Adsorption of benzene, toluene, and o-xylene vapours on activated carbons prepared from water hyacinth activated by zinc chloride

Abstract

Water hyacinth, rice husk, and sugarcane bagasses were used as raw materials for the preparation of carbon adsorbent. They were carbonized and activated simultaneously with 600 grams/liter zinc chloride solution. The preparation process was carried out at the temperatures of 400, 500, and 600 C for 1, 2, and 3 hours. The yield of carbon adsorbent decreased with an increase in temperature. While the specific surface area, as well as iodine number and the average pore size varied directly with temperature. The activation period hardly affected the adsorbent characteristics. In comparison with carbonized materials, the yield was reduced by about 25%. For the water hyacinth, both the specific surface area and the iodine adsorption were improved by at least two-hundred fold and three-fold, respectively. Adsorption equilibria on carbon adsorbents from water hyacinth for dilute vapours of benzene, toluene, or o-xylene were measured by chromatographic method at the temperature of 180-270 C. The Increasing sequence of the equilibrium constants for those vapours on a given carbon adsorbent was benzene, toluene, and o-xylene. Heats of adsorption of BTX on all carbon adsorbents were about 72, 81, and 100 KJ/mol, respectively, In addition, the overall mass-transfer coefficients of all vapours obeyed Arrhenius’ Law.