The Effect of Heartwood Extraction on Kraft Pulp Properties of Acacia mangium and Acacia aulacocarpa Wood
Since heartwood parts generally contain higher levels of extractive, in this study, several extraction methods were carried out as a pre-treatment of Acacia mangium and Acacia aulacocarpa heartwood sawdust, followed by kraft pulping in a micro digester. After extraction, pulp properties from the two species were significantly different. Polar solvent extraction effectively increased pulp yield and decreased kappa number levels, while the successive extraction had less impact. Pulp kappa number significantly increased after n-hexane extraction. Compared to the control samples, pulp brightness of A. aulacocarpa wood for single solvent and successive extraction increased sharply. The overall pulp hexuronic acid content significantly decreased after extraction. Successive extraction led to significantly lower pulp viscosity compared to a single solvent extraction. In general, heartwood extraction significantly increased the pH values of A. aulacocarpa black liquor. Considering pulp properties, this study recommends hot-water extraction for A. mangium and successive extraction (n-hexane and methanol) for A. aulacocarpa