Interpretation of the disparity in harvesting efficiency of different types of Microcystis aeruginosa using polyethylenimine (PEI)-coated magnetic nanoparticles

Heteroaggregation between magnetic nanoparticles (MNPs) and cells is a crucial precondition for the harvesting and separation of algae from the aquatic environment. However, separation mechanisms have not been fully elaborated in previous studies, especially regarding cyanobacteria coated with extracellular polymeric substances (EPS). The present study was conducted to investigate the interaction between PEI-coated iron-oxide nanoparticles (IONPs) and M. aeruginosa as a function of cell type (FACHB-1343 and FACHB-905) and cells with/without extracellular polymeric substances (EPS). The results demonstrated that harvesting efficiency (HE) varied with the different cell types with/without EPS surrounding the cyanobacteria. The PEI-coated IONPs showed higher HE for M9 than for M1 with the same mass ratio of NPs/cyanobacteria. Furthermore, EPS significantly affected the HE because of their heterogeneous composition, which was interpreted by spectral analysis and the DLVO theory. Overall, this study provides guidance on cyanobacteria harvesting with different environmental conditions when employing magnetic separation technology.