Contribution of Lignin to Adsorption of Organic Liquids onto Wood

Abstract

The contribution of lignin to the adsorption of several kinds of organic liquids onto wood was studied in relation to the amount of residual lignin of the samples. Three alcohols of different molecular size and dimethyl sulfoxide (DMSO), which was suggested to have a strong affinity for dry lignin in the preceding paper, were used as organic liquids. Dry and preswollen samples prepared by gradual delignification from wood meal were used as adsorbents. The results obtained were as follows : as the delignification progressed, the amount of adsorption of ethanol onto dry samples decreased remarkably, while the amount of adsorption of methanol hardly decreased. This means that vacant pores and/or adsorption sites loosely hydrogen-bonded to each other (which were suggested to exist in dry lignin in the preceding paper) are accessible to liquids having similar molecular sizes as ethanol. The amount of alcohols adsorbed onto preswollen samples increased in the final stage of delignification. This suggests that lignin contributes restraint of swelling of cellulose and/or hemicellulose in wood. The adsorbed amount of DMSO decreases with progressive delignification not only on dry samples but also on preswollen samples. Therefore, it can be concluded that DMSO has stronger affinity for lignin than for cellulose and hemicellulose not only in the dry wood but also in the preswollen wood.