Buoy-bead flotation application for the harvesting of microalgae and mechanistic analysis of significant factors

Harvesting technology has a significant influence on the microalgal biomass industry. This study develops a buoy-bead flotation method and analyzes the factors impacting flotation. Experimental results show that adding sodium borosilicate as an alternative microsphere material can result in 58.5% harvesting efficiency, a 25.65% increase over the foam flotation average. The Plackett–Burman design experimental results reveal that pH conditions, microsphere diameter, and the speed of agitation are the three most important factors affecting harvesting efficiency. The interaction between these three factors was all found to be significant, which indicates that the harvesting efficiency was affected by a combination of multiple factors. Analyses of the Extended Derjaguin–Landau–Vewey–Overbeek (XDLVO) theory show that the Van der Waals interactions are the key factor in the attachment of algae and microspheres. A harvesting efficiency of 89.9% can be achieved at pH 10, with 56 µm dimeter microspheres and an agitation speed of 114 rpm.