Preparation and characteristics of activated carbon from olive stones and walnut shells

The preparation of activated carbon from agricultural waste could increase economic return and reduce pollution. Activated carbon has been processed from different types of agricultural material, such as olive stone, acorn, pecan, walnut shells, and stone fruits. The objectives of this study were to prepare and to characterize activated carbon from two abundant waste material produced in Argentina. Activated carbon was made from olive pits (OP) and walnut shells (WS) by treatment with 50 and 75% (w/w) of KOH. The two types of activated carbon obtained were evaluated by iodine adsorption. The characterization of surface carbons was performed by scanning electron microscopy (SEM). Activated carbon yields from OP was higher than WS. The highest carbon yields were obtained with 75% KOH concentration in both OP and WS. The characteristics of the starting materials, the activating agent concentration, and the carbon particle size influenced the iodine adsorption capacity. Adsorptive properties were highest in the OP powdered carbon obtained at 75% KOH concentration. The WS-activated carbon had macrocroporous structures with a pore size distribution more homogeneous than OP.