Regeneration of deep eutectic solvent post biomass delignification

In recent years, lignocellulosic biomass has emerged as a promising renewable resource, offering potential to reduce reliance on fossil fuels. Comprised of cellulose, hemicellulose, and lignin, it requires complex separation techniques for value-added fractionation. Lignin, a byproduct of the pulp and paper industry, is of particular interest for its potential to be converted into high-value chemicals. However, traditional methods, like the Kraft process, limit lignin's value due to sulfur content and repolymerization, driving research into alternative solvents, including deep eutectic solvents (DESs).

Chapter 1 introduces the potential of DESs, alongside other green solvents such as ionic liquids and organic acids, in the delignification process. DESs, particularly lactic acid-choline chloride mixtures, show promise in lignin and hemicellulose removal while offering energy-saving benefits during regeneration. The thesis focuses on two strategies for DES regeneration: liquid-liquid extraction (LLX) and membrane-based methods. Chapters 2-4 investigate LLX with solvents like 2-MTHF and guaiacol, while Chapters 5-6 explore membrane-based ultrafiltration processes. The study demonstrates the efficacy of these methods in recovering lignin and furanic compounds, with solvent and energy considerations for industrial applications. Lastly, Chapter 7 provides energy usage calculations, comparing the regeneration methods. Guaiacol-based LLX emerged as a more energy-efficient option compared to 2-MTHF, while membrane processes also showed promise for lignin recovery.