Adsorption of Cu(II) ion from aqueous solutions on hydrogel prepared from Konjac glucomannan

A novel adsorbent, biodegradable Konjac glucomannan-poly(acrylic acid) (KGMP) hydrogel, is prepared by Konjac glucomannan grafting with acrylic acid. The adsorption properties of the KGMP for Cu(II) ion removal from aqueous solutions are investigated. The experiments are performed under various impact factors such as initial Cu(II) ion concentration, pH, contact time, temperature and salt ionic strength. The Langmuir and Freundlich isotherm are employed to discuss the adsorption behavior. The result shows the equilibrium data obtained at different temperatures are represented perfectly by Langmuir isotherm model compared to the Freundlich isotherm models. The monolayer saturation adsorption capacities of KGMP for Cu(II) ion is found to be 27.1739, 30.2115, 34.1297 and 41.6667 mg g⁻¹ at 298, 303, 308 and 313 K, respectively. Thermodynamic parameters such as ΔG, ΔH and ΔS are calculated. The kinetics studies show that adsorption process follows the pseudo-second-order model and the adsorption process is mainly controlled by both surface reactivity and intra-particle diffusion. FT-IR analysis shows that a large number of carbonyl, ester, and hydroxyl groups are included in the external surface of the KGMP, SEM indicates that the rough, irregular and pores of different size and shapes on surfaces of the KGMP are observed before adsorption. The present study indicates that the KGMP is an effective adsorbent for the removal of Cu(II) ion from aqueous solutions.