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[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]

[Display omitted] • Hydrogen peroxide and persulfates homogeneously activated by Cu(II) are summarized focusing on the mechanisms. • The introduction of reductants, chelators, and energy improve the catalytic efficiency of Cu(II)-initiated AOPs. • Reactive oxidant species formed are suggested to be identified by direct and multiple strategies. • Perspectives and challenges relating to homogeneously Cu(II)-initiated AOPs are discussed. Cost-effective oxidation is one of the hot topics in the remediation of environmental pollutants in recent years. Copper species have been recognized as efficient activators or catalysts in initiating some advanced oxidation processes (AOPs) to generate strong oxidants. Since many source water/wastewater contain certain amounts of Cu(II), AOPs homogeneously initiated by Cu(II) would have application potential in many cases of polluted water remediation. Although relevant research is increasing, substantial controversies exist in interpreting the mechanism of Cu(II) as an activator or a catalyst. In this review, we presented a relatively comprehensive summary on this topic, comparing the homogeneous hydrogen peroxide-based and persulfates-based AOPs initiated by Cu(II), with an emphasis on the reaction mechanisms. Approaches in literatures to improve the performance of homogeneously Cu(II)-initiated AOPs are illustrated. Furthermore, critical methodologies for the identification of intrinsic reactive species are discussed, including inhibition tests, electron paramagnetic resonance, typical organic compounds degradation, and spectroscopy methods. Finally, concluding remarks and perspectives are made to guide future research. This review is expected to provide a clear interpretation on the homogeneously Cu(II)-initiated AOPs. [ABSTRACT FROM AUTHOR]

• The classical 1O 2 -generation H 2 O 2 /OCl− system was used as comparison to some non-photochemical systems for the first time. • Dimol emission of singlet oxygen relaxation was used to investigate the 1O 2 role in some non-photochemical systems. • Methanol, acetonitrile and deuteroxide were used to explore the reaction characteristic of 1O 2 in these solvents. • The defects of quenching and EPR experiments for 1O 2 identification were discussed by experimental data. Singlet oxygen (1O 2) is considered as the dominant reactive oxygen species (ROS) responsible for micropollutants degradation in many non-photochemical systems. However, the role of 1O 2 in non-photochemical systems is overrated due to overlooking the fast quenching of 1O 2 in water and the false positive results of electron paramagnetic resonance (EPR) experiments for 1O 2 identification. Herein, we systematically compared the classical 1O 2 -generation H 2 O 2 /OCl− system and some non-photochemical systems in pollutants oxidation, electron paramagnetic resonance (EPR) experiments and dimol emission of singlet oxygen in different solvents for the first time. The results showed that almost all 1O 2 were deactivated by water and hardly consumed by micropollutants in non-photochemical systems considering the high deactivation rate constant of 1O 2 in water. Moreover, the EPR signals of TEMPO free radical detected in non-photochemical systems may not precisely represent the existence of 1O 2. These results indicated that some others ROS rather than 1O 2 , for example, dioxiranes in the ketone-catalysed decomposition of peroxomonosulfate (PMS), were responsible for the degradation of micropollutants in some non-photochemical systems, and further investigation about the real ROS are needed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transformation of phenolic pollutants by PAA was enhanced in the presence of I−, where HOI was the reactive species. • 1O 2 produced from the spontaneous decomposition of PAA was involved in the production of HOI, by oxidizing I−. • Cl− and Br− accelerated the transformation of phenolic pollutants by PAA/I− due to the formation of HOCl and HOBr. • The transformation products would increase the cytotoxicity during the PAA/I−. Peracetic acid (PAA) has been used as a disinfectant/oxidant in wastewater treatment. However, considering that the presence of iodide (I−) would induce the iodinated products in wastewater, the effect of I− on the transformation of phenolic pollutants by PAA was investigated. Herein, the presence of I− enhanced the transformation of phenolic pollutants (bisphenol S (BPS), bisphenol A (BPA), and p -hydroxybenzoic acid (p -HBA)) by PAA. Furthermore, hypoiodous acid (HOI) was reactive species in the PAA/I− system based on radical quenching experiments and electron spin resonance. In this system, PAA, together with 1O 2 that was produced in PAA oxidized I− into HOI. Increasing PAA and I− dose promoted the transformation of phenolic pollutants but the promoting effect was less significant at higher dosage. The increase in H 2 O 2 dose retarded the transformation of phenolic pollutants because of HOI being quenched by H 2 O 2. In a wide range of pH (pH 4.0–10.0), the transformation of BPS, BPA, and p -HBA was pH-dependent and most effective at pH 7.0. The presence of chloride and bromide accelerated the transformation of phenolic pollutants by PAA/I− due to the formation of HOCl and HOBr. Furthermore, HOI substitution was the primary reaction pathway in the transformation of BPS, BPA, and p -HBA by PAA/I−. Finally, the transformation products of phenolic pollutants during the PAA/I− posed higher cytotoxicity compared to the parent pollutants. Overall, our findings improved the understanding of the chemical behavior of PAA in the presence of I− and suggested that the generation of iodinated products raised concerns for water safety. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soybean biochar (SB) exhibited superior surface-area-normalized catalytic ozonation activity. • SB contained highest pyridine N and carbonyl group content which enhanced ozone activation. • SB contained strongest delocalized electron density and electron donor ability. • These biochars activated ozone to generate •OH, O 2 •− and 1O 2 for atrazine degradation. Selecting the biomass source is critical because different plants or tissues may exhibit varying textures and chemical properties. However, few researchers have compared the catalytic activity of different tissues from the same plant after carbonization. Soybean is widely cultivated worldwide and always suffers from pests and diseases. The inappropriate storage of harvested soybeans leads to mildew and its wastage. Herein, soybean biochar (SB), soybean shell biochar (SBS), and soy straw biochar (SS) catalysts were prepared using waste soybean plant tissues as precursors, which drastically improved the degradation efficiency of atrazine in catalytic ozonation. The specific reaction rate constant normalized by the surface area (k obs / S BET) of SB during catalytic ozonation indicated the catalytic performance of biochar was not affected just by S BET. The characterization results showed that the delocalized π-electrons, nitrogen-, and oxygen-containing functional groups played key roles in catalytic ozonation, and contributions of these active sites to the generation of both radical and nonradical reactive oxygen species (ROS) including hydroxyl radicals (•OH), superoxide radicals (O 2 •−), and singlet oxygen (1O 2) contributed to atrazine degradation. Compared with SBS and SS, SB contained the highest pyridine N content, the highest carbonyl group (–C = O) content, the strongest delocalized electron density, and electron donor ability, which was responsible for its superior catalytic performance. Such active sites on biochar enhanced the ozone adsorption and decomposition, accelerated the electron transfer process to produce more ROS, and achieved efficient pollutant elimination. Overall, guided by the "waste treating waste" concept, this study provided a valuable alternative in the recycling and reuse of agricultural waste soybean plants, proving that the derived biochar could be potentially used as a catalyst for advanced oxidation processes-based applications. [ABSTRACT FROM AUTHOR]

Very recently, it has been reported that bisulfite can activate permanganate to enhance the oxidation of selected organic contaminates at acid and neutral pH, where aquo and hydroxo Mn(III) formed via the fast reaction of permanganate with bisulfite is proposed to be responsible. In this work, to gain further insight into the role of bisulfite, we investigated the degradation of an emerging endocrine disruptor bisphenol S (BPS) by the permanganate/bisulfite system. We found that permanganate showed very sluggish reactivity toward BPS, while the permanganate/bisulfite system rapidly oxidized BPS at pH 4–7 with rates (∼2.8–85.2 s −1 ) that were 6–7 orders of magnitude faster than those for permanganate alone (∼10 −6 s −1 ). Both rate and extent of BPS loss in the permanganate/bisulfite system maximized at the [bisulfite]:[permanganate] ratio of 5:1–10:1, appreciably higher than the stoichiometric ratio of 2:1. Similarly, thiosulfate and hydrosulfite also showed activating effects, where the loss of BPS exhibited dependency on the [thiosulfate]:[permanganate] or [hydrosulfite]:[permanganate] ratio as well. Comparatively, arsenite showed negligible activating effect, while the combination of arsenite and bisulfite resulted in appreciable degradation of BPS by permanganate even though arsenite outcompeted bisulfite for permanganate. In addition, it was found that several model organic ligands appreciably inhibited the degradation of BPS in the permanganate/bisulfite system while Fe(III) showed negligible effect. These results were rationalized by the fact that reduced sulfur inorganics acted as complexing agents to stabilize Mn(III), and the formation of reactive Mn(III)-sulfur complexes responsible for BPS degradation was at near diffusion-controlled rate (∼10 9 M −1 s −1 ) and thus not a rate-limiting step in the permanganate/bisulfite process. [ABSTRACT FROM AUTHOR]

A novel advanced oxidation process, combined zero-valent iron and sulfite (Fe 0 /sulfite) system containing oxygen, was firstly developed to efficiently degrade organic pollutants at weak acidic and neutral conditions by selecting X-3B as a target compound. The removal of X-3B was attributed to the formed reactive radicals, such as SO 4 - , SO 5 - and HO , in the Fe 0 /sulfite system, and SO 4 - was evidenced as the principal reactive species. The quite low removal efficiency of X-3B (less than 5%) after reaction for 90 min with purging nitrogen gas suggests oxygen to be an essential factor for producing SO 4 - in the system. Optimal dosages of Fe 0 and sulfite were suggested to be 0.5 mM and 1.0 mM, respectively, in the system as both the two chemicals would scavenge the reactive radicals at overdosing. The presence of 2 mM bicarbonate significantly inhibited the removal of X-3B from 74.1% to 37.5% in the system. Halide ions inhibited the removal of X-3B following a trend that Cl − < Br − < I − . HSO 3 − , being effective in complexion of Fe(II) and transferring Fe(III) to Fe(II), is the main species during pHs 4–6, which results in the good reuse of Fe 0 and the highest removal efficiency of X-3B at weak acidic condition. Fe 0 /sulfite system was also evidenced to be effective in the treatment of actual textile effluents along with improving biodegradability, and the removal of nitrobenzene, methylparaben, bisphenol A, imipramine and amitriptyline. Overall, this study provided a cheap and easy operational advanced oxidation process in treatment of aqueous organic pollutants. [ABSTRACT FROM AUTHOR]