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• The Fenton-like Cu-PAN 3 catalysts is first synthesized by co-precipitation and carbon thermal reduction method. • Dual reaction centers are constructed around graphene-like carbon and Cu species. • The pollutants as electron donors inhibit the ineffective decomposition of H 2 O 2 at the electron-poor centers. • The pollutant removal mainly relies on the surface cleavage at the electron-poor centers. High energy consumption has seriously hindered the development of Fenton-like reactions for the removal of refractory organic pollutants in water. To solve this problem, we designed a novel Fenton-like catalyst (Cu-PAN 3) by coprecipitation and carbon thermal reduction. The catalyst exhibits excellent Fenton-like catalytic activity and stability for the degradation of various pollutants with low H 2 O 2 consumption. The experimental results indicate that the dual reaction centers (DRCs) are composed of Cu-N-C and Cu-O-C bridges between copper and graphene-like carbon, which form electron-poor/rich centers on the catalyst surface. H 2 O 2 is mainly reduced at electron-rich Cu centers to free radicals for pollutant degradation. Meanwhile, pollutants can be oxidized by donating electrons to the electron-poor C centers of the catalyst, which inhibits the ineffective decomposition of H 2 O 2 at the electron-poor centers. This therefore significantly reduces the consumption of H 2 O 2 and reduces energy consumption. [Display omitted] [ABSTRACT FROM AUTHOR]

Environmentally friendly catalysts have come to the forefront due to the cost of chemically produced catalysts and the formation of by-products harmful to the environment. Millions of tons of plant waste are produced every year, some of which is disposed directly. In this study, tomato stem hydrochar (TSCH) was produced from waste tomato stems by the hydrothermal carbonisation (HTC) method, and its use as a catalyst was investigated. The optimisation of Cr(VI) removal from water was carried out using a Fenton-like process with a TSCH catalyst and resulted in 100% of Cr(VI) removal efficiency at 10 mg/L of Cr(VI) concentration, pH 2.00, 0.2 g/L of TSCH catalyst, 10 µL/L of H2O2 and 60 minutes of reaction time. Fenton-like thermodynamic and kinetic data were analyzed, and the results were found to comply with the second-order in Cr(VI) removal. The reusability of the TSCH catalyst in Cr(VI) removal was investigated and it was emphasized that it was reusable for more than 5 uses. In conclusion, TSCH, which is an environmentally friendly, inexpensive and effective catalyst for Cr(VI) treatment in a Fenton-like process, can be used as an alternative catalyst for wastewater treatment in terms of both waste management and economic and environmentally friendly. [ABSTRACT FROM AUTHOR]

The thorny problem of adsorption is the disposing of spent adsorbent. In this manuscript, the exhaust adsorbent of efficient capture Cu(II) over ZSM-5 that supported zero-valent iron (nZVI) was reused as a catalyst for eliminating Rhodamine B (RhB). Batch experiments were used to evaluate the removal performance of Cu2+ and RhB. The results demonstrated that the Cu2+ adsorption process obeyed pseudo-second-order kinetics, and the adsorption performance was dependent on solution pH. The maximum adsorption capacity at the optimal pH 4.0 was 375.9 mg/g; equilibrium was reached rapidly within 35 min. From XPS, the reduction-oxidation between Fe0 and Cu2+ was occurred in the adsorption process, and Fe2+, Fe3+, and Cu0 was formed. In the recycling experiments, RhB was removed by the spent Cu adsorbent, with the removal performance being dependent on the initial Cu concentration, in the order of 5 mg/L > 20 mg/L > 0 mg/L > 100 mg/L > 500 mg/L. RhB removal also improved with increasing H2O2 concentration. More than 99.9% of the RhB was degraded within 8 min using 1.75 mM H2O2, which was a large improvement over the previously used catalyst. The hydroxyl radical was found to be the main free radical responsible for RhB degradation. [ABSTRACT FROM AUTHOR]

[Display omitted] The mutual transformation of reactive oxygen species may affect the structural transformation of catalysts during the Fenton-like processes. Its in-depth understanding is essential to achieve high catalytic activity and stability. In this study, a novel design of Cu(I) active sites based on the metal–organic framework (MOF) is proposed to "capture" OH− produced via Fenton-like processes and re-coordinate the oxidized Cu sites. The Cu(I)-MOF presents an excellent removal efficiency for sulfamethoxazole (SMX), with a high removal kinetic constant of 7.146 min−1. Combing DFT calculations with experimental observations, we have revealed that the Cu of Cu(I)-MOF exhibits a lower d-band center, enabling efficient activation of H 2 O 2 and spontaneous "capturing" of OH− to form Cu-MOF, which can be reorganized into the Cu(I)-MOF through molecular regulation for recycle. This research demonstrates a promising Fenton-like approach for solving the trade-off between catalytic activity and stability and provides new insights into the design and synthesis of efficient MOF-based catalysts for water treatment. [ABSTRACT FROM AUTHOR]

Developing a highly efficient Fenton-like catalyst working in a wide pH range is imperative to accomplish its practical wastewater treatment. Herein, FeS2/FeSxOy catalyst was synthesized by hydrothermal-solvothermal vulcanization with thioacetamide as a sulfur source. Characterization results confirmed FeS2/FeSxOy consisted of pyrite, kornelite, and szomolnokite. FeS2/FeSxOy exhibited superior catalytic activity toward H2O2 activation with more than 96% phenol removal within 5 min in pH 3.0 ∼ 8.0 at 30°C. Radical scavenging experiment and EPR analysis revealed both hydroxyl radicals (·OH) and superoxide anion radicals (O2·-) anticipated in phenol elimination, but ·OH played a dominant role. The detailed degradation experiments and density functional theory (DFT) calculation confirmed the vital role of FeS2 in enhancing phenol abatement. This study not only developed a highly active catalyst for H2O2 activation but also theoretically analyzed the FeS2 function in depth, which provided a guide for designing a highly efficient Fenton-like catalyst. [ABSTRACT FROM AUTHOR]

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We designed a photocatalyst and developed sustainable wastewater purification technology, which have significant advantages in effectively solving the global problem of drinking water shortage. In this study, a new nanocomposite was reported and shown to be a catalyst with excellent performance; CuO was coated successively onto functionalized nano γ-Al2O3, and this novel structure could provide abundant active sites. We evaluated the performance of the CuO@γ-Al2O3 nanocomposite catalyst for polyvinyl alcohol (PVA) degradation under visible light irradiation. Under optimized conditions (calcination temperature, 450 °C; mass ratio of γ-Al2O3:Cu(NO3)2·3H2O, 1:15; pH value, 7; catalyst dosage, 2.6 g/L; reaction temperature, 20 °C; and H2O2 dosage, 0.2 g/mL), the CuO@γ-Al2O3 nanocomposite catalyst presented an excellent PVA removal rate of 99.21%. After ten consecutive degradation experiments, the catalyst could still maintain a PVA removal rate of 97.58%, thus demonstrating excellent reusability. This study provides an efficient and easy-to-prepare photocatalyst and proposes a mechanism for the synergistic effect of the photocatalytic reaction and the Fenton-like reaction. [ABSTRACT FROM AUTHOR]

In this work, using molasses wastewater as a partial acidifying agent and bagasse pith as a pore-enlarging agent, a new low-cost Fenton-like catalyst (ACRMbp) used for degradation of sulfamethoxazole was prepared through a simple process of acidification and calcination using red mud (RM) as the main material. The optimum preparation conditions of ACRMbp were acquired, and the optimum preparation conditions of ACRMbp were as follows: mass ratio of bagasse pith to RM (mbp:mRM) 0.033:1, particle size of bagasse pith 0.10–0.20 mm, calcination temperature 773 K, and calcination time 2 h. The ACRMbp catalyst was characterized by XRD, SEM, EDS, and BET. According to the results of characterizations, it was found that the iron phase of ACRMbp had completely transformed into α-Fe2O3 after the process of acidification and calcination, and the addition of bagasse pith significantly improved the surface area of the prepared ACRMbp. Furthermore, under the reaction conditions of catalyst dosage of 2 g/L, initial pH 3 and reaction time 90 min, the ACRMbp has showed the highest catalytic activity. ACRMbp had significantly higher activity than red mud, and exhibited a remarkable settleability. Besides, ACRMbp retained good recyclability and stability during use. Kinetic studies showed the degradation process could be described with the first-order model. Overall, the prepared ACRMbp was an effective and excellent catalyst in the Fenton-like process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Cu-Ni@SBC catalyst was prepared by doping Cu-Ni bimetal in SBC. • The Cu-Ni bimetallic catalyst had a significant activation effect on H 2 O 2. • The synergistic catalytic mechanism in Fenton-like reaction was proposed. • The feasibility of the catalyst to degrade coal chemical wastewater was verified. In this study, the sewage sludge was converted into sludge biochar (SBC) and doped with Cu-Ni bimetal to synthesize a novel composite catalyst (Cu-Ni@SBC) for the activation of H 2 O 2 for phenol degradation. Characterization results showed that the Cu-Ni bimetal was successfully doped into the SBC and led to the formation of a porous structure with abundant cavities, resulting in a larger specific surface area and higher adsorbed oxygen content. Mechanism analysis revealed a valence state conversion cycle between Cu0-Cu(II), Ni(III)-Ni(II) and Cu-Ni which made Cu-Ni@SBC have higher electron transfer performance. Response surface methodology was applied to determine the optimal preparation and reaction conditions, under which the Fenton-like system composed of Cu-Ni@SBC and H 2 O 2 removed 100 % of phenol and mineralized 69.1 % of TOC from simulated wastewater. In addition, the experimental results showed that the Cu-Ni@SBC material had a relatively wide pH adaptation range (4–8), and the removal efficiency of phenol could reach 76.4 % after 5 cycles of experiments, and the catalytic inhibition rates of the two common coexisting anions, HCO 3 – and Cl-, were 17.1 % and 0 %, respectively. The results of practical application revealed that the phenol removal efficiency reached 90.44 % and the pollutant mineralization rate could reach 58.5 % within 90 min, which proved that the catalyst was suitable for the advanced degradation of organic matter in coal chemical wastewater. Therefore, Cu-Ni@SBC can be considered as a promising Fenton-like catalyst, and the process method is also of some guiding significance for the treatment of coal chemical wastewater. [ABSTRACT FROM AUTHOR]

Landfill leachates are a mixture of high concentration organic and inorganic contaminants and need to be appropriately treated due to their toxicity and severe adverse effects on the environment. Here, we studied the treatment of landfill leachate through a heterogeneous Fenton-like oxidation process using a zirconia supported copper catalyst (Cu/ZrO2). Reaction conditions such as pH, amount of catalyst, oxidant dose, temperature, and reaction time were investigated and their effects on pollutant abatement discussed. AOS (average oxidation state) and COS (carbon oxidation state) parameters were used for the evaluation of the degree of oxidation of the process, obtaining some insight into the formation of oxidized intermediates (partial oxidation) and the total oxidation (mineralization) of the leachate during the reaction. A two-step oxidation process enhanced the overall performance of the reaction with an abatement of organic compounds of 92% confirming the promising activity of a copper-based catalyst for the treatment of liquid waste. Higher catalytic activity was achieved when the following reaction conditions were applied: 70 °C, pH 5, 200 mg/L of catalyst, 30 mL/L of H2O2 dose, and 150 min. In addition, durability of the catalyst under optimized reaction conditions was verified by repeated reaction cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] The heterogeneous Fenton process suffers from low efficiency because of the low electron transfer cycle rate of Fe3+/Fe2+, which often consumes enormous amounts of hydrogen peroxide (H 2 O 2) or other energy. Herein, we report a novel Co-based Fenton-like catalyst (in-situ -Co-g-C 3 N 4) synthesized via the surface complexation method, in which Co species were modified in situ into the framework of the graphitic carbon nitride (g-C 3 N 4) substrate through C–O–Co chemical bonding. The catalyst exhibited higher Fenton-like catalytic activity than pure g-C 3 N 4 in the degradation of various pollutants under neutral conditions, as evidenced by the approximately 150-fold higher Fenton-like reaction rate constant of in-situ -Co-g-C 3 N 4 than that of g-C 3 N 4. Density functional theory (DFT) calculations and a series of experimental and characterization analyses revealed the interfacial reaction mechanism between H 2 O 2 , pollutants and in-situ -Co-g-C 3 N 4. During the Fenton-like reaction, the electron-poor C center on the aromatic ring of g-C 3 N 4 could capture the electrons deprived from pollutants, and subsequently deliver them to around the electron-rich Co center to efficiently reduce H 2 O 2 to hydroxyl radicals (•OH), enabling H 2 O 2 to be used efficiently for the degradation of pollutants. This study provides a strategy for improving Fenton-like degradation efficiency by effectively utilizing the energy of organic pollutants. [ABSTRACT FROM AUTHOR]

• The pre-coagulated landfill leachate concentrate was treated by Fenton-like process. • Process parameters were optimized by BBD of RSM. • The •OH radical proved to be the main active species. • The Fenton-like system produced more •OH at pH of 4. • The stability of the Fenton-like process under different pH was explored. The heterogeneous Fenton-like process with bimetallic chelated magnetic chitosan aerogel (Cu-Fe@CTS) as catalyst was applied to treat pre-coagulated leachate nanofiltration concentrate. The process conditions were optimized by Box-Behnken Design (BBD) and the maximum UV 254 removal reached 96.06% under the conditions of temperature 87.62 °C, oxidant dosage 0.2395 mol/L and catalyst dosage 1 g/L. The TOC concentration was reduced from 847.5 to 99.7 mg/L and COD concentration was reduced from 1625 to 464 mg/L. The three-dimensional (3D) fluorescence analysis showed that most of Fulvic acid-like (FA-like) was removed. The adsorption experiment showed that the catalyst reached the adsorption balanced after 60 min and the corresponding FA adsorption removal reached 14.1%. The addition of Tert-butanol (TBA) reduced the FA removal by 59.4%, indicating that the hydroxyl radicals (OH) was the main active species. Experiments of the OH capture at different pH showed that the Fenton-like system produced more OH at pH of 4, at which the maximum FA removal was 96.61%, while the FA removal still reached 94.26% at pH of 7. The OH capture at different temperature showed that the Fenton-like system produced more OH at 90 °C. KI and TBA shielding experiments showed that OH was produced on the catalyst surface rather than being produced by catalysis of free metal ions in the solution. [ABSTRACT FROM AUTHOR]

A comparison of the catalytic activity of the copper-modified magnetite was carried out under different conditions (dark and irradiated) and irradiation systems (460 nm Vis-LED, 370 nm UV-LED and Solar) in the degradation of the antibiotic sulfathiazole (STZ). The catalyst copper-modified magnetite presented a mesoporous structure, with a high absorption range (200–800 nm), band gap of 1.80 eV characteristic of iron and copper oxides, negative surface charge (− 24.6 mV) at neutral pH and high stability in solution (absence of iron and copper leaching). The results showed that the degradation kinetics of STZ increased in the following order in relation to irradiation: dark < Vis-LED < UV-LED < Solar), promoting complete degradation after 15 min, indicating that under solar and UV irradiation the catalytic activity is improved, due to an increase in the speed of the Fe–Cu redox reactions from a quick transfer of electrons that occur on the surface of the catalyst, further facilitating the formation of HO· radicals. The results have further demonstrated that the copper-modified magnetite can promote heterogeneous Fenton processes under LED or solar irradiation and be applied to effective degradation of micropollutants in wastewaters and have proven the versatility and high catalytic activity. [ABSTRACT FROM AUTHOR]

Tetracycline (TC), as a typical micro-pollutant in natural environment, has attracted much attention. The peroxymonosulfate (PMS)-based advanced oxidation process is regarded as a promising technology for TC treatment, while its potential practical application is mainly dependent on the oxidant yield derived from activating PMS by catalysts. Therefore, the development of improved activators which are characterized by adequate activity and stability for PMS decomposition is in high demand. In this paper, the high-efficiency K2−xMn8O16 nanowire hydrogels (KNH) with high stability was synthesized through a simple hydrothermal method and then an enhanced PMS/KNH system for antibiotic degradation via multiple strategies was established. For removal of low-concentration TC, a high degradation of nearly 95% could be achieved by activating PMS in a wide pH rang. More than that, a further catalytic mechanism of this PMS/KNH system was also put forward, thus providing a guideline for designing and fabricating transition-metal catalysts to activate PMS. [ABSTRACT FROM AUTHOR]

The discharge of colorless and water-soluble formaldehyde (FA) wastewater poses a serious threat to human health. In this study, copper based Fenton-like catalyst Cu x S y was innovatively introduced into the FA degradation system. Cu x S y catalysts with different morphologies were regulated by ethylenediamine. The Cu 7 S 4 catalyst exhibited 99% degradation performance towards FA. The physical and chemical properties of catalysts indicate that the Cu 7 S 4 catalyst has a beautiful dendritic snowflake like structure, which is more conducive to the adsorption and degradation process of FA. Electron paramagnetic resonance (EPR) detected an obvious Cu defect (g=2.064) in Cu 7 S 4 , which can effectively activate H 2 O 2 and stimulate the generation of •OH, thus accelerating the degradation of FA. Compared with Fenton reagent, Cu 7 S 4 shows more than 75% FA degradation performance (pH=5 and pH=9). Further research showed that the H 2 O 2 :Cu 7 S 4 ratio of 2:10 showed a 95% degradation effect on FA at 200–1000 ppm, demonstrating a more efficient and stable FA degradation ability. Moreover, the mechanism of FA degradation was analyzed. [Display omitted] • Recyclable Cu 7 S 4 catalyst with high Cu defects is used to degrade formaldehyde. • 1000 ppm formaldehyde wastewater can be degraded 85% within 30 minutes by Cu 7 S 4. • Cu 7 S 4 has high degradability and mineralization efficiency for formaldehyde. [ABSTRACT FROM AUTHOR]

Although CuFe 2 O 4 has been widely used in the field of Fenton-like wastewater treatment, its ability to activate H 2 O 2 still needs to be further improved. In this context, a novel Ag x /CFO OVs (x represents the theoretical mass percentage of Ag) composite catalyst was prepared by the tartaric acid reduction method for the first time, and its degradation performance and degradation mechanism of Phenol in a H 2 O 2 -based Fenton-like system were investigated. Through a series of characterizations, the successful preparation of the catalyst was confirmed. The degradation experiment showed that the degradation rate of 50 mg/L Phenol by Ag 2 /CFO OVs /H 2 O 2 system was 98.55% within 15 min, which was a significant improvement in the degradation efficiency compared with that of CuFe 2 O 4 and CFO OVs. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) confirmed the successful introduction of oxygen vacancies (OVs). Electrochemical impedance spectroscopy (EIS) showed that Ag 2 /CFO OVs had the lowest impedance, and the synergistic effect of OVs and Ag effectively enhanced the degradation capability of the catalysts for Phenol. The capture experiments of active species and ESR tests showed that the main active species of the Ag 2 /CFO OVs /H 2 O 2 system were 1O 2 and •OH. This study provides a new reference for the introduction of OVs and Ag in Fenton-like catalysts and their application to wastewater treatment. [Display omitted] • A novel Ag x /CFO OVs composite catalyst was prepared by the tartaric acid reduction method for the first time. • The catalyst exhibited excellent degradation of Phenol in H 2 O 2 -based Fenton-like systems. • The introduction of oxygen vacancies and Ag significantly enhanced the degradation performance of the catalyst. • The Ag x /CFO OVs /H 2 O 2 reaction system enables efficient mineralization of Phenol. • The catalyst showed good stability and recyclability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn SAC/PMS was designed to trigger radical and nonradical hybrid system. • The removal of target pollutant was dependent on the nonradical–oxidation. • A novel generation pathway of singlet oxygen under acidic and neutral conditions was explored. • A new mechanism for the synergistic effect of radical and nonradical pathways was proposed. The function of heterogeneous catalyst in singlet oxygen (1O 2) generation under acidic and neutral conditions and the effect of sulfate radical on the generation of 1O 2 is still unclear. This study provided a novel generation pathway of 1O 2 in the heterogeneous Mn single − atom catalyst (Mn SAC)/peroxymonosulfate (PMS) system. The MnN4 site with the ideal binding strength promoted the activation of PMS to generate sulfate radical (SO 4 •–), which would be adsorbed on the carbon/nitrogen sites forming SO 4 •– (s) , reacting spontaneously to produce 1O 2. The presence of MnN4 and carbon/nitrogen structure sites could shift the oxidation process from a bulk–phase oxidation to a surface oxidation. This shift has important implications in terms of reaction rate and product distribution, as the dual reaction sites decrease the required migration distance for the active species to form 1O 2 , avoiding the pointless consumption of active substances. [ABSTRACT FROM AUTHOR]

• Fenton-like AOP with Cu-Mn porous silica supported photocatalysts was performed Catalysts were evaluated at neutral pH for methylene blue model dye degradation • Adsorption of model dye on photocatalysts strongly depends on Mn. • Cu addition reduces Mn leaching from the silica support. • Mn and Cu act as separate active sites. Fenton and Fenton-like Advanced Oxidation Processes (AOP) have obtained large applicative use for the removal of organic pollutants from wastewater. Herein, we discuss a novel bimetal Cu-Mn porous silica-supported Fenton-like AOP catalyst with interparticle mesoporosity working under neutral pH and UV-VIS irradiation (CuMnKIL with Mn/Si = 0.01, Mn/Cu = 0.06). The photocatalyst was prepared via solvothermal synthesis (Mn incorporation into porous silica support) followed by incipient wetness impregnation (Cu loading into Mn containing porous silica support) and was tested for the decomposition of methylene blue as a model dye. Copper addition significantly reduced Mn leaching from the porous silica support (from 60 to 30 %) and functioned also as additional surface adsorption site. CuMnKIL (Mn/Si = 0.01, Mn/Cu = 0.06) showed 20 % higher adsorption and 20 % lower efficiency if compared with MnKIL (Mn/Si = 0.01) in Fenton-like AOP system, however, addition of irradiation (photo-Fenton-like system) improved efficiency of Cu/MnKIL (Mn/Si = 0.01, Mn/Cu = 0.06) for 10 % if compared to MnKIL (Mn/Si=0.01) due to the additional •OH radicals produced by the decomposition of H 2 O 2 by the light. No synergistic effects between Cu and Mn were recorded, meaning that Cu and Mn sites were acting as separate sites, which was confirmed with AR-TEM imaging as well as UV spectroscopy studies. [ABSTRACT FROM AUTHOR]

• Fe/SiO 2 performs well in the adsorption of methylene blue. • Fe/SiO 2 and H 2 O 2 form a heterogeneous Fenton-like system. • Methylene blue is degraded to colorless water-soluble organics. Silica (SiO 2) and iron-incorporated silica (Fe/SiO 2) materials are prepared from rice husk pyrolytic residues through alkali treatment, co-precipitation and calcination. The prepared material is characterized by ICP-AES, XRD, FT-IR, UV–vis DRS, XPS, SEM-EDS and TEM, and the results indicate that the prepared materials are mesoporous, where framework and extra-framework iron species concurrently exist in the Fe/SiO 2. The prepared materials are applied to treat methylene blue (MB) solution, where influencing factors such as temperature, pH, the dosage of H 2 O 2 and Fe/SiO 2 are studied. Under the optimal conditions, Fe/SiO 2 shows a much better adsorption effect than SiO 2 , where Fe/SiO 2 can adsorb 85% of MB within only 2 min, and almost 98.8% color is removed within 90 min in the presence of both Fe/SiO 2 and H 2 O 2. Only 0.46% iron leaches from Fe/SiO 2 , and it performs relatively good results in the recycle utilization where almost 90% of chroma is removed within 10 min or 20 min. Hydroxyl radicals are successfully captured by electron paramagnetic resonance (EPR) experiment and it proves that a heterogeneous Fenton-like system form in the presence of both Fe/SiO 2 and H 2 O 2 , i.e., Fe/SiO 2 acts as both adsorbent and catalyst in the treatment process of MB. [ABSTRACT FROM AUTHOR]

Heterogeneous Fe-based Fenton-like reaction is an efficient technology in wastewater treatment. However, few studies reveal the effects of exposed facets and surface OH groups of iron oxides on its reactivity. In this study, two lepidocrocite samples with lath- and rod-like morphologies were synthesized and applied to the adsorption and degradation of Orange G (OG). The OG molecule could be adsorbed vertically on the lath-like sample by the interaction with the μ−OH groups of the (010) facet. The molecule could also be adsorbed laterally on the rod-like sample by the interactions with the μ−OH and μ 3 −OH groups of the (010) and (001) facets. When the data were normalized to the unit surface area, the adsorption capacity of OG, the production efficiency of OH, the degradation rate in dark, and the total degradation rates under visible light irradiation in the lath-like system were 9.625-, 3.34-, 2.75-, and 1.98-fold higher than those in the rod-like system, respectively. • Two γ-FeOOH samples with lath- and rod-like shapes were prepared. • Lath-like γ-FeOOH exhibited a high percentage of (010) facets and μ−OH groups. • μ−OH groups of γ-FeOOH exhibited large adsorption capacity and affinity for OG. • μ−OH groups of γ-FeOOH exhibited high production efficiency of OH. [ABSTRACT FROM AUTHOR]

FeNiCeOx was firstly prepared by ultrasonic impregnation method and used to remove diclofenac in a Fenton-like system. The catalytic activity was improved successfully by doping Ni into FeCeOx. The diclofenac removal efficiency reached 97.9% after 30 min reaction. The surface morphology and properties of FeNiCeOx were characterized by Brunauer--Emmett--Teller (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Raman and X-ray photoelectron spectroscopy (XPS) analyses. FeNiCeOx in this paper had larger specific surface area than those prepared by other methods, which was attributed to the cavitation effect and hot-spot effect during the ultrasonic synthesis process. Low crystallinity of Fe2O3 and NiO showed by characterization could lead to high interaction of Fe and Ni ions with support of CeO2. They substituted Ce in CeO2, caused lattice contraction and formed more oxygen vacancies, which favoured the catalytic reaction. Meanwhile, Fe and Ce ions both had redox cycles of Fe3+/Fe2+ and Ce4+/Ce3+, which facilitated the electron transfer in the reaction. The synergistic effect among Fe, Ni and Ce might lead to better catalytic performance of FeNiCeOx than any binary metal oxides constituted from the above three elements. Finally, the potential mechanism of diclofenac removal in FeNiCeOx-H2O2 system is proposed. [ABSTRACT FROM AUTHOR]

Abstract Phosphate residue is regarded as a hazardous waste, which could potentially create significant environmental and health problems if it is not properly treated and disposed of. In this study, nitrogen-doped carbon nanotubes-FePO 4 (NCNTs-FePO 4) composite was successfully synthesized from phosphate residue, and its application as an effective catalyst was explored. Firstly, an effective method was developed to recover FePO 4 from phosphate residue, achieving an impressive FePO 4 mass recovery rate of 98.14%. Then, the NCNTs-FePO 4 catalyst was synthesized from the recovered FePO 4 by two main reactions, including surface modification and chemical vapor deposition. Finally, the synthesized NCNTs-FePO 4 was applied to photo-degrade 15 mg/L Rhodamine B (RhB) in a Fenton-like system. The results showed that 98.9% of RhB could be degraded in 60 min, closely following the pseudo-first-order kinetics model. It was found that even after six consecutive cycles, NCNTs-FePO 4 still retained a high catalytic capacity (> 50%). Moreover, •OH radicals participating in the RhB degradation process were evidenced using quenching experiments and electron paramagnetic resonance analysis, and a rational mechanism was proposed. It was demonstrated that the materials synthesized from hazardous phosphate residue can be used as an effective catalyst for dye removal. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract In this study, a multi-component catalyst, β-cyclodextrin (β-CD) and reduced graphene oxide (rGO) co-modified Fe 3 O 4 , was fabricated via one-pot solvothermal method and used as a synergistic catalyzer for Bisphenol A (BPA) removal. The study found that catalytic reactions of BPA followed the pseudo-first-order kinetics model, and the correlation rate constants (k obs) were calculated. Compared with Fe 3 O 4 @β-CD (0.02173 min−1), Fe 3 O 4 /rGO (0.09735 min−1) and Fe 3 O 4 (0.01666 min−1), the composite (0.15733 min−1) exhibited stronger catalytic ability to remove BPA from aqueous solution under the same conditions, which were attributed to the synergistic enhancement effect among the components. The introduction of rGO in the composites was beneficial to the generation of •OH, and the role of β-CD might enhance the utilization of •OH. A possible three-element catalytic schematic diagram was described. The effects of pH, dosage of the catalyst, initial H 2 O 2 and NH 2 OH concentrations on the removal efficiency were further investigated. The removal of BPA and TOC retained 78.2 ± 2.4% and 52.9 ± 2.5% after five cycles, indicating its excellent stability and reusability. Furthermore, a probable reaction pathway of BPA removal was suggested by analyzing the intermediate products. All results indicated that the composite had high and stable catalytic performance, which made it have potential application on the industrial treatment of wastewater. Graphical abstract Image 1 Highlights • Fe 3 O 4 @β-CD/rGO composite were firstly synthesized by One-pot solvothermal method. • Fe 3 O 4 @β-CD/rGO with k obs of 0.15733 min−1 for BPA exhibited strong catalytic ability. • The synergistic effect of composite catalyst in degradation of BPA was confirmed. • The catalysts showed excellent activity and reusability (about 80% after 5 cycles). These findings provide further insights into the assessment of multi-component catalyst for endocrine disruptors elimination. [ABSTRACT FROM AUTHOR]

A novel catalyst system was investigated based on Fe- N , N ʹ-dipicolinamide complex for the degradation of 4-chlorophenol (4-CP) by using hydrogen peroxide as an oxidant under mild alkaline conditions. This complex was stabilized by a ligand that assembles pyridyl and amide groups with a suitable linker. The optimization of the synthesized catalysts was evaluated in terms of the removal efficiency of 4-CP, by using Fe(II) and N , N ʹ-1,2-phenyl-enedipyridine-2-carboxamide with a molar ratio of 1:1. The effects of reaction parameters on the oxidation of 4-CP were investigated by applying the selected catalyst with 4-CP removal rate of 99%. The results indicated that the pH and catalyst concentration could significantly affect the degradation rate of 4-CP. The mineralization level of 4-CP during the reaction was also examined, and almost 62.5% of 4-CP was absolutely mineralized into carbon dioxide and water. The preliminary analysis on the degradation mechanism indicate that the main active species are not hydroxyl radicals, and another kind of active species, called iron-oxo species, were proposed. This study explores a resultful linker between pyridyl and amide and presents a new method to expand the application of pH range of Fenton-like system. [ABSTRACT FROM AUTHOR]

In this research, the ability of Fenton-like catalytic process in the presence of H2O2 for degradation of humic acid in simulated water was studied. In this regard, FeNi3 nanoparticles were synthesized by the coprecipitation method, using SiO2. The properties of the prepared FeNi3@SiO2 were assessed using Fourier transform infrared spectroscopy, vibrating sample magnetometer, field-emission scanning electron microscopy and transmission electron microscopy. The studied parameters were pH (3, 5, 7, 9 and 11), contact time (5–180 min), nanocomposite dose (0.005–0.1 g/L), concentration of humic acid (2–15 mg/L) and concentration of H2O2 (50–200 mg/L). The highest removal percentage of humic acid was 100% at pH = 7, with humic acid concentration of 10 PPM, FeNi3@SiO2 dosage of 0.1 g/L and H2O2 dosage of 200 mg/L. According to the results, the Fenton-like catalytic process of FeNi3@SiO2/H2O2 had high efficiency in removing humic acid from aquatic environment. [ABSTRACT FROM AUTHOR]

The efficiency of Fenton and Fenton-like processes can be seriously affected by the continuous loss of iron ions and by the formation of solid sludge. Here, alginate (Alg) films were synthesized to stabilize iron ions (Fe 2+ and Fe 3+ ) and to enhance their catalytic activities towards the decolorization of methyl orange via heterogeneous Fenton and Fenton-like processes. Iron ions were ionically bond to the Alg molecules resulting in a three-dimensional network with specific structural and morphological features according to the valence states of iron. Our results demonstrated that both Alg-Fe 2+ and Alg-Fe 3+ films show highlighted catalytic activity for the decolorization of MO and high decolorization rates. Reuse experiments demonstrated that both films could be employed in at least five consecutive decolorization processes without losing their catalytic efficiency or stability. Taken together, our findings reveal that the Alg-Fe 2+ and Alg-Fe 3+ films may be suitable low-cost catalysts in heterogeneous Fenton and Fenton-like processes. [ABSTRACT FROM AUTHOR]

Incorporating Mo into Fe-catalyst can enhance the catalytic activity and application range of pH value of catalyst. Therefore, Mo-Fe compounds with different Mo:Fe molar ratios were prepared by a wet chemical process, and then were used to degrade tetracycline (TC) by initiating a heterogeneous Fenton-like system with H2O2. The results demonstrated that the Fe2(MoO4)3/H2O2 system most efficiently degraded TC. At an initial concentration of 50 mg/L TC with natural pH value (about 5.5), about 99% of TC could be removed within 30 min by 0.8 g/L Fe2(MoO4)3 and 17.6 mM H2O2 at 299.15 K. Moreover, the pH value did not affect TC removal rate; but changed the total organic carbon removal rate. The Fe leaching concentration was about 0.009 mg/L under the optimal conditions. The TC removal rates in the Fe2(MoO4)3/H2O2 system were influenced by the complexity level of practical wastewater. The scavenging experiment using several scavengers indicated that both hydroxyl radicals (in solution and catalyst surface) and superoxide radicals played important roles in the degradation of TC. A possible degradation mechanism and pathway for TC were proposed in the Fe2(MoO4)3/H2O2 system. Finally, a comparison was made between this study and some others, showing that Fe2(MoO4)3/H2O2 was a preponderant system for TC removal. [ABSTRACT FROM AUTHOR]

This study investigates the removal of total petroleum hydrocarbons (TPH) from Mahshahr contaminated soil by Fenton-like oxidation. Magnetite nanoparticle (MNP) was applied as catalyst in the oxidation process to improve the hydroxyl radicals (OH°) production and, consequently, the removal of TPH from the samples. Response surface methodology with center composite design (CCD) was used to optimize performance of the treatment process. Various molar ratios of HO-MNP were calculated by CCD and then added to the contaminated samples at acidic pH (pH 3) and under laboratory conditions. The quadratic model describing TPH removal efficiency of Fenton-like was developed and validated by analysis of variances (ANOVA), correspondingly. The analysis results illustrated that the optimum condition of treatment was obtained using HO:MNP molar ratio of 17.5:1, leading to removal of 74.20% of TPH from the contaminated soil slurries. According to the results, the use of MNP catalyst and optimal molar ratio of HO-MNP had dominant roles in the increased oxidation of TPH from the slurries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe-SAC exhibited a higher catalytic activity than that of Cu-SAC. • High-valent iron-oxo species dominated the organics oxidation in Fe-SAC/PMS system. • Different spin-state of metal sites was responsible for versatile pathways via PMS activation. • The SACs-catalytic filter showed stable catalytic performance for versatile organics. Herein, we prepared two kinds of single-atom catalysts (SACs) with uniformed coordination structures (M−N 4 , M = Fe, and Cu) for evaluating the versatile pathways of peroxymonosulfate (PMS) activation by different metal sites. Fe-SAC exhibited a higher catalytic performance than that of Cu-SAC for chloroquine phosphate (CQP) oxidation. Results showed that the high-valent iron-oxo species accounted for 74.5 % for CQP oxidation in Fe-SAC/PMS system, while radicals (SO 4 •– and HO•) dominated the CQP oxidation (58.3 %) in Cu-SAC/PMS system, which was associated to the different spin-state of the metal sites for PMS adsorption and breakage of O O in PMS as well as the intermediates in versatile pathways. The SACs were then fixed onto the catalytic filter for PMS activation, which showed stable and effective catalytic performance for versatile recalcitrant organics. Overall, this work not only provided the atomic-level knowledge on PMS activation, but also gave the potential applications of Fenton-like for water remediation. [ABSTRACT FROM AUTHOR]

Recently, Fenton-like reaction based on peroxymonosulfate (PMS) has been recognized as a potential alternative for the degradation of organic pollutants. Herein, a high-efficiency and stable catalyst comprised of single Ru atoms dispersed on N-doped carbon (Ru SA -N-C) is synthesized by solvothermal strategy. Ru SA -N-C could effectively activate PMS for the degradation of azide dyes (Orange Ⅱ), compared with Ru-nanoparticle-loaded catalysts. Free radical scavenging experiments and density functional theory have displayed that singlet oxygen (1O 2) produced by Ru-N 4 sites are the main reactive oxygen species for the degradation of Orange Ⅱ. Meanwhile, the adjacent pyridinic N acts as the adsorption sites to anchor Orange Ⅱ. The ultra-high catalytic activity of Ru SA -N-C mainly derivate from its distinctive dual reaction sites, which significantly shorten the migration distance from 1O 2 to the adsorbed Orange Ⅱ molecules. This study provides a potential Ru SA -N-C/PMS system for the high-efficiency sewage treatment. [Display omitted] • Single-atom Ru dispersed on N-doped carbon was synthesized by solvothermal strategy. • 1O 2 was the dominant specie in the Ru SA -N-C/PMS system. • The ultra-high catalytic activity of Ru SA -N-C mainly derivate from its distinctive dual reaction sites. • Experimental and DFT calculation results demonstrate RuN 4 site was optimum active site. • The degradation pathway of Orange II was fully validated by the Fukui index, LC-MS and TOC. [ABSTRACT FROM AUTHOR]

Magnetic metal M (M = Fe, Co, Ni) nanocrystals encapsulated in nitrogen-doped carbon nanotubes (M@N-C) were fabricated conveniently using dicyandiamide as a C/N precursor, and exhibited varying activities toward Fenton-like reaction. The surface morphology and structure of the M@N-C catalysts were characterized and an efficient catalytic degradation performance, high stability, and excellent reusability were observed. In addition, several operational factors, such as initial dye concentration, oxidant type (peroxymonosulfate, peroxydisulfate and H 2 O 2 ) and dosage, reaction temperature, and dye type as well as stability of the composite were extensively evaluated in view of the practical applications. The results showed that various transition metals M significantly affected the structures and performances of the catalysts, and specially, their activity followed the order of Co > Fe > Ni in the presence of peroxymonosulfate. Moreover, H O ⁡ and S O 4 − radicals participating in the process were evidenced using quenching experiments, and a rational mechanism was proposed based on a non-radical process and the free radical process. Control experiments revealed that the enhanced active sites were mainly ascribed to the synergistic effects between the metal nanocrystals and nitrogen-doped carbon. The findings of this study elucidated that encapsulation of nanocrystals in nitrogen-doped carbon nanotubes was an effective strategy to enhance the overall catalytic activity. [ABSTRACT FROM AUTHOR]

The efficiency of a microwave-assisted Fenton-like process using special supported catalysts was evaluated using total organic carbon (TOC) removal from pharmaceutical wastewater. No acidification was required. The highest level of TOC removal efficiency from wastewater achieved was 65.88%. Moreover, the maximum number of consecutive uses with high activity was four. Under optimal conditions, the influent value of BOD5/COD was 0.25, and the effluent value of BOD5/COD was elevated to 0.40. In addition, colour was completely removed. This efficiency was compared with the same MW-Fentonlike process using common supported catalysts, where the highest achieved TOC removal efficiency from wastewater was 39.25%, the colour of the wastewater decreased from 50 to 20, and the value of BOD5/ COD was elevated from 0.25 to 0.34. The maximum number of consecutive high activity uses was two. This advanced performance was attributed to no presence of copper carbonate or cerium carbonate on the surface of special supported catalysts. The preparation method for these catalysts combined the merits of the isometric impregnation method with some new improvements. Its advantages include high-efficiency performance, short preparation time, low reagent usage (cupric nitrate 3.6 g, cerium nitrate 1.2 g, ammonia 1 mL), and reusability. The properties of the catalyst with the most efficient performance were characterized by determining surface particle size, the relative amount of active components and promoters, and the stable crystal form of the active components. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of Mn x Co 1−x Se catalysts were synthesized via hydrothermal process. • Mn 0.5 Co 0.5 Se possessed excellent catalytic activity and reusability. • 1O 2 , •OH, and •O 2 – were the dominant ROS in Mn 0.5 Co 0.5 Se/H 2 O 2 system. • Ternary element cycling and selenium vacancies contributed to high activity. • Se-based Mn-Co bimetals were promising Fenton-like catalysts. In this study, the Mn x Co 1−x Se catalysts were synthesized and employed in Fenton-like reactions for the degradation of organic pollutants. The Mn 0.5 Co 0.5 Se composite with 1:1 dosing ratio (Mn:Co) represented the best catalytic performance and showed higher reusability and stability in five cycles. The optimum conditions for target pollutant removal were 0.1 g/L catalyst dosage, 2.6 mM H 2 O 2 concentration, and initial pH 7.0 according to the result of a response surface approach. The high catalytic efficiency of the Mn x Co 1−x Se catalyst was attributed to the high-performance cycle of Mn/Co/Se elements between their oxidic and reduced states. Both non-radical processes (based on 1O 2) and radical processes (based on •OH and •O 2 –) were verified to be involved in the degradation of Acid Orange 7 (AO7). Se vacancy on the Mn x Co 1−x Se surfaces was identified and it played a significant way in the generation of non-radical 1O 2. The AO7 degradation intermediates and toxicity analysis were also evaluated. This study provides new insights on the Se-based bimetal redox cycle in the Fenton-like process, promoting its application in organic pollutants degradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of three-metallic catalyst with porous structure. • Synergic effect between the transition metals led to high catalytic activity. • Methylene blue was degraded through ultrasound-assisted Fenton-like reactions. • 98% of methylene blue was degraded in just 30 min. Successful catalytic degradation of pollutant molecules in wastewater streams has received tremendous attention in the last decade. Herein, we report the synthesis and characterization of a Fenton-like catalyst nanocomposite including CoFe 2 O 4 magnetic nanoparticles, porous silica and Cu-metal–organic framework (Cu-MOF) via a multi-step self-assembly method. For this purpose, CoFe 2 O 4 /SiO 2 magnetic nanostructure was synthesized by sol–gel method and then functionalized by glutaric anhydride and 3-(triethoxysilyl)propylamine. Subsequently, a nanoporous Cu-MOF framework was grown on the surface of nanoparticles to gain CoFe 2 O 4 /SiO 2 /Cu-MOF nanostructure. This unique nanocomposite offers various functional sites for the successful catalytic treatment of wastewater, confirmed by different analytical characterization techniques. The as-designed nanocomposite catalyst showed a porous structure with 27 g/m2 surface area. The as-synthesized nanocomposite was used to degrade methylene blue in its aqueous solution as a model wastewater sample through a sono-Fenton-like reaction approach. The results showed that almost all (∼98%) of the methylene blue molecules were degraded in the model wastewater sample an hour. Additionally, we analyzed the catalytic kinetic data by several mathematical models. The analysis revealed that the catalytic process follows a pseudo-second-order kinetic model, indicating that the removal of dye took place dominantly through the multi-site interactions, thanks to different active sites on the surface of the as-synthesized nanocomposite. This study shows that the proposed nanoporous magnetic MOF nanostructure has a great potential to be used as a catalyst for environmental applications. [ABSTRACT FROM AUTHOR]

Abstract: Granular activated carbon (GAC) can remove trace organic pollutants and natural organic matter (NOM) from industrial and municipal waters. This paper evaluates an iron nanocatalyst approach, based on Fenton-like oxidation reactions, to regenerate spent GAC within a packed bed configuration after saturation by organic compounds. Specifically, we focus on regenerating GAC packed beds equilibrated with varying influent concentrations of phenol, a model organic compound. Iron nanocatalysts were synthesized using ferric chloride, a chemical already used as a coagulant at municipal WTPs, and reacted with hydrogen peroxide (H2O2) for the purpose of in-situ regeneration. Up to 95% of phenol adsorption capacity was regenerated for GAC equilibrated with 1000 mg/L of phenol. Using this technique, at least four adsorption–regeneration cycles can be performed sequentially for the same batch of GAC with fresh iron nanocatalysts while achieving a regeneration efficiency of 90 ± 5% between each loading. Moreover, the iron nanocatalyst can be recovered and reused multiple times. Lower initial adsorbate concentrations (10–500 mg/L) resulted in a slightly lower saturated adsorbent-phase concentration of phenol and lower regeneration efficiencies (72 ± 5%). Additionally, this catalytic in-situ regeneration was applied to GAC saturated by NOM. A slightly lower regeneration efficiency (60%) was observed for the Suwannee River NOM adsorption capacity of GAC. The next step is validation in a pilot-scale test that applies this regeneration technique to a GAC adsorber employed in NOM removal. [Copyright &y& Elsevier]

The article examines the Fenton-like oxidation and mineralization of phenol through the synthetic Fe(II)-Fe(III) green rusts as pollutants. Study demonstrates that green rusts has different reactivity toward phenol oxidation. This suggests that the oxidation reaction promoted by green rust may contribute to the transformation of the water contaminants in the presence of hydrogen peroxide (H 2 O 2 ).

Abstract: The oxidation of pentachlorophenol (PCP) on the surface of magnetite used as heterogeneous catalyst has been investigated under various experimental conditions (initial substrate concentration, H2O2 dose, solid loading and temperature) at neutral pH and correlated with the adsorption behavior. The surface reactivity of magnetite was evaluated by conducting the kinetic study of both H2O2 decomposition and PCP oxidation experiments. The occurrence of the optimum values of H2O2 and magnetite concentrations for the effective degradation of PCP could be explained by the scavenging reactions with H2O2 or iron oxide surface. The surface interactions with PCP in the absence and the presence of oxidant can be well described by Langmuir and Langmuir–Hinshelwood models, respectively. All batch experiments indicate that Fenton-like oxidation of PCP was controlled by surface mechanism reaction and the species compete with each other for adsorption on a fixed number of surface active sites. The apparent degradation rate was dominated by the rate of intrinsic chemical reactions on the oxide surface rather than the rate of mass transfer. Raman analysis suggested that the sorbed PCP was removed form magnetite surface at the first stage of oxidation reaction. The mineralization determined by TOC abatement was completed after 7 d, while total dechlorination was achieved at 4 d treatment time. The first reaction of PCP oxidation should be the dechlorination since 90% of chloride was formed at the first 30h corresponding to the total disappearance of parent compound. All X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Mössbauer spectroscopy and chemical analyses showed that the magnetite catalyst exhibited low iron leaching, good structural stability and no loss of performance in second reaction cycle. [Copyright &y& Elsevier]

The catalytic efficiency of iron (II, III) oxide to promote Fenton-like reaction was examined by employing Rhodamine B (RhB) as a model compound at neutral pH. Two types of iron (II, III) oxides were used as heterogeneous catalysts and characterized by XRD, Mössbauer spectroscopy, BET surface area, particle size and chemical analyses. The adsorption to the catalyst changed significantly with the pH value and the sorption isotherm was fitted using the Langmuir model for both solids. Both sorption and FTIR results indicated that surface complexation reaction may take place in the system. The variation of oxidation efficiency against H2O2 dosage and amount of exposed surface area per unit volume was evaluated and correlated with the adsorption behavior in the absence of oxidant. The occurrence of optimum amount of H2O2 or of exposed surface area for the effective degradation of RhB could be explained by the scavenging effect of hydroxyl radical by H2O2 or by iron oxide surface. Sorption and decolourization rate of RhB as well as H2O2 decomposition rate were found to be dependent on the surface characteristics of iron oxide. The kinetic oxidation experiments showed that structural FeII content strongly affects the reactivity towards H2O2 decomposition and therefore RhB decolourization. The site density and sorption ability of RhB on surface may also influence the oxidation performance in iron oxide/H2O2 system. The iron (II, III) oxide catalysts exhibited low iron leaching, good structural stability and no loss of performance in second reaction cycle. The sorption on the surface of iron oxide with catalytic oxidation using hydrogen peroxide would be an effective oxidation process for the contaminants. [Copyright &y& Elsevier]

Abstract: In this work, the degradation and mineralization of the non-biodegradable azo dye Orange II (OII) was studied, making use of a heterogeneous Fenton-like oxidation process. For that, hydrogen peroxide activation was achieved by means of two different carbon-based catalysts, which have been impregnated with 7wt% of iron. The carbon supports employed are quite different, one of them being an activated carbon prepared from agricultural by-products (olive stone), while the other one is a carbon aerogel, prepared by carbonization of an organic resorcinol–formaldehyde polymer. The solids have been characterized using several techniques, namely N2 and CO2 adsorption at −196 and 0°C, respectively, mercury porosimetry, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Then, the catalyst''s performance in the Fenton-like oxidation of OII was compared, and the effects of the most relevant operating conditions (pH, catalyst concentration, H2O2 concentration and temperature) analyzed for the most promising one (the carbon aerogel based catalyst). In this catalyst, characterization data point for a very good iron dispersion on the carbon surface. This sample showed very good catalytic performances, with mineralization degrees as high as 90%. However, iron leaching from the support is also considerable leading to a progressive deactivation in consecutive reaction cycles. [Copyright &y& Elsevier]

Both the ≡Fe(III) reduction and the catalyst stability are the main obstacles limiting the application of such Fe-doped Fenton-like catalysts in endocrine disruptors removal. Herein, oxygen was introduced to the Fe-g-C 3 N 4 to fabricate a newly Fe–O-doped catalyst FeCA-g-C 3 N 4. The pseudo-first-order rate constant for bisphenol A (BPA) degradation in FeCA-g-C 3 N 4 system is 2.6 times higher than that in the traditional Fe-doped g-C 3 N 4 (FeCl 3 -g-C 3 N 4) system. And the formation of Fe–O bond can strengthen the stability of the catalyst. After operating 400 h, the π conjugate plane in the FeCl 3 -g-C 3 N 4 was completely destroyed, and the degradation of BPA was less than 3%. However, the crystal structure of FeCA-g-C 3 N 4 was relatively intact, and the degradation of BPA was still above 90%. According to the XPS and EXAFS spectra, the improvement of the FeCA-g-C 3 N 4 stability was attribute to the shorter lengthen of the Fe–O bond (1.47 Å). Besides, the introduction of electron-rich oxygen center can also effectively promote the reduction of ≡Fe(III) and directly activated H 2 O 2. Additionally, the electron-rich oxygen will also alleviate the shielding effect of halogen ions on the Fe sites, and the low concentration (<0.01 mM) of halide ions could even promote H 2 O 2 activation by 12.2%–24.5%. In conclusion, this study provides new insights to strengthen catalyst stability and accelerate electron transfer in the Fenton-like process, promoting its application in the actual wastewater purification. [Display omitted] • Fe–O-doped g-C 3 N 4 catalyst was fabricated by using ferric citrate as iron source. • Oxygen center can directly activate H 2 O 2 through single electron transfer. • Formation of Fe–O bond greatly improves the stability of the catalyst. • Oxygen center can improve the anti-interference ability of the catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Addition of Cu/Fe-AO-PAN to DBDP process can improve 4-FP abatement, as well as defluorination efficiency and TOC removal. • Enhanced 4-FP removal was attributed to the Fenton-like process between Cu/Fe-AO-PAN and H 2 O 2 produced by DBDP. • The formation of binuclear metal complexes when H 2 O 2 , Cu2+ and Fe3+ existed simultaneously was proposed. The enhancement effect of Cu/Fe-amination-polyacrylonitrile (Cu/Fe-AO-PAN) as a catalyst for H 2 O 2 produced by dielectric barrier discharge plasma (DBDP) on 4-fluorophenol (4-FP) degradation was explored. The addition of Cu/Fe-AO-PAN significantly increased the 4-FP removal rate and degradation energy efficiency from 61.0% and 1777 mg kWh−1 to 75.6% and 2203 mg kWh−1, respectively. The homologous total organic carbon (TOC) removal and defluorination efficiency were both increased (from 52.1% to 63.0% and 48.0% to 54.2%, respectively). The role of H 2 O 2 production was investigated by influencing parameter analysis and radical scavenging experiments. OH was verified to be a reactive species that increased 4-FP abatement, and was generated through electron transfer and binuclear metal complex formation between Cu/Fe-AO-PAN and H 2 O 2 during the Fenton-like process. This study provides a new insight into efficient wastewater treatment under DBDP process. [ABSTRACT FROM AUTHOR]

[Display omitted] • The right amount of cobalt ions could induce the formation of Fe 1-x S. • 100 mL orange II solution (30 mg/L) was degraded to 99.9% within 15 min. • OH and h+ played an important role in the photo-Fenton-like process. • FeS 2 -Fe 1-x S exhibited excellent stability and high catalytic degradation activity for other dyes. It is a challenge to develop heterogeneous Fenton-like catalysts with excellent performance and stability in the field of wastewater treatment. In this work, the FeS 2 -Fe 1-x S heterostructure catalyst was prepared by solvothermal method through adding cobalt element to change the particle nucleation process and inhibit the transformation process of pyrrhotite (Fe 1-x S) phase to pyrite (FeS 2) phase. Then, a series of experiments were devised to clarify the catalytic activity of FeS 2 -Fe 1-x S heterostructure. The degradation experiments exhibited that 99.9% degradation efficiency was achieved for 30 mg/L orange II solution within 15 min at the conditions of 0.2 g/L FeS 2 -Fe 1-x S, 2 mM H 2 O 2 and pH = 3.0. In addition, the reusability of the FeS 2 -Fe 1-x S catalyst was also investigated and the result displayed that degradation efficiency of orange II can reach 95.2% after eight cycles. The degradation of orange II was enhanced by Fenton reaction between FeS 2 -Fe 1-x S and dissolved oxygen, which could smoothly release Fe2+ and Fe3+ for the activation of H 2 O 2 to produce more hydroxyl radicals. Finally, the degradation pathway of orange II was proposed by detecting intermediates produced in FeS 2 -Fe 1-x S/H 2 O 2 photo-Fenton-like system by liquid chromatography-mass spectrometry (LC-MS). In short, FeS 2 -Fe 1-x S is a promising catalyst for removing the organic pollutants from solutions. [ABSTRACT FROM AUTHOR]

Nanoscale schwertmannites were fabricated and studied for their efficient degradation of 4–nitrophenol in Fenton–like processes. • Uniform nanoscale schwertmannites (nano-SCH) were prepared via PVP assisted pathway. • Nano-SCH was applied as efficient Fenton–like catalysts at various conditions. • Hydroxyl radicals were dominant active species for nitrophenol degradation. The Fenton process has been considered as one of the most promising advanced oxidation processes (AOPs) for the treatment of persistent organic pollutants (POPs). Herein, engineered nanoscale schwertmannite (nano–SCH) were fabricated from a PVP (polyvinylpyrrolidone) assisted room–temperature synthesis. The as–prepared well–dispersed nano–SCH materials were further studied as Fenton–like catalysts for 4–nitrophenol (4–NP) degradation in the presence of H 2 O 2. Results showed that the optimized nano–SCH–0.125 was able to degrade 91.0% of 4–NP in 60 min at 298 K, thanks to the nanoscale and hierarchical surface structures that provided abundant reactive sites at solid/solution interfaces. Moreover, mechanism study indicated that •OH radicals were the main reactive species responsible for the excellent 4–NP degradation performances during the Fenton–like processes. This work thus provides a viable pathway to engineer nanoscale materials with enhanced catalytic properties in oxidative degradation of environmental pollutants. [ABSTRACT FROM AUTHOR]

By exploiting the hydrophilicity of cellulose filter paper (FP) and the excellent chelating property of chitosan (CH) for Mn2+, we have designed an efficient and retrievable dip catalyst MnO 2 /CH-FP for Fenton-like degradation of methylene blue (MB) over a wide pH range from 2.8 to 11.2. The MnO 2 nanoparticles were uniformly immobilized in the CH-FP matrix by in-situ redox precipitation method where Mn(NO 3) 2 was treated with KMnO 4 at mild conditions. A series of MnO 2 /CH-FP hybrids with different MnO 2 loading were fabricated via varying concentration of Mn(NO 3) 2 solution, and their structure-function relationships were discussed based on detailed characterization. The optimal catalyst 1.0MnO 2 /CH-FP could cooperate with multiple low-concentration dosages of H 2 O 2 to efficiently degrade 95.6% MB in 90 min (50 mg L−1 MB, 1 g L−1 catalyst, 30 mg L−1 H 2 O 2 , pH 7). It is also shown that 1.0MnO 2 /CH-FP could still keep 83.3% degradation efficiency of MB after six cycles. Moreover, the activity of this composite greatly surpassed that of bare MnO 2 for nearly 50%, owing to its larger surface area and more accessible active sites. This method for preparing MnO 2 /CH-FP could effectively avoid the agglomeration of MnO 2 nanoparticles and make the reaction turn on/off almost instantaneously by mere insertion/removal. Image 1 • Nano-MnO 2 was in-situ anchored on the biopolymer by redox precipitation method. • It was an efficient and highly retrievable dip catalyst for Fenton-like degradation. • The hybrid has lager surface area and more accessible active sites than bare MnO 2. • The relationship between MnO 2 loading and degradation efficiency was discussed. • Multiple low-concentration doses of H 2 O 2 could achieve better decolorization. [ABSTRACT FROM AUTHOR]

• Bimetallic copper/zero-valent iron nanoparticles were syntethised by a facile method. • The degradation of SMZ was optimized by response surface methodology. • Hydroxyl radicals were the dominant oxidant species in SMZ degradation. • An early cleavage of the mediated sulfonamide group was observed. Zero-valent iron has been recognized as a promising catalyst for the degradation of micropollutants via Fenton-like reactions, however, the enhancement of its performance is insufficiently studied. In this feature, we investigate the activity of bimetallic copper/zero-valent iron nanoparticles (ZVI/Cu) as a heterogeneous catalyst for the degradation of sulfamethazine (SMZ), and intensively elucidate the reaction mechanism. The characterization of the catalyst by XRD, TEM, and EDS confirmed the growth of Cu° on the surface of the ZVI particles. Response surface methodology (RSM) coupled with a central composite design (CCD) optimized operating parameters such as pH, catalyst loading, H 2 O 2 dose, and initial SMZ concentration. Under the optimum conditions (pH = 3.0, H 2 O 2 concentration =2.0 g/L, ZVI/Cu loading =0.8 g/L), SMZ fell below the detection limit (0.036 mg/L) after 30 min of the reaction. The degradation mechanism revealed that hydroxyl radicals were the dominant oxidant species. However, the accumulated iron oxides on the shell of ZVI contributed to SMZ removal by adsorption. We propose a potential pathway for SMZ degradation based on the detected transformation products. This includes an early cleavage of the mediated sulfonamide group, which suggests an efficacious degradation into tentatively single-ring transformation compounds. [ABSTRACT FROM AUTHOR]

• Ce was used to enhance the surface characteristics of Cu-based materials. • Cu-Ce bimetallic catalyst showed much higher reactivity for FLC degradation. • The relationship between catalyst activity and structure was investigated in detail. • Mechanism of Cu-Ce composite catalyzed Fenton reaction is proposed. In order to fully exploit the potential of Cu-based Fenton systems, Ce was utilized to modify the Cu-based catalysts through one-pot synthesis. A typical antifungal drug, fluconazole (FLC), was selected as the target pollutant to evaluate the reactivity of as-synthetic Cu-Ce bimetallic catalysts. Evaluation test results indicated Ce 5% CuO y bimetallic materials exhibit the most excellent catalytic activity. Compared to copper monometallic catalyst, its fluconazole degradation efficiency and TOC removal rate are increased by 20% and 15%, respectively. Ce 5% CuO y also possess wide pH applicability (3.0–9.0) and maintain high activity after 4 runs. Radical quenching experiments and fluorescent probes tests showed that hydroxyl radicals (OH) played a dominant role in the degradation of FLC. The various characterization illustrated that Ce doping (2.5–5 at%) significantly improved the properties related to catalytic activity, such as morphology Cu(I) ratio, specific surface area, interface electron transfer rate and unpaired electron content. In particular, the increase in the unpaired electron content and Cu(I) ratio endow more electron-rich centers and active sites on the composite surface, which facilitates the H 2 O 2 to receive electrons and decompose into OH. Finally, the degradation intermediates during fluconazole oxidation were identified by LC/MC. [ABSTRACT FROM AUTHOR]

Heterogeneous Fenton processes with solid catalysts have gained much attention for water and wastewater treatment in recent years. In the field of solid catalysts, zero valent iron (ZVI) is among the most applicable due to its stability, activity, pollutant degradation properties and environmental friendliness. The main limitation in the use of ZVI in heterogeneous Fenton systems is due to its deactivation in neutral and alkaline conditions, and Fenton-like processes have been developed to overcome this difficulty. In this review, the effect of solution pH on the ZVI-Fenton performance is discussed. In addition, the pH trend of ZVI efficiency towards contaminants removal is also considered in oxic solutions (i.e., in the presence of dissolved O2 but without H2O2), as well as in magnetic-field assisted Fenton, sono-Fenton, photo-Fenton and microwave-Fenton processes at different pH values. The comparison of the effect of pH on ZVI performance, taking into account both heterogeneous Fenton and different Fenton-like processes, can guide future studies for developing ZVI applications in water and wastewater treatment. [ABSTRACT FROM AUTHOR]