Activation of palm shells by phosphoric acid impregnation for high yielding activated carbon

A compilation of the yield of activated carbons corresponding to good textural characteristics (BET surface area > 1000 m2/g) derived from palm shells, irrespective of the activation process has revealed a yield lower than 30%. Having known the ability of chemical activation methods to produce high yielding activated carbons, the present study utilizes a two stage activation process in a self-generated atmosphere to prepare activated carbon. A low activation temperature (425 °C) and activation time (30 min) has been utilized, while varying the impregnation ratio of phosphoric acid from 0.5 to 3. The yield of activated carbon is not found to vary with the impregnation ratio and is found to be around 50%. The textural characteristics are found to improve with increase in the impregnation ratio, up to an optimal value of 2, while found to decrease beyond. The BET surface area of activated carbon corresponding to an impregnation ratio of 3, with an iodine number of 1035 mg/g is found to be 1109 m2/g with a pore volume of 0.903 cm3/g and an average pore diameter of 3.2 nm. The textural characteristics of activated carbon reveal that the pore size is widely distributed with the contribution of micropores around 50%.