Preparation of Porous Activated Carbons from Rice Husk with Alkali Activation

Abstract

Activated carbons were prepared from rice husk by chemical activation using various alkali hydroxides (KOH, NaOH) as activating agent. The influences of activation parameters such as impregnation ratio, activation temperature and retention time on the final products were investigated, and the optimum preparation conditions were determined. The products were characterized by nitrogen gas adsorption isotherms at −196 °C and the surface areas and pore volume of the carbon were estimated by BET method. The specific surface area and pore volume were as high as 2960, 2450 m2/g and 2.159. 1.525 ml/g for activated carbons prepared using KOH, NaOH, respectively. Adsorption of Cr (VI) ions from solutions onto the resulting activated carbons have been studied. The effect of the solution pH on the adsorption was studied in the pH range 1-7 and 25±2 °C. The results show that the process was pH dependent. The experimental adsorption isotherm data were analyzed using three models, Freundlich, Langmuir and BET isotherm models and various adsorption parameters have been calculated. Equilibrium data were best represented by the Langmuir isotherm model. The results indicated that the prepared activated carbons are suitable adsorbent for the removal of Cr (VI) from wastewaters effluents.