Influences of extractives on absorption and desorption of many sorbents in two tropical woods

Abstract

Understanding the influence of extractives on water diffusion properties is crucial for optimizing drying processes and enhancing the performance of tropical wood species in various applications. This study investigates the hygroscopic behavior of two commercially valuable African tropical timbers, Tali (Erythrophleum suaveolens Brenan) and Bilinga (Nauclea diderrichii Merr.), focusing on the role of their extractive contents on water transport during absorption and desorption. Wood samples treated with six solvents and native wood were subjected to diffusion experiments at 30 °C and 82% relative humidity for five days. Applying the Fick diffusion law, an A polynomial type model best fitted the experimental data with significant variations observed in the average values of absorption, surface emission, diffusion, and diffusion resistance coefficients depending on the wood type and extractive content. Notably, the longitudinal direction exhibited greater moisture exchange compared to the tangential and radial directions. Moreover, water absorption, emission, and diffusion coefficients decreased with increase in wood density, while native and treated Bilinga woods displayed higher average values in all directions compared to Tali. Interestingly, the removal of extractives via acetone treatment enhanced water diffusion, highlighting the key role of specific extractive components. These findings provide valuable insights into the hygroscopic behavior of Tali and Bilinga, contributing to the development of efficient storage and improved utilization of these versatile tropical wood species.