Comparison of natural white clay and acid‐activated white clay for removal of Cd(II) ion from aqueous solution

Abstract Natural white clay obtained from Pohang city in Korea was treated with 6 M H 2 SO 4 and heated at 90 °C for 8 h. The generated clay, called as acid‐activated white clay in this study, was employed as an adsorbent for the removal of Cd 2+ in aqueous solution. It was found that the specific surface area and the pore volume of acid‐activated white clay were enhanced when compared with those of natural white clay. The adsorption rate of acid‐activated white clay toward Cd 2+ occurred steeply at initial contact time and reached equilibrium within 0.5 h. The amount of Cd 2+ adsorbed at equilibrium reduced from 94.2% to 37.94% by increasing initial Cd 2+ concentrations from 10 mg L −1 to 100 mg L −1 , whereas the amount of Cd 2+ increased from 13.54% to 93.38% as adsorbent dose increases from 0.1 g to 1.0 g. The adsorption data of Cd 2+ by acid‐activated white clay were introduced to pseudo‐first‐order and pseudo‐second‐order kinetics, and Freundlich and Langmuir adsorption isotherms, respectively. It was seen that the pseudo‐second‐order kinetics and the Langmuir isotherms were applied well to describe the adsorption behavior of acid‐activated white clay toward Cd 2+ due to their higher correlation coefficient R 2 . The maximum adsorption capacities of Langmuir, Q , for natural white clay and acid‐activated white clay were found to be 17.15 mg g −1 and 36.48 mg g −1 , respectively. The results of study suggest that acid‐activated white clay can be used as an efficient and low‐cost material for the removal of Cd 2+ from wastewater.