Equilibrium, thermodynamic and kinetic studies on aluminum biosorption from aqueous solution by brown algae (Padina pavonica) biomass

This paper presents the equilibrium, thermodynamic and kinetic studies on aluminum biosorption from aqueous solution by brown algae (Padina pavonica) biomass. Optimum biosorption conditions were determined as a function of pH, biomass dosage, contact time, and temperature. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherm of Al(III) by P. pavonica biomass. The biosorption capacity of P. pavonica biomass was found as 77.3 mg/g. The metal ions were desorbed from P. pavonica using 1 M HCl. The high stability of P. pavonica permitted a slight decrease about 20% in the recovery of Al(III) ions after 10 times of adsorption-elution process. The mean free energy value evaluated from the D-R model indicated that the biosorption of Al(III) onto P. pavonica biomass was taken place by chemical ion exchange. The calculated thermodynamic parameters, ΔG°, ΔH° and ΔS° showed that the biosorption of Al(III) onto P. pavonica biomass was feasible, spontaneous and endothermic under examined conditions. Experimental data was also tested in terms of biosorption kinetics using pseudo-first-order and pseudo-second-order kinetic models. The results showed that the biosorption processes of Al(III) onto P. pavonica biomass followed well pseudo-second-order kinetics.