Using macroporous N-chlorosulfonamide S/DVB copolymer as an aid to iron removal from water

Abstract

The de-ironing of water is a basic stage in water-treating technology. Consequently, the oxidation of easily soluble Fe(II) to poorly soluble Fe(III) compounds is indispensible. In order to oxidize Fe(II) ions to Fe(III), a macromolecular and macroporous product in bead form was used: polystyrene cross-linked by divinylbenzene, which contains pendant N-chlorosulfonamide groups in both the sodium and hydrogen forms. To assist the process of removing residual iron from water, this polymer - a macromolecular analog of Chloramine T, containing more than 4.0 mequiv of active chlorine/g - was prepared, starting from the sulfonate cation exchanger Amberlyst 15 by a three-step transformation of its functional groups. The investigations were carried out using both the batchwise and column methods, and 0.0025 M as well as 0.02 M FeSO4 solutions with different acidity were used. We found that the oxidation of ferrous ions to ferric by N-chlorosulfonamide copolymer was effective and was favored by a low pH. The oxidative ability of the copolymer was 225 mg Fe(II)/g. We established that the oxidation reaction could be operated in two directions. In acidic media (pH < 2.5), Fe(III) ions remained in the solution as products of the reaction. The higher the pH, the more the poorly soluble ferric compounds sedimented in the inner structure of the copolymer beads. In this way, new hybrid materials were obtained, i.e., by ferrous/ferric oxides and hydroxides, by nanoparticles, modified materials which can serve as specific reacting sorbents and catalysts.