Kinetic and Thermodynamic Studies of the Adsorption of Cr(VI) onto Some Selected Local Adsorbents

Abstract

In this study, locally available biomasses obtained from avocado kernel seeds (AKS), Juniperus procera sawdust (JPS) and papaya peels (PP) were investigated as adsorbents for the removal of Cr(VI). The study employed a batch method to investigate the efficiency of the adsorbents. Parameters that influence adsorption such as: pH, adsorbent dose, initial concentration of Cr(VI), contact time and temperature have been studied. Optimum parameters for the adsorption of 5mg L–1 Cr(VI) were: pH: 1, adsorbent dose: 0.5 g, contact time: 160 min and temperature: 313 K. The equilibrium data was best fitted to the Freundlich adsorption isotherm model. The results of kinetic models showed that the pseudo-second-order kinetic model was found to correlate well to the experimental data. The results of thermodynamic parameters showed that the adsorption process is feasible. The positive values of the entropy change suggest increased randomness at solid-liquid interfaces during the adsorption. The efficiencies of the adsorbents towards the removal of chromium from real samples were also examined and were found to remove chromium from waste water.