Cu-doped g-C3N4 catalyst with stable Cu0 and Cu+ for enhanced amoxicillin degradation by heterogeneous electro-Fenton process at neutral pH

Confinement Synthesis of Atomic Copper-Anchored Polymeric Carbon Nitride in Crystalline UiO-66-NH2 for High-Performance CO2-to-CH3OH Photocatalysis

Photocatalytic CO2 reduction to value-added fuels displays an attractive scenario to enhance energy supply and reduce global warming. We report herein the confinement synthesis of polymeric carbon nitride (PCN) incorporating with Cu single atoms (CuSAs) inside the crystalline UiO-66-NH2, which combines the merits of heterojunction photocatalysis and single-atom catalysis (SAC) to achieve high-performance CO2-to-CH3OH conversion. A series of spectral studies displays the formation of CuSAs@PCN inside the crystalline UiO-66-NH2. Remarkably, the ternary composite shows an excellent photocatalytic turnover frequency of 4.15 mmol ⋅ h-1 ⋅ g-1 for CO2-to-CH3OH conversion. Theoretical and experimental studies demonstrate the doping of CuSAs, as well as the formation of type-II heterojunction, are causal factors to achieve CH3OH generation. The study provides new insights designing high-performance photocatalyst for CO2 conversion to fuels at atomic scale.

The synergistic effect of adsorption and Fenton oxidation for organic pollutants in water remediation: an overview

Water pollution from industrial sources presents a significant environmental challenge due to the presence of recalcitrant organic contaminants. These pollutants threaten human health and necessitate effective remediation strategies. This article reviewed the synergistic application of adsorption and Fenton oxidation for water treatment. Adsorption, a common technique, concentrates pollutants onto a solid surface, but offers limited degradation. Fenton oxidation, an advanced oxidation process (AOP), utilizes hydroxyl radicals for efficient organic compound breakdown. When adsorption and Fenton oxidation combine, adsorption pre-concentrates pollutants, boosting Fenton oxidation effectiveness. This review delves into the mechanisms and advantages of this integrated approach, highlighting its potential for enhanced removal of organic contaminants. The discussion encompasses the mechanisms of Fenton oxidation and the synergistic effects it has with adsorption. Additionally, various support materials employed in this combined process are explored, including carbon-based supports (activated carbon, graphene, carbon nanotubes and biochar), metal-organic frameworks (MOFs), and clays. Finally, the applicability of this approach to diverse wastewater streams, such as medical and industrial wastewater, is addressed. The review contains 105 references and summarizes the key findings and future perspectives for this promising water remediation technology.

Enhancing the photocatalytic efficiency of g-C3N4 for ciprofloxacin degradation using Tetrakis (acetonitrile) copper(I) hexafluorophosphate as a highly effective cocatalyst

Ciprofloxacin antibiotic (CP) is one of the antibiotics with broad-spectrum antimicrobial activity that has the highest rate of antibiotic resistance. This antibiotic undergoes incomplete metabolism within the human body and is excreted into the water, resulting in its hazardous biological and ecotoxicological effects. In this study, a novel photocatalyst, comprised of graphitic carbon nitride (g-CN) and Tetrakis(acetonitrile)copper(I)hexafluorophosphate ([(CH3CN)4Cu]PF6), denoted as CuPF6/g-CN, was employed for the degradation of ciprofloxacin under visible-light irradiation. The Cu complex, functioning as a co-catalyst, assumes a crucial role in facilitating the efficient separation of photogenerated charges and exhibiting high absorption in the visible-light region. More surprisingly, CuPF6/g-CN does surpass by up to 6 times the behavior reached with bare g-CN. The experimental findings indicated that the optimal degradation of ciprofloxacin (CP) occurred after 50 min when using a concentration of 20 mg L-1 CP and a concentration of 0.05 g/L CuPF6/g-CN, under a pH of 8. This research offers valuable insights into the advancement of cost-effective co-catalysts that enhance the photocatalytic capabilities of established photocatalysts. It contributes to improving the overall performance and efficiency of these photocatalytic systems.

Electro-Fenton degradation of pefloxacin using MOFs derived Cu, N co-doped carbon as a nanocomposite catalyst

Electro-Fenton (EF) can in-situ produce H2O2 and effectively activate H2O2 to generate powerful reactive species for the destruction of contaminants under acidic conditions, however, the production of iron-containing sludge and requirement of low working pH significantly hinder its practical application. Herein, a novel Cu, N co-doped carbon (Cu-N@C) with metal organic framework (MOF) as a precursor was constructed and adopted for the elimination of pefloxacin (PEF) in the heterogeneous electro-Fenton (HEF) process. PEF could be almost completely removed within 1 h and total organic carbon (TOC) removal efficiency was 48.57% within 6 h. Meanwhile, Cu-N@C had good repeatability and environmental adaptability, it can still maintain excellent catalytic performance after 10 cycles, and it exhibited satisfactory remediation performance in simulated water matrix. In addition, the HEF process catalyzed by Cu-N@C also showed satisfactory degradation effect on other organic pollutants including atrazine, methylene blue, and chlorotetracycline. Under the action of impressed current, the HEF system could generate H2O2 in-situ, and the active species could be generated in the redox cycle of Cu0/Cu1+/Cu2+. Electron paramagnetic resonance and quenching experiments confirmed that •OH was the dominant active species in the degradation of organic compounds. The degradation process of PEF was studied by mass spectrometry analysis of intermediate products. This study provided a simple method to prepare MOF-based electrocatalyst, which exhibits promising application potential for treatment wastewater.

Enhanced Fenton-like catalysis via interfacial regulation of g-C3N4 for efficient aromatic organic pollutant degradation

For the efficient degradation of organic pollutants with the goal of reducing the water environment pollution, we employed an alkaline hydrothermal treatment on primeval g-C3N4 to synthesize a hydroxyl-grafted g-C3N4 (CN-0.5) material, from which we engineered a novel Fenton-like catalyst, known as Cu-CN-0.5. The introduction of numerous hydroxyl functional groups allowed the CN-0.5 substrate to stably fix active copper oxide particles through surface complexation, resulting in a low Cu leaching rate during a Cu-CN-0.5 Fenton-like process. A sequence of characterization techniques and theoretical calculations uncovered that interfacial complexation induced charge redistribution on the Cu-CN-0.5 surface. Specifically, some of the π electrons in the tris-s-triazine units were transferred to the copper oxide particles along the newly formed chemical bonds (C(π)-O-Cu), forming a π-deficient area on the tris-s-triazine plane near the complexation site. In a typical Cu-CN-0.5 Fenton-like process, a stable π-π interaction was established due to the favorable positive-negative match of electrostatic potential between the aromatic pollutants and π-deficient areas, leading to a significant improvement in Cu-CN-0.5's adsorption capacity for aromatic pollutants. Furthermore, pollutants also delivered electrons to the Cu-CN-0.5 Fenton-like system via a "through-space" approach, which suppressed the futile oxidation of H2O2 in reducing the high-valent Cu2+ and significantly improved the generation efficiency of •OH with high oxidative capacity. As expected, Cu-CN-0.5 not only exhibited an efficient Fenton degradation for several typical aromatic organic pollutants, but also demonstrated both a low metal leaching rate (0.12 mg/L) and a H2O2 utilization rate exceeding 80%. The distinctive Fenton degradation mechanism substantiated the potential of the as-prepared material for effective wastewater treatment applications.

Liquid- liquid (Cyclohexanone: Cyclohexanol) separation using augmented tight nanofiltration membrane: A sustainable approach

Organic solvent nanofiltration (OSN) is an incipient technology in the field of organic liquid-liquid separation. The incomplete separations and complexity involved in these, forces many organic liquids to be released as effluents and the adverse effects of these on environment is enormous and irreparable. The work prominences on the complete separation of industrially significant cyclohexanone: cyclohexanol (keto-alcohol oil) and heptane: toluene mixtures. The separations of these above-mentioned organic liquid mixtures were carried out using the fabricated Lewis acid modified graphitic carbon nitride (Cu2O@g-C3N4) incorporated polyvinylidene difluoride (PVDF) composite membranes. These fabricated membranes showed a separation factor of 18.16 and flux of 1.62 Lm-2h-1 for cyclohexanone: cyclohexanol mixture and separation of heptane and toluene mixture (with heptane flux of 1.52 Lm-2h-1) showed a separation factor of 9.9. The selectivity and productivity are based on the polarity and size of the organic liquids. The role of Cu2O@g-C3N4 is influencing the pore size distribution, increased divergence from solubility parameters, polarity, solvent uptake and porosity of the composite membranes. The developed composite membranes are thus envisioned to be apt for a wide range of liquid-liquid separations due to its implicit nature.

A review of copper-based Fenton reactions for the removal of organic pollutants from wastewater over the last decade: different reaction systems

In recent years, as global industrialization has intensified, environmental pollution has become an increasingly serious problem. Improving water quality and achieving wastewater purification remain top priorities for environmental health initiatives. The Fenton process is favored by researchers due to its high efficiency and ease of operation. Central to the Fenton process is a catalyst used to activate hydrogen peroxide, rapidly degrading pollutants, improving water quality. Among various catalysts developed, copper-based catalysts have attracted considerable attention due to their affordability, high activity, and stable performance. Based on this, this paper reviews the development of copper-based Fenton systems over the past decade. It mainly involves the research and application of copper-based catalysts in different Fenton systems, including photo-Fenton, electro-Fenton, microwave-Fenton, and ultrasonic-Fenton. This review provides a fundamental reference for the subsequent studies of copper-based Fenton systems, contributing to the goal of transitioning these systems from laboratory research into practical environmental applications.

Electrocatalysis coupled heterogeneous electro-Fenton like treatment of coal gasification wastewater using tourmaline as catalyst: process parameters and response surface

Coal gasification technology is essential for realizing clean and efficient conversion of coal, as well as for reducing carbon emissions. However, coal gasification technology is accompanied by a large amount of coal gasification wastewater that is biodegradable. In this work, tourmaline was applied as a catalyst in electro-Fenton like process for treating coal gasification wastewater. The optimal applied parameters of coal gasification wastewater were investigated as follows: current density of 90 mA cm-2, tourmaline dosage of 8 g L-1, electrode gap of 1 cm, and temperature at 25 °C; the COD removal ratio reached 91.24% after 240-min treatment. In addition, the current density and tourmaline dosage were further optimized by response surface method. The result was about current density with 82.4 mA cm-2 and catalyst with 7.57 g L-1; the predicted COD removal efficiency was 86.91%. Under the optimal parameters the actual COD removal efficiency was 88.25% a little high than the predicted value. To explore the reusability of tourmaline as Fenton reaction catalyst, five cycles of experiments were carried out. The result demonstrated that tourmaline could be used as catalyst for treating coal gasification wastewater by electro-Fenton like process.

Unveiling the metallic size effect on O2 adsorption and activation for enhanced electro-Fenton degradation of aromatic compounds

Metal-atom-modified nitrogen-doped carbon materials (M-N-C) have emerged as promising candidates for electro-Fenton degradation of pollutants. Nonetheless, a comprehensive exploration of size-dependent M-N-C catalysts in the electro-Fenton process remains limited, posing challenges in designing surface-anchored metal species with precise sizes. Herein, a heterogeneous-homogeneous coupled electro-Fenton (HHC-EF) system was designed and various M-N-C catalysts anchored with Co single atoms (CoSA-N-C), Co clusters (CoAC-N-C), and Co nanoparticles (CoNP-N-C) were successfully synthesized and employed in an HHC-EF system. Intriguingly, CoAC-N-C achieved outstanding removal efficiencies of 99.9% for BPA and RhB within 10 and 15 min, respectively, with the fastest reaction kinetics (0.70 min-1 for BPA and 0.34 min-1 for RhB). Electron spin resonance and trapping experiments revealed that·OH played a crucial role in the HHC-EF process. Moreover, experiments and theoretical calculations revealed that the unique metallic size effect facilitate the in-situ electro-generation of H2O2. Specifically, the atomic interaction between neighboring Co atoms in clusters enhanced O2 adsorption and activation by strengthening the Co-N bond and transforming O2 adsorption configuration to the Yeager-type. This study provides valuable insights that could inspire the size-oriented metal-based catalyst design from the perspective of the potential atomic distance effect.

Ferrocenylselenoether and its cuprous cluster modified TiO2 as visible-light photocatalyst for the synergistic transformation of N-cyclic organics and Cr(vi)

In this study, fcSe@TiO2 and [Cu2I2(fcSe)2]n@TiO2 nanosystems based on ferrocenylselenoether and its cuprous cluster were developed and characterized by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX), and electron paramagnetic resonance (EPR). Under optimized conditions, 0.2 g L-1 catalyst, 20 mM H2O2, and initial pH 7, good synergistic visible light photocatalytic tetracycline degradation and Cr(vi) reduction were achieved, with 92.1% of tetracycline and 64.5% of Cr(vi) removal efficiency within 30 minutes. Mechanistic studies revealed that the reactive species ˙OH, ˙O2-, and h+ were produced in both systems through the mutual promotion of Fenton reactions and photogenerated charge separation. The [Cu2I2(fcSe)2]n@TiO2 system additionally produced 1O2 from Cu+ and ˙O2-. The advantages of the developed nanosystems include an acidic surface microenvironment provided by Se⋯H+, resourceful product formation, tolerance of complex environments, and excellent adaptability in refractory N-cyclic organics.

Ecotoxicology Evaluation of a Fenton-Type Process Catalyzed with Lamellar Structures Impregnated with Fe or Cu for the Removal of Amoxicillin and Glyphosate

Antibiotics and pesticides, as well as various emerging contaminants that are present in surface waters, raise significant environmental concerns. Advanced oxidation processes, which are employed to eliminate these substances, have demonstrated remarkable effectiveness. However, during the degradation process, by-products that are not completely mineralized are generated, posing a substantial risk to aquatic ecosystem organisms; therefore, it is crucial to assess effluent ecotoxicity following treatment. This study aimed to assess the toxicity of effluents produced during the removal of amoxicillin and glyphosate with a Fenton-type process using a laminar structure catalyzed with iron (Fe) and copper (Cu). The evaluation included the use of Daphnia magna, Selenastrum capricornutum, and Lactuca sativa, and mutagenicity testing was performed using strains TA98 and TA100 of Salmonella typhimurium. Both treated and untreated effluents exhibited inhibitory effects on root growth in L. sativa, even at low concentrations ranging from 1% to 10% v/v. Similarly, negative impacts on the growth of algal cells of S. capricornutum were observed at concentrations as low as 0.025% v/v, particularly in cases involving amoxicillin-copper (Cu) and glyphosate with copper (Cu) and iron (Fe). Notably, in the case of D. magna, mortality was noticeable even at concentrations of 10% v/v. Additionally, the treatment of amoxicillin with double-layer hydroxides of Fe and Cu resulted in mutagenicity (IM ≥ 2.0), highlighting the necessity to treat the effluent further from the advanced oxidation process to reduce ecological risks.

Electrooxidation of amoxicillin in aqueous solution with graphite electrodes: Optimization of degradation and deciphering of byproducts using HRMS

Contaminants of emerging concern (CECs) such as antibiotics have become a matter of worry in aquatic environments worldwide. Their presence in the environment has been increasing due to the inability of conventional wastewater and water treatments to annihilate them. Hence, attempts have been made to remove CECs using electrochemical oxidation (EO). Present study employed the low cost, active carbon based graphite sheet electrodes as anode and cathode to oxidize and degrade Amoxicillin (AMOX)- a β-lactum thiazolidine antibiotic. Optimization studies found pH 9, 45 mA cm-2, 81 cm2 electrode surface area, 6 mM electrolyte concentration and 60 min treatment time to be optimal for AMOX removal. Studies with varying concentrations of AMOX (20 mg L-1, 30 mg L-1 and 40 mg L-1) found that increase in concentrations of AMOX require higher current densities and treatment time for better TOC removal. High performance liquid chromatography photo diode array (HPLC-PDA) studies found 94% removal for 40 mg L-1 of AMOX at optimal conditions with 90% COD and 46% TOC removal. High resolution mass spectrometry (HRMS) studies using Ultra performance liquid chromatography-quadrupole time of flight-mass spectrometry (UPLC-Q-ToF-MS) identified major degradation mechanisms to be hydroxylation, β-lactum ring cleavage, breakage of thiazolidine ring chain from the aromatic ring and piperazinyl ring formation. The final byproducts of AMOX oxidation were carboxylic acids.

Synthesis of solar-driven Cu-doped graphitic carbon nitride photocatalyst for enhanced removal of caffeine in wastewater

Caffeine (CaF), a widely consumed compound, has been associated with various harmful effects on human health, including metabolic, cardiovascular disease, and reproductive disorders. Moreover, it poses a signifincant threat to organisms and aquatic ecosystems, leading to water pollution concerns. Therefore, the removal of CaF from wastewater is crucial for mitigating water pollution and minimizing its detrimental impacts on both humans and the environment. In this study, a solar-driven Cu-doped graphitic carbon nitride (Cu/CN) photocatalyst was synthesized and evaluated for its effectiveness in oxidizing CaF in wastewater. The Cu/CN photocatalyst, with a low band gap energy of 2.58eV, exhibited superior performance in degrading CaF compared to pure graphitic carbon nitride (CN). Under solar light irradiation, CuCN achieved a remarkable CaF degradation efficiency of 98.7% CaF, surpassing CN's efficiency of 74.5% by 24.2%. The synthesized Cu/CN photocatalyst demonstrated excellent removal capability, achieving a removal rate of over 88% for CaF in wastewater. Moreover, the reusability test showed that Cu/CN could be successfully reused up to five cycles maintaining a high removal efficiency of 74% for CaF in the fifth cycle. Additionally, the study elucidated the oxidation mechanism of CaF using solar-driven Cu/CN photocatalyst and highlighted the environmental implications of the process.

Controllable synthesis of copper-organic frameworks via ligand adjustment for enhanced photo-Fenton-like catalysis

The efficient heterogeneous photo-Fenton-like catalysts based on two secondary ligand-induced Cu(II) metal-organic frameworks (Cu-MOF-1 and Cu-MOF-2) were constructed for the first time and investigated for the degradation of multiple antibiotics. Herein, two novel Cu-MOFs were prepared using mixed ligands by a facile hydrothermal method. The one-dimensional (1D) nanotube-like structure could be obtained by using V-shaped, long and rigid 4,4'-bis(3-pyridylformamide)diphenylether (3-padpe) ligand in Cu-MOF-1, while polynuclear Cu cluster could be prepared more easily by using short and small isonicotinic acid (HIA) ligand in Cu-MOF-2. Their photocatalytic performances were measured by degradation of multiple antibiotics in Fenton-like system. Comparatively, Cu-MOF-2 exhibited superior photo-Fenton-like performance under visible light irradiation. The outstanding catalytic performance of Cu-MOF-2 was ascribed to the tetranuclear Cu cluster configuration and excellent ability of photoinduced charge transfer and hole separation thus improved the photo-Fenton activity. In addition, Cu-MOF-2 showed high photo-Fenton activity in wide pH working range 3-10 and maintained wonderful stability after five cyclic experiments. The degradation intermediates and pathways were deeply studied. The main active species h⁺, O₂^- and OH worked together in photo-Fenton-like system and possible degradation mechanism was proposed. This study provided a new approach to design the Cu-based MOFs Fenton-like catalysts.

Flow-through heterogeneous electro-Fenton system using a bifunctional FeOCl/carbon cloth/activated carbon fiber cathode for efficient degradation of trimethoprim at neutral pH

The synthesis of multifunctional cathode with high-efficiency and stable catalytic activity for simultaneously producing and activating H₂O₂ is an effective way for promoting the performance of heterogeneous electro-Fenton process (HEF). In addition, accelerating mass transfer by adopting a flow-through reactor is also great importance because of its better utilization of catalysts and adequate contact of the contaminant with the oxidants generated on the electrode surface. Herein, a novel flow-through HEF (FHEF) system was designed for the degradation of trimethoprim (TMP) using bifunctional cathode with a sandwich structure FeOCl nanosheets loaded onto carbon cloth (CC) and activated carbon fiber (ACF) (FeOCl/CC/ACF). The cathode exhibited excellent performance in activating H₂O₂ for the in-situ generation of hydroxyl radicals (^•OH). The electron spin resonance (ESR) measurements and radical quenching tests proved that the high production of ^•OH in the FHEF process was favorable to the high catalytic efficiency. 25 mg L^-1 TMP was entirely degraded after 60 min, with the TOC removal of 62.6% (180 min) at pH 6.8, 9.0 mA cm^-2, and flux rate 210 mL min^-1. Moreover, the degradation rate still could reach 83% (60 min) after 10 cycles without obvious valence and crystal phase changes. Simultaneously, the current utilization rate has also been greatly enhanced, with an average current efficiency of 69.9% and a low energy consumption of 0.28 kWh kg^-1. The reasonable degradation pathways for TMP were proposed based on the UPLC-QTOF-MS/MS results. Finally, the results of toxicological simulation showed a declining trend in the toxicity of the samples during TMP degradation. These results claim that the FeOCl/CC/ACF-FHEF system is an efficient and economical technology for the treatment of organic contaminants in effluents.

The application of a new recyclable photocatalyst γ-Fe2O3@SiO2@ZIF8-Ag in the photocatalytic degradation of amoxicillin in aqueous solutions

This pilot study synthesized the γ-Fe₂O₃@SiO₂@ZIF8-Ag nanocomposites via the hydrothermal method to study its potential use in amoxicillin degradation as a novel photocatalyst in aqueous solutions under visible light radiation. Various diagnostic methods were used to determine the morphology and functional structure of the photocatalyst, and the results confirmed its proper formation. Complete degradation of AMX was obtained at a pH of 5, catalyst dosage of 0.4 g/L, AMX concentration of 10 mg/L, and reaction time of 60 min. The efficiency of the degradation was diminished when anions were present in the reaction medium, and the order of their effect was SO₄^2- < Cl^- < NO₃^- < HCO₃^-. Biodegradability (BOD₅/COD ratio) increased from 0.20 to 0.68 after 120 min of photocatalytic treatment, with a COD removal of 87.54% and a TOC removal of 74.88%. Through the experimental trapping of electrons, we found the production of reactive species, such as hydroxyl radical (•OH), superoxide (O₂^•-), and holes (h⁺), in the photocatalysis reactor and that •OH was the predominant species in AMX photodegradation. Comparative experiments emphasized that the oxidation process occurs with the adsorption of pollutants on the surface of the catalyst, and the photocatalyst has the potential to be activated by various light sources, including visible light, UV light, and sunlight, with an AMX decomposition above 88%. The synthesized particles can be recovered after five consecutive cycles with minimal reduction in the degradation rate (< 4%). γ-Fe₂O₃@SiO₂@ZIF8-Ag can be considered a promising photocatalyst for use in AMX degradation due to its recyclability, easier activation by different light sources, and excellent mineralization.

Boosting electron transport process over multiple channels induced by S-doped carbon and Fe7S8 NPs interface toward high-efficiency antibiotics removal

The enhancement of electron transport process on multiple channels of C-Fe and C-S-Fe bonds between dual-reaction centres was investigated for stimulating the antibiotics degradation in Fenton-like processes. Herein, multiple channels structure of sulfur-doped carbon coupled Fe₇S₈ cluster through C-Fe bond and C-S-Fe bond was constructed through density functional theory (DFT), and S-doped carbon framework coated Fe₇S₈ nanoparticles (Fe₇S₈/SC) Fenton-like catalyst was prepared through hydrothermal and subsequent sulfuration process. The DFT calculations revealed that electrons are thermodynamically transferred from carbon to iron along both C-Fe and C-S-Fe bonds. The optimized Fe₇S₈/SC catalyst exhibited desirable catalytic property for Fenton-like degradation for various antibiotics, the removal of amoxicillin, norfloxacin, and tetracycline hydrochloride reach 98.9%, 97.8%, and 99.3% respectively within 40 min under neutral pH, and catalyst also demonstrated excellent cycle stability after five runs. The excellent degradation effect of antibiotics by Fenton-like catalyst was attributed to the intensified electron transport process by multiple electron transfer channels between dual reaction centres, making Fe^II easier to regenerate. This study spreads a new route for the enhancement of electron transport process in Fenton-like catalysts by constructing multiple channels.

Degradation of lomefloxacin by MoS2/MIL-53(Fe, Cu) catalyst in heterogeneous electro-Fenton process

A novel heterogeneous catalyst named MoS₂/MIL-53(Fe, Cu) (MMFC) was prepared by hydrothermal method and applied in a heterogeneous electro-Fenton (hetero-EF) system for lomefloxacin (LOM) degradation in this work. Under the optimal conditions of current density 3 mA/cm², catalyst dosage 0.100 g/L, and initial pH 6, 93.5% LOM (2 mg/L) removal efficiency was achieved in the MMFC hetero-EF system within 60 min, indicating an obvious improvement compared with the MIL-53(Fe, Cu) hetero-EF system. The good catalytic activity was attributed to more effective active sites of the catalyst and the conversion of Fe(II)/Fe(III) and Cu(I)/Cu(II) promoted by Mo(IV) in MoS₂, which could be inferred by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) characterizations. The reusability and stability of MMFC were explored based on five cyclic experiments, and the average degradation efficiency reached 73.9%. Furthermore, the hetero-EF system could achieve the total removal of moxifloxacin and tetracycline within 6 min and 40 min, respectively. Quenching experiments revealed that the hydroxyl radicals (·OH) were the main reactive radicals while superoxide radicals (·O₂^-) and singlet oxygen (¹O₂) played a certain part in LOM degradation. Finally, the possible mechanism of the hetero-EF process and LOM degradation pathways were proposed, including substitution, elimination, and cleavage of ring structures. Accounting for good catalytic performance, low preparation cost, and satisfactory versatility, the MMFC exhibited good potential to work as a hetero-EF catalyst for wastewater treatment.

Novel catalysts with multivalence copper for organic pollutants removal from wastewater with excellent selectivity and stability in Fenton-like process under neutral pH conditions

Fenton-like reaction has been widely used for organics degradation. However, most Fenton-like reaction works at low pH range (pH < 4) with uncontrollable selectivity of hydroxyl radicals from H₂ O₂ activation, and unsatisfied catalyst stability, which is compromised advanced oxidation performance for water/wastewater treatments. In this work, to solve the drawbacks, novel copper catalysts were fabricated via hydrogen reduction/calcination of Cu²⁺ -supported Al/MCM-41 with precisely controllable copper valence state. Compared with catalysts with monovalence copper (i.e., CuO, Cu, and Cu²⁺ ), the obtained catalysts with multivalence copper present higher selectivity, excellent stability towards •OH radical pathways, and outperformance in pCBA degradation efficiency at neutral state. In addition, the fabricated catalysts also exhibited excellent phenol removal efficiency (75.5%) and H₂ O₂ utilization efficiency (47.9%) within neutral environment. Moreover, the degradation efficiency of phenol approaches to 100% within only 2 h. The catalyst also shows good stability for organic pollutants removal, which shows good potential in catalytic oxidation for phenolic compounds-containing wastewater in Fenton-like reaction, especially under neutral pH conditions. PRACTITIONER POINTS: Multivalence copper presents great potentials for organic compounds removal at neutral condition. Multivalence copper shows higher selectivity toward •OH and good stability at neutral condition. Multivalence copper exhibiters outperformed phenol removal efficiency at neutral condition.

A review of radical and non-radical degradation of amoxicillin by using different oxidation process systems

Pharmaceutical compounds have piqued the interest of researchers due to an increase in their demand, which increases the possibility of leakage into the environment. Amoxicillin (AMX) is a penicillin derivative used for the treatment of infections caused by gram-positive bacteria. AMX has a low metabolic rate in the human body, and around 80-90% is unmetabolized. As a result, AMX residuals should be treated immediately to avoid further accumulation in the environment. Advanced oxidation process techniques are an efficient way to degrade AMX. This review attempts to collect, organize, summarize, and analyze the most up to date research linked to the degradation of AMX by different advanced oxidation process systems including photocatalytic, ultrasonic, electro-oxidation, and advanced oxidation process-based on partials. The main topics investigated in this review are degradation mechanism, degradation efficiency, catalyst stability, the formation of AMX by-products and its toxicity, in addition, the influence of different experimental conditions was discussed such as pH, temperature, scavengers, the concentration of amoxicillin, oxidants, catalyst, and doping ratio. The degradation of AMX could be inhibited by very high values of pH, temperature, AMX concentration, oxidants concentration, catalyst concentration, and doping ratio. Several AMX by-products were discovered after oxidation treatment, and several of them had lower or same values of LC₅₀ (96 h) fathead minnow of AMX itself, such as m/z 384, 375, 349, 323, 324, 321, 318, with prediction values of 0.70, 1.10, 1.10 0.42, 0.42, 0.42, and 0.42 mg/L, respectively. We revealed that there is no silver bullet system to oxidize AMX from an aqueous medium. However, it is recommended to apply hybrid systems such as Photo-electro, Photo-Fenton, Electro-Fenton, etc. Hybrid systems are capable to cover the drawbacks of the single system. This review may provide important information, as well as future recommendations, for future researchers interested in treating AMX using various AOP systems, allowing them to improve the applicability of their systems and successfully oxidize AMX from an aqueous medium.

Efficient degradation of semi-coking wastewater in three-dimensional electro-Fenton by CuFe2O4 heterocatalyst

Semi-coking wastewater contains a rich source of toxic and refractory compounds. Three-dimensional electro-Fenton (3D/EF) process used CuFe₂O₄ as heterocatalyst and activated carbon (AC) as particle electrode was constructed for degrading semi-coking wastewater greenly and efficiently. CuFe₂O₄ nanoparticles were prepared by coprecipitation method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy disperse spectroscopy (EDS). Factors like dosage of CuFe₂O₄, applied voltage, dosage of AC and pH, which effect COD removal rate of semi-coking waste water were studied. The results showed that COD removal rate reached to 80.9% by 3D/EF process at the optimum condition: 4 V, 0.3 g of CuFe₂O₄, 1 g of AC and pH = 3. Trapping experiment suggesting that hydroxyl radical (•OH) is the main active radical. The surface composition and chemical states of the fresh and used CuFe₂O₄ were analyzed by XPS indicating that Fe, Cu, and O species are involved into the 3D/EF process. Additionally, anode oxidation and the adsorption and catalysis of AC are also contributed to the bleaching of semi-coking waste water. The possible mechanisms of 3D/EF for degrading semi-coking waste water by CuFe₂O₄ heterocatalyst were proposed.

Degradation of amoxicillin by newly isolated Bosea sp. Ads-6

Amoxicillin (AMX), one of the micro-amount hazardous pollutants, was frequently detected in environments, and of great risks to environments and human health. Microbial degradation is a promising method to eliminate pollutants. In this study, an efficient AMX-degrading strain, Ads-6, was isolated and characterized. Strain Ads-6, belonging to the genus Bosea, was also able to grow on AMX as the sole carbon and nitrogen source, with a removal of ~60% TOC. Ads-6 exhibited strong AMX-degrading ability at initial concentrations of 0.5-2 mM and pH 6-8. Addition of yeast extract could significantly enhance its degrading ability. Many degradation intermediates were identified by HPLC-MS, including new ones such as two phosphorylated products which were firstly defined in AMX degradation. A new AMX degradation pathway was proposed accordingly. Moreover, the results of comparative transcriptomes and proteomes revealed that β-lactamase, L, D-transpeptidase or its homologous enzymes were responsible for the initial degradation of AMX. Protocatechuate branch of the beta-ketoadipate pathway was confirmed as the downstream degradation pathway. These results in the study suggested that Ads-6 is great potential in biodegradation of antibiotics as well as in the bioremediation of contaminated environments.

Enhanced Fenton-like process via interfacial electron donating of pollutants over in situ Cobalt-doped graphitic carbon nitride

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 (H₂O₂) or other energy. Herein, we report a novel Co-based Fenton-like catalyst (in-situ-Co-g-C₃N₄) synthesized via the surface complexation method, in which Co species were modified in situ into the framework of the graphitic carbon nitride (g-C₃N₄) substrate through C-O-Co chemical bonding. The catalyst exhibited higher Fenton-like catalytic activity than pure g-C₃N₄ 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-C₃N₄ than that of g-C₃N₄. Density functional theory (DFT) calculations and a series of experimental and characterization analyses revealed the interfacial reaction mechanism between H₂O₂, pollutants and in-situ-Co-g-C₃N₄. During the Fenton-like reaction, the electron-poor C center on the aromatic ring of g-C₃N₄ could capture the electrons deprived from pollutants, and subsequently deliver them to around the electron-rich Co center to efficiently reduce H₂O₂ to hydroxyl radicals (^•OH), enabling H₂O₂ 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.