Comparative study of Cu-based bimetallic oxides for Fenton-like degradation of organic pollutants

Nickel-doped red mud-based Prussian blue analogues heterogeneous activation of H2O2 for ciprofloxacin degradation: waste control by waste

Red mud (RM) is a typical bulk solid waste with Fe/Al/Si/Ca-rich characteristics that has been used to prepare various heterogeneous catalysts such as iron-based catalysts and supported catalysts. Prussian blue analogues (PBA) is a low-cost, environmentally friendly, and active site rich iron-based metal organic framework, but its catalytic properties are adversely affected by their easy aggregation. In this study, nickel-doped RM-based PBA (RM-Ni PBA) was synthesized by acid dissolution-coprecipitation method for the degradation of ciprofloxacin (CIP). The characterization showed that RM-Ni PBA was a material with excellent dispersibility, large specific surface area, and abundant active sites. The degradation results showed that the removal efficiency of CIP in the RM-Ni PBA/H2O2 system was 16.63, 1.78, and 1.81 times that of RM, RM-PB, and Ni PBA, respectively. It was found that 1O2 was the main reactive oxygen species (ROS) dominated the degradation process, and its formation was accompanied by the mutual conversion of Ni(II)/Fe(II) and Ni(III)/Fe(III). Notably, the degradation process maintained a satisfactory efficiency over a wide pH range (3-9) and exhibited strong anti-interference ability against impurities such as Cl-, SO42-, and NO3-. The components and contents of RM-Ni PBA remained relatively stable during the degradation process. In addition, the degradation intermediates of CIP were identified, and possible degradation pathways were proposed. This study is expected to provide theoretical basis and technical guidance for the application of RM-based heterogeneous catalyst in the treatment of antibiotic wastewater.

Silk Industry Waste Protein-Derived Sericin Hybrid Nanoflowers for Antibiotics Remediation via Circular Economy

Hybrid protein-copper nanoflowers have emerged as promising materials with diverse applications in biocatalysis, biosensing, and bioremediation. Sericin, a waste biopolymer from the textile industry, has shown potential for fabricating such nanoflowers. However, the influence of the molecular weight of sericin on nanoflower morphology and peroxidase-like activity remains unexplored. This work focused on the self-assembly of nanoflowers using high- and low-molecular-weight (HMW and LMW) silk sericin combined with copper(II) as an inorganic moiety. The peroxidase-like activity of the resulting nanoflowers was evaluated using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydrogen peroxide (H2O2). The findings revealed that high-molecular-weight sericin hybrid nanoflowers (HMW-ShNFs) exhibited significantly higher peroxidase-like activity than low-molecular-weight sericin hybrid nanoflowers (LMW-ShNFs). Furthermore, HMW-ShNFs demonstrated superior reusability and storage stability, thereby enhancing their potential for practical use. This study also explored the application of HMW-ShNF for ciprofloxacin degradation to address the environmental and health hazards posed by this antibiotic in water. The results indicated that HMW-ShNFs facilitated the degradation of ciprofloxacin, achieving a maximum degradation of 33.2 ± 1% at pH 8 and 35 °C after 72 h. Overall, the enhanced peroxidase-like activity and successful application in ciprofloxacin degradation underscore the potential of HMW-ShNFs for a sustainable and ecofriendly remediation process. These findings open avenues for the further exploration and utilization of hybrid nanoflowers in various environmental applications.

The self-designed reactor to achieve efficient degradation of polyvinyl alcohol under high-pressure and high-temperature conditions

A huge amount of polyvinyl alcohol (PVA) fabric is abandoned from nuclear power plants every year, the traditional treatment process will occupy land resources and pollute the environment; therefore, a lot of research has been carried out on the chemical treatment of PVA fabric. Herein, the performance of degradation of polyvinyl alcohol under high-pressure and high-temperature conditions is investigated. The effects of the initial pH value, reaction temperature, molar ratio of H2O2/Fe2+, and H2O2 dosage on PVA degradation were evaluated. In the tested ranges in this work, the degradation of PVA fabric via high-pressure and high-temperature method was optimum at the initial pH value of 4, reaction temperature of 300℃, molar ratio of H2O2/Fe2+ as 10, and H2O2 dosage of 13 g/L. The PVA removal rate and TOC removal rate were 99.99% and 97.36%, respectively. Meanwhile, the high-pressure and high-temperature methods also had a great effect on the removal of Rhodamine-B and Reactive Red X-3B, the removal rates of Rhodamine-B and Reactive Red X-3B were 99.83% and 99.76%, respectively. The reaction mechanism of high-pressure and high-temperature methods was also discussed in this study.

Performance and degradation pathway of florfenicol antibiotic by nitrogen-doped biochar supported zero-valent iron and zero-valent copper: A combined experimental and DFT study

Fluorinated compounds are a class of organic substances resistant to degradation. Although zero-valent iron (Fe0) has a promising reducing capability, it still fails to degrade fluorine-containing antibiotics (i.e., florfenicol) efficiently. In this study, we applied a simple one-pot pyrolytic approach to synthesize nitrogen-doped biochar supported Fe0 and zero-valent copper (Cu0) composite (Fe/Cu@NBC) and investigated its performance on florfenicol removal. The results clearly showed that approximately 91.4% of florfenicol in the deionized water was removed by Fe/Cu@NBC within 8 h. As the reaction time was extended to 15 d, the total degradation rate of florfenicol reached 96.6%, in which the defluorination and dechlorination rates were 73.2% and 82.1%, respectively. Both experimental results and density functional theory calculation suggested that ∙OH and ·O2- triggered β-fluorine elimination, resulting in defluorination prior to dechlorination. This new finding was distinct from previous viewpoints that defluorination was more difficult to occur than dechlorination. Fe/Cu@NBC also had a favorable performance for removal of florfenicol in surface water. This study provides a new insight into the degradation mechanism and pathway of florfenicol removal in the Fe/Cu@NBC system, which can be a promising alternative for remediation of fluorinated organic compounds in the environment.

Enhanced non-radical activation of persulfate with pompon-like NiO microspheres for removing sulfamethoxazole in water

The development of efficient heterogeneous catalyst for non-radical activation of persulfate (PS) is highly desired for removing organic pollutants in water. Herein, four NiO samples were prepared by different methods, and their performance for PS activation was investigated using sulfamethoxazole (SMX) as the target pollutant. The structure, surface chemical state, and redox ability of these samples were measured by various characterization techniques, and the key property affecting PS activation efficiency was explored. The results showed that the degradation of SMX by these samples all followed the non-radical mechanism, and the activated PS was the dominant active species. Among them, pompon-like NiO microspheres exhibited the highest activity due to its large surface area and especially high oxidation ability. Catalyst with high oxidation ability or reducing ability should facilitate the non-radical or radical activation of PS, respectively. SMX was completely removed by pompon-like NiO microspheres within 10 min, and the reaction rate constant was calculated to be 0.4199 min-1. An adsorption-degradation experiment was designed to verify the high stability and oxidation potential of the adsorbed PS on NiO surface. Pompon-like NiO microspheres exhibited good reusability, and its performance was barely affected by water quality, demonstrating its potential application in water treatment.

Core-Shell Hierarchical Fe/Cu Bimetallic Fenton Catalyst with Improved Adsorption and Catalytic Performance for Congo Red Degradation

The preparation of heterogeneous Fenton catalysts with both adsorption and catalytic properties has become an effective strategy for the treatment of refractory organic wastewater. In this work, 4A-Fe@Cu bimetallic Fenton catalysts with a three-dimensional core-shell structure were prepared by a simple, template-free, and surfactant-free methodology and used in the adsorption and degradation of Congo red (CR). The results showed that the open three-dimensional network structure and the positive charge of the surface of the 4A-Fe@Cu catalyst could endow a high adsorption capacity for CR, reaching 432.9 mg/g. The good adsorption property of 4A-Fe@Cu for CR not only did not inactivate the catalytic site on 4A-Fe@Cu but also could promote the contact between CR and the active sites on the catalyst surface and accelerate the degradation process. The 4A-Fe@Cu bimetallic catalyst exhibited higher catalytic activity than monometallic 4A@Cu and/or 4A-Fe catalysts due to low work function value. The effects of different pH, H2O2 dosages, and catalyst dosages on the catalytic performance of 4A-Fe@Cu were explored. In the conditions of 7.2 mM H2O2, 2 g/L 4A-Fe@Cu, and 1 g/L CR solution, the degradation ratio of CR by 4A-Fe@Cu could reach 99.2% at pH 8. This strategy provided guidance to the design of high-performance Fenton-like catalysts with both adsorption and catalysis properties for dye wastewater treatment.

Enhanced •OH generation and pollutants removal by framework Cu doped LaAlO3/Al2O3

Highly dispersed framework Cu⁺/Cu²⁺ containing LaAlO₃/Al₂O₃ (La-Cu-Al) was synthesized by a solid-liquid mixed sol-gel method. Excessive Al₂O₃ was confirmed to be necessary for the formation of LaAlO₃. The NMR, EXAFS, FTIR and element mapping results revealed that Cu⁺/Cu²⁺ preferred to substitute octahedral Al sites and bonded by Cu-O-Al in the lattice of LaAlO₃. Compared to La₂CuO₄, CuAl₂O₄ and other reported Fenton-like catalysts, La-Cu-Al was more efficient to mineralize refractory pollutants at a wide pH range of 4.0-10.0. More single electrons around Cu center and octahedral Cu⁺ were confirmed to be responsible for the effective reduction of H₂O₂ into powerful ^•OH. Moreover, organic pollutants as electron donors could interact with surface Cu to accelerate Cu²⁺/Cu⁺ cycle and affect O-O bond of H₂O₂ on La-Cu-Al surface, further promoting the reduction of H₂O₂ into ^•OH. These processes resulted in the high H₂O₂ utilization and the highly efficient removal of pollutants on La-Cu-Al.

Recent advances in waste-derived functional materials for wastewater remediation

Water pollution is a major concern for public health and a sustainable future. It is urgent to purify wastewater with effective methods to ensure a clean water supply. Most wastewater remediation techniques rely heavily on functional materials, and cost-effective materials are thus highly favorable. Of great environmental and economic significance, developing waste-derived materials for wastewater remediation has undergone explosive growth recently. Herein, the applications of waste (e.g., biowastes, electronic wastes, and industrial wastes)-derived materials for wastewater purification are comprehensively reviewed. Sophisticated strategies for turning wastes into functional materials are firstly summarized, including pyrolysis and combustion, hydrothermal synthesis, sol-gel method, co-precipitation, and ball milling. Moreover, critical experimental parameters within different design strategies are discussed. Afterward, recent applications of waste-derived functional materials in adsorption, photocatalytic degradation, electrochemical treatment, and advanced oxidation processes (AOPs) are analyzed. We mainly focus on the development of efficient functional materials via regulating the internal and external characteristics of waste-derived materials, and the material's property-performance correlation is also emphasized. Finally, the key future perspectives in the field of waste-derived materials-driven water remediation are highlighted.

Fulvic acid degradation in Fenton-like system with bimetallic magnetic carbon aerogel Cu-Fe@CS as catalyst: Response surface optimization, kinetic and mechanism

In this study, Cu-Fe bimetallic magnetic chitosan carbon aerogel catalyst (Cu-Fe@CS) was prepared by the sol-gel method to degrade Fulvic acid (FA) in Fenton-like system. Degradation experiment results showed bimetallic catalyst Cu-Fe@CS can degrade more FA than monometallic catalysts (Cu@CS and Fe@CS) due to the synergistic effect between the copper and iron. Plackett Buiman (PB) design showed that pH and temperature exhibited significant influence on FA degradation. The significant factors were optimized by Central Composite Design (CCD), the results revealed that the maximum FA removal reached 96.59% under the conditions of pH 4.07 and temperature 93.77 °C, the corresponding TOC removal reached 77.7%. The kinetic analysis implied that the reaction followed pseudo-first order kinetic with correlation coefficient (R²) = 0.9939. The Arrhenius fitting analysis revealed that Cu-Fe@CS had a lower activation energy (Ea) than Cu@CS and Fe@CS, meaning that reaction was easier to occur in Fenten-like system with Cu-Fe@CS. Catalyst still remained the higher FA and TOC removals of 96.28% and 77.33% after six runs, respectively. The FA removal was reduced by 65.53% with 12 mmol tertiary butanol (TBA) as scavenger, indicating that •OH played an important role in FA degradation. Finally, the catalytic degradation mechanism was proposed.

Degradation of Tetracycline Hydrochloride by Cu-Doped MIL-101(Fe) Loaded Diatomite Heterogeneous Fenton Catalyst

In this work, the combination of high surface area diatomite with Fe and Cu bimetallic MOF material catalysts (Fe_0.25Cu_0.75(BDC)@DE) were synthesized by traditional solvothermal method, and exhibited efficient degradation performance to tetracycline hydrochloride (TC). The degradation results showed: Within 120 min, about 93% of TC was degraded under the optimal conditions. From the physical–chemical characterization, it can be seen that Fe and Cu play crucial roles in the reduction of Fe³⁺ because of their synergistic effect. The synergistic effect can not only increase the generation of hydroxyl radicals (•OH), but also improve the degradation efficiency of TC. The Lewis acid property of Cu achieved the pH range of reaction system has been expanded, and it made the material degrade well under both neutral and acidic conditions. Loading into diatomite can reduce agglomeration and metal ion leaching, thus the novel catalysts exhibited low metal ion leaching. This catalyst has good structural stability, and less loss of performance after five reaction cycles, and the degradation efficiency of the material still reached 81.8%. High performance liquid chromatography–mass spectrometry was used to analyze the degradation intermediates of TC, it provided a deep insight of the mechanism and degradation pathway of TC by bimetallic MOFs. This allows us to gain a deeper understanding of the catalytic mechanism and degradation pathway of TC degradation by bimetallic MOFS catalysts. This work has not only achieved important progress in developing high-performance catalysts for TC degradation, but has also provided useful information for the development of MOF-based catalysts for rapid environmental remediation.

Antioxidant and Organic Dye Removal Potential of Cu-Ni Bimetallic Nanoparticles Synthesized Using Gazania rigens Extract

Copper-nickel bimetallic nanoparticles (Cu-Ni BNPs) were fabricated using an eco-friendly green method of synthesis. An extract of synthesized Gazania rigens was used for the synthesis of BNPs followed by characterization employing different techniques including UV/Vis spectrophotometer, FTIR, XRD, and SEM. Spectrophotometric studies (UV-Vis and FTIR) confirmed the formation of bimetallic nanoparticles. The SEM studies indicated that the particle size ranged from 50 to 100 nm. Analysis of the BNPs by the XRD technique confirmed the presence of both Cu and Ni crystal structure. The synthesized nanoparticles were then tested for their catalytic potential for photoreduction of methylene blue dye in an aqueous medium and DPPH radical scavenging in a methanol medium. The BNPs were found to be efficient in the reduction of methylene blue dye as well as the scavenging of DPPH free radicals such that the MB dye was completely degraded in just 17 min at the maximum absorption of 660 nm. Therefore, it is concluded that Cu-Ni BNPs can be successfully synthesized using Gazania rigens extract with suitable size and potent catalytic and radical scavenging activities.

Preparation of a Gangue-Based X-type Zeolite Molecular Sieve as a Multiphase Fenton Catalyst and Its Catalytic Performance

In this study, a series of X-type zeolite molecular sieve catalysts, modified with copper (Cu-X), were prepared by an alkali fusion-hydrothermal synthesis using coal gangue from Inner Mongolia. These catalysts were used in the degradation of the methylene blue dye by a Fenton-like reaction. Characterization results showed that Cu is considered to be present in the surface structure of the zeolite in the form of doped Cu ions and metal oxide. It is believed that Cu2+ is the main active site involved in the Fenton reaction. The X-ray photoelectron spectroscopy (XPS) spectra indicated that Cu2+ and Cu+ coexist in the catalysts and participate together in the Fenton reaction. The degradation of methylene blue by the Cu-X catalysts was investigated to determine the optimal catalytic conditions in terms of six aspects: catalyst dosage, initial solution concentration, initial pH of the solution, H2O2 dosage, copper loading, and reaction temperature. The experimental results showed that CX-1.0 had excellent activity and stability for the degradation and decolorization of the methylene blue dye, which could completely degrade the dye within 90 min, and the total organic carbon removal rate reached as high as 97.8%. Electron spin resonance (ESR) and radical capture experiments showed that •OH played a dominant role in the Fenton-like reaction. Combined with XPS, ESR, and catalytic tests, the redox cycle of Cu+/Cu2+ was found to be accelerating the generation of reactive radicals in the Fenton system.

Nanoscale Fe0/Cu0 bimetallic catalysts for Fenton-like oxidation of the mixture of nuclear-grade cationic and anionic exchange resins

Spent resins generated from the nuclear industrial processes are still difficult to be treated and disposed. Fenton-like processes have great application potential in the treatment of spent resins, but the Fenton reaction mechanisms and resin degradation pathways remain challenging. In this study, nanoscale Fe⁰/Cu⁰ bimetallic catalysts were prepared and characterized for the Fenton-like degradation of the mixture of cationic and anionic resins. High catalytic property of Fe⁰/Cu⁰ bimetallic nanoparticles activated by H₂O₂ was evaluated, according to the effects of various nanoparticles, temperature, catalyst amount, H₂O₂ concentration and the mixing ratio of cationic and anionic resins. Combined the shape and color changes of mixed resins with the experimental and calculated characterization results, different degradation difficulty of cationic and anionic resins and their degradation mechanisms were studied. According to the density functional theory calculations of the optimized resin molecules with the Fe⁰/Cu⁰ catalyst, the mechanisms of Fenton-like reactions and the degradation of mixed resins through the synergistic effect of Fe and Cu species were proposed. The comprehensive Fenton-like reactions and degradation mechanisms provide new insights to advance the treatment of spent resins and organic polymers by Fenton-like processes.

Synergistic effect of dual sites on bimetal-organic frameworks for highly efficient peroxide activation

Active site engineering is of significant importance for developing high activity metal-organic frameworks (MOFs) for catalytic applications. Herein, we develop a one-pot strategy to construct bimetal organic frameworks with Fe-Co dual sites for Fenton-like catalysis. Density functional theory (DFT) demonstrated that the introducing Co heteroatoms into MIL-101(Fe) (MIL represents Matérial Institute Lavoisier) was favorable for the formation of electron-deficient centers around benzene rings and electron-rich centers around Fe/Co. This synergistic effect could effectively decrease the energy barrier of H₂O₂ activation. Due to the facilitated charge transfer in the coordinated structures, MIL-101(Fe,Co) with engineered dual sites exhibited exceptionally high efficiency for the degradation of ciprofloxacin (CIP). The reaction rate of MIL-101(Fe,Co)/H₂O₂ system was 0.12 min^-1, which was nearly 7.5 times higher than that of pristine MIL-101(Fe). The reaction mechanism of heterogeneous Fenton-like catalysis was fundamentally investigated by series of in-situ techniques, such as DRIFTS and Raman. ·OH radicals generated by H₂O₂ activation endowed the inspiring ability of MIL-101(Fe,Co) for water decontamination. This work offers a facile principle of exploring MOFs-based Fenton-like catalysts with a wide working pH range for environmental applications.

Three-Dimensional Hierarchical Porous Structures of Metallic Glass/Copper Composite Catalysts by 3D Printing for Efficient Wastewater Treatments

Finding highly efficient and reusable catalysts for advanced oxidation processes is a crucial endeavor to resolve the severe water pollution problems. Although numerous nanocatalysts have been developed in the past few decades, their recyclability along with sustainably high catalytic efficiency still remain challenging. Here, we propose a new strategy for designing efficient and reusable catalysts, that is, introducing Cu as a reductant into a metallic glass-based catalyst and constructing three-dimensional hierarchical porous architectures via a laser 3D printing technique. The as-printed 3D porous MG/Cu catalysts exhibit exceptional catalytic efficiency in degrading RhB with a normalized rate constant approximately 620 times higher than commercial nano zero-valent iron, outperforming most reported Fenton-type catalysts so far. Strikingly, the catalysts exhibit an excellent reusability and can be used more than 100 times (the highest record so far) without apparent efficiency decay. It is revealed that Cu-doping could improve the surface reducibility and promote the electronic transfer, rendering the 3D-printed MG/Cu catalysts with a sustainably active Fe(II)-rich surface and, therefore, unprecedented reusability. This work offers a broadly applicable design route for the development of advanced catalysts with an outstanding combination of activity and reusability for wastewater treatments.

Design and application of metal-organic frameworks and derivatives as heterogeneous Fenton-like catalysts for organic wastewater treatment: A review

Advanced oxidation process (AOP), with a high oxidation efficiency, fast reaction speed (relatively no secondary pollution), has become one of the core technologies of industrial wastewater and advanced drinking water treatment. Heterogeneous Fenton-like oxidation process (HFOP) is a kind of AOP, which developed rapidly in recent years in such a way to overcome the disadvantages of traditional Fenton reaction. Metal-organic frameworks (MOFs) and their derivatives become essential heterogeneous catalysts for organics mineralization due to the large specific surface area, abundant active sites, and ease of structural regulation. However, the knowledge gap on the mechanism and the fate of heterogeneous catalyst species during organics degradation activities by MOFs presents considerable impediments, particularly for a wide application and scaling up the process. This work has the potential to provide guidance and ideas for researchers and engineers in the fields of environmental remediation, environmental catalysis and functional materials. This review focuses on clarifying the critical mechanism of •OH production from MOFs and derivatives as well as its action on the organic's degradation process. The recent developments in MOF based HFOP are compared, and more attention is paid for the following aspects in this review: (1) classifies systematically progressive modification methods of MOFs by chemical and physical treatments; (2) analyzes the fate of catalytic species during treating organic wastewater; (3) proposes design ideas and principles for improving the performance of MOFs catalysts; (4) discusses the main factors influencing the catalytic properties and practical application; (5) summarizes the possible research challenges and directions for MOFs and their derivatives as catalysts applied to wastewater treatment in the future.

Efficient and stable catalysis of hollow Cu9S5 nanospheres in the Fenton-like degradation of organic dyes

The development of new heterogeneous catalysts with stable catalytic activity in a wide pH range to prevent polluting precipitation plays a vital role in large-scale wastewater treatment. Here, a facile anion exchange strategy was designed to fabricate hollow Cu₉S₅ nanospheres by using Cu₂O nanospheres as hard-templates. The structural and compositional transformation from Cu₂O nanospheres to hollow Cu₉S₅ nanospheres were investigated via X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The Fenton-like degradation of organic dyes was used to evaluate the catalytic performance of the obtained Cu-containing catalysts. Results reveal that the hollow Cu₉S₅ nanospheres have the best catalytic activity among five kinds of Cu-containing catalysts. Hollow Cu₉S₅ nanospheres can effectively accelerate the decomposition of H₂O₂ into hydroxyl radicals and superoxide radical, which have been proven to be mainly oxidative species in the Fenton-like degradation of organic pollutants. Hollow Cu₉S₅ nanospheres have a wide pH application range of 5.0-9.0, and their extremely stable activity can be maintained in at least 15 catalytic cycles with a Cu²⁺ ion leaching rate of less than 1.0 %. The outstanding catalytic performance of the Cu₉S₅ catalyst is expected to enhance the practical applications of copper sulfide catalysts in Fenton-like wastewater treatment.

Development of mesh-type Fenton-like Cu/Fex/γ-Al2O3/Al catalysts and application for catalytic degradation of dyes

The application of nanoparticle heterogeneous Fenton-like catalysts is limited due to the requirement of filtration after reaction and possible secondary pollution. In this work, a novel mesh-type monolithic Fenton-like Cu/Fe_x/γ-Al₂O₃/Al catalyst was developed for the degradation of dyes. The Cu and Fe species are uniformly dispersed on the mesh-type anodic monolithic γ-Al₂O₃ supports, and the results of scanning electron microscopy and X-ray diffractometry analysis show that Fe can reduce the particle size of Cu over γ-Al₂O₃. The activity results show that the degradation rate of rhodamine B (RhB) reached 99.5% within 1 h using 4 × 6 cm Cu_12.0/Fe_2.0/γ-Al₂O₃/Al catalyst with 1,200 ppm H₂O₂ at 50 °C. The important role of •OH as a reactive oxidant was confirmed through electron spin-resonance spectroscopy and radical scavenging experiment. The hydrogen temperature programmed reduction suggests the high redox ability of Cu/Fe bimetallic catalyst is beneficial to the production of •OH. The Cu/Fe bimetallic catalyst shows excellent recyclability in a 10-cycle experiment, the degradation rate of RhB was maintained at 98% and the leaching amount of metals was lower than 0.7 mg/L. The mesh-type catalyst will be easily applied for the continuous wastewater treatment because it does not need filtration for recovery.

Hydrochars from pinewood for adsorption and nonradical catalysis of bisphenols

In the present study, hydrochars (HCs) were prepared from pinewood biomass by high-temperature pyrolysis and applied as environmental-friendly adsorbents and catalysts in the removal of bisphenol F (BPF) and bisphenol S (BPS) from water. It was found that the structural oxygen defects on hydrochars not only enhance the specific surface area for adsorption of the bisphenols, but also function as an electron conductor for molecular oxygen activation in nonradical pathways. The hydrochar pyrolyzed at 800 °C (HC-800) showed the superior adsorption and catalytic performances toward BPS and BPF removals in a wide pH range, and the removal efficiencies were hardly inhibited by the coexistent inorganic anions and humic acid. Particularly, the nonradical reaction is the dominated catalytic oxidation process in a H₂O₂-HC-800 system, different from the traditional radical-based process with persistent free radicals on hydrochars derived from low-temperature pyrolysis. This study provides a novel route toward the efficient removal of endocrine disrupting compounds via the synergistic adsorption and nonradical catalysis.

Iron-copper bimetallic metal-organic frameworks for efficient Fenton-like degradation of sulfamethoxazole under mild conditions

Iron and copper bimetallic MOF material (Fe_xCu_1-x(BDC)) as a novel Fenton-like catalyst was prepared by a simple solvothermal method, and its performances were evaluated in the catalytic degradation of sulfamethoxazole (SMX) in the presence of hydrogen peroxide. The results indicated that the Fe_xCu_1-x(BDC)/H₂O₂ system was highly effective for SMX degradation over a wide pH range (4.0-8.6). At initial solution pH of 5.6, the bimetallic Fe_0.75Cu_0.25(BDC) catalyst exhibited a 100% SMX (20 mg L^-1) removal within 120 min, which was superior to the SMX removal efficiency over monometallic Fe(BDC) and Cu(BDC) catalysts. Combined with the physical-chemical characterization, the synergistic effect between Fe and Cu species were responsible for the efficient catalytic activity. Moreover, the Fe_0.75Cu_0.25(BDC) catalyst showed good reusability for SMX degradation. The possible reaction mechanism in Fe_xCu_1-x(BDC)/H₂O₂ system was also tentatively proposed. This work has not only suggested the potential of bimetallic Fe_xCu_1-x(BDC) catalysts in Fenton-like treatment of antibiotics, but also provided useful information to develop MOF-based catalysts for efficient environmental remediation.

Advanced Oxidation Processes for the Removal of Antibiotics from Water. An Overview

In this work, the application of advanced oxidation processes (AOPs) for the removal of antibiotics from water has been reviewed. The present concern about water has been exposed, and the main problems derived from the presence of emerging pollutants have been analyzed. Photolysis processes, ozone-based AOPs including ozonation, O3/UV, O3/H2O2, and O3/H2O2/UV, hydrogen peroxide-based methods (i.e., H2O2/UV, Fenton, Fenton-like, hetero-Fenton, and photo-Fenton), heterogeneous photocatalysis (TiO2/UV and TiO2/H2O2/UV systems), and sonochemical and electrooxidative AOPs have been reviewed. The main challenges and prospects of AOPs, as well as some recommendations for the improvement of AOPs aimed at the removal of antibiotics from wastewaters, are pointed out.

Efficient removal of several estrogens in water by Fe-hydrochar composite and related interactive effect mechanism of H2O2 and iron with persistent free radicals from hydrochar of pinewood

Recently, hydrochar (HC) with existed persistent free radicals (PFRs) has attracted researches' attention for the potential application in heterogeneous Fenton-like reactions, but studies on the interactive effects of H₂O₂, iron, and HC in removal of organic pollutants are still limited. In this paper, magnetic iron (hydr)oxides immobilized hydrochar composite (Fe/HC) derived from hydrothermal carbon (HTC) of pinewood were synthesized and characterized. The interactive effects of H₂O₂, iron, and HC in the removal of several estrogens were systematically investigated to understand the removal performance and related mechanism, especially at a pH range close to natural water environment. Batch experiments results showed that estrogens could be efficiently removed over Fe/HC material under a wide pH range of 4-9. Based on the analysis of electron spin resonance, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, and electrochemical impedance spectroscopy, mechanism study indicated that the carbon-centered PFRs on the surface of hydrochar can act as electron donors, and transfer the electrons on adsorbed O₂ to generate O₂^- rapidly, while the addition of H₂O₂ enhanced the transmission ability of electron to produce OH_(ads) on the material surface. The iron and hydrochar components contributed to the desirable removal of estrogens via the synergistic effect between catalysis and adsorption. This study provides a promising application for the use of Fe/HC materials on remediation of pollution with trace estrogens in water environment.

Different adsorption-degradation behavior of methylene blue and Congo red in nanoceria/H2O2 system under alkaline conditions

The Fenton-like activity of nanoceria has attracted intensive attention for wastewater treatment in recent years. During the Fenton-like reaction, the adsorption of organic pollutants on catalyst surface plays a key role in their degradation. In this work, the adsorption-degradation of methylene blue (MB) and Congo red (CR) in nanoceria/H2O2 system was investigated under alkaline conditions. The MB exhibited weak adsorption on nanoceria surface via electrostatic attraction, while strong Lewis acid-base interactions between CR and cerium ions was observed. Moreover, the adsorption of MB was enhanced in the presence of H2O2 by the formation of surface peroxide species, but an adsorption competition existed between H2O2 and CR. With more Ce3+, CeO2 nanorods could degrade CR efficiently as Fenton-like catalyst. But the degradation of MB catalyzed by ceria was much lower than that of CR in the presence of H2O2.

Enhanced Removal of Veterinary Antibiotic Florfenicol by a Cu-Based Fenton-like Catalyst with Wide pH Adaptability and High Efficiency

The study on the removal of refractory veterinary antibiotic florfenicol (FF) in water is still very limited. In this study, an efficient Fenton-like catalyst was developed by synthesizing a series of Cu-based multi-metal layered double hydroxides (CuNiFeLa-LDHs) to degrade FF in aqueous solution. In the experiments, the screened CuNiFeLa-2-LDH with the molar ratio of La³⁺/(Fe³⁺ + La³⁺) = 0.1 exhibited high catalytic activity, achieving almost complete degradation of 5 mg L^-1 FF under 5 mmol L^-1 H₂O₂ conditions. The mechanisms revealed that the enhanced catalytic performance was ascribed to the existence of Ni which accelerated the electron transfer rate and La which served as a Lewis acidic site to provide more reactive sites in this Cu-dominated Fenton-like reaction, further generating ^•OH, ^•O₂ ^-, and O₂ ¹ as active species to attack pollutants directly. Interestingly, the catalyst showed a wide pH adaptability and little release of copper ions to the solution. The regenerated CuNiFeLa-2-LDH is demonstrated to be a stable and reliable material for florfenicol degradation.