Biosorption of Heavy Metals from Aqueous Solutions by Parkia biglobosa Biomass: Equilibrium, Kinetics, and Thermodynamic Studies

摘要

The adsorption capacities of Parkia biglobosa chaff biomass (PBC) and Parkia biglobosa pulp biomass (PBP) for Cr(Ⅲ), Cd(Ⅱ), Ni(Ⅱ), and Pb(Ⅱ) ions were studied. Experimental data suggested the highest monolayer sorption capacities of PBC and PBP, q_(max_1) at equilibrium to be 170.07 mg/g at pH 7.0 and 324.68 mg/g at pH 6.0, for the uptake of Cr(Ⅲ) ions, respectively. The minimum adsorption capacities obtained by PBC and PBP were 60.72 mg/g for Ni(Ⅱ) and 16.70 mg/g for Cd(Ⅱ) at pH value of 2.0, respectively. Pseudo-second order kinetic model fits the all experimental data best, suggesting that the entire adsorption processes might have occurred by chemisorption mechanism. Thermodynamic data indicated that the adsorption of various metal ions by PBC and PBP was endothermic, with increase in disorderliness of the system. The Gibb's free energy values for the uptake of Cr(Ⅲ), Cd(Ⅱ) and Ni(Ⅱ) ions by PBC indicated the spontaneity of the processes. Moreover, the Gibb's free energy values for the uptake of Pb(Ⅱ) ion by PBC depicted the non spontaneity of the processes. Also, Gibb's free energy values for the adsorption of various metal ions by PBP depicted the spontaneity of the processes.