Insights into the dissolution of cellulose in lithium bromide solution

Abstract

Lithium bromide molten salt hydrate (∼62 wt% aqueous solution of LiBr) can dissolve cellulose, but the cellulose dissolution mechanisms are not fully understood. This study revisited cellulose dissolution in the LiBr solution and aimed to provide new insights into the dissolution mechanisms. The collected evidence suggested that cellulose dissolution in the LiBr solution is primarily attributed to the disruption of intermolecular H-bonds of cellulose by the ion-dipole coordination between hydrated Li+ and cellulose hydroxy. The coordination between Li+ and cellulose was verified by 7Li NMR and simultaneous DSC-TGA analysis. The observations in this study also suggest that polarizable, large-size, and low-electronegativity Br– plays a synergetic and supplementary role in the dissolution of cellulose. In addition, the dissolution of cellulose in the LiBr solution is greatly dependent on dissolution conditions (LiBr concentration, temperature, pH, and cellulose loading) and cellulose properties (particle size and degree of polymerization).

Keywords

• Cellulose hydrophilicity
• Concentrated salt solution
• Hydrogen bond
• Ion-dipole coordination
• Molten salt hydrate