Preparation of activated carbon from jatropha waste via phosphoric acid, potassium hydroxide, and zinc chloride activations

Abstract

The preparation conditions of activated carbon from waste of jatropha were determined at various temperatures (500, 600, and 700oC), activation times (60, 120, and 180 min.), and ratios of raw material:chemical agent (1:0.5-1:2). The derived activated carbon was analyzed for its specific surface area, iodine number, average pore size, net iodine number, net surface area, bulk density, %yield, functional groups, and purity. The best conditions for the production of high surface area of activated carbon from jatropha seed cake and shell were the activation with potassium hydroxide at the activation temperature of 700oC (for both cake and shell), activation time of 180 (cake) and 60 (shell) minutes, and impregnation ratio of 1:0.75 (cake) and 1:0.5 (shell). At this optimal condition, the BET surface areas were 666 and 699 m2/g, and iodine numbers were 696 and 631 mg/g for seed cake and shell, respectively. The average pore size of activated carbon from jatropha shell with zinc chloride was the largest, at 9.86 nm. The structure of activated carbon were mainly amorphous, where the activated carbon with zinc chloride might contain the crystals of ZnO and Zn5(OH)8Cl2 .H2O on the carbon surface. The surface of activated carbon might contain several functional groups including aromatic, benzene derivatives, and hydroxyl groups. When %yield was included in the consideration, the best combination for the production of activated carbon was to use jatropha seed cake as a raw material, and zinc chloride as activating agent as this provided the yield at as high as 0.64 g activated carbon/g raw material.