Adsorption of 60Co2+ on hydrous manganese oxide powder from aqueous solution

Abstract

Summary Hydrous manganese oxide (HMO) was synthesized and its ability to sorb 60Co2+ from aqueous solution was studied under static conditions as a function of contact time, cobalt concentration (10-2-10-7M), temperature (303-333K) and pH of adsorptive solution (2.2-11.4). X-ray diffraction was used in characterization of synthesized HMO. Low concentration of 60Co2+ solution, high pH and high temperature were the most favorable conditions for the adsorption process. The results show that the removal process is complete in 40 minutes, obeys a first order rate law and can be described using the Freundlich adsorption model. The standard enthalpy of the system was ΔH 0 = 12.5 ± 0.2 kJ mol-1 and cobalt desorption indicates that the uptake process proceeds via cation exchange. The removal of cobalt ions by HMO appears to be endothermic and irreversible. The values of calculated ΔG 0 and ΔS 0 were -17.0 ± 3.0 kJ mol-1 and (9.8 ± 0.2) × 10-2 kJ K-1 mol-1 respectively, this indicates spontaneity of the process and the degree of freedom of ions is increased by adsorption.