Lignin enhances cellulose dissolution in cold alkali.

Area of Science:

• Biomass processing
• Polymer chemistry
• Materials science

Background:

• Aqueous sodium hydroxide (NaOH) is a common solvent for lignin in kraft pulping.
• NaOH is also used for cellulose dissolution due to cost, recyclability, and low toxicity.
• Cellulose dissolution in NaOH is limited to narrow concentration ranges and low temperatures, often yielding incomplete dissolution.

Purpose of the Study:

• To investigate lignin as a potential additive to improve cellulose dissolution in aqueous sodium hydroxide.
• To characterize the effect of lignin on the dissolution process and the properties of regenerated cellulose.

Main Methods:

• Exploration of lignin as an additive in cold alkaline cellulose dissolution.
• Comparison of cellulose dissolution in neat NaOH, NaOH-urea, and NaOH-lignin systems.
• Characterization of regenerated cellulose crystallinity and crystallite size.

Main Results:

• Lignin was found to improve cellulose dissolution in cold alkali.
• Lignin extended the effective NaOH concentration range for dissolution to lower values.
• Regenerated cellulose from NaOH-lignin solvents showed lower crystallinity and crystallite size compared to neat NaOH and NaOH-urea systems.

Conclusions:

• Lignin acts as a beneficial additive for cellulose dissolution in cold alkaline media.
• Lignin-cellulose interactions in solution are preserved during regeneration, suppressing cellulose crystallization.
• This finding opens new avenues for biomass processing and cellulose modification.