The removal of Cr (VI) from aqueous solution by dried powder of activated sludge: kinetic and equilibrium studies

Background: Nowadays, different methods are applied for the removal of heavy metals from the aqueous resources that the adsorption process is one of them. The chromium VI is one of the most prevalent contaminants which create serious difficulties; so, it should be removed from the contaminated waters by an effective method before being leaved into the environment. The present research investigated the use of dried powder of activated sludge of Kavirtire wastewater treatment plant as bio sorbent for removal of chromium (VI). Methods: In the present experimental study, the effects of pH, adsorbent dose, primary concentration of metal and contact time on the removal of chromium (VI) from the aqueous solutions were studied. Then, the equations of isotherm and adsorption kinetic were specified based on the optimal conditions. The absorbent features were analyzed by SEM and EDX techniques. Results: The maximum efficiency of the removal of chromium (VI) at pH 2, optimal dose of 5 g/L, contact time of 60 min and with primary concentration of 15 mg/L was reported 99.83 percent. The study of relation of the isotherm and kinetic in the reaction revealed that the process of adsorptions of chromium follows the Freundlich model (R^2=0.90) and the pseudo second order kinetic model (R^2= 1), respectively. Conclusions: The dried powder of activated sludge can be applied as a proper adsorbent for the removal of Chromium VI from the aqueous resources.