ADSORPTION OF LIQUIDS AND SWELLING OF WOOD-III - ADSORPTION OF SOME ORGANIC LIQUIDS ONTO DRIED WOOD

The adsorption of four kinds of organic liquids onto dried wood, in wh ich the hydrogen bonds between the molecules of wood constituents are cut prior to the adsorption of the liquids, from their dilute benzene solutions were studied thermodynamically. Standard free energy changes of adsorption (Delta F degrees) as a thermodynamic measure of adsorpt ivity were determined by means of Langmuir's adsorption theory. For ac etone-benzene, ethyl acetate-benzene. and propanol-benzene systems, De lta F degrees values for dried wood were smaller than those for preswo llen wood. Furthermore, the difference between Delta F degrees values for dried wood and those for preswollen wood become greater with incre asing molecular size (Figs. 1 and 2). These results mean that greater energy is necessary to cut the hydrogen bonds between the molecules of wood constituents than to desorb adsorbent molecules and for larger m olecules to penetrate into the cell walls of wood. However, for the me thanol-benzene system, the Delta F degrees value was greater for dried wood than for preswollen wood (Fig. 1). This result is attributable t o the fact that methanol is adsorbed more easily onto the sites free o f hydrogen bonds and/or the sites loosely hydrogen bonded to each othe r in the cell walls of wood because molecular size of methanol is smal ler than the other organic liquids, It is well-known that liquids havi ng large molecular sizes tend to swell wood to a less extent; however, this mechanism is not known yet. The mechanism was clarified thermody namically in this study.