New algal lipid extraction procedure using an amphiphilic amine solvent and ionic liquid

Lipid extraction is a key step in microalgal biofuel production. However, economical microalgal biofuel production is limited by the high energy consumption of the extraction process. Therefore, in this study, we employed N-methylcyclohexylamine (MCHA) as a switchable solvent to directly extract a wet microalgal slurry, and an ionic liquid, [C4-mim][PF6] (1-butyl-3-methylimidazolium hexafluorophosphate), was used to recover the extracted algal oil through a simple phase separation method. CO2 was used to trigger the separation of MCHA from [C4-mim][PF6], and MCHA was regenerated by heating and purging with N2. Our extraction procedure differs from conventional solvent extraction, which requires drying algal slurries before extraction. The new extraction procedure adopted in this study can be used to extract wet algal slurries directly and recycle the solvent by using a low-energy consumption method. In addition, water-soluble MCHA was investigated for DHA(docosahexaenoic acid) wet algal slurries with 85% water content, and the extraction yield could reach 85% at low stirring speeds (200 rpm). Using [C4-mim][PF6] to separate algal oil from the crude extraction liquid, algal lipid recovery was approximately 77%. In summary, the results showed the feasibility of utilizing MCHA and [C4-mim][PF6] as extracting and separating agents, respectively, for algal oil exaction.