Comparisons of Rice Husk and Activated Carbon in Removal of Cadmium from Aqueous Solution in Low Concentration

In this study، rice husk (RH) and activated carbon (AC) adsorbents was used for removing of cadmium ion from aqueous solution at pH = 6. Equilibrium time was shortened with a decrease in initial concentration of Cd from 50 mg/l to 1 mg/l for both adsorbent. This time was 60 and 45 minutes for rice RH and AC، respectively. Furthermore، not only the equilibrium time decreased with increasing initial concentration from 50 mg/l to 500 mg/l، but it became identical for both absorbents. Adsorption efficiency increased with a decrease in initial concentration of solution for both adsorbents. Maximum adsorption efficiency was found for RH and AC at initial concentration of 1 mg/l. Obtained adsorption efficiency at this concentration were approximately 98. 0 and 99. 7 percent for RH and AC، respectively. Fitting the results to the Lagergren (1898) and Ho et al. (1996) models was also attempted; the latter model better described the outcome. Moreover، the Freundlich isotherm better described the data than the Langmuir isotherm.