Wet Oxidation Research Articles

Effects of reaction conditions on the wet oxidation of excess sludge from the caprolactam wastewater treatment process.

In this study, wet oxidation of excess sludge from the caprolactam wastewater treatment process was investigated. The effects of reaction conditions, including sludge concentration, the amount of sludge, reaction temperature and time and the oxygen supply amount, were discussed. The highest removal rates of chemical oxygen demand (COD) and volatile suspended solid (VSS) that can be attained at 78.6 and 89.3% were acquired separately under 260 °C for 60 min with an initial oxygen gas pressure of 1.3 MPa. The sludge was hydrolyzed and oxidized under hydrothermal conditions, producing small molecule organic acids, such as acetic, formic and oxalic acids, as the main products, which could be used as carbon sources for wastewater treatment. These results indicated that wet oxidation provides a favourable and feasible alternative method for the treatment of excess sludge from the coal chemical industry.

A novel bimetallic Fe-Cu-CNT catalyst for effective catalytic wet peroxide oxidation: reaction optimization and mechanism investigation

Treatment of organic wastewater is of great importance and can be carried out by catalysis technologies such as catalytic wet peroxide oxidation (CWPO). A novel bimetallic Fe-Cu-CNT catalyst was first developed by a facile hydrothermal method; Fe species (Fe (Ⅱ) and Fe (Ⅲ)) and Cu species (Cu (Ⅰ) and Cu (Ⅱ)) were used to fabricate the catalyst with the CNTs, which was stable during testing. Methylene blue (MB) was chosen as model compound for the study; the optimization for treatment by the Box-Behnken design indicated that a combination of low pH, high MB concentration and intermediate temperature led to better treatment performance. The CWPO reaction obeyed the 2nd-order kinetic equation and the catalyst activity increased with an increase in the Cu content. The reaction induction period was shortened with decreasing Fe:Cu ratio. The cycling reaction between Fe3+/Fe2+ and Cu2+/Cu+ pairs generated a large number of oxidative radicals and improved the pollutant degradation efficiency. Finally, the reaction rate equation of CWPO over Fe-Cu-CNT was derived, and it was experimentally illustrated that hydroxyl radicals played a crucial role in the treatment. This study demonstrates that the optimized Fe-Cu-CNT has great potentials for treatment of organic wastewater with higher efficiency and lower cost.

Facilely prepared heterogeneous Fenton catalyst Fe(Fe0.69Al0.31)2O4@C for catalytic wet peroxide oxidation of ciprofloxacin in batch and continuous reactor: Reaction intermediates and toxicity evaluation

Herein, by using a simple co-precipitation method Al-doped magnetite spinel nanoparticle encapsulated in the carbon matrix Fe(Fe0.69Al0.31)2O4@C was synthesised and its catalytic activity was examined as a heterogeneous Fenton catalyst towards the catalytic wet peroxide oxidation (CWPO) of antibiotic pollutant 20 ppm ciprofloxacin (CIP) in batch and continuous reactors. Under the optimized conditions, 0.5 g·L-1 Fe(Fe0.69Al0.31)2O4@C in batch reactor mineralized 51 % of CIP was achieved within 180 min at 50 °C and pH 3 by utilizing 1.2 mM or 4S H2O2 (S = stoichiometry; 47 mol H2O2:1 mol CIP) which is significantly less concentration compared to other heterogeneous Fenton catalysts. Impressive long-lasting catalytic activity was demonstrated in the up-flow fixed bed reactor, for 110 h with 44 % TOC removal and less than 1 ppm Fe leaching in the effluent water. Kinetic studies on the rate of decomposition of H2O2 revealed that Fe(Fe0.69Al0.31)2O4@C effectively decomposed the H2O2 like the homogeneous Fenton catalyst. The XPS results confirmed the influence of Al on iron ions in the magnetite structure through a substantial shift in higher binding energy for Fe3+ and introduced a more electropositive character on the Fe3+(δ+) that successively expedites the kinetically slow Fe3+ reduction reaction with H2O2 to produce HOO•. The π electrons of the graphitic carbon facilitate the electron transfer between the carbon matrix and Fe(Fe0.69Al0.31)2O4 nanoparticles to enhance the CIP degradation. The acute toxicity assessment studies validated the non-toxic nature of the effluent water obtained from batch and continuous reactors. A degradation pathway was proposed based on the eleven intermediate products identified using LC-HRMS analysis.

Sustainable energy recovery from mixed agri-food waste by hydrothermal carbonisation: Mechanistic evaluation of the evolution of product characteristics

To address aggravating climate concerns and enhance bioenergy production, mixed agri-food waste (MAFW) was upgrade into high quality solid biofuel using hydrothermal carbonisation (HTC), demonstrating the potential to convert low-quality biowaste into valuable bioenergy resource. The influence of reaction temperature (190–230 °C), residence time (1–5 h) and solid loading (5–20 %) on the evolution of hydrochar and process water (PW) characteristics were systematically investigated to gain mechanistic insight into the HTC process of MAFW. In addition, an assessment of the valorisation option(s) for MAFW PW was conducted to guide the development of a conceptual HTC-based biorefinery system for sustainable bioenergy production. Results demonstrated that high HTC reaction severity (increased reaction temperature and residence time) enhanced the fuel characteristics of the hydrochar except for nitrogen content, which increased by ⁓86 % at the most severe HTC operating condition. Furthermore, the concentration of organic compounds in the PW showed a significant decrease as the reaction severity increased, except for total phenol content which showed a consistent increase. Meanwhile, the concentration of organic compounds in the PW increased as the solid loading increased. Overall, MAFW PW is rich in organic matter but relatively low in nutrients. Based on the analysis of the hydrochar and PW characteristics at different HTC operating conditions, it was revealed that dehydration, decarboxylation, aromatisation and Maillard reaction constitute primary reaction mechanisms influencing the HTC conversion of MAFW. Although higher reaction severity yielded a high degree of coalification in MAFW hydrochar, a medium reaction severity was conducive for producing high-quality solid biofuel. Additionally, medium solid loading yielded ample solid yield and a moderate organic matter concentration in the PW. To efficiently valorise the MAFW PW, a multistage process involving the combination of wet oxidation, anaerobic digestion and nutrient recovery was proposed. The findings presented in this study offer valuable referential information for improving the fuel quality of hydrochar obtained from MAFW and guiding the development of a sustainable strategy to harness the energy potential of MAFW via HTC.

Enhancing sodium percarbonate catalytic wet peroxide oxidation with artificial intelligence-optimized swirl flow: Ni single atom sites on carbon nanotubes for improved reactivity and silicon resistance

H2O2 is widely used in the treatment of refractory organic pollutants.However, due to its explosive and corrosive chemical characteristics, H2O2 will bring great safety risks and troubles in transportation.So we chose sodium percarbonate(SPC) to be used in catalytic wet peroxide oxidation enhanced by swirl flow(SF-CWPO) and we designed carbon nanotubes with Ni single atom sites(Ni-NCNTs/AC) to activate SPC to treat an m-cresol wastewater containing Si.Meanwhile, artificial intelligence which used Artificial neural network (ANN) was used to optimize the conditions.Under the conditions of pH = 9.27, reaction time of 8.91 min, m-cresol concentration is 59.09 mg L−1, SPC dosage is 2.80 g L−1 and Na2SiO3·9H2O dosage is 77.27 mg L−1, the degradation rate of total organic carbon(TOC) and m-cresol reaches 94.37% and 100%, respectively.Finally, the applicability of Ni-NCNTs/AC-SPC–SF–CWPO technology was evaluated in a wastewater system of a sewage treatment enterprise and Fourier transform ion cyclotron resonance mass spectrum(FT-ICR MS) analysis and chemical oxygen demand(COD) analysis showed the great ability of Ni-NCNTs/AC-SPC–SF–CWPO technology to treat wastewater.It is believed that this paper is of great significance to the design and construction of the in-depth research and industrial application of SF-CWPO.

Identifikasi Mikroplastik Polyethylene (PE) Menggunakan Digesting Wet Peroxide Oxidation (WPO)

The extraction method using Wet Peroxide Oxidation (WPO) is a digestion method for separating microplastic particles and other organic/inorganic precipitation, with a liquid oxidation process using peroxide and iron salts as catalysts. Polyethylene (PE) is a type of plastic that pollutes the environment due to its high level of use in the packaging sector. The aim of this research is to determine the optimum conditions for the Wet Peroxide Oxidation (WPO) extraction method and obtain an effective method for identifying microplastics. Variations in oven temperature are 70⁰C, 80⁰C, 90⁰C, 100⁰C, and 110⁰C; variations in Fe(II) concentrsation 0.025 M, 0.05 M, 0.075 M, 0.1 M, and 0.125 M; heating temperature variations 30⁰C, 45⁰C, 60⁰C, 75⁰C, and 90⁰C. The research results showed that the optimum oven conditions occurred at a temperature of 90⁰C producing a microplastic mass of 0.5943 grams, the optimum Fe(II) concentration of 0.1M produced a mass of 1.2966 grams, the optimum heating temperature occurred at 60⁰C producing a mass of 0.7128 grams. For samples, characterization using FTIR showed that no new groups were formed after being treated under optimal conditions. Meanwhile, for XRF, no impurity elements were identified after the sample was treated with optimum conditions.

Flaws in the methodologies for organic carbon analysis in seagrass blue carbon soils

AbstractThe ability to accurately measure organic carbon (OC) in marine sediments or soils is overall taken for granted in scientific communities, yet this seemingly mundane task remains a methodological challenge when the soil matrix contains calcium carbonate (CaCO3), creating inaccuracies in Blue Carbon estimates. Here, we compared five common methods combining acidification, combustion, and wet oxidation pre‐treatments for determination of OC in sediments and soils containing CaCO3 based on the analyses of artificial soil mixtures made of different OC and CaCO3 contents, and multiple soils from Australian seagrass cores. The results obtained showed that methods involving acidification pre‐treatment entailed −17 ± 0.2% (mean ± SE) underestimation of OC content (ranging from −8% to −26%), whereas the combustion‐based method was accurate for samples with high CaCO3 content but entailed 32–47% overestimation in samples with low CaCO3 content. The Heanes method (wet oxidation method) showed <5% deviation from the known OC content, but this method is not suitable for soil samples containing reduced iron, sulfur and potentially manganese compounds. The differences observed among methods have significant impacts on local, regional, and global Blue Carbon storage calculations. We provide key methodological guidelines for the analysis of OC in soils with high and low CaCO3 contents, aiming at improving accuracy in current Blue Carbon science.

Catalytic wet air oxidation of phenol over nano mesoporous lanthanum oxide synthesized by chitosan template method

The study investigates the effectiveness of nano mesoporous lanthanum oxide (La2O3), synthesized by the chitosan template method, as a catalyst for the wet air oxidation of phenol (WAO). To relate the performance of the synthesized La2O3 to its chemical and textural characteristics, it was subjected to a thorough characterization using various analytical techniques, including TG-DTG, XRD, FTIR, BET, TEM, TPD-CO2, TPD-NH3, and H2-TPR. Nanomesoporous La2O3 displayed remarkable efficiency in removing phenol and total organic carbon (TOC) while exhibiting a greater preference towards non-organic compounds. Significant improvement in removal efficiency and selectivity when compared to non-catalytic wet air oxidation is observed for the catalyst. The study investigated the impact of temperature, catalyst dosage, airflow, and phenol pumping rate on the catalytic wet air oxidation (CWAO) of phenol. Even after 6 h of continuous reaction, La2O3 exhibited exceptional catalytic stability. The mesoporous nature and presence of Lewis basic sites in nano-La2O3 may be crucial in facilitating the degradation of phenol and enhancing the efficiency of TOC removal. The study concludes that the chitosan template method is an effective approach for synthesizing nano mesoporous lanthanum oxide, which could be used as a promising catalyst for the treatment of phenol-containing wastewater.

Nutritional ingredients and fertilizer potential of the dewatering effluent after sludge wet air oxidation

Wet air oxidation (WAO) is an effective technology for sludge treatment, and the treated sludge was mechanically dewatered to generate sludge cake and filtrate effluent. The sludge cake can be used as a soil conditioner or sent to landfills, but the effluent is usually sent back to wastewater treatment plants with nutrient waste. In this study, we proposed to use the effluent to process water-soluble organic fertilizer and analyzed its characteristics systematically and its effect on seed germination. The results showed that humic acid, protein, and polysaccharide were decomposed in different degrees in WAO with a chemical oxygen demand (COD) removal rate of 60–70%. After a WAO treatment at 240 °C, phosphorus, potassium, and heavy metals remained in the solid phase. At the same time, the effluent contained ammonium of more than 2800 mg/L, amino acids of nearly 3000 mg/L, humic acid derivatives of 2400 mg/L, and acetic acid of 3900 mg/L. Acetic acid was helpful in seed germination, while the other components were critical to root growth. The diluted effluent significantly prompted the germination and development of three kinds of plant seeds, particularly Spring Onion, with a germination index exceeding 200%.

Improving the braking performance of the novalac-based CNFs/carbon composite by the wet chemical oxidation of CNFs

In this research, the braking performance of the CNFs-carbon composite pads was improved by the oxidation of CNFs using wet chemical oxidation. Oxidation of CNFs resulted in the formation of functional groups on the CNFs that improved adhesion and bonding of the CNFs to the matrix. Through this process, the toughness, tensile, compressive, and bending strength of the composite were strongly increased. Also, the hardness and wearing properties of the composite were improved by the oxidation of CNFs. For the composite reinforced by the oxidized CNFs, the low content of the nanofiber pull-out increased the COF. The main disadvantage of the oxidized CNFs-carbon composite was the sample decomposition at temperatures above 400 ºC. This feature can deteriorate the braking performance of the composite when it is pushed too hard and overheated. To fix this problem, a SiC coating layer was applied to the composite by CVD method. Applying SiC postponed the thermal degradation of the composite up to 1000 ºC. Weight losing of the SiC-coated sample was recorded at about 3.13% at 1000ºC.

Identification of microplastics in fish from the local fish market of Yogyakarta Province, Indonesia

Marine pollution, mainly plastic waste, has become a worldwide problem, especially in Indonesia. Indonesia is the second contributing country after China, with 10% contribution of the source of plastic pollution in the world. In the ocean, plastic will fragment into smaller pieces (less than 5 mm), known as microplastics (MPs). MPs can harm wildlife, especially fish, due to their toxic characteristics or other toxic substances attached to them. Indonesia, especially coastal areas, is known for its high consumption of marine fish, so this study aims to investigate the microplastics in fish sold at lokal fish markets in Bantul Regency, Yogyakarta Province, Indonesia. The fish sold came from the southern sea of Java (Indian ocean) around Depok Beach, Cemorosewu Beach, and Parangkusumo Beach. Three types of fish dominate namely Skipjack, Snapper, and Pomfret. The National Oceanic Atmospheric Administration (NOAA) and Wet Peroxide Oxidation (WPO) methods were used to examine fish samples. Identification of MPs was made based on shape and colour. The results showed that the most common MPs found were fibres with a total number of 36-91 particles/fish. The dominant colour of MPs is transparent, with a total of 552 particles from total samples. Although the analysis was only conducted in fish intestinal, there is potential that MPs will be found in fish meat. The chemical characteristics of MPs were determined using the Fourier Transport InfraRed (FTIR). The types of plastics found were Polyethylene (PE), Polypropylene (PP), and Nylon.

Development of CoZrTaB Laminated Thin Films With Novel CMOS Compatible Dielectric Material

This paper presents an optimized CoZrTaB-based laminated thin films with a wet etch-able oxide dielectric material. Wet etching capability was studied on the stack material and a narrow and clean undercut was achieved. Good uniaxial anisotropy with low coercivity (<1 Oe) was achieved via in-situ magnetic alignment during magnetron sputtering. Relative permeability of 432 and Q-factor of 23.4 at 100 MHz were observed in high frequency permeameter measurement. Finally thermal annealing was carried out at various temperatures. Uniaxial anisotropy was maintained up to 300 °C, while an enhancement of permeability (by 25%) was observed.

Efficient removal of aromatic pollutants via catalytic wet peroxide oxidation over synthetic anisotropic ilmenite/carbon nanocomposites

As one of the most common ferrous (Fe2+)-containing oxide minerals in the Earth’s crust, ilmenite (FeTiO3) is a potential low-cost heterogeneous Fenton-like catalyst for organic wastewater treatment via catalytic wet peroxide oxidation (CWPO). However, it suffers from low activity and long induction time. Herein anisotropic FeTiO3/C nanocomposite with rich Fe2+ ions on large surface area of 159.0 m2 g−1 (surface Fe/Ti and Fe2+/Fe3+ ratios were respectively 2.1 and 2.0) was prepared via cetyltrimethylammonium (CTA+)-assisted sol-gel synthesis. CTA+ modulated the growth of FeTiO3 nanoparticles with more exposed metallic sites by preferential adsorption on its (104) plane via electrostatic attraction, provided the carbon source and facilitated the generation of more Fe2+ ions at the interface of FeTiO3/C via carbothermal reduction of FeTiO3. FeTiO3/C efficiently catalyzed CWPO removal of six aromatic pollutants with different charges (25 mg L−1 each) at 25 oC and pH 3.0 without an induction period owing to rich Fe2+ content on neutral surface (pHpzc ~3.3)—three dye solutions completely decolorized in 1 h and three antibiotics degraded by >90% in 3 h. Reusability of FeTiO3/C was demonstrated with cationic rhodamine B and anionic orange G dyes in five consecutive runs. Scavenging tests and spin-trapping EPR spectra confirmed the generation of dominant ·OH and minor O2•− species for organic degradation via catalytic decomposition of H2O2 on FeTiO3/C as a heterogeneous Fenton-like catalyst.

Catalytic wet air oxidation of sulfamethoxazole and tetracycline using platinum-based catalysts at eco-operating conditions

Conventional wastewater treatment plants (WWTP) are unsuitable for emerging contaminants' elimination. Most of these pollutants persist after the treatment and threaten the receiving environment. Catalytic wet air oxidation (CWAO) is one of the promising solutions to treat these concentrated active molecules. This study reports the catalytic degradation tests on sulfamethoxazole (SM) and tetracycline (TET) using platinum (Pt) supported on cerium oxide (Ce) and mixed cerium and zirconium oxides (CeZr). Pt/CeZr catalyst showed 98 % TET elimination at 50 °C under atmospheric pressure (Patm). Furthermore, the test at room conditions reached 92 % removal. Pt/Ce test enabled 77 % SM elimination and reached 45 % SM mineralization. Toxicity assessment confirmed the environmental legibility of the treated solution using CWAO. The outcomes of this study showed an eco-energetic, eco-friendly, and efficient way to treat wastewater loaded with pharmaceutical pollutants.

Utilization of Ferrate Ion (FeO42-) as Oxidizing Agent for Reducing Color Intensity of Peat Water

Peat water from Central Kalimantan is generally yellow to brownish-red in color. It causes peat water to not be used as a source of water for daily needs. Humic acid, fulvic acid, and humin are organic compounds that cause peat water to become colored. One alternative step that can be taken for reducing the color intensity of peat water is to degrade color-causing organic compounds by using an oxidizing agent. A hexavalent form of iron ion (Fe6+), commonly called ferrate (FeO42-) in potassium ferrate compound, is a powerful oxidizing agent used in the present study. Potassium ferrate (K2FeO4) was synthesized by a wet oxidation method and characterized using a UV-Vis spectrophotometer and an X-Ray Diffractometer (XRD). The ferrate solution is purplish-red in color with a maximum wavelength of 510 nm. The XRD pattern shows strong diffraction peaks at 2θ which are characteristic of K2FeO4. The ferrate solution was then used to degrade color-causing organic compounds in the peat water from Central Kalimantan. Determination of the optimum degradation conditions was monitored by the absorbance decrease of organic compounds in peat water at a wavelength of 370 nm. The results showed that ferrate solution with a concentration of 80 ppm was able to degrade organic compounds in peat water at pH 8, with a removal efficiency of 100%. Keywords: oxidizing agent, ferrate ion (FeO42-), peat water

Contaminants and Human Health Risks Associated with Exposure to Microplastic Ingestion of Green Mussels (Perna viridis) Collected from The Kedonganan Fish Market, Bali

Microplastics (MPs) are pollutant agents that have been absorbed and detected in aquatic ecosystems at high concentrations. This study aimed to investigate the presence of MPs pollution in green mussel (Perna viridis) products sold at the Kedonganan fish market, Badung, Bali. A total of 150 mussels with an average weight of 3,2 ± 0,71 g/mussels from three traders each composed and followed by the pre-treatment stage using 5 M NaCl solution, extraction with wet oxidation peroxidation (WPO) + Fe(II) catalyst and filtered. The highest percentage for the form of MPs was successively obtained by the Line form in Trader A at 85,42% and the lowest in Trader C at 50,00%. The highest form of fragments was obtained in Trader C at 42,86%. Film and filament forms were only obtained in Trader A. The highest MPs color was black and the lowest was gray. The highest average MPs particle size was found in the form of a filament of 1944,37 ± 88,41 μm which was found in Trader A. Estimates of MPs intake per year/capita in Indonesia showed that exposure to MPs through consumption of green mussels in this study amounted to 498,330 MPs/year/capita items. Overall, the green mussel from Trader A had the highest percentage and size of MPs, with the shape of fragment MPs being dominated by Trader C and the color of the MPs being dominated by black. MPs exposure to green mussel consumption in Indonesia is very high, but no health impact category has yet been found for this estimate.

Zinc and graphene oxide composites as new protective coatings for oil and gas pipes

A method was developed to obtain a durable coating consisting of zinc and graphene oxide (Zn-GO) in order to reduce the mechanical wear and tear rate of oil and gas pipelines made of steel. Graphene oxide was obtained from graphite by wet chemical oxidation (unmodified and modified Hummers’ method) using potassium permanganate and sulfuric acid. The process was carried out at various temperatures. The steel was covered with an ultrathin layer of Zn-GO using the electrophoretic deposition method. The GO particle size (&lt; 90 nm) was confirmed by XRD and laser analysis. For GO particles obtained by the modified Hummers’ method, a significant correlation was observed in the scratch (R2 = 0.87) and the Vickers microhardness tests (R2 = 0.93), which indicates a lower wear rate of Zn-GO-coated steel.

Preparation of PrFexCo1–xO3/Mt catalyst and study on degradation of 2-hydroxybenzoic acid wastewater by catalytic wet peroxide oxidation

In this study, the perovskite nanocomposite PrFexCo1–xO3(Pr(S)) was successfully synthesized by the sol–gel method; PrFexCo1–xO3/Al-pillared montmorillonite (Pr(S)/Mt) catalysts were prepared by impregnation (D) method and solid-melting (G) method, respectively, with Pr(S) as the active component and Al-pillared montmorillonite as the carrier. The catalysts were applied to treat the 2-hydroxybenzoic acid (2-HA)-simulated wastewater by catalytic wet peroxide oxidation (CWPO) technique, and the chemical oxygen demand (COD) removal rate and the 2-HA degradation rate were used as indicators to evaluate the catalytic performance. The results of the experiment indicated that the solid-melting method was more conducive to preparing the catalyst when the Co/Fe molar ratio of 7:3 and the optimal structural properties of the catalysts were achieved. The influence of operating parameters, including reaction temperature, catalyst dosage, H2O2 dosage, pH, and initial 2-HA concentration, were optimized for the degradation of 2-HA by CWPO. The results showed that 97.64% of 2-HA degradation and 75.23% of COD removal rate were achieved under more suitable experimental conditions. In addition, after the catalyst was used five times, the degradation rate of 2-HA could still reach 76.93%, which implied the high stability and reusability of the catalyst. The high catalytic activity of the catalyst was due to the doping of Co into PrFeO3, which could promote the generation of HO·, and the high stability could be attributed to the loading of Pr(S) onto Al–Mt, which reduced the leaching of reactive metals. The study of reaction mechanism and kinetics showed that the whole degradation process conformed to the pseudo-first-order kinetic equation, and the Langmuir–Hinshelwood method was applied to demonstrate that catalysis was dominant in the degradation process.

The Catalytic Wet Oxidation of Excess Activated Sludge from a Coal Chemical Wastewater Treatment Process

An improved catalytic wet oxidation method for the disposal of excess activated sludge from a coal chemical wastewater treatment process by using the prepared Cu-Ce/γ-Al2O3 catalyst was reported. The effects of catalyst dosage, reaction temperature and time, and initial oxygen pressure on the degradation of the sludge were investigated. The maximum removal rate of volatile suspended solids, 93.2%, was achieved at 260 °C for 60 min with the catalyst 7.0 g·L−1 and initial oxygen pressure 1.0 MPa. The removal rate of chemical oxygen demand was 78.3% under the same conditions. The production of volatile fatty acids, including mainly acetic acid, propanoic acid, and isobutyric acid, increased with the increasing temperature. These acids have the potential to be carbon sources for the biological treatment of wastewater. Scanning electron microscopy images showed that the sludge became a loose porous structure, which is beneficial for dewatering performance. The results of an energy dispersive spectroscopy analysis illustrated that the carbon element in the sludge substantially migrated from solid to liquid phases. Therefore, these results demonstrated that the proposed catalytic wet oxidation method offers a promising pathway for the disposal and utilization of excess activated sludge from the coal chemical wastewater treatment process.

Interpretable artificial intelligence for advanced oxidation systems: Principle, operations and performance

Advanced oxidation processes have been widely studied and employed due to their potent mineralization capacity for pollutants. However, the intricate reaction mechanisms of these processes pose limitations for fitting and predicting performance. In this study, we comprehensively derived and assessed neural networks for three advanced oxidation methods: catalytic oxidation, catalytic wet air oxidation, and electrochemical oxidation. Our analysis encompassed multilayer perceptron principles, forward and back propagation process, strategies for handling overfitting, and performance evaluation matrices. Additionally, we utilized Bayesian optimization to probe the impact of network architecture on outcomes. Two conventional methods, multiple linear regression and response surface methodology, are employed for comparison. Our results demonstrate that neural networks exhibit more robust performance in fitting and predicting advanced oxidation processes as indicated by statistical indicators. Importantly, we tackle the "black box" issue of neural networks by incorporating the shapley additive explanations interpretable model of game theory to elucidate the impact of advanced oxidation features on outcomes. The superior performance of explainable artificial intelligence techniques implies their vast potential for broad applications in environmental science and technology.