Fenton-like System Research Articles

Fenton-reaction-aid selective delignification of lignocellulose by Inonotus obliquus to improve enzymatic saccharification

Aiming at improving the efficiency of recovering sugars from wheat straw by the white rot fungus Inonotus obliquus in solid-state fermentation, two Fenton-reaction-aid systems, i.e., one system containing Fenton reaction pretreatment (FRP) and subsequent Inonotus obliquus culture, one system composed of fungal combined treatment with Fe3O4 nanomaterials (NMs), were developed. FRP and NMs improved the fungal growth and degradation efficiency of wheat straw (WS) by regulating ligninolytic enzyme secretion with manganese peroxidase (MnP) (471.0, 359.8 IU g−1), lignin peroxidase (LiP) (108.0, 48.6 IU g−1), and laccase (Lac) (18.0, 13.4 IU g−1) in the FRP group and NMs group within 15 days. Hemicellulose removal on Day 5 and delignification on Day 10 in FRP group (51.3 % and 20.93 %) and NMs group (40.7 % and 12.60 %) were more severe than the control group (19.2 %, 7.37 %). Sugar yield and conversion rate of 10-day-cultured FRP-WS were 228.4 g kg−1 and 37.2 %, 2.1 and 2.6 times higher than that of 10-day-cultured raw WS. Synergism of Fenton reaction and white-rot fungus quickened fermentation period, promoted degradation selectivity, and then subsequent enzymatic hydrolysis. The Fenton-like system established by NMs and I. obliquus made the synergistic system simpler and represented biocompatible chemistry for developing novel microbial cell factories.

Carbon-doped defect MoS2 co-catalytic Fe3+/peroxymonosulfate process for efficient sulfadiazine degradation: Accelerating Fe3+/Fe2+ cycle and 1O2 dominated oxidation

In order to accelerate Fe3+/Fe2+ cycle and boost singlet oxygen (1O2) generation in peroxymonosulfate (PMS) Fenton-like system, a co-catalyst of defect MoS2 was prepared by C doping and C2-MoS2/Fe3+/PMS system was structured. The removal efficiency of sulfadiazine (SDZ) antibiotics was nearly 100 % in 10 min in the system under the appropriate conditions ([co-catalysts] = 0.2 g/L, [PMS] = 0.1 mM, [Fe3+] = 0.4 mM, pH 3.5), and the reaction rate constant was 4.6 times that of Fe3+/PMS system. C doping MoS2 could induce phase transition, yield more sulfur defects, and expedite electron transfer. Besides, exposed Mo4+ sites on C2-MoS2 could significantly enhance the regeneration and stability of Fe2+ and further promote the activation of PMS. ·OH, SO4·−, and 1O2 were responsible for SDZ degradation in the system. Notably, 1O2 generation was efficiently promoted by sulfur defects and CO sites on C2-MoS2, and 1O2 played the main role in SDZ degradation. Therefore, this co-catalytic system exhibited great anti-interference and stability, and organic contaminants could be efficiently and stably degraded in a 14-day long-term experiment. This work provides a new approach for improving the co-catalytic performance of MoS2 for Fe3+ mediated Fenton–like technology, and offers a promising antibiotic pollutant removal strategy.

Overlooked self-catalytic mechanism in phenolic moiety-mediated Fenton-like system: Formation of Fe(III) hydroperoxide complex and co-treatment of refractory pollutants

Applications of Fenton-like reactions (Fe(III)/H2O2) without catalyst have low efficiency in remediating pollutants. Herein, pollutants containing phenolic moiety (P, e.g., paracetamol (PCM)) were demonstrated to make Fe(III)/H2O2 system highly effective in degrading a wide range of contaminants. Kinetics analysis shows the self-catalytic degradation of PCM with optimum performance at pH 4.0, and Fe(III)/Fe(II) conversion was accelerated without the assistance of cocatalyst. Based on state-of-art spectroscopy measurements and theoretical calculations, the overlooked self-catalytic mechanism was revealed. In the presence of phenolic moiety, a yellow-colored high-spin P-Fe(III)-OOH complex can be formed in Fe(III)/H2O2 system, which subsequently converts to Fe(II). Afterwards, the oxidation of P gives hydroquinone that also facilitates the cycling of Fe(III)/Fe(II). The accumulated Fe(II) reacts with H2O2 to generate hydroxyl radicals, the major species responsible to oxidize pollutants, thereby achieving efficient decontaminant performance. Results provide new insights into the self-catalytic Fenton-like process for remediating a mixture of pollutants.

Investigation of Glyphosate Removal from Aqueous Solutions Using Fenton-like System Based on Calcium Peroxide

Glyphosate [N-(phosphonomethyl)-glycine], an organophosphate broad-spectrum herbicide, is a serious environmental contaminant that poses a significant threat to humans. It can be detected as a contaminant in water; thus, effective procedures for its removal are urgently required. The present study investigated the performance of glyphosate removal from aqueous solutions using a Fenton-like system. Calcium peroxide (CaO2) was used as a source of hydroxyl free radicals with Fe2+ as a catalyst to trigger the Fenton reaction. Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and potassium permanganate titration were carried out for characterization of calcium peroxide. The effect of operating parameters such as pH, the molar ratio of Ca2+:Fe2+, the initial dosage of calcium peroxide, and the initial glyphosate concentration on the removal efficiency was studied, respectively. The maximum total phosphorus (TP) and chemical oxygen demand (COD) removal were 94.50% and 68.60%, respectively, within 120 min under optimal conditions (pH = 3.0, initial glyphosate concentration = 50 ppm, initial CaO2 dosage = 0.5 g, molar ratio of Ca2+:Fe2+ = 6, room temperature). Experimental data were analyzed using zero-order, first-order, second-order, and Behnajady, Modirshahla, and Ghanbary (BMG) kinetics models. The degradation kinetics of glyphosate could be mostly fitted with the BMG kinetics model. This study demonstrated that calcium peroxide could be considered an effective oxidant for glyphosate wastewater treatment.

Mechanistic insights into Fe(II)-citric acid complex catalyzed CaO2 Fenton-like process for enhanced benzo[a]pyrene removal from black-odor sediment at circumneutral pH

Polycyclic aromatic hydrocarbons (PAHs) are found ubiquitously in contaminated aquatic sediments. They are difficult to degrade, particularly the high-molecular-weight PAHs (e.g., benzo[a]pyrene, BaP). In this study, CaO2 assisted with ferrous ion (Fe(II))-citric acid (CA) was applied for the first time in BaP degradation in aquatic sediment. Among the treatment processes we studied, CaO2/Fe(Ⅱ)/CA could effectively degrade BaP at circumneutral pH (7.0 ± 0.3), reaching a maximum of nearly 80% under optimal conditions (0.84 mM CaO2, 0.21 mM Fe(Ⅱ), and 0.35 mM CA in per gram of dry sediment). Contrary to some external environmental factors such as temperature, common metal ions, and natural organic matters, a certain amount of moisture content and inorganic anions (Cl−, SO42−) exhibited a positive effect on BaP degradation, which can probably be contributed to the improved mass transfer rate in the non-homogeneous sediment-water mixture and a higher level of free radicals. The degradation kinetic dominated by hydroxyl radicals included three main stages contribution ∼29.4%, ∼43.1%, and ∼2.4% to BaP degradation, respectively. Based on the theoretical calculations of density functional theory, a pathway for BaP degradation was proposed. For the treatment of actual contaminated sediment, the CaO2/Fe(II)/CA process could realize the elimination of black-odor and effective removal of PAHs from the sediment, as well as negligible ecotoxicity on benthic organisms. This study provides a reference and guidance for the use of CaO2 based Fenton-like systems in treating PAH-contaminated black-odor river sediments.

Investigation of glyphosate removal from aqueous solution using calcium peroxide

Glyphosate, an organophosphate herbicide containing carboxyl group, is widely used in agriculture. It can be found as a contaminant in water, and procedures are required for its removal. The present study investigated the efficiency of glyphosate removal from aqueous solutions using a Fenton-like system. Calcium peroxide (CaO2) was used as a source of hydroxyl free radicals with Fe2+ as the catalyst to trigger Fenton reaction. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and potassium permanganate titration were carried out for characterization of calcium peroxide. The effect of operating parameters such as pH, molar ratio of Ca2+: Fe2+, and initial dosage of calcium peroxide on the total phosphorus (TP) removal efficiency was studied. The maximum TP removal was 94.50% under optimal conditions (pH = 3.0, initial glyphosate concentration = 50 ppm, initial CaO2 dosage = 0.5 g, molar ratio of Ca2+: Fe2+= 6). This study demonstrated that calcium peroxide could be considered as an effective oxidant for glyphosate wastewater treatment.

Disposal of MIEX desorbent at high salinity by ZVI/H2O2 Fenton-like system: Optimization, performance and mechanisms

Magnetic ion exchange resin (MIEX) pretreatment has been widely used to enhance the performance of waterworks, but the high-salinity organic desorbent produced during the resin regeneration is difficult to be safely disposed of. The present study aimed to investigate the removal of DOM and retention of salts from MIEX desorbent via zero-valent iron (ZVI)-assisted Fenton reaction. ZVI/H2O2 mediated Fenton reaction was further validated by various analytical approaches such as 3D-EEM, Molecular weight distribution, Zeta potential, size, dissolution of iron ions, etc. In batch experiments, 73.26% reduction of DOC and 97.66% of UV254 were achieved in 40 min at optimal H2O2 concentration (20 mM), 2 g/L dose of ZVI, and pH of 3, respectively. The removal of organics was ascribed to the direct oxidation of ZVI/H2O2 and flocculation of the iron released during the oxidation. It should be noted that the high concentration of Cl- in system favored the organic removal and its enhanced performance lied in the production and oxidation of HOCl/OCl-. The treated liquid can be reused to regenerate the saturated resin with only a small amount of salt supplementation to obtain a similar recovery performance to that of a freshly configured 10% NaCl solution. Moreover, the retrieval and utilization of ZVI particles and other properties of MIEX desorbent after ZVI/H2O2 treatment were all promising and up to the mark: after four reuses, the mineralization of organic matter differs by 8.81% from the first time, which could be compensated by supplying new ZVI. This research will facilitate the recycling of resin desorbate and expand the market for MIEX applications.

FeOx nanoclusters decorated TiO2 for boosting white LED driven photocatalytic Fenton-like norfloxacin degradation

The treatment of water pollution caused by antibiotic residues is essential for human health and the ecological environment. Herein, FeOx nanoclusters modified TiO2 nanofibers (FeOx-TNFs) heterostructure was fabricated for efficient photocatalytic Fenton-like removal of antibiotic norfloxacin (NOR) under white LED irradiation. Compared with the pristine TiO2, the optimized FeOx-TNFs heterostructure displays much-increased photocatalytic Fenton-like activity, with NOR removal by 92 % within 5 h by visible-light-driven photocatalytic Fenton-like reactions. The efficient NOR degradation activity should be mainly ascribed to the extended optical light absorption in visible light region and accelerated separation and migration of photogenerated carriers of TiO2 by the surface FeOx nanoclusters modification. This highly benefits the formation of reactive •OH radicals in Fenton-like reaction system and thus leads to great improvement in NOR removal. This study demonstrates an alternative approach of surface engineering to synthesize novel heterostructure for the effective photocatalytic remediation of wastewater containing antibiotic contaminants.

Synthesis of Fe(III)-doping Morchella-like porous magnesium hydroxide for the enhanced heterogeneous Fenton degradation of amphoteric antibiotics and anionic dyes

A Morchella-like hierarchical porous Fe-doping magnesium hydroxide (Fe(III)-PMH) was synthesized via a one-step hydrothermal process using iron-bearing brucite with the modulation of recyclable L-threonate. The L-threonate facilitated formatting Morchella-like porous structure through controlling specific lattice plane of Mg(OH)2. The as-prepared Fe(III)-PMH features a high specific surface area porous structure and even distribution of steady Fe(III) active sites doped in Mg(OH)2 lattice, contributing to its degradation of amphoteric antibiotics or anionic dyes in the presence of H2O2. The surface alkalinity of Fe(III)-PMH drives the anionic conversion of amphoteric antibiotics or enhances the ionization of anionic dyes. Then these anionic contaminants are rapidly absorbed and oxidized in situ on the positively charged surface of Fe(III)-PMH. For the stable presence of superoxide radicals in Fe(III)-PMH/H2O2 system, a wide range of working pH was obtained (pH 3–11). Moreover, a negligible amount of leached iron ions, and excellent reusability make it durable and promising for industrial applications. This work provides a simple and low-cost preparation of heterogeneous catalysts with good performance, especially for the highly effective enhanced Fenton-like system in the wastewater treatment of amphoteric antibiotics and anionic dyes.

Enhancing ferric ion/sodium percarbonate Fenton-like reaction with tungsten disulfide cocatalyst for metronidazole decomposition over wide pH range

To overcome the drawbacks of traditional Fenton method, this work proposed the application of tungsten disulfide (WS2) as the cocatalyst to enhance Fe3+ and sodium percarbonate (SPC) Fenton-like system for metronidazole (MTZ) degradation. MTZ was completely removed after 10 min under the optimum conditions with 1.5 g/L WS2, 2 mmol/L SPC, 1.5 mmol/L Fe3+, and pH 7. And the Fe3+/SPC/WS2 could achieve well performance over a wide pH range of 3–11. WS2 could significantly accelerate the Fe3+/Fe2+ circulation and H2O2 disintegration. The electron paramagnetic resonance and quenching tests discovered that the hydroxyl radicals (HO·) and carbonate radicals (CO3·−) were the crucial active species for MTZ decomposition. The surface valence state of WS2 before and after the reaction was analyzed by X-ray photoelectron spectroscopy, and the Fe3+/Fe2+ cycle was proved to be triggered by the conversion of W4+ to W6+. After fifth cycle, the Fe3+/SPC/WS2 still achieved the MTZ degradation efficiency of 75 %. The decomposition byproducts of MTZ and their biotoxicities were determined by mass spectrometry and toxicity estimation software tool, respectively. This investigation provided an effectively idea for antibiotic removal with the WS2 co-catalytic system.

Fe-g-C3N4/reduced graphene oxide lightless application for efficient peroxymonosulfate activation and pollutant mineralization: Comprehensive exploration of reactive sites

To overcome the shortcomings of homogeneous Fe ion activating peroxymonosulfate (PMS), such as high pH-dependence, limited cycling of Fe(III)/Fe(II) and sludge production, graphite carbon nitride (g-C3N4) is chosen as a support for Fe ions, and reduced graphene oxide (rGO) is employed to facilitate the electron transfer process, thereby enhancing catalysis. Herein, a ternary catalyst, Fe-g-C3N4/rGO, is first applied under lightless condition for PMS activation, which exhibits ideal performance for contaminant mineralization. 82.5 % of the total organic carbon (TOC) in 100 mL of 5 mg/L bis-phenol A (BPA) was removed within 20 min by the optimal catalyst named 30%rFe0.2CN, which shows a strong pH adaptability over the range of 3–11 compared with a common Fenton-like system. Moreover, the highly stable Fe-g-C3N4/rGO/PMS catalytic system resists complex water matrices, especially those with high turbidity. To unveil the mechanism of PMS activation and pollutant degradation, the physicochemical properties of the as-prepared catalysts are comprehensively characterized by multiple techniques. The Fe(III) contained in both the Fe-N group and α-Fe2O3 component of 30%rFe0.2CN not only directly reacts with PMS to produce sulfate radicals (SO4−) and hydroxyl radicals (OH), but also combines with PMS to form the essential [Fe(III)OOSO3]+ active complex, thereby generating superoxide radicals (O2−) and singlet oxygen (1O2). Among the various reactive oxidizing species, 1O2 plays an important role in pollutant removal, which is additionally generated by the CO moiety of the catalyst activating PMS as well as PMS self-oxidation, indicating the dominance of the non-radical pathway in the pollutant degradation process. Due to the advantages of high efficiency, wide pH adaptability and stability, the proposed lightless Fe-g-C3N4/rGO/PMS catalytic system represents a promising avenue for practical wastewater purification.

Trace-Dissolved S(-II) Triggers the Fe(III)-Activated H2O2 Process for Organic Pollutant Degradation by Promoting the Fe(III)/Fe(II) Cycle: Kinetics, Toxicity, and Mechanisms

The practical application of the traditional Fenton system (Fe(II)/H2O2) is seriously hampered by the sluggish Fe(III)/Fe(II) cycle and the stringent acidic reaction condition. In this work, we found that trace-dissolved S(-II) (DS(-II), 5 μM) could significantly accelerate the Fe(III)/Fe(II) cycle and trigger a rapid H2O2 activation process in the Fe(III)/H2O2 system. Thus, more hydroxyl radicals (·OH) were generated for the rapid removal of various organic pollutants such as bisphenol A (BPA) and sulfamethoxazole (SMX) from water. Besides, the additive DS(-II) effectively broadened the application pH range of the Fenton or Fenton-like system. The constructed Fe(III)/DS(-II)/H2O2 system showed extensive applicability to different water matrices and maintained high BPA removal in the actual water sources. Furthermore, the toxicity assessment revealed that the toxicity of the target contaminant was diminished. The harmless SO42– was the final product of DS(-II) in the Fe(III)/DS(-II)/H2O2 system, and the residual DS(-II) was less than the threshold limit value for fresh or saltwater (0.5 mg/L). This discovery is expected to promote the large-scale practical application of iron-based Fenton or Fenton-like systems in practical organic wastewater purification.

Fenton-like Remediation for Industrial Oily Wastewater Using Fe78Si9B13 Metallic Glasses

Metallic glasses (MGs) with a unique atomic structure have been widely used in the catalytic degradation of organic pollutants in the recent years. Fe78Si9B13 MGs exhibited excellent catalytic performance for the degradation of oily wastewater in a Fenton-like system for the first time. The oil removal and chemical oxygen demand (COD) removal from the oily wastewater were 72.67% and 70.18% within 60 min, respectively. Quenching experiments were performed to verify the production of active hydroxyl radicals (·OH) by activating hydrogen peroxide (H2O2). The formation of ·OH species can significantly contribute to the degradation reaction of oily wastewater. Fe78Si9B13 MG ribbons were highly efficient materials that exhibited superior reactivity towards H2O2 activation in oily wastewater treatment. The study revealed the catalytic capability of metallic glasses, presenting extensive prospects of their applications in oily wastewater treatment.

Facile and scalable synthesis of Fe-based metal organic frameworks for highly efficient photo-Fenton degradation of organic contaminants

Fe-based metal organic frameworks (Fe-MOFs) being a newly developed photo-Fenton catalyst, have gained ever-increasing attention for environmental remediation, but have been limited by high synthesis cost (high energy-consumption and low yield). In this work, economical and scalable synthesis of Fe-BDC1 (BDC denotes as terephthalic acid) was achieved via facile stirring under ambient condition, and its adsorptive, photocatalytic, Fenton-like and photo-Fenton performances were comprehensively explored against contaminants removal. In comparison, synthesized Fe-BDC2 with the common solvothermal method, the yield of Fe-BDC1 increased 3.4 times. Also, its adsorption capacity towards Rhodamine B (Rh. B) increased about 5.85 times. Moreover, the significantly improved degradation of Rh. B was observed in the Fenton-like and photo-Fenton systems with the increased reaction rate constants up to 4.90 and 2.33 times, respectively. This enhanced catalytic performance of Fe-BDC1 was mainly attributed to the enlarged specific surface area (SSA) and favorable electron separation and migration, resulting into the accelerated ≡Fe(II)/≡Fe(III) cycle and increased yield of reactive oxidative species (ROSs). Additionally, the unique light-induced adsorption enhancement further strengthened the contaminants removal. Fe-BDC1 as photo-Fenton catalyst was found superior over conventional catalysts in terms of advantages including: low dose requirement of catalysts (decrease in an order of magnitude) and H2O2, wide pH working range (3.0–9.0), excellent reusability and stability, universal removal behavior against all organic pollutants, and remarkable synergism between photocatalysis and Fenton-like process with synergistic factor of 77.23%. Moreover, the Fe coordinative unsaturated sites (Fe CUSs) and ·OH were determined as the active sites and the main ROSs, respectively, responsible for highly efficient pollutant degradation. This work gives a feasible solution for the preparation of Fe-MOFs with low synthesis cost and high yield, paving ways for their practical mass application in heterogeneous photo-Fenton oxidation.

Photochemical transformation of sulfadiazine in UV/Fe(II)/sodium citrate Fenton-like system

The persistence and potential hazards of antibiotics in the aquatic environment have attracted worldwide attention. Currently, advanced oxidation technology is considered to be an effective way to degrade antibiotics in the water environment. An enhanced photochemical Fenton-like system was investigated in this study for degradation of antibiotic sulfadiazine (SDZ). The degradation kinetics, pathways, and mechanisms of SDZ in four different photocatalytic systems were studied, including ultraviolet (UV), UV/sodium citrate (SC), UV/Fe(II), and UV/Fe(II)/SC. The highest degradation rate of SDZ was observed in UV/Fe(II)/SC system, and the complexation of SC-Fe(II) promoted photocatalytic efficiency and iron cycling. It was proved that hydroxyl radicals (•OH) were generated in UV/Fe(II)/SC system, but excessive Fe(II) consumed •OH and produced a UV shielding effect, thus reducing the degradation rate of SDZ. In the UV/Fe(II)/SC system, the degradation of SDZ followed pseudo-first-order kinetics, and the reaction rate constant of SDZ reached a maximum of 8.49 × 10−3 min−1, with a degradation efficiency of 97.7%. Even in different real water samples, the removal rate of SDZ can reach about 80%. HCO3−, SO42−, and NO3− in the water environment inhibited the degradation of SDZ, and the order of inhibition was as follows: SO42− > HCO3−>NO3−. With the increase of SDZ concentration and high concentration of humic acid (HA), the degradation rate of the target compound decreased. By identifying the photodegradation products of SDZ, four degradation pathways were proposed, and it revealed that the N–C bond and N–S bond were broken by attacking of hydroxyl groups, where a hydroxyl group replaced the H atom, resulting in the decomposition of SDZ into low molecular weight compounds like SO2, CO2, NO3− and H2O. It suggested that the UV/Fe(II)/SC system has good effect and application prospect in SAs treatment.

Boosting peroxydisulfate Fenton-like reaction by protocatechuic acid chelated-Fe2+ with broad pH range

In this study, a boosted peroxydisulfate (PDS)/Fe2+ Fenton-like system that employing protocatechuic acid (PCA) as complexing reagent to mediate Fe3+/ Fe2+ circulation was established. The outcomes presented typical dyes and antibiotics, such as methyl orange (MO), rhodamine B tetracycline, and metronidazole all can be efficiently eliminated in this synergistic process. Under the optimal conditions (1 mmol L-1 PDS, 30 µmol L-1 Fe2+ and 30 µmol L-1 PCA), the MO removal reached 100% within 80 min at pH 6.7. Furthermore, this system could perform well under the broad pH span (3–7) and realize the effective Fe3+/Fe2+ cycle. The masking test and electron paramagnetic resonance demonstrated sulfate radical (SO4·-), hydroxyl radical, and singlet oxygen were responsible for MO elimination in the cooperative process, and SO4·- was the dominant active substance. The MO decomposition byproducts and their evolutions were researched based on the mass spectrum analysis. The effect of inorganic anions in natural water on the PDS/Fe2+/PCA system was conducted, and the consequences indicated that Cl-, HCO3– and NO3– all negatively influenced the MO elimination. The proposed organic co-catalytic Fenton-like method could promote the development of advanced oxidation processes in water treatment.

WSe2/g-C3N4 for an In Situ Photocatalytic Fenton-like System in Phenol Degradation.

An in situ photo-Fenton system can continuously generate H2O2 by photocatalysis, activating H2O2 in situ to form strong oxidizing ·OH radicals and degrading organic pollutants. A WSe2/g-C3N4 composite catalyst with WSe2 as a co-catalyst was successfully synthesized in this work and used for in situ photo-Fenton oxidation. The WSe2/g-C3N4 composite with 7% loading of WSe2 (CNW2) has H2O2 production of 35.04 μmol/L, which is fourteen times higher than pure g-C3N4. The degradation efficiency of CNW2 for phenol reached 67%. By constructing an in situ Fenton-system, the phenol degradation rate could be further enhanced to 90%. WSe2 can enhance the catalytic activity of CNW2 by increasing electron mobility and inhibiting the recombination of photogenerated electron–hole pairs. Moreover, the addition of Fe2+ activates the generated H2O2, thus increasing the amount of strong oxidative ·OH radicals for the degradation of phenol. Overall, CNW2 is a promising novel material with a high H2O2 yield and can directly degrade organic pollutants using an in situ photo-Fenton reaction.

Effect of Synthesis Conditions on the Catalytic Performances of CuO/Al2O3 in Microwave-enhanced Fenton-like System

Background: In previous work, we successfully prepared CuO/Al2O3 catalysts and evaluated their catalytic activity, kinetics and degradation mechanism for Fenton-like oxidation of p-nitrophenol (PNP) under microwave irradiation. However, we did not study the effect of important preparation parameters on the activities of catalysts. Objective: (1) The effect of preparation conditions: CuSO4 concentration of the impregnating solution, Al2O3 to CuSO4 solution ratio, type and concentration of precipitant and calcination temperature on the physico-chemical properties and catalytic activity were studied. (2) The catalytic performance of the Fenton-like oxidation reaction of PNP under microwave irradiation was evaluated and correlated with the characterization results. (3) The stability and catalytic mechanism of the catalysts were investigated. objective: (1) The effect of preparation conditions: CuSO4 concentration of impregnating solution, Al2O3 to CuSO4 solution ratio, type and concentration of precipitant and calcination temperature on the physico-chemical properties and catalytic activity were studied. (2) The catalytic performance of the Fenton-like oxidation reaction of PNP under microwave irradiation was evaluated and correlated with the characterization results.(3) The stability and catalytic mechanism of the catalysts were investigated. Methods: The CuO/Al2O3 catalyst was prepared by the impregnation deposition method. The 20 g pretreated Al2O3 particles were immersed in 0.6 mol/L Cu (NO3)2 solution and 0.4 mol/L NaOH solution for 24 h before and after. After cleaning and drying, the samples were calcined in an air muffle furnace for 4 h at a certain temperature to obtain CuO/Al2O3 catalyst. Then the catalyst was characterized and catalyzed. method: The CuO/Al2O3 catalyst was prepared by impregnation deposition method. The 20 g pretreated Al2O3 particles were immersed in 0.6 mol/L Cu (NO3)2 solution and 0.4 mol/L NaOH solution for 24 hours before and after. After cleaning and drying, the samples were calcined in an air muffle furnace for 4 hours at a certain temperature to obtain CuO/Al2O3 catalyst. Then the catalyst was characterized and catalyzed. Results: XRD, BET and FESEM results have demonstrated that the catalyst claimed at 300 and 350 ℃ showed a smaller size, a higher specific surface area and a better distribution of the CuO species than their counterparts prepared at higher calcination temperatures. The CuO/Al2O3 catalyst claimed at 300 and 350 ℃ also showed higher removal efficiencies for PNP than other catalysts prepared at higher calcination temperatures. result: XRD, BET and FESEM results have demonstrated that the catalyst claimed at 300 and 350 ℃ showed a smaller size, a higher specific surface area and a better distribution of the CuO species than their counterparts prepared at higher calcination temperatures. the CuO/Al2O3 catalyst claimed at 300 and 350 ℃ also showed higher removal efficiencies for PNP than other catalysts prepared at higher calcination temperatures. Conclusion: It was found that the catalysts prepared at 350 ℃ as calcination temperature showed higher surface area, smaller CuO particle size, and uniform CuO particle size distribution, and consequently showed better catalytic activities with better stability and reusability. Moreover, the XPS results of the catalysts showed a decrease in the Isat/Ip ratio after microwave enhanced Fenton-like reaction, confirming that CuO species has been reduced to Cu2O to some extent.

A strategy of eliminating phosphate inhibiting the degradation of metronidazole by hydroxylamine assisted heterogeneous Fenton-like system

The heterogeneous Fenton-like process using hydroxylamine (HA) possessed the merit of rapid oxidation performance is very fascinating for water treatment. However, the existence of phosphate limits the oxidation rate of organic pollutants. This study uncovered the role of phosphate in HA-assisted Fenton-like process and provided a feasible strategy to dispel the negative influence of phosphate upon introduction of aluminum and ferric ions. Besides, optimized reaction conditions as nMET of 0.04 g/L, H2O2 of 1.3 mM and HA of 0.4 mM were acquired by response surface methodology (RSM) with MNZ degradation efficiency of 95.21% and leaching Fe ions of 2.26 mg/L. Hydroxyl radical (HO) and superoxide radical (O2−) were responsible for MNZ removal. Subsequently, the toxicities assessment of formed MNZ byproducts was clarified based on the analysis of MNZ decomposition pathways.

Photocatalytic Activity of Zero-Valent Iron Nanoparticles Highly Dispersed on Porous Carbon Materials

During the traditional homogeneous Fenton reaction process for water treatment, the consumption rate constant of Fe2+ is much greater than its regeneration rate constant, which makes Fe2+ an almost stoichiometric loss and produces iron sludge waste. In this article, highly dispersed zero-valent Fe nanoparticles loaded on porous carbon materials (Fe-EMC) were synthesized by a one-step calcination method using Flammulina velutipes natural carbon source and Fe(NO3)3 as raw materials to solve the aforementioned problem. The as-prepared Fe-EMC materials are characterized by X-ray diffraction analysis, scanning electron microscopy, electron probe microanalyzer, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption–desorption measurements. It exhibits excellent photocatalytic activity for the degradation of methylene blue (MB) dyes under a broad pH region. Under conditions of 0.3 g/L Fe-EMC, 0.2 M/L H2O2, pH 7.0–11.0, and 50 mg/L MB, 97.98% of the MB dyes in the solution were completely degraded within 1 h. It was attributed to the efficient regeneration cycle between Fe2+ and Fe3+ in the Fenton-like system with light irradiation, which can promote the generation of active oxygen species.