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

Abstract

AbstractNatural white clay obtained from Pohang city in Korea was treated with 6 M H2SO4 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 Cd2+ 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 Cd2+ occurred steeply at initial contact time and reached equilibrium within 0.5 h. The amount of Cd2+ adsorbed at equilibrium reduced from 94.2% to 37.94% by increasing initial Cd2+ concentrations from 10 mg L−1 to 100 mg L−1, whereas the amount of Cd2+ increased from 13.54% to 93.38% as adsorbent dose increases from 0.1 g to 1.0 g. The adsorption data of Cd2+ 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 Cd2+ due to their higher correlation coefficient R2. 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 Cd2+ from wastewater.