Poly (Acrylate -Acrylic acid-co-Maleic acid) hydrogel: A Cost Effective and Efficient Method for Removal of Metal Ions from Water

Noncompetitive adsorption of Zn (II) and Cd(II) from aqueous solution was carried out using Poly(Acrylate-Acrylic acid)(PAA) and Poly(Acrylate -Acrylic acid-co-Maleic acid)(PAAAM) hydrogels as adsorbents. Adsorption capacity was affected by the adsorbate concentration, temperature, and time and was investigated in detail. Results showed a decrease in adsorption with increase in the temperature whereas a steady increase followed by an equilibrium state (within 60min.) was observed with time. The maximum adsorption capacity obtained for Zn2+ and Cd2+ were 227.89 and 369.51mg/g, respectively. Even though the isotherms could be explained both with Langmuir and Freundlich, the present result was better explained by the Freundlich isotherm. This points to the fact that the hydrogel surface is heterogeneous and the adsorption occurred is a multilayered one. Adsorption was well modeled by the pseudo-second-order kinetic model. All metal ions used in the studies were successfully desorbed using 0.1N HCl and the regeneration of hydrogel took place even after four cycles without any loss in its adsorption capacity.