Green Synthesis of CdS Nanoparticles and their Potential Application towards Adsorption of Lead and Cadmium ions

Watermelon rind aqueous extract mediated synthesis of CdS nanoparticles was investigated for its efficiency towards removal of lead and cadmium ions from aqueous solutions. Batch adsorption investigations were performed to optimise the experimental conditions. The optimised conditions were found to be pH 6, 1 g L-1, 30 min and 303 K respectively for the removal of lead and cadmium ions. The equilibrium data obtained was analysed with isotherm models and it was found that Langmuir and Freundlich isothersm explain better and the loading capacities were found to be 332.2 and 318.7 mg L-1 respectively for Pb2+ ad Cd2+ ions. Kinetic investigations suggest that pseudo second order kinetic model fits well to the experimental data suggesting that chemical reactions govern the rate limiting step. The spontaneous and exothermic nature of the present process was successfully demonstrated by the thermodynamic investigations. Desorption and regeneration studies suggest that the CdS nanoparticles can be successfully regenerated 5 times and reused in the adsorption process.