Fate and transformation of iodine species during Mn(VII)/sulfite treatment in iodide‐containing water

Abstract

During oxidative treatment of iodide (I À )-containing waters, I À is easy to be oxidized into hypoiodous acid (HOI) by various oxidants and the further reaction of HOI with organic compounds can lead to the formation of iodinated disinfection by-products (I-DBPs). Oxidation of HOI to iodate (IO 3 À ) or reduction of HOI to I À has been proposed to reduce the formation of I-DBPs.Because the reaction of HOI with sulfite proceeds rapidly, this study examined the fate of iodine and the formation of I-DBPs in Mn(VII)/sulfite process.Results showed that I À was oxidized to HOI but the further formation of IO 3 À was suppressed due to the fast reduction of HOI to I À by sulfite. The reactions of HOI with SO 3 2À and IO À with SO 3 2À are the major pathways with speciesspecific second-order rate constants determined to be 1.12 Â 10 5 M À1 s À1 and 9.43 Â 10 7 M À1 s À1 , respectively. The rapid reaction of HOI with sulfite plays an essential role in minimizing the formation of iodinated products in HOIand phenol-containing solutions. The toxic risk analysis showed that the toxicity of the generated DBPs from Mn(VII)/sulfite pre-oxidation followed by chlorination only changed slightly. Practitioner Points• The decay of I À was negligible in Mn(VII)/sulfite process.• The rapid reaction of HOI with SO 3 2À resulted in the negligible generation of IO 3 À .• Mn(VII)/sulfite process exerted slight influence on the formation of I-DBPs.• Mn(VII)/sulfite process is promising for the pretreatment of I À -containing water.