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Diospyros lotus L., which belongs to the Ebenaceae family, is used in folk medicine for treating anemia, fatigue, insomnia, and hepatitis. In the present study, supercritical CO2 fluid extraction (SFE) was used to extract Diospyros lotus L. essential oil, and its antioxidant, antimicrobial, and cytotoxic activities were investigated. The chemical composition of the essential oil was investigated using GC/MS. The antioxidant capacity was evaluated via 1,1diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging and hydroxyl radical scavenging. The minimum inhibitory concentration (MIC) using the broth microdilution method was applied to investigate antimicrobial activities. The cytotoxic activity of the essential oil was measured using a standard 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide (MTT) assay. The GC–MS analysis showed that Diospyros lotus L essential oil contained 25 components, mainly including 5-hydroxymethylfurfural (50.90%), 2-methylhexadecan-1-ol (19.97%), 2-cis-9-octadecenyloxyethanol (5.46%), dibutyl phthalate (4.84%), and n-hexadecanoic acid (4.20%). The IC50 values of the essential oil in the DPPH assay and hydroxyl radical scavenging activity were 46.46 ± 1.70 μg/mL and 0.551 ± 0.0267 mg/mL, respectively. Furthermore, at concentrations below 50 μg/mL, the evaluation of cell viability showed no cytotoxicity in the human embryonic kidney cell line 293T. The results show that Diospyros lotus L. essential oil has antimicrobial and antioxidant effects, and has no toxicity on 293T cells at low concentrations, indicating potential health benefits. [ABSTRACT FROM AUTHOR]

As reported, the persistent toxic and harmful pollutant bisphenol A (BPA) from industrial emissions has been consistently found in aquatic environments inhabited by humans. Periodate (PI)-based advanced oxidation processes (AOPs) have been employed to degrade BPA, although activating PI proves more challenging compared to other oxidants. A novel nano iron metal catalyst, sulfided nanoscale iron-nickel bimetallic nanoparticle supported on biocarbon (S-(nFe0-Ni)/BC) was synthesized and utilized to activate PI for the removal of BPA. The morphology, structure, and composition of S-(nFe0-Ni)/BC were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive spectrometer (SEM–EDS), and fourier-transform infrared spectrum (FTIR). The catalyst demonstrates an excellent ability to activate PI, achieving a BPA removal efficacy of 86.4%, accompanied by a 33% reduction in total organic carbon (TOC) in the {S-(nFe0-Ni)/BC}/PI system. BPA degradation exhibited a significant change at the 5-min mark. In the first stage (0–5 min), nonlinear dynamic fitting research, combined with scavenging experiments, unveiled the competitive degradation of pollutants primarily driven by iodate radical ( IO 3 · ), singlet oxygen 1 O 2 , and hydroxyl radical ( · OH ). The competitive dynamics aligned with the ExpAssoc model. The contribution rates of different active species during the second stage (5–120 min) were calculated. The contributions of main species to BPA removal follow the order of IO 3 · > 1 O 2 > · OH throughout the entire process. The influence of various parameters, such as the dosage of S-(nFe0-Ni)/BC, initial PI concentration, BPA concentration, pH, temperature, and the presence of coexisting anions, was also examined. Finally, a plausible reaction mechanism in the system is proposed, suggesting that the {S-(nFe0-Ni)/BC}/PI system involves a heterogeneous synergistic reaction occurring primarily on the surface of S-(nFe0-Ni)/BC. Therefore, this study proposes a promising approach for PI-based AOPs to degrade organic pollutants, aiming to mitigate the irreversible harm caused by such pollutants to organisms and the environment. [ABSTRACT FROM AUTHOR]

The efficient use of renewable X/γ-rays or accelerated electrons for chemical transformation of CO2 and water to fuels holds promise for a carbon-neutral economy; however, such processes are challenging to implement and require the assistance of catalysts capable of sensitizing secondary electron scattering and providing active metal sites to bind intermediates. Here we show atomic Cu-Ni dual-metal sites embedded in a metal-organic framework enable efficient and selective CH3OH production (~98%) over multiple irradiated cycles. The usage of practical electron-beam irradiation (200 keV; 40 kGy min−1) with a cost-effective hydroxyl radical scavenger promotes CH3OH production rate to 0.27 mmol g−1 min−1. Moreover, time-resolved experiments with calculations reveal the direct generation of CO2•‒ radical anions via aqueous electrons attachment occurred on nanosecond timescale, and cascade hydrogenation steps. Our study highlights a radiolytic route to produce CH3OH with CO2 feedstock and introduces a desirable atomic structure to improve performance. Most approaches for CH3OH production focus on thermochemical, electrolytic, and photolytic processes. Here the authors report a radiolytic route to produce CH3OH from CO2 and water by atomic Cu-Ni dual sites embedded in a metal-organic framework. [ABSTRACT FROM AUTHOR]

Radio-fluorogenic hydrogel dosimeters are urgently needed in radiotherapy for 3D dose verification. However, few hydrogel sensors have been reported at low absorbed doses under 2 Gy which meets the requirements of clinical practice. Here, we report a new type of gold-nanoparticle-enhanced radio-fluorogenic agarose hydrogel with coumarin as the dose-responsive material. An optimal composition of 3 wt% of agarose, 0.1 mM of gold nanoparticles, and 0.5 mM coumarin was selected. The addition of gold nanoparticles enhanced the hydroxyl radicals generated from the radiolysis of water, which can react with coumarin and generate fluorescent 7-hydroxy-coumarin and, eventually, achieve low-dose verification of 0–2.4 Gy with a high linear correlation coefficient. These findings provide an effective method for 3D dose verification, and will inspire the development of other radio-fluorogenic sensing hydrogels as well. [ABSTRACT FROM AUTHOR]

Owing to the easy over‐oxidation, it is a promising yet challenging task to explore renewable carbon resources to control the sunlight‐driven selective catalytic oxidation of biomass‐derived 5‐hydroxymethylfurfural (HMF), producing important chemical feedstocks, namely, less‐oxidized 2,5‐diformylfuran (DFF) and 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA). Herein, we have developed a photocatalyst by anchoring a Ru complex on CdS quantum dots, which achieves selective oxidation of HMF toward DFF or HMFCA with high conversion (>81 %) and selectivity (>90 %), based on the controllable generation of two oxygen radicals under different atmospheres. Such selective conversion can also work well outside the laboratory by using natural sunlight. In particular, the selective production of HMFCA through photocatalytic HMF oxidation is achieved for the first time. More importantly, our photocatalyst is applicable for the selective oxidation of other compounds with hydroxyl and aldehyde groups. [ABSTRACT FROM AUTHOR]

Recently, graphitized carbon nitride (g-C 3 N 4) is widely used as a metal-free photocatalyst for photocatalytic hydrogen peroxide (H 2 O 2) generation. However, its photocatalytic activity still suffers from the poor separation efficiency of charge carrier and weak adsorption ability towards dioxygen. Herein, a series of polydopamine (PDA) surface-modified g-C 3 N 4 composites (CNPX) are successfully fabricated through a self-assembled method. The optimum material, i.e. CNP40, produced H 2 O 2 of 69.0 μM/L under visible-light irradiation for 3 h, demonstrating 4.6-fold higher activity in comparison with the pristine g-C 3 N 4. Meanwhile, the apparent quantum yield (AQY) reached as high as 1.91% over CNP40 under monochromatic irradiation of 420 nm, which is 6.2-fold higher than CN. It is identified that the remarkably increased photocatalytic activity is contributed to the significantly promoted charge separation and dioxygen adsorption. This present work could provide a novel environmental-friendly material for the efficient photocatalytic H 2 O 2 production. • Loading PDA with various thickness on the surface of g-C 3 N 4 through simply adjusting the polymerization time of DA. • PDA's loading introduces rich hydroxyl group on the surface of CN/PDA-X catalyst. • The introduced hydroxyl group simultaneously promote charge-carriers separation and dioxygen adsorption. • The AQY over CN/PDA-40 reach as high as 1.91% at 420 nm, being 6.2 times higher than the pristine g-C 3 N 4. [ABSTRACT FROM AUTHOR]

• In-situ generated FeO x and MnO x are used for membrane cleaning. • Flux recovery could be higher than 95% by the proposed method. • Efficient membrane cleaning are achieved by low H 2 O 2 dosage and short time. • PAC is a key factor for MnO x removal and membrane cleaning. Preoxidation-ultrafiltration process is an effective method for Fe2+ and Mn2+removal, in which Fe2+ (Mn2+) are firstly oxidized to FeO x (MnO x), then collected by the ultrafiltration membrane. However, the simultaneous presence of Fe2+, Mn2+, and organics in feed can cause severe membrane fouling, which inhibits the overall performance of this method prominently. In this study, a novel FeO x +MnO x +H 2 O 2 membrane cleaning method is proposed based on the idea of turning in-situ generated membrane foulants, i.e., FeO x +MnO x , into the catalysts for membrane cleaning. The results demonstrate that the FeO x +MnO x +H 2 O 2 system can achieve more than 95% membrane flux recovery and remove almost all irreversible membrane foulants within only 5 min and with only 0.5 % w t % H 2 O 2 solution. The outstanding performance of the system is mainly attributed to the catalytic decomposition of H 2 O 2 to generate both highly reactive radicals, such as hydroxyl radicals (·OH), and abundant oxygen. In addition, when the membrane is loaded by only MnO x , polyaluminium chloride (PAC) as the coagulator demonstrates prominent influence on the performance of membrane cleaning. However, PAC makes almost no contribution to membrane cleaning when the membrane is loaded by FeO x. This is because coagulation induced by PAC exerts more prominent impact on the particle size distribution of MnO x than that of FeO x. In conclusion, the catalytic decomposition of H 2 O 2 by in-situ generated FeO x +MnO x is a promising advanced oxidation process to achieve outstanding membrane cleaning performance under the condition of low H 2 O 2 concentration and no extra dosage of catalysts. The novel membrane cleaning system exhibits high potential for the practical membrane treatment processes to treat water with high contents of Fe and Mn. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • BQ improved efficiency of the Fe(III)/PMS system via boosting Fe(II) regeneration. • SO 4 •−, •OH and Fe(IV) simultaneously existed in the BQ/Fe(III)/PMS system. • Activation mechanism was clarified and degradation pathways were proposed. • Cl− inhibited ATZ degradation and caused chlorinated byproducts accumulation. Fe(II)-involved advanced oxidation processes could effectively degrade refractory contaminants, but the slow transformation of Fe(III) to Fe(II) limits their wide application. Herein we reported that p -benzoquinone (BQ) could accelerate Fe(III)/Fe(II) cycle and promote atrazine (ATZ) degradation in the Fe(III)/peroxymonosulfate (Fe(III)/PMS) system through reconstructing active Fe(II)/PMS system. Under the identical experimental conditions, ATZ degradation efficiency in the BQ/Fe(III)/PMS system (99.8%) was superior to that in the Fe(III)/PMS system (23.2%), suggesting the indispensable role of BQ in Fe(II) regeneration and PMS activation. Reactive species sulfate radical (SO 4 •−), hydroxyl radical (•OH) and ferryl ion (Fe(IV)) were involved in the BQ/Fe(III)/PMS system based on alcohol quenching experiments, ESR tests and the selective transformation from methyl phenyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO 2). ATZ degradation mechanism was proposed based on LC-MS detection, among which dealkylation and dechlorination-hydroxylation were the dominant transformation pathways. The BQ/Fe(III)/PMS system showed satisfactory catalytic performance at pH 2.5–7.0 and low Fe(III) concentration, which expanded the pH range and avoided the addition of a large amount of Fe. More importantly, the increase of PMS concentration not only enhanced the oxidative degradation of ATZ and its two main chlorinated byproducts (atrazine-desethyl (DEA) and atrazine-desisopropyl (DIA)), but also facilitated the removal of toxic BQ. Cl− inhibited the degradation of ATZ and caused the accumulation of DEA and DIA, and the higher Cl−, the more obvious this effect. This study provided a new approach to improve the Fe(III)/PMS system by boosting Fe(III)/Fe(II) cycle with quinons. [ABSTRACT FROM AUTHOR]

The O3/PMS system has appeared as an effective wastewater treatment method because of the simultaneous generation of hydroxyl radicals (•OH) and sulfate radicals (SO4•−). Many research achievements have been made on the degradation of micropollutants and the reaction mechanism of the O3/PMS system. However, an integral understanding of the O3/PMS system is lacking, which limits the development of safe and effective AOP-based water treatment schemes. Therefore, in this review, the degradation effects, toxicity changes, and reaction mechanisms of various micropollutants in the O3/PMS system are reviewed. The formation of oxidation by-products (OBPs) is an important issue that affects the practical application of O3/PMS systems. The formation mechanism and control methods of OBPs in the O3/PMS system are overviewed. In addition, the influence of different reaction conditions on the O3/PMS system are comprehensively evaluated. Finally, future research needs are proposed based on the limited understanding of O3/PMS systems in the degradation of micropollutants and formation of OBPs. Specifically, the formation rules of several kinds of OBPs during the O3/PMS system are not completely clear yet. Furthermore, pilot-scale research, the operational costs, sustainability, and general feasibility of the O3/PMS system also need to be studied. This review can offer a comprehensive assessment on the O3/PMS system to fill the knowledge gap and provide guidance for the future research and engineering applications of the O3/PMS system. Through this effort, the O3/PMS system can be better developed and turned towards practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Enhanced degradation of OCs was obtained by TAP in the presence of Cl−. • Different reactive species contributed to OCs degradation during Cl−/TAP oxidation. • TOC removal efficiencies were 52.6 %–69.0 % using TAP in the existence of Cl−. • The concentrations of typical CBPs were 17.2 μg/L–86.3 μg/L in Cl−/TAP system. The effect of chloride ion (Cl−) on the degradation of organic contaminants (OCs) by thermally activated peroxymonosulfate (TAP) was assessed in this study. P -aminobenzoic acid (PABA), sulfadiazine (SDZ), bisphenol A (BPA), and chloramphenicol (CAP) were employed as model OCs with different structure. The degradation efficiencies of PABA, SDZ, BPA, and CAP were respectively 76.4 %, 90.8 %, 10.1 %, and 14.5 % by TAP (70 °C) after 60 min treatment, further raised to 97.6 %, 97.4 %, 55.2 %, and 30.5 % in the presence of Cl− (1 mM). When Cl− concentration increased to 10 mM, PABA and SDZ were completely degraded respectively after 7 min and 10 min, 97.1 % of BPA and 59.5 % of CAP were removed within 60 min. In TAP system, PABA and SDZ were primarily degraded by direct peroxymonosulfate (PMS) oxidation, while BPA and CAP were mostly removed by hydroxyl radical and sulfate radical oxidation. In Cl−/TAP mixtures, the degradation of PABA and BPA was mainly attributed to hypochlorous acid oxidation, SDZ was chiefly removed via direct PMS oxidation, and CAP was principally oxidized by radicals. Furthermore, the intermediate products of OCs degradation during Cl−/TAP oxidation were identified, and primary degradation pathways were proposed. The removal efficiencies of total organic carbon were markedly improved from 19.3 % to 25.3 % by TAP to 52.6 %–69.0 % in Cl/TAP system. The concentrations of typical chlorinated by-products after OCs oxidation were 17.2 μg/L–86.3 μg/L in Cl−/TAP system. Considering the complexity of actual wastewater, 51.3 %–100 % removal efficiencies of OCs by TAP oxidation were achieved in Cl−-containing secondary effluent. Understanding the role of Cl− in OCs degradation is essential for the practical application of Cl−/TAP oxidation in advanced wastewater treatment. [ABSTRACT FROM AUTHOR]

This study presents a catalytic membrane based on cobalt-loaded carbon nanotubes and graphene oxide (Co@CNT-GO). Cobalt, serving as the active center, efficiently activates peroxymonosulfate for the degradation of organic compounds in transmembrane water. The uniform dispersion and firm loading of Co on CNT prevent the aggregation and leakage issues typically associated with conventional catalysts. The two-dimensional channels formed by the vacuum-assisted self-assembly of CNT and GO enhance the probability of contact between organic compounds and Co and prolong the contact duration thereby ensuring catalytic efficiency while maintaining a low water permeability resistance. The water flux of the catalytic membrane is 90 L/m2/h, and the atrazine removal efficiency is more than 92%, maintaining high stability even after continuous operation for 72 h. The generated active free radicals, including sulfate radicals, hydroxyl radicals, and singlet oxygen, synergistically facilitate the mineralization of organic compounds. Furthermore, the presence of oxygen vacancies on CNT accelerates the redox cycle of ≡ Co(II)/≡Co(III), sustaining the catalytically active center. Compared to the precursor catalytic membrane, Co@CNT-GO catalytic membrane possesses the characteristics of high removal efficiency and high flux, holding promise as a platform technology for the rapid and precise treatment of organic pollutants in contaminated water. [Display omitted] • Membranes are prepared via vacuum-assisted self-assembly of Co@CNT-GO. • Catalytic oxidation process occurs in 2D nanochannels filled with 1D nanotubes. • Co@CNT-GO membrane achieves almost 100% removal of ATZ within 175 ms. • Oxygen vacancies accelerate the redox cycle of ≡ Co(II)/≡Co(III). [ABSTRACT FROM AUTHOR]

• The simulated sunlight/monochloramine system effectively degraded microcontaminants. • The established model well simulated roles of Cl∙, HO∙, Cl 2 ∙−, and photodegradation. • Cl∙ and HO∙ were main radicals responsible for degrading ibuprofen and carbamazepine. • DBPs were analyzed at different reaction times and after 24 h of post-chloramination. As an eco-friendly and sustainable energy, solar energy has great application potential in water treatment. Herein, simulated sunlight was for the first time utilized to activate monochloramine for the degradation of environmental organic microcontaminants. Various microcontaminants could be efficiently degraded in the simulated sunlight/monochloramine system. The average innate quantum yield of monochloramine over the wavelength range of simulated sunlight was determined to be 0.068 mol/Einstein. With the determined quantum yield, a kinetic model was established. Based on the good agreement between the simulated and measured photolysis and radical contributions to the degradation of ibuprofen and carbamazepine, the major mechanism of monochloramine activation by simulated sunlight was proposed. Chlorine radical (Cl∙) and hydroxyl radical (HO∙) were major radicals responsible for microcontaminant degradation in the system. Moreover, the model facilitated a deep investigation into the effects of different reaction conditions (pH, monochloramine concentration, and water matrix components) on the degradation of ibuprofen and carbamazepine, as well as the roles of the involved radicals. The differences between simulated and measured degradation data of each microcontaminant under all conditions were less than 10 %, indicating the strong reliability of the model. The model could also make good prediction for microcontaminant degradation in the natural sunlight/monochloramine system. Furthermore, the formation of disinfection byproducts (DBPs) was evaluated at different oxidation time in simulated sunlight/monochloramine with and without post-chloramination treatment. In real waters, organic components showed more pronounced suppression on microcontaminant degradation efficiency than inorganic ions. This study provided a systematic investigation into the novel sunlight-induced monochloramine activation system for efficient microcontaminant degradation, and demonstrated the potential of the system in practical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of vacuum-ultraviolet (VUV) photolysis in water treatment has been gaining significant interest due to its efficacy in degrading refractory organic contaminants and eliminating oxyanions. In recent years, the reactive species driving pollutant decomposition in VUV-based advanced oxidation and reduction processes (VUV-AOPs and VUV-ARPs) have been identified. This review aims to provide a concise overview of VUV photolysis and its advancements in water treatment. We begin with an introduction to VUV irradiation, followed by a summary of the primary reactive species in both VUV-AOPs and VUV-ARPs. We then explore the factors influencing VUV-photolysis in water treatment, including VUV irradiation dose, catalysts or activators, dissolved gases, water matrix components (e.g., DOM and inorganic anions), and solution pH. In VUV-AOPs, the predominant reactive species are hydroxyl radicals (˙OH), hydrogen peroxide (H 2 O 2), and ozone (O 3). Conversely, in VUV-ARPs, the main reactive species are the hydrated electron (e aq −) and hydrogen atom (˙H). It is worth noting that VUV-based advanced oxidation/reduction processes (VUV-AORPs) can transit between VUV-AOPs and VUV-ARPs based on the externally added chemicals and dissolved gases in the solution. Increase of the VUV irradiation dose and the concentration of catalysts/activators enhances the degradation of contaminants, whereas DOM and inorganic anions inhibit the reaction. The pH influences the redox potential of ˙OH, the speciation of contaminants and activators, and thus the overall performance of the VUV-AOPs. Conversely, an alkaline pH is favored in VUV-ARPs because e aq − predominates at higher pH. [Display omitted] • VUV photolysis includes AOP driven by ˙OH, H 2 O 2 , and O 3 , and ARP driven by e aq − /˙H. • Irradiation dose, catalysts, gas, water matrix, and pH influences VUV efficacy. • VUV-AOP cost is lower than ultrasound, UV, electric AOP, plasma, and photo-Fenton. • Shallow penetration depth of VUV in water leads to full-scale treatment unworkable. • Optimizing the VUV reactor is a good way to overcome its limitations. [ABSTRACT FROM AUTHOR]

Establishing an economic and sustained Fenton oxidation system to enhance sludge dewaterability and carbamazepine (CBZ) removal rate is a crucial path to simultaneously achieve sludge reduction and harmless. Leveraging the principles akin to "tea making", we harnessed tea waste to continually release tea polyphenols (TP), thus effectively maintaining high level of oxidation efficiency through the sustained Fenton reaction. The results illustrated that the incorporation of tea waste yielded more favorable outcomes in terms of water content reduction and CBZ removal compared to direct TP addition within the Fe(III)/hydrogen peroxide (H 2 O 2) system. Concomitantly, this process mainly generated hydroxyl radical (•OH) via three oxidation pathways, effectively altering the properties of extracellular polymeric substances (EPS) and promoting the degradation of CBZ from the sludge mixture. The interval addition of Fe(III) and H 2 O 2 heightened extracellular oxidation efficacy, promoting the desorption and removal of CBZ. The degradation of EPS prompted the transformation of bound water to free water, while the formation of larger channels drove the discharge of water. This work achieved the concept of treating waste with waste through using tea waste to treat sludge, meanwhile, can provide ideas for subsequent sludge harmless disposal. [Display omitted] • The concept of tea-making is utilized for improving Fe(III)/H 2 O 2 oxidation ability. • The sustained release of tea polyphenols maintains efficient cycle of Fe(II)/Fe(III). • The destruction of hydrogen bond and sustained oxidation leads to CBZ removal. • Extracellular oxidation promotes the desorption of CBZ from EPS-CBZ complex. [ABSTRACT FROM AUTHOR]

• Cl 2 •− was an important parent radical of HO• in the presence of chloride. • The k Cl2•−, HCO3− and k Cl2•−, CO32− were determined by laser flash photolysis. • The accuracy and applicability of the kinetic model were greatly improved. • Chloride could compensate the inhibitory effect of bicarbonate on HO• generation. The ultraviolet/monochloramine (UV/NH 2 Cl) process is an emerging advanced oxidation process with promising prospects in water treatment. Previous studies developed kinetic models of UV/NH 2 Cl for simulating radical concentrations and pollutant degradation. However, the reaction rate constants of Cl 2 •− with bicarbonate and carbonate (k Cl2•−, HCO3− and k Cl2•−, CO32−) were overestimated in literature. Consequently, when dosing 1 mM chloride and 1 mM bicarbonate, the current models of UV/NH 2 Cl severely under-predicted the experimental concentrations of three important radicals (i.e., hydroxyl radical (HO•), chlorine radical (Cl•), and dichloride radical (Cl 2 •−)) with great deviations (> 90 %). To investigate this issue, the transformation reactions among these three radicals in UV/NH 2 Cl were systematically studied. For the first time, it was found that in addition to Cl•, Cl 2 •− was also an important parent radical of HO• in the presence of chloride, and chloride could effectively compensate the inhibitory effect of bicarbonate on HO• generation in the system. Moreover, reactions and rate constants in current models were scrutinized from corresponding literature, and the reaction rate constants of Cl 2 •− with bicarbonate and carbonate (k Cl2•−, HCO3− and k Cl2•−, CO32−) were reevaluated to be 1.47 × 105 and 3.78 × 106 M−1s−1, respectively, by laser flash photolysis. With the newly obtained rate constants, the refined model could accurately simulate concentrations of all three radicals under different chloride and bicarbonate dosages with satisfactory deviations (< 30 %). Meanwhile, the refined model performed much better in predicting pollutant degradation and radical contribution compared with the unrefined model (with the previously estimated k Cl2•−, HCO3− and k Cl2•−, CO32−). The results of this study enhanced the accuracy and applicability of the kinetic model of UV/NH 2 Cl, and deepened the understanding of radical transformation in the process. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the synergistic and antagonistic effects of Fe species and coexisting natural organic matter (NOM) on the efficacy of solar light disinfection of water are investigated. Different initial iron species (Fe2+/Fe3+) and naturalorganic matter types (Suwannee River-SRNOM, Nordic Reservoir NOM-NDNOM, SR Humic Acid-SRHA, and SR Fulvic Acid-SRFA) were selected. The bactericidal actions of Fe and NOM, alone or in conjunction, were evaluated at various initial iron dosing concentrations, NOM concentrations, irradiation intensities, and pH values. We show that when an appropriate iron (1 ppm Fe2+ or 0.25 ppm Fe3+) and NOM concentration (2 ppm SRNOM or 5 ppm NDNOM) coexisted, synergistic inactivation was observed in the pH range 5.0–8.0. A plausible explanation is that the presence of Fe+NOM significantly promoted the generation of hydroxyl radicals (•OH) and singlet oxygen (1O 2), which led to enhanced disinfection rates. These results elucidate the previously understudied effects of ubiquitous elements in natural waters and their impact on solar-mediated bacterial inactivation. [Display omitted] ● We analyzed the synergistic disinfection effects between Fe and NOM in sunlit waters. ● Various types of Fe and NOM reveal different synergistic capacity under varied pH. ● The coexistence of Fe and NOM in water enhances the Fe2+/Fe3+ cycling and PPRI production. ● 1O 2 is a key mediator of the bacterial inactivation under solar exposure. [ABSTRACT FROM AUTHOR]

[Display omitted] • The addition of In 2 O 3 significantly enhanced the visible light response of Mn(VII) • Intermediate Mn int (Mn(V) and Mn(III)) and •OH were identified as the major oxidants. • Scavenging of photogenerated e- by Mn(VII) contributed to the generation of Mn int. • The reaction of photogenerated h+ with H 2 O contributed to the generation of •OH. • The Vis/In 2 O 3 /Mn(VII) process demonstrated good reusability and robust resistance to water matrices. Activation of permanganate (Mn(VII)) by generating intermediate manganese species (Mn int , i.e., Mn(V) and Mn(III)) has been demonstrated to be an efficient way to enhance the oxidative ability of Mn(VII). In this work, it was found that the addition of indium oxide (In 2 O 3) could significantly enhance the visible light response of Mn(VII) (Vis/In 2 O 3 /Mn(VII)) by selecting flumequine (FLU) as a representative compound. The presence of In 2 O 3 enhanced the degradation of FLU by the Vis/Mn(VII) process with the pseudo-first-order rate constant increasing by around 30 folds. Intermediate Mn int (Mn(V) and Mn(III)) and hydroxyl radicals (•OH) were identified as the major oxidants in the Vis/In 2 O 3 /Mn(VII) process, and •OH outcompeted that of Mn int under alkaline conditions. The scavenge of photogenerated e- by Mn(VII) played a critical role in the generation of Mn int , while the reaction of photogenerated h+ with H 2 O contributed to the generation of •OH. The degradation efficiency of FLU showed a negative relationship with the increase of solution pH, likely due to the electrostatic repulsion between the deprotonated FLU and negatively charged In 2 O 3 surfaces. Increasing Mn(VII) or In 2 O 3 dosages enhanced the degradation of FLU by elevating the concentrations of reactive species. The presence of chloride, bicarbonate, and humic acid slightly inhibited FLU degradation by the Vis/In 2 O 3 /Mn(VII) process, due to their competitive scavenging of reactive species. Totally 14 oxidation products were identified during FLU oxidation by the Vis/In 2 O 3 /Mn(VII) process, and they were likely generated via hydroxylation, defluorination, dealkylation/decarboxylation/deamination, ring-opening, or oxidation pathways. Good stability and reusability of the In 2 O 3 catalyst were obtained. This work proposed a new activation pathway for Mn(VII) and provided a novel approach for the treatment of emerging contaminants in aqueous environments. [ABSTRACT FROM AUTHOR]

Rapid self-decomposition and low reactivity to natural organic compounds with more unsaturated functional groups in alkaline water were the two critical parameters that restricted the practical application of Ferrate (VI). Herein, we reported a novel approach to reactivate the stabilized Fe (VI) for highly efficient membrane cleaning. The Fe (VI) stabilized by bicarbonate/carbonate (HCO 3 −/CO 3 2−) buffer was reactivated by calcium ions (Ca2+) to facilitate releasement of O 2 and generate high-valent iron species with subsequent hydroxyl radicals (•OH). The process was rationally utilized for removal of the membrane foulants, humic acid (HA) coupled with Ca2+, which exhibited excellent cleaning performance with membrane flux recovered from 67% to 98%. The outstanding removal performance of membrane foulants could be mainly attributed to the high-valent iron species and •OH, with their contribution rate ratio being about 7:3. Significantly, the proposed FeO 4 2− + HCO 3 −/CO 3 2− buffer + Ca2+ strategies paved a novel way for upgrading the Fe(VI) utilization pattern compared with Fe(VI) direct oxidation, which was expected to provide an effective option for Fe(VI)-based membrane cleaning in alkaline water. [Display omitted] • A novel cleaning strategy in alkaline condition using Fe (VI) was proposed. • The stabilized Fe (VI) was reactivated by Ca2+ to facilitate releasement of O 2. • Ca2+ could activate stabilized ferrate (VI) for effective membrane cleaning. • High-valent iron species and.•OH radicals were the reactive species for cleaning process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bifunctional core–shell V O -LCO@CeO x nanoreactor was designed for H 2 O 2 activation. • Heterostructure boosted V O levels via the removal of oxygen atoms to interface. • Direct electron transfer between ≡Cu and ≡Ce achieved efficient ROS production. • The catalytic mechanism had been further confirmed through DFT calculations. Double oxygen vacancies (V O) tuned core–shell La V CuO δ @CeO x (V O -LCO@CeO x) nanoreactors with direct electron transfer (DET) structure was synthesized as an effective heterogeneous Fenton-like catalyst for the quinoline removal. The DET structure was constructed by electron-rich ≡Cu center of V O -LCO core and electron-capture center of CeO x shell for electrons supplying and consuming. This structure elevated total V O levels of catalyst through the removal of oxygen atoms in CeO 2 from attice to interface sites. Meanwhile, the ≡Ce(III) acted as reactive sites for the adsorption of hydrogen peroxide (H 2 O 2) to form surface peroxide species, and then the electron-rich ≡Cu center was further provided electrons to surface peroxide species by DET to produce hydroxyl radical. Moreover, the newly formed surface V O would also be further promote hydroxyl radical production through self-activation of H 2 O 2. This catalyst displayed excellent catalytic activity and stability. The density functional theory (DFT) results further pointed out that this structure had excellent adsorption energy, and generable electron transfer from V O -LCO to CeO x. This work provided a novel approach for the development of heterogeneous Fenton-like catalysts to degrade quinoline wastewater. [ABSTRACT FROM AUTHOR]

• The addition of PI greatly promoted the degradation of organic pollutants by In 2 O 3 /Vis-LED process. • • OH was formed through the reaction of holes with H 2 O and played a major role. • PI received electrons from the conduction band of the In 2 O 3 and eventually changed to iodate. • The species variation of PI with pH did not affect its ability to accept electrons. Periodate (PI) as an oxidant has been extensively studied for organic foulants removal in advanced oxidation processes. Here PI was introduced into In 2 O 3 /Vis-LED process to enhance the formation of ·OH for promoting the degradation of organic foulants. Results showed that the addition of PI would significantly promote the removal of sulfamethoxazole (SMX) in the In 2 O 3 /Vis-LED process (from 9.26% to 100%), and ·OH was proved to be the dominant species in the system. Besides, the process exhibited non-selectivity in the removal of different organic foulants. Comparatively, various oxidants (e.g., peroxymonosulfate, peroxydisulfate, and hydrogen peroxide) did not markedly promote the removal of SMX in the In 2 O 3 /Vis-LED process. Electrochemical analyses demonstrated that PI could effectively receive photoelectrons, thus inhibiting the recombination of photogenerated electron-hole (e −/ h +) pairs. The holes then oxidized the adsorbed H 2 O to generate ·OH, and the PI converted to iodate at the same time. Additionally, the removal rate of SMX reduced from 100% to 17.2% as Vis-LED wavelengths increased from 440 to 560 nm, because of the low energy of photons produced at longer wavelengths. Notably, the species of PI do not affect its ability to accept electrons, resulting in the degradation efficiency of SMX irrespective of pH (4.0–10.0). The coexistence of inorganic cations and anions (such as Cl−, CO 3 2−/HCO 3 −, SO 4 2−, Ca2+, and Mg2+) also had an insignificant effect on SMX degradation. Furthermore, the process also showed excellent degradation potential in real water. The proposed strategy provides a new insight for visible light-catalyzed activation of PI and guidance to explore green catalytic processes for high-efficiency removal of various organic foulants. [Display omitted] [ABSTRACT FROM AUTHOR]

• The irradiation of Cr(VI) by solar light effectively degraded various micropollutants. • OH was the major reactive species contributing to micropollutant degradation in the solar light/Cr(VI) system. • Cr(V) was determined as the important intermediate of •OH formation. • The natural solar light/Cr(VI) system showed great potential for micropollutant degradation. Hexavalent chromium (Cr(VI)) is ubiquitous in natural environments, whereas its role in the transformation of coexisting contaminants may have been overlooked. In this work, it was reported for the first time that the irradiation of Cr(VI) by solar light (solar light/Cr(VI) system) could effectively degrade various micropollutants with different structures. The removal efficiency of selected micropollutants was increased by 13.3–64.8% by the solar light/Cr(VI) system compared to that by direct solar photolysis. Meanwhile, the oxidation rates were enhanced by 2.2–21.5 folds, while they were negligible by Cr(VI) oxidation alone. Experiments by specific scavengers, probe compounds, fluorescence absorbance, and electron spin resonance analysis demonstrated that hydroxyl radical (•OH) was the major reactive species in the solar light/Cr(VI) system. Further experiments showed that the generation of •OH was closely related to the intermediate Cr(V) generated from Cr(VI) reduction, and Cr(V) could be re-oxidized back to Cr(VI). Increasing solution pH negatively affected model micropollutant (carbamazepine (CBZ)) degradation by the solar light/Cr(VI) system, mainly due to the decreased quantum yield of •OH at higher pH. Coexisting sulfate ions showed negligible effect on CBZ degradation in the solar light/Cr(VI) system, while the presence of bicarbonate, chloride, and humic acid inhibited CBZ degradation to varying degrees, owing to their diverse scavenging effects on •OH. Furthermore, moderate CBZ degradation was also achieved by natural solar light photolysis of Cr(VI). This study demonstrated the pivotal role of Cr(VI) in the transformation of micropollutants under solar irradiation, which advances the understanding of the fate of micropollutants in natural environments. [Display omitted] [ABSTRACT FROM AUTHOR]

• Fe(II)/PAA efficiently oxidized p -ASA at pH ≤ 7.0 with the optimum [Fe(II)] to [PAA] ratio of 2:1. • •OH and CH 3 C(O)O• contributed to p -ASA degradation by the Fe(II)/PAA process. • 2 organic and 4 inorganic products were detected during PAA oxidation by the Fe(II)/PAA process. • PAA rapidly oxidized As(III) to As(V) at pH ≥ 7.0 with a stoichiometry of [As(III)] to [PAA] of 1:1. • Total arsenic was effectively removed by ferric precipitates in both synthetic and real waters. The widespread occurrence of p -arsanilic acid (p -ASA) in natural environments poses big threats to the biosphere due to the generation of toxic inorganic arsenic (i.e., As(III) and As(V), especially As(III) with higher toxicity and mobility). Oxidation of p -ASA or As(III) to As(V) followed by precipitation of total arsenic using Fe-based advanced oxidation processes demonstrated to be a promising approach for the treatment of arsenic contamination. This study for the first time investigated the efficiency and inherent mechanism of p -ASA and As(III) oxidation by Fe(II)/peracetic acid (Fe(II)/PAA) and PAA processes. p -ASA was rapidly degraded by the Fe(II)/PAA process within 20 s at neutral to acidic pHs under different conditions, while it was insignificantly degraded by PAA oxidation alone. Lines of evidence suggested that hydroxyl radicals and organic radicals generated from the homolytic O O bond cleavage of PAA contributed to the degradation of p -ASA in the Fe(II)/PAA process. p -ASA was mainly oxidized to As (V), NH 4 +, and p -aminophenol by the Fe(II)/PAA process, wherein the aniline group and its para position were the most vulnerable sites. As(III) of concern was likely generated as an intermediate during p -ASA oxidation and it could be readily oxidized to As(V) by the Fe(II)/PAA process as well as PAA alone. The in-depth investigation demonstrated that PAA alone was effective in the oxidation of As(III) under varied conditions with a stoichiometric molar ratio of 1:1. Efficient removal (> 80%) of total arsenic during p -ASA oxidation by Fe(II)/PAA process or during As(III) oxidation by PAA process with additional Fe(III) in synthetic or real waters were observed, mainly due to the adsorptive interactions of amorphous ferric (oxy)hydroxide precipitates. This study systematically investigates the oxidation of p -ASA and As(III) by the Fe(II)/PAA and PAA processes, which is instructive for the future development of arsenic remediation technology. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesized nitrogen-doped rGO (N-rGO) was firstly applied to activate sulfite. • Polarized carbon atom adjacent to the doped nitrogen primarily induced activation. • The generated HO• was mainly responsible for the oxidation of As(III) to As(V). • N-rGO with more pyridine nitrogen has higher catalytic activity. As a metal-free alternative, graphene-based catalysts have attracted increasing attention for minimizing the risk of heavy metal exposure. In this study, a nitrogen–doped reduced graphene oxide (N-rGO) material was synthesized by a one–pot hydrothermal method using dicyandiamide as the precursor. N-rGO has been adopted for sulfite activation for the first time, to our knowledge. The established N–rGO/sulfite system could effectively remove As(III) in water, and the solution pH and dissolved oxygen were the most important factors affecting the removal. The results of density functional theory calculations indicated that sulfite activation was more likely to occur on C atoms adjacent to the N dopant. It was inferred that the generated hydroxyl radical (HO•) played a vital role in As(III) oxidation. In addition, the conversion of pyridinic nitrogen to pyrrolic nitrogen was responsible for the poor long–term stability of N-rGO. These results demonstrated that N-rGO was a promising catalyst for water treatment. [ABSTRACT FROM AUTHOR]

Studying the ecological risks of antibiotics and their degradation products is of great importance to water environment security and advanced oxidation processes (AOPs) development. This work studied the changes and internal influencing mechanisms of ecotoxicity and the capacity for inducing antibiotic resistance genes (ARGs) shown by the tetracycline (TC) degradation products generated in AOPs with differential free radicals. Under the action of superoxide radicals and singlet oxygen in the ozone system, and sulfate and hydroxyl radicals in the thermally activated potassium persulfate system, TC exhibited differential degradation pathways and resulted in the differential growth inhibition trends on the determined strains. Microcosm experiments combined with metagenomics were also performed to analyze the remarkable changes in the TC resistance genes tetA (60), tetT , and otr (B) induced by the degradation products and ARG hosts in the natural water environment. Microcosm experiments exhibited that the microbial community in actual water have changed significantly with the addition of TC and degradation intermediates. Furthermore, the richness of genes related to oxidative stress was investigated to discuss the effect on reactive oxygen species production and SOS response caused by TC and its intermediates. • ARGs induction testing and hosts analysis usingmicrocosm experiment combined with metagenomic methods. • Tetracycline was degraded by active oxidizing species domination. • The ecological risks of tetracycline intermediates changed with the different degradation mechanisms. [ABSTRACT FROM AUTHOR]

Ozone microbubbles have received increasing attention since they can produce hydroxyl radical (•OH) to decompose ozone-resistant pollutants. Besides, compared with conventional bubbles, microbubbles have a larger specific surface area and higher mass transfer efficiency. However, the research on the micro-interface reaction mechanism of ozone microbubbles is still relatively scarce. Herein, we systematically studied the stability of microbubbles, ozone mass transfer and atrazine (ATZ) degradation through multifactor analysis. The results revealed that bubble size was dominant in the stability of microbubbles, and gas flow rate played a major role in ozone mass transfer and degradation effects. Besides, the bubble stability accounted for the different effects of pH on ozone mass transfer in two aeration systems. Finally, kinetic models were built and employed to simulate the kinetics of ATZ degradation by •OH. The results revealed that conventional bubbles could produce •OH faster compared with microbubbles under alkaline conditions. These findings shed light on the interfacial reaction mechanisms of ozone microbubbles. [Display omitted] • The key influencing factors of each oxidation process were investigated. • With pH varying, microbubbles and conventional bubbles respond differently. • pH influenced the mass transfer of ozone through changing the stability of bubbles. • Conventional bubbles had higher.•OH generation rate compared with microbubbles at pH 9. [ABSTRACT FROM AUTHOR]

• Mitigation rates and pathways of ClO2− by solar light photolysis were revealed. • Reactive species generated in SSL/ClO2− system were identified and quantified. • •OH contributed the most to the degradation of BZF, following by Cl•, O3, and ClO•. • Impacts of water background components on BZF degradation by SSL/ClO2− were investigated. • Mitigation of ClO2− and BZF by NSL/ClO2− or by SSL/ClO2− in realistic waters were observed. Chlorite (ClO 2 −) is an undesirable toxic byproduct commonly produced in the chlorine dioxide and ultraviolet/chlorine dioxide oxidation processes. Various methods have been developed to remove ClO 2 − but require additional chemicals or energy input. In this study, an overlooked mitigation pathway of ClO 2 − by solar light photolysis with a bonus for simultaneous removal of micropollutant co-present was reported. ClO 2 − could be efficiently decomposed to chloride (Cl−) and chlorate by simulated solar light (SSL) at water-relevant pHs with Cl− yield up to 65% at neutral pH. Multiple reactive species including hydroxyl radical (•OH), ozone (O 3), chloride radical (Cl•), and chlorine oxide radical (ClO•) were generated in the SSL/ClO 2 − system with the steady-state concentrations following the order of O 3 (≈ 0.8 μΜ) > ClO• (≈ 4.4 × 10−6 μΜ)> •OH (≈ 1.1 × 10−7 μΜ)> Cl• (≈ 6.8 × 10−8 μΜ) at neutral pH under investigated condition. Bezafibrate (BZF) as well as the selected six other micropollutants was efficiently degraded by the SSL/ClO 2 − system with pseudofirst-order rate constants ranging from 0.057 to 0.21 min−1 at pH 7.0, while most of them were negligibly degraded by SSL or ClO 2 − treatment alone. Kinetic modeling of BZF degradation by SSL/ClO 2 − at pHs 6.0 – 8.0 suggested that •OH contributed the most, followed by Cl•, O 3 , and ClO•. The presence of water background components (i.e., humic acid, bicarbonate, and chloride) exhibited negative effects on BZF degradation by the SSL/ClO 2 − system, mainly due to their competitive scavenging of reactive species therein. The mitigation of ClO 2 − and BZF under photolysis by natural solar light or in realistic waters was also confirmed. This study discovered an overlooked natural mitigation pathway for ClO 2 − and micropollutants, which has significant implications for understanding their fate in natural environments. [Display omitted] [ABSTRACT FROM AUTHOR]

Natural organic matter humic acid (HA) coupled with the inorganic metal oxides FeO x + MnO x will cause severe irreversible membrane fouling. Chemical cleaning is indispensable for the removal of irreversible membrane foulants and sustainable membrane filtration, while conventional cleaning methods have limitations with low cleaning efficiency, high reagents consumption and potential membrane damage. For the first time, calcium peroxide (CaO 2), a solid alternative for liquid hydrogen peroxide (H 2 O 2), is proposed for the membrane cleaning. For membranes fouled by HA, it is noteworthy that 40 mg/32.15 cm2 CaO 2 tablet without any other catalyst can restore the terminal membrane flux dramatically from 51% to 82% in only 5 min, which is far more than 3 wt% H 2 O 2 alone (only from 51% to 59%). Moreover, Fenton-like reaction induced by in-situ membrane foulants FeO x + MnO x further enhances the membrane flux from 53% to 97%. Based on HA oxidation tests and reactive species identification in CaO 2 tablets cleaning process for the case of HA-fouled membranes and HA + FeO x + MnO x -fouled membranes, singlet oxygen ( O 2 1) in CaO 2 system dominated the strong oxidation of electron-rich compounds HA, which plays a key role in membrane flux recovery. With involvement of FeO x + MnO x , signal intensities of free radicals such as hydroxyl radicals (O H •) are enhanced greatly, which further achieves more outstanding membrane cleaning performance. These results underline that the novel CaO 2 system provides a promising candidate for more portable and cost-effective membrane cleaning method in a nonradical pathway. [Display omitted] • A novel non-radical cleaning strategy using CaO 2 was proposed. • CaO 2 system achieves outstanding flux recovery from irreversible foulants. • Singlet oxygen was identified as the dominated reactive species for cleaning process. • Membrane foulants, FeO x and MnO x , could further increase permeate flux recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • A 2-D hybrid nanocomposite (Ag/Ti 3 C 2 @BiPO 4) catalyst is synthesized. • The catalyst can activate PDS efficiently under microwave irradiation. • PPCPs can be effectively degraded in the developed Ag/Ti 3 C 2 @BiPO 4 /MW/PDS system. • SO 4 ·- and ·OH are the main contributors to PPCPs degradation. • The degradation pathways are clarified with the detected intermediate products. A hybrid nanocomposite (Ag/Ti 3 C 2 @BiPO 4) synthesized by an electrostatic self-organizing method for peroxydisulfate (PDS) activation to degrade pharmaceuticals and personal care products (PPCPs) under microwave irradiation (MW) was developed. Degradation and mineralization efficiencies of 99.4 % and 71.5 % for bisphenol A at initial concentration of 20.0 mg/L in 5.0 min operation were achieved in the proposed system. Other kinds of PPCPs including ciprofloxacin, diclofenac, sulfamethoxazole, benzophenone-3 and diethyltoluamide could also be effectively degraded. The two-dimensional (2-D) layered Ti 2 C-based material Ti 3 C 2 significantly facilitated charge transfer, the separation of electron-hole pairs and production of radicals. Additionally, Ti 3 C 2 incorporation also provided more active species being involved in MW-assisted PDS activation. Density functional theory calculation confirmed that PDS was more easily adsorbed by Ag/Ti 3 C 2 @BiPO 4 than Ag@BiPO 4 , favoring PDS activation to produce more radicals for PPCPs removal. Evidences from radical scavenger trials and electron paramagnetic resonance analysis collectively suggested that sulfate radicals and hydroxyl radicals contributed significantly to PPCPs degradation. The main degradation pathways of investigated PPCPs were also clarified with the detected intermediate products. Meanwhile, the eco-toxicity effect of intermediate products of PPCPs on fish, daphnid, and green algae calculated using ecological structure activity relationship software showed that they were much less harmful or not toxic. This work opens up a new perspective on the applications of MXene-based 2-D materials for fast and highly efficient catalytic activation of PDS to degrade PPCPs under MW irradiation. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr(VI)) was activated by ultraviolet-A light-emitting diode (UVA-LED), resulting in efficient removal of various pollutants, including dye, pharmaceuticals, and pesticides, with pseudo-first-order rate constants of 0.0610–0.159 min−1. Comparatively, UVA-LED or Cr(VI) alone barely degraded selected pollutants. Both HO• and Cr(V) were produced in the UVA-LED/Cr(VI) system based on scavenging and probing experiments, UV–visible and electron spin resonance spectra analysis. HO• was demonstrated to be the dominant reactive species via stepwise regeneration of Cr(V) to Cr(VI). The quantum yield of HO• was determined to be 7.79 × 10−4 mol Es−1 at a Cr(VI) dosage of 0.5 mM and pH of 6.0. Additionally, the degradation efficiency of sulfamethoxazole (SMX) as a model compound decreased linearly as UVA-LED wavelengths increased from 365 to 405 nm, while SMX was barely degraded at visible light irradiation wavelength ranges (449–505 nm). SMX degradation efficiency increased from 71.0 % to 97.5 % as Cr(VI) dosage increased from 0.05 to 0.7 mM. pH displayed a negative impact on SMX degradation with its removal efficiency decreasing from 99.4 % to 13.3 % as pH increased from 3.0 to 9.0. This study first reported that HO• was generated via activation of Cr(VI) by UVA-LED, which is instructive for the removal of pollutants co-existed in chromium-containing wastewater. [Display omitted] • A novel UVA-LED/Cr(VI) process was proposed firstly in this study. • UVA-LED/Cr(VI) exhibited remarkable degradation for various refractory pollutants. • HO• was identified to be reactive species in this process. • Cr(V) played a major role in HO• generation during Cr(VI) photochemical reaction. [ABSTRACT FROM AUTHOR]

The oxidation compatibility with polyamide membranes is an important feature of nanofiltration (NF) technology in practical water treatment processes. In this study, we systematically investigated the oxidation resistance of fully aromatic (NF90) and semi-aromatic (NF270) polyamide NF membranes to reactive oxidative species including SO 4 •- and HO• in terms of membrane surface properties and filtration performance. SO 4 •− and HO• exhibit different oxidative behaviors in NF membranes with different polyamide structures. The HO•-dominated oxidation significantly damaged the membrane integrity of NF90 and NF270, with notably varied surface morphology, hydrophilicity, and charge. Further analysis of the chemical property on membrane surfaces revealed that the SO 4 •−-dominated oxidation was more reactive to the N moieties (N–H or N–C) of the NF90 membrane, whereas HO• unselectively reacted with polyamides. The radicals also impact the permselectivity (water permeability and salt rejection) of the NF90 and NF270 membranes in different ways. The NF90 membrane after SO 4 •−-exposure exhibited higher water permeability and slightly decreased salt rejection, whereas the permselectivity of the NF270 membrane was more significantly affected by HO•-exposure. To further reveal the underlying oxidation mechanisms, polyamide monomers were selected to react with the peroxodisulfate solutions. The results demonstrated that a fully aromatic polyamide membrane was more resistant to oxidative radicals than a semi-aromatic polyamide membrane. This study will facilitate the development of novel antioxidant membranes and provide information for selecting appropriate membrane materials in specific water treatment processes. [Display omitted] • Oxidation resistances of polyamide NF membranes to SO 4.•- and HO• were investigated. • Radicals showed different oxidative behaviors to different polyamide NF membranes. • SO 4.•- oxidation was more reactive to polyamides and HO• oxidation was unselective. • NF90 membrane was more resistant to oxidative radicals than NF270 membrane. [ABSTRACT FROM AUTHOR]

[Display omitted] • The k obs for IBP degradation in UV/chlorine/TiO 2 was 2.7 times higher than the sum of k obs in UV/chlorine and UV/TiO 2. • The degradation of IBP and radical roles were analyzed well with model simulation. • The energy consumption was calculated and optimized. • Lower solution toxicity and less DBP formation were observed in UV/chlorine/TiO 2 than UV/chlorine and/or UV/TiO 2. • The formation mechanism of a chlorine-substituted product of IBP was revealed with DFT study. UV/chlorine is an effective process for pollutant degradation in water treatment. It was reported that the concentrations of hydroxyl radical (HO•) and chlorine radical (Cl) could rise significantly by adding TiO 2 in UV/chlorine. In this study, the degradation of ibuprofen (IBP), a frequently detected pollutant in aquatic environments, was investigated in the UV/chlorine/TiO 2 process. The pseudo-first-order kinetics rate constant for IBP degradation by UV/chlorine/TiO 2 was nearly 3-fold higher than the sum of the rate constant by UV/chlorine and UV/TiO 2. HO and Cl were the primary radicals and chlorine oxide radical (ClO) also participated in the degradation of IBP in UV/chlorine/TiO 2. The kinetic model was used to assess the effect of different influencing factors (chlorine, chloride, and bicarbonate dosage, and pH) on degradation kinetics and radical roles. Meanwhile, the probe experiment with nitrobenzene was performed to evaluate the reliability of the modeling results. The electrical energy per order (EE/O) was determined under varied chlorine and TiO 2 dosage, and the lowest EE/O of UV/chlorine/TiO 2 was obtained to be about 40% and 50% of that of UV/chlorine and UV/TiO 2 , respectively. Toxic products could be generated during IBP degradation in all three processes, while less reaction time was needed for the removal of solution toxicity by UV/chlorine/TiO 2. When achieving IBP degradation by one order of magnitude, less disinfection byproducts were generated in UV/chlorine/TiO 2 compared with UV/chlorine both with and without 24 h post-chlorination. Furthermore, a chlorine-substituted product of IBP was detected, and both HO and Cl participate in the formation of this product based on density functional theory (DFT) study. [ABSTRACT FROM AUTHOR]

In this work, a systematical investigation on the role of hydrogen sulfide (H 2 S) on the transformation of tetrachloro- p -benzoquinone (TCBQ) under ultraviolet (UV) irradiation (at 253.7 nm) in aqueous solution has been conducted through quantum chemical calculations. Under the UV irradiation, with the forward energy barrier (E a,f , 11.7 kcal mol−1) much lower than the reverse one (E a,r , 22.3 kcal mol−1), the first triplet state of TCBQ was kinetically feasible to react with bisulfide anion (HS−) via the Michael addition, and the addition of HS− could promote the release of Cl− and the formation of primary dechlorination product (HS-TriCBQ). During the UV photolysis of the primary dechlorination products (HO-TriCBQ and HS-TriCBQ) in the presence of H 2 O and H 2 S, the addition of nucleophile (OH− or HS−) to the ortho-position of the hydroxyl or thiol group might be the most efficient pathway for the dechlorination, and their respective E a,f were 9.2 kcal mol−1 (for HS−-hydroxyl), 1.1 kcal mol−1 (for OH−-thiol) and 8.9 kcal mol−1 (for HS−-thiol). Moreover, the electron transfer from HS− to the first triplet states could generate hydrosulfide radical for the dechlorination of TCBQ. The findings in the present study may provide some important theoretical foundation for the dehalogenation of TCBQ as well as other halobenzoquinones. [Display omitted] • The first triplet state of tetrachloro- p -benzoquinone and HS− could generate hydrosulfide radical. • The nucleophilic attack of HS− could facilitate the dechlorination of tetrachloro- p -benzoquinone. • The dechlorination of tetrachloro- p -benzoquinone and the decontamination of H 2 S was synergistic. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxidative filtration can utilize more oxidation capacity of PMS than homogeneous activation. • Surface PMS-complexes dominate pollutant removal. • Pollutants are selectively removed by the oxidative filtration. • The oxidative filtration also can mitigate membrane fouling. It is generally accepted that sulfate radical predominates pollutant removal when peroxomonosulfate (PMS) is activated by cobalt ion or cobalt-containing catalysts. Although sulfate radical is very reactive toward many contaminants, its nonselective reaction with various water constituents always limits its practical application. In this work, selective pollutant removal was achieved with oxidative filtration on a ceramic membrane doped with highly dispersed cobalt (Co-CM). It was observed that the oxidative filtration was insensitive to chloride, bicarbonate, and humic substances for pollutant removal, which is distinct from the oxidation relying on sulfate/hydroxyl radicals. Moreover, associated with very low Co2+ leaching (less than1 µg L−1), the oxidative filtration used more oxidation capacity of PMS than the homogeneous PMS/Co2+. Unlike heterogeneous PMS activation with Co-CM in jar tests where sulfate radical dominates pollutant removal, the predominant oxidant of the oxidative filtration was confirmed to be surface-complexed PMS. This study revealed that the hydraulic condition is an important factor to be taken into account when analyzing the mechanism of PMS activation, and this novel reaction pathway would endow the oxidative filtration with high selectivity for pollutant removal as compared with traditional slurry reactions. [ABSTRACT FROM AUTHOR]

• Increasing pH enhances the retention of Tl(I) on iron/manganese (hydr)oxides. • The properties of Tl(I) binding species affects the retention and release of Tl(I). • The hydration of surface hydroxyl groups dominates the sustained retention of Tl(I). • The binding response of alkaline species MeOTlOH− is faster than neutral MeOHTl+. • Higher adsorption energy of alkaline Tl(I) species drives the rapid retention. The reversibility of monovalent thallium (Tl) absorption on widely distributed iron/manganese secondary minerals may affect environmental Tl migration and global cycling. Nevertheless, quantitative and mechanistic studies on the interfacial retention and release reactions involving Tl(I) are limited. In this study, batch and stirred-flow experiments, unified kinetics modeling, spectral detection, and theoretical calculations were used to elucidate the retention behaviors of Tl(I) on goethite, hematite, and manganite with different solution pH values and Tl loading concentrations. Sustained Tl(I) retention (k d, MeOHTl =0.005∼0.018 min−1) was induced by hydration of the surface hydroxyl groups. Rapid Tl(I) retention (k d,MeOTlOH =1.232∼2.917 min−1) was enhanced by the abundant hydroxide ions and deprotonated hydroxyl groups, which increased the Tl(I) binding ability. Compared to the ambient Tl concentration, pH had a more substantial effect on the formation and distribution of surface Tl(I) binding species. In alkaline environments, the large adsorption energy for Tl(I) binding to surface species (E ads =-6.14 eV) induced fast Tl(I) binding response on the surfaces of iron/manganese secondary minerals. This study provides new insights into the heterogeneous surface complexation and retention behaviors of Tl(I) and contributes to an in-depth understanding of the environmental fate of Tl and the remediation of Tl contamination. [Display omitted] [ABSTRACT FROM AUTHOR]

Developing high-efficiency catalysts for peroxymonosulfate (PMS)-based advanced oxidation processes is important for eliminating pollutants in water. Herein, α-MnO 2 with major exposed {110} and {100} facets prepared via a hydrothermal method were used as catalysts to activate PMS for the degradation of Orange Ⅰ (OⅠ). α-MnO 2 -100, with more abundant surface hydroxyl groups and greater reductive ability, performed remarkably better than α-MnO 2 -110 for degrading OⅠ. OⅠ removal of 86.20% was obtained in the α-MnO 2 -100/PMS system. The apparent rate constant of OⅠ removal over α-MnO 2 -100 was 2.11 times higher than that of α-MnO 2 -110. The effects of PMS concentration, catalyst dosage, OⅠ concentration, initial pH, anions and humic acid (HA) on OⅠ degradation in the α-MnO 2 -100/PMS system were systematically investigated. Quenching experiments and electron paramagnetic resonance (EPR) demonstrated that SO 4 •−, •OH, O 2 •− and 1O 2 were the reactive oxygen species (ROS) in the α-MnO 2 -100/PMS system. Moreover, the possible degradation pathway of OⅠ in the α-MnO 2 -100/PMS system was proposed. This work provides an ideal metal oxide catalyst for sewage remediation. • α-MnO 2 with major exposed {110} and {100} facets were prepared, respectively. • α-MnO 2 -100 exhibited excellent activity to activate PMS to remove Orange Ⅰ. • Surface hydroxyl groups played an important role in the α-MnO 2 /PMS system. [ABSTRACT FROM AUTHOR]

As a special type of wastewater produced in the landfill, leachate is mainly composed of organic pollutants, inorganic salts, ammonia nitrogen and heavy metals, and featured by high pollutants concentration, complex composition and large fluctuations in water quality and volume. Biological, chemical and physical methods have been proposed to treat landfill leachate, but much attention has been paid to the advanced oxidation processes (AOPs), due to their high adaptability and organic degradation efficiency. This paper summarizes the recent findings on the AOPs based on hydroxyl radical (OH) (e.g., ozonation and catalyzed ozone oxidations, Fenton and Fenton-like oxidations) and sulfate radical (SO 4 −) (e.g., activated and catalyzed persulfate oxidations), especially the production routes of free radicals and mechanisms of action. When dealing with some special landfill leachates, it is difficult for a single advanced oxidation technology to achieve the expected results, but the synergistic combination with biological or physical methods can produce satisfactory outcomes. Therefore, this paper has summarized the application of these combined treatment technologies on landfill leachate. [Display omitted] • Landfill leachate treatment with hydroxyl and sulfate radicals-based AOPs is reviewed. • The combination of AOPs with biological and physical technologies is summarized. • The mechanisms and parameters of various AOPs and combined technologies are discussed. [ABSTRACT FROM AUTHOR]

• Fe(II)/NH 2 OH/PDS and Fe(II)/NH 2 OH/H 2 O 2 systems followed different kinetic rules. • Cl− had opposite effects on BA degradation in Fe(II)/NH 2 OH/PDS and Fe(II)/NH 2 OH/H 2 O 2 systems. • Cl− changed relative contents of ·OH, SO 4 ·− and Fe(IV) in Fe(II)/NH 2 OH/PDS system. • Cl− competitively consumed ·OH with target pollutants in Fe(II)/NH 2 OH/H 2 O 2 system. Hydroxylamine (NH 2 OH) has been verified to efficiently strengthen pollutants oxidation in Fe(II)/peroxydisulfate (PDS) and Fe(II)/H 2 O 2 systems. However, the different effects of hydroxylamine salts types were rarely recognized. Herein, the effects of two commonly used hydroxylamine salts (i.e. NH 2 OH·HCl and (NH 2 OH) 2 ·H 2 SO 4) on oxidation kinetics and reactive species composition were compared in Fe(II)/PDS and Fe(II)/H 2 O 2 systems for the first time. Pseudo first order kinetics could only describe benzoic acid (BA) oxidation well in Fe(II)/NH 2 OH/H 2 O 2 system, which was related to the different concentration changes of Fe(III) determined by [ Oxidant ] [ N H 3 O H + ] 2. Hydroxylamine salts types influenced not kinetic rules, but reaction rates of target compounds. The empirical reaction rate constant of BA in Fe(II)/NH 2 OH·HCl/PDS system was 141.5% of that in Fe(II)/(NH 2 OH) 2 ·H 2 SO 4 /PDS system under the same concentration of NH 2 OH (1.4 mM), while the apparent reaction rate constant in Fe(II)/NH 2 OH·HCl/H 2 O 2 system was 68% of that in Fe(II)/(NH 2 OH) 2 ·H 2 SO 4 /H 2 O 2 system. This opposite effect resulted from the differences in primary reactive species compositions and their interactions with Cl−. Reactive species identification indicated that Cl− would decrease the contribution of ferryl ion (Fe(IV)) and transform sulfate radical (SO 4 ·−) to hydroxyl radical (·OH) in Fe(II)/NH 2 OH/PDS system, while it competitively consumed the only reactive species ·OH in Fe(II)/NH 2 OH/H 2 O 2 system. This study highlights the importance of reductants types on strengthening Fenton oxidation and offers a reference for reasonable construction of the relevant systems. [Display omitted] [ABSTRACT FROM AUTHOR]

• Coupling EA and HA showed a synergy for the Electro-Fenton property at pH 2.0–6.9. • Coupling EA and HA made up for their respective shortcomings. • Coupling EA and HA transformed more HA into N 2. • Coupling EA and HA broadened the effective pH range up to 6.5. To improve H 2 O 2 generation and Fe3+/Fe2+ cycle simultaneously for enhancing Electro-Fenton performance, the electrode aeration (EA) and hydroxylamine sulfate (HA) were coupled. With dimethyl phthalate (DMP) as main target contaminant, combination of HA and EA greatly accelerated the degradation of DMP and exhibited a synergy in the pH of 2.0–6.9 through promoting the key reactions, including electrochemical two-electron reduction of O 2 into H 2 O 2 and redox cycles of Fe3+/Fe2+, which then improved the generation of hydroxyl radicals (·OH). The coupling EA and HA reduced the use of HA and converted most of HA into environment-friendly N 2 (60.1–62.1% of HA products), while HA/solution aeration(SA) system consumed HA rapidly and the generated N 2 only accounted for 5.8–6.7% of HA products. Furthermore, compared with HA/SA and EA Electro-Fenton systems, enhancement degree of DMP degradation in HA/EA Electro-Fenton process was higher in actual waterbody than in ultrapure water. The coupling EA and HA in the Electro-Fenton process could solve the low Fe3+/Fe2+ cycle efficiency and low H 2 O 2 production simultaneously, and improve the N 2 selectivity of HA transformation, which advanced its application in practical environmental remediation. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • NaOH showed dramatical enhancement for ACE elimination in heat/PMS system. • 1O 2 and •OH were the primary reactive oxygen species responsible for ACE degradation. • 1O 2 and •OH separately came from base-activated PMS and thermolysis of peroxide bond. • Chloride ion significantly accelerated ACE removal in NaOH-enhanced heat/PMS system. • Heat/PMS system had better performance than heat/PDS system under alkaline conditions. Owing to the high peroxide bond dissociation energy (377 kJ mol−1), peroxymonosulfate (PMS) is rather difficult to be activated by heat for degrading organic pollutants. This work is the first to add sodium hydroxide (NaOH) to enhance the elimination of acetaminophen in heat/PMS system. Heat/PMS system even possessed a better Performance than heat/peroxydisulfate (PDS) system with the addition of NaOH. Quenching experiments and electron paramagnetic resonance tests demonstrated that singlet oxygen and hydroxyl radical were the primary reactive oxygen species responsible for acetaminophen elimination in NaOH-enhanced heat/PMS system. Singlet oxygen mainly came from the alkaline activation of PMS, while hydroxyl radical was generated from the thermolysis of peroxide bond. Increasing PMS concentration and reaction temperature favored the production of reactive oxygen species and the elimination of acetaminophen. Nine degradation intermediates of acetaminophen were identified by LC/TOF/MS and the corresponding degradation pathways were proposed. Chloride ion significantly accelerated the elimination of acetaminophen, while humic acid and carbonate ion slightly retarded acetaminophen removal. NaOH-enhanced heat/PMS system was highly efficient in eliminating many organic pollutants and more prone to degrading electron-rich organics. This study developed a simple and efficient approach to strengthening the oxidation capacity of heat-activated PMS and highlighted the superiority of PMS to PDS in thermolysis under alkaline conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrafast activation of PMS was achieved with Ti 3 C 2 MXene in the presence of trace Fe3+ at the μg L-1 level. • Fe3+/PMS/MXene exhibited excellent performance even under neutral and alkaline conditions. • Ti 3 C 2 MXene had dual functions of inhibition of the hydrolysis of iron ions and reduction of Fe(III) to Fe(II). Ultrafast activation of peroxymonosulfate (PMS) by reduction of trace Fe3+ at the μg L-1 level with the ecofriendly Ti 3 C 2 MXene under neutral and alkaline conditions was achieved for the first time. Complete removal of model pollutant sulfamethoxazole (SMX) was accomplished within about 5 min and 10 min at pH 7.0 and 9.0, respectively. The degradation rate of SMX in Fe3+/PMS/MXene process was increased by 72 times compared with that in the absence of Ti 3 C 2 MXene (pH = 7). Methanol/ tert -butanol quenching experiment and electron spin resonance (ESR) measurement demonstrated that hydroxyl radical (•OH) and sulfate radical (SO 4 •–) were the primary reactive species. The strong reducibility of Ti 3 C 2 MXene played the key role in triggering the Fe(III)/Fe(II) cycle and accelerating PMS activation. The reducibility of Ti 3 C 2 MXene towards Fe3+ was measured to be 3.35:1–5.03:1 (mol:mol), far higher than that of hydroxylamine (1:1). Because the confinement effect of MXene inhibited the hydrolysis of iron ions, Fe3+/PMS/MXene process exhibited excellent performance even under neutral and alkaline conditions. This study improved the understanding of MXene in Fenton-like reaction and provided an ideal Fenton-like process with ultra-low metal consumption, high efficiency and broad pH range. [ABSTRACT FROM AUTHOR]