Fe(IV) and Fe(V) are promising oxidants for the selective removal of emerging organic contaminants (EOCs) from water under near-neutral conditions. The Fe(III)-assisted electrochemical oxidation system with a BDD anode (Fe(III)–EOS–BDD system) has been employed to generate Fe(VI), while the generation and contributions of Fe(IV) and Fe(V) have been largely ignored. Thus, we examined the feasibility and involved mechanisms of the selective degradation of EOCs in the Fe(III)–EOS–BDD system under near-neutral conditions. It was found that Fe(III) application selectively accelerated the electro-oxidation of phenolic and sulfonamide organics and made the oxidation system be resistant to interference from Cl–, HCO3 –, and humic acid. Several lines of evidence indicated that EOCs were decomposed via direct electron-transfer process on the BDD anode and by Fe(IV) and Fe(V) but not Fe(VI), besides HO•. Fe(VI) was not generated until the exhaustion of EOCs. Furthermore, the overall contributions of Fe(IV) and Fe(V) to the oxidation of phenolic and sulfonamide organics were over 45%. Our results also revealed that Fe(III) was oxidized primarily by HO• to Fe(IV) and Fe(V) in the Fe(III)–EOS–BDD system. This study advances the understanding of the roles of Fe(IV) and Fe(V) in the Fe(III)–EOS–BDD system and provides an alternative for utilizing Fe(IV) and Fe(V) under near-neutral conditions.

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.

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