The removal of Cu(II) and Co(II) from aqueous solutions using cross-linked chitosan-Evaluation by the factorial design methodology

A 23 factorial design was employed to evaluate the quantitative removal of Cu(II) and Co(II) on glutaraldehyde-cross-linked chitosan from kinetic isotherms, using chitosan masses of 100 and 300 mg and temperatures of 25 and 35 °C. The adsorption parameters were analyzed statistically using modeling polynomial equations and a cumulative normal probability plot. The results indicated the higher quantitative preference of the chitosan for Cu(II) in relation to Co(II). Increasing the chitosan mass decreases the adsorption/mass ratio (mol g−1) for both metals. The principal effect of the temperature did not show statistical importance. The adsorption thermodynamic parameters, namely ΔadsH, ΔadsG and ΔadsS, were determined. Exothermic and endothermic results were found in relation to a specific factorial design experiment. A comparison of ΔadsH values was made in relation to some metal-adsorbent interactions in literature. It is suggested that the adsorption thermodynamic parameters are determined by the influence of the principal and interactive experimental parameters and not by the temperature changes alone.