Sorption and diffusion properties of untreated and thermally modified beech wood dust

Abstract

Dynamic water vapor sorption experiments were carried out using beech wood dust (from untreated and thermally modified wood) of two-particle sizes, (< 25 and 80–250 µm), obtained from abrasive sanding. Sorption isotherms were parameterized with the GAB and GDW models. Dust from thermally modified wood had significantly lower equilibrium moisture content compared to dust from untreated material, due to the reduction in primary sorption sites in treated material. The observed changes were quantified by the coefficients of the GAB and GDW models. Thermal modification and size of wood dust particles had no influence on binding energy of water molecules being linked to the secondary sorption sites. Water diffusivity decreased significantly with increasing moisture content, but only for monolayer sorption. For higher moisture content values, water diffusivity was practically independent of moisture content. These results were found for untreated and thermally modified material as well as for both dust size fractions. The influence of thermal modification on water diffusivity was unclear, which is attributed to the diffusion model, which represents dust particles as spheres and assumes instant hygroscopic equilibrium. Overall, this study indicates that the effectiveness of filtration processes likely depends strongly on sorption and diffusion properties of wood dust only at low moisture contents within the hygroscopic range.

Anisotropic wood–water interactions determined by gravimetric vapor sorption experiments

“…The diffusivity tends to decrease upon increasing the RH in the adsorption process and, vice versa in the desorption process. This behavior has previously been reported with values for the diffusion coefficient that decrease from 0.88 × 10 −10 to 0.06 × 10 −10 m 2 /s when increasing the RH from 5 to 80% RH (Majka et al 2022), and similar to other published results obtained from different methods (Olek et al 2005;Simo-Tagne et al 2016;Gezici-Koç et al 2017).…”

Evaluation of Environmental Impact on Selected Properties of Lime (Tilia Cordata Mill.) Wood

“…The fitting results for all the sets of the wood samples are presented in Table 7. The sorption experiments' results presented in Figure 5 generally support earlier conclusions that hygroscopic properties of juvenile and mature lime wood differ [22]. The lowest differentiation of hygroscopic properties regards the juvenile and mature wood tissue of the tree growing under low stress conditions (A), i.e., in the forest (see Figure 5a).…”

“…It was also determined that the amount of energy involved in the sorption process is greater in the mature wood than in the juvenile wood. Majka and Olek [22] stated the sorption isotherms at 25 • C for the successive phases (i.e., initial desorption, adsorption and second desorption), sorption hysteresis and the fiber saturation point (FSP) of mature and juvenile lime (Tilia sp.) wood.…”