(364b) Cellulose Dissolution and Regeneration in Calcium Bromide Solution

Cellulose is the most abundant natural polymer in the world. As a promising material, it offers advantages including renewability, biodegradability, biocompatibility, barrier properties, attractive appearance, non-toxicity, and low cost. Efficiently converting this renewable resource into value-added products, such as regenerated cellulose materials and cellulose derivatives, requires the critical step of cellulose dissolution. Inorganic molten salt hydrates, such as lithium bromide (LiBr), zinc bromide (ZnBr₂), zinc chloride (ZnCl₂), and calcium bromide (CaBr₂) solutions, have drawn increasing attention as a new category of cellulose solvents. This study provides a systematic investigation into cellulose dissolution by CaBr₂ solutions. The cellulose dissolution by CaBr₂ is a process of disassembling the strong matrix of cellulose chains assembled via intermolecular hydrogen bonding (H-bonds) and hydrophobic stacking. Parameters influencing the dissolution of microcrystalline cellulose (MCC), including CaBr₂ concentration, MCC concentration, temperature, and time, were investigated. The results showed that 2% MCC can be dissolved within 15 min by 58% CaBr₂ at 100 ℃, without hydrolysis of cellulose to glucose or further conversion to 5-hydroxymethylfurfural. Additionally, this study prepared cellulose aerogels via a process of dissolution and regeneration. The cellulose aerogels had high porosity, low density, and strong matrix properties, making them potentially useful in adsorption, oil/water separation, thermal insulation, and biomedical applications, among other fields. Overall, this study provides a systematic investigation into cellulose dissolution by CaBr₂ solutions and has important implications for the development of new processes to produce cellulose-based materials with a broad range of applications.