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Halonitromethanes (HNMs) is a typical class of nitrogenous disinfection byproducts with high toxicity. The effect of Br− on the formation and transformation of HNMs from dimethylamine (DMA) during the ultraviolet (UV)/chlorine disinfection has been investigated in current study. Results reveal that only chloronitromethane, dichloronitromethane and trichloronitromethane (TCNM) could be found during the UV/chlorine disinfection. Whereas in the presence of Br−, nine species of HNMs could be observed simultaneously. When Br− concentration increased from 0 to 15.0 mg L−1, the predominant species of HNMs were gradually changed from TCNM to dibromonitromethane and tribromonitromethane, which contributed to 23.37% and 31.07% of total HNMs concentration at 15 mg L−1 Br−, respectively. The presence of Br− not only shifted the chlorinated-HNMs (Cl-HNMs) towards brominated-HNMs (Br-HNMs) but also affected the dominant species and total concentration of HNMs. When Br− concentration was 4.0 mg L−1, the formation of HNMs decreased with the increase of pH from 6.0 to 8.0 and increased with the increase of free chlorine and DMA. When free chlorine concentration rose from 0.25 to 1.1 mmol L−1, Br-HNMs were shifted to Br(Cl)-HNMs and then to Cl-HNMs. According to the findings, possible formation and transformation pathways of HNMs from DMA were proposed in the presence of Br− during the UV/chlorine disinfection. Finally, it was proved that the effect of Br− on the trend of HNMs in real water was similar to that in deionized water, but higher HNMs concentrations and delayed peak time were observed in real water. This study can provide the scientific evidence and fundamental data for the applications of UV/chlorine disinfection in the treatment of water containing Br−. [Display omitted] • Nine species of HNMs were found in the presence of Br− under UV/chlorine. • The increase of Br− shifted the Cl-HNMs towards Br-HNMs under UV/chlorine. • Free chlorine, pH and DMA seriously affected the formation and species of HNMs. • Pathways of HNMs from DMA were proposed in the presence of Br− under UV/chlorine. [ABSTRACT FROM AUTHOR]

Peroxymonosulfate (PMS) activation induced by tricobalt tetroxide spinel (Co 3 O 4 ) has been confirmed as a typical Haber-Weiss reaction, while free radicals were once considered as the dominated reactive species in the previous studies. However, the catalytic mechanism of the spongy Co 3 O 4 driven PMS activation was surprisingly found as a radical/nonradical mixed process rather than a pure radical process in the present work. The important role of sulfate radical (SO 4 - ) was confirmed through the quenching experiments. Despite the inhibition of furfuryl alcohol (FFA) and 1,4-benzoquinone (BQ) on degradation was generally accepted as the evidence to support the existence of 1 O 2 and O 2 - , additional experiments using methyl phenyl sulfoxide (PMSO) as the indicator indeed verified high-valent-cobalt-oxo rather than 1 O 2 and O 2 - dominated the very early reaction stage. Notably, instead of homogeneous Co 3+ , heterogeneous Co(IV) = O on catalyst surface was believed to be responsible for the oxidation of organics. Spongy Co 3 O 4 not only possessed stronger catalytic ability than commercial Co 3 O 4 (k [spongy Co3O4]  = 0.74 min -1 , k [Co3O4]  = 0.08 min -1 ), but also owned preferable stability. The performance of catalytic system was barely affected by the solution pH under the near neutral condition. Besides, little suppression of the widely existing anions on the degradation indicated the potential application of spongy Co 3 O 4 /PMS system. This study provides a reliable oxidation technology for the removal of organic pollutants, and sheds new light on the cobalt oxide triggered PMS activation process., (Copyright © 2022 Elsevier Ltd. All rights reserved.)