ADSORPTION BEHAVIOR OF WOOD CHARCOAL: SELECTIVITY OF TOLUENE FROM THE MIXED GAS WITH ALPHA-PINENE

摘要

The adsorption properties of wood, carbonized at various temperatures, were investigated by testing their ability to adsorb volatile organic compounds (VOCs). Wood (Japanese cypress) charcoal samples were prepared by heat treatment at various temperatures ranging from 500-1100°C and then exposed to a gaseous mixture of toluene and alpha-pinene at 20°C. Charcoal produced by heat treatment at 800-1100°C adsorbed both toluene and alpha-pinene, whereas charcoal produced at 500-700°C only adsorbed toluene. Analysis of the surface structure of the charcoal by nitrogen adsorption at liquid nitrogen temperature indicated that the test samples produced by 900 and 1100°C heat treatment had meso-pores and micro-pores more than 0.7 nm in diameter, whereas those produced by 700°C heat treatment had micro-pores mainly 0.6 nm in diameter and few meso-pores. Generation of the meso-pores is probably related to the adsorption capability for alpha-pinene. Since toluene molecules have a flat shape, they are probably adsorbed into the narrower sized, 0.6 nm pores, whereas the bulkier and more globular alpha-pinene molecules cannot be similarly adsorbed. This selective adsorption property is expected to be useful in selectively removing harmful VOCs from the living environment, leaving only pleasant aromas.