NONSTOICHIOMETRIC BINDING OF LEAD(II) IONS BY SODIUM ALGINATE

The capability of sodium alginate to bind up to 500 Pb2+ ions per uron ide unit is shown. The residual concentration of Pb2+ ions in solution is as small as 4.10(-4) - 3.10(-3) mol . 1(-1) (concentration of sodi um alginate-2.10(-4) - 1.10(-3) g-equiv . 1(-1); initial concentration of a lead salt - 0.001 - 0.5 mol . 1(-1) ionic strength-0.15; ambient temperature). This does not depend on the concentrations of reagents. Interactions are reversible. They can at least in part result from th e sorption of the excess of Pb2+ ions by the initially formed lead alg inate gel.