H2O2 bleaching of brown pulp with adsorbed xylan and its modifying effects on the mechanical properties of paper

Xylan is the primary hemicellulose in most hardwood species, especially in birch. Research has highlighted the exploitation of xylans as a strength-enhancing additive to paper due to the current trend for the effective utilization of biomass. In this paper, a new pulping process was proposed, which involved the extraction of xylan prior to pulping, followed by the re-adsorption of the pulp after the final stage in the digester, followed by a suitable bleaching process. The aim of this work was to bleach hardwood kraft pulp (brown pulp) with adsorbed birch xylan via hydrogen peroxide and study the effect of the bleaching parameters on the paper properties. The results showed that the optical properties of paper decreased; however, the mechanical properties increased after the brown pulp adsorbed birch xylan. During the bleaching process, better mechanical properties were obtained with shorter bleaching times and lower bleaching temperatures, initial pHs, and MgSO4 dosages. However, the optical properties were improved as the bleaching time, temperature, initial pH, and MgSO4 dosage were increased. The adsorption of birch xylan could effectively modify the mechanical properties of paper made from brown pulp under various phases.