A macromolecular N, N-dichlorosulfonamide as oxidant for thiocyanates

Abstract

Macroporous S/DVB copolymer containing N, N-dichlorosulfonamide groups was used for removal of thiocyanate ions from aqueous solutions. This copolymer contains active chlorine in functional groups (8.2 meq Cl ∗/g) and oxidises thiocyanates to considerably less toxic products (such as sulphate, cyanate, carbonate and ammonium ions). The resin was employed in static and dynamic conditions and thiocyanate solutions containing 116 or 560 ppm SCN − were treated. The effects of various parameters on the rates of reaction have been studied. The proposed method is particularly advantageous for treating highly diluted solutions. Using this redox copolymer, it was possible to reduce thiocyanate concentration in solutions below 0.5 mg SCN −/dm 3. The oxidation capacity of the resin was found to be nearly 60 mg SCN −/g. The resin was especially efficient for removal of SCN − ions from neutral and weakly acidic solutions, whereas in alkaline media it lost a part of its oxidising properties as a result of escape of active chlorine. Reactivation of the stripped resin was performed in a one-step treatment by an acidified solution of sodium chlorate(I). The regenerated copolymer can be reused in the next cycle.