Ion exchange selectivities of calcium alginate gels for heavy metals

An equilibrium model has been proposed and verified, based on the condition s in the gel phase and Donnan equilibrium theory, for the analysis of the e xperimental data on the recovery of lead, copper, cadmium, cobalt, nickel a nd zinc from synthetic, nonmetallic aqueous solutions on calcium alginate g els. This equilibrium model considers that the system behaves as an ion-exc hange process between the calcium in the gets and the divalent metals in so lution, and that the metallic portion enclosed in gel fluid is supposed an important quantitative contribution to the total amount of metal uptake by gels. According to the equilibrium constants calculated, it is deduced that the selectivity order is: Pb>Cu>Cd>Ni>Zn>Co.