Removal of Cu2+ ions using hydrogels of chitosan, itaconic and methacrylic acid: FTIR, SEM/EDX, AFM, kinetic and equilibrium study

A removal of Cu2+ ions from aqueous solutions onto hydrogels of chitosan, itaconic and methacrylic acid has been investigated using batch adsorption technique. The extent of adsorption was investigated as a function of pH, adsorbent dose, initial metal ion concentration, contact time and temperature. The FTIR spectra showed that –NH2, –OH and –COOH groups are involved in the Cu2+ ions adsorption. The surface topography changes were observed by AFM, where the phase images indicated that sorption takes place on the surface of the hydrogel and in the bulk. Pseudo-first order, pseudo-second order and intraparticle diffusion models were analyzed and showed that the Cu2+ ions adsorption followed pseudo-second order kinetics. The equilibrium data were analyzed using Langmuir, Freundlich and Redlich–Peterson isotherms and the best interpretation was given by Redlich–Peterson. The adsorption capacity was found to be 122.59 mg/g, based on the non-linear Langmuir isotherm. Based on the separation factor, RL, the Cu2+ ion adsorption is favorable, while the low activation energies indicate physisorption. Desorption experiments, done with a nitric acid, showed that the investigated hydrogels could be reused without significant losses of the initial properties even after three adsorption–sorption cycles.