Harvesting microalgae using ionic polyelectrolytes in an aqueous-organic two-phase system: Screening of separation parameters using model algal particles

Abstract

Abstract Separation and recovery of microalgae from the aqueous medium that they reside in is difficult as a result of the nature of the algal cells, i.e., small cell size, density close to water, low concentration, and ability to stay suspended in water due to surface potential. In this study, an easy technique that can separate microalgae from aqueous phase to a water-immiscible organic phase utilizing the natural zeta potential of microalgae is reported. The technique involves the addition of the positively charged electrolyte, Mono/Poly-(diallyl dimethyl ammonium chloride, DADMAC), which then interacts with the negatively charged biomass. The particle-bound electrolyte results in the formation of a hydrophobic ensemble which in turn migrates the particles from the aqueous phase to hydrophobic organic solvent phase. Approximately 80–85% of cellulose beads (model particles) and 80–82% of algae cells were displaced into hexane phase. Studies also indicated that the technique could be used to extract lipids without subjecting algal cells to disruption. The results pave the way for developing a low-cost method to dewater and separate whole algal cells by utilizing the inherent charges they carry. We anticipate the results being a starting point for the development of new separation technology targeting bioprocessing industry.