Catalytic Wet Peroxide Oxidation Process Research Articles

Simultaneous degradation of cyanobacteria and cyanotoxins by catalytic wet peroxide oxidation: Impact of morphology and growth stage

The widespread proliferation of potentially toxic cyanobacteria in source waters for drinking water treatment plants (DWTPs) presents a pressing contemporary challenge. Although catalytic wet peroxide oxidation (CWPO) has been recognized as a highly effective and environmentally friendly technology for removing cyanotoxins from water, the simultaneous degradation of cyanobacteria and cyanotoxins has been scarcely investigated. Considering their great morphological diversity, in this work, the impact of the presence of pure strains of several species of toxic and non-toxic cyanobacteria on the degradation of relevant cyanotoxins has been evaluated considering also the main stages of their life cycle. In each studied scenario, achieving a full eradication of the cyanobacteria also led to the complete elimination of the cyanotoxin, including both intra and extracellular fractions. Morphological factors, including filament and cell sizes, play a crucial role in the efficiency of the process. Small cells and long filaments entail a higher presence of particulate organic matter, which consumes hydroxyl radicals considerably in competence with the cyanotoxin degradation. Moreover, the growth stage emerges as a pivotal factor in understanding the CWPO process performance, with cyanobacteria in their early life stages, exhibiting more pronounced interference compared to later stages, probably due to their higher cell viability and accelerated metabolism. All these understandings are essential for the successful implementation of the technology in treating surface waters affected by toxic cyanobacterial blooms.

Performance of catalytic wet oxidation on thermochemical aqueous effluents assessed by FT-ICR MS

Aqueous phase (AP) is frequently observed in bio-oil from biomass thermochemical conversion or as an upgrading coproduct. However, AP contains high organic content that can be toxic and that must be reduced or removed to be then treated in existing wastewater plants. A promising method to upgrade these APs is the catalytic wet peroxide oxidation (CWPO) that was applied here on APs of both hydrothermal liquefaction and pyrolysis bio-oils from softwood and hardwood. Efficiency of the CWPO was assessed by investigating the molecular composition of raw and treated APs by ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with electrospray ionization (ESI) in negative- and positive-ion modes. Combination of FT-ICR MS and multivariate statistical analyses evidenced efficiency of the process with new compounds resulting from the oxidative depolymerization, characterized by lower unsaturation degree and molecular weight, and higher oxygen atom count. Refractory compounds were also observed, which are notably characterized by high unsaturation degrees. Interestingly, both detection modes were shown to be complementary for the understanding of the CWPO process. ESI (-) allowed to assess the completion of the oxidation process in detecting carboxylic acid conversion products and to specifically evidence refractory products. ESI (+) was informative on the CWPO process, especially on the conversion of the basic compounds, with the decrease of the detected species. Eventually, softwood AP was shown to be more reluctant to CWPO than the hardwood one.

Efficient degradation of phenol wastewater using CuFe2O4 as highly active catalyst in the microwave-assisted catalytic wet peroxide oxidation process

Six kinds of CuFe2O4, including capsule-shaped CuFe2O4-C, plate-shaped CuFe2O4-P, polyhedral-shaped CuFe2O4-O, and irregular shaped catalysts prepared by co-precipitation (CuFe2O4-CO), by microwave heating (CuFe2O4-MW), and by hydrothermal synthesis (CuFe2O4-S), were used in the microwave-assisted catalytic wet peroxide oxidation (MW-CWPO) process to remove phenol from wastewater. The physicochemical properties of the catalysts were dependent on preparation methods. The catalytic activities were in the order of CuFe2O4-CO (95.3 %) >> CuFe2O4-P (78.8 %) > CuFe2O4-C (72.7 %) > CuFe2O4-MW (67.1 %) > CuFe2O4-S (63.3 %) > CuFe2O4-O (60.0 %). Effects of CuFe2O4-CO dosage, H2O2, pH, phenol initial concentration, anions, and MW in the MW-CWPO process were then systematically studied. Under optimal conditions of pH = 3, H2O2 = 1 mL/L, and CuFe2O4-CO = 0.5 g/L, MW energy of 99 kJ (550 W, 3 min) and 132 kJ (550 W, 4 min) were found essential to achieve 99.6 % removal rate of phenol and 95.3 % removal rate of chemical oxygen demand (COD). Possible degradation pathways were suggested: phenol was firstly oxidized into hydroquinone and catechol, which further degraded into p-benzoquinone, 1,2-benzoquinone, respectively. Finally, these compounds transformed into oxalic acid, CO2, and H2O within 4 min. The proposed mechanism suggested that the catalyst CuFe2O4-CO generates more “hot spots” due to its irregular shape, which enhances MW scattering and absorbing abilities. Consequently, the chemical composition and crystal structure of the catalyst significantly promote the decomposition of H2O2 to generate free radicals. The CuFe2O4-CO has an opportunity of potential engineering application due to its high efficiency and stability.

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.

Catalytic wet peroxide oxidation of metronidazole over Fe and Mn supported UiO-66 catalysts: Kinetic study

The metronidazole (MNZ) antibiotic is widely used to treat infections caused by anaerobic bacteria and it is difficult to biodegrade in the pharmaceutical wastewaters. In this study, Fe-UiO-66, Mn-UiO-66 and Fe/Mn-UiO-66 catalysts were prepared for the kinetic study of catalytic wet peroxide oxidation (CWPO) degradation of metronidazole in pharmaceutical wastewater. The catalysts were characterized by XRD, FT-IR, N2 adsorption-desorption, SEM, and TGA. The effects of Fe and Mn loading rate, catalyst dosage, MNZ concentrations, calcined temperature of Mn-UiO-66 and Fe/Mn ratio on the CWPO of metronidazole wastewater were systematically studied. Fe-UiO-66 catalysts exhibited better catalytic activity for the CWPO degradation of metronidazole wastewater (XMNZ = 93 %, XH2O2 = 78 %) compared to Mn-UiO-66 catalysts (XMNZ = 20 %, XH2O2 = 30 %). The kinetics study indicates that the CWPO process is fitted for the pseudo-first-order reaction with activation energy of 89.37 kJ/mol and 95.08 kJ/mol obtained on the Fe-UiO-66 and 2Fe/Mn-UiO-66 catalysts, respectively. The supported Fe and Mn UiO-66 catalysts showed good catalytic activity for CWPO of metronidazole which exhibited potential application in the wastewater treatment process.

Carbon Nanomaterials from Polyolefin Waste: Effective Catalysts for Quinoline Degradation through Catalytic Wet Peroxide Oxidation

Quinoline (QN) is highly toxic and carcinogenic and has been detected in soil, groundwater, and biological tissues. Advanced oxidation processes (AOPs) have shown promise to address its degradation in wastewater treatment, with catalytic wet peroxide oxidation (CWPO) being highlighted due to its cost-effectiveness and mild operation. However, developing active and inexpensive catalysts is crucial for CWPO’s effectiveness. Another pressing issue is the accumulation of mixed, dirty plastic solid waste (PSW), particularly polyolefins used in packaging. Although recycling rates have increased, much plastic packaging remains in landfills. However, polyolefins can be converted into carbon-based nanostructured materials (CNMs), such as carbon nanotubes (CNTs), through chemical vapor deposition (CVD) using PSW as a carbon precursor. While many studies focus on CNT preparation, their application is often overlooked. In this context, this work proposes the preparation of CNMs, particularly CNTs, through CVD using a single-stage pyrolysis reactor. Polyolefins (LDPE, HDPE, and PP), both individually and in a mixture simulating PSW, were used as carbon sources. Given a sufficiently high temperature, the desired CNT architecture was successfully synthesized regardless of the starting polymer. These CNMs were then tested as catalysts for CWPO in simulated wastewater containing QN. The results showed a rapid degradation of QN (30–120 min) and high removals of total organic carbon (TOC) and aromatic compounds (75% and >90%, respectively), demonstrating the applicability of PSW-derived CNTs in the CWPO process for QN abatement.

Highly active Mn-Cu bimetallic oxide catalyst assembled as 3D-printed monolithic agitating paddles for advanced oxidation process

Catalytically agitating paddles are essential to perform liquid-solid heterogeneous catalytic reactions on an industrial scale due to the improved mass transfer and easy catalyst recovery. Herein, bimetallic oxides were formed after the calcination of nanomaterials derived from metal-organic frameworks (MOFs). Particularly, Mn(M)-BTC nanomaterials were synthesized by self-assembly of Mn2+ ions (mixed with various dopants such as Cu2+, Ce3+, or Fe2+) and H3BTC ligands in a mixed solvent of ethanol and water. It was found that in the powdery form, the Mn-Cu oxide derivate exhibited the highest degradation rate in the catalytic wet peroxide oxidation process (CWPO process), which was significantly higher than that of single metal oxide as well as Mn-Fe and Mn-Ce oxide derivates. The reason was caused by the synergistic effect between Mn-Cu promoted the formation of Mn3+ and Cu+ species to boost the CWPO reaction. Furthermore, the obtained Mn-Cu powdery catalysts were 3D-printed to obtain monolithic agitating paddles with different geometries, which were then mounted on a central shaft in the stirred reactor. An advanced oxidation process was used to investigate the effect of 3D patterns on the degradation efficiency of various organic dyes. It was discovered that the 3D-printed grid with higher cell density (484 cpsi) had better liquid mixing efficiency and thus better catalytic performance, which could be repeatedly used more than seven times. Additionally, the numerical simulation analysis (computational fluid dynamics) revealed a good mixing efficiency and improved mass transfer in the entire reactor equipped with the designed monolithic agitating impellers.

Coupling photocatalytic water oxidation on decahedron BiVO4 crystals with catalytic wet peroxide oxidation for removing organic pollutions in wastewater

Catalytic wet peroxide oxidation (CWPO) is widely used to remove organic pollutants in industrial wastewater, however, the remained challenges in circulating Fe3+/Fe2+ ions, inevitably forming iron sludge and massively consuming H2O2 limit its applications. Herein, the coupling of CWPO and photocatalytic water oxidation on decahedron BiVO4 crystals was reported to solve the above challenges. Using spatial photogenerated charge separation between different facets of BiVO4, efficiently circulating Fe3+ to Fe2+ was realized with a selectivity of ~100%, which greatly inhibits the formation of iron sludge. Moreover, in-situ formation of H2O2 through two-hole-involved photocatalytic water oxidation on BiVO4 replenishes the H2O2 consuming in the CWPO process. The coupling system exhibits a much higher total organic carbon (TOC) removal than the CWPO process in various pollutants, giving an improvement of rate constant to more than 10 times. This work provides a potential coupling route for advanced degradation of organic pollutants in wastewater treatment.

Catalytic wet peroxide oxidation of phenolic wastewater on novel Cu/Mn-UiO-66@Al2O3 ceramic tube membrane catalysts

Novel Cu and Mn supported UiO-66@Al2O3 ceramic tube (UiO-66CT) membrane catalysts were synthesized by solvothermal method combined with secondary incipient wetness impregnation method and used for efficient catalytic wet peroxide oxidation (CWPO) of phenolic wastewater. Synthesis conditions of UiO-66CT were optimized by investigating the secondary soaking times and UiO-66 content. The experimental set-up based on a novel membrane reactor was designed for the catalytic activity evaluation of the ceramic tube catalysts. Results indicated that solvothermal time of 24 h and secondary soaking time of 1 h in the UiO-66 (12.8 g/L) can effectively shorten the synthesis time with a UiO-66 loading ratio about 2.0 wt% obtained. The SEM and EDS mapping results certificated the loading of UiO-66 in the macro-pores of the ceramic tube and the successfully supporting of Cu species on the UiO-66CT. The Cu-UiO-66CT catalysts exhibited good catalytic activity (Xphenol > 99% without toxic by-products detected in the final treated wastewater). By contrast, the Mn-UiO-66CT catalysts exhibited lower catalytic activity because of the fast decomposition of H2O2 on the MnO2 catalysts. The Cu-UiO-66CT catalyst showed excellent stability with phenol conversion (initial concentration of 500 ppm) kept above 90% after reused for 5 times. The immobilization of UiO-66 into the macro-pores of Al2O3 ceramic tube and the supporting of Cu species in the UiO-66CT can not only keep the high activity of MOFs catalysts but also enhance the stability of Cu-UiO-66 in the CWPO process. This research provides a promising strategy to solve the unstability of MOFs catalysts when used for the CWPO process of wastewaters.

Magnetite-Based Catalyst in the Catalytic Wet Peroxide Oxidation for Different Aqueous Matrices Spiked with Naproxen–Diclofenac Mixture

Magnetite supported on multiwalled carbon nanotubes catalysts were synthesized by co-precipitation and hydrothermal treatment. The magnetic catalysts were characterized by X-ray diffraction, Fourier-transform infrared spectrometry, thermogravimetric analysis and N2 physisorption. The catalysts were then tested for their ability to remove diclofenac (DCF) and naproxen (NAP) from an aqueous solution at different conditions (pH, temperature, and hydrogen peroxide) to determine the optimum conditions for chemical oxidation. The optimization of the process parameters was conducted using response surface methodology (RSM) coupled with Box–Behnken design (BBD). By RSM–BBD methodology, the optimal parameters (1.75 mM H2O2 dosage, 70 °C and pH 6.5) were determined, and the removal percentages of NAP and DCF were 19 and 54%, respectively. The NAP–DCF degradation by catalytic wet peroxide oxidation (CWPO) was caused by •OH radicals. In CWPO of mixed drug solutions, DCF and NAP showed competitive oxidation. Hydrophobic interactions played an important role during the CWPO process. On the other hand, the magnetic catalyst reduced its activity after the second cycle of reuse. In addition, proof of concept and disinfection tests performed at the operating conditions showed results following the complexity of the water matrices. In this sense, the magnetic catalyst in CWPO has adequate potential to treat water contaminated with NAP–DCF mixtures.

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.

Graphite as catalyst for UV-A LED assisted catalytic wet peroxide oxidation of ibuprofen and diclofenac

Ibuprofen (IBU) and Diclofenac (DCF) are two of the most common non-steroidal anti-inflammatory drugs used worldwide. Their occurrence in natural streams, as contaminants of emerging concern, evidences the inefficiency of conventional wastewater treatment plants for their removal. The photocatalytic methods developed so far usually demand either highly energetic light sources working in the UV-C range, or exclusive tailor-made catalysts, which compromise the economy of the process. In this work, IBU and DCF degradation are addressed in a UV-A LED (395 nm) assisted Catalytic Wet Peroxide Oxidation process using graphite as catalyst. Total IBU and DCF removal is achieved in t < 60 min working at [IBU or DCF]0: 20 µM, [H2O2]0: 800 µM, [Graphite]: 1 g · L−1 and pH0:3.0, with a 53% TOC removal and ECTOC: 31.0 kWh gTOC−1. Results show a high influence of the interaction between the graphite's surface and H2O2, which enables pollutant adsorption as first step in the oxidation reaction. Further redox reactions on the graphite surface lead to the cleavage of the reaction intermediates, making active sites available again. Nonetheless, in absence of an external energy source this process is very slow. UV-A radiation promotes these reactions as well as H2O2 decomposition into hydroxyl and hydroperoxyl radicals, enhancing the contaminant removal rate. The UV-A assisted CWPO process is also effective in surface water and WWTP effluent. Furthermore, graphite shows a great stability in IBU removal from WWTP effluent upon five consecutive cycles.

Understanding the active sites of boron nitride for CWPO: An experimental and computational approach

Hexagonal boron nitride (h-BN) has been explored as a catalyst for degrading persistent organic pollutants in wastewater by Catalytic Wet Peroxide Oxidation (CWPO). Herein, the superior activity of the h-BN on the phenol degradation (model pollutant) compared to other metal-free catalysts, such as carbon-based ones, and the lower selectivity to CO encourage the potential application of h-BN catalysts in CWPO processes. Through a combined density functional theory calculations, experimental reactions and catalyst characterization approach, a comprehensive study on the reaction mechanism has been conducted. According to this, only defected B atoms in the h-BN layer, protonated as B-(OH2)+, decompose the hydrogen peroxide into highly reactive hydroxyl radicals. The radical species diffuse towards inner h-BN regions and react with the phenol adsorbed by π-π interaction on the h-BN surface. Oxidation by-products cause carbonaceous deposits and progressive deactivation of the h-BN catalyst that can be directly regenerated by burning off in air.

Degradation of MO and H2O2 on Cu/γ‐Al2O3 pellets in a fixed bed reactor: Kinetics and transport characteristics

AbstractPelletized Cu catalysts (Cu/γ‐Al2O3) with different diameters (dp = 1.1–4.2 mm) were prepared and examined kinetically for methyl orange (MO) degradation using a fixed bed reactor. A Cu/γ‐Al2O3 catalyst (dp = 2.3 mm) exhibited high degradation activity (Conv.MO &gt; 95%) and superior leaching resistance (Cu leaching &lt;0.6 mg/L in 200 hr). Apparent kinetics showed that both MO degradation and H2O2 decomposition were mainly controlled by internal mass transfer. A plug‐flow reactor model with mass‐transfer coefficients was developed, and a modified empirical correlation for external mass transfer (Sh = 1.5Re'1.10Sc0.42) was proposed to accurately describe the species transport from/to the catalyst pellets in the low Reynolds number regime. The model was verified against conversions of pollutants degradation and H2O2 decomposition separately in a fixed bed with relative errors &lt;5% compared with experimental data; thus, it could be used as an effective tool for further design and optimization of reactor configuration and reaction conditions for the continuous catalytic wet peroxide oxidation process.

Cu/UiO-66: a novel nanocatalyst obtained by a microwave-assisted protocol in DMF-free media for the efficient phenol removal via catalytic wet peroxide oxidation

This paper analyzes the microwave-assisted synthesis of the zirconium-based metal-organic framework (MOF) UiO-66 using acetone as a solvent, in replacement of the traditional and toxic N,N-Dimethylformamide (DMF). It also studies the subsequent loading of this MOF with high amounts of dispersed copper species to be used as catalyst in the advanced oxidation of phenol. To this purpose, the structural development of UiO-66 was monitored studying the effect of synthesis variables such as stirring, temperature, treatment time and volume of the mixture. In this way, a high-crystallinity UiO-66 was obtained with high yields (88 %) at short times (6 h) and under mild conditions (80 °C) in a DMF-free media. Subsequently, by studying treatment conditions, a Cu/UiO-66 catalyst supporting high loadings (10 wt. %) of highly dispersed copper species (Cu+/Cu2+) was obtained. This nanocatalyst, which was obtained following sustainability criteria, exhibited a high performance in the catalytic wet peroxide oxidation (CWPO) of phenol, quickly converting all the phenol at 70 °C in the first 5 min and reaching a mineralization (TOC removal) of 88 % and a H2O2 consumption efficiency of 30 % at 120 min. Cu/UiO-66 represents a new nanostructured catalyst based on highly dispersed copper species to be applied in CWPO processes.

Simulation and Optimization of the CWPO Process by Combination of Aspen Plus and 6-Factor Doehlert Matrix: Towards Autothermal Operation

This work aims to present an industrial perspective on Catalytic Wet Peroxide Oxidation (CWPO) technology. Herein, process simulation and experimental design have been coupled to study the optimal process conditions to ensure high-performance oxidation, minimum H2O2 consumption and maximum energetic efficiency in an industrial scale CWPO unit. The CWPO of phenol in the presence of carbon black catalysts was studied as a model process in the Aspen Plus® v11 simulator. The kinetic model implemented, based on 30 kinetic equations with 11 organic compounds and H2O2 involvement, was valid to describe the complex reaction network and to reproduce the experimental results. The computer experiments were designed on a six-factor Doehlert Matrix in order to describe the influence of the operating conditions (i.e., the different process temperatures, inlet chemical oxygen demands, doses of H2O2 and space time) on each selected output response (conversion, efficiency of H2O2 consumption and energetic efficiency) by a quadratic model. The optimization of the WPO performance by a multi-criteria function highlighted the inlet chemical oxygen demand as the most influential operating condition. It needed to have values between 9.5 and 24 g L−1 for autothermal operation to be sustained under mild operating conditions (reaction temperature: 93–130 °C and pressure: 1–4 atm) and with a stoichiometric dose of H2O2.

UV-assisted Catalytic Wet Peroxide Oxidation and adsorption as efficient process for arsenic removal in groundwater

Arsenic is a toxic and carcinogenic element present in groundwater as arsenite, As(III) and/or arsenate, As(V), due to natural lixiviation or because of anthropogenic activities. The World Health Organization threshold in drinking water is 10 μg/L, well below the concentration found in the water resources of numerous populations, as in the Duero basin (Spain). As(V) can be easily removed by adsorption onto iron-based adsorbents, whereas As(III) is harder to remove. Therefore, in this work we propose the use of ilmenite (FeTiO3), a low-cost catalyst, as both photocatalyst and adsorbent in the UV-A assisted Catalytic Wet Peroxide Oxidation process. The main aim of this technology is to oxidize arsenite into arsenate, for its subsequent adsorption onto the Fe sites of the catalyst. This technology has proven to be effective for the oxidation and removal of 10 mg/L As(III) working at 1000 mg/L ilmenite, 60 mg/L H2O2, 0, pH0: 7 and room temperature (25 °C), in both ultrapure water and groundwater collected from Lastras de Cuéllar (Segovia, Spain). Furthermore, we propose a complete kinetic model which comprises the H2O2 decomposition, As(III) oxidation and As(V) adsorption, which is in agreement with the experimental data.

Catalytic wet peroxide oxidation of phenol on Fe-ZSM-5/PSSF membrane catalysts: Effect of framework Fe by hydrothermal synthesis

Two kinds of zeolite membrane catalysts, Fe–ZSM-5/PSSF and Fe2O3/ZSM-5/PSSF, were synthesized by hydrothermal method and incipient wetness impregnation method respectively, and tested for catalytic wet peroxide oxidation (CWPO) of phenol in the fixed bed reactor. The paper-like stainless steel fiber (PSSF) were prepared by a combined papermaking and sintering process. Then hydrothermal and impregnation methods were applied to coat Fe–ZSM-5 as well as Fe2O3/ZSM-5 membrane catalyst on PSSF respectively. Framework Fe3+ species on the Fe–ZSM-5/PSSF zeolite membrane catalysts were characterized and tested for phenol oxidation in the fixed bed reactor. In addition, the effects of Si/Fe, temperature and residence time on catalyst performance were investigated. Results showed that Fe–ZSM-5/PSSF with Si/Fe = 120 showed highest activity. Higher temperature and longer residence time can improve the catalytic performance and the existence of the framework Fe3+ species over Fe–ZSM-5/PSSF can enhance the catalytic efficiency of phenol, with phenol conversion of over 99.0% and TOC conversion of 55.6% under condition of 4 cm bed height, 2 mL/min feed flow rate and 80 °C. Catalytic activity of Fe–ZSM-5/PSSF was dramatically increased compared to the Fe2O3/ZSM-5/PSSF, indicating the key role of framework Fe3+ played in the CWPO process. Finally, the stability test results showed that a relatively low decrease in activity of Fe–ZSM-5/PSSF (Si/Fe = 120) can be found after three consecutive runs (21 h).

The influence of the catalyst on the CO formation during catalytic wet peroxide oxidation process

Herein, the formation of carbon monoxide as a harmful product upon the Catalytic Wet Peroxide Oxidation process is studied in presence of different solid catalysts: an iron supported activated carbon catalyst, a metal-free catalyst based on Graphene Nanoplatelets, and 1.6 wt.% Fe containing Cr2AlC MAX phase catalyst. The CWPO performance and the evolution of the gas effluent have been compared to that obtained in a conventional Fenton process.Carbon monoxide yield released was significantly lower in Catalytic Wet Peroxide Oxidation process in relation to that obtained in the Fenton process, where CO concentration reaches a maximum of 6651 mg/Nm3. By contrast, in presence of activated carbon-Fe catalyst and, notably, Graphene Nanoplatelets and Cr2AlC MAX phase catalysts, a more progressive phenol and aromatics intermediates oxidation resulted in a much lower CO maximum concentration in the gas phase at the exit of the reactor of 2454 mg/Nm3, 170 mg/Nm3 and 187 mg/Nm3, respectively.Hence, when compared to the homogeneous Fenton oxidation, Catalytic Wet Peroxide Oxidation process results be a more sustainable treatment for high-loaded phenolic wastewaters by decreasing the hazardous CO gaseous emissions avoiding this way a secondary pollution during the oxidation process.

Editorial Catalysts: Special Issue on Trends in Catalytic Wet Peroxide Oxidation Processes

The catalytic wet peroxide oxidation (CWPO) process is an advanced oxidation technology that has shown great potential for the decontamination of wastewater [...]