Biosorptive Removal of Lead (II), Cadmium (II) and Arsenic (III) from Aqua Media on Vigna Unguiculata Leaf Powders

The biosorption of Cd (II), As (III) and Pb (II) ions from solution utilizing Vigna unguiculata leaf powders (VULP) as a low cost biosorbent was studied. The influence of temperature, metal ion concentration, biosorbent dose, contact time and pH on the sequestration process was examined by batch procedure. Increase in the biosorption of the three metal ions with increased pH and biosorbent dosage was obtained in this study.Equilibrium contact time of 20, 40 and 50min was achieved for Cd(II), As (III) and Pb(II) ions and biosorption was in the order As(III)> Cd(II) >Pb(II). Isotherm analysis was performed by the application of Langmuir, Freundlich, Flory-Huggins and Scatchard models. The Langmuir model gave the best fit with maximum monolayer biosorption capacity of 109.1, 105 and 119.3 mg/g for Cd (II), Pb (II) and As (III) respectively. Scatchard model confirmed a homogenous surface of VULP and monolayer biosorption of metal ions. Pseudo second order model showed the best fit compared to pseudo first order, Elovich and Banghams kinetic models according to kinetic analysis. Thermodynamics study revealed a feasibly, spontaneous exothermic biosorption process. The result showed good potentials of VULP as suitable cheap biosorbent for attenuation of Cd (II), Pb(II) and As (III) ions from polluted wastewaters.