Application of soda-AQ pulping to agricultural waste (okra stalks) from Sudan

Abstract

Abelmoschus esculentus okra as whole stalks was examined for its suitability for pulp and paper production. It’s, fiber dimensions, morphological and chemical characteristics were reported. The pulping trials with soda- Anthraquinone (AQ,) at different chemical charges. Application of 21% as NaOH with 0.1% AQ gave good results in degree of delignification, mechanical properties. Utilization of okra pulps and blender is recommended due to good pulp properties. Evaluation of general characteristics of okra stalks in terms of fiber dimensions morphological indices, chemical components, Soda-AQ cooking and to study their suitability for paper production. Okra Fiber dimension evaluation done after maceration with a mixture of 30% hydrogen peroxide and acetic acid (1:1) for core and bark parts separately and was carried out under microscope staining with aqueous safranin. The Soda-AQ cooks at different active alkali levels were calculated as NaOH on oven dry raw material. The fibers from okra stalks studied (core and bark) were in the range of hardwood fibers, with short fiber length, especially the core with more or less moderate walls, narrow lumen and fiber width. The fiber width of bark was medium –narrow with medium wall thickness. The ash content was rather high whereas the silica content was comparatively high The hot water extractives from okra stalks was (4.1%), cold water (0.4) ethanol/ cyclohexane (1.1), ethanol extractives (1.2%) and 1% NaOH (27.6%) were rather high. The cellulose (Kurschner-Hoffer) was (48.5%) The lignin content was (15.3%) which was relatively moderate. The use of 0.1% AQ enhanced the delignification in the three trials applied. The screened yield increase with increase of chemical dose applied while the rejects decrease. When 21% NaOH was applied, the screened yield was 32.2% with negligible amount of rejects, however with lower alkali charge 18% the screened yield was decreased to 28% with very low rejects 1.5%. on the other hand rejects were increased to 7% when 15% NaOH was applied with very low screened yield 19%.The pulps produced from okra soda-AQ are suitable for production of printing and writing papers and it is advisable to use them in blending due to good papermaking properties.