Alkaline Pulping and Bleaching of Acacia auriculiformis Grown in Bangladesh

The physical, chemical, and morphological characteristics of Acacia auriculiformis were evaluated in terms of its suitabilityfor papermaking. The fiber length (1.1 mm) of A. auriculiformis in this study was within the range of tropical hardwoods. The lignincontent in A. auriculiformis was 19.4% and α-cellulose 44.1%, which was within the range of other acacias, but that of extractiveswas higher. Soda, soda-AQ, and kraft processes were studied in pulping. Screened pulp yield was increased with increasing activealkali. Acceptable pulp yield (43%-44%) and kappa number (22-24) were obtained at 20% alkali and 2.5 h of cooking in soda, 16%alkali and 2.5 h of cooking in soda-AQ, and 18% alkali in 2 h of cooking in kraft process. Soda-AQ pulp showed better strengthproperties than soda and kraft pulp. Soda, soda-AQ, and kraft pulps were bleached in DEpD and DEpDEpD (where D denotesChlorine dioxide, E denotes peroxide reinforced alkaline extraction) bleaching in different kappa factors. In DEpD bleaching, kraftpulp showed better bleachability as compared to soda and soda-AQ pulp. However, in case of DEpDEpD bleaching, all pulps exhibitedalmost the same brightness. At the same kappa factor, final brightness of pulp increased from 72%-75% to 85%-86% with splittingDEpD and DEpDEpD sequences, respectively.