Sequestration of Cd(II), Pb(II) and Zn(II) from aqueous solutions using Snake Tomato (Trichosanthes cucumerina L.) Leaf: kinetics, isotherms and thermodynamics

Abstract

The sequestration of Cd(II), Pb(II) and Zn(II) from aqueous solution using Snake Tomato (Trichosanthes cucumerina L.) leaf (STL) was investigated under various physiochemical parameters. Optimization study carried out using batch biosorption studies on each of the metal ions was found to be dependent on pH. The equilibrium sorption data for the metal system was found to fit best to the Langmuir for Cd(II) and to the Freundlich isotherm for Pb(II) and Zn(II). Pseudo-first order model adequately described the kinetics of Cd(II) while Pseudo-second order model adequately described the kinetics of Pb(II) and Zn(II) sorption with high correlation coefficients, respectively. Thermodynamic parameters such as free energy change (ΔG°), entropy change (ΔS°) and enthalpy change (ΔH°) indicated that the biosorption process of Cd(II), Pb(II) and Zn(II) using STL was spontaneous, feasible and exothermic.