KEYWORDSThe adsorption of cobalt ions (Co 2+ ) from aqueous solution onto chitosanhydroxyapatite composite is investigated in this study. The effects of adsorption time, initial concentration, temperature, and pH are studied in details. Kinetics and thermodynamics of the adsorption of Co 2+ onto the chitosan-hydroxyapatite are also investigated and the adsorption kinetics is found to follow the pseudo-second-order model with an activation energy (Ea) of 10.73 kJ/mol. Thermodynamic studies indicates that the adsorption follows the Langmuir adsorption equation. The value of entropy change (∆S ө ) and enthalpy change (∆H ө ) are found to be 83.50 and 18.09 kJ/mol, respectively. The Gibbs free energy change (∆G ө ) is found to be negative at all fives temperatures, demonstrating that the adsorption process is spontaneous and endothermic.