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Thiosulfate (S 2 O 3 ) is frequently used as an ozone (O 2- ) is frequently used as an ozone (O 3 ) quenching agent when investigating the ozonation of organic contaminants and the kinetics thereof. In this study, however, O 3 is activated by S 2 O 3 2- , resulting in a superfast degradation of O 3 -refractory contaminants. Therefore, the focus of this study is the exploration into the enhancing role of S 2 O 3 2- in the degradation of refractory organic contaminants by O 3 , which has been overlooked thus far. Results obtained from scavenging experiments and electron paramagnetic resonance (EPR) spectra verify that • OH generated from the reaction of S 2 O 3 2- with O 3 is mainly responsible for the superfast degradation of O 3 -refractory contaminants. The • OH yield from the O 3 /S 2 O 3 process is proposed with the implementation of density functional theory (DFT). Initially, ozone reacts with a sulfur of S 2- process is determined to be 0.216. A plausible mechanism for the generation of • OH from the O 3 /S 2 O 3 2- process is proposed with the implementation of density functional theory (DFT). Initially, ozone reacts with a sulfur of S 2 O 3 2- to form OOOSSO 3 2- . The adduct then rearranges to OO(O)SSO 3 2- or HOO(O)SSO 3 2- in the presence of H + , which cleaves to give a sulfoxide radical cation and O 2 •- /HO 2 • . O 2 •- /HO 2 • is rapidly transformed into • OH by O 3 through a series of steps. Degradation efficiency of O 3 -refractory contaminants of this process highly depends on the molar ratio of S 2 O 3 2- and O 3 ([S 2 O 3 2- ]:[O 3 ]). The optimal [S 2 O 3 2- ]:[O 3 ] is pH dependent in synthetic water (e.g. 0.3 at pH 7). The presence of bicarbonate inhibits the degradation of refractory contaminants by the O 3 /S 2 O 3 2- process. Humic acid exhibits a slight enhancing effect at low concentrations (0.1-0.2 mg-C/L), and an inhibiting effect at higher concentrations (≥0.4 mg-C/L). In addition, the efficacy of the O 3 /S 2 O 3 2- process in real water matrices is also confirmed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study systematically investigated the performance of ozonation on tetrabromobisphenol A (TBBPA) degradation under different ozone dosages (5.21-83.33 μmoL/L), initial solution pH (3.0-11.0) and temperatures (10-50 °C). At the same time, the generations of inorganic products (bromide ion and bromate) under different experimental conditions were evaluated and the organic products were also identified. Then, the possible mechanism was proposed and verified by the quantum chemical calculation. In addition, variations and controlling of the toxicity were also analyzed, including acute toxicity, chronic toxicity and genotoxicity. Ozonation was proved to be an efficient and promising technology for removing TBBPA from water. TBBPA of 1.84 μmoL/L could be completely degraded within 5 min under the ozone dosage of 41.67 μmoL/L in wide ranges of pH (3.0-11.0) and temperature (10-40 °C). During the degradation of TBBPA, over 65% of the average bromine ion was detected and nine products were identified. The proposed degradation pathways verified that TBBPA might undergo addition and stepwise oxidative debromination, the hydrogen extraction, and the deprotonation. The results of toxicity testing showed that ozonation could effectively control the acute and chronic toxicity of the water samples, although the toxicity increased in the initial reaction stage due to the accumulation of more toxic intermediates., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Treatment of Ni-EDTA in industrial nickel plating effluents was investigated by integrated application of Fenton and ozone-based oxidation processes. Determination of integrated sequence found that Fenton oxidation presented higher apparent kinetic rate constant of Ni-EDTA oxidation and capacity for contamination load than ozone-based oxidation process, the latter, however, was favorable to guarantee the further mineralization of organic substances, especially at a low concentration. Serial-connection mode of two oxidation processes was appraised, Fenton effluent after treated by hydroxide precipitation and filtration negatively affected the overall performance of the sequential system, as evidenced by the removal efficiencies of Ni 2+ and TOC dropping from 99.8% to 98.7%, and from 74.8% to 66.6%, respectively. As a comparison, O 3 /Fe 2+ oxidation process was proved to be more effective than other processes (e.g. O 3 -Fe 2+ , O 3 /H 2 O 2 /Fe 2+ , O 3 /H 2 O 2 -Fe 2+ ), and the final effluent Ni 2+ concentration could satisfied the discharge standard (<0.1 mg L -1 , China) under the optimal conditions (H 2 O 2 dosage of 1.0 mL L -1 , Fe 2+ : H 2 O 2 mole ratio of 1.46, and reaction time of 10 min for Fenton reaction, initial influent pH of 3.0, O 3 dosage of 252 mg L -1 , Fe 2+ of 150 mg L -1 , and reaction time of 30 min for O 3 /Fe 2+ oxidation). Furthermore, pilot-scale test was carried out to study the practical treatability towards the real nickel plating effluent, revealing the effective removal of some other co-existence contaminations. And Fenton reaction has contributed most, with the percentage ranging from 72.41% to 93.76%. The economic cost advantage made it a promising alternative to the continuous Fenton oxidation., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Elimination of hypophosphite (HP) was studied as an example of nickel plating effluents treatment by O 3 /H 2 O 2 and sequential Fe(II) catalytic oxidation process. Performance assessment performed with artificial HP solution by varying initial pH and employing various oxidation processes clearly showed that the O 3 /H 2 O 2 ─Fe(II) two-step oxidation process possessed the highest removal efficiency when operating under the same conditions. The effects of O 3 dosing, H 2 O 2 concentration, Fe(II) addition and Fe(II) feeding time on the removal efficiency of HP were further evaluated in terms of apparent kinetic rate constant. Under improved conditions (initial HP concentration of 50 mg L −1 , 75 mg L −1 O 3 , 1 mL L −1 H 2 O 2 , 150 mg L −1 Fe(II) and pH 7.0), standard discharge (<0.5 mg L −1 in China) could be achieved, and the Fe(II) feeding time was found to be the limiting factor for the evolution of apparent kinetic rate constant in the second stage. Characterization studies showed that neutralization process after oxidation treatment favored the improvement of phosphorus removal due to the formation of more metal hydroxides. Moreover, as a comparison with lab-scale Fenton approach, the O 3 /H 2 O 2 ─Fe(II) oxidation process had more competitive advantages with respect to applicable pH range, removal efficiency, sludge production as well as economic costs. [ABSTRACT FROM AUTHOR]

BACKGROUD Nitrite is ubiquitous in natural water and wastewater. It is generally accepted that nitrite is an ozone consumer and has a negative influence on contaminants degradation during ozonation. Recently, nitrite was found to react with ozone to produce · OH. However, the potential positive effect of nitrite on the degradation of ozone refractory compounds has never been recognized previously during ozonation. Herein, the influence of nitrite on the degradation of atrazine by ozonation is evaluated. RESULTS The presence of nitrite was found to enhance atrazine degradation during ozonation. The enhancing effect of nitrite was attributed to · OH formation with a yield of 8.4% in the reaction of ozone with nitrite, which was demonstrated in scavenging experiments with tert-butyl alcohol. The maximum atrazine degradation was observed at the nitrite dose of 10 µmol L−1, when the ozone dose was 20 µmol L−1. The enhancing effect of nitrite on atrazine degradation by ozonation was more pronounced at lower pHs. The enhancing effect of nitrite on atrazine degradation by ozonation was still observed in surface water, especially at acidic pH. Six transformation products of atrazine were identified in the ozone/nitrite system, and the degradation mechanism is discussed. CONCLUSIONS This study is the first to demonstrate that nitrite not only acts as an ozone consumer, but may also have a positive effect on the degradation of ozone refractory contaminants by activating ozone to produce · OH. It provides a more comprehensive understanding to the role of nitrite in ozonation. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

This work investigated the fate of bromate formation during ozonation in the presence of hydroxylamine (HA). Results indicated that pH depression, as a commonly feasible control strategy for bromate formation during ozonation, unexpectedly enhanced the bromate formation during ozonation in the presence of HA. A dramatically high level of bromate was observed at acidic pH in the ozone/HA process. The scavenging experiments demonstrated the essential role of OH produced in the reaction of ozone with HA in bromate formation. In the process, OH mainly oxidizes bromide to Br , which is further oxidized by ozone and eventually converts to bromate. Further investigations suggested that the unexpected enhancement on bromate formation by pH depression can be mainly ascribed to the pH-dependent ozone decay, OH exposures and formation rate of Br . As pH decreased from 7 to 5, the reduced OH scavenging capacity of HA led to higher OH exposures, which contributed to the enhancement of bromate formation. As pH decreased from 5 to 3, the enhanced formation rate of Br largely augmented the formation of bromate. In addition, the ozone decay slowed down by pH depression provided more available ozone for the oxidation of the formed Br to bromate. The enhanced effect of pH depression on bromate formation was still observed in the real water samples in the ozone/HA process. Accordingly, pH depression might be avoided to control the bromate formation during ozonation in the presence of HA. [ABSTRACT FROM AUTHOR]

Highlights: [•] Minimizing of bromate formation by ferrate was studied for the first time. [•] The mechanism is the combined effects of intermediates on and HBrO/BrO−. [•] Bromate can be effectively inhibited with the increase of ferrate dose. [•] Ferrate inhibited bromate under the drinking water standard in pH range 3.0–11.0. [•] Temperature had a positive relationship with the inhibition of bromate formation. [Copyright &y& Elsevier]