Cadmium removal from water using agro based adsorbents

The present work deals with the removal of cadmium from water using lemon peel and green coconut shell powder in batch reactor.Characterization of the biosorbents has been carried out through proximate and ultimate analysis, FTIR, SEM, EDAX etc. The influence of initial cadmium concentration, pH, adsorbent dose, time and temperature on the removal of cadmium has been investigated to find out the optimum process conditions. Analysis of kinetic data shows that the initial adsorption of cadmium is rapid for both the biosorbents, however, equilibrium agitation period is about 5 h for lemon peel and 3 h for green coconut shell powder. The adsorption process for both the biosorbents follows pseudo second order kinetic model. Langmuir isotherm model gives better prediction on adsorption equilibrium than Freundlich isotherm model. The Langmuir maximum adsorption capacity (qmax) for lemon peel and green coconut shell powder is found to be 11.24 mg/g and 14.49 mg/g respectively. The values of thermodynamic parameters such as Gibb¿s free energy change (¿G°), enthalpy change (¿H°) and entropy change (¿S°) for these experiments indicate the spontaneous and exothermic nature of the processes.