Evaluation of CO2-induced azole-based switchable ionic liquid with hydrophobic/hydrophilic reversible transition as single solvent system for coupling lipid extraction and separation from wet microalgae

Abstract The utilization of microalgae as bioenergy source was limited by the excessive cost and energy consumption during the process of lipid extraction and separation. CO2-induced switchable ionic liquids (S-ILs) with reversible hydrophobic-hydrophilic conversion were synthesized and applied for lipid extraction and separation. The reversible transition mechanism of switchable IL is due to the formation of carbamate. The novel approach based on S-ILs was developed for lipid extraction from wet microalgae, which coupled microalgae cell disruption, lipid extraction, separation, and solvent recovery process without additional solvents. The highest lipid extraction efficiencies from wet microalgae were obtained by C6DIPA-Im, and the lipids were recovered from the extraction phase by simply bubbling CO2. Furthermore, C6DIPA-Im maintained more than 83.6±3.6% of its initial lipid extraction efficiency after recycling five times. The S-IL based extraction and separation method provides a new strategy for sustainable bioenergy production.