Ion-exchange equilibria of Ni2+, Co2+, Mn2+ and Mg2+ with iminodiacetic acid chelating resin Amberlite IRC 748

A chelating ion-exchange resin, Amberlite IRC 748 which carries an iminodiacetate acid functional group has been investigated for its adsorption properties towards Ni, Co, Mn and Mg from aqueous solution. Experiments were conducted through batch adsorption by varying the resin volume at three different pH values. It was observed that the amount of metals adsorbed by the resin increased with increasing pH. The applicability of both the Langmuir and Freundlich isotherms were analyzed on the equilibrium data obtained. In all cases, the Langmuir isotherm shows an excellent fit to the experimental data while the Freundlich isotherm failed to predict the data at higher loadings. The resin exhibited high selectivity towards nickel (K = 58,000) and cobalt (K = 16,800), which can be easily separated from magnesium and manganese at pH 4 and 5. The obtained values of the equilibrium constant K (l/mol) matched the expected order of selectivity of this resin which is Ni > Co > Mn > Mg. The results also showed that the adsorption mechanisms of these metals onto the resin follow a combination of monolayer and multilayer adsorption.