Alkaline Pulping and Bleaching of Acacia auriculiformis Grown in Bangladesh

Authors: M. SARWAR JAHAN, ROWSHAN SABINA, ARJUMAND RUBAIYAT

Abstract: The physical, chemical, and morphological characteristics of Acacia auriculiformis were evaluated in terms of its suitability for papermaking. The fiber length (1.1 mm) of A. auriculiformis in this study was within the range of tropical hardwoods. The lignin content in A. auriculiformis was 19.4% and \alpha-cellulose 44.1%, which was within the range of other acacias, but that of extractives was higher. Soda, soda-AQ, and kraft processes were studied in pulping. Screened pulp yield was increased with increasing active alkali. 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 strength properties than soda and kraft pulp. Soda, soda-AQ, and kraft pulps were bleached in DEpD and DEpDEpD (where D denotes Chlorine dioxide, E denotes peroxide reinforced alkaline extraction) bleaching in different kappa factors. In DEpD bleaching, kraft pulp showed better bleachability as compared to soda and soda-AQ pulp. However, in case of DEpDEpD bleaching, all pulps exhibited almost the same brightness. At the same kappa factor, final brightness of pulp increased from 72%-75% to 85%-86% with splitting DEpD and DEpDEpD sequences, respectively.

Keywords: Acacia auriculiformis, pulp yield, kappa number, strength properties, bleachability, viscosity

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