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Waste drilling fluids produced from oil extraction can cause serious harm to the ecological environment; thus, the treatment of waste drilling fluids is urgent and important to ensure the sustainability and development of the oil extraction. In this work, we used the Fenton-like reaction method to degrade waste drilling fluids with SiO2-supported MnO2@Fe2O3 composite material as a catalyst in the presence of H2O2. During the Fenton-like reaction process, the MnO2@Fe2O3 interface exhibits exceptional activity by facilitating the production of ·OH species with high activity and strong oxidizing properties, which degrade the organic substances in the waste drilling fluids into smaller inorganic molecules, thereby reducing its COD value. Compared to the reaction only with H2O2, after reacting with sufficient SiO2-supported MnO2@Fe2O3 catalyst for 4 h at 60 °C in the presence of H2O2, the COD value of the waste drilling fluids is reduced by 36,495 mg L−1, a decrease of more than 95%. This performance is significantly superior to that of the traditional Fenton reagent FeSO4, which reduced the COD by 32,285 mg L−1, a decrease of 84%. This work provides an important composite catalyst, which is practically useful for the treatment of waste drilling fluids. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAP) is a material renowned for its exceptional capabilities in adsorbing and exchanging heavy metal ions, making it a widely employed substance within the environmental domain. This study aims to present a novel material, namely copper–HAP (Cu–HAP), which was synthesized via an ion exchange method. The resulting material underwent comprehensive characterization using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. Subsequently, based on the principle of the Fenton-like oxidation reaction, the material was used for the degradation of phenol. The outcomes of the investigation revealed that the optimal preparation conditions for the catalyst were achieved at a temperature of 40 °C, a pH value of 5, and a relative dosage of Cu–HAP at 100 mg/g. Under the reaction conditions of a catalyst dosage of 2 g/L, a 30% hydrogen peroxide concentration of 30 mM, a phenol concentration of 20 mg/L, a pH value of 6, a temperature of 40 °C, and the degradation rate of phenol impressively reached 98.12%. Furthermore, the degradation rate remained at 42.31% even after five consecutive cycles, indicating the promising potential of Cu–HAP in the treatment of recalcitrant organic compounds within this field. HIGHLIGHTS A novel copper-based catalyst (Cu–HAP) has been synthesized and utilized for the catalytic degradation of phenol.; Cu–HAP improved the efficiency of H2O2 in the traditional Fenton reaction.; Cu–HAP surface has a rich pore structure.; The phenol removal rate can still reach 42.31% after five times of reuse.;

The widespread use of pharmaceuticals and personal care products (PPCPs) in many fields has brought convenience to human lives but has also caused unavoidable environmental pollution issues. In particular, the resistance gene problem resulting from accumulating antibiotics that cannot be fully absorbed by biological individuals has been a concern; thus, it is urgent to find efficient technologies to boost the degradation efficiency of antibiotics in the environment. Here, an ε-MnO2 catalyst was prepared by a novel droplet-interface-drying method and utilized as a Fenton-like catalyst for efficiently degrading ciprofloxacin (CIP). The ε-MnO2 shell was formed preferentially at the gas–liquid interface and then continued to decompose into ε-MnO2 with abundant O vacancies in the air-insulated microcavity. The XPS result confirms that this particular preparation method can regulate the content of O vacancies in the material. Compared with ε-MnO2 samples obtained by the direct drying method (ε-MnO2-B), the catalytic performance of ε-MnO2 prepared by the droplet-interface-drying method (ε-MnO2-P) is significantly improved. By activating peroxymonosulfate (PMS) with the ε-MnO2-P catalyst, the CIP degradation efficiency can reach 84.1%. The detection and analysis of reactive oxygen species (ROS) in the ε-MnO2-P/PMS oxidation system confirms that ·OH, SO4·− and 1O2 are the main ROS for CIP degradation. This study highlights the creation of miniature hypoxic space to regulate the content of O vacancies in ε-MnO2, providing a new idea for the synthesis of other O-vacancy-rich materials. [ABSTRACT FROM AUTHOR]

Bimetallic FeMn nanoparticles based on a ferromanganese wad were successfully synthesized employing an entirely green approach. South African rooibos tea (RTea) extract was used as an environmentally friendly reducing and capping agent for preparing the Fe and Mn nanoparticles (nFeMn). The obtained nFeMn suspension and freeze-dried RTea capped nFeMn powder were characterized using several techniques. Elemental analysis conducted using XRF combined with ICP analysis revealed a metallic loading of 1.08 wt% of Fe and 0.25 wt% of Mn. The ultraviolet–visible spectroscopy (UV–vis) showed a broad shoulder in the UV region where the peaks of RTea and FeMn are located, implying bond formation during the reaction between RTea polyphenols and nFeMn. TEM analysis depicted a core–shell architecture for the nFeMn with an average size of 20 nm while the FTIR revealed that specific peaks observed in the spectrum of RTea extract were visible on that of the nFeMn powder, indicating the capping of nFeMn particles by the RTea extract. Finally, the reactivity of nFeMn powder as a Fenton-like reagent was probed for the decoloration of methylene blue (MB) from an aqueous solution. Fenton-like oxidation of MB followed a pseudo-first-order reaction kinetics with a rate constant of 0.23 A−1 min−1. The results showed that nFeMn removed MB dye with an efficiency of over 95% in the MB concentration range of 50–250 mg/L. Overall, the finding herein is unique because we directly used readily available raw material as a source of metals and a safe, practical reagent to prepare bimetallic FeMn nanoparticles that can be used to remove the color from dye wastewater, thus, creating a circular green process. [ABSTRACT FROM AUTHOR]

Magnetic geopolymer (Fe3O4-CGGP) was prepared from coal gangue, and evaluated by Fenton-like degradation of phenol. It was found that Fe3O4 with a particle size of 10-20 nm was uniformly dispersed on the surface of coal gangue geopolymer (CGGP). The saturation magnetization of Fe3O4-CGGP reached 35.68 emu/g. These indicated that Fe3O4-CGGP had a good catalytic activity and magnetic responsiveness. The effects of pH value, catalyst dosage, H2O2 dosage, and initial phenol concentration were investigated on Fenton-like degradation of phenol. The optimum conditions were as follows: pH is 3.5, catalyst dosage 0.5 g/L, and H2O210 mmol/L. Under the parameters, phenol can be completely degraded in 60 min. The free radical quenching experiment revealed that ·OH dominates the catalytic process in the Fe3O4-CGGP/H2O2 system.

In this study, the zero-valent iron Fenton reagent (ZVI Fenton-like) system was combined with the chemical precipitation method for the deep treatment of desulfurization wastewater from coal-fired power plants, and the chemical oxygen demand (COD) was used as the evaluation criterion for organic matter in the desulfurization wastewater. The effects of reaction time, H2O2 dosage, zero-valent iron dosage, pH, and reaction temperature were also investigated. The results showed that the COD concentration of the effluent was the lowest when the running time of the ZVI Fenton-like reagent system was 1 h, the dosage of H2O2 was 33.3 mg·L−1, the dosage of iron was 0.075 g·L−1, the pH was 4.5~6.5, the reaction temperature was 35 °C, the COD concentration of the wastewater was the lowest and its operating conditions were the best, and the internal reaction mechanism was finally deduced. In summary, the zero-valent iron Fenton reagent system provides a new idea for the treatment of desulfurization wastewater from coal-fired power plants. [ABSTRACT FROM AUTHOR]

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[Display omitted] • Confined catalysts were prepared by modulating the proportion of β-CD with cavity. • As the cavity increases, the catalytic activity displayed a volcanic peak trend. • MCF exhibited superior performance for PMS activation and TCP elimination. • The existence of narrower channels facilitated the electron transfer to remove TCP. • Possible degradation pathways for TCP in MCF/PMS system were proposed. Rationally regulating the structure of catalysts in Fenton-like reactions provides abundant opportunities for the efficient remediation of organic micropollutants from the aqueous environment, yet it is challenging to achieve superior reactivity and the catalytic mechanisms have rarely been systematically elucidated. Herein, we present a simple strategy to synthesize confined catalysts with different pore-size distributions by modulating the proportion of β-cyclodextrin (β-CD) with a cavity. The degradation performance of the confined catalyst MCF with the smallest pore size (5.9 nm) was remarkably enhanced compared to the unconfined catalyst NCF, mainly by 1O 2 and electron transfer. As the cavity content increases, the reactivity displayed an unexpected volcanic peak tendency. The pseudo-first-order reaction constant of MCF was 2.6 times higher than that of HCF (8.2 nm) in Fenton-like oxidation with peroxymonosulfate (PMS). Comparative control experiments demonstrated that the appropriate structure can significantly facilitate the diffusion and degradation process of pollutants that are adsorbed in the confined channels. The MCF/PMS system exhibited strong adaptability to coexisting ions and pH in the water matrix, and the intermediate products were harmless to the environment. This unusual catalytic mechanism and the structural regulation strategy will establish new insights into boosting the catalytic performance for the efficient removal of organic micropollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single atom FeN 4 active sites were induced by neighbouring nitrogen vacancies. • Fe loading improved the absorption performance and catalytic activity of catalysts. • Both radical and non-radical pathways were involved in peroxydisulfate activation. • Multi-component catalytic system integrated Fenton-like oxidation and photocatalysis processes for contaminant elimination. The regulation of heterogeneous material properties to strengthen the peroxymonosulfate activation to destroy refractory pharmaceuticals remains a challenge. Herein, a promising nitrogen-deficient catalyst (FeCN) with single atom Fe and Fe 2 O 3 nanoparticles dispersing on g -C 3 N 4 matrix was synthesized and applied as a competent peroxydisulfate (PDS) activator for tetracycline (TC) degradation under visible light. The K-edge X-ray absorption fine structures and 57Fe Mössbauer measurements confirmed the unique configuration of Fe 2 O 3 and single atom Fe active sites (pyrrolic and pyridinic FeN 4) induced by the neighbouring nitrogen vacancies. The theory calculations and experiments provided a deep insight into the PDS activation and TC degradation via radical and non-radical pathways. The pyrrolic FeN 4 active sites dominated the electron transfer, while the pyridinic FeN 4 and Fe 2 O 3 decomposed PDS to produce free radicals. The synergistic effect between the Fenton-like oxidation and photocatalysis is responsible for efficient TC degradation. This study offers a new strategy by integrating novel catalysts and advanced oxidation technology for effective wastewater purification. [ABSTRACT FROM AUTHOR]

The widespread use of pharmaceuticals and personal care products (PPCPs) in many fields has brought convenience to human lives but has also caused unavoidable environmental pollution issues. In particular, the resistance gene problem resulting from accumulating antibiotics that cannot be fully absorbed by biological individuals has been a concern; thus, it is urgent to find efficient technologies to boost the degradation efficiency of antibiotics in the environment. Here, an ε-MnO2 catalyst was prepared by a novel droplet-interface-drying method and utilized as a Fenton-like catalyst for efficiently degrading ciprofloxacin (CIP). The ε-MnO2 shell was formed preferentially at the gas–liquid interface and then continued to decompose into ε-MnO2 with abundant O vacancies in the air-insulated microcavity. The XPS result confirms that this particular preparation method can regulate the content of O vacancies in the material. Compared with ε-MnO2 samples obtained by the direct drying method (ε-MnO2-B), the catalytic performance of ε-MnO2 prepared by the droplet-interface-drying method (ε-MnO2-P) is significantly improved. By activating peroxymonosulfate (PMS) with the ε-MnO2-P catalyst, the CIP degradation efficiency can reach 84.1%. The detection and analysis of reactive oxygen species (ROS) in the ε-MnO2-P/PMS oxidation system confirms that ·OH, SO4·− and 1O2 are the main ROS for CIP degradation. This study highlights the creation of miniature hypoxic space to regulate the content of O vacancies in ε-MnO2, providing a new idea for the synthesis of other O-vacancy-rich materials.

Ion exchange resins (IERs) are widely used to remove radioactive contaminants from various commercial nuclear power plant systems. After the completion of their useful life cycle, IERs are removed from the nuclear facility and are known as spent resins. In the past few decades, the development of Fenton/Fenton-like treatments for the management of spent resins has received considerable attention because of their potential to completely break down the IER structure into harmless compounds (e.g., carbon dioxide, water, and inorganic salts). In addition, after Fenton-like treatments, the resulting solutions containing radionuclides can be easily immobilized to stable waste. In this review, we critically discuss the key developments in Fenton/Fenton-like dissolution, degradation, and mineralization of spent resins. We describe the important reaction parameters (initial pH, resin dosage, catalyst type and dosage, hydrogen peroxide dosage, flow rates of the catalyst and oxidant, reaction temperature, treatment time, and other specific parameters) for various Fenton/Fenton-like treatments of spent resins. Moreover, this review focuses heavily on the major reaction intermediates generated in Fenton-like treatments. In the final section of this review (conclusions and perspectives), we discuss the major challenges and suggest future research directions need to be addressed to improve the efficiency of Fenton-like treatments of spent resins.

Fluorinated Fe3O4 microspheres with 7.1 ± 1.4 wt% of fluoride (F-Fe3O4-1) were prepared via glycothermal synthesis. Fluorination significantly enhanced the activity of F-Fe3O4-1 in catalytic wet peroxide oxidation of anionic dyes (including orange G (OG) and congo red) at pH ~7. However, the promotional effect of fluorination became less obvious for amphoteric rhodamine B and was not observed for cationic methylene blue. After reacting with H2O2 (40 mM) for 2 h at pH 6.5 and 40 °C, the decolorization rates of OG (0.1 mM) and the pseudo-first-order rate constant were 96.8% and 0.0284 min−1 over F-Fe3O4-1 versus 17.6% and 0.0011 min−1 over unmodified Fe3O4. The effects of reaction parameters (initial H2O2 concentration and pH value and reaction temperature) on OG decolorization with H2O2 over F-Fe3O4-1 were investigated. The reusability of F-Fe3O4-1 was demonstrated by OG decolorization in eight consecutive runs. Fluorination increased the isoelectric point of F-Fe3O4-1 to 8.7 and facilitated the adsorption and degradation of anionic dyes on the surface of F-Fe3O4-1 at pH ~7. Scavenging tests and EPR spectra supported that hydroxyl radicals were the main reactive species for the OG decolorization over F-Fe3O4-1. [ABSTRACT FROM AUTHOR]

In this study, a novel strategy for selectively generating Co(IV)=O species during peroxymonosulfate (PMS) activation was proposed, utilizing an optimized Co 4 Cu 1 -layered double hydroxide (LDH) material with low-coordination and high-spin-state Co sites. The incorporation of Cu(II), influenced by the Jahn-Teller effect, altered the geometry and coordination at Co(III) sites, optimizing the filling of Co 3d orbitals. The Co 4 Cu 1 -LDH/PMS system demonstrated exceptional catalytic activity for degrading emerging contaminants (ECs) across various water matrices, with a high concentration of Co(IV)=O generation. Continuous flow experiments showed an average 97.51 % degradation over 10 hours, indicating significant practical potential. Mechanistically, enhanced performance was attributed to a single electron transfer process and optimized orbital configurations for oxygen ligands at Co(III) sites. This study offers both theoretical insights and practical guidance for developing efficient catalysts targeting Co(IV)=O species in Fenton-like systems. [Display omitted] • High-spin Co(III) sites was constructed for selective formation of Co(IV)=O species. • Jahn-Teller distortion was applied for the construction to regulate Co sites. • Co(IV)=O showed strong oxidation ability towards various emerging contaminants. • Excellent performance was also achieved in continuous flow wastewater treatment. [ABSTRACT FROM AUTHOR]

Red mud (RM) and sewage sludge (SS) are growing massive industrial wastes, and recycling utilization is considered a suitable disposal method. In this study, a novel Fenton-like catalyst was synthesized through co-pyrolysis with RM and SS with high alkaline endurance, presenting a sustainable full resource utilization of the SS. The advanced oxidation process effectively breaks down the SS structure to release phosphorus(P) for struvite recovery. The residual SS can be repurposed as fuel following direct flocculation and dehydration. There is no need for complex pH adjustments throughout. XRD pattern revealed zero valent iron (ZVI, Fe0) as the primary catalyst phase. Experimental findings demonstrated that H 2 O 2 efficiently disrupts bacterial structures, leading to a significant reduction in bound extracellular polymer (TB-EPS) in the SS. It was observed that the release rate of P reached nearly 100% after 60 min of reaction. The purity of recycled struvite reaches 94.9%, and the heavy metal content meets national standards. Planting experiments indicated that recycled struvite exhibited superior fertility compared to commercial fertilizers. The proposed sustainable resource production and recycling process of SS strongly supports the construction of a "city without waste". [Display omitted] • An magnetic recyclable catalyst were prepared through co-pyrolysis of red mud and sewage sludge (SS-RM) suits for alkaline Fenton-like reaction. • The SS was teated by the alkaline heterogeneous Fenton-like oxidation with SS-RM for phosphorus (P) recovery with a release efficiency proximate 100%. • The purity of recycled P though struvite reaches 94.9%, and exhibited superior fertility to commercial fertilizers. • This article demonstrates a promising prospect for resource oriented utilization of industrial solid waste. [ABSTRACT FROM AUTHOR]

We prepared a double-layer magnetic nanocomposite Fe3O4@ZIF-8@ZIF-67 by layer-by-layer self-assembly. Fe3O4@ZIF-8@ZIF-67 was used to remove tetracycline from an aqueous solution via a combination of adsorption and Fenton-like oxidation. Depending on the outstanding porous structure of the Fe3O4@ZIF-8@ZIF-67, a high adsorption capacity for tetracycline was 356.25 mg g−1, with > 95.47% removal efficiency within 100 min based on Fenton-like oxidation. To better understand the mechanisms involved in integrated adsorption and Fenton-like oxidation, various advanced characterization techniques were used to monitor the changes in morphology and composition of Fe3O4@ZIF-8@ZIF-67 before and after removal of tetracycline. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) all supported adsorption and Fenton oxidation of tetracycline. This study extends the application of Fe3O4@ZIF-8@ZIF-67 for environmental remediation. [ABSTRACT FROM AUTHOR]

Iron oxide nanoparticles with controlled size anchored on CNT skeleton (Fe 2 O 3 @Fe 3 O 4 /CNT) synthesized in a one-step hydrothermal reaction has good potential in lithium-ion storage and Fenton-like oxidation. [Display omitted] In this work, heterogeneous hematite (Fe 2 O 3) and magnetite (Fe 3 O 4) nanoparticles are jointly engineered on the external surface of multi-walled carbon nanotubes (CNTs) to construct a composite material (Fe 2 O 3 @Fe 3 O 4 /CNT). A simple one-step redox reaction is triggered in a hydrothermal reaction system containing functionalized CNT (FCNT) aqueous suspension and iron foils. Both Fe 2 O 3 and Fe 3 O 4 nanoparticles with controlled size are generated and well dispersed in the interconnected CNT framework. Controlled samples of Fe 2 O 3 @Fe 3 O 4 and Fe 3 O 4 /CNT have also been prepared and used to investigate the synthetic mechanism and evaluate the lithium-ion storage performances. As an anodic active material for lithium-ion batteries, the Fe 2 O 3 @Fe 3 O 4 /CNT composite delivered a high reversible capacity of about 924 mAh·g−1 for 200 continual charge/discharge cycles under a high current rate of 1000 mA·g−1. As a catalyst in a Fenton-like reaction for degrading methyl orange (MO) contaminant in waterbody, the Fe 2 O 3 @Fe 3 O 4 /CNT composite exhibited an attractive decomposition efficiency (99.5% decomposition within 60 min) and good stability. The beneficial factors contributing to the inspiring performances are discussed. The effective and scalable material design and synthesis method can be regarded to have good potential in other fields. [ABSTRACT FROM AUTHOR]

This study proposed a two-stage oxidation process of combining potassium ferrate and hydrogen peroxide to reduce the amount of potassium ferrate and further improve the treatment effect of neomycin sulfate wastewater. Compared with the K2FeO4 single oxidation process and the H2O2 single oxidation process, the K2FeO4 + H2O2 two-stage oxidation process had a higher chemical oxygen demand (COD) removal rate than the sum of the two single oxidation processes, showing a certain synergy. In addition, H2O2 dosage, system acidity, reaction temperature and reaction time did not affect this conclusion. In the first stage, the optimized processing parameters are the dosage of K2FeO4 7 g/L, pH value 4, reaction time 40 min and temperature 40°C. In the latter stage, the appropriate dosage of H2O2 is 20 mL/L, pH value is 3, the reaction time is 50 min and the reaction temperature is 40°C as same as the first stage, the COD removal rate of neomycin sulfate wastewater is 96.83%, showing a good treatment effect and obvious synergistic effect. [ABSTRACT FROM AUTHOR]

The photocatalytic technology based on Metal-Organic Frameworks (MOFs) has shown promising applications in the field of antibiotic pollution control. However, it still faces challenges in efficiently removing high-concentration antibiotic wastewater. A typical Fe-containing MOF, MIL-53(Fe), was successfully synthesized and demonstrated efficient photocatalytic activity under visible light irradiation for high-concentrations of tetracycline hydrochloride (TCH). However, the bare MIL-53(Fe) exhibited unsatisfactory photocatalytic performance. To overcome the low degradation efficiency resulting from the rapid recombination of light-induced electron-hole pairs, H 2 O 2 was introduced as an external electron acceptor to establish a synergistic Fenton-like system to couple with the photocatalysis process. The results showed that in the MIL-53(Fe)/H 2 O 2 /Vis system, 99% of 1 g/L TCH was degraded within 80 min, while the degradation efficiency of the MIL-53(Fe)/Vis process was only 4.89% under identical conditions. The degradation mechanism of the coupling system was performed by radical scavenging experiments and Electron Spin Resonance characterization. The results indicated that ·OH was the dominant radical in the coupled reaction, and ·O 2 - and h+ also played a role in this system. The significant improvement in TCH degradation efficiency during the coupling process was attributed to the following three factors: (1) In the coupling reaction process, photo-generated electrons can stimulate H 2 O 2 to form ·OH radicals, inhibiting the recombination of photo-generated electrons and holes, improving the efficiency of the photocatalytic reaction. (2) FeIII in MIL-53(Fe) can be excited by photo-generated electrons and converted to FeII, which then stimulates H 2 O 2 to form ·OH radicals. (3) FeIII in MIL-53(Fe) can convert with FeII, stimulate H 2 O 2 to form ·OH radicals, and participate in the degradation reaction. In addition, the reusability and stability of the MIL-53(Fe) photocatalyst in the coupled system, as well as the impact of operational parameters, were systematically studied. This work demonstrates a feasible strategy for environmental remediation by enhancing the efficiency of MIL-53(Fe) in photocatalytic Fenton-like systems, thereby providing a viable approach for the treatment of high-concentration antibiotic wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

Fe-bearing salt and minerals are common reagents used in activating peroxymonosulfate (PMS) for Fenton-like oxidation in wastewater treatment. Fe-bearing reagents are used in mass production, which generate abundant Fe-bearing waste sludge in the absence of a reductant for Fe3+/Fe2+ cycling. Herein, a novel Fe/S-bearing mineral, erdite, was synthesized with a one-step hydrothermal route. The material exerted an Fe/S synergetic effect for p-nitrophenol degradation upon PMS activation and showed a one-dimensional structure similar to that of (FeS2)nn−. It contained short rods with diameters of 100 nm and lengths ranging from 200 to 400 nm. It grew radically to 0.8–2 μm in length upon the addition of MnO2. Ps-0.5, prepared by adding MnO2 in an Mn/Fe molar ratio of 0.5, showed optimal efficiency in removing approximately 99.4% of p-nitrophenol upon PMS activation. Only 3.3% of p-nitrophenol was removed without MnO2. The efficiency of p-nitrophenol removal through Ps-0.5 activation was higher than that through FeSO4, nanoscale zero-valent iron (nZVI), CuFeS2, and MnSO4 activation. The formed erdite rods were spontaneously hydrolyzed to Fe/S-bearing flocs, in which an electron was used by structural S to reduce Fe3+ to Fe2+ upon PMS activation. The reduction resulted in a high p-nitrophenol removal rate. This study provided new insight into the development of an effective PMS activator in wastewater treatment. [ABSTRACT FROM AUTHOR]

Natural iron minerals and zero-valent metals have been widely tested as catalysts for the Fenton-like process, but the systematical comparison study about their catalytic performance was rarely conducted, and the risk of the secondary pollution of toxic heavy metals was still not uncertain. In this paper, a comparison study of applying pyrite, ilmenite, vanadium titano-magnetite (VTM), zero-valent iron (ZVI), and zero-valent copper (ZVC) as Fenton-like catalysts for the removal of imidacloprid was performed. The results showed that ZVI exhibited the highest activity among the recyclable solid catalysts with a removal rate of 96.8% at initial pH 3 using 10.78 mmol/L H2O2, due to iron corrosive dissolution. Vanadium titano-magnetite (VTM) exhibited the best activity at first use among tested minerals but with low reusability. Pyrite with stable morphology showed a medium but sustainable ability to degrade imidacloprid, achieving a removal rate of 10.5% in the fifth use. The reaction much favored the acidic condition of initial pH around 2 or 3. Meanwhile, there was a significant positive correlation between removal efficiency and dissolved Fe or Cu concentration. Pyrite was considered to be a promising catalyst in Fenton-like reaction. It was suggested that the system proceeded predominantly through a homogeneous route via dissolved Fe or Cu ions. Except ZVC and VTM, other tested catalysts showed the low possibility of causing secondary pollution of toxic metals in the application of Fenton-like process. [ABSTRACT FROM AUTHOR]

Facile preparation of functional hydrogel materials for environmental catalysis is a hot research topic of soft materials science and green catalysis. In this study, a carboxylcellulose hydrogel confined Fe 3 O 4 nanoparticles composite catalyst (Fe 3 O 4 @CHC) with magnetic recyclability has been synthesized by taking the advantages of the newly developed cellulose solution in tetramethyl guanidine/DMSO/CO 2 through in situ acylation using mixed cyclic anhydrides and ion exchange reaction. The achieved Fe 3 O 4 @CHC hydrogel catalyst was shown to be an more efficient and better Fenton-like catalyst for decomposition of the organic dye rhodamine B (RhB) in the presence of hydrogen peroxide, with almost complete decomposition occurring within 180 min, in comparison with Fe 3 O 4 @cellulose hydrogel (CH) with excellent recyclability. This work provided a facile strategy for the preparation of hydrogel-based functional composite green catalytic materials, which has potential applications in green catalysis. [Display omitted] • Cellulosic hydrogel anchoring carboxylic moiety is developed as a superior carrier for nano Fe 3 O 4 than cellulose. • Fe 3 O 4 NPs in situ hydrogel network have an average diameter size of 4.3 nm. • The coordination ability of carboxylic and hydroxyl groups moiety is response for the good NPs stability and dispersion. • The prepared Fe 3 O 4 NPs have the desired catalytic activity for the Fenton-like degradation of Rhodamine B. [ABSTRACT FROM AUTHOR]

The integration of two different advanced oxidation processes can not only avoid their individual shortcomings but also utilize the synergistic effects between them. Herein, CoFe2O4 modified g-C3N4 composite (CoFe2O4@g-C3N4) was synthesized and used for building a novel coupled system, in which two processes of visible light-activated photocatalysis and sulfate radical-based Fenton-like oxidation have been combined together to provide a synergistic reaction path for the removal of rhodamine B. The coupled system exhibited a drastically enhanced catalytic efficiency compared with the photocatalytic or Fenton-like process alone. It also showed a significantly enhanced catalytic activity compared with g-C3N4, CoFe2O4 or their simple mixture. The improved catalytic performance can be ascribed to the efficient separation of photogenerated carriers as well as more available catalytic reactive sites for peroxymonosulfate (PMS) activation due to the synergistic effects between the photocatalytic and Fenton-like processes. In 30 min, 96% RhB was degraded using PMS activated by a CoFe2O4@g-C3N4 composite with 3% CoFe2O4 loading under visible light irradiation, and the synergistic index in such system reached as high as 3.07. Such system can be used at a wide pH range of 3.0–10.0. The composite also showed good stability for its practical applications. [ABSTRACT FROM AUTHOR]

Two new heterogeneous catalysts (Cu-sand) have been synthesized by supporting copper on the surface of natural sand using two defined methods such as chemical vapor deposition (CVD) and dry evaporation (DE). The Cu-sand catalysts were characterized by several techniques. SEM-EDX analysis indicated that 13.86 wt% of copper species were dispersed on the surface of Cu-sand (CVD) catalyst whereas 11 wt% were agglomerated on the Cu-sand (DE) surface. The presence of copper species was more noticeable in the XRD pattern for the Cu-sand (CVD) catalyst. The catalytic performance of the prepared catalysts was evaluated in the Fenton-like oxidation of Alizarin red S dye (ARS). The reactivity and stability of the two catalysts were differentiated by studying the influence of the supported amount of copper, activity of leachate and the reuse of catalyst on the conversion of initial concentration of ARS. ARS oxidation has been investigated under various experimental conditions. The best ARS conversion rate was about 95% when using Cu-sand (CVD) catalyst in optimal conditions: [H2O2]0 = 10 mmol/L, temperature = 40 °C and the addition of H2O2 in two stages (0 min and 20 min of treatment). CVD method makes it possible to prepare an efficient and stable catalyst. [ABSTRACT FROM AUTHOR]

The use of nanoscale zero-valent iron (nZVI) for the purification of contaminated water and soil was investigated for its high potential to remove subsurface contaminants. In this study, the mechanism of diclofenac (DCF) degradation by nZVI and the combined process of nZVI and hydrogen peroxide (H2 O2) are discussed. The results demonstrated that nZVI with acidic conditions had a certain degradation efficiency on DCF, with a removal rate about 30% in a 2-hour reaction at pH 5. The combined process of nZVI and H2 O2 could obviously remove DCF, with a removal rate greater than 90% in a 2-hour reaction at pH 5. In nZVI system, under acidic and aerobic conditions, Fe2+ and H2 O2 can be generated to form a Fenton-like system. Meanwhile, the release of electrons from nZVI could promote the reductive dechlorination of DCF. In nZVI/H2O2 system, the high removal rate of TOC was also showed the DCF mineralization by the Fenton-like oxidation. [ABSTRACT FROM AUTHOR]

Treatment of wastewater generated in carpet manufacturing is a problematic issue, mainly because of the toxic impact of chemicals used in different processes. Fenton oxidation may be a suitable approach for reducing toxicity but the cost of chemicals may be prohibitive to adopt this process as the main treatment phase. In this context, this study explored the feasibility of implementing either Fenton or Fenton-like oxidation process as a pretreatment stage before the biological treatment of carpet manufacturing effluents. It also included optimization of operation parameters using response surface methodology. Optimization was mainly focused on molar ratios of H2O2/COD and H2O2/Fe along with the reaction time for Fenton and Fenton-like advanced oxidation. For the Fenton process, the optimum H2O2/COD and H2O2/Fe2+ molar ratios were determined as 0.06 and 0.60 mol/mol, respectively. Different optimum values of 0.29 and 4 mol/mol, respectively, were applied to the same molar ratios for the Fenton-like oxidation. The Fenton process yielded 81% and 68% for COD removal and toxicity reduction, respectively. Similarly, removal yields of 62% for COD and 76% for toxicity were achieved by means of the Fenton-like oxidation. This process proved to be suitable as a pre-treatment step, where adequate toxicity reduction was achieved to allow effective COD removal in the following biological treatment phase. [ABSTRACT FROM AUTHOR]

The combination of metal-organic frameworks (MOFs) with nano-carbon materials is an emerging field among the researchers now a days. The addition of carbon materials (CNTs/GO) increases the Physico-chemical characteristics of parent MOFs. In this mini review the photocatalytic and Fenton-like oxidation behavior of these hybrid nanocomposites has been discussed. Additionally, the efficient remediation of a number of pollutants (VOCs, heavy metals and toxic gases) through adsorptive removal from atmospheric environment has been presented. Finally, the recyclability and stability of MOFs-C along with future perspectives are also presented at the end of this review.

Heterogeneous Fenton-like catalysts with the activation of peroxymonosulfate (PMS), which offer the advantages of fast reaction rate, wide functional pH range and cost efficiency, have attracted great interest in wastewater treatment. In this study, a novel magnetic MnO2/Fe3O4/diatomite nanocomposite is synthesized and then used as heterogeneous Fenton-like catalyst to degrade the organic pollutant methylene blue (MB) with the activation of PMS. The characterization results show that the Fe3O4 nanoparticles and nanoflower-like MnO2 are evenly distributed layer-by-layer on the surface of diatomite, which can be readily magnetically separated from the solution. The as-prepared catalyst, compared with other Fenton-like catalysts, shows a superb MB degradation rate of nearly 100% in 45 min in the pH range of 4 to 8 and temperature range of 25 to 55 °C. Moreover, the nanocomposite shows a good mineralization rate of about 60% in 60 min and great recyclability with a recycle efficiency of 86.78% after five runs for MB. The probable mechanism of this catalytic system is also proposed as a synergistic effect between MnO2 and Fe3O4.

Sludge-based activated carbon (ZAC) was successfully employed as both adsorbent and catalyst for the oxidation process of reactive yellow 86 (RY86) and reactive black 5 (RB5). Physicochemical properties of the prepared sewage sludge-derived activated carbon were evaluated by N2 adsorption/desorption, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The effects of parameters such as initial pH, H2O2 concentrations, ZAC dosages, dye concentrations and temperature on the removal of RY86 and RB5 were investigated. Kinetics results showed that the adsorption rates of RY86 and RB5 by ZAC can be approximated by the pseudo-first order model, and that the oxidation rates by Behnajady–Modirshahla–Ghanbery (BMG) model. Under the optimum conditions in the experiment, i.e. pH = 6.0, T = 303 K, [H2O2] = 49.5 mmol/L, [ZAC] = 4 g/L, [dyes] = 300 mg/L and t = 150 min, 99%, 88% and 84% of colour, COD and TOC were removed by Fenton -like oxidation for RY86, while for RB5, the three removal rates were 90%, 70% and 62%, respectively, indicating that sludge-based activated carbon can be used as an effective catalyst to oxidation of dyes by H2O2 from coloured wastewater. [ABSTRACT FROM AUTHOR]

The application of a novel sulfidation modified Fe 3 O 4 nanoparticles (S-Fe 3 O 4 NP) as catalyst for degradation of dyes-containing wastewater through Fenton-like reaction is investigated in the current research. Results demonstrate the as-prepared S-Fe 3 O 4 NP is mainly composed of interconnected FeS 2 and sulfur-doped Fe 3 O 4 , which can be recovered from aqueous solution by magnetic separation method. S-Fe 3 O 4 NP/H 2 O 2 catalytic system exhibits great advantage and much higher catalytic performance over Fe 3 O 4 based Fenton-like process, which can effectively degrade RhB at wide pH range from 3 to 9. It also presents excellent recyclability in the first three cycles and high catalytic activity towards degradation of various azo dyes such as MB, MG and AR-73. The H+ species, Fe2+ ions and surface Fe2+ active sites generated in the S-Fe 3 O 4 NP/H 2 O 2 system can significantly facilitate the production of hydroxyl radicals and this synergetic effect between FeS 2 and sulfur-doped Fe 3 O 4 leads to the enhanced catalytic performance of S-Fe 3 O 4 NP. Unlabelled Image • Sulfidation modified Fe 3 O 4 nanoparticles were synthesized for the first time. • S-Fe 3 O 4 NP can be used as an efficient Fenton-like catalyst for dyes degradation. • S-Fe 3 O 4 NP shows high catalytic activity at wide pH range from 3 to 9. • The excellent catalytic performance was owing to multiple structural features. [ABSTRACT FROM AUTHOR]

Hemp fiber was applied to prepare activated carbon by phosphoric acid activation at a carbonization temperature of 400 °C. Then, zero-valent iron particles were immobilized onto the surface of hemp-derived AC (HAC), and the composites (ZVI@HAC) were used as heterogeneous catalysts for Fenton-like treatment of pulping effluent. The as-prepared catalysts were characterized. The optimum conditions for Fenton-like reaction and the reusability of the catalyst were investigated. Results showed that ZVI particles were well-distributed on the surface of HAC without aggregation. Both HAC and ZVI@HAC had a microporous structure. With the loading of ZVI, the catalysts were endowed with magnetism and more active sites. Under the optimal conditions (3.0 initial pH, 35 mmol/L H2O2, and 3.0 g/L 2-ZVI@HAC), the chemical oxygen demand (COD) removal rate reached 87.74%. This work illustrated the feasibility of HAC as a carrier of ZVI and the ZVI@HAC was an effective heterogeneous Fenton catalyst. [ABSTRACT FROM AUTHOR]

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• Green Mn2O3 was used to active PDS for removing E3 from real wastewaters. • Effects of substrates of wastewaters on the removal of E3 by Mn 2 O 3 /PDS system. • Combined DFT, LC-MS analyses and ECOSAR to understand the reaction mechanisms. • The degradation pathway and toxicity of intermediates were predicted. While green synthesized Mn 2 O 3 has been used to activate peroxydisulfate (PDS) to degrade estrogens, effective application in real wastewater is less common due to variation in environmental matrices in wastewater. Here, green synthesized Mn 2 O 3 was used as a Fenton-like catalyst to activate PDS for estriol (E3) degradation in wastewater. The results show that the high concentration of K+ and humic acid in wastewater could inhibit the activation process of the Mn 2 O 3 /PDS system, resulting in low removal efficiency of E3 in wastewater. However, when the concentration of PDS was increased to 15 mM, the removal efficiency of E3 in medical wastewater can reach 100 %, because the high PDS concentration increases the main reactive oxygen species singlet oxygen (1O 2) in medical wastewater. XRD and SEM-EDS analysis indicate that the crystal structure of Mn 2 O 3 is stable, with a consistent rice grain-like morphology before and after reaction. XPS results show no obvious changes in the percentages of Mn(II), Mn(III) and Mn(IV) before and after reaction, indicating that Mn 2 O 3 has good stability when degrading E3 in medical wastewater. Based on density functional theory (DFT) calculations, liquid chromatography-mass spectrometry (LC-MS), and ecological structure–activity relationship (ECOSAR) modeling data analysis, the reactive oxygen species produced by the Mn 2 O 3 /PDS system mainly attack the benzene ring structure of E3, where the toxicity of its intermediate products declines significantly after breaking the benzene ring structure. Overall, this work provides greater understanding of the E3 degradation pathway and the toxicity of its degradation products. [ABSTRACT FROM AUTHOR]

The classical Fenton system composed of Fe(II) and H2O2 uses harsh oxidative conditions and cannot realistically simulate physiological oxidations which are less severe. Here, reactive oxygen species (ROS) were generated with a combination of CoSO4 and H2O2 to provide milder conditions. DNA was used as a biologically meaningful probe for monitoring the oxidative conversion. Oxidative hazard on DNA was accomplished in ammonia/ammonium chloride buffer at 37 °C, and the Fenton reaction was stopped with trichloroacetic acid (TCA). A suitable aliquot of this solution was added to cupric ion reducing antioxidant capacity (CUPRAC) reaction mixture, and the absorbance at 450 nm was recorded. The oxidized species derived from DNA were CUPRAC-reactive while intact DNA was not. The protective effects of antioxidants (AOxs), known to have radical scavenging effects, were tested; green tea and a synthetic fetal bovine serum (FBS) were also successfully used as real ROS scavengers. Although the classical iron-based Fenton procedure applied in ethanol medium generated CUPRAC-responsive products, the proposed system was perfectly ethanol-tolerant, enabling the CUPRAC measurement of DNA oxidation products against an unaffected reagent blank. The protective effects of phenolic antioxidants, perfectly solubilized in ethanol, could also be measured. [ABSTRACT FROM AUTHOR]

The zero valence iron (ZVI) Fenton-like catalyst has two main defects: one defect is that the surface passivation impairs the reusability of catalysts, and the other defect is the deactivation under neutral working pH. To overcome these problems, we synthesized a dendrite-like ZVI@Fe 3 O 4 composite modified with carbon quantum dots (CQDs) and oxygen vacancies (OVs) by electrodeposition and solvothermal treatments. The results showed that the CQDs (approximately 5 nm) with polar C-groups on the surface of the composites were derived from the carbonization of glucose during thermal treatment, and the OVs (atomic scale) at the junction of Fe 3 O 4 and the CQDs were induced by the reduction of the CQDs. The synthesized composite possessed excellent catalytic activity and reusability. Under the condition of 6 mmol/L H 2 O 2 , the synthesized composite catalyst with the dose of 0.10 g/L completely removed 35 ppm phenol within 10 min at pH 4.0 and within 60 min at neutral pH. Furthermore, the catalytic mechanism was proposed. The reducing effect of CQDs accelerated the Fe3+/ Fe2+ cycle, and the surface polar C-groups promoted the adsorption of phenol molecules; the OVs induced the formation of acidic micro regions and facilitated the dissociation of the O O bonds in H 2 O 2 into OH, extending the application range of pH from ~4.0 to the neutral condition during the Fenton-like process. Unlabelled Image • Dendritic Fe@Fe 3 O 4 /OVs@CQDs were multiscale-designed and green-synthesized. • Abundant CQDs and OVs were formed by the carbonization effect of glucose. • CQDs promote the transform of Fe3+/Fe2+ and attract phenol molecules. • OVs provide acid micro-regions and reduce the activation energy of H 2 O 2 into OH. [ABSTRACT FROM AUTHOR]

A series of EDTA-metal complexes was prepared for the Fenton oxidation catalysts and Fe(II)L exhibits high catalytic performance for degradation of hydroxypropyl guar gum in a wide pH range 7.0-13.0. The viscosity of hydroxypropyl guar gum can be reduced with the 10.0% H2O2 and 5.0% Fe(II)L. The viscosity average molecular weight of hydroxypropyl guar gum was decreased from almost 2 million to 3,199. Most important of all, the chemical oxygen demand (COD) value can be decreased to 104 mg/L from 8,080 mg/L with enough H2O2, and Fe(II)L also shows great catalytic ability in the degradation of various polymers by H2O2. The proposed mechanism of the activation of H2O2 by the complex was studied. [ABSTRACT FROM AUTHOR]

This paper is built on the Fenton-like oxidation of p-hydroxybenzoic acid (p-HBZ) in the presence of H2O2 and 3%Fe supported on CeO2-TiO2 aerogels under mild conditions. These catalysts were deeply characterized by X-ray diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The effect of thermal treatment, pH (2-3, 5, 7), H2O2/p-HBZ molar ratio (5, 15, 20, 25) and reaction temperature (25 °C, 40 °C and 60 °C) on the catalytic properties of supported Fe catalysts are studied. Our results highlight the role of CeO2 and the calcination of the catalyst to obtain the highest catalytic properties after 10 min: 73% of p-HBZ conversion and 52% of total organic carbon (TOC) abatement. [ABSTRACT FROM AUTHOR]