Effect of Cu2+, Zn2+, and Mn2+ ions on the water absorption of polyelectrolyte hydrogels based on polyacrylonitrile fiber hydrolyzate

Polyelectrolyte hydrogels based on 40% aqueous-salt solutions of polyacrylonitrile fiber hydrolyzate were prepared using products of thermal decomposition of ammonium persulfate as cross-linking agent. Swelling of these gels in aqueous solutions of zinc, copper, and manganese sulfates is followed by the inverse process leading to the collapse of the hydrogels. The use of complex salts of the above ions prevents the inverse process. The relationships characterizing the influence of the cross-linking agent concentration on the initial swelling rate and on the equilibrium and maximum swelling in distilled water and in 0.01 M solutions of copper sulfate and disodium copper ethylenediaminetetraacetate were determined.