Relationship between Production Method and Adsorption Property of Char

Abstract

Charcoals were prepared from Japanese cypress (C. obtusa) and Japanese oak (Q. mongolica) by three carbonization methods, (a) in a nitrogen stream, (b) in an air stream, (c) in a container with cover . The relationship between the carbonization methods and the adsorption properties of the charcoals was investigated and the following results were obtained. Regardless of the carbonization method or the kind of wood used, the surface of charcoals prepared at low temperature was acidic and that of charcoals prepared at high temperature basic . The surface of charcoals prepared by method (c) showed the highest acidity. When benzene, iodine and phenol were adsorbed for short periods onto charcoals prepared by methods (a) and (c) , the charcoal prepared at 600ºC had the largest mean pore size, and also showed the fastest adsorption rate and the highest adsorption capacity. Of the charcoals prepared by method (b) , the charcoal prepared at 900•Ž had the highest adsorption capacity. The charcoal prepared at 1000ºC showed a decrease in adsorption capacity because of thermal shrinkage of the pores. For all methods, adsorption capacity for water vapor was lowest in the charcoal prepared at 600ºC . However, the amount of water vapor desorbed when humidity decreased was highest in the charcoal prepared at 600ºC . It was found that the 600ºC charcoal is the best for use in humidity-control .