Mesoporous high-surface-area activated carbon

Coconut shells and palm seeds have been used as raw materials to obtain activated carbons with high surface area by simultaneous treatment with zinc chloride and carbon dioxide as the physical and chemical agents, respectively, Both the surface area and the mesopore content could be tuned by controlling the experimental parameters, viz., ZnCl2-to-raw material ratio, duration of exposure to the carbon dioxide atmosphere and temperature of activation. In particular, ZnCl2-to-shell ratios above 1 yielded high surface areas, and ratios above 2 resulted in high mesopore content. The adsorption capacity and nature of the porosity were investigated by adsorption experiments using adsorbates with different molecular sizes (viz., phenol, methylene blue and erythrosine red). The capacities of the mesoporous activated carbons were much higher than those of microporous carbons for larger adsorbates, confirming the presence of large amounts of mesopores in the former. The measured adsorption capacities for the prepared samples conformed to the expectations based on micropore and mesopore area and volume estimations. (C) 2001 Elsevier Science B.V. All rights reserved.