Evaluation of Cu2+, Co2+ and Ni2+ ions removal from aqueous solution using a novel chitosan/clinoptilolite composite: Kinetics and isotherms

A novel chitosan/clinoptilolite composite, as beads with an average size of 800 μm in diameter, in dry state, was used for comparative studies on the removal of toxic metal ions like: Cu2+, Co2+ and Ni2+ from aqueous solutions. The effects of the initial pH value of the solution, contact time, the initial metal ion concentration and temperature on the adsorption capacity of the composite were investigated. The kinetics data were analysed by pseudo-first order, pseudo-second order, and intra-particle diffusion equations. The adsorption kinetics were well described by the pseudo-second order equation, and the adsorption isotherms were better fitted by the Langmuir equation. The maximum theoretical adsorption capacities of the chitosan/clinoptilolite composite for Cu2+, Co2+ and Ni2+ were found to be 11.32, 7.94 and 4.209 mmol/g, respectively. The negative values of Gibbs free energy of adsorption (ΔGads°) indicated the spontaneity of the adsorption of all metal ions on the novel composite. Desorption of the metal ions from the composite was achieved by using 0.1 M HCl in about 20 min.