Advanced oxidation processes based on sulfite[S(Ⅳ)]have attracted more and more atten-tion due to their low-cost advantages.In this study,we investigated the oxidation effect and mechanism of As(Ⅲ)in high-arsenic groundwater in the presence of bicarbonate(HCO3-)by the Mn(Ⅱ)-activated S(Ⅳ)system.The results showed that HCO3-significantly promoted the oxidation of As(Ⅲ)in the S(Ⅳ)-Mn(Ⅱ)system.Kinetic experiments showed that increasing concentrations of S(Ⅳ)andMn(Ⅱ)promoted the oxidation of As(Ⅲ),but too high concentrations inhibited the oxidation process.The effect of pH on the oxidation of As(Ⅲ)due to the species changes of S(Ⅳ)and Mn(Ⅱ)in the reaction solu-tion.The promotion effect of HCO3-on the oxidation of As(Ⅲ)may due to two aspects:(1)it formed weak coordination with Mn(Ⅱ),which was helpful for the combination of S(Ⅳ)and Mn(Ⅱ);(2)it promoted the oxidation of Mn(Ⅱ)to Mn(Ⅲ),which was favorable for the formation of SO4·-.Quenching experiments revealed that SO4·-was the primarily reactive oxygen species in the oxidation of As(Ⅲ).This study enhances the understanding of the S(Ⅳ)-HCO3--Mn(Ⅱ)system and provides a new solution for the treatment of high arsenic water.
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