Equilibrium and Thermodynamic Studies on Adsorption of Cd2+ and Zn2+ using Brachystegia eurycoma Seed coat as Biosorbent

摘要

The potential of B.eurycoma seed coat as biosorbent for removing Cd~(2+) and Zn~(2+) from aqueous solutions has been studied. Batch adsorption experiments were carried out as function of pH, initial metal ion concentration and temperature. Maximum metal sorption was found to occur at pH 6.0 at initial concentration of 30 mg/L and at 30~(0)C. The maximum adsorption capacity of B.eurycoma corresponding to sites saturation was found to be 4.286 and 4.390 mg/g respectively for initial Cd~(2+)and Zn~(2+) concentration of 30 mg/L at a temperature of 40~(0) C. The results were analyzed by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherms using linearized correlation coefficient at different temperatures. Results showed that the Langmuir and Freundlich models gave the best interpretation to the equilibrium adsorption data for the Cd(II) and Zn(II) ions-B.eurycoma systems studied. The following thermodynamic parameters: ΔH, ΔS and ΔG were calculated and results obtained showed that the adsorption process was exothermic and spontaneous.