The Zn2+, Cd2+, and Ni2+ extraction rate is high for the Dowex 50W resin for the first 40min of the process. This could be explained by the easy access of sulfonic functional groups for ion exchanging. It is natural that a high degree of swelling, as well as a cross-linking agent concentration, leads to the polymer chain extension that makes the functional groups of resin efficiently involved in the exchange process. Ion exchange of the –SO3H groups increases with atomic number, valence and degree of ionization of the exchange metal ion. The ionic radius changes of these ions are Ni2+