destruction of 4-chlorophenol in water in the presence of hydrogen peroxide and the catalysts performed well at the pH of aqueous 4-CP solution.
TL;DR: In this article, the effect of temperature and oxygen partial pressure on the p-nitrophenol degradation process and porosity regain of activated carbons was analyzed under subcritical conditions by means of wet oxidation.
Abstract: Activated carbons saturated with p-nitrophenol were regenerated under subcritical conditions by means of wet oxidation, analyzing the effect of temperature (160–200 °C) and oxygen partial pressure (3–12 bar). The research intended to achieve two main objectives: (a) to restore the carbons adsorption performance and (b) to get insight about the p-nitrophenol oxidation process and how it can be influenced by the presence of the adsorbent. Based on the contaminant oxidation mechanisms, which was defined as a series of radical processes, a kinetic model was developed. The model was created by COMSOL MULTIPHYSICS software, and allowed obtaining characteristical parameters. Further comparison between theoretical and experimental results showed the suitability of the model in the whole range of experimental domain. Subsequent application of this model to regeneration experiments confirmed the need of developing a new model in the latter case, since the presence of carbon involved a significant modification of kinetic parameters, which was related to the catalyzing action of the adsorbent. It was also found that both temperature and pressure affect the p-nitrophenol degradation process as well as porosity regain of the carbons. Values of p-nitrophenol regeneration efficiency up to 87% for the highest values of temperature and oxygen partial pressure.
TL;DR: The Catalytic Wet Air Oxidation (CWAO) of phenol using copper oxide catalysts supported by γ-Al2O3, TiO2, and pillared clay was evaluated to identify which of these catalysts was the most appropriate for this reaction.
Abstract: The Catalytic Wet Air Oxidation (CWAO) of phenol using copper oxide catalysts supported by γ-Al2O3, TiO2, and pillared clay was evaluated to identify which of these catalysts was the most appropriate for this reaction. The CuO/PILC, CuO/γ-Al2O3 and CuO/TiO2 catalysts were the most successful at removing phenol and resulted in more than 96% conversion. Among these catalysts, CuO/γ-Al2O3 produced the largest amount of CO2, the lowest amount of intermediate products and the lowest amount of copper leaching. These results showed that the CuO/γ-Al2O3catalyst was the best for the end of the reaction. However, the methods used in this study did not allow us to identify the most appropriate reaction time (or catalyst). An alternative approach for this problem was to quantify the costs for each reaction time. Using this approach, the CuO/γ-Al2O3 catalyst was the most economically favorable catalyst when it was used during the first hour of the reaction.
21 Apr 2015-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, the effects of temperature, oxidation time, and oxygen concentration on the conversion of sulfur by wet oxidation in the Bayer process were investigated at length, and it was shown that active sulfur S2− and S2O3 − 2− in sodium aluminate solution can be converted completely by wet oxidization during the digestion process, thus the effect of S2 − and S 2O3−− 2− on alumina product quality are eliminated.
Abstract: In this paper, the effects of temperature, oxidation time, and oxygen concentration on the conversion of sulfur by wet oxidation in the Bayer process were investigated at length. The results show that active sulfur S2− and S2O3
2− in sodium aluminate solution can be converted completely by wet oxidation during the digestion process, thus the effects of S2− and S2O3
2− on alumina product quality are eliminated; increased temperature, oxidation time, and oxygen concentration are conducive to conversion of S2− and S2O3
2−. At the same time, part of the organic carbon in the sodium aluminate solution is also oxidized by wet oxidation, and the color of the sodium aluminate solution noticeably fades.
TL;DR: In this article, the influence of pH, temperature and concentrations on the homogeneous catalytic oxidation of aqueous phenol at high concentrations (0.0467 −1.4 −3 −3 ) was studied.
TL;DR: The model was shown to be accurate in predicting the concentrations of each component, and produced good results when applied to a plant 500 times larger in size, and demonstrated the usefulness of the model by suggesting optimum operating conditions such that volatile fatty acids were maximised.
Abstract: A kinetic study of wet air oxidation pretreatment and induced biodegradability enhancement of a model complex wastewater was studied in the temperature range of 150–200 °C, air pressure 6–12 bar (0.6–1.2 MPa), reaction time 15–120 min and agitation 150–500 rpm. Based on free radical mechanism, a kinetic model is postulated where the electron transfer from air (oxygen) to the substrate was assumed to initiate the free radical generation. According to the model, reaction orders for wet oxidation pretreatment (in terms of COD degradation rate) were found to be 1.0, 0.42 and 0.22 for COD and oxygen partial pressure respectively. The WAO pretreatment led to reorientation and/or breakdown of complex biologically recalcitrant molecules with 3–5-fold increase in biodegradability index. The kinetics of biodegradability index enhancement was successfully correlated with COD degradation kinetics.
TL;DR: This work addresses the wet air oxidation (WAO) process for pre-treatment of phenolic wastewater effluents with the aim to increase biodegradability prior to a subsequent anaerobic stage.
24 Sep 2015
TL;DR: In this article, a simple method to lower Fe(VI) preparation cost by recycling iron from a spent steel pickling liquid as an iron source for preparing potassium ferrate with a wet oxidation method was proposed.
Abstract: Potassium ferrate (K2FeO4) is a multi-functional green reagent for water treatment with considerable combined effectiveness in oxidization, disinfection, coagulation, sterilization, adsorption, and deodorization, producing environment friendly Fe(III) end-products during the reactions. This study uses a simple method to lower Fe(VI) preparation cost by recycling iron from a spent steel pickling liquid as an iron source for preparing potassium ferrate with a wet oxidation method. The recycled iron is in powder form of ferrous (93%) and ferric chlorides (7%), as determined by X-ray Absorption Near Edge Spectrum (XANES) simulation. The synthesis method involves three steps, namely, oxidation of ferrous/ferric ions to form ferrate with NaOCl under alkaline conditions, substitution of sodium with potassium to form potassium ferrate, and continuously washing impurities with various organic solvents off the in-house ferrate. Characterization of the in-house product with various instruments, such as scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS), proves that product quality and purity are comparative to a commercialized one. Methylene blue (MB) de-colorization tests with in-house potassium ferrate shows that, within 30 min, almost all MB molecules are de-colorized at a Fe/carbon mole ratio of 2/1.
TL;DR: In this article, the effect of the main operating conditions, such as temperature (423 −483 K), pressure (2.0 −8.0 MPa), and pH (2 −11.0 ) on the degree of mineralization, biodegradability, toxicity and colour were analyzed.
TL;DR: In this paper, the effectiveness of an advanced sludge treatment technology (Wet Oxidation, WO) is presented by analyzing experimental studies at the lab scale and data collected during years of industrial-scale activities.
Abstract: In this article, the effectiveness of an advanced sludge treatment technology (Wet Oxidation, WO) is presented by analyzing experimental studies at the lab scale and data collected during years of industrial-scale activities. The data showed good performances of WO on COD and VSS removal efficiencies—about 65–70% and 95–98%, respectively—and the effect of operating parameters (i.e., temperature and reaction time) on process efficiencies was highlighted. The energy balance of the WO systems indicated that about 90% of the energy entering the system may be recovered. Finally, a techno-economic assessment showed that WO can be a suitable solution for sludge treatment and minimization.
TL;DR: The authors had successfully demonstrated the application of response surface methodology (RSM) with the Box-Behnken design (BBD) as a means of elucidating the complicated interaction effects between parameters.
Abstract: In this study, 10% CuO/Al2O3 catalyst was used in a catalytic wet-air oxidation process to remove chemical oxygen demand (COD) and color from experimentally designed wastewater containing lignin. The catalyst was prepared using an impregnation method and was characterized by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), and Brunauer-Emmett-Teller method (BET) for surface area before use. A series of Box-Behnken design (BBD) experiments were used to identify the conditions (temperature, pressure, reaction time, and catalysts) necessary for the COD removal process. The predicted model had R2 and R2adj correlation coefficients of 0.98 and 0.97, respectively. Pressure only and the interaction effect between temperature and pressure were found to have a significant effect on COD removal (both confidence interval [CI] 95%). Finally, response surface methodology (RSM)-optimized results suggested that 92% of COD could be removed in 1 L of experimental wastewater with a lignin concentration 350 g/...
TL;DR: In this paper, the effectiveness of two homogeneous copper salts (nitrate and sulfate) as catalysts during batch WO process conducted under mild temperature and pressures (i.e., 120°C and oxygen pressure = 0.5 MPa).
Abstract: Several process industries discharge wastewater with enormous amount of toxic phenolic compounds. Wet oxidation (WO) is considered among the potential cleaner treatment methods for such waste streams. The present study demonstrates the effectiveness of two homogeneous copper salts (nitrate and sulfate) as catalysts during batch WO process conducted under mild temperature and pressures (i.e., 120 °C and oxygen pressure = 0.5 MPa). The catalytic oxidation showed around 90 % reduction of phenol, chemical oxygen demand and total organic carbon from the wastewater within 2 h. The oxidation reaction pathway at mild conditions is also proposed based on the presence of intermediates/by-products. Fourier transform infrared spectroscopy confirmed the formation of polymerized compounds containing alcoholic/phenolic species. The inductively coupled plasma-atomic emission spectroscopy analysis revealed the presence of ~40 % of the total copper in sludge. The copper recovery from the treated wastewater and sludge and its reuse in the oxidation process should be studied in future.