Adsorption of copper from aqueous solution by activated carbons obtained by pyrolysis of cassava peel

摘要

Activated carbons (ACs) were prepared by pyrolysis of cassava peel in presence of chloride zinc (chemical activities). Cassava peel from Colombian cassava cultives were impregnated with aqueous solutions of ZnCl_2 following a variant of the incipient wetness method. Different concentrations were used to produce impregnation ratios of 40,70,110 and 160 wt.%. Activation was carried out under argon flow by heating to 823 K with 1 h soaking time. The porous texture of the obtained ACs was characterized by physical adsorptions of N_2 at 77 K and CO_2 at 273 K. The impregnation ration had a strong influence on the pore structure of these ACs, which could be easily controlled by simply varying the proportion of ZnCl_2 used in the activation. Thus, low impregnation ratio led to essentially microporous ACs. At intermediate impregnation ratios, ACs with wider pore size distribution (from micropores to mesopores) were obtained. Finally, high impregnation ratios yielded essentially mesoporous carbons with high surface area and pore volume. The four best-fit three-parameter isotherms Sips, Toth, Radke-Prausnitz and Vieth-Sladek suggests that the sorption capacity of activated carbon of cassava peel to uptake copper ions to be 55 mg/g.