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

Abstract

Present investigation is undertaken to explore the feasibility of biosorption for the removal of copper and zinc from aqueous Cu-Zn solution using <i>Erythrina variegata orientalis</i> 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&nbsp;mm size adsorbent for an equilibrium agitation time of 30 min. The experimental data are well described by Langmuir (R²=0.99), Freundlich (R²=0.98) and Temkin (R²=0.98) isotherms. The sorption studies follow the second order rate expression (R² = 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.