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Graphical abstract Unsymmetrical squaraine dyes SQ-OPA can effectively identify Cys, Hcy and GSH through two response processes. Highlights • The property of unsymmetrical squaraine dyes is variable. • Acrylate groups changed the nature of the four-member ring of squaraine. • The central of squaraines plays a role in the identification of thiols. Abstract Two unsymmetrical squaraines (SQ-OH and SQ-OPA) have been synthesized. SQ-OPA was gained by esterification of acryloyl chloride and hydroxyl group on SQ-OH. Based on the investigation of the UV–vis, fluorescent, time-dependent 1H NMR and mass spectra, SQ-OPA was demonstrated to have two response sites to biothiols: the central four-member ring and acryloyl group. SQ-OPA is the first "turn-on" fluorescent squaraine thiol probe, and can probe the biothiols (Cys, Hcy, and GSH) simultaneously by naked-eye. However, SQ-OH bearing similar squaraine molecular framework with SQ-OPA, showed good chemical stability during the addition of biothiols. Therefore, for unsymmetrical squaraines, the substituent attached in benzene ring, far away from the central four-member ring, can signficantly affect the stability of squaraine central four-member ring against the nucleophilic attack, which could provide a new strategy for designing "turn-on" fluorescent SQ probes. [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]

2-methylisoborneol (2-MIB) and geosmin are two odor-causing compounds that are difficult to remove and the cause of many consumer complaints. In this study, we assessed the degradation of 2-MIB and geosmin using a UV/persulfate process for the first time. The results showed that both 2-MIB and geosmin could be degraded effectively using this process. The process was modeled based on steady-state assumption with respect to the odor-causing compounds and either hydroxyl or sulfate radicals. The second order rate constants for 2-MIB and geosmin reacting with the sulfate radical ( SO 4 − ) were estimated to be (4.2 ± 0.6) × 10 8 M −1 s −1 and (7.6 ± 0.6) × 10 8 M −1 s −1 respectively at a pH of 7.0. The contributions of the hydroxyl radical (OH ) to 2-MIB and geosmin degradation were 3.5 times and 2.0 times higher, respectively, than the contribution from SO 4 − in Milli-Q water with 2 mM phosphate buffer at pH 7.0. The pseudo-first-order rate constants ( k o s ) of both 2-MIB and geosmin increased with increasing dosages of persulfate. Although pH did not affect the degradation of 2-MIB and geosmin directly, different scavenging effects of hydrogen phosphate and dihydrogen phosphate resulted in higher values of k o s for both 2-MIB and geosmin in acidic condition. Bicarbonate and natural organic matter (NOM) inhibited the degradation of both 2-MIB and geosmin dramatically through consuming OH and SO 4 − and were likely to be the main radical scavengers in natural waters when using UV/persulfate process to control 2-MIB and geosmin. [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]

Abstract: Magnetic porous copper ferrite (CuFe2O4) showed a notable catalytic activity to peroxymonosulfate (PMS). More than 98% of atrazine was degraded within 15 min at 1 mM PMS and 0.1 g/L CuFe2O4. In contrast, CuFe2O4 exhibited no obvious catalytic activity to peroxodisulfate or H2O2. Several factors affecting the catalytic performance of PMS/CuFe2O4 were investigated. Results showed that the catalytic degradation efficiency of atrazine increased with PMS and CuFe2O4 doses, but decreased with the increase of natural organic matters concentration. The catalytic oxidation also showed a dependence on initial pH. The presence of bicarbonate stimulated atrazine degradation by PMS/CuFe2O4 at low concentrations but inhibited the degradation at high concentrations. Furthermore, the reactive species for atrazine degradation in PMS/CuFe2O4 system were identified as hydroxyl radical (HO ) and sulfate radical through competition reactions of atrazine and nitrobenzene, instead of commonly used alcohol scavenging, which was not a reliable method in metal oxide catalyzed oxidation. Surface hydroxyl groups of CuFe2O4 were a critical part in radical generation and the copper on CuFe2O4 surface was an active site to catalyze PMS. The catalytic degradation of atrazine by PMS/CuFe2O4 was also effective under the background of actual waters. [Copyright &y& Elsevier]

Abstract: The experiments have been performed with a semi-continuous batch reactor to investigate the degradation efficiency of nitrobenzene in aqueous solution by ultrasound with the different orthogonal dual frequencies catalytic ozonation. The introduction of ultrasound can enhance the degradation efficiency of nitrobenzene compared to the results obtained from the processes of ozonation alone and ultrasound alone. The degradation of nitrobenzene is found to be zero-order in the two systems of ultrasound alone, and the reactions follow the pseudo-first-order kinetic model in the processes of ozone alone and ozone/ultrasound. The investigation confirms that the degradation of nitrobenzene follows the mechanism of hydroxyl radical (•OH) oxidation, and the enhancement function is even more pronounced in the presence of ultrasound with the greater difference between the orthogonal dual frequencies due to the obvious synergetic effect between ozone and ultrasound, which increases the utilization efficiency of ozone, and accelerates the initiation of •OH and the formation of H2O2, resulting in the rapid formation of an increasing diversity of byproducts and the advancement degree of mineralization of total organic carbon (TOC). The oxidative byproducts have been, respectively identified in the different processes selected, including o, p, m-nitrophenols, phenol, malonic acid, 4-nitrocatechol, nitrate ion, maleic acid, oxalic acid, hydroquinone, p-quinone, 1,2,3-trihydroxy-5-nitrobenzene and acetic acid. [Copyright &y& Elsevier]

Removal of phosphate in secondary effluents was investigated in presence of Fe2+/H2O2. The effect of H2O2-dose, Fe-dose and initial phosphate concentration were assessed. The results indicated that Fe2+/H2O2 could greatly increase the removal of phosphate compared with those achieved by Fe2+ alone. For initial phosphate concentration of 0.97–3.75mg P/L, phosphate removal rates of 50–60% were observed at 1:1 molar addition of Fe(II). However, a 125% excess of Fe-dose was necessary for complete phosphate removal. The experimental data demonstrated that removal of phosphate with Fe2+/H2O2 was higher than that observed with ferric coagulation alone. This fact suggested that in situ formed Fe(III) having much affinity for ligand phosphate. Chemical co-precipitation was considered as the dominant mechanism about phosphate removal in presence of Fe2+/H2O2. The electron paramagnetic resonance (EPR) spectra tests in secondary effluents showed that Fe2+/H2O2 could produce an increasing hydroxyl radical concentration with a decrease in both H2O2 dosage and phosphate concentration. Fe2+/H2O2 had the potential to be utilized for removal of phosphate due to the lower cost and the higher phosphate removal capability. [Copyright &y& Elsevier]

Abstract: The degradation efficiencies of nitrobenzene in aqueous solution were investigated by semi-continuous experiments in the processes of ozone alone, ozone/ceramic honeycomb (CH) and ozone/modified ceramic honeycomb (MCH). MCH with 1.0% Mn and 0.5% Cu had more pronounced catalytic ability than CH to accelerate the degradation of nitrobenzene, to increase the utilization efficiency of ozone, to improve the concentrations of hydrogen peroxide (H2O2) formation and hydroxyl radical (ation, and to enhance the removal efficiency of TOC. The modification process of CH with the metals enhanced the density of surface hydroxyl groups, which determines the initiation of zone decomposition and the generation of intermediate species on heterogeneous catalytic surface, yielding the acceleration of the degradation of nitrobenzene in aqueous solution. Possible reaction mechanism of ozone with heterogeneous catalytic surface in aqueous solution was proposed, and the formation mechanism of H2O2 and so discussed according to the combined reactions in heterogeneous and homogeneous catalytic systems. [Copyright &y& Elsevier]

[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]

To better predict the elimination of highly ozone-refractory organic micro-pollutants from wastewater in ozonation and peroxone (O 3 /H 2 O 2 ) processes, it is important to understand the OH formation therein. Nevertheless, the contribution of the propagation reactions (in brief, OH + DOM (Dissolved Organic Matter) + O 2 → O 2 − , O 3 + O 2 − → O 3 − → OH ) to the OH yields ( Ф ) in these two processes has not received great attention so far. In this study, >25% of O 3 was estimated to be consumed via the propagation reactions in ozonation of wastewater effluents. The competition method (taking the OH exposure and scavenging capacity of water matrix into account) was recommended to determine the Ф values, and thus the relatively higher values (i.e., 33–58% vs. 6–24%) in ozonation were obtained as compared with the “ tert- Butanol ( t BuOH) assay” (with excess t BuOH to scavenge OH producing stoichiometric formaldehyde), where the contribution of the propagation reactions was otherwise neglected when excess t BuOH completely scavenged OH . In peroxone of wastewater effluents, the rate constant of O 3 consumption increased significantly with the increase of H 2 O 2 concentration ([H 2 O 2 ]:[O 3 ] = 0.1–0.35). However, compared to ozonation alone, the improvement of the Ф values was negligible over a wide range of [H 2 O 2 ]:[O 3 ] = 0.1–2.0. This discrepancy was mainly ascribed to the fact that substantial O 3 consumption via the propagation reactions resulted in comparable Ф values in peroxone vs. ozonation processes. [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]

Organic degradation by zero-valent metal (ZVM)-activated peroxymonosulfate (PMS) systems has drawn great attention in water treatment. Among various types of ZVM, zero-valent copper (ZVC) showed greatest activating capacity. However, the disadvantages of the released Cu2+ limit the practical utilization of ZVC. In this study, the activation capacity of four normal-sized copper catalysts, namely, copper sheet, graphene-copper sheet, copper foam, and graphene-copper foam, for PMS was investigated using Naproxen (NPX) as the probe compound. Results showed that the degradation efficiency of NPX increased by 10%, while the release of Cu2+ decreased by 30% by coating the copper with graphene. Stability tests showed that all of the four catalysts exhibited considerable stability in PMS activation. Furthermore, we found for the first time that the hydroxyl radical was the dominant species in the degradation of NPX rather than the sulfate radical, which was proved by ESR and radical scavenging experiments. Finally, six intermediates were identified by HPLC-MS/MS, and the degradation pathways were proposed. This study confirmed the feasibility of graphene coating on metals to achieve the enhancement of PMS activation. • The activation capacity of four types of normal-sized zero-valent copper catalyst on PMS was investigated. • The release of copper ions could be inhibited by graphene coating, while the degradation efficiencies of NPX increased. • PMS acted as an electron acceptor in the four copper-catalyzed PMS systems. • Hydroxyl radical was the dominant species in the degradation of NPX, and water acted as the radical precursor. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • UV/PDS is proposed to be unsuitable for treatment of bromophenols compared to UV/H 2 O 2. • Brominated polymeric products can be formed in UV-based oxidation process. • BrO 3 − evolution in the degradation of 2,4-DBP by UV/PDS exhibited biphasic kinetics. Abstract The sustained massive use of bromophenols in industrial products leads to their especially pernicious in aquatic environments. This study explored the oxidation kinetics of 2,4-bromophenol (2,4-DBP) and formation potential of bromate (BrO 3 −) and brominated polymeric products of concern during water treatment by UV/persulfate (PDS) and UV/hydrogen peroxide (H 2 O 2). 2,4-DBP exhibited appreciable reactivity toward sulfate radical (SO 4 −) and hydroxyl radical (HO). The second-order rate constants of SO 4 − and/or HO with 2,4-DBP at pH 9 were higher than those at pH 5 and 7. It is mainly due to the deprotonation of the hydroxyl group in 2,4-DBP when pH > pKa (pKa = 7.79). The chloride ions (Cl−) significantly inhibited 2,4-DBP degradation in UV/PDS process, which showed little inhibition in the UV/H 2 O 2 process. Carbonate/bicarbonate (CO 3 2−/HCO 3 −) and natural organic matters (NOM) significantly retarded 2,4-DBP degradation in both processes. BrO 3 − formation in UV/PDS process in the presence of 2,4-DBP (as organic carbon model compound) exhibited biphasic kinetics, i.e., BrO 3 − was undetectable in the lag phase and rapid generated in the secondary rapid phase. However, BrO 3 − was not detected throughout UV/H 2 O 2 process. According to the analysis by electrospray ionization-triple quadruple mass spectrometry, tentative oxidation pathway was proposed. The results showed that brominated polymeric products in the reaction of 2,4-DBP with SO 4 − and/or HO were readily produced by electrophilic addition and coupling reactions. Given the enhanced toxicological effects of these BrO 3 − and brominated polymeric products compared with the bromophenols precursors, it is important to better understand their reactivities and fates when UV/PDS or UV/H 2 O 2 is applied for the oxidative treatment of bromophenols-containing waters. [ABSTRACT FROM AUTHOR]

Abstract The frequent detection of propranolol, a widely used β-blocker, in wastewater effluents and surface waters has raised serious concern, due to its adverse effects on organisms. UV/hydrogen peroxide (UV/H 2 O 2) and UV/persulfate (UV/PDS) processes are efficient in eliminating propranolol in various waters, but the formation of oxidation products in these processes, as well as the assessment of their toxicity, has not been systematically addressed. In this study, we identified and compared transformation products of propranolol produced by hydroxyl radical (•OH) and sulfate radical (SO 4 •-). The electrostatic attraction enhances the reaction between SO 4 •- and the protonated form of propranolol, while •OH shows non-selectivity toward both protonated and neutral propranolol species. The hydroxylation of propranolol by •OH occurs at either amine moiety or naphthalene group while SO 4 •- favors the oxidation of the electron-rich naphthalene group. Further oxidation by •OH and SO 4 •- results in ring-opening products. Bicarbonate and chloride exert no effect on propranolol degradation. The generation of CO 3 •- and Cl-containing radicals is favorable to oxidizing naphthalene group. The acute toxicity assay of Vibrio fischeri suggests that SO 4 •- generates more toxic products than •OH, while CO 3 •- and Cl-containing radicals produce similar toxicity as SO 4 •-. High concentrations of bicarbonate in UV/H 2 O 2 increase the toxicity of treated solution. Graphical abstract Image 1 Highlights • Propranolol degradation is comparatively studied in UV/H 2 O 2 and UV/PDS. • CO 3.•- and Cl-containing radicals react with propranolol •.•OH induces hydroxylation of propranolol at either amine or naphthalene group • SO 4.•-, CO 3 •- and Cl-containing radicals attack the naphthalene group • SO 4.•-, CO 3 •- and Cl-containing radicals generate more toxic products than •OH [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The combination of O 3 with PMS had a strong enhancement on bromate formation. • The bromate formation process was clarified in O 3 /PMS process. • Bromate formation was the combined effect of molecular ozone, OH and SO 4 − in O 3 /PMS process. • The bromate formation was significantly inhibited in the actual water in O 3 /PMS process. Abstract Previously, we proposed a novel advanced oxidation process combining ozone (O 3) with peroxymonosulfate (PMS), which simultaneously produces sulfate radical (SO 4 −) and hydroxyl radical (OH) and significantly enhances the removal of organic matter. However, bromate formation is poorly understood during the oxidative treatment of bromide-containing water by O 3 /PMS process. In this study, factors influencing bromate formation were explored during the O 3 /PMS process, including the influences of solution pH, PMS dosage, and bromide concentration in distilled water and in actual water samples. Furthermore, the bromate formation mechanism was also clarified by monitoring the intermediate hypobromous acid (HOBr/OBr−), calculating the change of bromide species at different pH levels, and was further confirmed by adding radical scavengers. Generally, the O 3 /PMS process significantly promotes bromate formation compared with ozone treatment alone. During the O 3 /PMS process, increasing the PMS dosage and bromide concentrations promoted bromate formation, which was also significantly improved by raising the pH from 4.0 to 10.0. Bromate formation was a result of the combined effect of molecular ozone, OH, and SO 4 −, and the HOBr/OBr− was the essential intermediate species. Bromate formation was inhibited in the actual water sample due to the competitive effect of natural organic matter, bicarbonate, and reaction of HOBr/OBr− with ammonia. Therefore, the bromate formation should be evaluated as applying the O 3 /PMS process for organic matters abatement in bromide-containing actual water. [ABSTRACT FROM AUTHOR]

Abstract While fluoroquinolone (FQ) antibiotics are susceptible to degradation by sulfate and/or hydroxyl radicals formed in peroxymonosulfate (PMS) based advanced oxidation processes, here we report that unactivated PMS itself exhibits a specific high reactivity toward FQs for the first time. Reaction kinetics of PMS with two model FQs, ciprofloxacin (CF) and enrofloxacin (EF), showed a strong pH dependency with apparent second-order rate constants of 0.10–13.05 M−1s−1 for CF and 0.51–33.17 M−1s−1 for EF at pH 5–10. This pH dependency was well described by species-specific parallel reactions. On the basis of reaction kinetics and structure–activity assessment, the tertiary and secondary aliphatic N4 amines on the FQs' piperazine ring were proposed to be the main reaction sites. High performance liquid chromatography/electrospray ionization tandem mass analysis showed the formation of hydroxylated, N-oxide, and dealkylated products. Bacterial growth inhibition bioassays using Escherichia coli showed that oxidation products of FQs by PMS retained negligible antibacterial potency in comparison to parent FQs. Kinetic modeling using the rate constants estimated from pure water well predicted the oxidation kinetics of low levels of CF and EF by PMS in surface water. The degradation efficiency of FQs by PMS in surface water was slightly lower than that by ozone, comparable to that by ferrate, and much higher than that by permanganate. These results suggest that PMS is a promising oxidant for the treatment of FQs in water. Graphical abstract Image 1 Highlights • Direct oxidation of FQs by PMS without activation showed strong pH dependency. • Aliphatic N4 amines on the FQs' piperazine ring were the main reaction sites. • Transformation of FQs yielded hydroxylated, N-oxide, and dealkylated products. • Oxidation products had a much lower antibacterial activity than parent FQs. • FQs were efficiently degraded by PMS in natural water. [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]

Vacuum-Ultraviolet (VUV), an efficient and green method to produce hydroxyl radical (•OH), is effective in degrading numerous organic contaminants in aqueous solution. Here, we proposed an effective and simple kinetic model to describe the degradation of organic pollutants in VUV system, by taking the •OH scavenging effects of formed organic intermediates as co-existing organic matter in whole. Using benzoic acid (BA) as a •OH probe, •OH was regarded vital for pollutant degradation in VUV system, and the thus developed model successfully predicted its degradation kinetics under different conditions. Effects of typical influencing factors such as BA concentrations and UV intensity were investigated quantitatively by the model. Temperature was found to be an important influencing factor in the VUV system, and the quantum yield of •OH showed a positive linear dependence on temperature. Impacts of humic acid (HA), alkalinity, chloride, and water matrices (realistic waters) on the oxidation efficiency were also examined. BA degradation was significantly inhibited by HA due to its scavenging of •OH, but was influenced much less by the alkalinity and chloride; high oxidation efficiency was still obtained in the realistic water. The degradation kinetics of three other typical micropollutants including bisphenol A (BPA), nitrobenzene (NB) and dimethyl phthalate (DMP), and the mixture of co-existing BA, BPA and DMP were further studied, and the developed model predicted the experimental data well, especially in realistic water. It is expected that this study will provide an effective approach to predict the degradation of organic micropollutants by the promising VUV system, and broaden the application of VUV system in water treatment. [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]

This study proposed deethylatrazine (DEA) as the OH probe compound during ozonation and compared with the widely used p -chlorobenzoic acid ( p CBA) for the first time. Results showed the ozone decay was not affected by DEA, but largely accelerated by p CBA as compared to the control. The DEA degradation was exclusively attributed to OH formation from ozonation of the tested waters, while p CBA was partially degraded by OH formation from the p CBA-derived propagation reactions. In synthetic waters with different OH scavenging capacities, the ozone decay rates with DEA were almost consistent with the control. The ozone decay rates with p CBA remained consistent with the control only in the synthetic waters with high OH scavenging capacities. For the synthetic waters with low OH scavenging capacities, p CBA led to higher ozone decay rates and OH exposures, and thus gave overestimated R ct values. The two OH probe compounds were also investigated in four authentic waters with different OH scavenging capacities. DEA exhibited no detectable effect on the ozone decay in all four authentic waters as compared to the control. The enhancing effects of p CBA on the ozone decay and OH formation were observed in the tap and reservoir water, which led to an overestimation of R ct as compared to the presence of DEA. In the ground water and wastewater, similar values were observed in ozone decay rates and R ct for the presence of p CBA and DEA. Thus, the use of p CBA as the OH probe compound should be carefully examined or avoided to prevent its interrupts in determining the R ct during ozonation of waters with different OH scavenging capacities. DEA is a more appropriate OH probe compound during ozonation. [ABSTRACT FROM AUTHOR]

Magnetic porous Bi-doping MnFe 2 O 4 (Mn 1− x Bi x Fe 2 O 4 , x = 0, 0.005, 0.01, 0.02, 0.05) were synthesized by a sol–gel method and characterized via multiple techniques. The influence of Bi-doping on catalytic ozonation of catalysts for di-n-butyl phthalate (DBP) decomposition and ozone utilization were investigated in aqueous solutions. Varying Bi-doping amount had little effect on the crystal structure, morphology and magnetism of MnFe 2 O 4 . The introduction of Bi into MnFe 2 O 4 enhanced the catalytic DBP degradation. Hydroxyl radicals played a critical role in the Mn 1− x Bi x Fe 2 O 4 /O 3 heterogeneous systems. OH generation was promoted by the surface hydroxyl groups which were regarded as main active sites of catalyst. The extent of Bi-doping had an effect on crystallite size ( D XRD ) and resulted in increasing surface hydroxyl site concentrations (SHSC) of catalysts. A good linear correlation between the doping amount and SHSC was observed. The initial reaction rate and DBP removal rate mainly depended on the surface hydroxyl groups in catalytic ozonation. The numbers of SHSC and average ozone utilization rate were correlated with initial reaction rates and DBP removal rates, respectively. Bi-doping not only increased the binding sites but also enhanced the tendency of ozone to decompose into OH. [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]

Enhanced ozonation degradation of para -chlorobenzoic acid ( p CBA) with the addition of peroxymonosulfate (PMS) was investigated in aqueous solution. The results demonstrated that the addition of PMS could accelerate the decomposition of O 3 by 50 times compared to that of O 3 alone, and the effect was comparable to that of hydrogen peroxide. The degradation of a typical organic contaminant p CBA, was significantly enhanced by the addition of O 3 /PMS. The mechanism behind the synergistic effect was preliminarily explored by the addition of hydroxyl and sulfate radical ( SO 4 - ) scavengers. The degradation of p CBA by O 3 /PMS could not be completely inhibited by tert -butanol, whereas it was inhibited by the addition of methanol, indicating that the effect of O 3 /PMS was primarily due to the production of a greater amount of SO 4 - . The addition of O 3 /PMS had a selective effect on various contaminants. The enhanced degradation of p CBA by O 3 /PMS was also observed in actual water samples, and provided some impetus for practical applications of the developed 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]

Abstract: A molecular imprinted particle for Bisphenol A (BPA-MIP) was successfully used for selective recognition of BPA in the water. The contaminants such as 3, 3′, 5, 5′-Tetrabromobisphenol A (TBBPA), phenol and phenol red (PSP) were selected as the latent interferon to investigate the selectivity. The binding efficiencies of BPA-MIP for different phenols were explored at various initial concentrations in the single and mixed water. Various selective parameters such as K d , K and K' of BPA-MIP for BPA were calculated. The influences of humic acid (HA) and common ions on the BPA binding were investigated. A physical model was proposed to illustrate the selective binding performance. The results showed that BPA-MIP possessed strong selectivity for BPA in competitive water, while the other similar phenols had the influence for BPA binding at the order of TBBPA > phenol > PSP. The HA and common ions indicated little effect on the BPA binding process onto BPA-MIP. It was found that the molecular geometry and the hydrogen bonding interactions between the hydroxyl and carboxyl played an important role in recognizing the target molecular in the binding process. [Copyright &y& Elsevier]

[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]

Abstract: The efficiency and mechanism of catalytic ozonation of 2,4,6-trichloroanisole (TCA) by metal oxide modified bauxite were studied. TCA was effectively degraded by catalytic ozonation in the presence of iron- or manganese-modified bauxite (IMB or MMB). The effect of water pH on catalytic ozonation indicated that surface property was the key factor that influenced the activity of catalyst. Analysis results of the isoelectric point (IEP) and zeta potential for catalyst further confirmed that a lower zeta potential for modified bauxite enhanced catalytic activity. Results of both catalytic ozone decomposition and radical scavengers experiments indicated that catalytic ozonation by IMB or MMB followed a hydroxyl radical (ion pathway. The main reaction pathway was proposed that adsorption of both ozone and TCA in the micropores and subsequent interaction (direct and indirect oxidation) between them that was confirmed by the analysis of the surface pore volume and surface hydroxyl groups, being followed by the diffusion of ozone and TCA on the mesoporous surface, in which surface hydroxyl groups covering mesoporous surface initialed ozone decomposition to generate ted in TCA degradation. [Copyright &y& Elsevier]