Poly(styrene-divinylbenzene) copolymers with N-chlorosulfonamide functional groups as oxidants for arsenite ions in aqueous media — redox studies

Abstract

Two macromolecular oxidants that were macroporous styrene/divinylbenzene copolymers containing N-chlorosulfonamide functional groups in the sodium form — RCl/Na (a macromolecular analog of chloramine-T) or in the hydrogen form — RCl/H (there is no analog among low-molecular compounds) were synthesized and used as oxidants of arsenites in dilute aqueous solutions. The reaction course was examined depending on stoichiometric ratios of reagents by special reductometric, potentiometric measurements at different pH values. In weak alkaline medium (pH ~11.5) the RCl/Na copolymer was ineffective as an As(III) oxidant, the reaction proceeded with difficulty, and the redox potential reached a negative value. In weak acidic medium (pH~3.0) the reaction proceeded efficiently enough, but the flat titration curve indicated the unfavorable kinetics of As(III) oxidation by means of RCl/H (despite the high redox potential in the reaction medium). In neutral medium (pH ~6.5) the reaction proceeded with the highest effectiveness. In this case the titration curve had a characteristic, classic shape, indicating the advantageous kinetics of As(III) oxidation by means of RCl/Na (despite the lower redox potential in the reaction medium).