Hemicelluloses extraction from giant bamboo (<i>Bambusa balcooa</i> Roxburgh) prior to kraft or soda-AQ pulping and its effect on pulp physical properties

Abstract

Abstract The alkaline and acid preextraction of giant bamboo ( Bambusa balcooa Roxburgh), grown in South Africa, before kraft and soda-anthraquinone (AQ) pulping was in focus and the effects of NaOH concentration, temperature, and time on hemicelluloses extraction were studied by means of a statistical experimental design. The NaOH concentration exerted the strongest influence, solubilizing up to 20.4% of the available xylan with 2.0 M NaOH at 90°C for 240 min. The optimal extraction condition was achieved with 1 M NaOH at 90°C for 240 min, in the course of which 13.6% of the xylan was removed; the screened pulp yield was 50.4% without viscosity reduction, whereas the burst index of the handsheets was even improved. In the case of dilute acid preextraction before soda-AQ pulping, 11.3% xylan could be removed without affecting the pulp quality. The viscosity of the pulp was even better than that of pulps from nonextracted bamboo. The biorefinery approach, alkaline preextraction in combination with kraft pulping, is superior to the approach, acid prehydrolysis/soda-AQ pulping.