Removal of Cadmium (II) from Aqueous Medium Using Vigna radiata Leave Biomass: Equilibrium Isotherms, Kinetics and Thermodynamics

In the present study, a novel biosorbent Vigna radiata leaves biomass (L. biomass) was utilized for cadmium (II) extraction from aqueous medium. Cadmium (II) free and cadmium (II) loaded L. biomass was analyzed by Fourier transform infrared (FTIR) spectroscopy. Adsorption of cadmium (II) from aqueous medium was studied under various conditions such as adsorbent dose, agitation time, pH and temperature of the medium to optimize the process variables. Different models including Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (DR) were used to elaborate the insight of adsorption process. Best interpretation of biosorption process was given by Langmuir model. Value of maximum adsorption capacity (q_m) calculated from Langmuir isotherm model was found to be 13.44 mg/g. Results indicated the establishment of physical interaction between cadmium (II) ions and functional groups of L. biomass. Kinetic study for adsorption of cadmium (II) ions on L. biomass was done by applying pseudo first order, pseudo second order, elovich and intra-particles diffusion models. Biosorption process best followed the pseudo second order kinetics. Value of standard Gibbs energy (ΔG°) and standard enthalpy change (ΔH°) showed the feasibility, spontaneity and endothermic nature of adsorption process. Percentage removal efficiency of L. biomass for cadmium (II) was successfully maintained for four cycles. Biomass has a potential to be used as an efficient adsorbent for the removal of cadmium (II) from different polluted water samples.