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Abstract
The alkaline extraction of hemicelluloses from hardwoods prior to pulping, for further conversion to value-added products, seems to be a promising pathway for paper mills to increase profit and improve sustainability. However, the amount of hemicellulose extracted will be limited by the requirement to maintain pulp quality and pulp yield in comparison to existing pulping processes. The effects of NaOH concentration, temperature, and time on hemicellulose extraction of Eucalyptus grandis were studied using a statistical experimental design. Extracted wood chips were subjected to kraft pulping to evaluate the effect of the extraction on cooking chemicals, pulp quality, and handsheet paper strengths. The selective xylan recovery (12.4% dry mass) from E. grandis combined with low-cooking, active alkali charge, and less cooking time advantaged the xylan extraction and subsequent modified kraft pulping process under the studied conditions. Pulp viscosity, breaking strength, and tensile index of handsheets were slightly improved.
Acknowledgments
The research was supported by the South African National Energy Research Institute (SANERI), the Department of Science and Technology (DST), and the National Research Foundation (NRF). The authors are thankful to the South African pulp and paper suppliers Mondi Business Paper and Sappi Manufacturing Pty (Ltd.) for providing Eucalyptus grandis wood chips and to Mr. Jan Swart for technical assistance.