Application of organic solvent nanofiltration for microalgae extract concentration

Microalgae lipids hold significant potential as a biofuel feedstock. The high-lipid content found in some species of microalgae is a major superiority over other sources. Furthermore, they have a high production rate record per area and survive in areas not already used for food production. This study considered the use of an integrated membrane process for oil extraction from microalgae. Different technologies were explored for laboratory-scale microalgae oil extraction, including the use of organic solvents, but they would require a further purification. Organic solvent nanofiltration (ONF) was employed for separation of solvent from oil: the solvent passed through the dense polymeric membrane while oil molecules were rejected by the membrane. Since different organic solvents were used in literature for oil extraction from microalgae, this study examined different oil-solvent mixtures and their separation by commercial hydrophobic and hydrophilic membranes. Experimental results showed that the new generation of ONF membranes has a superior performance compared to the previously used membranes. Based on rejection tests of oil in ethanol, isopropanol, and acetone, the applicability of the new commercial membranes for solvent recovery was demonstrated. Hydrophobic membranes had superior performances when oil was extracted using n-hexane as the solvent, whereas methanol miscella had the highest flux and rejection in hydrophilic membranes. Finally, the conventional and hybrid approach were simulated in Aspen. The approach including nanofiltration saves around 97% of the energy requirements for the separation. In terms of economic costs, the conventional alternative is slightly more convenient in a short-term situation.