Preparing activated carbon from various nutshells by chemical activation with K2CO3

Abstract

We have prepared activated carbons by chemical activation with K2CO3 from five kinds of nutshells: almond shell (AM), coconut shell (CN), oil palm shell (OP), pistachio shell (PT) and walnut shell (WN). When prepared at 1073 K, the activated carbons from all the nutshells had the maximum specific surface areas. According to the maximum values of specific surface areas, the activated carbons prepared were classified into two groups: Group-L and Group-S; the former group included activated carbons with high specific surface area and the latter included those with lower specific surface area, respectively. It was found that K2CO3 effectively worked as an activation reagent, but differently in the temperature ranges below 800 and above 900 K. Due to impregnation, cellulose and hemi-cellulose were modified by K2CO3 and accordingly the weight loss behaviors of the nutshells were changed in the temperature range below 800 K. In the temperature range above 900 K, carbon in the chars was removed as CO gas by the reduction of K2CO3 to increase the specific surface area and the pore volume. It was deduced that the difference between the specific surface areas of Group-L and those of Group-S correspond to the difference between weight loss behaviors in the temperature range above 900 K.