Interaction energy and detachment of magnetic nanoparticles-algae.

Magnetic separation, a promising bioseparation technology, is confronted with the challenges in recovery and recycle of magnetic matters during algae harvesting for biofuel extraction. The thermodynamic method was used to characterize the surface interactions between MNPs and algae cells. Three methods were adopted to detach magnetic nanoparticles-algae (Microcystis aeruginosa, Synechocystis sp., Nannochloropsis maritima and Stigeoclonium sp.) and recover magnetic nanoparticles (MNPs) in this study. The thermodynamic method indicated that the greatest adhesion strength was expected for Stigeoclonium sp. on MNPs. High detachment efficiency of MNP-algae was achieved by ultrasonic-extracting, which got above 90% after 5 recycles. Moreover, the harvesting efficiencies of these four algae cells could remain more than 90% after 5 recycles using a mixture of the regenerated and the raw MNPs.