Absorption/release of polyvalent metal ions by a polyelectrolyte gel.

The swelling/contraction dynamics of a strongly charged gel immersed in a copper sulphate solution were studied. Changes in the size of the gel particle and the penetration of metal ions inside the network were monitored by optical microscopy. The equilibrium state was attained in two steps: First, the gel swells, mainly by absorbing water, and then it collapses, to the almost dry state. The release of copper ions from the contracted gel when it was placed in acidic medium was studied as a function of time using optical microscopy. The influence of the acid concentration on the rate of ion release and on changes in the particle size of the gel are discussed.