Sorption of copper, nickel and cadmium on bone char

Abstract

The sorption capacity of bone char was tested on the removal of copper, nickel and cadmium ions, from aqueous solutions. The Freundlich and Langmuir models were applied to the adsorption isotherms. The equilibrium data fitted well with the Langmuir model and the maximum loading capacities showed the following affinity order: Cu²⁺ (1.093 mmol g^–1 at pH _i 3, and 0.884 mmol g^–1 at pH _i 4) > Cd²⁺ (0.760 mmol g^–1 at pH _i 3, and 0.690 mmol g^–1 at pH _i 4) > Ni²⁺ (0.453 mmol g^–1 at pH _i 3, and 0.225 mmol g^–1 at pH _i 4). The kinetic data follow a diffusion model in the film and inside particles. A sorption mechanism based on ion exchange, attack by protons of the carbonate and hydroxide positions in the apatite lattice, and also on the adsorption of protons on the basic active sites of carbon, is proposed to explain the heavy metals removal and the pH decreasing in solution.