The Effect of Oxidative Bleaching Using Chlorine Oxoacid Agents on the Characteristics of Cellulose Fibers and Hydrogel Films of Sugarcane Bagasse

Cellulose hydrogels have outstanding research and application prospects in biomedical and agricultural fields. In this study, sugarcane bagasse waste was converted to physical cellulose hydrogels through the phase inversion gelation process, and the effects of the oxoacid bleaching process using NaClO, NaClO₂, and NaClO₃ on the properties of both fiber and hydrogel were evaluated in terms of their bleaching behavior and the properties of extracted cellulose in fibrous and hydrogel states. Under acidic conditions, each bleaching agent acted as an oxidant, resulting in a bleaching reaction of the cellulose bagasse. NaClO quickly produced ClO⁻, effectively removing lignin and yielding white cellulose fiber. However, this process led to the degradation of cellulose molecules, resulting in a significant decrease in molecular weight. NaClO₂ generated ClO₂ within the first 30 min, effectively bleaching cellulose without causing degradation. In contrast, brown components remained in the cellulose fibers by NaClO₃ bleaching. These purified celluloses were then dissolved in DMAc/LiCl solution to produce transparent hydrogels. However, the hydrogels from the NaClO₃ exhibit a brown in color. The resulting hydrogels exhibited flexibility like viscoelastic properties and maintained high water contents. However, the cellulose hydrogels obtained with NaClO treatment had weak gel strength with the highest water retention.