Selectivity study of heavy metal ions adsorption onto zeolite-g-polyacrylamide

In our previous study, the zeolite-g-polyacrylamide (zeolite-g-PAAM) adsorbent has been successfully synthesized by radiation-induced graft polymerization by using gamma rays with the simultaneous technique. The adsorption capacity of zeolite-g-polyacrylamide adsorbent towards heavy metal ions both in single and multi-component are greatly influenced by adsorption conditions. In this study, batch adsorption experiments were conducted at pH 2, 3, and 5. The effect of pH on the adsorption capacity and selectivity of metal ions adsorption onto the adsorbent was investigated. The amount of metal ions removed at equilibrium both in the single and multi-component system were interpreted by using the coefficient of distribution. The results indicated that the adsorption selectivity sequence of zeolite-g-PAAM adsorbent towards metal ions changed with pH. The selectivity sequence of heavy metal ions adsorbed on the adsorbent for a single component system was Cu>Zn>Ni (pH 2), Ni>Cu>Zn (pH 3), and Cu>Ni>Zn (pH 5). On the other hand, the adsorption selectivity for a multi-component system was found to be selective for nickel ions at pH 2 and copper ions at pH 3 and 5. Therefore, the initial pH and the presence of other metal ions give a significant role in the adsorption selectivity of metal ions onto the zeolite-g-PAAM adsorbent. The results showed that zeolite-g-PAAM adsorbent was higher selective for Cu metal ions both in SC and MC systems. The hydroxyl species is kindly formed in the MC system compared to the SC system resulting in the adsorption capacity of Cu was higher in the MC system.