Density Functional Theory Calculations for Insight into the Heterocatalyst Reactivity and Mechanism in Persulfate-Based Advanced Oxidation Reactions

Cu-O-Fe boosts electronic transport for efficient peroxymonosulfate activation over a wide range of pH

The transition metal-oxygen-transition metal (TM1-O-TM2) structural bonds served as electron transport bridges facilitates the charge flow, which guided developing bimetallic activators for peroxymonosulfate (PMS). In this work, a bimetallic CuO/Fe2O3 heterojunction with Cu-O-Fe bond in a core-shell structure was designed. The configuration enhanced PMS activation over a wide range of pH, as demonstrated by the degradation of the model contaminant sulfamethoxazole (SMX), particularly under acid and alkaline condition (>95 % within 30 min). Mechanistic investigations were conducted under various pH conditions. Cu(III) and 1O2 were the dominant active species at acid and alkaline condition, respectively, confirmed by DFT calculations, characterizations and experiments. The degradation pathway of SMX was speculated by mass spectrometry combined with calculations. In addition, the substrate guidance mechanism which was verified by 6 kinds of emerging contaminants (ECs) further highlights the excellence of the surveyed system. The potential for practical application was suggested, attributed to the excellent performance in SMX removal from raw river water (98.7 %), tap water (100 %) and domestic sewage (86.7 %). This study provides new prospect into PMS activation by bimetallic heterojunctions attributing to electronic transport via TM1-O-TM2 bond, which is significant for treating ECs in water.

In-situ preparation of highly dispersed Fe doping C3N5 induced by inorganic iron salts with effective activation of PMS for photocatalytic degradation of chlortetracycline

A highly dispersed Fe in situ doped C3N5 (Fe-C3N5) photocatalyst utilizing inorganic iron salt was successfully prepared, which was applied in photocatalytic synergistic advanced oxidative degradation of chlortetracycline (CTC) under the activation with persulfate. BET measurements revealed that uniform Fe doping increases the specific surface area, thus enhancing the reactive active sites. Photoelectric tests indicate that Fe doping optimizes the energy band structure of C3N5, thereby enhancing electron transfer, and the photogenerated electrons facilitate the Fe2+/Fe3+ redox cycle, which is beneficial for the sustained and efficient activation of persulfates. The Fe-C3N5(50 %)/PMS/Vis system achieved over 95 % degradation of CTC within 2 h, after four cycles, the Fe-C3N5(50 %) still exhibits good reusability and stability. Free radical quenching experiments coupled with EPR spectroscopy identified 1O2, h+, and ·O2- as the dominant reactive species driving the degradation of CTC, elucidating the potential degradation mechanisms. Based on LC-MS measurements and utilizing the TEST toxicity assessment software, it has been determined that CTC ultimately decomposes into non-toxic small molecules, such as CO2 and H2O. Furthermore, a hydroponic germination experiment using mung beans was conducted to demonstrate that Fe-C3N5(50 %) does not exhibit toxic effects on plant growth. Importantly, this study offers novel insights into the green synthesis of highly dispersed Fe doping C3N5 photocatalytic for the efficient degradation of CTC.

Concurrent redox reactions for perfluorocarboxylic acids decontamination via UV-activated tryptophan/carbon nanotubes

The contamination and persistence of Perfluorooctanoic Acid (PFOA) in aquatic environments have escalated environmental concerns, driving extensive research into effective decontamination strategies. To enhance the removal efficiency of PFOA via Advanced Reduction Processes (ARP) utilizing UV irradiation of tryptophan (Trp), carbon nanotubes (CNT) were incorporated, resulting in the development of a UV-Trp/CNT system. This novel process demonstrated a significant improvement in PFOA removal kinetics, as well as defluorination and Total Organic Carbon (TOC) reduction, and was effective across a broad spectrum of perfluoroalkyl carboxylic acids (PFCAs). In addition to the advanced reduction mechanism driven by hydrated electrons (eaq-), quenching experiments, material characterization, and chemical calculations indicated that CNTs facilitated the enrichment of Trp and PFOA, enabling electron transfer from PFOA to Trp via the CNT surface. This established a novel reaction pathway for PFOA oxidation coupled with ARP. The sequential defluorination of -CF₂- groups was facilitated by eaq-, while the electron transfer mechanism enabled oxidative decarboxylation, electron rearrangement, CC bond cleavage, and carbon chain shortening. These oxidative and reductive processes alternated systematically, advancing the development of a synergistic redox approach for the removal of PFCAs and inspiring further exploration into the use of carbon materials to construct confined domains and catalyze the degradation of PFASs.

Biodegradable porous adsorbent for efficient formaldehyde removal from indoor air

Prolonged formaldehyde exposure in indoor environments poses significant health risks. This study presents a biodegradable, cost-effective porous adsorbent engineered for efficient formaldehyde removal from indoor air. Comprising alginate, carboxymethyl cellulose, and attapulgite, the composite adsorbent leverages alginate and carboxymethyl cellulose to establish a stable porous framework, while attapulgite optimizes pore architecture. Polyethyleneimine was incorporated to introduce amino functional groups, thereby enhancing adsorption performance. At a polyethyleneimine concentration of 7 wt%, the adsorbent achieved a formaldehyde adsorption capacity of 2.31 mg/g, with a distribution coefficient quadrupling that of activated carbon at only 30 % of its cost. Adsorption kinetics conformed to a pseudo-second-order model, and isotherm analysis aligned with the Sips model, suggesting chemisorption as the predominant mechanism, complemented by physisorption. Moreover, the adsorbent demonstrated outstanding reusability and biodegradability, retaining 94.29 % of its initial capacity after four regeneration cycles and exhibiting a decomposition rate of 49 % after 30 days. This study provides a sustainable, high-performance solution for indoor formaldehyde removal with strong potential for practical applications.

Exploring the Structural Properties of Waste-Derived Carbon Nanomaterials for Enhanced Persulfate-Driven Advanced Oxidation Processes

The rapid accumulation of global solid waste poses a challenge to environmental health, human well-being, and resource sustainability. Solid waste, such as biomass and plastics, is increasingly recognized as a potential resource for producing functional materials. Through methods like pyrolysis, hydrothermal treatment, and chemical vapor deposition, solid waste can be upcycled into carbon-based catalysts for persulfate-driven advanced oxidation processes in environmental decontamination. This Perspective systematically explores waste-derived carbon nanomaterials for persulfate activation. Key structural and chemical factors influencing their catalytic behavior are evaluated, including carbon hybridization states (sp, sp2, and sp3), textural properties, oxygen-containing functional groups, structural defects, and heteroatom or metal doping. Special focus is given to how heteroatom/metal incorporation modulates the electronic structure, enabling persulfate activation through both radical and nonradical pathways. The novelty of this work lies in its integrated approach that bridges waste valorization and the rational design of functional catalysts. Consequently, this Perspective contributes to the advancement of sustainable and resource-efficient technologies for organic pollutant decontamination.

Leveraging Polaron Effect for Solar-Driven Efficient Peroxymonosulfate Activation in Water Purification

Peroxymonosulfate (PMS) represents a promising advanced oxidation technique for the treatment of refractory pollutants; however, its application is limited by high costs resulting from excessive usage due to low activation efficiency. In this study, we formulated a sunlight-driven Cu1-Ov/TiO2 catalyst with surface electron polaron sites to activate PMS for the degradation of contaminants, achieving a record reaction rate of k = 2.998 min-1 even with a low PMS dosage of 0.3 mM. The adsorption process and electron transfer kinetics were significantly enhanced with surface polaron sites in Cu1-Ov/TiO2, which facilitated the activation of PMS and increased the reaction rate constant k by 29.1 times compared with that of TiO2/PMS under illumination. Additionally, we verified that light irradiation promotes transfer from the non-free-radical pathway to the efficient free-radical pathway in mechanism of PMS activation. Our designed sunlight-driven flow-through PMS setup achieves a removal rate exceeding 90% for 7 days of outdoor operation at 3.2 × 102 L m-2 h-1, the feasibility of which is further proven in regions around the world by analysis of solar intensity. This study presents a demonstration of economical PMS application in water purification worldwide, with an estimated cost of 0.135 $ m-3.

State-Of-The-Art Structural Regulation Methods and Quantum Chemistry for Carbon-Based Single-Atom Catalysts in Advanced Oxidation Process: Critical Perspectives into Molecular Level

Advanced oxidation processes (AOPs) by carbon-based single-atom catalysts (SACs) are recognized as an attractive scientific frontier for water treatment, with the outstanding benefits of ultra-effective and anti-interference capability. However, most of the research has paid more attention to the performance of SACs, while the in-depth understanding of catalytic regulation by molecular interaction is relatively deficient. This critical review delves into deciphering the catalytic mechanism through a micro-level, which makes it more convenient to interpret apparent catalytic phenomena. It first summarizes basic theories of quantum chemistry, which provide mechanism interpretation and prediction for molecular-oxidation systems. Additionally, corresponding oxidation pathways of common oxidants are underscored. Following the oxidants, state-of-the-art regulation methods are discussed with special attention to involved molecular interactions and pollutants. Particularly, the preliminary insights into the "oxidant-catalyst-pollutants" internal relationships are provided to help construct the SAC-AOP system from a molecular standpoint. Meanwhile, some cutting-edge laboratory devices and pilot-scale engineering are presented to illustrate the ultimate purpose of scientific molecular exploration. Eventually, relative challenges of SACs-AOPs upon the design of catalytic systems and investigation methods are provided. This review aims to promote the large-scale potential of SACs-based AOPs in practical water treatment by emphasizing the pivotal role of micro-insights.

Enhanced Fe(III)/Fe(II) Cycle by Lattice Sulfur for Continuous Fenton Reactions

The Fenton reaction is usually limited by the sluggish regeneration of Fe(II). In this article, we developed a Fenton system that uses metal sulfides (MSx) and diluted Fe(III) to activate H2O2, and the enhanced mechanism of the Fe(III)/Fe(II) cycle in the presence of sulfides was investigated. The lattice sulfur of MSx can donate electrons to reduce Fe(III) into Fe(II) and is partially oxidized to SO42- during H2O2 activation. •OH and 1O2 are the primary reactive oxygen species for pollutant removal. Meanwhile, low-cost iron-based sulfide (FeSx) is selected for scale-up experiments in a fixed-bed reactor, which can maintain 100% atrazine degradation over 240 h. Additionally, the Fukui function is employed to analyze the selective degradation pathway of atrazine, and the biological toxicity of the organic intermediates is also assessed. The novel FeSx/Fe(III) system provides a potential alternative to the traditional Fenton reaction.

Biodegradable aminated alginate-chitosan porous polymer for efficient indoor formaldehyde capture

Formaldehyde, even at low concentrations, poses a significant indoor pollutant risk, underscoring the need for efficient and sustainable sorbents. This study introduces a novel, multifunctional, and fully biodegradable adsorbent derived from waste shrimp shells. The shells were converted into soluble chitosan, which was then physically crosslinked with branched amine-modified alginate, resulting in a porous biuret-modified alginate/chitosan (BCC) polymer. BCC, with a 6 wt% biuret content, demonstrated exceptional adsorption performance for low-concentration formaldehyde, achieving a capacity of 1.97 mg·g-1-159% higher than alginate and 149 % greater than activated carbon. The adsorption kinetics followed the pseudo-second-order model, and the Sips isotherm model suggested a chemical adsorption-dominated mechanism, with physical adsorption acting as a supplementary process. Additionally, BCC exhibited excellent reusability, maintaining high adsorption efficiency after four regeneration cycles, and incorporated a colorimetric signaling function, with a detection threshold of 0.07 mg·m-3 and a sensitivity of 0.02 mg·m-3. These findings provide valuable insights and a theoretical basis for developing effective, safe, and environmentally friendly formaldehyde adsorbents.

Amorphous Engineering Driving d-Orbital High Spin Configuration for Almost 100% 1O2-Mediated Fenton-Like Reactions

The inherent atomic disorder in amorphous materials leads to unsaturated atomic sites or dangling bonds, effectively modulating the material's electronic states and rendering it an ideal platform for the growth of single atoms. Herein, the electronic structure of isolated cobalt atoms anchored on amorphous carbon nitride (Co-ACN) is modulated through a substrate amorphization engineering, enabling the thorough removal of pazufloxacin (PZF) in 1 min with a high reaction rate constant (k1) of 3.504 min-1 by peroxymonosulfate (PMS) activation. Experiments and theoretical calculations reveal that Co-ACN exhibited a higher coordination environment (Co-N3) compared to crystalline Co-CCN (Co-N2). Meanwhile, the t2g energy level enhancement of Co 3d orbital promotes electron transition from t2g to eg, inducing more unpaired electrons and thereby driving the transition from a low-spin state (LS, t2g 6eg 1) to a high-spin state (HS, t2g 5eg 2). The HS Co-ACN optimized the d-band center, boosted the electronic transfer, and weakened the interaction between Co 3d and O 2p orbitals of HSO5 -, thereby enabling nearly 100% selective singlet oxygen (1O2) generation, whereas Co-CCN yielded coexisting reactive oxygen species (ROS). This work opens up a new paradigm for regulating the electronic structure of single-atom catalysts at the atomic scale.

Elucidating the Functional Orbital Evolution in Transition Metal-Doped Bi3O4Br Platforms for CO2 Photoreduction

Frontier orbital hybridization plays a vital role in the initial adsorption and activation process during catalysis. A formidable challenge is the precise determination of active orbitals/sites. Herein, 2D Bi3O4Br nanosheets are adopted as an operable platform for heteroatom doping of various transition metals (Fe, Ni, Zn/Cd). As the atom number of dopants increases, the capability of selective CO2 photoconversion is continuously amplified. The intrinsic nature is the variation of active functional orbital as indicated from band center distance (Δd/p-p) indicators. The calculated charge transfer of various CO2-bound geometries further demonstrates the p-p orbital interaction overwhelms d-p orbital interaction. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy results verify the charged nature of Bi sites with 6p orbitals not fully filled by electrons. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis and Gibbs free energy change profile suggest the rapid emergence of the critical *COOH intermediate in a thermodynamically preferred pathway.

Cascade Electric Field in ZnIn2S4/CuCo2O4 Photocatalyst for the Selective Oxidation of Biomass-Derived 5-Hydroxymethylfurfural in Aqueous Solutions

The photocatalytic conversion of biomass feedstock represents a promising and environmentally friendly strategy for achieving selective transformation and value addition. The slow charge dynamics and sluggish hole transfer in the oxidation reactions severely limit the photocatalytic activity. Here, the heterojunction is fabricated by synthesizing ultra thin ZnIn2S4 nanoflower with spinel CuCo2O4. The internal and interfacial electric fields are successfully constructed, which shows superior 5-hydroxymethylfurfural (HMF) valorization. HMF undergoes severe mineralization when ZnIn2S4 is used as the catalyst, resulting in 0.9% 2,5-diformylfuran (DFF) yield in water, while the ZnIn2S4/CuCo2O4 heterojunction catalyst exhibits 77% DFF selectivity with 88.6% HMF conversion, The cascaded bulk and internal electric fields greatly reduce the oxidation potential of holes and enhance the charge separation efficiency, thus give a remarkable 70-fold increase in DFF yield. This work overcomes the limitations of ZnIn2S4 application for HMF and similar alcohol oxidation reactions that typically require organic solvents, achieving a high DFF evolution rate of 724.9 µmol·g-1·h-1 in water within the first hour of the reaction, surpassing most reports of photocatalytic HMF selective oxidation.

Heterogeneous Peroxymonosulfate-Based Advanced Oxidation Mechanisms: New Wine in Old Bottles?

Heterogeneous persulfate-based advanced oxidation processes (PS-AOPs) have been gaining significant attention in water/wastewater treatment; however, the elucidation of mechanisms in PS-AOPs has become increasingly complex as the understanding of potential reactive pathways expands and the rigor of corresponding characterizations intensifies. As such, accurately illustrating system mechanisms with a robust and convincing methodology is crucial, while the influence of substrates must not be overlooked. In this Perspective, established techniques and critical issues are systematically compiled to serve as practical guidelines. Additionally, a newly proposed pathway, the direct oxidation transfer process (DOTP), is discussed in comparison to conventional mineralization processes by reactive oxidative species (ROS) in PS-AOPs. Overall, the investigation of PS-AOP mechanisms across various heterogeneous systems remains contentious and calls for standardization, for which this work aims to serve as a valuable reference.

Microplastic types dominate the effects of bismuth oxide semi-conductor nanoparticles on their transport in saturated quartz sand

The transport of microplastics (MPs) is of great significance due to its potential threat to subsurface systems. The copresence of MPs and semi-conductor nanoparticles is quite common in practical environments (i. e. in electronic/electrical waste disposal sites). To date, the influence of bismuth oxide (Bi2O3) semi-conductor nanoparticles on MPs transport in porous media has still been rarely and explicitly explored. Therefore, the effect of Bi2O3 on the transport of distinct types of MPs were investigated using column experiments. The MPs included 0.51 μm and 1.1 μm polystyrene (PS), 1 μm polyethylene terephthalate (PET) and 1 μm polyethylene (PE) MPs. Mechanisms for the differently altered transport of various MPs with Bi2O3 were further elucidated. It was verified that the deposited Bi2O3 on sand surfaces could contribute to the decreased transport of PET and PE MPs by column experiments with pre-treatment. Moreover, scanning electron microscopy (SEM), dynamic light scattering (DLS) measurements, and electrochemical Nyquist curves demonstrated that the interaction of PE and PET MPs with Bi2O3 was more pronounced than that of PS MPs, especially for PE MPs. In addition, density functional theory (DFT) calculations combined with adsorption experiments further confirmed that the adsorption between PE MPs and Bi2O3 was the strongest, which then contributed to the highest decrease of PE MPs transport. This study highlighted that the MPs types might be the major factor controlling its interaction with copresent substances, thereby affecting its fate and transport in soil systems.

Development of New Dual-Purpose Environmental Strategies for Effective Antibiotic Degradation Using Red Mud-Based Fenton Oxidation Catalysts

Mitigating antibiotic pollution is essential to combating antibiotic resistance, safeguarding ecosystems, ensuring food and water safety, and preserving the efficacy of antibiotics. Simultaneously, the comprehensive utilization of red mud is a key approach to reducing resource waste and ecological damage. This study investigates the use of iron components from red mud to prepare RM-nZVI/Ni for Fenton-like reactions, aimed at degrading antibiotics in water. By leveraging the inherent iron content in red mud, RM-nZVI/Ni was developed to achieve a dual-purpose environmental strategy: antibiotic degradation and solid waste resource recycling. The results demonstrate that 0.02 g/L of sulfamethoxazole (SMX) can be fully degraded within 15 min using 0.1 g/L of RM-nZVI/Ni and 6 mM of H2O2. Hydroxyl radicals (·OH) and Ni were identified as key contributors to SMX removal. Moreover, this system exhibits universality in degrading common antibiotics such as LFX, NFX, CIP, and TC. LC-MS analysis and DFT theoretical calculations indicate that the degradation byproducts are of lower toxicity or are non-toxic. Additionally, cost analysis suggests that RM-nZVI/Ni is a cost-effective and efficient catalyst. This research gives valuable insights into antibiotic degradation using red mud-based catalysts and offers guidance for expanding the high-value applications of red mud.

Carbonaceous materials in structural dimensions for advanced oxidation processes

Carbonaceous materials have attracted extensive research and application interests in water treatment owing to their advantageous structural and physicochemical properties. Despite the significant interest and ongoing debates on the mechanisms through which carbonaceous materials facilitate advanced oxidation processes (AOPs), a systematic summary of carbon materials across all dimensions (0D-3D nanocarbon to bulk carbon) in various AOP systems remains absent. Addressing this gap, the current review presents a comprehensive analysis of various carbon/oxidant systems, exploring carbon quantum dots (0D), nanodiamonds (0D), carbon nanotubes (1D), graphene derivatives (2D), nanoporous carbon (3D), and biochar (bulk 3D), across different oxidant systems: persulfates (peroxymonosulfate/peroxydisulfate), ozone, hydrogen peroxide, and high-valent metals (Mn(VII)/Fe(VI)). Our discussion is anchored on the identification of active sites and elucidation of catalytic mechanisms, spanning both radical and nonradical pathways. By dissecting catalysis-related factors such as sp2/sp3 C, defects, and surface functional groups that include heteroatoms and oxygen groups in different carbon configurations, this review aims to provide a holistic understanding of the catalytic nature of different dimensional carbonaceous materials in AOPs. Furthermore, we address current challenges and underscore the potential for optimizing and innovating water treatment methodologies through the strategic application of carbon-based catalysts. Finally, prospects for future investigations and the associated bottlenecks are proposed.

Effect of persulfate dosage on organic degradation using N-doped biochar: Reaction pathway and environmental implications

Persulfate-based advanced oxidation processes (PS-AOPs) catalyzed by carbon-based catalysts are promising for removing organic pollutants via radical/non-radical pathways. However, the activation efficiency of peroxymonosulfate (PMS) or peroxydisulfate (PDS) usage and the reaction mechanism remain insufficiently understood. In this study, the effects of PMS/PDS dosage on the degradation of bisphenol A (BPA, 10 mg/L) were evaluated using N-doped biochar (N-BC, 0.2 g/L) assisted PS-AOPs. The reaction pathways were comprehensively investigated through a combination of characterization techniques and molecular simulations. With low PS dosages (0.05 and 0.1 mM), the degradation rate constants (k obs $$ {k}_{obs} $$ ) were higher in N-BC/PDS (0.04 and 0.07 min-1) compared to N-BC/PMS (0.02 and 0.04 min-1), likely due to higher PDS utilization, which enhanced the contribution of the non-radical pathway. Interestingly, with higher PS dosages (0.5 and 1.5 mM), thek obs $$ {k}_{obs} $$ values were 0.16 min-1 and 0.18 min-1 in N-BC/PMS, respectively, significantly exceeding those determined in N-BC/PDS (0.11 and 0.11 min-1). This result stemmed from the greater adsorption capacity of N-BC for PMS compared to PDS, leading to increased formation of 1O2. The contribution of non-radical pathways for both PMS and PDS increased with higher PS dosage. The results highlighted that BPA degradation improved significantly with the increase in PMS dosage; meanwhile, BPA degradation was insensitive to PDS dosage. The optimal PMS dosage for BPA degradation was found to be 1.5 mM and 0.1 mM for PDS. This study offered valuable insights for optimizing PS-AOPs in environmental remediation, helping to guide the selection of appropriate oxidants and dosages for maximizing pollutant removal. PRACTITIONER POINTS: Effect of PMS/PDS dosage on BPA degradation by N-doped biochar was revealed. Contribution of dominated non-radical pathway increased as PMS/PDS dosage increased. The greater PDS utilization and non-radical pathway resulted in the higherk obs $$ {k}_{obs} $$ at low dosage. N-BC adsorbed more PMS than PDS, leading to an increase ink obs $$ {k}_{obs} $$ at high dosage.

Controlling the amount of MoSe2 loaded SrTiO3 to activate peroxymonosulfate for efficient elimination of organic pollutants

It is critical to effectively eliminate recalcitrant organic pollutants from wastewater. In this paper, the MoSe2/SrTiO3 (MST) catalysts were synthesized through simply controlling the amount of MoSe2 in the hydrothermal method to activate peroxymonosulfate (PMS) for the degradation of pollutants. The results demonstrated that sulfamethoxazole and tetracycline were almost eliminated by PMS/MST-3 (MoSe2/SrTiO3 mass ratio 0.3: 1) activation system. The effect of inorganic anions (Cl -, H2PO4 -, HCO3 -) and metal ions (Cu2+, Ni2+, Zn2+) commonly found in actual water bodies on catalytic reaction was explored. Moreover, SO4• -, •OH and 1O2 were identified by EPR tests and scavenger experiments, where the SO4• - and •OH were the dominant reactive species. The XPS analysis indicated that the oxygen vacancies and charge transfer on the catalyst surface were the keys of PMS activation. The effect of active sites in SMX and TC on the catalytic degradation activity was explored by density functional theory, and it was obtained that the central nitrogen site of SMX was more vulnerable in the catalytic system, while the edge oxygen site of TC was more susceptible to attack.

Transforming Plastics to Single Atom Catalysts for Peroxymonosulfate Activation: Axial Chloride Coordination Intensified Electron Transfer Pathway

Transforming plastics into single-atom catalysts is a promising strategy for upcycling waste plastics into value-added functional materials. Herein, a graphene-based single-atom catalyst with atomically dispersed FeN4Cl sites (Fe─N/Cl─C) is produced from high-density polyethylene wastes via one-pot catalytic pyrolysis. The Fe─N/Cl─C catalyst exhibited much higher turnover frequency and surface area normalized activity (Kac) compared with the Fe─N─C catalyst without axial Cl modulation. Both experiments and density functional theory (DFT) computations demonstrated that the axial incorporation of chloride fine-tuned the coordination environment of FeN4 sites and enhanced peroxymonosulfate (PMS) activation because of improved conductivity and modulated spin state. In situ, Raman, and infrared spectroscopic techniques revealed that PMS is activated by the Fe─N/Cl─C catalyst through an electron transfer process. The formation of a key PMS* intermediate at the Fe site effectively elevated the redox capacity of the catalyst surface to realize a fast degradation of diverse pollutants. The non-radical oxidation manner secures high selectivity toward target pollutants and high chemical utilization efficiency. A continuous operation in a column reactor also demonstrated the high efficiency and stability of the (Fe─N/Cl─C + PMS) system for practical water treatment.

Significantly suppressing CO release achieved by the catalysis effect of nanostructured rare earth/manganese oxides: Application in flame retardant thermoplastic polyurethane

There is significant smoke and toxic volatiles generated from the combustion of thermoplastic polyurethane (TPU), which has compromised its application and posed a significant threat to human life. Here, the hydrothermal-citrate complexation method synthesised the rare earth Mn-based composite catalyst and blended with TPU to mitigate smoke release and toxic gas generation during TPU combustion. The results demonstrate that the inclusion of 3 wt% Mn-La and Mn-Ce catalysts into TPU leads to a 41.3% and 33.6% decrease in maximum smoke density (Ds max), respectively, along with a 52.4% and 50.5% reduction in peak CO production rate (pCOPR). The mechanism of rare earth Mn-based catalyst-based smoke suppression and toxicity reduction in TPU is explained at a microscopic scale based on density functional theory (DFT) research: the introduction of catalyst bolsters the adsorption of O2 and CO on the surface of TPU nanocomposites and facilitates the oxidation of CO. Additionally, it can expedite the formation of dense carbon layers and impede heat and mass transfer. The TPU nanocomposites exhibit excellent flame retardancy and effective smoke suppression. A feasible strategy for manufacturing fire-safety TPU nanocomposites with favorable comprehensive properties is proposed.

Trimetallic MOF-derived Fe-Mn-Sn oxide heterostructure enabling exceptional catalytic degradation of organic pollutants

Developing efficient and environmentally benign heterogeneous catalysts that activate peroxymonosulfate (PMS) for the degradation of persistent organic contaminants remains a challenge. Metal-organic frameworks (MOFs)-derived metal oxide catalysts in advanced oxidation processes (AOPs) have received considerable attention research fraternity. Herein, we report an innovative magnetic trimetallic MOF-derived Fe-Mn-Sn oxide heterostructure (FeMnO@Sn) with adjustable morphology, size and Sn content, prepared through an impregnation-calcination strategy. The formation of a novel magnetic Fe2O3/Fe3O4/Mn3O4 heterostructure induces the generation of abundant Fe2+ and Mn2+ sites on the FeMnO@Sn surface. Meanwhile, the introduction of SnO2 into the Fe2O3/Fe3O4/Mn3O4 heterostructure facilitates the cleavage of the OO bond in adsorbed PMS. The synergy among the different functionalities of each metal oxide plays a vital role in the swift and effective degradation of pollutants. In addition, the uniquely designed catalyst exhibits magnetic properties that facilitate easy recycling and repeated use, thereby meeting environmental protection requirements. Overall, this research highlights the design of heterogeneous catalysts for the effective activation of PMS and provides valuable insights for the advancement of future environmental catalysts.

Graphene-based electrochemical sensors for antibiotics: sensing theories, synthetic methods, and on-site monitoring applications

Owing to the extensive use of antibiotics for treating infectious diseases in livestock and humans, the resulting residual antibiotics are a burden to the ecosystem and human health. Hence, for human health and ecological safety, it is critical to determine the residual antibiotics with accuracy and convenience. Graphene-based electrochemical sensors are an effective tool to detect residual antibiotics owing to their advantages, such as, high sensitivity, simplicity, and time efficiency. In this work, we comprehensively summarize the recent advances in graphene-based electrochemical sensors used for detecting antibiotics, including modifiers for electrode fabrication, theoretical elaboration of electrochemical sensing mechanisms, and practical applications of portable electrochemical platforms for the on-site monitoring of antibiotics. It is anticipated that the current review will be a valuable reference for comprehensively comprehending graphene-based electrochemical sensors and further promoting their applications in the fields of healthcare, environmental protection, and food safety.

Surface acoustic wave platform integrated with ultraviolet activated rGO-SnS2 nanocomposites to achieve ppb-level dimethyl methylphosphonate detection at room-temperature

Dimethyl methylphosphonate (DMMP) is commonly used as an alternative for demonstrating to detect sarin, which is one of the most toxic but odorless chemical nerve agents. Among various types of DMMP sensors, those utilizing surface acoustic wave (SAW) technology provide notable advantages such as wireless/passive monitoring, digital output, and a compact, portable design. However, key challenges for SAW-based DMMP sensors operated at room temperature lies in simultaneous enhancement of sensitivities and reduction of detection limits. In this study, we developed a binary material strategy by combining reduced graphene oxide (rGO) and tin disulfide (SnS2) with (100)-facets orientation as sensing layers of SAW device for DMMP detection utilized at room temperature. Ultraviolet (UV) light was applied to activate the sensitive film and reduce the sensor's response time. The developed SAW DMMP sensor demonstrated a superior sensitivity (-1298.82 Hz/ppm), a low detection limit of 50 ppb, and a hysteresis below 1.5%, along with fast response/recovery time (39.2 s/28.4 s), excellent selectivity, long-term stability and repeatability. The formation of shrub-like rGO-SnS2 heterojunctions with abundant surface defects and large specific surface areas, high-energy (100) crystalline surfaces of SnS2, and photogenerated carriers generated by UV irradiation were pinpointed as the crucial sensing mechanisms. These factors collectively enhanced adsorption and reaction dynamics of DMMP molecules.

Co-catalysis strategy for low-oxidant-consumption Fenton-like chemistry: From theoretical understandings to practical applications and future guiding strategies

Recently, great effects have been made for the co-catalysis strategy to solve the bottlenecks of Fenton system. A series of co-catalysis strategies using various inorganic metal co-catalysts and organic co-catalysts have been developed in various oxidant (i.e., hydrogen peroxide (H2O2) and persulfate) systems with significantly promotion of catalytic performances and lower oxidant consumption (only 5-10 % of conventional Fenton/Fenton-like systems). However, the developments of these co-catalysis strategies from theoretical understandings to practical applications and future guiding strategies were overlooked, which was an essential problem that must be considered for the future scale-up applications of co-catalysis systems. In this paper, these co-catalysis strategies with low-oxidant-consumption characteristics have been reviewed by the comparison of their co-catalysis mechanisms, as well as their advantages and disadvantages. We also discussed the recent developments of amplifying devices based on the co-catalysis systems. The scale-up performances of co-catalysis strategies based on these amplifying devices have also been assessed. In addition, future guiding strategies for the development of co-catalysis strategy with low-oxidant-consumption characteristics have also been first time outlined by the combination of the technical-economic analysis (TEA), life cycle assessment (LCA) and machine learning (ML). Finally, the paper systematically discusses the development opportunities, technical bottlenecks and future development directions of co-catalysis strategies with the prospect of large-scale applications. Basically, this work provides a systematic review on co-catalysis strategy with low-oxidant-consumption characteristic from theoretical understandings to practical applications and future guiding strategies.

Electrochemically Assisted Cobalt/MXene Membrane for Effective Water Treatment: Synchronously Improving Catalytic Performance and Anti-Interference Ability

Catalytic membrane technology for water treatment is often constrained by a trade-off between permeability and catalytic efficiency as well as interference from coexisting anions and organic matter in natural water matrices. Herein, a novel cobalt-loaded MXene (Co/MXene) 2D membrane with good hydrophilicity, electrical conductivity, and PMS activation function is constructed. The negative voltage is exerted on the membrane to significantly enhance its PMS activation efficiency and anti-interference capacity toward effective water treatment. Under -2 V, the optimal Co/MXene catalytic membrane displays 100% rhodamine b (RhB) removal within a residence time of only 1.1 s, whose RhB degradation kinetic constant (k of 6.85 s-1) is 17.6 times higher than that of the Co/MXene catalytic membrane alone and is also greatly superior to other advanced catalysts and catalytic membranes. Meanwhile, the catalytic membrane displays obvious anti-interference ability in the presence of various coexisting substances of the water matrix and performs well in treating the secondary effluent of coking wastewater. The radical-dominated (SO4•- and •OH) mechanism accompanied by the nonradical species (1O2 and Co(VI)═O) is revealed in the system, and the reactive species production is obviously enhanced under negative voltage. Experimental results and theoretical calculations jointly confirm the key role of electrochemical assistance in enhancing membrane performance, which not only facilitates cycling of Co3+/Co2+ for enhanced PMS activation via improving PMS adsorption and promoting charge transfer from Co to PMS but also hinders interference from coexisting substances in water via electrostatic repulsion.

Low-coordinated Mn-N2 sites in graphene oxide induce peroxydisulfate activation for tetracycline degradation: Process optimization and theoretical calculation

Atom-dispersed low-coordinated transition metal-Nx catalysts exhibit excellent efficiency in activating peroxydisulfate (PDS) for environmental remediation. However, their catalytic performance is limited due to metal-N coordination number and single-atom loading amount. In this study, low-coordinated nitrogen-doped graphene oxide (GO) confined single-atom Mn catalyst (Mn-SA/NGO) was synthesized by molten salt-assisted pyrolysis and coupled to PDS for degradation of tetracycline (TC) in water. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and X-ray absorption fine structure spectroscopy (XAFS) analysis showed the successful doping of single-atom Mn (weight percentage 1.6%) onto GO and the formation of low-coordinated Mn-N2 sites. The optimized parameters obtained by Box-Behnken Design achieved 100% TC removal in both prediction and experimental results. The Mn-SA/NGO + PDS system had strong anti-interference ability for TC removal in the presence of anions. Besides, Mn-SA/NGO possessed good reusability and stability. O2•-, •OH, and 1O2 were the main active species for TC degradation, and the TC mineralization reached 85.1%. Density functional theory (DFT) calculations confirmed that the introduction of single atoms Mn could effectively enhance adsorption and activation of PDS. The findings provide a reference for the synthesis of high-performance single-atom catalysts for effective removal of antibiotics.

Microenvironment Engineering of Heterogeneous Catalysts for Liquid-Phase Environmental Catalysis

Environmental catalysis has emerged as a scientific frontier in mitigating water pollution and advancing circular chemistry and reaction microenvironment significantly influences the catalytic performance and efficiency. This review delves into microenvironment engineering within liquid-phase environmental catalysis, categorizing microenvironments into four scales: atom/molecule-level modulation, nano/microscale-confined structures, interface and surface regulation, and external field effects. Each category is analyzed for its unique characteristics and merits, emphasizing its potential to significantly enhance catalytic efficiency and selectivity. Following this overview, we introduced recent advancements in advanced material and system design to promote liquid-phase environmental catalysis (e.g., water purification, transformation to value-added products, and green synthesis), leveraging state-of-the-art microenvironment engineering technologies. These discussions showcase microenvironment engineering was applied in different reactions to fine-tune catalytic regimes and improve the efficiency from both thermodynamics and kinetics perspectives. Lastly, we discussed the challenges and future directions in microenvironment engineering. This review underscores the potential of microenvironment engineering in intelligent materials and system design to drive the development of more effective and sustainable catalytic solutions to environmental decontamination.

Advances in the Removal of Organic Pollutants from Water by Photocatalytic Activation of Persulfate: Photocatalyst Modification Strategy and Reaction Mechanism

Environmental pollution caused by persistent organic pollutants has imposed big threats to the health of human and ecological systems. The development of efficient methods to effectively degrade and remove these persistent organic pollutants is therefore of paramount importance. Photocatalytic persulfate-based advanced oxidation technologies (PS-AOTs), which depend on the highly reactive SO4 - radicals generated by the activation of PS to degrade persistent organic pollutants, have shown great promise. This work discusses the application and modification strategies of common photocatalysts in photocatalytic PS-AOTs, and compares the degradation performance of different catalysts for pollutants. Furthermore, essential elements impacting photocatalytic PS-AOTs are discussed, including the water matrix, reaction process mechanism, pollutant degradation pathway, singlet oxygen generation, and potential PS hazards. Finally, the existing issues and future challenges of photocatalytic PS-AOTs are summarized and prospected to encourage their practical application. In particular, by providing new insights into the PS-AOTs, this review sheds light on the opportunities and challenges for the development of photocatalysts with advanced features for the PS-AOTs, which will be of great interests to promote better fundamental understanding of the PS-AOTs and their practical applications.

Reviving Sodium Tunnel Oxide Cathodes Based on Structural Modulation and Sodium Compensation Strategy Toward Practical Sodium-Ion Cylindrical Battery

As a typical tunnel oxide, Na0.44MnO2 features excellent electrochemical performance and outstanding structural stability, making it a promising cathode for sodium-ion batteries (SIBs). However, it suffers from undesirable challenges such as surface residual alkali, multiple voltage plateaus, and low initial charge specific capacity. Herein, an internal and external synergistic modulation strategy is adopted by replacing part of the Mn with Ti to optimize the bulk phase and construct a Ti-containing epitaxial stabilization layer, resulting in reduced surface residual alkali, excellent Na+ transport kinetics and improved water/air stability. Specifically, the Na0.44Mn0.85Ti0.15O2 using water-soluble carboxymethyl cellulose as a binder can realize a capacity retention rate of 94.30% after 1,000 cycles at 2C, and excellent stability is further verified in kilogram large-up applications. In addition, taking advantage of the rich Na content in Prussian blue analog (PBA), PBA-Na0.44Mn1-xTixO2 composites are designed to compensate for the insufficient Na in the tunnel oxide and are matched with hard carbon to achieve the preparation of coin full cell and 18650 cylindrical battery with satisfactory electrochemical performance. This work enables the application of tunnel oxides cathode for SIBs in 18650 cylindrical batteries for the first time and promotes the commercialization of SIBs.

Revealing the Synergistic Effect of Cation and Anion Vacancies on Enhanced Fenton-Like Reaction: The Electron Density Modulation of O 2p-Co 3d Bands

Defect engineering is considered as a flexible and effective mean to improve the performance of Fenton-like reactions. Herein, a simple method is employed to synthesize Co3O4 catalysts with Co-O vacancy pairs (VP) for peroxymonosulfate (PMS) activation. Multi-scaled characterization, experimental, and simulation results jointly revealed that the cation vacancies-VCo contributed to enhanced conductivity and anion vacancies-VO provided a new active center for the 1O2 generation. Co3O4-VP can optimize the O 2p and Co 3d bands with the strong assistance of synergistic double vacancies to reduce the reaction energy barrier of the "PMS → Co(IV) = O → 1O2" pathway, ultimately triggering the stable transition of mechanism. Co3O4-VP catalysts with radical-nonradical collaborative mechanism achieve the synchronous improvement of activity and stability, and have good environmental robustness to favor water decontamination applications. This result highlights the possibility of utilizing anion and cation vacancy engineering strategies to rational design Co3O4-based materials widely used in catalytic reactions.

Interaction characteristics and mechanism of Cr(VI)/Cr(III) with microplastics: Influence factor experiment and DFT calculation

The coexistence of highly toxic heavy metal chromium and new pollutants microplastics has been widely present, and the interaction behavior and mechanism of the two are crucial for their environmental effects in coexisting environments, which urgently need to be further explored. Firstly, the interaction characteristics of polyamide (PA) and polyethylene (PE) with Cr(VI)/Cr(III) were investigated, where PA exhibited higher adsorption capacity of both Cr(VI) and Cr(III) than PE among various environmental conditions. The higher adsorption energy of PA on Cr(VI)/Cr(III) was also achieved by DFT calculation, and the bending configuration of PA during the adsorption process may be beneficial for its interaction with Cr. Then, the combination of characterization analysis and DFT calculation showed that significant chemical bonding occurred in the interaction between CO bond of PA and Cr(III), weak chemical interactions occurred in the adsorption of PE with Cr(III) and PA with Cr(VI), while the adsorption of PE with Cr(VI) was mainly physical effects. This study provides theoretical support for pollution control of microplastics and chromium in co-existing environment.

The Surface Confinement of FeO Assists in the Generation of Singlet Oxygen and High-Valent Metal-Oxo Species for Enhanced Fenton-Like Catalysis

Transition metal compounds (TMCs) have long been potential candidate catalysts in persulfate-based advanced oxidation process (PS-AOPs) due to their Fenton-like catalyze ability for radical generation. However, the mechanism involved in TMCs-catalyzed nonradical PS-AOPs remains obscure. Herein, the growth of FeO on the Fe3O4/carbon precursor is regulated by restricted pyrolysis of MIL-88A template to activate peroxymonosulfate (PMS) for tetracycline (TC) removal. The higher FeO incorporation conferred a 2.6 times higher degradation performance than that catalyzed by Fe3O4 and also a higher interference resistance to anions or natural organic matter. Unexpectedly, the quenching experiment, probe method, and electron paramagnetic resonance quantitatively revealed that the FeO reassigned high nonradical species (1O2 and FeIV═O) generation to replace original radical system created by Fe3O4. Density functional theory calculation interpreted that PMS molecular on strongly-adsorbed (200) and (220) facets of FeO enjoyed unique polarized electronic reception for surface confinement effect, thus the retained peroxide bond energetically supported the production of 1O2 and FeIV═O. This work promotes the mechanism understanding of TMCs-induced surface-catalyzed persulfate activation and enables them better perform catalytic properties in wastewater treatment.

Promoting Electrocatalytic Oxygen Reactions Using Advanced Heterostructures for Rechargeable Zinc-Air Battery Applications

In order to facilitate electrochemical oxygen reactions in electrically rechargeable zinc-air batteries (ZABs), there is a need to develop innovative approaches for efficient oxygen electrocatalysts. Due to their reliability, high energy density, material abundance, and ecofriendliness, rechargeable ZABs hold promise as next-generation energy storage and conversion devices. However, the large-scale application of ZABs is currently hindered by the slow kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). However, the development of heterostructure-based electrocatalysts has the potential to surpass the limitations imposed by the intrinsic properties of a single material. This Account begins with an explanation of the configurations of ZABs and the fundamentals of the oxygen electrochemistry of the air electrode. Then, we summarize recent progress with respect to the variety of heterostructures that exploit bifunctional electrocatalytic reactions and overview their impact on ZAB performance. The range of heterointerfacial engineering strategies for improving the ORR/OER and ZAB performance includes tailoring the surface chemistry, dimensionality of catalysts, interfacial charge transfer, mass and charge transport, and morphology. We highlight the multicomponent design approaches that take these features into account to create advanced highly active bifunctional catalysts. Finally, we discuss the challenges and future perspectives on this important topic that aim to enhance the bifunctional activity and performance of zinc-air batteries.

Advanced Characterization Techniques and Theoretical Calculation for Single Atom Catalysts in Fenton-like Chemistry

Single-atom catalysts (SACs) have attracted extensive attention due to their unique catalytic properties and wide range of applications. Advanced characterization techniques, such as energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and X-ray absorption fine-structure spectroscopy, have been used to investigate the elemental compositions, structural morphologies, and chemical bonding states of SACs in detail, aiming at unraveling the catalytic mechanism. Meanwhile, theoretical calculations, such as quantum chemical calculations and kinetic simulations, were used to predict the catalytic reaction pathways, active sites, and reaction kinetic behaviors of SACs, providing theoretical guidance for the design and optimization of SACs. This review overviews advanced characterization techniques and theoretical calculations for SACs in Fenton-like chemistry. Moreover, this work highlights the importance of advanced characterization techniques and theoretical calculations in the study of SACs and provides perspectives on the potential applications of SACs in the field of environmental remediation and the challenges of practical engineering.

A comprehensive review of the "black gold catalysts" in wastewater treatment: Properties, applications and bibliometric analysis

A significant amount of effort has been devoted to the utilization of biochar-based catalysts in the treatment of wastewater. By virtue of its abundant functional groups and high specific surface area, biochar holds significant promise as a catalyst. This article presents a comprehensive systematic review and bibliometric analysis covering the period from 2009 to 2024, focusing on the restoration of wastewater through biochar catalysis. The production, activation, and functionalization techniques employed for biochar are thoroughly examined. In addition, the application of advanced technologies such as advanced oxidation processes (AOPs), catalytic reduction reactions, and biochemically driven processes based on biochar are discussed, with a focus on elucidating the underlying mechanisms and how surface functionalities influence the catalytic performance of biochar. Furthermore, the potential drawbacks of utilizing biochar are also brought to light. To emphasize the progress being made in this research field and provide valuable insights for future researchers, a scientometric analysis was conducted using CiteSpace and VOSviewer software on 595 articles. Hopefully, this review will enhance understanding of the catalytic performance and mechanisms pertaining to biochar-based catalysts in pollutant treatment while providing a perspective and guidelines for future research and development efforts in this area.

Stability of Nitrogen-Doped Activated Carbon as an Electrocatalyst for the Oxygen Reduction Reaction in Various Storage Media

Besides outstanding catalytic performance, the stability of nitrogen-doped carbon materials during storage is equally crucial for practical applications. Therefore, we conducted the first investigation into the stability of highly nitrogen-doped activated carbon (AC-NC-T) obtained by modifying activated carbon with CO2/NH3 in different storage media (air, vacuum and N2). The results of the catalysis of the oxygen reduction reaction and the activation of peroxymonosulfate for degrading bisphenol A by AC-NC-T show that the catalytic activity of AC-NC-T stored in air decays most prominently, while the performance attenuated only marginally when stored in vacuum and N2. The results from N2 adsorption isotherms, Raman spectroscopy, elemental and X-ray photoelectron spectroscopy indicate that the decline in catalytic activity is due to the presence of oxygen in the environment, causing a decrease in absolute contents of pyridinic N (N-6) and graphitic nitrogen (N-Q). After being stored in an air atmosphere for 28 days, the absolute contents of N-6 and N-Q in AC-NC-950 decreased by 19.3% and 12.1%, respectively. However, when stored in a vacuum or N2, the reduction in both was less than 7%. This study demonstrates that reducing oxygen concentration during storage is crucial for preserving high catalytic activity of nitrogen-containing carbon materials.

Qualitative and quantitative analysis of electrons donated by pollutants in electron transfer-based oxidation system: Electrochemical measurement and theoretical calculations

In order to gain a profound understanding of the fate of pollutants in advanced oxidation processes (AOPs), this study analyzed the electron contribution of pollutants qualitatively and quantitatively which rarely reported before. The rich electron transfer system was constructed by mesoporous carbon nitride (MCN) coupling with persulfate (PS) driven by visible light and the sulfanilamide antibiotics (SULs) were used as target contaminants. Firstly, the qualitative analysis of electron transfer in the system was confirmed systematically. The electron flow direction tested by i-t curves indicated that PS absorbed electrons, while SULs released electrons. The flow rate of electrons was also accelerated after the addition of SULs. The fitting curve between the kinetics and the peak potential difference tested by CV curve showed that the larger potential difference, the slower rate of oxidative degradation. Secondly, the quantification of electron transfer was achieved through theoretical calculations to simulate the interactions of the 'catalyst-oxidant-antibiotic' system. After the addition of SULs, the adsorption energy of the 'catalyst-oxidant-antibiotic' system was enhanced and the bond length of the peroxide bond was stretched. Notably, the electron transfer analysis results showed that the charge of SULs was around 0.032-0.056e, indicating that SULs pollutants played the role of electron contributors in the system. The oxidative degradation pathway included the direct cracking of S-N bond, shedding of marginal groups, ring-opening and hydroxyl addition reaction. This study clarified the electronic contribution of SULs in the oxidation system, providing necessary theoretical supplement for the analysis of the transformation of pollutants in AOPs.

Direct Electron Transfer-Driven Nontoxic Oligomeric Deposition of Sulfonamide Antibiotics onto Carbon Materials for In Situ Water Remediation

The rising in situ chemical oxidation (ISCO) technologies based on polymerization reactions have advanced the removal of emerging contaminants in the aquatic environment. However, despite their promise, uncertainties persist regarding their effectiveness in eliminating structurally complex contaminants, such as sulfonamide antibiotics (SAs). This study elucidated that oligomerization, rather than mineralization, predominantly governs the removal of SAs in the carbon materials/periodate system. The amine groups in SAs played a crucial role in forming organic radicals and subsequent coupling reactions due to their high f- index and low bond orders. Moreover, the study highlighted the robust adhesion of oligomers to the catalyst surface, facilitated by enhanced van der Waals forces and hydrophobic interactions. Importantly, plant and animal toxicity assessments confirmed the nontoxic nature of oligomers deposited on the carbon material surface, affirming the efficacy of carbon material-based ISCO in treating contaminated surface water and groundwater. Additionally, a novel classification approach, Δlog k, was proposed to differentiate SAs based on their kinetic control steps, providing deeper insights into the quantitative structure-activity relationship (QSAR) and facilitating the selection of optimal descriptors during the oligomerization processes. Overall, these insights significantly enhance our understanding of SAs removal via oligomerization and demonstrate the superiority of C-ISCO based on polymerization in water decontamination.

Anchored Cobalt Nanoparticles on Layered Perovskites for Rapid Peroxymonosulfate Activation in Antibiotic Degradation

In the Fenton-like reaction, revealing the dynamic evolution of the active sites is crucial to achieve the activity improvement and stability of the catalyst. This study reports a perovskite oxide in which atomic (Co0) in situ embedded exsolution occurs during the high-temperature phase transition. This unique anchoring strategy significantly improves the Co3+/Co2+ cycling efficiency at the interface and inhibits metal leaching during peroxymonosulfate (PMS) activation. The Co@L-PBMC catalyst exhibits superior PMS activation ability and could achieve 99% degradation of tetracycline within 5 min. The combination of experimental characterization and density functional theory (DFT) calculations elucidates that the electron-deficient oxygen vacancy accepts an electron from the Co 3d-orbital, resulting in a significant electron delocalization of the Co site, thereby facilitating the adsorption of the *HSO5/*OH intermediate onto the "metal-VO bridge" structure. This work provides insights into the PMS activation mechanism at the atomic level, which will guide the rational design of next-generation catalysts for environmental remediation.

Size-Dependent Catalysis in Fenton-like Chemistry: From Nanoparticles to Single Atoms

State-of-the-art Fenton-like reactions are crucial in advanced oxidation processes (AOPs) for water purification. This review explores the latest advancements in heterogeneous metal-based catalysts within AOPs, covering nanoparticles (NPs), single-atom catalysts (SACs), and ultra-small atom clusters. A distinct connection between the physical properties of these catalysts, such as size, degree of unsaturation, electronic structure, and oxidation state, and their impacts on catalytic behavior and efficacy in Fenton-like reactions. In-depth comparative analysis of metal NPs and SACs is conducted focusing on how particle size variations and metal-support interactions affect oxidation species and pathways. The review highlights the cutting-edge characterization techniques and theoretical calculations, indispensable for deciphering the complex electronic and structural characteristics of active sites in downsized metal particles. Additionally, the review underscores innovative strategies for immobilizing these catalysts onto membrane surfaces, offering a solution to the inherent challenges of powdered catalysts. Recent advances in pilot-scale or engineering applications of Fenton-like-based devices are also summarized for the first time. The paper concludes by charting new research directions, emphasizing advanced catalyst design, precise identification of reactive oxygen species, and in-depth mechanistic studies. These efforts aim to enhance the application potential of nanotechnology-based AOPs in real-world wastewater treatment.

Recent advances in catalyst design, performance, and challenges of metal-heteroatom-co-doped biochar as peroxymonosulfate activator for environmental remediation

The escalation of global water pollution due to emerging pollutants has gained significant attention. To address this issue, catalytic peroxymonosulfate (PMS) activation technology has emerged as a promising treatment approach for effectively decontaminating a wide range of pollutants. Recently, modified biochar has become an increasingly attractive as PMS activator. Metal-heteroatom-co-doped biochar (MH-BC) has emerged as a promising catalyst that can provide enhanced performance over heteroatom-doped and metal-doped biochar due to the synergism between metal and heteroatom in promoting PMS activation. Therefore, this review aims to discuss the fabrication pathways (i.e., internal vs external doping and pre-vs post-modification) and key parameters (i.e., source of precursors, synthesis methods, and synthesis conditions) affecting the performance of MH-BC as PMS activator. Subsequently, an overview of all the possible PMS activation pathways by MH-BC is provided. Subsequently, Also, the detection, identification, and quantification of several reactive species (such as, •OH, SO4•-, O2•-, 1O2, and high valent oxo species) generated in the catalytic PMS system by MH-BC are also evaluated. Lastly, the underlying challenges associated with poor stability, the lack of understanding regarding the interaction between metal and heteroatom during PMS activation and quantification of radicals in multi-ROS system are also deliberated.

pH-modulated oxidation of organic pollutants for water decontamination: A deep insight into reactivity and oxidation pathway

Solution pH is one of the primary factors affecting the efficiency of water decontamination. Although the influence of pH on oxidants activation, catalyst activity, and reactive oxygen species have been widely explored, there is still a scarcity of systemic studies on the changes in the oxidation behavior of organic pollutants at different pH levels. Herein, we report the influence laws of pH on the forms, reactivities, active sites, degradation pathways, and products toxicities of organic pollutants. Changes in pH cause the protonation or deprotonation of organic pollutants and further affect their forms and chemistry (e.g., electrostatic force, hydrophobicity, and oxidation potential). The oxidation potential of organic pollutants follows the order: protonated form > pristine form > deprotonated form. Moreover, protonation or deprotonation can modify the active sites and degradation pathways of organic pollutants, wherein deprotonation renders them more susceptible to electrophilic attack, while protonation reduces their activity against electrophilic and nucleophilic attacks. Additionally, pH adjustments can modify the degradation pathway and the toxicity of transformation products. Overall, pH changes can affect the oxidation fate of organic pollutants by altering their structure, which distinguishes it from the effect of pH on oxidants or oxidant activation processes.

Tailoring the selective generation of oxidative organic radicals for toxic-by-product-free water decontamination

Peracetic acid (PAA) is emerging as a versatile agent for generating long-lived and selectively oxidative organic radicals (R-O•). Currently, the conventional transition metal-based activation strategies still suffer from metal ion leaching, undesirable by-products formation, and uncontrolled reactive species production. To address these challenges, we present a method employing BiOI with a unique electron structure as a PAA activator, thereby predominantly generating CH3C(O)O• radicals. The specificity of CH3C(O)O• generation ensured the superior performance of the BiOI/PAA system across a wide pH range (2.0 to 11.0), even in the presence of complex interfering substances such as humic acids, chloride ions, bicarbonate ions, and real-world water matrices. Unlike conventional catalytic oxidative methods, the BiOI/PAA system degrades sulfonamides without producing any toxic by-products. Our findings demonstrate the advantages of CH3C(O)O• in water decontamination and pave the way for the development of eco-friendly water decontaminations based on organic peroxides.

Decolorization and degradation of crystal violet dye by electron beam radiation: Performance, degradation pathways, and synergetic effect with peroxymonosulfate

Ionizing radiation (mainly including gamma ray and electron beam) technology provides a more efficient and ecological option for dye-containing wastewater treatment, which is supported by its successful achievements in industrial-scale applications. However, the degradation pathway of triphenylmethane dyes by radiation technology is still unclear. In this study, crystal violet (CV) was selected as representative cationic triphenylmethane dye, the decolorization and degradation performance by electron beam radiation technology was systematically evaluated. The results showed that CV can be efficiently decolorized and mineralized by radiation, and its degradation kinetics followed the first-order kinetic model. The effect of inorganic anions and chelating agents commonly existed in dye-containing wastewater on CV decolorization and total organic carbon (TOC) removal was explored. Quenching experiments, density functional theory (DFT) calculation and high performance liquid chromatography mass spectrometry (HPLC-MS) analysis were employed to reveal CV decolorization and degradation mechanism and pathway, which mainly included N-demethylation, triphenylmethane chromophore cleavage, ring-opening of aromatic products and further oxidation to carboxylic acid, and mineralization to CO2 and H2O. Additionally, electron beam radiation/PMS process was explored to decrease the absorbed dose required for decolorization and degradation, and the synergetic effect of radiation with PMS was elucidated. More importantly, the findings of this study would provide the support for treating actual dyeing wastewater by electron beam radiation technology.

Peroxydisulfate-Driven Reductive Dechlorination as Affected by Soil Constituents: Free Radical Formation and Conversion

We report a previously unrecognized but efficient reductive degradation pathway in peroxydisulfate (PDS)-driven soil remediation. With supplements of naturally occurring low-molecular-weight organic acids (LMWOAs) in anaerobic biochar-activated PDS systems, degradation rates of 12 γ-hexachlorocyclohexanes (HCH)-spiked soils boosted from 40% without LMWOAs to a maximum of 99% with 1 mM malic acid. Structural analysis revealed that an increase in α-hydroxyl groups and a diminution in pKa1 values of LMWOAs facilitated the formation of reductive carboxyl anion radicals (COO•-) via electrophilic attack by SO4•-/•OH. Furthermore, degradation kinetics were strongly correlated with soil organic matter (SOM) contents than iron minerals. Combining a newly developed in situ fluorescence detector of reductive radicals with quenching experiments, we showed that for soils with high, medium, and low SOM contents, dominant reactive species switched from singlet oxygen/semiquinone radicals to SO4•-/•OH and then to COO•- (contribution increased from 30.8 to 66.7%), yielding superior HCH degradation. Validation experiments using SOM model compounds highlighted critical roles of redox-active moieties, such as phenolic - OH and quinones, in radical formation and conversion. Our study provides insights into environmental behaviors related to radical activation of persulfate in a broader soil horizon and inspiration for more advanced reduction technologies.

Insights into the efficient water treatment over N-doped carbon nanosheets with layered minerals as template: The role of interfacial electron tunneling and transfer

Peroxymonosulfate (PMS) oxidation reactions have been extensively studied recently. Due to the high material cost and low catalytic capability, PMS oxidation technology cannot be effectively applied in an industrial water treatment process. In this work, we developed a modification strategy based on enhancing the neglected electron tunneling effect to optimize the intrinsic electron transport process of the catalyst. The 2D nitrogen-doped carbon-based nanosheets with small interlayer spacing were prepared by self-polymerization of dopamine hydrochloride inserted into the natural layered bentonite template. Systematic characterizations confirmed that the smaller layer spacing in the 2D nitride-doped carbon-based nanosheets reduces the depletion layer width. The weak electronic shielding effect derived by the small layer spacing on the material subsurface enhanced the bulk electron tunneling effect. More bulk electrons could be migrated to the catalyst surface to activate PMS molecules. The PMS activation system showed ultrafast oxidation capability to degrade organic pollutants and strong ability to resist interference from environmental matrixes due to the optimized electron transfer process. Furthermore, the developed membrane reactor exhibited strong catalytic stability during the continuous degradation of P-Chlorophenol (CP).

Sustainable and Rapid Water Purification at the Confined Hydrogel Interface

Emerging organic contaminants in water matrices have challenged ecosystems and human health safety. Persulfate-based advanced oxidation processes (PS-AOPs) have attracted much attention as they address potential water purification challenges. However, overcoming the mass transfer constraint and the catalyst's inherent site agglomeration in the heterogeneous system remains urgent. Herein, the abundant metal-anchored loading (≈6-8 g m-2) of alginate hydrogel membranes coupled with cross-flow mode as an efficient strategy for water purification applications is proposed. The organic flux of the confined hydrogel interfaces sharply enlarges with the reduction of the thickness of the boundary layer via the pressure field. The normalized property of the system displays a remarkable organic (sulfonamides) elimination rate of 4.87 × 104 mg min-1 mol-1. Furthermore, due to the fast reaction time (<1 min), cross-flow mode only reaches a meager energy cost (≈2.21 Wh m-3) under the pressure drive field. It is anticipated that this finding provides insight into the novel design with ultrafast organic removal performance and low techno-economic cost (i.e., energy operation cost, material, and reagent cost) for the field of water purification under various PS-AOPs challenging scenarios.

Enhancing Fenton-like reaction through a multifunctional molybdenum disulfide film coating on nano zero valent iron surface (MoS2@nZVI): Collaboration of radical and non-radical pathways

In this study, we synthesized nano zero-valent iron incorporated with a multifunctional molybdenum disulfide film (MoS2@nZVI). The material exhibited a 100.00 % removal efficiency for sulfamethoxazole (SMX) and achieved a kobs of 0.4485 min-1 within 10 min. The excellent degradation performance can be attributed to the incorporation of the MoS2 film, which facilitated Fe2+ regeneration. Simultaneously, the MoS2 film assisted in proton accumulation and electron transfer, thereby amplifying the efficiency of SMX degradation across a wide pH range. Comprehensive experimental examinations and characterizations confirmed the selectivity and stability of the MoS2@nZVI catalysts, encompassing both degradation efficiency and structural stability. Interestingly, the MoS2@nZVI/PMS system for SMX degradation significantly involved a non-radical mechanism (1O2), along with radicals (SO4·-, ·OH, and O2·-). The direct oxidation of PMS by Fe2+ not only facilitated the generation of ·OH and SO4·- but also actively engaged in a reaction with O2, leading to the production of O2·-. The primary pathway for 1O2 production was established through the interplay between Mo6+ and O2·-, in conjunction with the direct electron transfer (DET) mechanism between PMS and SMX. The contributions of these active species to SMX degradation occurred in the following precedence: SO4·- > 1O2 > ·OH > O2·-. Notably, the primary pathways for radicals and non-radicals were studied during separate reaction periods. This investigation proposed a promising approach for mitigating pharmaceutical pollutants using a transition metal sulfide-modified nZVI catalyst.

Removal of sulfonylurea herbicides with g-C3N4-based photocatalysts: A review

The accumulation of agricultural chemicals in the environment has become a global concern, of which sulfonylurea herbicides (SUHs) constitute a significant category. Solar-driven photocatalysis is favored for removing organic pollutants due to its high efficiency and environmental friendliness. Graphite carbon nitride (g-C3N4)-based materials with superior catalytic activities and physicochemical stabilities are promising photocatalysts. This review describes the g-C3N4-based materials and their uses in the photocatalytic degradation of SUHs or other organic pollutants with similar structures. First, the fundamentals of g-C3N4-based materials and photocatalytic SUHs degradation are discussed to provide an in-depth understanding of the mechanism for the photocatalytic activity. The ability of different g-C3N4-based materials to photocatalytically degrade SUH-like structures is then discussed and summarized based on different modification strategies (morphology modulation, elemental doping, defect engineering, and heterojunction formations). Meanwhile, the effects of different environmental factors on the photocatalytic performance of g-C3N4-based materials are described. Finally, the major challenges and opportunities of g-C3N4-based materials for the photocatalytic degradation of SUHs are proposed. It is hoped that this review will show the feasibility of photocatalytic degradation of SUHs with g-C3N4-based materials.

Mechanistic exploration of Co doping in optimizing the electrochemical performance of 2H-MoS2/N-doped carbon anode for potassium-ion battery

The 2H-MoS2/nitrogen-doped carbon (2H-MoS2/NC) composite is a promising anode material for potassium-ion batteries (PIBs). Various transition metal doping has been adopted to optimize the poor intrinsic electronic conductivity and lack of active sites in the intralayer of 2H-MoS2. However, its optimization mechanisms have not been well probed. In this paper, using Cobalt (Co) as an example, we aim to investigate the influence of transition metal doping on the electronic and mechanical properties and electrochemical performance of 2H-MoS2/NC via first-principles calculation. Co doping is found to be effective in improving the electronic conductivity and the areas of active sites on different positions (C surface, interface, and MoS2 surface) of 2H-MoS2/NC. The increased active sites can optimize K adsorption and diffusion capability/processes, where general smaller K adsorption energies and diffusion energy barriers are found after Co doping. This helps improve the rate performance. Especially, the pyridinic N (pyN), pyrrolic N (prN), and graphitic N (grN) are first unveiled to respectively work best in K kinetic adsorption, diffusion, and interfacial stability. These findings are instructive to experimental design of high rate 2H-MoS2/NC electrode materials. The roles of different N types provide new ideas for optimal design of other functional composite materials.