Visible-light-assisted peroxymonosulfate activation by metal-free bifunctional oxygen-doped graphitic carbon nitride for enhanced degradation of imidacloprid: Role of non-photochemical and photocatalytic activation pathway

Insight of neonicotinoid insecticides: Exploring exposure, mechanisms in non-target organisms, and removal technologies

Neonicotinoid insecticides (NEOs) have garnered global attention due to their selective toxicity to insects and minimal impact on mammals. However, growing concerns about their extensive use and potential adverse effects on the ecological environment and non-target organisms necessitate further investigation. This study utilized bibliometric tools to analyze Web of Science data from 2003 to 2024, elucidating the current research landscape, identifying key research areas, and forecasting future trends related to NEOs. This paper provides an in-depth analysis of NEO exposure in non-target organisms, including risk assessments for various samples and maximum residue limits established by different countries. Additionally, it examines the impacts and mechanisms of NEOs on non-target organisms. Finally, it reviews the current methods for NEO removal and degradation. This comprehensive analysis provides valuable insights for regulating NEO usage and addressing associated exposure challenges.

Oxidation of imidacloprid insecticide through PMS activation using CuFe2O4 nanoparticles: Role of process parameters and surface modifications

The contamination of water bodies by synthetic organic compounds coupled with climate change and the growing demand for water supply calls for new approaches to water management and treatment. To tackle the decontamination issue, the activation of peroxymonosulfate (PMS) using copper magnetic ferrite (CuMF) nanoparticles prepared under distinct synthesis conditions was assessed to oxidize imidacloprid (IMD) insecticide. After optimization of some operational variables, such as CuMF load (62.5-250 mg L-1), PMS concentration (250-1000 μM), and solution pH (3-10), IMD was completely oxidized in 2 h without interferences from leached metal ions. Such performance was also achieved when using tap water but was inhibited by a simulated municipal wastewater due to scavenging effects promoted by inorganic and organic species. Although there was evidence of the presence of sulfate radicals and singlet oxygen oxidizing species, only four intermediate compounds were detected by liquid chromatography coupled to mass spectrometry analysis, mainly due to hydroxyl addition reactions. Concerning the changes in surface properties of CuMF after use, no morphological or structural changes were observed except a small increase in the charge transfer resistance. Based on the changes of terminal surface groups, PMS activation occurred on Fe sites.

Enhanced antibiotic degradation via photo-assisted peroxymonosulfate over graphitic carbon nitride nanosheets/CuBi2O4: Highly efficiency of oxygen activation and interfacial charge transfer

Improving the activation capacity of peroxymonosulfate (PMS) to increase radical and non-radical production is critical for antibiotic degradation. However, how to boost reactive oxygen species (ROS) and speed interfacial charge transfer remains an essential challenge. We report a coupling system of 10 %CNNS/CuBi2O4 photocatalyst and sulfate radical-based advanced oxidation processes (SO4--AOPs) to enhance the activation of PMS and improve antibiotic degradation. Owing to highly efficient oxygen activation and interfacial charge transfer, the degradation efficiency of the photo-assisted PMS system was as high as 51.6 times and 2.8 times that of photocatalyst and SO4--AOPs alone, respectively. Importantly, the highly efficient oxygen activation resulted in the production of O2-, which in turn could utilize the excess electrons generated through efficient interfacial charge transfer to convert into non-radical 1O2. The total organic carbon (TOC) elimination effectiveness of the photo-assisted PMS system reached 82 % via the synergy of radicals and non-radicals (O2-, OH, 1O2, SO4-, h+). This system also had excellent potential for reducing the generation and toxicity of disinfection by-products (DBPs), as evidenced through significant reductions in concentrations of trichloromethane (TCM), dichloroacetic acid (DCAA), and trichloronitromethane (TCNM) by 76 %, 64 %, and 35 %, respectively, providing an effective and eco-friendly strategy for antibiotic treatment.

2D/2D heterojunctions for rapid and self-cleaning removal of antibiotics via visible light-assisted peroxymonosulfate activation: Efficiency, synergistic effects, and applications

Developing eco-friendly and efficient technologies for treating antibiotic wastewater is crucial. Traditional methods face challenges in incomplete removal, high costs, and secondary pollution. Heterogeneous peroxymonosulfate (PMS) activation assisted by visible light shows promise, but suitable activators remain a huge challenge. Here, we synthesized cost-effective carbon nitride/bismuth bromide oxide (CN/BiOBr) heterojunctions. Such a heterojunction achieved rapid PMS activation, achieving over 90.00% tetracycline (TC) removal only within 1 min (kobs of 2.23 min-1), surpassing previous systems by nearly 1-2 orders of magnitude and even remarkably superior to the popular single-atom catalysts. The system exhibited self-cleaning properties, maintaining activity after 8 cycles and stability across a wide pH range (3.01 to 9.03). Quenching experiments and theoretical calculations elucidated the exclusive •O2- species involvement and removal pathways. Eco-toxicity assessment and total organic carbon results confirmed simultaneous degradation, detoxification, and mineralization. This system also showed excellent resistance to environmental factors, e.g., coexisting anions, varying pH, and water sources, and demonstrated potential in coking and medical wastewater purification. This study presents a novel technique for rapidly decontaminating antibiotic wastewater through visible light-assisted PMS activation and introduces innovative bionic catalytic oxidation combining light and darkness for practical applications.

Modulating electron density enable efficient cascade conversion from peroxymonosulfate to superoxide radical driven by electron-rich/poor dual sites

The superoxide radical (•O2-)-mediated peroxymonosulfate (PMS)-based photo-Fenton-like reaction enables highly selective water decontamination. Nevertheless, the targeted construction of •O2--mediated photo-Fenton-like system has been challenging. Herein, we developed an electron-rich/-poor dual sites driven •O2--mediated cascade photo-Fenton-like system by modulating electron density. Experimental and theoretical results demonstrated that PMS was preferentially adsorbed on electron-poor Co site. This adsorption promoted O-O bond cleavage of PMS to generate hydrogen peroxide (H2O2), which then migrated to electron-rich O site to extract eg electrons for O-H bond cleavage, rather than competing with PMS for Co site. The developed versatile cascade reaction system could selectively eliminate contaminants with low n-octanol/water partition constants (KOW) and dissociation constants (pKa) and remarkably resist inorganics (Cl-, H2PO4- and NO3-), humic acid (HA) and even real water matrices (tap water and secondary effluent). This finding provided a novel and plausible strategy to accurately and efficiently generate •O2- for the selective water decontamination.

Effective Activation of Peroxymonosulfate by Oxygen Vacancy Induced Musa Basjoo Biochar to Degrade Sulfamethoxazole: Efficiency and Mechanism

Biochar materials have garnered attention as potential catalysts for peroxymonosulfate (PMS) activation due to their cost-effectiveness, notable specific surface area, and advantageous structural properties. In this study, a suite of plantain-derived biochar (MBB-400, MBB-600, and MBB-800), possessing a well-defined pore structure and a substantial number of uniformly distributed active sites (oxygen vacancy, OVs), was synthesized through a facile calcination process at varying temperatures (400, 600, and 800 °C). These materials were designed for the activation of PMS in the degradation of sulfamethoxazole (SMX). Experimental investigations revealed that OVs not only functioned as enriched sites for pollutants, enhancing the opportunities for free radicals (•OH/SO4•-) and surface-bound radicals (SBRs) to attack pollutants, but also served as channels for intramolecular charge transfer leaps. This role contributed to a reduction in interfacial charge transfer resistance, expediting electron transfer rates with PMS, thereby accelerating the decomposition of pollutants. Capitalizing on these merits, the MBB-800/PMS system displayed a 61-fold enhancement in the conversion rate for SMX degradation compared to inactivated MBB/PMS system. Furthermore, the MBB-800 exhibited less cytotoxicity towards rat pheochromocytoma (PC12) cells. Hence, the straightforward calcination synthesis of MBB-800 emerges as a promising biochar catalyst with vast potential for sustainable and efficient wastewater treatment and environmental remediation.

Engineering highly dispersed AgI nanoparticles on hierarchical In2S3 hollow nanotube to construct Z-scheme heterojunction for efficient photodegradation of insecticide imidacloprid

Increasing the exposure of active sites and improving the intrinsic activity are necessary considerations for designing a highly efficient photocatalyst. Herein, an In2S3/AgI stable Z-scheme heterojunction with highly dispersed AgI nanoparticles (NPs) is synthesized by the mild self-templated and in-situ ion exchange strategy. Impressively, the optimized In2S3/AgI-300 Z-scheme heterojunction exhibits superior photodegradation activity (0.020 min-1) for the decomposition of insecticide imidacloprid (IMD), which is extremely higher than that of pure In2S3 (0.002 min-1) and AgI (0.013 min-1). Importantly, the three-dimensional excitation-emission matrix (3D EEMs) fluorescence spectra, high-resolution mass spectrometry (HRMS), the photoelectrochemical tests, radical trapping experiment, and electron spin resonance (ESR) technique are performed to clarify the possible degradation pathway and mechanism of IMD by the In2S3/AgI-300 composite. The enhanced photocatalytic performance is attributed to the highly dispersed AgI NPs on hierarchical In2S3 hollow nanotube and the construction of In2S3/AgI Z-scheme heterojunction, which can not only increase active site exposure, but also improve its intrinsic activity, facilitating rapid charge transfer rate and excellent electron-hole pairs separation efficiency. Meanwhile, the practical application potential of the In2S3/AgI-300 composite is systematically investigated. This study opens a new insight for designing catalysts with high photocatalytic performance through a convenient approach.

Degradation of Pesticides Using Semiconducting and Tetrapyrrolic Macrocyclic Photocatalysts-A Concise Review

Exposure to pesticides is inevitable in modern times, and their environmental presence is strongly associated to the development of various malignancies. This challenge has prompted an increased interest in finding more sustainable ways of degrading pesticides. Advanced oxidation processes in particular appear as highly advantageous, due to their ability of selectively removing chemical entities form wastewaters. This review provides a concise introduction to the mechanisms of photochemical advanced oxidation processes with an objective perspective, followed by a succinct literature review on the photodegradation of pesticides utilizing metal oxide-based semiconductors as photosensitizing catalysts. The selection of reports discussed here is based on relevance and impact, which are recognized globally, ensuring rigorous scrutiny. Finally, this literature review explores the use of tetrapyrrolic macrocyclic photosensitizers in pesticide photodegradation, analyzing their benefits and limitations and providing insights into future directions.

Peroxymonosulfate assisted pesticide breakdown: Unveiling the potential of a novel S-scheme ZnO@CoFe2O4 photo-catalyst, anchored on activated carbon

A ternary hetero-junction was prepared by anchoring ZnO@CoFe2O4 (ZCF) on activated carbon (AC) and employed as a UV-assisted peroxymonosulfate (PMS) activator to boost the degradation of diazinon (DZN) pesticide. The structure, morphology, and optical properties of the ZCFAC hetero-junction were characterized through a series of techniques. The highest degradation efficiency of DZN (100% in 90 min) was achieved by the PMS-mediated ZCFAC/UV system, superior to other single or binary catalytic systems due to the strong synergistic effect between ZCFAC, PMS, and UV. The operating reaction conditions, synergistic effects, and the possible pathways of DZN degradation were investigated and discussed. Optical analysis showed that the band-gap energy of the ZCFAC hetero-junction not only enhanced the absorption of UV light but also reduced the recombination of photo-induced electron/hole pairs. Both radical and non-radical species (HO•, SO4•-, O2•-, 1O2, and h+) took part in the photo-degradation of DZN, assessed by scavenging tests. It was found that AC as a carrier not only improved the catalytic activity of CF and ZnO nanoparticles and conferred high stability for the catalyst but also played a crucial role in accelerating the catalytic PMS activation mechanism. Moreover, the PMS-mediated ZCFAC/UV system showed good reusability, universality, and practical applicability potential. Overall, this work explored an efficient strategy for the best use of hetero-structure photo-catalysts towards PMS activation to achieve high performance in decontaminating organic compounds.

Performance and microbial metabolic mechanism of imidacloprid removal in a microbial electrolysis cell-integrated adsorption biological coupling system

Coke used as a filler to treat imidacloprid (IMI) wastewater by both adsorption biological coupling and microbial electrolysis cells (MEC)-adsorption biological coupling technologies, the removal efficiencies on pollutions in wastewater containing IMI were investigated, and the key functional genes related to IMI degradation pathways were also revealed. Results showed that the removal rates of COD, ammonia nitrogen, TP, and IMI under the adsorption biological coupling treatment and MEC-adsorption biological coupling treatment were 94.61-95.54%, 93.37-95.79%, 73.69-83.80%, and 100%, respectively. MEC increased the relative abundance of Proteobacteria by 9.01% and transformed the dominant bacteria from Lysobacter and Reyranella to Brevundimonas and Aquincola. Moreover, MEC up-regulated the abundance of the coding genes PK (9.30%), narG (2.26%), pstS (3.63%), and phnD (1.32%), and converted the IMI degradation products to smaller molecular weight C6H8N2 and C6H6ClNO. This study provided an important reference information for efficient treatment of IMI wastewater using the MEC-adsorption biological coupling technology.

Oxygen doped graphite carbon nitride as efficient metal-free catalyst for peroxymonosulfate activation: Performance, mechanism and theoretical calculation

In this study, oxygen-doped graphitic carbon nitride (g-C3N4), named O-g-C3N4, was successfully fabricated and characterized, and its performance in activating peroxymonosulfate (PMS, HSO5-) for the removal of phenol, 2,4-dichlorophenol (2,4-DCP), bisphenol A (BPA), rhodamine B (RhB), reactive brilliant blue (RBB) and acid orange 7 (AO7) was evaluated. The catalytic performance of O-g-C3N4 for AO7 removal increased by 14 times compared to g-C3N4. In the presence of 0.2 g L-1 O-g-C3N4, 3.5 mM PMS at natural pH 5.8, 96.4% of AO7 could be removed in 60 min, reduced toxicity of the treated AO7 solution was obtained, and the mineralization efficiency was 47.2% within 120 min. Density functional theory (DFT) calculations showed that the charge distribution changed after oxygen doping, and PMS was more readily adsorbed by O-g-C3N4 with the adsorption energy (Eads) of -0.855 kcal/mol than that of the pristine g-C3N4 (Eads: -0.305 kcal/mol). Mechanism investigation implied that AO7 was primarily removed by the sulfate radicals (SO4•-) and hydroxyl radicals (•OH) on the surface of O-g-C3N4, but the role of singlet oxygen (1O2) to AO7 elimination was negligible. The results of cyclic experiments and catalyst characterization after reaction confirmed the favorable catalytic activity and structural stability of O-g-C3N4 particles. Furthermore, the O-g-C3N4/PMS system was very resistant to most of the environmental impacts, and AO7 removal was still acceptable in natural water environment. This study may provide an efficient metal-free carbonaceous activator with low dosage for PMS activation to remove recalcitrant organic pollutants (ROPs).

Simultaneous photocatalytic biomass conversion and CO2 reduction over high crystalline oxygen-doped carbon nitride

Simultaneous photocatalytic biorefinery and CO2 reduction to co-produce fuels and high value-added chemicals have recently attracted significant attention; however, comprehensive studies are still lacking. Herein, we report the preparation of highly crystalline oxygen-doped carbon nitride nanotubes (O-CNNTs-x) using an ammonium fluoride-assisted hydrothermal/calcination strategy. The hollow structure, high crystallinity, and O incorporation endowed the O-CNNTs-x with photocatalytic activity by considerably improving optical absorption and modulating the charge carrier motion. The lactic acid yield and CO evolution rate over O-CNNTs-2.0 reached 82.08% and 67.95 μmol g-1 h-1, which are 1.57- and 7.37-fold times higher than those of CN, respectively. Moreover, ·OH plays a key role in the oxidation half-reaction. This study offers a facile approach for fabricating highly crystalline element-doped CN with a customizable morphology and electronic properties and demonstrates the viability of co-photocatalytic CO2 reduction and biomass selective oxidation.

Remediation technologies for neonicotinoids in contaminated environments: Current state and future prospects

Neonicotinoids (NEOs) are synthetic insecticides with broad-spectrum insecticidal activity and outstanding efficacy. However, their extensive use and persistence in the environment have resulted in the accumulation and biomagnification of NEOs, posing significant risks to non-target organisms and humans. This review provides a summary of research history, advancements, and highlighted topics in NEOs remediation technologies and mechanisms. Various remediation approaches have been developed, including physiochemical, microbial, and phytoremediation, with microbial and physicochemical remediation being the most extensively studied. Recent advances in physiochemical remediation have led to the development of innovative adsorbents, photocatalysts, and optimized treatment processes. High-efficiency degrading strains with well-characterized metabolic pathways have been successfully isolated and cultured for microbial remediation, while many plant species have shown great potential for phytoremediation. However, significant challenges and gaps remain in this field. Future research should prioritize isolating, domesticating or engineering high efficiency, broad-spectrum microbial strains for NEO degradation, as well as developing synergistic remediation techniques to enhance removal efficiency on multiple NEOs with varying concentrations in different environmental media. Furthermore, a shift from pipe-end treatment to pollution prevention strategies is needed, including the development of green and economically efficient alternatives such as biological insecticides. Integrated remediation technologies and case-specific strategies that can be applied to practical remediation projects need to be developed, along with clarifying NEO degradation mechanisms to improve remediation efficiency. The successful implementation of these strategies will help reduce the negative impact of NEOs on the environment and human health.

Degradation of tetracycline by peroxymonosulfate activated with Mn0.85Fe2.15O4-CNTs: Key role of singlet oxygen

Tetracycline (TC) is a kind of electron-rich organic, and singlet oxygen (¹O₂) oxidative pathway-based advanced oxidation processes (AOPs) have represented outstanding selective degradation to such pollutants. In this paper, an excellent prepared strategy for ¹O₂ dominated catalyst was adopted. A catalyst composed of non-stoichiometric doping Mn-Fe bimetallic oxide supported on CNTs (0.3-Mn_0.85Fe_2.15O₄-CNTs) was synthesized and optimized by regulating the non-stoichiometric doping ratio of Mn & Fe and the loading amount of CNTs. Through optimization and control experiments, the optimized catalyst represented 94.9% of TC removal efficiency within 60 min in neutral condition under relatively low concentrations of Mn_0.85Fe_2.15O₄-CNTs (0.4 g/L) and PMS (0.8 mM). Through SEM and XRD characterization, Mn_0.85Fe_2.15O₄-CNTs was a hybrid of cubic Mn_0.85Fe_2.15O₄ uniformly dispersing on CNTs. By the characterization of XPS and FT-IR, more CO bonds and low-valent Mn (II) & Fe (II) appeared in Mn_0.85Fe_2.15O₄-CNTs. Reactive oxygen species (ROS) was determined by radical quenching experiments and electron spin resonance (EPR) spectroscopy, and ¹O₂ was verified to be the dominated ROS. The mechanism for PMS' activation was speculated, and more low-valent Mn (II) and Fe (II) contributed to the production of free-radical (•OH & SO₄^•-), while the reaction between PMS and the enhanced CO bond on Mn_0.85Fe_2.15O₄-CNTs played a crucial part in the generation of ¹O₂. In addition, through the comparative degradation of four different organics with distinct charge densities, the excellent selectivity of ¹O₂-based oxidative pathway to electron-rich pollutants was found. This paper supplied a good strategy to prepare catalyst for PMS activation to form a ¹O₂-dominated oxidative pathway.

Synergistic activation of persulfate by FeS@SBA-15 for imidacloprid degradation: Efficiencies, activation mechanism and degradation pathways

In this work, FeS supported SBA-15 mesoporous silica catalyst (FeS@SBA-15) was synthesized successfully, characterized and first applied to persulfate (PS) activation for the degradation of imidacloprid in wastewater. The as-prepared 3.5-FeS@SBA-15 presented an impressive imidacloprid removal efficiency of 93.1% and reaction stoichiometric efficiency (RSE) of 1.82% after 5 min, ascribed to the synergetic effects of improved FeS dispersion and abundant surface sites by SBA-15. Electron paramagnetic resonance spectra and quenching experiments proved that both SO4·- and ·OH were produced in FeS@SBA-15/PS system, and SO4·- played a dominant role in the degradation process. The S2- can accelerate the cycling of Fe(III)/Fe(II) during activation and increase the steady-state concentration of Fe(II). More importantly, the constructed heterogeneous system exhibited an efficient and stable catalytic activity over a wide range of pH (3.0-9.0), temperature (283K-313K), inorganic ion (NO3-) and humic acid (1-20 mg/L). Moreover, the density functional theory calculations were conducted to predict the potential reaction sites of imidacloprid. Based on eighteen identified intermediates, four main degradation pathways were proposed: hydroxylation, dechlorination, hydrolysis, and the ring cleavage of the imidazolidine. ECOSAR analysis indicated hydroxylation and dechlorination played a key role in the detoxification of the formed compounds. These findings would provide new insights into the application of FeS@SBA-15 catalyst in wastewater treatment and the removal mechanism of imidacloprid from wastewater.

Fe3O4 quantum dots mediated P-g-C3N4/BiOI as an efficient and recyclable Z-scheme photo-Fenton catalyst for tetracycline degradation and bacterial inactivation

Photo-Fenton technology integrated by photocatalysis and Fenton reaction is a favorable strategy for water remediation. Nevertheless, the development of visible-light-assisted efficient and recyclable photo-Fenton catalysts still faces challenges. This study successfully constructed a novel separable Z-scheme P-g-C₃N₄/Fe₃O₄QDs/BiOI (PCN/FOQDs/BOI) heterojunction via in-situ deposition method. The results showed that the photo-Fenton degradation efficiency for tetracycline over optimal ternary catalyst reached 96.5% within 40 min at visible illumination, which was 7.1 and 9.6 times higher than its single photocatalysis and Fenton system, respectively. Moreover, PCN/FOQDs/BOI possessed excellent photo-Fenton antibacterial activity, which could completely inactivate 10⁸ CFU·mL^-1 of E. coli and S. aureus within 20 and 40 min, respectively. Theoretical calculation and in-situ characterization revealed that the enhanced catalysis behavior resulted from the FOQDs mediated Z-scheme electronic system, which not only facilitated photocreated carrier separation of PCN and BOI while maintaining maximum redox capacity, but also accelerated H₂O₂ activation and Fe³⁺/Fe²⁺ cycle, thus synergistically forming more active species in system. Additionally, PCN/FOQDs/BOI/Vis/H₂O₂ system displayed extensive adaptability at pH range of 3-11, removal universality for various organic pollutants and attractive magnetic separation property. This work would provide an inspiration for design of efficient and multifunctional Z-scheme photo-Fenton catalyst in water purification.

O and S co-doping induced N-vacancy in graphitic carbon nitride towards photocatalytic peroxymonosulfate activation for sulfamethoxazole degradation

Doping-induced vacancy engineering of graphitic carbon nitride (GCN) is beneficial for bandgap modulation, efficient electronic excitation, and facilitated charge carrier migration. In this study, synthesis of oxygen and sulphur co-doped induced N vacancies (OSGCN) by the hydrothermal method was performed to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) antibiotic degradation and H₂ production. The results from experimental and DFT simulation studies validate the synergistic effects of co-dopants and N-vacancies, i.e., bandgap lowering, electron-hole pairs separation, and high solar energy utilization. The substitution of sp² N atom by O and S co-dopants causes strong delocalization of HOMO-LUMO distribution, enhancing carrier mobility, increasing reactive sites, and facilitating charge-carrier separation. Remarkably, OSGCN/PMS photocatalytic system achieved 99.4% SMX degradation efficiency and a high H₂ generation rate of 548.23 μ mol g^-1 h^-1 within 60 min and 36 h, respectively under visible light irradiations. The SMX degradation kinetics was pseudo-first-order with retained recycling efficiency up to 4 catalytic cycles. The results of EPR and chemical scavenging experiments revealed the redox action of reactive oxidative species, wherein ¹O₂ was the dominant reactive species in SMX degradation. The identification of formed intermediates and the SMX stepwise degradation pathway was investigated via LC-MS analysis and DFT studies, respectively. The results from this work anticipated deepening the understanding of PMS activation by substitutional co-doping favoring N-vacancy formation in GCN lattice for improved photocatalytic activity.

Orientated construction of visible-light-assisted peroxymonosulfate activation system for antibiotic removal: Significant enhancing effect of Cl. JOURNAL OF HAZARDOUS MATERIALS 2023;445:130476. [PMID: 36455327 DOI: 10.1016/j.jhazmat.2022.130476]

Antibiotic contaminants can migrate over long distances in the water, thus possibly causing severe detriment to the environment and even potential harm to human health. Heterogeneous activation of peroxymonosulfate (PMS) assisted by visible light is an emerging and promising technology for the purification of such wastewater. This study designed an ultra-efficient and stable PMS activator (FeCN) to restore the typical antibiotic-polluted water under harsh conditions. About 90.94% of sulfamethoxazole (SMX) was degraded in 35 min in the constructed FeCN+PMS/vis system, and the reaction rate constant was nearly 50-fold higher than direct photocatalysis. Electron spin resonance, quenching experiments, LC/MS technique, eco-toxicity assessment, and density functional theory validated that the SMX removal was dominated by the attack of h⁺, ^•O₂^- and ¹O₂ on the active atoms of SMX molecules with high Fukui index, presenting as a simultaneous degradation and detoxification process. Such a visible-light-assisted PMS activation system also had good resistance to the environmental water bodies and a broad spectrum in the degradation of various pollutants. In particular, Cl^- (50 mM) could significantly accelerate the removal of SMX with a 32.6-fold increase in catalytic activity, and the mineralization efficiency could reach 56.6% under identical conditions. Moreover, this Cl^- containing system excluded the degradation products of disinfection by-products, and such a system was also versatile for different contaminants. This work demonstrates the feasibility of the FeCN+PMS/vis system for the remediation of antibiotic-contaminated wastewater in the presence and absence of Cl^-, and also highlights their great potential in WWTPs.

Improved catalytic performance of ZnO via coupling with CoFe2O4 and carbon nanotubes: A new, photocatalysis-mediated peroxymonosulfate activation system, applied towards Cefixime degradation

In this study, a ternary ZnO@spinel cobalt ferrite@carbon nanotube magnetic photocatalyst (ZSCF@CNT) was successfully synthesized and used to activate peroxymonosulfate (PMS) for Cefixime (CFX) antibiotic degradation under UVC irradiation. The morphology, optical, structural, and physicochemical properties of ZSCF@CNT were characterized and analyzed by XPS, XRD, FESEM-EDX, TEM, BET, VSM, UV-vis DRS and PL analysis. The results indicated that the ternary ZSCF@CNT photocatalyst exhibited superior catalytic activity on CFX elimination than that of individual components and binary composite catalysts, in which CFX with was rapidly removed under UVC irradiation and PMS. The effect of operational parameters including initial PMS, catalyst, and CFX concentrations and solution pH on the catalytic activity was investigated in detail; the optimal conditions were: pH: 7.0, catalyst: 0.3 g/L, PMS: 3.0 mM, leading to total CFX (10 mg/L) elimination in ∼20 min. Based on the radical scavenger tests, various radicals and non-radical species including sulfate, hydroxyl and superoxide radicals, singlet oxygen and electrons were involved in the ZSCF@CNT/PMS/UVC system. The high surface area, reduced agglomeration formation and excellent separation of photogenerated electron-hole pairs embodied in ZSCF@CNT photocatalyst conferred its superior catalytic activity and stability. The results from the tests in real water matrices revealed that ZSCF@CNT could be a promising photocatalyst to activate PMS for actual aqueous matrices' treatment.

Ball milling and acetic acid co-modified sludge biochar enhanced by electrochemistry to activate peroxymonosulfate for sustainable degradation of environmental concentration neonicotinoids

Neonicotinoids pose potential serious risks to human health even at environmental concentration and their removal from water is considered as a great challenge. A novel ball milling and acetic acid co-modified sludge biochar (BASBC) was the first time synthesized, which performed superior physicochemical characteristics including larger surface area, more defect structures and functional groups (e.g., CO and -OH). Electrochemistry was introduced to enhance BASBC for peroxymonosulfate (PMS) activation (E/BASBC/PMS) to degrade environmental concentration neonicotinoids (e.g., imidacloprid (IMI)). The degradation efficiency of IMI was 95.2% within 60 min (C₀ (PMS)= 1 mM, E= 25 V, m (BASBC)= 10 mg). Solution pH and anionic species/concentrations were critical affecting factors. The scavenging and electron paramagnetic resonance experiments suggested that ^•OH and ¹O₂ were the dominant reactive oxygen species contributing to IMI degradation. Three degradation pathways were proposed and pathway Ⅲ was the main one. 86.1% of IMI were mineralized into non-toxic CO₂ and H₂O, and others were converted into less toxic intermediates. Also, E/BASBC/PMS system achieved the sustainable degradation of IMI in the cycle experiments. Additionally, it exhibited excellent degradation performance for other three typical neonicotinoids (96.6% of thiacloprid (THI), 96.5% of thiamethoxam (THX) and 82.6% of clothianidin (CLO)) with high mineralization efficiencies (87.8% of THI, 90.5% of THX and 75.4% of CLO).

Insight into mechanism of peroxydisulfate activation by natural pyrite: Participation of Fe(IV) and regulation of Fe(III)/Fe(II) cycle by sulfur species

In this study, natural pyrite (NP) was used to activate peroxydisulfate (PDS) for imidacloprid (IMD) degradation. NP was characterized by X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Effects of key reaction parameters (NP dosage, PDS concentration and initial pH) and co-existing ions on IMD degradation in the NP/PDS system were investigated. Quenching experiments and electron spin resonance (ESR) tests identified the existence of sulfate radical (SO₄^•-), hydroxyl radical (^•OH), singlet oxygen (¹O₂) and superoxide radical (O₂^•-). The cumulative concentration of SO₄^•- and ^•OH were quantified by the formation of benzoquinone (BQ) and p-hydroxybenzoic acid (HBA), respectively. Meanwhile, more than 60% of methylphenyl sulfoxide (PMSO) was selectively converted to methylphenyl sulfone (PMSO₂), revealing that Fe(IV) was dominant in the NP/PDS system. The order of contribution of the three reactive species in the NP/PDS system was Fe(IV) > ^•OH > SO₄^•- (contributions of ¹O₂ and O₂^•- were negligible). Fe(II) released from NP played a crucial role in PDS activation, and sulfur species in NP could also boost Fe(III)/Fe(II) cycle and contribute to the generation of reactive species. Further, the possible degradation pathways of IMD have been proposed based on the detected intermediates using high-performance liquid chromatography-mass spectrometry (HPLC-MS), and the toxicity (including acute toxicity, developmental toxicity and mutagenicity) of these intermediates have been predicted using Toxicity Estimation Software Tool (T.E.S.T). Moreover, NP/PDS system was applied in four natural water bodies and IMD degradation efficiency reached more than 97% after adjusting the pH to 3. The fluorescence excitation-emission matrix (EEM) spectra showed that in addition to IMD, NP/PDS system could also remove other impurities.

Highly efficient photodegradation of magnetic GO-Fe3O4@SiO2@CdS for phenanthrene and pyrene: Mechanism insight and application assessment

A novel magnetic core-shell Fe₃O₄@SiO₂@CdS embedded graphene oxide (GO) composite was prepared for the visible-light-driven photodegradation of high ring number polycyclic aromatic hydrocarbons (PAHs). The potential application of GO-Fe₃O₄@SiO₂@CdS was evaluated through the photodegradation of phenanthrene and pyrene in deionized water, tap water, and lake water, respectively. It was found that GO-Fe₃O₄@SiO₂@CdS could remove 86.4 % of phenanthrene and 93.4 % of pyrene, suggesting its potential for the degradation of high-ring number PAHs. The density functional theory (DFT) calculations demonstrate that pyrene has more active sites attacked by free radicals. The photoelectrochemical measurement and quenching experiments indicate that GO can transfer photoelectrons efficiently, resulting in the crucial radicals (O₂^-, OH and ¹O₂). More importantly, the photocatalytic activity kept almost constant during five cycles, confirming the significant anti-photocorrosion of GO-Fe₃O₄@SiO₂@CdS. This work provides some new insights into the removal of PAHs with high-ring numbers in the natural water environment.

Synergistic effect of novel Co-modified micro/nano geopolymers in a photo-PDS system

Persulfate activation is an efficient advanced oxidation process for water treatment. However, many catalyst materials make their preparation methods and raw materials very complicated and expensive while pursuing high-efficiency catalytic effects. In this research, a novel Co-modified micro/nano geopolymer (Co-MNG) material was prepared from solid waste using a mechanochemical method. The whole preparation process of Co-MNG is simple and time-saving, and most of its raw materials are solid waste. In addition, it has few adverse effects on the environment during preparation and use and has a good effect on PDS activation. Under dark conditions, 1 mg L^-1 of unloaded Co metal MNG material could degrade 20 mg L^-1 Rhodamine B solution by 79% in 60 min with 15 mM PDS, but the application of visible light could not enhance its effect. However, after adding 4 wt% of different Co-containing compounds, the prepared Co-MNG materials could improve their degradation effect under the same conditions, and it is more obvious under the condition of applying visible light. Among them, MNG-Co(NO₃)₂ could completely degrade RhB within 40 min under the application of visible light. ESR (electron spin resonance) tests showed that the MNG-Co(NO₃)₂ material could generate a variety of active radicals in a photo-PDS system, such as h⁺, ·OH, ·O₂^- and SO₄^-. Mechanistic research experiments showed that both visible light and Co-MNG materials can activate PDS to a certain extent, but when both exist at the same time, the material could effectively couple visible light and Co activation of PDS in a photo-PDS activation system to achieve synergistic degradation of pollutants in water.

Mechanistic insights into UV photolysis of carbamazepine and caffeine: Active species, reaction sites, and toxicity evolution

The pseudo-persistence of pharmaceutical and personal care products (PPCPs)in the aqueous environment may pose potential risks to human health and ecosystems. The UV disinfection in wastewater treatment plants is one of the essential processes before PPCPs enter the water environment, so it is crucial to elucidate the photolytic behavior and mechanism of PPCPs under UV radiation. In this work, carbamazepine (CBZ) and caffeine (CAF) were selected as typical pollutants to investigate the effect of water matrixes, humic acid, inorganic ions, and pH on the UV radiation performance. Hydroxyl radical (•OH) and singlet oxygen (¹O₂) were identified by quenching experiments and electron paramagnetic resonance (EPR) spectra as playing a dominant role in the degradation process. UPLC-TOF/MS was conducted to identify 13 and 14 possible intermediates of CBZ and CAF, respectively. Moreover, combining density functional theory (DFT) calculations (Frontier Molecular Orbital and Fukui index), hydroxylation, oxidation, and ring cleavage were proposed as the main degradation pathways of the contaminants, which occurred first at the C(7C), N(17 N) and O(18O) sites of CBZ and at the C(9C) site of CAF. The bio-acute toxicity experiment and the Ecological Structure-Activity Relationships (ECOSAR) program were performed to analyze and predict the toxicity of the intermediates of CBZ and CAF under UV radiation, respectively. The results showed that the acute toxicity of both solutions increased after UV radiation and followed with the combined toxicity. This work has great scientific value and practical environmental significance for evaluating the UV disinfection process and managing PPCPs in the aqueous environment.

Changes in the catalytic activity of oxygen-doped graphitic carbon nitride for the repeated degradation of oxytetracycline

Metal-free carbonaceous catalysts have gained growing interest because of their excellence in organic pollutant degradation. However, most of them suffer from deactivation after use, and the origins have not been investigated or understood. In this study, the changes in the characteristics after multiple uses of a carbonaceous catalyst, i.e., oxygen-doped graphitic carbon nitride (O-gCN), were investigated to identify the key factors affecting its reactivity. The O-gCN was repeatedly used to remove an antibiotic (oxytetracycline, OTC) in the presence of peroxymonosulfate (PMS). OTC removal was significantly reduced as the O-gCN was repeatedly used. The reactivity of O-gCN used five times (O-gCN5) corresponded well with the decreased signals of DMPO-X, DMPO-O₂^•-, and TEMP-¹O₂ in electron paramagnetic resonance spectra. These signal changes were accompanied by a shift of the involved reactive species from ¹O₂ and OH^• for O-gCN to ¹O₂ and SO₄^•- for O-gCN5. The changes in activity and involved reactive species were attributed to the changes in the properties of O-gCN, considering the negligible OTC adsorption and slight PMS consumption. The results of X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy showed a decrease in the degree of defects, graphene-like layers, and crystallinity in graphitic structures, but an increase in the fractions of N and O, for O-gCN5. However, the OTC degradation pathways and intermediates were not significantly different for O-gCN and O-gCN5. These results provide valuable information for developing strategies for the design, practical use, and regeneration of carbonaceous catalysts.

Structural Effects of Metal Single-Atom Catalysts for Enhanced Photocatalytic Degradation of Gemfibrozil

The development of efficient catalysts is a highly necessary but challenging task within the field of environmental water remediation. Single-atom catalysts are promising nanomaterials within this respect, but in-depth studies encompassing this class of catalysts remain elusive. In this work, we systematically study the degradation of gemfibrozil, a persistent pollutant, on a series of carbon nitride photocatalysts, investigating both the effect of (i) catalyst textural properties and (ii) metal single atoms on the contaminant degradation. Tests in the absence of the catalyst result in negligible degradation rates, confirming the stability of the contaminant when dispersed in water. Then, photocatalytic tests at optimal pH, solvent, and wavelength reveal a correlation between the support surface area and the degradation. This points to the role of carbon nitride surface nanostructure on gemfibrozil degradation. In particular, the use of silver on mesoporous carbon nitride single-atom catalyst (Ag@mpgC₃N₄) leads to an unprecedented degradation of gemfibrozil (>90% within 60 min). The possible degradation intermediates and products were identified by mass spectrometry and were inert by cytotoxicity evaluation. We anticipate that, with further refinement and customization, the carbon nitride catalysts reported herein may find broad applications for light-driven degradation of other contaminants of emerging concern.

Enhanced adsorption and catalytic degradation of antibiotics by porous 0D/3D Co3O4/g-C3N4 activated peroxymonosulfate: An experimental and mechanistic study

In this work, Co₃O₄/g-C₃N₄ catalyst with highly efficient adsorption and degradation of antibiotics was developed based on the combination of three-dimensional (3D) porous morphological controls of g-C₃N₄ and the loading of Co₃O₄ quantum dots (Co₃O₄ QDs). It was discovered that the catalyst can effectively activate peroxymonosulfate (PMS) through a non-photochemical path, and a high tetracycline elimination rate of 99.7% can be achieved within 18 min. The characterization and density functional theory calculation results demonstrated that the porous 3D structure can not only promote the substrate adsorption reaction but also provide large surface area and countless exposed active sites for catalytic reaction. The introduction of Co₃O₄ QDs lowered activation energy barrier and lead to high energy of PMS adsorption. More efficient charge migration between the catalyst and PMS further accelerated PMS activation. Thus, leading to the excellent catalytic performance. In addition, non-free radical mediated degradation mechanism of catalytic activity was also proposed. This work provides a scheme for designing novel and efficient PMS activators for the removal of abusive antibiotics from aqueous environments.

Construction of Li/K dopants and cyano defects in graphitic carbon nitride for highly efficient peroxymonosulfate activation towards organic contaminants degradation

As an emerging peroxymonosulfate (PMS) activation catalyst, graphitic carbon nitride (g-C₃N₄) is non-toxic and eco-friendly, while its poor catalytic performance hinders the application of pristine g-C₃N₄. Herein, a simple LiCl/KCl molten salts-assisted thermal polymerization method was adopted to promote the photocatalytic performance of g-C₃N₄. With the insertion of Li/K dopants and the introduction of surface cyano defects, the modified catalyst exhibited greatly enhanced ability on PMS activation towards acetaminophen removal, observing a 13 times higher rate constant than pristine g-C₃N₄ (k = 0.0435 min^-1 vs. 0.0033 min^-1). The main reactive oxygen species for pollutant degradation were identified as sulfate radicals and singlet oxygen. The wavefunction analysis at excited states based on density functional theory suggests that the introduction of cyano defects greatly promotes the separation of photo-generated electron-hole pairs, thereby achieving higher photocatalytic efficiency. In addition, the doping of Li/K significantly enhances the interaction between PMS and the catalyst surface, and orients the electron transfer from PMS to catalyst to generate non-radical species singlet oxygen, which improves the catalyst resistance to anions-containing water matrices.