Effects of pretreatment on the recycling properties of birch holocellulose paper.

Holocellulose fibers exhibit excellent recycling performance and are increasingly gaining attention for addressing the hornification effect that occurs during the recycling of waste paper products. However, the mechanism by which hemicellulose components in holocellulose fibers impact fiber reuse remains unknown. In this study, birch holocellulose was prepared through peracetic acid delignification. The hemicellulose content was adjusted using alkali treatment and xylanase treatment, both based on holocellulose. The removal of hemicellulose resulted in an increase in hornification and porosity growth rate during the recycling process due to these pretreatments. Consequently, fibers subjected to alkali treatment and xylanase treatment exhibited diminished mechanical performance with each recycling cycle. In particular, after five recycling runs, alkali treatment paper experienced a significant reduction in ultimate strength, dropping from 48 to 11 MPa, representing a 77% decrease. In contrast, hemicellulose-rich holocellulose paper retained an ultimate strength as high as 56 MPa (reduced from 81 MPa), marking a 33% decrease. The high hemicellulose content in holocellulose fibers proved advantageous for preserving the network structure of fibers and impeding the co-crystallization and aggregation of fibers during the recycling process, ultimately ensuring the maintenance of mechanical performance, including tensile, tearing, and bursting strength. [ABSTRACT FROM AUTHOR]