THE INTERACTION OF WOOD PRESERVATIVES WITH LIGNOCELLULOSIC SUBSTRATES .1. QUATERNARY AMMONIUM-COMPOUNDS

The effect of solution pH on adsorption of a quaternary ammonium compound, didecyldimethylammonium chloride (DDAC), onto cellulose, softwood lignin, and softwood wood meal has been studied. Adsorption was found to be predominantly onto lignin with much lower adsorption onto cellulose. In general, adsorption was much greater at high pH from ammoniacal solutions than from neutral or acidic solutions. pH effect was more apparent with liginin adsorption than in the case of cellulose. The results suggest that cation exchange with carboxyl and phenolic hydroxyl groups may be the dominant mechanism for DDAC adsorption onto lignin, while other factors, such as electrostatic effects, may also play an important role in DDAC adsorption onto cellulose. The implications of high adsorption onto lignin with respect to observed performance of quaternary ammonium-only treated wood in field tests are discussed.