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

摘要

Natural white clay obtained from Pohang city in Korea was treated with 6 M H2 SO4 and heated at 90 ℃ 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 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 Cd~(2+)from wastewater.