Modified chitosan and calcium alginate biopolymer sorbents for removal of nickel (II) through adsorption

Removal of nickel (II) from aqueous solutions through adsorption on to biopolymer sorbents, such as calcium alginate (CA), chitosan coated calcium alginate (CCCA) and chitosan coated silica (CCS), was studied using equilibrium batch and column flow techniques. The biosorbents were characterized by FTIR, SEM, TGA and surface area analysis. The extent of adsorption was found to be a function of the pH of the solution, contact time, sorbate concentration and adsorbent dose. The optimum pH was found to be 5.0. The adsorption of Ni (II) ions on CA was comparatively higher than CCCA and CCS. Adsorption of Ni (II) on to the biopolymers followed pseudo-second order kinetics. The equilibrium adsorption data for Ni (II) on CA, CCCA and CCS were fitted to Freundlich, and Langmuir Isotherms. The maximum monolayer adsorption capacity of the biosorbents (CA, CCCA and CCS), as obtained from Langmuir adsorption isotherm, was found to be 310.4, 222.2 and 254.3 mg/g, respectively. Breakthrough curves were obtained for adsorption of Ni (II) on all the three adsorbents through column flow technique. The Ni (II) loaded biosorbents were regenerated using 0.1 M EDTA solution.