Equilibrium, kinetic and thermodynamic studies on biosorption of copper and zinc from mixed solution by Erythrina variegata orientalis leaf powder

Present investigation is undertaken to explore the feasibility of biosorption for the removal of copper and zinc from aqueous Cu-Zn solution using Erythrina variegata orientalis leaf powder. Batch investigations indicate that biosorption of Cu-Zn mixture is gradually increased with increase in pH from 1 to 6 (38.25 to 44.77 mg/g). The biosorption of Cu-Zn mixture is increased from 86.3 to 91.9% (86.27 to 45.93 mg/g) with increase in biosorbent dosage from 1 to 2 g/L. 91.9% (45.93 mg/g) of Cu-Zn mixture is removed from the solution containing 100 mg/L of Cu and Zn agitated with 2 g/L of 45 μm size adsorbent for an equilibrium agitation time of 30 min. The experimental data are well described by Langmuir (R 2 =0.99), Freundlich (R 2 =0.98) and Temkin (R 2 =0.98) isotherms. The sorption studies follow the second order rate expression (R 2 = 0.99) and rate constant is 9.39 g/mg-min. The biosorption is found to increase with decrease in temperature of the solution. From the thermodynamic parameters, sorption is found to be exothermic and reversible.