Air Oxidation Process Research Articles

Rational Synthesis of Spongy Fe3N@N-Doped Carbon Nanorods with Controlled Topography and Porosity for Enhanced Energy Storage Anodes in Lithium-Ion Batteries.

Iron nitrides with the merits of high theoretical capacities, cost-effectiveness, and good electronic/ionic conductivity have been recognized as attractive anode candidates for lithium-ion batteries (LIBs). Carbon compositing, pore engineering, and nanostructure construction have proved to be effective strategies to prepare high-performance metal nitride anodes for LIBs. Herein, we synthesized a series of Fe3N-embedded and N-doped carbon nanorods (Fe3N@NCNR) with a hierarchical porous system and controllable topography by metal-catalyzed graphitization-nitridization of the Fe(III)-triazole framework (Fe-MOF) and thermal evaporation of the triblock copolymer F127 template assembled in Fe-MOF via hydrogen bonding interaction, followed by the air oxidation and urea-assisted ammonolysis processes. The Fe3N@NCNR as anodes for LIBs display extraordinary lithium storage capabilities with a high reversible capacity of 830 mA h g-1 at 0.1 C, a good rate performance of 576 mAh g-1 at 5 C, and a long-term cycling stability of 742 mA h g-1 over 600 cycles at 1 C. Such outstanding performance benefits from the spongy carbon nanorods with rich macropores for rapid electronic/ionic transport and effective accommodation of electrode volume expansion, abundant N-doped meso-/microporous carbon for the additional storage of Li+ via capacitive effect, and the efficient utilization of Fe3N nanoparticles uniformly distributed through carbon nanorods. Importantly, this work introduces an effective strategy to construct superior performance nitride anodes from MOF surfactants based on hydrogen bonding-driven interface self-assembly and provides insight into the preparation of highly efficient nanoarchitectures for Li+ storage.

The Influence of Au Loading and TiO2 Support on the Catalytic Wet Air Oxidation of Glyphosate over TiO2+Au Catalysts

This study aimed to explore the impact of varying amounts of added Au (0.5 to 2 wt.%) and the structural characteristics of anatase TiO2 supports (nanoparticles (TP, SBET = 88 m2/g) and nanorods (TR, SBET = 105 m2/g)) on the catalytic efficiency of TiO2+Au catalysts in eliminating the herbicide glyphosate from aqueous solutions via the catalytic wet air oxidation (CWAO) process. The investigation was conducted using a continuous-flow trickle-bed reactor. Regardless of the TiO2 support and the amount of Au added, the addition of Au has a positive effect on the glyphosate degradation rate. Regarding the amount of Au added, the highest catalytic activity was observed with the TP + 1% Au catalyst, which had a higher Schottky barrier (SB) than the TP + 2% Au catalyst, which helped the charge carriers in the TiO2 conduction band to increase their reduction potential by preventing them from returning to the Au. The role of glyphosate degradation product adsorption on the catalyst surface is crucial for sustaining the long-term catalytic activity of the investigated TiO2+Au materials. This was particularly evident in the case of the TR + 1% Au catalyst, which had the highest glyphosate degradation rate at the beginning of the CWAO experiment, but its catalytic activity then decreased over time due to the adsorption of glyphosate degradation products, which was favoured by the presence of strong acidic sites. In addition, the TR + 1% Au solid had the smallest average Au particle size of all analyzed materials, which were more easily deactivated by the adsorption of glyphosate degradation products. The analysis of the degradation products of glyphosate shows that the oxidation of glyphosate in the liquid phase involves the rupture of C–P and C–N bonds, as amino-methyl-phosphonic acid (AMPA), glyoxylic acid and sarcosine were detected.

Optimization of catalytic wet air oxidation process in microchannel reactor for TBBS wastewater treatment

ABSTRACT Catalytic wet air oxidation (CWAO) process is employed for the treatment of N-tert-butyl-2-benzothiazolesulfenamide (TBBS) wastewater in a microchannel reactor that enables continuous operation of the reaction and allows for thorough mixing of oxygen and pollutants. To achieve the optimal process performance, four key parameters of pressure, temperature, time, and the mass ratio of input oxygen to wastewater COD are optimized using both response surface methodology (RSM) and backpropagation artificial neural network (BP-ANN). According to the correlation coefficients of model results and experimental data, BP-ANN performs better than RSM in simulation and prediction. The analysis of variance in RSM shows that all parameters are significant for the obtained quadratic model, but their interactions with each other are not significant. Connection weights algorithm is used to determine the relative importance of these parameters for the process efficiency, and it is demonstrated that temperature is the most influential parameter with a relative importance of 35.61%, followed by pressure (29.74%), time (19.53%) and ROC (15.12%).

Chemically activated hydrochars as catalysts for the treatment of HTC liquor by catalytic wet air oxidation

Hydrothermal carbonization (HTC) is a highly efficient and valuable technology for treating wet solid wastes and producing solid carbon-based materials named hydrochar. In this work, a hydrochar coming from the HTC of an anaerobic digestion sludge of wastewater treatment plant was used to assess the influence of several activation agents, a base (KOH) and different chloride salts (FeCl3, ZnCl2, and CuCl2) with the exact molar quantities, to develop materials with enhanced surface area and potential inclusion of metal active species for application in wet air oxidation processes. The KOH as an activating agent increased the surface area of hydrochar up to ca. 1000 m2/g of BET surface area. The employment of CuCl2 and FeCl3 as activating agents allows Cu- and Fe-rich doped materials of remarkable surface areas with 49.1 and 42.5 wt% of each metal, respectively. Likewise, the catalytic behavior of the different synthesized carbon-based materials as metal-free and metal-doped catalysts was evaluated for the Catalytic Wet Air Oxidation (CWAO) of a HTC aqueous liquor from a HTC process of animal manure to produce a valuable stream of higher biochemical methane potential in anaerobic digestion. CWAO effluents increased the proportion of carboxylic acids as final by-products due to the oxidation of more complex organic compounds of the initial effluent (ketones, phenols, aromatics and olefins). The CWAO treatments improve the anaerobic digestion rate in biochemical methane potential tests, although the methane production was limited by the lower TOC concentration of the treated streams after CWAO. This research contributes to developing sustainable and efficient strategies for the HTC-liquor treatment, using its solid hydrochar as catalysts, closing the loop of a Circular Economy.

Treatment of Highly Alkaline Industrial Organic Raffinate Containing Pyridine and Its Derivatives by Coupling of Catalytic Wet Air Oxidation and Biological Processes

Treatment of Highly Alkaline Industrial Organic Raffinate Containing Pyridine and Its Derivatives by Coupling of Catalytic Wet Air Oxidation and Biological Processes

Investigation into Propolis Components Responsible for Inducing Skin Allergy: Air Oxidation of Caffeic Acid and Its Esters Contribute to Hapten Formation.

Propolis is a resin-like material produced by bees from the buds of poplar and cone-bearing trees and is used in beehive construction. Propolis is a common additive in various biocosmetics and health-related products, despite the fact that it is a well-known cause of contact allergy. Caffeic acid and its esters have been the primary suspects behind the sensitization potency of propolis-induced contact allergy. However, the chemical structures of the protein adducts formed between these haptens and skin proteins during the process of skin sensitization remain unknown. In this study, the reactivity of three main contact allergens found in propolis, namely, caffeic acid (CA), caffeic acid 1,1-dimethylallyl ester (CAAE), and caffeic acid phenethyl ester (CAPE), was investigated. These compounds were initially subjected to the kinetic direct peptide reactivity assay to categorize the sensitization potency of CA, CAAE, and CAPE, but the data obtained was deemed too unreliable to confidently classify their skin sensitization potential based on this assay alone. To further investigate the chemistry involved in generating possible skin allergy-inducing protein adducts, model peptide reactions with CA, CAAE, and CAPE were conducted and analyzed via liquid chromatography-high-resolution mass spectrometry. Reactions between CA, CAAE, and CAPE and a cysteine-containing peptide in the presence of oxygen, both in closed and open systems, were monitored at specific time points. These studies revealed the formation of two different adducts, one corresponding to thiol addition to the α,β-unsaturated carbonyl region of the caffeic structure and the second corresponding to thiol addition to the catechol, after air oxidation to o-quinone. Observation of these peptide adducts classifies these compounds as prehaptens. Interestingly, no adduct formation was observed when the same reactions were performed under oxygen-free conditions, highlighting the importance of air oxidation processes in CA, CAAE, and CAPE adduct formation. Additionally, through NMR analysis, we found that thiol addition occurs at the C-2 position in the aromatic ring of the CA derivatives. Our results emphasize the importance of air oxidation in the sensitization potency of propolis and shed light on the chemical structures of the resultant haptens which could trigger allergic reactions in vivo.

Kinetics of oxygen consumption, a key factor in the changes of young wines composition

The oxygen that a wine receives during the winemaking process defines its properties. The aim of this work was to evaluate the oxygen consumption capacity of wines and its influence on the modification of their composition. This preliminary work evaluated the changes after 3 months in the chemical composition of twenty-seven Spanish commercial red, white and rosé wines after their air saturation and oxidation process at 35 °C for 7 days. All the wines studied were high oxygen consumers, while the white and rosé wines showed greater variability according to their chemical composition. Wines that consumed a lot of oxygen did so quickly or slowly, while wines that consumed little oxygen did so slowly. All the wines showed a significant decrease in ethyl esters of straight-chain fatty acids (50–58%), ethyl esters of branched-chain fatty acids (48–56%) and alcohol acetates (34–65%) content, and a significant increase in Strecker aldehydes (24%) because of oxygen consumption. This paper presents a preliminary approach to determine the oxidation tendency of different wines showing the importance of controlling the winemaking processes that can increase oxygen availability and of establishing the minimum appropriate level of free sulfur dioxide.

Kinetics and mechanism study of dyes degradation in electric field-promoting catalytic wet air oxidation process

Wet air oxidation (WAO) is a clean and eco-friendly technology for dyes removal, but the high operating temperature and pressure limit its practical application. In the present work, an electric field-promoting (EF-promoting) catalytic WAO process is developed to degrade dyes under room condition. The oxidation kinetics of four different types of dyes and their degradation pathways are studied. A kinetic model is constructed by including the exogenous electric field into the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism framework, and quantitative structure-activity relationship (QSAR) analysis is conducted to correlate the kinetic parameters to the physicochemical properties of the dyes. A negative linear relationship is found between the adsorption equilibrium constants of the dyes and their first ionization energies, and their surface reaction rate constants are positively linearly associated to Esum (ELUMO + EHOMO). The degradation pathways of the different dyes are proposed according to the degradation intermediates and the activities of the atoms within the dye molecules. The heteroatoms N and S, and the atom C connecting the aromatic rings are identified as the susceptible sites upon the electrophilic attack of O2. Bond cleavage at these sites gives rise to aromatic fragments which are eventually mineralized via carboxyl acids. The results of this work is helpful for guiding the design and operation of the EF-promoting catalytic WAO process into the treatment of various dye wastewaters.

Spherical activated carbons derived from resin-microspheres for the adsorption of acetic acid

Separation of small-molecule carboxylic acids, especially acetic acid, from wastewater is challenging due to its high-water solubility, acidity, and low concentration. In this work, resin-derived spherical activated carbon (RSAC) was directly prepared from resin spheres through facile pre-oxidation and carbonization processes. RSAC was characterized by SEM, N2 physisorption, XRD, Raman, element analysis and XPS. RSAC showed high removal rates (> 95.8 %) for a variety of small-molecule carboxylic acids. The initial adsorption capacity of acetic acid over RSAC was 23.4 mg/g and 94 % of the removal rate was retained after five successive adsorption-desorption cycles for 1000 mg/L acetic acid. In addition, RSAC showed a high total organic carbon removal rate (> 80 %) for the high-salinity effluent of catalytic wet air oxidation (CWAO) process. The adsorption of acetic acid over RSAC complied with the pseudo-second-order model and Langmuir model ideally, through Vander Waals force and pore-filling effect. Furtherly, discarded resin microspheres were used to prepare spherical active carbon, which showed 88.2 % removal of acetic acid (1000 mg/L). The benign scheme of “treating wastes by wastes” from economical and environmental aspects was realized.

Microinterface intensification in hydrogenation and air oxidation processes

Hydrogenations and air oxidations usually have low apparent reaction rate, generally controlled by mass transfer rate, and widely exist in the modern chemical manufacturing process. The key to increase the mass transfer rate is the reduction of the liquid film resistance 1/ k L a . In this work, the original concept of microinterface intensification for mass transfer and then for these reactions has been proposed. We derived the regulation model and set up the mathematical calculation method of micron-scale gas-liquid interface structure on mass transfer and reaction, designed the mechanical energy exchange device that can produce gas-liquid microinterface system on a large scale, and established the OMIS system which is able on line to measure the diameter and distribution of millions of microbubbles, interface area a and mass transfer film thickness δ M , as well as developed a series of microinterface intensified reactor systems (MIRs) for the applications of hydrogenation and air oxidation processes. It is believed that this research will provide an up-to-date development for the intensification of hydrogenation and air oxidation reactions.

Mineralize complex organic contaminants using only oxygen on dense copper atoms embedded in the walls of carbon nanotubes

In this study, a novel catalytic air oxidation (CAO) process is proposed based on a facilely synthesized nanocomposite catalyst. The catalyst was prepared using Cu single atoms (CuSA) embedded on multiwalled carbon nanotubes (CNTs), denoted as CNTs@CuSA, with mass ratio of CuSA up to 10.02 %. Humic acid (HA) and other typical refractory contaminents were used to investigate the ability of CNTs@CuSA in CAO. The catalysts were pre-excited to cross the energy barrier at 120 °C for 10 min, and then used to catalyze the oxidation of HA at 90 °C in 50 min. The CNTs@CuSA with CuSA mass ratio 8.39 % showed a superior catalytic activity, and 99 % of HA in solution was degraded with 98 % of organic carbon mineralization. Aberration-corrected transmission electron microscopy, electron paramagnetic resonance spectroscopy, and density functional theory calculations were applied to detect the mechanism. The results showed that the Cu-N coordination sites on CNT walls and the confinement effect of CNTs activated O2 to produce ·OH radicals, with a high activation efficiency. Moreover, this catalyst remained active after multiple cycles. This result provides a new catalyst to support low-temperature catalytic air oxidation for organic wastewater treatment.

Multi-Elemental Coatings on Zirconium Alloy for Corrosion Resistance Improvement

Zirconium alloys are commonly used as a cladding material for fuel elements in nuclear reactors. This application is connected with zirconium alloy’s good resistance to water corrosion and radiation resistance under normal working conditions. In the case of severe accident conditions, the possibly very fast oxidation of zirconium alloys in steam or/and air atmosphere may result in the intense generation of hydrogen and explosion of the hydrogen oxide mixture. The development of a solution to minimize the aforementioned risk is of interest. One of the actual concepts is to improve the oxidation resistance of Zr alloy cladding with protective coatings. This study aimed to develop, form, and investigate new coatings for zirconium alloy Zry-2. Multi-elemental Physical Vapour Deposition (PVD) coatings with Cr, Si, and Zr were considered for Institute of Nuclear Chemistry and Technology) INCT as corrosion protective coatings for nuclear fuel claddings. Heat treatment at 850–1100 °C/argon, air oxidation processes at 700 °C/1–5 h, and a long-term corrosion test in standard conditions for Pressure Water Reactor (PWR) reactors (360 °C/195 bar/water simulating the water used in PWR) were carried out. Initial, modified, and oxidized materials were characterized with Scanning Electron Microscopy (SEM) (morphology observations), Energy Dispersive Spectroscopy (EDS) (elemental composition determination), and X-ray Diffraction (XRD) (phase composition analysis). Slower oxidation processes and a smaller oxidation rate, in the case of modified material investigations, were observed, as compared with the unmodified material. The obtained results displayed a protective character against the oxidation of formed layers in the defined range of parameters in the process.

Ionic Dopant-Free Polymer Alloy Hole Transport Materials for High-Performance Perovskite Solar Cells.

The dominated hole transport material (HTM) used in state-of-the-art perovskite solar cells (PSCs) is Spiro-OMeTAD, which needs to be doped to improve its conductivity and mobility. The inevitable instability induced by deliquescent dopants and the necessary oxidation process in air hinders the commercialization of this technology. Here, an alloy strategy using two conjugated polymers with highly similar structures but different crystallinities for dopant-free HTM and high-performance PSCs has been demonstrated. We found that the polymeric packing and crystallinity of a polymer alloy could be regulated finely by blending the polymer PM6 and our developed polymer PMSe, which exhibits a shorter π-π stacking distance due to the improved planarity of the polymer backbone with strong C═O···Se noncovalent interactions. The structure-property relationship of the polymer alloy is investigated by theoretical and experimental analyses. The optimized PSCs using the polymer alloy HTM without any ionic dopants feature an excellent power conversion efficiency of 24.53% and a high open circuit voltage (VOC) of 1.19 V with much improved stability. This efficiency is much higher than that of the control device using doped Spiro-OMeTAD HTM (PCE = 22.54%). Our work provides a very effective strategy to design and construct dopant-free hole transport materials for highly efficient perovskite solar cells and other applications.

Catalytic wet air oxidation of azo dye (reactive red 2) over copper oxide loaded activated carbon catalyst

The degradation of reactive red 2 mono azo dye through catalytic wet air oxidation process using copper oxide loaded activated carbon catalyst showed remarkable a result. The AC was prepared from water hyacinth root using the physic-chemical activation method and the copper oxide loaded activated carbon (CuO/AC) catalyst was prepared through the wet impregnation method. It was characterized by: Fourier transform infrared (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermo gravimetric analysis (TGA) instruments. The influence of operating parameters (catalyst dose (2–6 g/L), reaction temperature (70–120 °C), and oxygen partial pressure (1–3 bar)) on reactive red 2 (RR2) dye decolorization and chemical oxygen demand (COD) conversion at a reaction time of (10–120 min) were investigated. Complete dye decolorization (100%) and 88.57% chemical oxygen demand (COD) conversion were achieved at maximum operating conditions, 6 g/L of catalyst dose, 120 °C reaction temperature, and 3 bar of oxygen partial pressure within 120 min of reaction time. The percentage of dye decolorization was 42.91 and 59% in the presence of free radical scavengers sodium bicarbonate (NaHCO3) and methanol (CH3OH) respectively. Also, the performance of the reused catalyst was decreased. Based on the percentage of germination index of lepidium sativium seed, the phytotoxicity of the treated dye solution has low toxicity (62.67%) than the untreated dye solution (34.80%).

Performance of high temperature phase-stable high entropy oxide (MgCuMnCoFe)Ox in catalytic wet air oxidation of chloroquine phosphate

With the continuous spread of COVID-19, the water pollution problems caused by the abuse of chloroquine phosphate (CQP) as an antiviral drug have attracted wide attention. The cubic Fm-3m spinel high entropy oxide (HEO)—(MgCuMnCoFe)Ox was prepared by coprecipitation method as the catalytic wet air oxidation (CWAO) catalyst to treat CQP simulated wastewater. Through electron spin resonance (ESR) analysis, HEO will stimulate the production of superoxide radical (·O2−) and hydroxyl radical (·OH) in the wet air oxidation (WAO) process, which accelerates the degradation and mineralization of CQP. Through response surface method (RSM) optimization, the optimal degradation conditions of CQP in CWAO were proposed: initial oxygen pressure of 15 bar, catalyst dosage of 1.4 g/L and temperature of 230 °C. The advantages of HEO in CWAO were analyzed by principal component analysis (PCA). The degradation mechanism of CQP in CWAO by (MgCuMnCoFe)Ox were explored. This work provides a new idea for the rapid development of HEO in the field of environmental catalysis.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10853-022-07271-z.

Biomass-derived mesoporous and super-hydrophilic carbon manufactured by cycling-pressure-switching air activation process towards ultrahigh adsorption efficiency of tetracycline

Mesoporous and super-hydrophilic carbon materials have been synthesized with sugar cane bagasse via a cycling pressure-switching (CPS) air oxidation process. Facilitated by the pressure-switching process, reactive gas (air) can diffuse into porous channels for activation reaction and create rich mesoporous structure as well as abundant surface functional groups. Compared to conventional atmospheric pressure (AP) method, CPS process simultaneously maximizes the mesopore volume fraction (37%) and enriches the surface functional groups. Such unique carbon materials were systematically characterized by various techniques to reveal the evolution of pore structure and surface property. These materials have been demonstrated very effective for the adsorption of bulk antibiotics such as tetracycline (TC) and the maximum adsorption capacity of 671.14 mg/g was achieved at room temperature with feeding TC concentration of 150–400 mg/L−1. In a word, this work presents an environmental benign approach to manufacture porous carbon with direct air activation, the unique features of the materials with large mesopore volume and superhydrophilic surface enable efficient adsorption of bulk molecules in aqueous solution and show promising application in antibiotics removal from polluted water.

Comparison of two methods of neutralization and wet air oxidation for treating wastewater spent caustic produced by oil refineries.

Today, problems of treating wastewater spent caustic produced by refinery units with high toxic compounds and chemical oxygen demand (COD) become concerns of many managers of these industries and environmental experts. Hence, emission without application of treatment methods will have adverse environmental impacts. In this study, two direct acid neutralization (DAN) and wet air oxidation (WAO) processes were selected to treatment the wastewater of the Bandar Abbas oil refinery in southern Iran. The aim was to reduce COD and harmful substances, compare the two methods, optimize processes, and evaluate their performance. Experimental experiments were performed in a reactor system with different input variables related to two different methods. Parameter optimization was performed based on Box-Behnken (BBD) method and Design Expert software. The analysis of the results based on statistical methods and response procedure diagrams was used to evaluate the status of COD changes to the parameters. The best operating conditions of temperature, pressure, residence time, and stoichiometric coefficient of air were 148.269°C, 15.716bar, 3.563h, and 8.415l/h respectively in WAO with 68% reduction in COD, and for DAN process, temperature, pH, and agitation speed were 30.082°C, 2.008, and 203.672rpm, respectively, with 43% reduction in COD. Results of rapid impact assessment matrix (RIAM) showed that WAO process with a higher score is a more environmentally friendly method and DAN process has been considered by experts due to its popularity, ease of testing, less equipment requirements, and lower cost.

Study on heterogeneous catalytic wet air oxidation process of high concentration MDEA-containing wastewater

High concentration N-methyldiethanolamine (MDEA)-containing wastewater with strong alkaline, high chemical oxygen demand (COD), and toxic organics, cannot be directly treated by biochemical process. In this paper, effect of operation parameters (temperature, reaction pressure and residence time) on removal ratio of COD and MDEA was investigated by catalytic wet air oxidation (CWAO) over commercial activated carbon (AC). The degradation pathway of MDEA in the CWAO was proposed. The results showed that the concentration of MDEA, COD, total organic carbon (TOC), and total nitrogen (TN) were 18.92, 61.2, 21.34 and 5.65 g·L−1, respectively. The contribution rate of MDEA concentration to COD in the wastewater reached up to 89.8%. The removal ratio of MDEA and COD exceeded 98% and ∼90% at temperature of 230 °C, reaction pressure of 5.0 MPa and residence time of 90 min for 168 h continuous running, respectively. The surface carboxylic acid groups of AC played a key role in the formation of hydroxyl radicals (·OH), due to the O2 was adsorbed by the carboxyl groups on the surface of AC to form ·OH, and the ·OH then attacked the CN bond of the MDEA to generate other intermediate products, and then these intermediate products was further oxidized to NH4+, CO2 and H2O. This work provides a promising pretreatment technology of high concentration MDEA-containing wastewater.

Research on Coal Tar Pitch Catalytic Oxidation and Its Effect on the Emission of PAHs during Co-Carbonation with Coal

Coal tar pitch (CTP) is abundant and widely used, but its properties will be affected due to oxidation aging during storage. In this study, CTP was oxidized by simulating the air oxidation process, and the change of chemical structure has been analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and both gas chromatography and mass spectrometry (GCMS). The effects of the oxidized and unoxidized CTP co-carbonization with coal on the polycyclic aromatic hydrocarbons (PAHs) emission were detected by GCMS. The small and medium-molecule aromatic substances were reduced during CTP oxidation, while the intermolecular condensation reaction increased the macromolecules content. The catalytic can effectively facilitate the dehydrogenation and condensation reaction of CTP and the entry of oxygen molecules, which leads to the increase of oxygen-containing groups and the decrease of PAHs. Compared to the raw CTP, the catalytic oxidized CTP significantly reduced the emissions of toxic PAHs during the co-carbonization with coal. A possible catalytic mechanism of CTP catalytic oxidation is proposed.

Kinetics of catalytic treatment of coking wastewater (COD, phenol and cyanide) using wet air oxidation

Abstract Coking wastewater (CWW) is known as a highly polluting effluent. This study deals with the degradation of pollutants in terms of COD, phenol and cyanide present in CWW using catalytic wet air oxidation (CWAO) process. CWAO was carried out in batch mode using various catalysts. The investigated operating parameters are initial pH (pH i ) 3–11, temperature (T) 100–160 °C, air partial pressure (p air) 2–6 MPa, catalyst mass loading (C w ) 2–5 g/L and treatment time (t R ) of 0–6 h. Among various catalysts, the copper chloride was proved to be best for degradation of pollutants. The optimum conditions were evaluated for the degradation of organic compounds as T 130 °C, p air 8.8 MPa, C w 3 g/L and t R = 6 h. The maximum percentage reduction of COD, phenol, and cyanide was achieved through experiment at T 160 °C, p air 12.2 MPa, C w 5 g/L and t R 6 h as 97.32%, 97.94% and 99.87%, respectively. The kinetics studies were also performed to evaluate the rate constant (k), and reaction order with respect to COD, phenol, CN, CW and p air.