Study on the Performance Test of Fe-Ce-Al/MMT Catalysts with Different Fe/Ce Molar Ratios for Coking Wastewater Treatment.

It is very important to choose a suitable method and catalyst to treat coking wastewater. In this study, Fe-Ce-Al/MMT catalysts with different Fe/Ce molar ratios were prepared, characterized by XRD, SEM, and N2 adsorption/desorption, and treated with coking wastewater. The results showed that the optimal Fe-Ce-Al/MMT catalyst with a molar ratio of Fe/Ce of 7/3 has larger interlayer spacing, specific surface area, and pore volume. Based on the composition analysis of real coking wastewater and the study of phenol simulated wastewater, the response surface test of the best catalyst for real coking wastewater was carried out, and the results are as follows: initial pH 3.46, H2O2 dosage 19.02 mL/L, Fe2+ dosage 5475.39 mL/L, reaction temperature 60 °C, and reaction time 248.14 min. Under these conditions, the COD removal rate was 86.23%.

Efficient degradation of m-cresol during catalytic wet peroxide oxidation with biochar derived from the pyrolysis of persulfate-ZVI treated sludge.

Sludge dewatering is crucial for cutting the cost of sludge post-disposal in wastewater treatment plants. Response surface methodology (RSM) was used in this study to sufficiently investigate the interaction among persulfate, zero-valent iron (ZVI) and reaction time on the sludge dewatering. Under the experimental condition at the central point in RSM, the sludge moisture content was reduced to 54%. The sludge-based biochar obtained from the pyrolysis of persulfate-ZVI treated sludge at the central point in RSM was marked as SC-M and tested for catalytic activity. With the catalyst SC-M, the removal rates of m-cresol and total organic carbon (TOC) were 98.1% and 84.2%, respectively. The persulfate-ZVI treatment for sludge dewatering facilitated increasing the proportion of iron species in SC-M, which contributed to its high catalytic activity. M-cresol degradation with SC-M was a two-period reaction including an induction period and a rapid reaction with the apparent activation energy at a low level. This study integrates the sludge dewatering by persulfate-ZVI treatment and m-cresol degradation by catalytic oxidation with the biochar SC-M prepared from the dewatered iron-rich sludge, providing an effective, economic and environment-friendly approach for sewage sludge utilization and management.

Effect of copper ion-exchange on catalytic wet peroxide oxidation of phenol over ZSM-5 membrane.

Cu-ZSM-5 zeolite membrane catalysts prepared by ion exchange method were synthesized on paper-like sintered stainless fibers (PSSFs) with three-dimensional net structure for the catalytic wet peroxide oxidation (CWPO) of phenol in structured fixed bed reactor. The experimental results exhibited that the BET of optimal catalyst was 165 m2/g with the ion exchange concentration of 0.1 M and time of 24 h, respectively, at temperature of 40 °C and one time ion exchange. The FT-IR results illustrated that band intensity was the lowest, and original Cu+ species and lattice oxygen were predominant in optimal catalyst according to the XPS results. Then, the effects of ion exchange concentration, time, temperature and times on catalytic performance of phenol were also investigated in structured fixed bed. It was found that the phenol was completely removed, TOC conversion (around 76.6%), high CO2 selectivity (about 78%) and low copper leaching rate (about 30%) were achieved with only 1.91 wt% copper loading over the optimal catalyst. Finally, a reasonable reaction mechanism occurring in the presence of H2O2 for CWPO of phenol was proposed by analyzing the HPLC results, which indicated Fenton-like reactions were mainly based on the HO· production by catalytic decomposition of hydrogen peroxide with Cu+ species.

Comparative evaluation of synthesis routes of Cu/zeolite Y catalysts for catalytic wet peroxide oxidation of quinoline in fixed-bed reactor.

In order to find a better alternative of conventional aqueous ion-exchange method, several Cu/zeolite Y samples were synthesized by different routes and examined for the catalytic wet peroxide oxidation of quinoline aqueous solution in continuous fixed-bed reactor. The characterization of catalysts using ICPMS, XRD, N2 sorption, UV-vis DRS, FESEM and XPS techniques reveals the profound influence of preparation methods on synergy between copper-support interfaces. Aqueous ion-exchange (CuYAIE) and wet-impregnation (CuYIMP) methods promoted isolated Cu1+/2+ species; however, large crystallites of CuO were present on the external surface of precipitation-impregnation (CuYPI) catalyst. Interestingly, CuYPI showed hierarchical porosity and increase of surface area from 567 to 909 m2 g-1. The generation of mesoporosity in CuYPI was result of higher desilication from zeolite framework due to synergetic effect of copper and NaOH. Almost comparable mineralization (61-65%) and H2O2 stoichiometric efficiencies (44.2-45.7%) were observed for CuYAIE and CuYIMP samples. Higher catalytic activities of both catalysts in comparison to CuYPI suggest that isolated sites are the most redox-active sites for H2O2 activation and play more important role than high surface area, i.e., for CuYPI. Wet-impregnation was found better than aqueous ion-exchange method. CuYIMP exhibited high operation stability with >60% mineralization at LHSV = 4 h-1, particle size = 1.2-1.7 mm, H2O2/quinoline = 48 and T = 80 °C. Copper leaching was majorly influenced by LHSV and particle size. The system was following Eley-Rideal mechanism and kinetic parameters were calculated using model based on this mechanism.

Wet peroxide oxidation process catalyzed by Cu/Al2O3: phenol degradation and Cu2+ dissolution behavior.

Catalytic wet peroxide oxidation (CWPO) has become an important deep oxidation technology for organics removal in wastewater treatments. Supported Cu-based catalysts belong to an important type of CWPO catalyst. In this paper, two Cu catalysts, namely, Cu/Al2O3-air and Cu/Al2O3-H2 were prepared and evaluated through catalytic degradation of phenol. It was found that Cu/Al2O3-H2 had an excellent catalytic performance (TOC removal rate reaching 96%) and less metal dissolution than the Cu/Al2O3-air case. Moreover, when the organic removal rate was promoted at a higher temperature, the metal dissolution amounts was decreased. Combined with hydroxyl radical quenching experiments, a catalytic oxidation mechanism was proposed to explain the above-mentioned interesting behaviors of the Cu/Al2O3-H2 catalyst for CWPO. The catalytic test results as well as the proposed mechanism can provide better guide for design and synthesis of good CWPO catalysts.

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.

Promoted wet peroxide oxidation of chlorinated volatile organic compounds catalyzed by FeOCl supported on macro-microporous biomass-derived activated carbon.

Chlorinated volatile organic compounds (CVOCs) are a recalcitrant class of air pollutants, and the strongly oxidizing reactive oxygen species (ROS) generated in advanced oxidation processes (AOPs) are promising to degrade them. In this study, a FeOCl-loaded biomass-derived activated carbon (BAC) has been used as an adsorbent for accumulating CVOCs and catalyst for activating H2O2 to construct a wet scrubber for the removal of airborne CVOCs. In addition to well-developed micropores, the BAC has macropores mimicking those of biostructures, which allows CVOCs to diffuse easily to its adsorption sites and catalytic sites. Probe experiments have revealed HO• to be the dominant ROS in the FeOCl/BAC + H2O2 system. The wet scrubber performs well at pH 3 and H2O2 concentrations as low as a few mM. It is capable of removing over 90% of dichloroethane, trichloroethylene, dichloromethane and chlorobenzene from air. By applying pulsed dosing or continuous dosing to replenish H2O2 to maintain its appropriate concentration, the system achieves good long-term efficiency. A dichloroethane degradation pathway is proposed based on the analysis of intermediates. This work may provide inspiration for the design of catalyst exploiting the inherent structure of biomass for catalytic wet oxidation of CVOCs or other contaminants.

Preparation and characterisation of alkali-activated blast furnace slag and Na-jarosite catalysts for catalytic wet peroxide oxidation of bisphenol A.

In this study, cost-effective alkali-activated materials made from industrial side streams (blast furnace slag and Na-jarosite) were developed for catalytic applications. The catalytic activity of the prepared materials was examined in catalytic wet peroxide oxidation reactions of a bisphenol A in an aqueous solution. All materials prepared revealed porous structure and characterisation expressed the incorporation of iron to the material via ion exchange in the preparation step. Furthermore, the materials prepared exhibited high specific surface areas (over 200 m2/g) and were mainly mesoporous. Moderate bisphenol A removal percentages (35%-37%) were achieved with the prepared materials during 3 h of oxidation at pH 7-8 and 50°C. Moreover, the activity of catalysts remained after four consecutive cycles (between the cycles the catalysts were regenerated) and the specific surface areas decreased only slightly and no changes in the phase structures were observed. Thus, the prepared blast furnace slag and Na-jarosite-based catalysts exhibited high mechanical stability and showed good potential in the removal of bisphenol A from wastewater through catalytic wet peroxide oxidation.

Enhancing H2O2 utilization efficiency for catalytic wet peroxide oxidation through the doping of La in the Fe-ZSM-5 Catalyst.

Iron-loaded zeolite (Fe-zeolite) has shown great potential as an efficient catalyst for degrading organic pollutants with high concentrations in the catalytic wet peroxide oxidation (CWPO) process under mild conditions. Here, 0.4 wt% Lanthanum (La) was added in the 1.0 wt% Fe-ZSM-5 by two-step impregnation method for an enhanced H2O2 utilization efficiency. For a systematical comparison, the CWPO process at 55 °C, where m-cresol with a high concentration of 1000 mg/L as a substrate, was studied over Fe-ZSM-5 and Fe-La-ZSM-5 catalysts. Compared with Fe-ZSM-5, Fe-La-ZSM-5 showed 15% higher H2O2 utilization efficiency with comparable total organic carbon (TOC) removal at around 40%, meanwhile with a 15% reduced metal leaching. Transmission electron microscopy (TEM) with elemental mapping (EDS), surface acidity analysis by Fourier transform infrared (FT-IR) and NH3-temperature programmed desorption (NH3-TPD), redox property analysis by Raman spectroscopy and H2-temperature-programmed reduction (H2-TPR) of both catalysts revealed, that the La doped Fe-ZSM-5 can provide an altered surface acidity, a more uniform and evenly dispersed surface Fe species with a promoted reducibility, which effectively promoted the accurate decomposition of H2O2 into the reactive •OH radicals, enhanced the H2O2 utilization efficiency, and increased the catalyst stability. Also, more than 90% conversion was maintained during the continuous experiment for more than 10 consecutive test days under 55 °C without pH adjustment, showing a promising possibility of the Fe-La-ZSM-5 for a practical wastewater treatment process.

Pyrolyzed carbon derived from red soil as an efficient catalyst for cephalexin removal.

Red soil, a typical soil type in southern China, has been deemed infertile or nutrient-deficient. In this study, red soil was firstly utilized as a substrate for preparing catalysts, which were then successfully applied to the catalytic wet peroxide oxidation (CWPO) of cephalexin. The highest cephalexin removal was 95.23% and TOC removal was 60.58%, with the catalyst pyrolyzed at 500 °C (RC500). The high iron content and proportion of Fe(II) on the surface of RC500 was responsible for the decomposition of H2O2 into· OH. Moreover, the porous structure and existence of other minerals (such as SiO2 and Al2O3) in the catalyst were also significant for enhancing the catalytic activity of RC500. Afterwards, the influencing parameters, including temperature, pH, the dose of H2O2, and catalyst, were examined for cephalexin degradation. It was noteworthy that RC500 was efficient in treating hospital wastewater when using a self-design pilot device. A density functional theory analysis of cephalexin was conducted to establish the possible position attacked by ·OH, and the possibly ruptured one. Meanwhile, the intermediates generated during CWPO were identified. Finally, a reliable degradation pathway of cephalexin was proposed on the basis of the results.

A novel CWPO/H2O2/VUV synergistic treatment for the degradation of unsymmetrical dimethylhydrazine in wastewater.

In this paper, the catalytic wet peroxide oxidation (CWPO) combined with vacuum ultraviolet (VUV) irradiation was developed to mineralize the wastewater with high concentration of unsymmetrical dimethylhydrazine (UDMH), especially to decompose the main byproduct of UDMH decomposition, N-nitrosodimethylamine (NDMA). CuO-NiO-MgO/γ-Al2O3 was used as the catalyst and H2O2 as the resources of ⋅ O H . Fourier Transform Infrared spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray spectroscopy (EDX) were employed to evaluate the structure of the catalyst. The treatment performances such as the UDMH degradation efficiency, chemical oxygen demand (COD) removal efficiency, and the concentration of N-nitrosodimethylamine (NDMA) were investigated in the treating process. The optimal conditions were obtained based on the results of single-factor experiments including parameters such as the initial UDMH concentration, catalyst dosage, initial pH, H2O2 dosage and temperature. The comprehensive results indicated that CWPO/H2O2/VUV process presented remarkable treatment performance to the reaction conditions with about 100% UDMH conversion efficiency, 95.02% COD removal efficiency and approximately 100% UDMH removal within 30 min.

Enhancing the catalytic behaviour of HKUST-1 by graphene oxide for phenol oxidation.

The composites of graphite oxide (GrO) and the HKUST-1 framework were synthesized by the typical solvothermal method and applied as heterogeneous catalysts for catalytic wet peroxide oxidation (CWPO) of phenol. XRD, FT-IR, Raman and SEM were conducted to characterize the samples. For catalytic oxidation of 150 mL 100 mg L-1 phenol, the dose of 30 mg (0.2 g L-1) catalysts and 0.46 mL H2O2 were kept constant. The GrO-3/HKUST-1 (3% content of GrO) showed higher catalytic activity than the HKUST-1 framework and other GrO/HKUST-1 composites with 99% phenol conversion and 86% COD removal efficiency were obtained at 50°C after 30 min and 8 h. The effect of temperature (40-80°C) and pH (4-9) on catalytic oxidation of phenol by GrO-3/HKUST-1 was investigated. The results showed that the degradation of phenol was obtained with optimum efficiency at 60°C with complete phenol conversion and 93% COD reduction. Furthermore, the acid and alkali resistance abilities were enhanced to a certain degree by the integration of GrO compared with the parent framework HKUST-1. Three successive runs were conducted in the natural pH (6.8) of 150 mL 100 mg L-1 phenol solution which indicated that the synthesized GrO-3/HKUST-1 composite had satisfactory reusability due to the prevention of carbon deposit and negligible Cu2+ leaching (8 ppm). The GrO/HKUST-1 composite could be a kind of promising heterogeneous catalysts for catalytic degradation of organic compounds. Similar to other catalysts, the catalytic oxidation of phenol also relies on the formation of hydroxyl radicals.

Developing Fe/zeolite catalysts for efficient catalytic wet peroxidation of three isomeric cresols.

Five Fe/zeolite (i.e., Fe/ZSM-5-1, Fe/ZSM-5-2, Fe/ZSM-5-3, Fe/MCM-22, and Fe/MOR) were prepared and tested as catalysts in the catalytic wet peroxide oxidation process (CWPO). Their adsorption and catalytic effects on the removal of three isomeric cresols were systematically explored. Sufficient characterizations were carried out to illuminate the iron species dispersed on the catalysts' surface porous channels. Other properties of the catalysts such as the Si/Al ratio, crystalline structures, and morphologies were systematically studied. After loaded with iron, the catalysts maintained zeolite's framework, which possessed specific porous structures and surface areas. Interestingly, the Si/Al ratio seemed to be an important issue influencing the adsorption and catalytic degradation of cresols due to n-π interaction and the acceleration of HO• generation, respectively. The amount of framework-Fe and Fe3+Al-Si in Fe/ZSM-5-3 was the most, which was crucial for its better catalytic ability than the other Fe/ZSM-5 catalysts (71.19% for m-cresol conversion). In conclusion, the catalytic activities of all the Fe/zeolites followed the sequence: Fe/ZSM-5-3> Fe/ZSM-5-2> Fe/ZSM-5-1> Fe/MCM-22>Fe/MOR. For three cresols, m-cresol was more susceptible to the attack of HO• than p- and o-cresol because more positions of m-cresol could be easy to be approached by the oxidizing agent. Considering the mild reaction condition in this study, such as 30 °C, pH=4.0, and catalyst dosage=1.0 g/L, the Fe/ZSM-5-3 was a promising zeolite catalyst for the degradation of refractory contaminants in practical wastewater.

Post-treatment of real municipal wastewater effluents by means of granular activated carbon (GAC) based catalytic processes: A focus on abatement of pharmaceutically active compounds.

Pharmaceutically active compounds (PhACs) widely present in urban wastewater effluents pose a threat to ecosystems in the receiving aquatic environment. In this work, efficiency of granular activated carbon (GAC) - based catalytic processes, namely catalytic wet peroxide oxidation (CWPO), peroxymonosulfate oxidation (PMS/GAC) and peroxydisulfate oxidation (PDS/GAC) at ambient temperature and pressure were studied for removal of 22 PhACs (ng L-1 level) that were present in secondary effluents of real urban wastewater. Concentrations of PhACs were measured using Ultra Performance Liquid Chromatography - Triple Quadrupole Mass Spectrometry (UPLC-QqQ-MS/MS). Catalytic experiments were conducted in discontinuous mode using up-flow fixed bed reactors with granular activated carbon (GAC) as a catalyst. The catalyst was characterized by means of N2 adsorption-desorption isotherm, mercury intrusion porosimetry (MIP), elemental analysis, X-ray fluorescence spectroscopy (WDXRF), X-ray diffraction (XRD), thermal gravimetry and differential temperature analyses coupled mass spectrometry (TGA-DTA-MS). Results indicate that the highest efficiency in terms of TOC removal was achieved during CWPO performed at optimal operational conditions (stoichiometric dose of H2O2; TOC removal ~ 82%) followed by PMS/GAC (initial PMS concentration 100 mg L-1; TOC removal ~73.7%) and PDS/GAC (initial PDS concentration 100 mg L-1; TOC removal ~ 67.9%) after 5 min of contact time. Full consumption of oxidants was observed in all cases for CWPO and PDS/GAC at contact times of 2.5 min, while for PMS/GAC it was 1.5 min. In general, for 18 out of 22 target PhACs, very high removal efficiencies (> 92%) were achieved in all tested processes (including adsorption) performed at optimal operational conditions during 5 min of contact time. However, moderate (40 - 70%) and poor (< 40%) removal efficiencies were achieved for salicylic acid, ofloxacin, norfloxacin and ciprofloxacin, which can be possibly attributed to insufficient contact time. Despite high efficiency of all studied processes for PhACs elimination from urban wastewater effluent, CWPO seems to be more promising for continuous operation.

Zn-CNTs-Cu catalytic in-situ generation of H2O2 for efficient catalytic wet peroxide oxidation of high-concentration 4-chlorophenol.

4-chlorophenol (4-CP) with high concentration is difficult to degrade thoroughly by traditional treatment methods due to its high biotoxicity and refractory to bio-degradation. A novel catalytic wet peroxide oxidation (CWPO) system based on Zn-CNTs-Cu catalysts through the in-situ generation of H2O2 was constructed and investigated for the degradation of high-concentration 4-CP for the first time. Zn-CNTs-Cu composite was prepared by the infiltration melting-chemical replacement method. The operational factors effect, mechanism, and pathways of Zn-CNTs-Cu/O2 system for high concentration of 4-CP degradation were systematically performed and discussed. At the optimal experimental conditions, the degradation efficiency of 4-CP through CWPO system with Zn-CNTs-Cu/O2 achieved 100 %, which was 689 % higher than that of wet oxidation system with O2 alone. According to the mainly in-situ generated H2O2, the strong oxidative OH radical and wet-oxidation effect of O2, high concentration of 4-CP degraded into small molecular organic matter, even been mineralized into carbon dioxide and water in the Zn-CNTs-Cu/O2 based CWPO system. Overall, Zn-CNTs-Cu/O2 CWPO system can efficiently degrade high-concentration 4-CP through the in-situ generation of H2O2 without extra replenishment, and it provides a novel method and strategy to the efficient treatment of refractory chlorophenols wastewater.

Copper nickel co-impregnation of Moroccan yellow clay as promising catalysts for the catalytic wet peroxide oxidation of caffeine.

Copper and nickel were incorporated into the prepared yellow clay (YC) using one of the most widely used methods, for the preparation of heterogeneous catalysts, which is the wet impregnation method (IPM) and its application as a heterogeneous catalyst for Caffeine (CAF). Several catalysts Cooper Nickel's Catalysts (Cu-Ni) were applied to the yellow clay with different weight ratio of Cu and Ni, in order to explore the role of both metals during the catalytic oxidation process CWPO. Furthermore, the CuNi-YC catalysts, were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Langmuir's surface area, Brunauer Emmett Teller (BET), scanning electron microscope (SEM) and inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), so as to get a better understanding concerning the catalytic activity's behavior of CuNi-YC catalysts. The optimization of the catalytic activity's effects on the different weight ratios of Cu and Ni, temperature and H2O2 were also examined, using Box-Behnken Response Surface Methodology RSM to enhance the CAF conversion. The analysis of variances (ANOVA) demonstrates that Box-Behnken model was valid and the CAF conversion reached 86.16%, when H2O2 dosage was equal to 0.15 mol.L-1, copper impregnated (10%) and temperature value attained 60 °C. In addition, the regeneration of catalyst's cycles under the optimum conditions, indicated the higher stability up to four cycles without a considerable reduction in its conversion performance.

Efficient degradation of sulfamethoxazole by catalytic wet peroxide oxidation with sludge-derived carbon as catalysts.

Sulfamethoxazole (SMX) is a commonly used antibiotic for both human and animals. The frequent detection of SMX in natural water bodies and sediment has become an issue of great environmental concern due to its potential risk to induce antibiotic resistance in pathogenic bacteria. In the present work, the catalytic wet peroxide oxidation (CWPO) was investigated to remove SMX with sludge-derived carbon (SC) as a cheap alternative catalyst. Different acids were used to modify SC. It was found that SC modified with sulphuric acid (SC-H2SO4) demonstrated the best catalytic activity. The removal efficiency of SMX and TOC was 97.7% and 65.7%, respectively, after 260 min, at pH 5 with a dosage of 220 mg/L H2O2. The effects of temperature, initial pH and H2O2 dosage were also investigated. The study demonstrated that the increase of temperature could significantly improve the degradation of SMX from 10.0% at 20°C to 94.7% at 60°C.

Iron-loaded carbon nanotube-microfibrous composite for catalytic wet peroxide oxidation of m-cresol in a fixed bed reactor.

A kind of novel iron-loaded carbon nanotube-microfibrous composite (Fe2O3-CNT-MF) catalyst is prepared and tested for fixed bed m-cresol catalytic wet peroxide oxidation (CWPO) reaction. Results show that the Fe2O3-CNT-MF can significantly decline the pressure drop of the fixed bed. Higher temperature, lower feed flow rate, higher catalyst bed height, and higher H2O2 dosage are beneficial to m-cresol degradation. Lower pH can also improve m-cresol degradation, but it will cause severe iron leaching. The highest m-cresol removal (over 99.5%) and total organic carbon (TOC) removal (53.6%) can be observed under condition of 2 cm bed height, flow rate of 2 mL/min, reaction temperature of 70 °C, 6 g/L H2O2, and initial pH = 1. Meanwhile, the Fe2O3-CNT-MF catalyst shows good stability with less than 10% decrease in m-cresol conversion and 7% decrease in TOC conversion after 24-h reaction and less than 2 mg/L iron leaching is observed in all conditions except for strong acid condition. Two probable pathways of m-cresol degradation process are presented. Under most conditions, m-cresol will first be turned into methylhydroquinone, followed by oxidation to p-toluquinone. In basic condition, some m-cresol will first be changed into 4-methylpyrocatechol. These aromatic intermediates will then be oxidized into some small molecular acids and finally be mineralized to CO2 and H2O.

Synthesis of graphene with different layers on paper-like sintered stainless steel fibers and its application as a metal-free catalyst for catalytic wet peroxide oxidation of phenol.

Different layers of graphene (Gr) films are prepared on the paper-like sintered stainless steel fibers (PSSF) support with three-dimensional structure by CVD method. The effects of acetylene flow rate, deposition time, and deposition temperature on the properties of PSSF-Gr are investigated by EDS, AFM, SEM, TEM, and Raman spectroscopy, respectively. Then, the catalytic performances of PSSF-Gr with different layers of Gr films as metal-free catalysts for catalytic wet peroxide oxidation (CWPO) of phenol are assessed in the continuous fixed-bed reactor. The catalytic results demonstrate that the PSSF-Gr catalyst with single layer graphene film achieves the best catalytic performance (phenol and TOC removal efficiency reach 99% and 73%, respectively) after continuously operating for 6 h. Under the treatment of the PSSF-Gr catalyst with single-layer graphene, total phenol oxidation and excellent TOC removal (maintain about 71%) have been achieved for the long-term operation (38 h). Moreover, the phenol conversion of blank experiment (without catalyst) and PSSF are around 40%, which are caused by thermal degradation and thus, the excellent catalytic activity of PSSF-Gr is ascribed to graphene. Like other Fenton's catalysts, the catalytic mechanism of PSSF-Gr catalyst in phenol degradation is also a ·OH mechanism.

Boosting the catalytic activity of natural magnetite for wet peroxide oxidation.

This work explores the modification of naturally occurring magnetite by controlled oxidation (200-400 °C, air atmosphere) and reduction (300-600 °C, H2 atmosphere) treatments with the aim of boosting its activity in CWPO. The resulting materials were fully characterized by XRD, XPS, TGA, TPR, SEM, and magnetization measurements, allowing to confirm the development of core-shell type structures. The magnetite core of the solid remained unchanged upon the treatment whereas the Fe(II)/Fe(III) ratio of the shell was modified (e.g. 0.42, 0.11 and 0.63 values were calculated for pristine Fe3O4, Fe3O4-O400, and Fe3O4-R400, respectively). The performance of the catalysts was tested in the CWPO of sulfamethoxazole (SMX) (5 mg L-1) under ambient conditions and circumneutral pH (pH0 = 5), using the stoichiometric dose of H2O2 (25 mg L-1) and a catalyst load of 1 g L-1. The key role of the ferrous species on the mineral shell was evidenced. Whereas the oxidation of magnetite led to significantly slower degradation rates of the pollutant, its reduction gave rise to a dramatic increase, achieving the complete removal of SMX in 1.5 h reaction time with the optimum catalyst (Fe3O4-R400) compared to the 3.5 h required with the pristine mineral. A reaction mechanism was proposed for SMX degradation, and a kinetic equation based on the Eley-Rideal model was accordingly developed. This model successfully fitted the experimental results. The stability of Fe3O4-R400 was evaluated upon five sequential runs. Finally, the versatility of the catalytic system was proved in real environmentally relevant water matrices.