Sorption of Cadmium and Lead by Chelating Ion Exchangers Ostsorb DITHIZON and Ostsorb SALICYL

Abstract

The pH and I (ionic strength) dependences of exchange capacity of chelating ion exchangers Ostsorb based on spherical cellulose modified with functional groups of dithizone and salicylic acid have been studied in the sorption of Pb(II) and Cd(II) ions. The cellulosic selective sorbents Ostsorb DITHIZON and Ostsorb SALICYL can be used for sorption of Pb(II) and Cd(II) ions from aqueous solutions of I = 0 - 1 mol l-1 (Pb) and I = 0 - 5 mol l-1 (Cd); the dithizone ion exchanger retains both metals most effectively at pH 7 - 8, the salicyl ion exchanger at pH 5.5 - 6.5 (Pb) or pH 4 - 9 (Cd). Because of the formation of precipitates of hydrolytic products of the two metals in neutral and alkaline media, it is suitable to carry out the sorption in media of mild acidity if possible, particularly so at the metal concentrations above 1 mg l-1. Increasing ionic strength affects the exchange capacity for both metals in a negative way.