A macromolecular N-chlorosulfonamide as oxidant for thiocyanates

Abstract

A redox copolymer, macroporous poly(S/DVB) resin having N-chlorosulfonamide groups – obtained by chemical modification of Amberlyst 15 – was used for removal of thiocyanates from aqueous solutions. This resin contains active chlorine in functional groups (2.15 mmol/g) and shows oxidative properties. It was employed in static and flow systems to oxidise thiocyanate ions to less toxic compounds. The reactions were carried out in aqueous media containing 116 or 580 mg SCN −/dm 3 at different pH values. The data showed that the –SO 2NClNa groups containing resin easily oxidised thiocyanates forming sulphates and cyanates. Cyanates are unstable under the reaction conditions (hydrolysis). The concentration of thiocyanates dropped below 0.5 mg/dm 3 in most of the tested solutions. The thiocyanate-oxidising capacity of the resin was found to be 0.55 mmol/g. The kinetic course of the reaction strongly depends on the pH of the reaction medium (acidic medium>neutral medium>alkaline medium). The functional groups of the reactive copolymer during thiocyanate treatment undergo dechlorination to sulfonamide groups. The exhausted copolymer can be regenerated by sodium chlorate(I) and reused for continuous processes.