Nitrogen-Doped Reduced Graphene Oxide as a Bifunctional Material for Removing Bisphenols: Synergistic Effect between Adsorption and Catalysis

Heterogeneous catalytic ozonation for the removal of antibiotics in water: A review

Antibiotics with pseudo-persistence in water have been regarded as emerging pollutants, which have obvious biological toxicity even at trace levels. On account of high reactivity, heterogeneous catalytic ozonation has been widely applied to remove antibiotics. Among the heterogeneous catalysts, with well-developed pores and regulable surface defects, carbon-based materials can act as both adsorbents and catalysts. Metal cations, surface hydroxyl (-OH) groups and oxygen vacancies (OVs) serve as primary active sites in metal oxides. However, composites (perovskite, apatite, etc.) with special crystalline structure have more crystallographic planes and abundant active sites. The unsaturated bonds and aromatic rings which have dense structure of the electron cloud are more likely to be attacked by ozone (O3) directly. Sulfonamides (SAs) can be oxidized by O3 directly within a short time due to the structure of activated aromatic rings and double bonds. With the existence of catalysts, almost all antibiotics can attain fair removal effects. The presence of water matrix can greatly influence the removal rate of pollutants via changing the surface properties of catalysts, competing active sites with O3, etc. Correspondingly, the application of diverse heterogeneous catalysts was introduced in details, based on modification including metal/non-metal doping, surface modification and carrier composite. The degradation pathways of SAs, fluoroquinolones (FQNs), tetracyclines (TCs) and β-lactams were summarized founded on the functional group structures. Furthermore, the effects of water matrix (pH, coexisting ions, organics) for catalytic ozonation were also debated. It is expected to proffer advanced guidance for researchers in catalytic ozonation of antibiotics.

Analyzing the active sites of carbocatalyst for peroxydisulfate activation: Specific surface area or electrochemical surface area?

Persulfates activation by various nanomaterials has been intensively reported for advanced oxidation processes (AOPs), and substantial progress has been made in understanding the mechanism. However, most of the published articles only present the unnormalized catalytic properties, which generated confusion to compare different catalysts and identify the active sites. Herein, we presented electrochemical surface area (ECSA) as a practical normalized method and confirmed the primary active sites in N-doped graphene. By controlling the aggregation state of graphene sheets to adjust the activity of doped graphite-N species, the active sites for peroxydisulfate (PDS) activation were accurately estimated. In further experiments, specific surface area (SSA, by N2-physisorption and methylene blue adsorption) and ECSA were adopted to conclude the normalized oxidation rate constant and graphitic-N was confirmed as the primary site in nitrogen-doped graphene for the carbocatalyst/PDS system. The normalized results revealed that SSA derived from inert gas on materials could not reflect the true active sites at solid-liquid interface, while ECSA considering the operated solid-liquid situation can be used for accurate estimation of the active sites. Therefore, this study suggests that ECSA integrates the properties of both kinetics and thermodynamics, which can be adopted as a useful methodology for analyzing nano-sized environmental catalysts performance.

High adsorption to methylene blue based on Fe3O4-N-banana-peel biomass charcoal

This research focused on utilizing banana peel as the primary material for producing mesoporous biomass charcoal through one-step potassium hydroxide activation. Subsequently, the biomass charcoal underwent high-temperature calcination with varying impregnation ratios of KOH : BC for different durations in tubular furnaces set at different temperatures. The resultant biomass charcoal was then subjected to hydrothermal treatment with FeCl3·6H2O to produce biochar/iron oxide composites. The adsorption capabilities of these composites towards methylene blue (MB) were examined under various conditions, including pH (ranging from 3 to 12), temperature variations, and initial MB concentrations (ranging from 50 to 400 mg L-1). The adsorption behavior aligned with the Langmuir model and demonstrated quasi-secondary kinetics. After five adsorption cycles, the capacity decreased from 618.64 mg g-1 to 497.18 mg g-1, indicating considerable stability. Notably, Fe3O4-N-BC exhibited exceptional MB adsorption performance.

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.

Carboxymethyl chitosan modification of cobalt-zinc bimetallic MOF for tetracycline hydrochloride removal: Exploration of the enhancement mechanism of the process

This study synthesized a carboxymethyl chitosan-modified bimetallic Co/Zn-ZIF (CZ@CMC) with strong hydrophilicity and adsorption performance via the one-pot method. Tetracycline hydrochloride (TCH) was used as the model contaminant to evaluate the adsorption and peroxymonosulfate (PMS) activation properties of CZ@CMC. Mechanism showed that the adsorption behavior occurred through pore filling, electrostatic attraction, surface complexation, hydrogen bonding, and π-π stacking. In addition, a CZ@CMC/PMS system was constructed, which had excellent catalytic performance. The hydrophilicity and selective adsorption properties of CMC conferred a greatly accelerated CZ@CMC in catalyzing the PMS process with kobs of 0.095 min-1, in which OH, 1O2, SO4-, O2-, and Co(III) were the main ROS which quenching tests, EPR, and chemical probe experiments verified. In addition, the degradation pathways of TCH were obtained utilizing DFT and HPLC-MS and analyzed to show that the system possessed a good detoxification capacity. This work is expected to provide a green, efficient, and stable strategy to enhance the adsorption properties of catalytic materials and subsequently their co-catalytic properties.

Hollow Nanoreactors Unlock New Possibilities for Persulfate-Based Advanced Oxidation Processes

As a novel type of catalytic material, hollow nanoreactors are expected to bring new development opportunities in the field of persulfate-based advanced oxidation processes due to their peculiar void-confinement, spatial compartmentation, and size-sieving effects. For such materials, however, further clarification on basic concepts and construction strategies, as well as a discussion of the inherent correlation between structure and catalytic activity are still required. In this context, this review aims to provide a state-of-the-art overview of hollow nanoreactors for activating persulfate. Initially, hollow nanoreactors are classified according to the constituent components of the shell structure and their dimensionality. Subsequently, the different construction strategies of hollow nanoreactors are described in detail, while common synthesis methods for these construction strategies are outlined. Furthermore, the most representative advantages of hollow nanoreactors are summarized, and their intrinsic connections to the nanoreactor structure are elucidated. Finally, the challenges and future prospects of hollow nanoreactors are presented.

Ultrafine CuO/graphene oxide cellulose nanocomposites with complementary framework for polycyclic aromatic hydrocarbon pollutants removal

Efficient and sustainable methods for eliminating polycyclic aromatic hydrocarbon pollutants (PAHPs) are in highly desired. Proven technologies involve physical and chemical reactions that absorb PAHPs, however they encounter formidable challenges. Here, a bottom-up refining-grain strategy is proposed to rationally design ultrafine CuO/graphene oxide-cellulose nanocomposites (LCelCCu) with a mirror-like for tetracycline (TC) to substantially improve the efficient of the purification process by active integrated-sorption. The LCelCCu captures TC with a higher affinity and lower energy demand, as determined by sorption kinetic, isotherms, thermodynamics, and infrared and X-ray Photoelectron Spectroscopy. The resulting material could achieve ultra-high sorption capacity (2775.23 mg/g), kinetic (1.2499 L g-1 h-1) and high selectivity (up to 99.9 %) for TC, nearly surpassing all recent adsorbents. This study simultaneously unveils the pioneering role of simultaneous multi-site match sorption and subsequent advanced oxidation synergistically, fundamentally enhancing understanding of the structure-activity-selectivity relationship and inspires more sustainable water purification applications and broader material design considerations.

Antifungal Hybrid Graphene-Transition-Metal Dichalcogenides Aerogels with an Ionic Liquid Additive as Innovative Absorbers for Preventive Conservation of Cultural Heritage

The use and integration of novel materials are increasingly becoming vital tools in the field of preventive conservation of cultural heritage. Chemical factors, such as volatile organic compounds (VOCs), but also environmental factors such as high relative humidity, can lead to degradation, oxidation, yellowing, and fading of the works of art. To prevent these phenomena, highly porous materials have been developed for the absorption of VOCs and for controlling the relative humidity. In this work, graphene and transition-metal dichalcogenides (TMDs) were combined to create three-dimensional aerogels that absorb certain harmful substances. More specifically, the addition of the TMDs molybdenum disulfide and tungsten disulfide in such macrostructures led to the selective absorption of ammonia. Moreover, the addition of the ionic liquid 1-hexadecyl-3-methylimidazolium chloride promoted higher rates of VOCs absorption and anti-fungal activity against the fungus Aspergillus niger. These two-dimensional materials outperform benchmark porous absorbers in the absorption of all the examined VOCs, such as ammonia, formic acid, acetic acid, formaldehyde, and acetaldehyde. Consequently, they can be used by museums, galleries, or even storage places for the perpetual protection of works of art.

Cu/N co-doped biochar activating PMS for selective degrading paracetamol via a non-radical pathway dominated by singlet oxygen and electron transfer

The non-free radical oxidation pathway (PMS-NOPs) of peroxymonosulfate (PMS) holds significant promise for practical wastewater treatment applications, owing to its low oxidation potential, high PMS utilization rate, and robust anti-interference capability in the degradation of pollutants. A novel activator copper nitrogen co-doped porous biochar (Cu-N-BC) with rich defect edges and functional groups was obtained by adding Cu and N to the biochar matrix generated by sodium alginate through pyrolysis in this study. Under the condition of 1 mM PMS, 30 mg/L activator was used to activate PMS and achieve efficient degradation of 10 mg/L paracetamol (PCT) within 15 min, with a high reaction rate constants (kobs) of 0.391 min-1. The activation mechanism of the Cu-N-BC/PMS/PCT system was a non-radical activation pathway with the dominance of singlet oxygen (1O2) and the presence of catalyst-mediated electron transfer. The graphite nitrogen, pyridine nitrogen, and Cu-N coordination introduced by Cu/N co-doping, as well as the carbon skeleton and CO functional group of biochar, were considered active sites that promote the 1O2 generation. The Cu-N-BC/PMS system exhibits strong stability, eco-friendliness, effective mineralization, and interference resistance across diverse pH levels (3-11) and interfering ions, including Cl-, H2PO4-, NO3-, SO42-, and humic acid. Remarkably, it efficiently degrades PCT in tap and lake water, achieving a notable 63.73% TOC mineralization rate, with leached copper ions below 0.02 mg/L. This research introduces a novel method for obtaining metal nitrogen carbon activators and enhances understanding of PMS non-radical activation pathways and active sites.

Nitrogen-Doped Biochar for Enhanced Peroxymonosulfate Activation to Degrade Phenol through Both Free Radical and Direct Oxidation Based on Electron Transfer Pathways

Nowadays, super nitrogen-doped biochar (SNBC) material has become one of the most promising metal-free catalysts for activating peroxymonosulfate (PMS) to degrade organic pollutants. To understand the evolution of SNBC properties with fabrication conditions, a variety of SNBC materials were prepared and characterized by elemental analysis, N2 adsorption-desorption, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. We systematically investigated the activation potential of these SNBC materials for PMS to degrade phenol. SN1BC-800 with the best catalytic performance was obtained by changing the activation temperatures and the ratio of biochar to melamine. The effects of catalyst dosage, the PMS concentration, pH, and reaction temperature on phenol degradation were studied in detail. In the presence of 0.3 g/L SN1BC-800 and 1 g/L PMS, the removal rate of 20 mg/L phenol could reach 100% within 5 min. According to electron paramagnetic resonance spectra and free radical quenching experiments, a nonfree radical pathway of phenol degradation dominated by 1O2 and electron transfer was proposed. More interestingly, the excellent catalytic performance of the SN1BC-800/PMS system is universally applicable in the degradation of other typical organic pollutants. In addition, the degradation rate of phenol is still over 80% after five reuses, which shows that the SN1BC-800 catalyst has high stability and good application prospects in environmental remediation.

Catalytic activation of persulfate by nanoscale zero-valent iron-derived supported boron-doped porous carbon for bisphenol A degradation

In this study, boron-doped porous carbon materials (BCs) with high surface areas were synthesized employing coffee grounds as carbon source and sodium bicarbonate and boric acid as precursors; afterward, nanoscale zero-valent iron (nZVI) and BCs composites (denoted as nZVI@BCs) were further prepared through reduction of FeSO4 by NaBH4 along with stirring. The performance of the nZVI@BCs for activating persulfate (PS) was evaluated for the degradation of bisphenol A (BPA). In comparison with nZVI@Cs/PS, nZVI@BCs/PS could greatly promote the degradation and mineralization of BPA via both radical and non-radical pathways. On the one hand, electron spin resonance and radical quenching studies represented that •OH, SO4•-, and O2•- were mainly produced in the nZVI@BCs/PS system for BPA degradation. On the other hand, the open circuit voltages of nZVI@BCs and nZVI@Cs in different systems indicated that non-radical pathway still existed in our system. PS could grab the unstable unpaired electron on nZVI@BCs to form a carbon material surface-confined complex ([nZVI@BCs]*) with a high redox potential, then accelerate BPA removal efficiency via direct electron transfer. Furthermore, the performances and mechanisms for BPA degradation were examined by PS activation with nZVI@BC composites at various conditions including dosages of nZVI@BCs, BPA and PS, initially pH value, temperature, common anions, and humid acid. Therefore, this study provides a novel insight for development of high-performance carbon catalysts toward environmental remediation.

Removal of sulfonamide antibiotics by non-free radical dominated peroxymonosulfate oxidation catalyzed by cobalt-doped sulfur-containing biochar from sludge

The reuse of activated sludge as a solid waste is severely underutilized due to the limitations of traditional treatment and disposal methods. Given that, the sulfur-containing activated sludge catalyst doped with cobalt (SK-Co(1.0)) was successfully prepared by one-step pyrolysis and calcinated at 850 ℃. The generation of CoSx was successfully characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), indicating that the sulfur inside the sludge was the anchoring site for the externally doped cobalt. Cobalt (Ⅱ) (Co2+), as the main adsorption site for peroxymonosulfate(PMS), formed a complex (SK-Co(1.0)-PMS* ) and created the conditions for the generation of surface radicals. The SK-Co(1.0)/PMS system showed high degradation efficiency and apparent rate constants for Sulfamethoxazole (SMX) (91.56% and 0.187 min-1) and Sulfadiazine (SDZ) (90.73% and 0.047 min-1) within 10 min and 30 min, respectively. Three sites of generation of 1O2, which played a dominant role in the degradation of SMX and SDZ in the SK-Co(1.0)/PMS system, were summarized as：sulfur vacancies (SVs), the Co3+/Co2+ cycles promoted by sulfur(S) species, oxygen-containing functional groups (C-O). The degradation mechanisms and pathways had been thoroughly investigated using DFT calculations. In view of this, a new idea for the resource utilization of activated sludge solid waste was provided and a new strategy for wastewater remediation was proposed.

Origins of Selective Oxidation in Carbon-Based Nonradical Oxidation Processes toward Organic Pollutants: Quantitative Structure-Activity Relationships (QSARs)

Metal-free carbon material-mediated nonradical oxidation processes (C-NOPs) have emerged as a research hotspot due to their excellent performance in selectively eliminating organic pollutants in aqueous environments. However, the selective oxidation mechanisms of C-NOPs remain obscure due to the diversity of organic pollutants and nonradical active species. Herein, quantitative structure-activity relationship (QSAR) models were employed to unveil the origins of C-NOP selectivity toward organic pollutants in different oxidant systems. QSAR analysis based on adsorption and oxidation descriptors revealed that C-NOP selectivity depends on the oxidation potentials of organic pollutants rather than on adsorption interactions. However, the dominance of electronic effects in selective oxidation decreases with increasing structural complexity of organic pollutants. Moreover, the oxidation threshold solely depends on the inherent electronic nature of organic pollutants and not on the reactivity of nonradical active species. Notably, the accuracy of substituent descriptors (Hammett constants) and theoretical descriptors (e.g., highest occupied molecular orbital energy, ionization potential, and single-electron oxidation potential) is significantly influenced by the complexity and molecular state of organic pollutants. Overall, the study findings reveal the origins of organic pollutant-oriented selective oxidation and provide insight into the application of descriptors in QSAR analysis.

Synergistic effect of silver nanoparticle-embedded calcite-rich biochar derived from Tamarindus indica bark on 4-nitrophenol reduction

Calcite-biochar composites are attractive materials with outstanding adsorption capabilities for removing various recalcitrant contaminants in wastewater treatment, however, the complexity of their synthesis limits their practical applications. In this work, we have prepared calcite-rich biochar (Ca-BC) from a single precursor (Tamarindus indica bark), which simplifies the synthetic route for preparing calcite-biochar composite. The as-synthesized composite is utilized to make a heterogeneous catalytic system containing the supported silver nanoparticles (Ag@Ca-BC) formed by the reduction of Ag+ ions on the surface of the composite. The formation of Ag@Ca-BC is confirmed by various characterization techniques such as PXRD, FT-IR, UV-Vis, cyclic voltammetry, impedance measurement, SEM, and TEM analyses. Especially, the TEM analysis confirms the presence of Ag nanoparticles with size ranging between 20 and 50 nm on the surface of Ca-BC composite. The nano-catalyst Ag@Ca-BC efficiently promotes the conversion of 4-nitrophenol to 4-aminophenol using NaBH4 as the reductant in water within 24 minutes at room temperature, suggesting that Ag@Ca-BC can be an efficient catalyst to remove nitroaromatics from the industrial effluents. The straightforward synthesis of Ca-BC from a single precursor along with its utility as a catalytic support presents a compelling proposition for application in the field of materials synthesis, catalysis, and green chemistry.

Catalytic ozonation of bisphenol A by Cu/Mn@γ-Al2O3: Performance evaluation and mechanism insight

Herein, an alumina-based bimetallic catalyst (Cu1Mn7@γ-Al2O3) was synthesized for bisphenol A (BPA) degradation in the catalytic ozonation process. The catalytic ozonation system could degrade 93.9% of BPA within 30 min under the conditions of pH = 7.0, 10 mg L-1 O3 concentration, and 24 g L-1 catalyst dosage compared to ozone alone (21.0%). The enhanced BPA degradation efficiency was attributed to the abundant catalytic sites and synergistic effects of Cu and Mn. The results revealed that the synergistic interaction between Cu and Mn effectively accelerated the electron transfer process on the catalyst surface, thus promoting the generation of reactive oxygen species (ROS). Further studies indicated that the BPA degradation in Cu1Mn7@γ-Al2O3/O3 system predominantly followed the ·OH and O2·- oxidation pathway. Based on the density functional theory (DFT) calculations and intermediates detected by LC-MS analysis, two pathways for BPA degradation in the Cu1Mn7@γ-Al2O3/O3 system were proposed. The toxicity estimation illustrated that the toxicity of BPA and its byproducts was effectively reduced in the Cu1Mn7@γ-Al2O3/O3 system. This work provides a new protocol for O3 activation and pollutant elimination through a novel bimetallic catalyst during water purification.

Iron-loading N and S heteroatom doped porous carbon derived from chitosan and CdS-Tetrahymena thermophila for peroxymonosulfate activation

Transforming waste into resources is an important strategy to enhance the economic efficiency and reduce the waste entering the environment. In this work, iron-loading N and S co-doped porous carbon materials, as peroxymonosulfate (PMS) activator for pollutants degradation, were prepared by pyrolysis of the mixture of iron loading chitosan and CdS-Tetrahymena thermophila under N2 flow. Chitosan is mainly derived from the shell waste of shrimp and crab, and CdS-Tetrahymena thermophila is produced in the removing process of Cd2+ pollution bioremediation using Tetrahymena thermophila. The synergistic effects of iron related species and heteroatoms (S/N) co-doped porous carbon in the obtained carbon materials improved the performance for activating PMS. The prepared Fe-S-CS-1-900 exhibited high performance for the degradation of Rhodamine B (RhB) by activating PMS. Radical quenching tests and electron paramagnetic resonance measurements suggested that superoxide radical (O2-) and singlet oxygen (1O2) were the primary reactive oxygen species in RhB degradation. These results propose new insights of using biomass waste to derive Fe-loading N and S heteroatom co-doping carbon as PMS activator applied in the removal of organic pollutants.

Research Progress of Methods for Degradation of Bisphenol A

Bisphenol A (BPA), an endocrine disruptor widely used in industrial production, is found in various environmental sources. Despite numerous reports on BPA degradation and removal, the details remain unclear. This paper aims to address this gap by providing a comprehensive review of BPA degradation methods, focusing on biological, physical, and chemical treatments and the factors that affect the degradation of BPA. Firstly, the paper uses VOSviewer software (version 1.6.15) to map out the literature on BPA degradation published in the past 20 years, which reveals the trends and research focus in this field. Next, the advantages and limitations of different BPA degradation methods are discussed. Overall, this review highlights the importance of BPA degradation to protect the environment and human health. The paper provides significant insights for researchers and policymakers to develop better approaches for BPA degradation and removal.

Carbocatalysts for Enhancing Permanganate Oxidation of Sulfisoxazole

Permanganate (Mn(VII)) is extensively applied in water purification due to its stability and ease of handling, but it is a mild oxidant for trace organic contaminants (TrOCs). Hence, there is significant interest in strategies for enhancing reaction kinetics, especially in combination with efficient and economical carbocatalysts. This study compared the performance of four carbocatalysts (graphite, graphene oxide (GO), reduced-GO (rGO), and nitrogen-doped rGO (N-rGO)) in accelerating sulfisoxazole (SSX) oxidation by Mn(VII) and found that GO exhibited the greatest catalytic performance. Besides, the Mn(VII)/GO system shows desirable capacities to remove a broad spectrum of TrOCs. We proposed that the degradation of SSX in Mn(VII)-GO suspensions follows two routes: (i) direct oxidation of SSX by Mn species [both Mn(VII) and in situ formed MnO2(s)] and (ii) a carbocatalyst route, where GO acts as an electron mediator, accepting electrons from SSX and transferring them to Mn(VII). We developed a mathematical model to show the contribution of each parallel pathway and found one-electron transfer is primarily responsible for accelerating SSX removal in the Mn(VII)/GO system. Findings in this study showed that GO provides a simple and effective strategy for enhancing the reactivity of Mn(VII) and provided mechanistic insights into the GO-catalyzed redox reaction between SSX and Mn(VII).

Nitrogen-doped graphene for tetracycline removal via enhancing adsorption and non-radical persulfate activation

Nitrogen-doped graphene (NG) was synthesized via direct thermal annealing treatment. The obtained NG showed outstanding removal ability for tetracycline (TC) ascribed to enhanced adsorption and persulfate activation. The maximum TC adsorption capacity calculated from the Langmuir model of NG was 227.3 mg/g, which was 1.66 times larger than nitrogen-free graphene. The coexistence of NG and persulfate (PS) exhibited complete degradation of TC within 120 min attributed to the successful modification of nitrogen. Further analysis demonstrated that non-radical electron transfer was the dominant degradation pathway, which was different from the widely acknowledgeable radical mechanism. An electron donor-mediator-acceptor system was introduced, in which TC, NG, and PS performed as electron donor, mediator, and acceptor, respectively. The potential intermediates in the TC degradation process were detected and toxicity assessment was also performed. In addition, more than 75.8% of total organic carbon was removed, and excellent reusability was manifested in multiple adsorption and degradation experiments.

Selective and nonselective removal of hydrophobic compounds by coupling engineered FeOCl in a cathode-anode synergistic electrochemical platform

Efficient and selective removal of water pollutants remains a critical challenge. Here, we addressed this challenge by ingeniously engineering FeOCl via polyaniline intercalation and dodecyl group modification (FeOCl-P-S) to improve its activity and selectivity for the in situ removal of hydrophobic phenolic compounds. We further encapsulated the catalyst inside commercial cheap corundum balls and developed a "millimeter-scale reactor", which maintained a high efficiency of 86.02% after ten cycles with negligible physical changes. Moreover, we established the synergy between anodic (generating H+, O2, and IrO3) and cathodic reactions (utilizing H+ and O2) for H2O2 generation and direct anodic oxidation, an unexplored process, in a vertical bidirectional gas diffusion electrochemical system (VB-GDE). By combining the "reactor" and VB-GDE, we constructed a new platform for selective and nonselective continuous pollutant oxidation in a self-sustaining acidic environment with minimal chemical residues. This work presents a promising electrochemical technology for the efficient and selective removal of water pollutants.

Charging and discharging of humic acid geobattery induced by green rust and oxygenation: Impact on the fate and degradation of tribromophenol in redox-alternating groundwater environments

Humic acid (HA) and ferrous minerals (e.g. green rust, GR) are abundant in groundwater. HA acts as a geobattery that take up and release electrons in redox-alternating groundwater environments. However, the impact of this process on the fate and transformation of groundwater pollutants is not fully understood. In this work, we found that the adsorption of HA on GR inhibited the adsorption of tribromophenol (TBP) under anoxic conditions. Meanwhile, GR could donate electrons to HA, causing the electron donating capacity of HA rapidly increase from 12.7% to 27.4% in 5 min. The electron transfer process from GR to HA significantly increased the yield of hydroxyl radicals (•OH) and the degradation efficiency of TBP during GR-involved dioxygen activation process. Compared to the limited electronic selectivity (ES) of GR for •OH production (ES = 0.83%), GR-reduced HA improves the ES by an order of magnitude (ES = 8.4%). HA-involved dioxygen activation process expands the •OH generation interface from solid phase to aqueous phase, which is conducive to the degradation of TBP. This study not only deepens our understanding on the role of HA in •OH production during GR oxygenation, but also provides a promising approach for groundwater remediation under redox-fluctuating conditions.

Selective Removal of Organic Pollutants in Groundwater and Surface Water by Persulfate-Assisted Advanced Oxidation: The Role of Electron-Donating Capacity

The efficiency of persulfate-assisted advanced oxidation processes (PS-AOPs) in degrading organic pollutants is affected by the electron-donating capability of organic substances present in the water source. In this study, we systematically investigate the electron-donating capacity (EDC) difference between groundwater and surface water and demonstrate the dependence of removal efficiency on the EDC of target water by PS-AOPs with carbon nanotubes (CNTs) as a catalyst. Laboratory analyses and field experiments reveal that the CNT/PS system exhibits higher performance in organic pollutant removal in groundwater with a high concentration of phenols, compared to surface water, which is rich in quinones. We attribute this disparity to the selective electron transfer pathway induced by potential difference between PS-CNT and organic substance-CNT intermediates, which preferentially degrade organic substances with stronger electron-donating capability. This study provides valuable insights into the inherent selective removal mechanism and application scenarios of electron transfer process-dominated PS-AOPs for water treatment based on the electron-donating capacity of organic pollutants.

Strong coupling of super-hydrophilic and vacancy-rich g-C3N4 and LDH heterostructure for wastewater purification: Adsorption-driven oxidation

Adsorption and wettability are crucial components of catalytic oxidation. To increase the reactive oxygen species (ROS) generation/utilization efficiency of peroxymonosulfate (PMS) activators, defect engineering and 2D nanosheet characteristics were used to regulate electronic structures and expose more active sites. Two-dimensional (2D) super-hydrophilic heterostructure by connecting cobalt species modified nitrogen vacancy-rich g-C₃N₄ (V_n-CN) and LDH (V_n-CN/Co/LDH) with high-density active sites and multi-vacancies, as well as high conductivity and adsorbability, to expedite ROS generation. The degradation rate constant of ofloxacin (OFX) was 0.441 min^-1 via the V_n-CN/Co/LDH/PMS system, which was 1-2 orders greater than in the previous studies. Confirmation of the contribution ratios of various reactive oxygen species (ROS), SO₄^·- and ¹O₂ in bulk solution, O₂^·- on the catalyst surface was the most abundant ROS. The catalytic membrane was constructed utilizing Vn-CN/Co/LDH as the assembly element. The 2D membrane achieved the continuous effective discharge of OFX in the simulated water after 80 h/4 cycles of continuous flowing-through filtration-catalysis. This study provides fresh insights into designing a PMS activator for environmental remediation activated on demand.

Heterogeneous Fe-Co dual-atom catalyst outdistances the homogeneous counterpart for peroxymonosulfate-assisted water decontamination: New surface collision oxidation path and diatomic synergy

Heterogeneous catalysts lag far behind their homogeneous counterparts in activating peroxymonosulfate (PMS) for water decontamination due to the low site intrinsic activity and sluggish mass transfer. The single-atom catalyst can bridge the gap between heterogeneous and homogeneous catalysts, but the difficulty to break scaling relations originating from the site monotony restricts further efficiency upgradation. Herein through modulating the crystallinity of NH₂-UIO-66, a porous carbon support with ultrahigh surface area (1721.71 m² g^-1) is obtained to anchor the dual-atom FeCoN₆ site, which exhibits superior turnover frequency over single-atom FeN₄ and CoN₄ sites (13.07 versus 9.97, 9.07 min^-1). The as-synthesized composite thus outperforms the homogeneous catalytic system (Fe³⁺+Co²⁺) for sulfamethoxazole (SMZ) degradation, and the catalyst-dose-normalized kinetic rate constant (99.26 L min^-1 g^-1) exceeds reported values by 1∼2 orders of magnitude. Moreover, only 20 mg of the catalyst can run a fluidized-bed reactor to realize continuous zero discharge of SMZ in multiple actual waters for up to 8.33 h. Unlike all reported reaction routes, the catalysis on the diatomic site follows a new surface collision oxidation path, i.e. the dispersed catalyst adsorbs PMS to generate surface-activated PMS with high potential, which collides with surrounding SMZ and directly seizes electron from it to induce pollutant oxidation. Theoretical calculation indicates that the enhanced activity of FeCoN₆ site stems from the diatomic synergy, leading to stronger PMS adsorption, larger near-Fermi-level density of states and optimal global Gibbs free energy evolution. Overall, this work provides an effective strategy of constructing heterogeneous dual-atom catalyst/PMS process to achieve faster pollution control than homogeneous system, and sheds light on the interatomic synergetic mechanism for PMS activation.

Degradation of p-Nitrophenol by activated persulfate with carbon-based materials

The removal of p-nitrophenol (PNP) from wastewater was evaluated by the activated persulfate process using different materials - carbon xerogels (XG), carbon nanotubes (CNT), and activated carbon (AC) -, and also using such materials doped with nitrogen (XGM, CNTM and ACM). These carbon materials were impregnated with 2 wt.% of iron and tested in the oxidative process to assess the influence of their textural and surface chemical properties. The carbon-based materials' properties influence the efficiencies of the adsorption and oxidative processes; in adsorption, the materials with higher specific surface areas (S_BET), i.e. AC (824 m²/g) and Fe/AC (807 m²/g), have shown to be the most promising (having achieved a PNP removal of about 20%); on the other hand, in the activated persulfate process the carbon or iron-containing carbon materials with the highest mesoporous areas (S_meso) were the preferential ones - XG and Fe/XG, respectively - reaching removals of 47.3% and 75.7% for PNP and 44.9 and 63.3% for TOC, respectively. Moreover, the presence of nitrogen groups on the samples' surface benefits both processes, being found that PNP degradation and mineralization increase with the nitrogen content. The stability of the best materials (XGM and Fe/XGM) was evaluated during four cycles, being noticed that while XGM lost catalytic activity, the Fe/XGM sample remained stable without leaching of iron. The quantification of intermediate compounds formed during persulfate oxidation was performed, and only oxalic acid was detected, in addition to PNP, being that their contribution to the TOC measured was higher than 99%. Experiments carried out in the presence of radical scavengers proved that only the sulfate radical is present under the acidic conditions used. Complete PNP oxidation and TOC removal of ∼96% were reached for the activated persulfate process, proving to be more attractive than the Fenton one.

Dynamic coordination of two-phase reactions in heterogeneous Fenton for selective removal of water pollutants

The •OH-mediated heterogeneous Fenton reaction has been widely applied despite the limitations of low pollutant selectivity and unclear oxidation mechanism. Here we reported an adsorption-assisted heterogeneous Fenton process for the selective degradation of pollutants and systematically illustrated its dynamic coordination in two phases. The results showed that the selective removal was improved by (i) surface enrichment of target pollutants via electrostatic interactions including real adsorption and adsorption-assisted degradation and (ii) inducing the diffusion of H₂O₂ and pollutants from the bulk solution to the catalyst surface to trigger the homogeneous and surface heterogeneous Fenton reactions. Furthermore, surface adsorption was confirmed as a crucial but not necessary step for degradation. Mechanism studies demonstrated that •O₂^- and Fe³⁺/Fe²⁺ cycle increased •OH generation, which remained active in two phases within ⁓244 nm. These findings are critical for understanding the removal behavior of complex targets and expanding heterogeneous Fenton applications.

Probing the activation mechanism of nitrogen-doped carbonaceous materials for persulfates: Based on the differences between peroxymonosulfate and peroxydisulfate

The activation processes of persulfates by metal-free nitrogen-doped carbonaceous material (NCM) remain unclear due to their complex structures and heterogeneous nature. On the other hand, from the perspective of persulfates, it is possible to clarify the reaction between persulfates and NCM by considering the differences in activation behaviors between peroxymonosulfate (PMS) and peroxydisulfate (PDS). Our study aims to compare the differences between NCM-PDS and NCM-PMS using a fully metal-free NCM as a model catalyst. Firstly, NCM-PDS was more efficient than NCM-PMS in degrading phenolic compounds (PCs). Secondly, the stoichiometric ratio between consumed persulfates and DCP removed in the NCM-PDS (0.73) is lower than in the NCM-PMS (1.08). Thirdly, PMS and PDS adsorb on NCM in different ways, suggesting that the peak O-O bond in PDS has blue shifted from 814 cm^-1 to 805 cm^-1, while that of O-O bond in PMS has shifted from 889 cm^-1 to 834 cm^-1. Additionally, the hydrogen bond between the phenolic group and oxidants plays a critical role in PCs degradation by NCM-PDS, exhibiting a stronger pH effect and higher kinetic isotope effects (KIEs) than NCM-PMS. A proton-coupled electron transfer process has been proposed for PCs degradation using NCM-PDS, and a scheme of reaction pathways has been provided for the NCM-PMS/PDS-PCs system. The study results provide a deeper understanding of the activation of persulfates by NCM, as well as a strategy for selecting oxidants.

Competitive adsorption of sulfamethoxazole and bisphenol A on magnetic biochar: Mechanism and site energy distribution

Competitive adsorption and complementary adsorption between emerging pollutants has been observed in multiple studies. Investigation of the preference of pollutants for different types of adsorption sites can provide a supplementary perspective for understanding complementary adsorption. In this study, the simultaneous adsorption of two typical emerging pollutants, sulfamethoxazole (SMX) and bisphenol A (BPA), on magnetic biochar (MBC-1) was investigated. The results showed that the modification with ferric chloride optimized the surface properties of biochar (aromaticity, hydrophobicity, and oxygen-containing functional groups, etc.), and helped to remove SMX and BPA through various interactions. The equilibrium adsorption capacity of the two adsorbents was inhibited by competitive adsorption in the mixed solute systems, which was due to the same adsorption mechanism. When pH = 7, the SMX and BPA adsorption mainly involved pore filling, hydrophobic effect, π-π EDA, and hydrogen bonding. In addition, electrostatic force, surface coordination, and ion exchange have also been proven to be related to the adsorption of SMX and BPA. In the co-adsorption system, BPA's competitive advantage might be due to its superior hydrophobicity, charge property, and molecular diameter. In the competitive adsorption experiment, the total adsorption capacity (Q_i) of the competitive solute exceeded the adsorption inhibition (△Q_i) of the main solute, indicating that the two solutes occupied their preferred adsorption sites, which confirmed the complementary adsorption phenomenon. Complementary adsorption can be explained by the preference of SMX and BPA for different types of adsorption sites. BPA preferentially occupied high-energy sites in the co-adsorption system, such as π-π EDA interaction, ion exchange, and surface coordination. At the same time, SMX tended to be removed by hydrophobic interaction and hydrogen bonding.

Metal organic framework-derived recyclable magnetic coral Co@Co3O4/C for adsorptive removal of antibiotics from wastewater

The menace posed by antibiotic contamination to humanity has increased due to the absence of efficient antibiotic removal processes in the conventional waste water treatment methods from the hospitals, households, animal husbandry, and pharma industry. Importantly, only a few commercially available adsorbents are magnetic, porous, and have the ability to selectively bind and separate various classes of antibiotics from the slurries. Herein, we report the synthesis of a coral-like Co@Co3O4/C nanohybrid for the remediation of three different classes of antibiotics - quinolone, tetracycline, and sulphonamide. The coral like Co@Co3O4/C materials are synthesized via a facile room temperature wet chemical method followed by annealing in a controlled atmosphere. The materials demonstrate an attractive porous structure with an excellent surface-to-mass ratio of 554.8 m2 g-1 alongside superior magnetic responses. A time-varying adsorption study of aqueous nalidixic acid solution on Co@Co3O4/C nanohybrids indicates that these coral-like Co@Co3O4/C nanohybrids could achieve a high removal efficiency of 99.98% at pH 6 in 120 min. The adsorption kinetics data of Co@Co3O4/C nanohybrids follow a pseudo-second-order reaction kinetics suggesting a chemisorption effect. The adsorbent has also shown its merit in reusability for four adsorption-desorption cycles without showing significant change in the removal efficiency. More in-depth studies validate that the excellent adsorption capability of Co@Co3O4/C adsorbent attributing to the electrostatic and π-π interaction between adsorbent and various antibiotics. Concisely, the adsorbent manifests the potential for the removal of a wide range of antibiotics from the water alongside showing their utility in the hassle-free magnetic separation.

Fe-N co-doped coral-like hollow carbon shell toward boosting peroxymonosulfate activation for efficient degradation of tetracycline: Singlet oxygen-dominated non-radical pathway

Fe-N co-doped coral-like hollow carbon shell (Fe-N-CS) was synthesized via a simply impregnation-pyrolysis method. The Fe-N-CS showed an excellent ability for activating peroxymonosulfate (PMS), which could degrade about 93.74% tetracycline (20 mg/L) in 12 min. The Fe-N-CS/PMS system exhibited a good anti-interference capacity of various pH, inorganic anions, HA and different water qualities. More importantly, the Fe nanoparticles were anchored uniformly in the carbon layer, effectively limiting the metal leaching. The quenching tests and electron spin resonance (ESR) manifested that non-radical singlet oxygen (¹O₂) was the main reactive oxygen species (ROS) for TC degradation. The mechanism study showed that Fe nanoparticles, defect and graphite N played a key role in activating PMS to produce ROS. Moreover, three probable degradation pathways were proposed by using LC-MS measurements. Generally, this work had a new insight for the synthesis of heterogeneous Fe-N-C catalysts in the advanced oxidation process based on PMS.

New insights into engineering the core size and carbon shell thickness of Co@C core-shell catalysts for efficient and stable Fenton-like catalysis

Herein, we engineered the cobalt core size and carbon shell thickness of Co@C by molten salt electrolysis (MSE) to investigate the enhanced essence of decreasing core size as well as the shell thickness dependence-mediated transition of catalytic mechanisms. We found that the reaction activation energy (RAE) of Co@C/peroxymonosulfate (PMS) systems was intimately dependent on the core sizes for sulfamethoxazole (SMX) degradation. The smaller core size of 26 nm provided a lower RAE of 13.39 kJ mol^-1. In addition, increasing carbon shell thicknesses of Co@C altered the catalytic mechanisms from a radical pathway of SO₄^•- and •OH to to a non-radical pathway of ¹O₂ and electron-transfer process (ETP), which were verified by experimental results and density functional theory (DFT) calculations. Interestingly, increasing carbon shell thicknesses promoted the charge transfer between Co metal slab and carbon shell, increased the adsorption energy of PMS molecule on the Co@C slab, and decreased the length of OO, which favoured the occurrence of non-free radical processes.

Facilely achieved enhancement of Fenton-like reactions by constructing electric microfields

In this work, we found that the presence of non-active ZnO crystals greatly accelerated the degradation of Bisphenol A (BPA) by 3.7 folds in the peroxymonosulfate (PMS, HSO₅^-)/Co₃O₄ system. Our mechanistic study revealed that the ZnO particles would create negative electric microfields around them, which are closely related with the zeta potentials (ζ) of ZnO and affected by solution pH. According to COMSOL simulation, the electrostatic repulsion between ZnO and PMS would drive HSO₅^- toward active Co₃O₄ surface, leading to the concentration increasing of HSO₅^- around active Co₃O₄ particles, which will then improve the degradation performance. The particle size of ZnO will also affect the promoting effect greatly by COMSOL simulation. Therefore, this study for the first time reveals synergy of electric microfields for enhanced heterogeneous Fenton-like reactions, providing a low-cost and effective strategy for enhanced persulfate catalysis.

Sulfur and nitrogen co-doped magnetic biochar coupled with hydroxylamine for high-efficiency of persulfate activation and mechanism study

Biochar has recently become a central issue in advanced oxidation processes (AOPs) based on peroxydisulfate (PDS) activation. However, the PDS activation by biochar must be improved. In this study, S, N co-doped magnetic biochar (IBC) was prepared by a simple impregnation-pyrolysis method using Eichhornia crassipes stems with inherent sulfur and nitrogen as the raw materials for biochar. The reductant hydroxylamine (HA) was employed to further enhance PDS activation by the IBC for organic pollutant degradation. Incorporating HA in PDS activation over IBC significantly improved its compatibility with complex water, catalytic degradation, stability performance, and mineralization rate of organic pollutants. The outstanding performance of the HA/PDS/IBC system for organic degradation was due to the increased free radicals SO₄^·-, O₂^·-, and non-radical ¹O₂ generated, as well as the electrons transferred between IBC, PDS, and organic pollutants, which were verified by electron paramagnetic resonance (EPR) detection and electrochemical characterizations. Furthermore, HA-enhanced Fe(III)/Fe(II) cycling, surface functional groups, and S and N doping contributed to the generation of reactive oxygen species (ROS). Moreover, the toxicity assessment indicated that the toxicity of the degradation intermediates decreased. Therefore, this research proposes a new insight into the enhanced degradation of pollutants by increasing PDS activation using biochar-based catalytic materials.

Mechanistic and structure investigation of the KOH activation ZIF-8 derived porous carbon as metal-free for unprecedented peroxymonosulfate activation degradation of bisphenol A

The high-performance and free secondary pollution of the catalysts are the most critical issues in the peroxymonosulfate-based advanced oxidation processes (PMS-AOPs). In this research, the KOH was used to activate ZIF-8 derived carbon materials to synthesize the NC-KOH-x (x = 700, 800, 900 °C), which was an effective metal-free PMS activator. As-prepared NC-KOH-x showed significant improvement not only pore structure and BET surface area but also CO groups, and graphite N content, which were beneficial for the adsorptive and oxidative reaction. The NC-KOH-900 as an excellent metal-free carbon-catalyst exhibited considerable reactivity for bisphenol A (BPA) removal in broad pH ranges. Almost 100% of BPA was eliminated using 9 mg NC-KOH-900, 0.5 mM PMS within 60 min. Interestingly, It was found that the BPA removal efficiency by adding PMS after saturated adsorption of NC-KOH-x was better than that by adding NC-KOH-x and PMS simultaneously. Electronic paramagnetic resonance (EPR) and quenching experiments results demonstrated that the BPA degradation relied mainly on the nonradical (¹O₂) pathways and the defects (I_D/I_G), graphitic nitrogen, pyridinic nitrogen, and CO were verified as leading catalytic sites for BPA degradation via PMS activation. Finally, degradation pathways of BPA were proposed and the Toxicity Estimation Software Tool (T.E.S.T.) result implicated that the intermediates of BPA were environmentally friendly to the microorganism and recycled in the ecosystem. The outcomes of this study illustrated the NC-KOH-x owned many merits of state-of-the-art, eco-friendly, and high-performance for great potential practical application value.

Carbon nanotubes accelerates the bio-induced vivianite formation

Vivianite widely existed in digested sludge and activated sludge as a potential phosphate resource recovered from wastewater treatment plants (WWTPs). As an important product of extracellular electron transfer (EET) and biological iron reduction, the production of vivianite can be enhanced by conductive materials. Carbon nanotubes (CNTs) with excellent electrical conductivity have been reported to promote electron transfer, which was applied in wastewater treatment to accelerate the degradation of the contaminants. However, the impact of CNTs on vivianite formation was barely reported. In this study, the iron reduction, vivianite recovery, and the biotoxicity of CNTs were investigated in order to determine the influence of CNTs towards the vivianite production. The enhancement of vivianite production after CNTs adding reached up to 17 % by promoting the electron transfer between dissimilative iron-reducing bacteria (DIRB) and Fe(III). However, at the initial stage (0-24 h), Fe(III) reduction efficiency decreased by 81 % after inoculating with sewage sludge, which was attributed to CNTs destroying of the cell membrane (as indicated by SEM, CLSM and AFM analysis). The biotoxicity of CNTs stimulated DIRB to secret extracellular polymeric substances (EPS) and form bio-flocs to resist the physical puncture. After 48 h, the proportion of living DIRB in 1000 mg/L CNTs batch increased to 98 %, which was 79 % higher than 12 h. As a result, the vivianite recovery of raw sewage with 1000 mg/L CNTs increased to 44 ± 1 %, which was 33 % higher than that in the CNT-0.

Fast peroxydisulfate oxidation of the antibiotic norfloxacin catalyzed by cyanobacterial biochar

Peroxydisulfate (PDS) is a common oxidant for organic contaminant remediation. PDS is typically activated by metal catalysts to generate reactive radicals. Unfortunately, as radicals are non-selective and metal catalysts may cause secondary contamination, alternative selective non-radical pathways and non-metal catalysts need attention. Here we investigated PDS oxidation of commonly detected antibiotic Norfloxacin (NOR) using cyanobacterial nitrogen rich biochars (CBs) as catalysts. NOR was fully degraded by CB pyrolysed at 950 °C (CB950) within 120 min. CB950 caused threefold faster degradation than low pyrolysis temperature (PT) CBs and achieved a maximum surface area normalized rate constant of 4.38 × 10^-2 min^-1 m^-2 L compared to widely used metal catalysts. CB950 maintained full reactivity after four repeated uses. High defluorination (82%) and mineralization (>82%) were observed for CB950/PDS. CBs were active over a broad pH range (3-10), but with twice as high rates under alkaline compared with neutral conditions. NOR is degraded by organic, ^•OH and SO₄^•- radicals in low PT CBs/PDS systems, where the presence of Mn^II promotes radical generation. Electron transfer reactions with radicals supplemented dominate high PT CBs/PDS systems. This study demonstrates high PT biochars from algal bloom biomass may find use as catalysts for organic contaminant oxidation.

Metal-free graphene-based catalytic membranes for persulfate activation toward organic pollutant removal: a review

Owing to their ultrathin two-dimensional structure and efficient catalytic ability for persulfate activation, graphene-based nanocarbons exhibit considerable application potential in fabricating carbonaceous composite membranes for in situ catalytic oxidation to remove organic pollutants. This approach offers significant advantages over conventional batch systems. However, the relationships between the physicochemical properties of carbon mats and performance of graphene-based catalytic membranes in water purification remain ambiguous. Herein, we summarize the main mechanisms of in situ catalytic oxidation and the facile fabrication strategies of carbonaceous composite membranes. Different factors influencing the performance of graphene-based catalytic membranes are comprehensively discussed. The defective level, heteroatom doping, and stacking morphology of carbon mats and operational conditions during filtration play critical roles in the oxidative degradation of target pollutants. Long-term operation leads to the deterioration of catalytic activity and transmembrane pressure, especially in the complex water matrix. Finally, the present challenges and future perspectives are presented to improve the anti-fouling performance and catalytic stability of membranes and develop scalable fabrication methods to promote the engineering applications of in situ catalytic oxidation in real water purification.

Resource utilization of agricultural waste: Converting peanut shell into an efficient catalyst in persulfate activation for degradation of organic pollutant

Agricultural waste was characterized by large quantity and low degree of resource utilization. The peanut shell waste was converted into value-added biochar to alleviate the pollution of dyeing wastewater, which caters to the concept of resource recovery and sustainable utilization. In this work, peroxydisulfate (PDS) could be efficiently activated by biochar obtained by pyrolysis at 700 °C (BC) and Acid Orange 7 (AO7) was rapidly eliminated with 96% removal ratio in 10 min. Meanwhile, BC catalyst performed good stability and reusability. In addition, remarkable removal performance within 40 min (>94%) could be achieved in a wide range of pH (3.0-11.0). Through series characterizations, it was found that 700 °C was the critical pyrolysis temperature to prepare material with excellent property mainly attributing to large specific surface area (SSA), followed by high defect structure and rich C-O. It was speculated that radical pathway mainly especially surface-bounded radicals (SO₄^•-、•OH、O₂^-•) worked in the degradation of AO7. Specifically, abundant and typical oxygen-containing functional groups (OFGs) and defect structure catalytic sites of BC enhanced PDS activation. In addition, various radicals participated the whole degradation processes, such as the cleavage of azo bond (-NN-), hydroxylation, deamination and desulfurization.

Endocrine disrupting chemicals in the environment: Environmental sources, biological effects, remediation techniques, and perspective

Endocrine disrupting chemicals (EDCs) have been identified as emerging contaminants, which poses a great threat to human health and ecosystem. Pesticides, polycyclic aromatic hydrocarbons, dioxins, brominated flame retardants, steroid hormones and alkylphenols are representative of this type of contaminant, which are closely related to daily life. Unfortunately, many wastewater treatment plants (WWTPs) do not treat EDCs as targets in the normal treatment process, resulting in EDCs entering the environment. Few studies have systematically reviewed the related content of EDCs in terms of occurrence, harm and remediation. For this reason, in this article, the sources and exposure routes of common EDCs are systematically described. The existence of EDCs in the environment is mainly related to human activities (Wastewater discharges and industrial activities). The common hazards of these EDCs are clarified based on available toxicological data. At the same time, the mechanism and effect of some mainstream EDCs remediation technologies (such as adsorption, advanced oxidation, membrane bioreactor, constructed wetland, etc.) are separately mentioned. Moreover, our perspectives are provided for further research of EDCs.

pH-dependent generation of radical and nonradical species for sulfamethoxazole degradation in different carbon/persulfate systems

The impacts of pH on purification efficiency can be phenomenal in advanced oxidation processes (AOPs), because solution pH affects persulfate (PS) activation processes. However, consensus has not been reached on the regimes of pH-regulated oxidation in persulfate-based AOPs (PS-AOPs). Particularly, the impacts of pH on carbon-catalyzed generation of radical and nonradical species remain unclear. In this work, we evaluated three typical carbonaceous materials including pyrolytic carbon (PC), activated carbon (AC), and carbon nanotube (CNT) to activate PS for sulfamethoxazole (SMX) degradation within a pH range from 4 to 9. The experiment revealed pH-dependent SMX removal in PC/PS, AC/PS, and CNT/PS, and the kinetics followed an order of pH 4 > pH 7 > pH 9. Solution pH simultaneously affected SMX adsorption and degradation, but the latter was more profound. Chemical quenching experiment, electrochemical measurement, kinetics calculation, and ATR-FTIR tests collectively revealed that high pH was not favorable for both radical and nonradical oxidation. In the PC/PS system, increased pH decreased the amount of phenolic -OH on PC surface, thereby restraining the generation of SO₄^•- and ^•OH due to the lack of electron donors. For AC/PS system, elevated pH hindered the interactions between AC and PS, thus suppressing the formation of surface-bound radicals. CNT/PS initiated an electron-transfer pathway, and increased pH reduced the oxidation potential of surface CNT-PS* complex, which was not favorable for nonradical oxidation of adsorbed pollutants. Therefore, outcomes of this work will advance the current knowledge on the intrinsic impacts of pH in PS-AOPs catalyzed by carbonaceous materials for wastewater purification.

Degradation of tetracycline by activating persulfate using biochar-based CuFe2O4 composite

Biochar derived from Lentinus edodes (LBC) and CuFe₂O₄ (CuFe₂O₄@LBC) composites were prepared by the hydrothermal method, and were applied to activate persulfate (PDS) for degrading tetracycline (TC) in a wide pH range. The CuFe₂O₄@LBC composites were characterized by XRD, FTIR, SEM, and XPS. LBC-derived biochars greatly reduced the aggregation of CuFe₂O₄ particles and enhanced the catalytic performance of CuFe₂O₄. CuFe₂O₄@LBC catalyst could remove 85% of tetracycline within 100 min under visible light. In addition, the removal rate of TC reached 76% after five cycles, indicating that the composite had good stability and reusability. Simple classical quenching experiments suggested that the degradation of TC could be mainly attributed to •OH and •S [Formula: see text].