Abstract
The diffusion rate of tritiated water into pine and aspen particles follows a Fickian mechanism. The tortuosity for the diffusion of water into wood is quite low, at approximately 1.6, and increases with decreasing particle size. The tortuosity for aspen is higher than that for pine because the shorter fiber structure in aspen gives rise to a more extensive network of pores. Diffusion into free and bound water occurs at the same rate. Also, diffusion into and out of the particles is nearly identical, demonstrating that diffusion of water into saturated wood particles is completely reversible. No hysteresis was evident, in contrast to behavior for water adsorption on unsaturated wood. The implications of these findings for pulping and wood drying are discussed.
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