Advanced Oxidation Processes Research Articles

Activation of peroxymonosulfate by Fe based metal organic framework for selective degradation of phenol in water

Phenol is a common pollutant in various wastewater, which is required to be removed to a certain standard before the wastewater can be discharged. Persulfate-based advanced oxidation processes (PS-AOPs) are an effective technology for phenol removal, with efficacy contingent upon the activation methods and materials employed. In this study, Fe-based metal-organic frameworks (Fe-MOFs) constructed with carboxylic acid as a ligand were synthesized by a solvothermal method, which can form chelates with ferrous ions. Fe-MOFs showed the activity similar to the homogeneous catalyst thus improving their activation efficiency, and can be used to activate peroxymonosulfate (PMS) for phenol degradation in water. The effects of catalyst dosage, PMS and phenol concentration, temperature, and pH on the degradation efficiency were investigated. Under the optimum reaction conditions, the 96 % of phenol can be rapidly removed in 5 min. SO4·− was determined as the primary radical. Fe species on Fe-MOFs acted as the key active sites. Density functional theory (DFT) analysis suggested enhanced charge redistribution, fostering electron-rich sites that facilitate electron transfer in AOPs, thus boosting phenol degradation. The Fe-MOFs/PMS system enables iron recycling and efficient phenol degradation in water, indicating the potential for phenol-contaminated water treatment.

ZIF-derived non-bonding Cu/Zn catalysts-driven peroxymonosulfate activation via selective generation of surface-bound radicals for efficient water purification

The peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) have been extensively studied in wastewater treatment due to their ability to generate various reactive oxygen species. However, the ultra-short half-lives of free radical species limit their effective transfer from the catalyst surfaces to the target organic contaminants for efficient decontamination. Thus, directed production of reactive species with longer lifetimes is challenging but belong with significant demand. In this study, a catalyst with neighboring Cu and Zn heteroatoms pairs anchored on the surface of zeolitic imidazolate framework (Cu/Zn-ZIF) was designed to selectively and sustainably generate radicals via PMS activation. Electron energy-loss spectroscopy (EELS) demonstrated the formation of non-bonding Cu-Zn heteroatom pairs. Owing to the synergistic effect of the Cu and Zn heteroatoms, the Cu/Zn-ZIF/PMS system achieved 99.5 % removal rate of bisphenol A (BPA) within 60 min. Therein, PMS was stabilized by the strongly adsorptive Cu/Zn-ZIF and activated within the nanoscale confinement of Cu sites, resulting in the directional generation of surface-bound •OH and SO4•− radicals with longer lifetimes, which facilitated the efficient removal of BPA. Significantly, it also demonstrated robust resilience against disruptions caused by intricate aquatic environments, including freshwater bodies and ionic species. These findings provide reference for theoretical research on the design of functional MOFs materials and the practical application of surface-bound radicals in AOPs

The peculiar role of iodides and formation of iodinated oligomer byproducts upon phenol mineralization with boron-doped diamond anode

Formation of halogenated aromatic byproducts upon electrochemical advanced oxidation processes (EAOPs) had attracted increasing concerns in recent years. However, previous correlative works mainly focused on the generation of chlorinated and brominated byproducts, and the works concerning iodinated byproducts were still missing. Herein, this research was designed to investigate the generation of iodinated aromatic byproducts (IABs) during phenol electrochemical degradation with boron-doped diamond (BDD) anode. Firstly, response surface methodology was employed to compare the effects of major operating parameters on the mineralization efficiency, and the peculiar role of iodide ions was thus identified. Next, LC/MS analysis was conducted to identify the iodinated organic byproducts. Twenty-six major IABs were identified with NaI as electrolyte, including p-iodinated phenol, 2,4-diiodophenol, and iodinated dimers and trimers with complex ether structures. These findings confirmed the critical role of active iodine species during the electrolytic oxidations, as well as the overlooked coupling reactions between iodinated phenoxy radicals. Lastly, the structural characteristics of iodinated oligomers had been compared with those of chlorinated and brominated ones. Since IABs were more genotoxic than their chlorinated and brominated analogues, their formations should be carefully treated when EAOPs were applied in environmental matrices containing free iodide ions.

High-efficiency PMS activation by difunctional Co-Fe PBA/g-C3N4 S-scheme heterojunction for oxytetracycline degradation: Performance evaluation and mechanism insight

The utilization of sulfate radical-based advanced oxidation processes (SR-AOPs) has captivated the academic community due to their minimal energy requirements and superior efficacy in peroxomonosulfate (PMS) activation for pollutant decomposition. Notwithstanding these advantages, engineering an effective and economical catalyst for PMS activation presents a considerable hurdle. In the present study, a metal-organic framework of CoFe PBA is ingeniously anchored onto g-C3N4 nanosheets, resulting in the formation of an innovative CoFe PBA/g-C3N4 S-scheme heterojunction that demonstrates remarkable efficiency in PMS activation. Intriguingly, the catalytic efficiency of CoFe PBA/g-C3N4 surpasses that of g-C3N4 and CoFe PBA by 7-fold and 2.33-fold, respectively. The heightened activity of CoFe PBA/g-C3N4 heterojunction is attributed to the enhanced charge transfer efficiency, a consequence of the successful heterojunction formation. Concurrently, the ability of photoexcited electrons to reduce Co3+/Fe3+ to Co2+/Fe2+ bolsters PMS activation. Significantly, this heterojunction retains unparalleled stability in degrading oxytetracycline without discernible performance attenuation, heralding its commendable prospects in real-world applications. Besides, mechanism exploration indicates that SO4−, h+, and electron transfer contribute to oxytetracycline degradation in the CoFe PBA/g-C3N4 system. This investigation serves as a beacon for the strategic development of highly active and stable catalysts for PMS activation, aiming at environmental decontamination.

Fermi energy level synergistic Bi-based electron bridge construction of Z-type heterojunctions to accelerated photogenerated charge transfer for photostability and contaminant mineralization

Advanced oxidation technologies offer new opportunities for pollutant degradation. Despite the existence of numerous photocatalyst heterojunctions for advanced oxidation, their charge transfer and separation efficiency is low due to inadequate interfacial modulation, especially for Type II heterojunctions. Here, through metal reduction, metal defects with regulating the Fermi level and metal electron bridges with facilitate the separation of photo-generated carriers, facilitating the transition from Type II to Z-type heterojunctions. Herein, we designed a Z-Scheme photocatalyst with Bi-based electron bridges (referred to as ‘fishbone-like’ BiVO4/Bi/CuO) synthesized through in situ reduction, utilized for RhB degradation. Under visible light irradiation, the degradation rate of RhB up to 99 % within 120 min, outperforming most previously reported photocatalysts. Notably, the well-designed BiVO4/Bi/CuO exhibits as reaction rate of 4.13 × 10-2 ·min−1, which is 18 times higher than the pure BiVO4. The BiVO4/Bi/CuO photocatalyst demonstrates exceptional stability over 6 reaction cycles spanning 15 h, due to strengthened contact interface of BiVO4/Bi/CuO. The metal Bi can induce the surface plasmon resonance (SPR) effect, enhancing light absorption. Furthermore, Bi-based electron bridges significantly promote the charge transfer across the Z-type heterojunction interface, which were verified by assorted experimental outcomes and density functional theory (DFT) calculations. This work represents a promising platform for the development of highly efficient and stable photocatalysts that have potential in Pollutant degradation applications.

Promotion of Single-Electron Transfer by Low-Coordinated Co Single Atoms to Facilitate Advanced Oxidation Processes in Wastewater Treatment.

Heterogeneous catalysts are fascinating for advanced oxidation processes (AOPs) in wastewater treatment to reduce cost, metal contamination, and pH operation limitations. However, they usually encounter low catalytic efficiency because of the difficult single-electron-transfer (SET) pathway during AOPs. Herein, an efficient heterogeneous catalyst for AOPs is realized through the rational regulation of N coordination around Co single-atom (SA) centers in favor of SET. As guided by calculations, low N coordination enables a high density of electronic states at the Fermi energy level of SA Co to facilitate SET activation of peroxomonosulfate (PMS). A special oxide-compounding method is further applied to decrease the N coordination of SA Co on the carbon carriers from common Co1-N3/4 to the desired Co1-N2. Co1-N2 shows a delightful activity for AOP degradation of various organic pollutants with kinetic rate and turnover frequency values up to 0.862 min-1 and 389 h-1, respectively, greatly outperforming those of Co1-N3/4. It is also superior in a wide pH operation range and has strong resistance to environmental disturbances. Detailed mechanistic investigations confirm the generation of singlet oxygen (1O2) instead of common radical O species from the SET between PMS and Co1-N2, corroborating the calculated results and accounting for the enhanced AOP activity.

Impacts of blending advanced treated water and traditional groundwater supply on lead and copper concentrations and microbial diversity in premise plumbing

In response to stresses on water demands, some regions augment conventional drinking water sources with alternative water supplies such as desalinated seawater and reclaimed wastewater. The advanced treatment of wastewater by reverse osmosis, microfiltration, and advanced oxidation processes can produce high quality water for potable uses. However, if not appropriately stabilized, the resulting water can be corrosive to metal-based distribution pipes and plumbing materials. We conducted long-term premise plumbing pipe loop experiments with copper pipes containing lead solder to test the impact of the introduction of advanced treated water on the water quality. Advanced treated water (ATW) originally at low pH (<7) and low alkalinity (<10 mg/L as CaCO3) was stabilized with a calcite contactor before being blended with baseline ground water (BLW). The effects of percentages of ATW on the release of lead and copper and on the changes in the microbial diversity were monitored. Experiments monitored metal release from pipes receiving (1) only BLW, (2) a series of blends of BLW and ATW that gradually increased from 25 % to 100 % ATW, and (3) an abrupt switch from BLW to 100 % ATW. Introducing 100 % ATW dramatically increased lead release and simultaneously decreased copper release. Pipe scale analysis showed that the introduction of ATW had destabilized sulfate-containing pipe scales, which exposed the copper pipe surface to galvanic corrosion. The dissolution of scale material was associated with a significant decrease in sulfate concentration in the 100 % ATW which was in agreement with theoretical solubility calculations. The impact of blending ATW on microbial diversity was studied via 16S rRNA gene amplicon sequencing. The composition of the microbial communities changed significantly after water was in contact with the copper pipes in experiments with both BLW and ATW. The type of water recirculating in the pipes affected the structure of the microbial community. The results from this study can be useful for water utilities that are considering potable reuse as they develop strategies to mitigate any adverse impacts of water quality changes.

Natural and synthetic hydrogels for dye removal

In recent years, dyes have been classified as recalcitrant contaminants in wastewater, exhibiting significant toxicological characteristics for flora, fauna, and humans. Various techniques are currently being studied for the remediation of water contaminated with dyes. Among the most relevant alternative technologies are bioadsorption, biocoagulation, the use of composite materials, advanced oxidation processes, etc. However, these methods have some disadvantages. Similarly, the use of hydrogels specifically designed for the treatment of contaminated water is a viable and effective alternative. This is due to their ability to adsorb large amounts of water, high porosity, and multiple active sites. This research describes dyes, their classification,toxicity, and ecotoxicity. Additionally, it presents some alternative treatments for water remediation, emphasizing the design of hydrogels based on synthetic and natural macromolecules. These hydrogels are proposed as promising materials for the removal of dyes from contaminated water. The aim of this research is to highlight synthetic and natural hydrogels as promising materials for the decontamination of water from dyes.

Role of Nanomaterials in Degradation of Cosmetics and Pharmaceutical Wastewater: A Review

Biodiversity progress impacts the quality and availability of renewable natural resources. Ecological concerns about air and water pollution have been raised on communal and commercial levels. The continuous release and accumulation of cosmetics and pharmaceutical items in the environment pose significant threats to both ecosystems and human health. The presence of these emerging pollutants from pharmaceutical and cosmetic products has been reported in wastewater streams coming from industrial as well as wastewater treatment plants. This need has driven the development of technologies like advanced oxidation processes such as ozonation, Fenton’s oxidation, photocatalysis, etc. for conventional wastewater treatments. Among these, the photocatalytic processes are presently being efficient since they not only utilize UV light but also visible light. This article mainly focuses on the review of preparation and comparative activity of photocatalysts on cosmetic as well as pharmaceutical wastes degradation. Photocatalysts, in their different forms like nanoparticles, nanorods and nanocomposites, hold great promise due to their stability, non-toxicity and reusability.

Natural Vanadium–Titanium Magnetite Activated Peroxydisulfate and Peroxymonosulfate for Acid Orange II Degradation: Different Activation Mechanisms and Influencing Factors

Persulfate-based advanced oxidation processes have emerged as a promising approach for the degradation of organic pollutants in aqueous environments due to their ability to generate sulfate radicals (SO4−·) within catalytic systems. In this study, peroxydisulfate (PDS) and peroxymonosulfate (PMS) were investigated with the natural vanadium–titanium magnetite (VTM) as the activator for the degradation of acid orange II. The degradation efficiency increased with higher dosages of VTM or persulfate (both PDS and PMS) at lower concentrations (below 10 mM). However, excessive PMS (higher than 10 mM) in the PMS/VTM system led to the self-consumption of free radicals, significantly inhibiting the degradation of acid orange II. The VTM-activated PDS or PMS maintained an effective degradation of acid orange II in a wide pH range (3~11), suggesting remarkable pH stability. The SO4−· was the main active species in the PDS/VTM system, while hydroxyl radical (·OH) also contributed significantly to the PMS/VTM system. In addition, PMS exhibited better thermal stability during VTM activation. Coexisting ions in an aqueous environment such as bicarbonate (HCO3–), carbonate (CO32–), and hydrogen phosphate (HPO42–) had obvious effects on persulfate activation. Our study systematically investigated the different activation processes and influencing factors associated with PDS and PMS when the natural VTM was used as a catalyst, thereby providing new insights into the persulfate-mediated degradation of organic pollutants in aqueous environments.

Mechanistic insight into the self-catalyzed degradation of Cu-EDTA in photocatalytic fuel cell coupled with peroxymonosulfate

The performance and mechanism of self-catalyzed degradation of Cu-EDTA in a peroxymonosulfate (PMS)-coupled photocatalytic fuel cell (PFC) are investigated for the first time. By choosing Ca-EDTA and Pb-EDTA as controls for the comparative experiments, it was estimated that the self-catalyzed degradation of Cu-EDTA in the PMS/PFC/sunlight system contributed 41.8 % of its total degradation and 22.6 % of the total maximum output power density. The self-catalyzed degradation of Cu-EDTA via the released Cu2+ increased the contribution of h+, 1O2, and •OH to Cu-EDTA degradation. In solution, Cu2+ could activate PMS via the Cu2+/Cu+ redox cycle. Moreover, partial Cu2+ could be reduced by e− and deposited on photoanode as copper oxides/copper to form a new heterojunction with TiO2-nanotube-arrays, which improved the separation of charge-carriers and redox capacity of the photoanode, thus enhancing the photocatalysis of PFC and photocatalytic activation of PMS. Besides, the self-catalyzed degradation of Cu-EDTA increased the electricity power generation in the PFC by improving the reactivity of the photoanode and reducing the resistance via deposition. This study proposed new insights into the self-catalyzed degradation of metal-complexes in sulfate radical advanced oxidation processes and provided a clean, efficient, and economical way for Cu-EDTA degradation by enhancing this self-catalysis via the PFC.

Ultrastable cobalt-based chainmail catalyst for degradation of emerging contaminants in water

Developing stable and efficient cobalt-based catalysts for degradation of emerging contaminants (ECs) in water is deemed as a practical strategy to avoid secondary pollution in advanced oxidation processes (AOPs). Herein, we developed a ultrastable cobalt-based chainmail catalysts (Co-NC900) using 2, 2’-bipyridine-assistant pyrolysis method. More than 96.6 % of imidacloprid (IMD) in water could be degraded within 5 min in the presence of Co-NC900 and peroxymonosulfate (PMS). Amazingly, Co-NC900 still give 95 % degradation efficacy for IMD after15 runs. And only 0.083 μg L−1 of Co could be detected in the reaction mixture after continuous using 7 d. Density Functional Theory (DFT) calculations demonstrated that Co-NC900 can efficiently activate PMS through unique ping-pong mechanism (C-N bond breaking and re-forming process), and further degrade ECs. This study presents a novel approach for the development of efficient and stable metal-based catalysts for the removal of ECs from water.

Enhanced Ornidazole Degradation via Peroxymonosulfate Activation Using Nano CoFe2O4‐Decorated Halloysite Nanotubes: A High‐Efficiency and Stable Catalyst Approach

AbstractThis study proposes a novel, cost‐effective nano CoFe2O4‐decorated halloysite nanotubes (CoFe2O4/HNT) catalyst, which effectively degrades the antibiotic ornidazole (ONZ) through peroxymonosulfate (PMS) activation. By using a simple and economical preparation method, ultra‐low amounts of CoFe2O4 are uniformly loaded onto HNTs, significantly improving the activity and stability of the catalyst. The experimental results show that the CoFe2O4/HNT+PMS system can almost completely degrade ONZ within 1 h, with good pH adaptability and resistance to anion interference. The simple synthesis process and low cost of CoFe2O4/HNT make it highly practical for large‐scale applications. Mechanism studies have shown that the synergistic effect between Co and Fe greatly improves the activation efficiency of PMS, generating reactive oxygen species (such as 1O2) that play a key role in ONZ degradation. This work not only elucidates the activation mechanism, but also provides insightful information for advanced oxidation processes (AOP). The results indicate the practicality and importance of CoFe2O4/HNT catalyst in treating harmful pollutants in water, supporting effective and sustainable water purification technologies. In addition, the study emphasizes the elasticity and adaptability of this innovative catalyst system in managing various pollutants, indicating its broad potential for environmental applications.

WS2-Assisted Electrochemical Activation of Peroxymonosulfate for Eliminating Organic Pollutant in Water

Advanced oxidation process based on heterogeneous activation of peroxymonosulfate (PMS) has received significant attention in wastewater remediation. Herein, a facile and effective electrochemical method was introduced in a tungsten sulfide (WS2)-activated PMS process for the removal of a typical azo dye Acid Orange 7 (AO7) in aqueous solution. It was found that the electrochemical activation could remarkably promote the removal of organic pollutants by coupling with WS2/PMS system. The elimination of AO7 in the electro-assisted WS2-activated PMS (E/WS2/PMS) system achieved 95.8% of AO7 removal in 30 min, with the optimal conditions of 1.0 g/L WS2, 1.0 mM PMS, current density of 1.0 mA/cm2 and initial pH of 6.5. Based on quenching experiments and EPR techniques, mechanistic studies confirmed that hydroxyl radical (•OH) and singlet oxygen (1O2) are the primary reactive oxygen species for the oxidation of pollutants. In addition, the influences of pH, WS2 dosage, PMS concentration, current density, common anions and humic acid on the AO7 removal are also investigated in detail. Furthermore, the system exhibited resistance to aqueous matrices, verifying the accepted applicability in real water (i.e., Yangtze River water and Shahu Lake water). In summary, this study demonstrates a green system for the effective removal of contaminants in water, holding significant implications for practical application.

Construction of Asymmetric Filler Density Mixed-Matrix MOF Membranes via Liquid-Phase Ion Activation for Advanced Oxidation Processes.

Mixed-matrix membrane (MMM) reactors incorporating metal-organic framework (MOF) fillers have significant applications in fields such as separation, catalysis, and chiral resolution. However, the traditional method of directly mixing MOF fillers with polymers results in a symmetric structure where most of the MOF fillers are uniformly distributed across the membrane reactor's cross-section. During usage, this leads to a pronounced trade-off between flux and efficiency and the waste of the MOF, as the rich pore characteristics and active sites of MOFs are not fully utilized. In this study, we propose a liquid-phase ion activation strategy that enables the in situ formation of a uniform and densely packed MOF shell layer on the membrane surface during the phase inversion process of MMM fabrication. This asymmetric density distribution of the MOF-based MMM reactor selectively induces the generation of considerable nonradical 1O2 in the peroxomonosulfate (PMS) system, demonstrating superior catalytic degradation performance against antibiotics like TC and dye molecules (with a flux of 1880 L m-2 h-1 and a Kapp value of 648 min-1), as well as outstanding cycling stability and environmental tolerance. This discovery sheds light on the design and engineering of composite membrane materials and applications for advanced oxidation processes in water purification.

Boosting the O2-to-H2O2 Selectivity Using Sn-Doped Carbon Electrocatalysts: Towards Highly Efficient Cathodes for Actual Water Decontamination.

The high cost and often complex synthesis procedure of new highly selective electrocatalysts (particularly those based on noble metals) for H2O2 production are daunting obstacles to penetration of this technology into the wastewater treatment market. In this work, a simple direct thermal method has been employed to synthesize Sn-doped carbon electrocatalysts, which showed an electron transfer number of 2.04 and outstanding two-electron oxygen reduction reaction (ORR) selectivity of up to 98.0 %. Physicochemical characterization revealed that this material contains 1.53 % pyrrolic nitrogen, which is beneficial for the production of H2O2, and -C≡N functional group, which is advantageous for H+ transport. Moreover, the high volume ratio of mesopores to micropores is known to favor the quick escape of H2O2 from the electrode surface, thus minimizing its further oxidation. A purpose-made gas-diffusion electrode (GDE) was prepared, yielding 20.4 mM H2O2 under optimal electrolysis conditions. The drug diphenhydramine was selected for the first time as model organic pollutant to evaluate the performance of an electrochemical advanced oxidation process. In conventional electro-Fenton process (pH 3), complete degradation was achieved in only 15 min at 10 mA cm-2, whereas at natural pH 5.9 and 33.3 mA cm-2, almost overall drug removal was reached in 120 min.

Atomically Dispersed Cobalt Anchored on Hollow Tubular Carbon Nitride Mediates Direct Electron Transfer and Oxygen-Related Active Species Path for Activation of Permonosulfate.

Atomically dispersed catalysts anchored on nitrogen-rich substrates present promising application potential for the persulfate-based advanced oxidation process. Nevertheless, efficient activation efficiency and a clear activated mechanism of persulfate remain challenging in carbon nitride-based single-atom catalysts (SACs). To these, combined with the regulation strategy of metal-ligand section and carrier's architecture, an atomically dispersed Co single-atom catalyst anchored on regular hollow tubular carbon nitride (Co/TCN SAC) herein was devised and utilized to activate permonosulfate. As a result, Co/TCN SACs show excellent catalytic performance for the degradation of common antibiotics. Combined with X-ray absorption fine structure and theory calculation, it is confirmed that superficially anchored CoO3 sites of the Co2N2O2-CoO3 unit are the catalytic active center for peroxymonosulfate (PMS) activation. The electrochemical test and in situ electron paramagnetic resonance results demonstrate radical (SO4•- and •OH) and nonradical (electron transfer process and 1O2) paths contributing to the superior catalytic performance. In addition, the catalyst exhibits high reaction efficiency and structural stability considering water quality parameters. Finally, a continuous and efficient device was operated on a laboratory scale, which exhibited satisfactory efficiency in continuously removing electron-rich antibiotics such as tetracycline. This work reveals the atomic-level modulation of cobalt atomic sites on hollow tubular carbon nitride and their structure-activity relationship with persulfate activation.

Comprehensive Insight into the Common Organic Radicals in Advanced Oxidation Processes for Water Decontamination.

Radical-based advanced oxidation processes (AOPs) are among the most effective technologies employed to destroy organic pollutants. Compared to common inorganic radicals, such as •OH, O2•-, and SO4•-, organic radicals are widespread, and more selective, but are easily overlooked. Furthermore, a systematic understanding of the generation and contributions of organic radicals remains lacking. In this review, we systematically summarize the properties, possible generation pathways, detection methods, and contributions of organic radicals in AOPs. Notably, exploring organic radicals in AOPs is challenging due to (1) limited detection methods for generated organic radicals; (2) controversial organic radical-mediated reaction mechanisms; and (3) rapid transformation of organic radicals as reaction intermediates. In addition to their characteristics and reactivity, we examine potential scenarios of organic radical generation in AOPs, including during the peroxide activation process, in water matrices or with coexisting organic pollutants, and due to the addition of quenching agents. Subsequently, we summarize various methods for organic radical detection as reported previously, such as electron paramagnetic resonance spectroscopy (EPR), 31P nuclear magnetic resonance spectroscopy (31P NMR), liquid/gas chromatography-mass spectroscopy (GC/LC-MS), and fluorescence probes. Finally, we review the contributions of organic radicals to decontamination processes and provide recommendations for future research.

The Dual Role of Natural Organic Matter in the Degradation of Organic Pollutants by Persulfate-Based Advanced Oxidation Processes: A Mini-Review

Persulfate-based advanced oxidation processes (PS-AOPs) are widely used to degrade significant amounts of organic pollutants (OPs) in water and soil matrices. The effectiveness of these processes is influenced by the presence of natural organic matter (NOM), which is ubiquitous in the environment. However, the mechanisms by which NOM affects the degradation of OPs in PS-AOPs remain poorly documented. This review systematically summarizes the dual effects of NOM in PS-AOPs, including inhibitory and promotional effects. It encompasses the entire process, detailing the interaction between PS and its activators, the fate of reactive oxygen species (ROS), and the transformation of OPs within PS-AOPs. Specifically, the inhibiting mechanisms include the prevention of PS activation, suppression of ROS fate, and conversion of intermediates to their parent compounds. In contrast, the promoting effects involve the enhancement of catalytic effectiveness, contributions to ROS generation, and improved interactions between NOM and OPs. Finally, further studies are required to elucidate the reaction mechanisms of NOM in PS-AOPs and explore the practical applications of PS-AOPs using actual NOM rather than model compounds.

Peroxymonosulfate activation over (Cu+ decorated g-C3N4)/Bi2WO6 composites with S-scheme heterojunction for RhB degradation

Catalytic activation of peroxymonosulfate (PMS) is one of the important research areas in the development of advanced oxidation technology for wastewater treatment. At present, the development of high-performance catalysts for PMS activation has become a research hotspot. Herein, (Cu+ decorated g-C3N4)/Bi2WO6 ((Cu+/g-C3N4)/Bi2WO6) composite was prepared successively by calcination and solvothermal method, which was used in visible light-assisted PMS activation for the degradation of rhodamine B (RhB). The construction of S-scheme heterojunctions between Cu+ decorated g-C3N4 and Bi2WO6 facilitated the activation of PMS, leading to a RhB degradation ratio of 98.46 % within 50 min. The corresponding reaction kinetic was significantly improved by a factor of 2.32 and 7.94 compared with that of CCN and BWO, respectively. The enhanced performance of the (Cu+/g-C3N4)/Bi2WO6 can be attributed to the successful construction of S-scheme heterojunction, which facilitates the separation of photogenerated carriers and accelerates the PMS activation to produce abundant active species. Furthermore, the (Cu+/g-C3N4)/Bi2WO6 composites exhibit strong stability and reusability following three cycles. In addition, the intermediates produced during the RhB degradation process were investigated by liquid chromatograph mass spectrometer (LC-MS). This study provides a new insight into the preparation of S-scheme photocatalysts for the photocatalytic-PMS activation system that will achieve efficient removal of dyes from wastewater.