Disruption and Wet Extraction of the Microalgae <i>Chlorella vulgaris</i> Using Room-Temperature Ionic Liquids

Abstract

Recently, ionic liquids have been demonstrated to increase the efficiency of solvent extraction of lipids from microalgae. However, to date, mostly imidazolium-based ionic liquids have been investigated. This report extends the range of cations studied to over 30, including imidazolium, ammonium, phosphonium, and pyridinium derivatives, which were screened for their ability to increase hexane extraction efficiency of lipids from freeze-dried microalgae Chlorella vulgaris at ambient temperature. Promising ionic liquids were first identified using gravimetric analysis of total extractable oils. Oils extracted after ionic liquid pretreatment were further characterized with respect to fatty acid methyl ester (FAME) equal to biodiesel yield, FAME composition, and chlorophyll content. With few exceptions, all of the tested ionic liquids had lower chlorophyll content than standard solvent extraction techniques. The effect of process parameters such as mass ratio of algae to ionic liquid, incubation time, water content, and cosolvents were investigated for 1-ethyl-3-methylimidazolium ethylsulfate [C 2 mim][EtSO 4 ]. The results indicate that this ionic liquid can disrupt C. vulgaris in conjunction with methanol and allow facile recovery of lipids over a large degree of dewatered microalgae (0–82 wt % water), in a small amount of time (75 min) at room temperature, resulting in the development of a low energy, water compatible, biodiesel production scheme.