Repeated Utilization of Ionic Liquid to Extract Lipid from Algal Biomass

Abstract

In this work, different kinds of ionic liquids and reaction conditions for the extraction of lipid from microalgae biomass were optimized and repeated use of ionic liquids for microalgal lipid extraction was evaluated. Morphological changes of microalgae cells were compared in terms of pre- and post-treatment to understand the mechanisms of ionic liquid treatment. Ionic liquid [BMIM][MeSO4] showed the best lipid extraction efficiency at 70°C and with reaction time of 2 hours. The ratios (ILs : methanol) of 1 : 7 and 1 : 3 were the optimum ratios to complete the extraction of the lipids from microalgae. The initial 50% volume fraction of [BMIM][MeSO4] was 16.04% of dry weight, which showed the highest five average extraction rates. The loss of ionic liquid in the reaction system and the increase in water content of ionic liquids were considered as the main reasons for the decrease in the extraction rate. It is suggested that the potential of lipid extraction in this IL-methanol co-solvent system is promising due to the high efficiency, low cost, safety, environmental protection, and other characteristics.