The effect of magnetic nanoparticles on Microcystis aeruginosa removal by a composite coagulant

A composite coagulant was prepared by magnetic nanoparticles and polyferric chloride (PFC) for Microcystis aeruginosa removal. The magnetic nanoparticles and composite coagulant were characterized in terms of typical properties, structure and morphological analysis (TEM, XRD and FTIR). The coagulation performances of magnetic nanoparticles/PFC (MPFC) and PFC were compared under different pH conditions and coagulant dosages. Natural water spiked with M. aeruginosa cells was also investigated to study the effect of natural organic matter (NOM) on the function of magnetic nanoparticles. The results show that the composite coagulant exhibits improved coagulation efficiency with higher removal values and slighter pH dependence. The better performance could be attributed to the co-effect of PFC and magnetic nanoparticles. The newly added magnetite acts as an adsorber, which favors the M. aeruginosa removal by facilitating the formation of settleable flocs and reducing the negative influence of NOM at optimal dosages. In addition, settling kinetic studies present accelerated settling velocity of MPFC under external magnetic field, emphasising the role plays by magnetic nanoparticles in promoting the coagulation efficiency.