Application and mechanisms of microalgae harvesting by magnetic nanoparticles (MNPs)

Magnetic harvesting of microalgae by magnetic nanoparticles (MNPs) depends on the interface interactions between microalgal cells and MNPs, therefore it’s important to understand these interface interactions. In this effort, we discussed the application and principles of microalgae magnetic harvesting via MNPs synthesized by the coprecipitation method. MNPs were capable of capturing Nannochloropsis maritima with a harvesting efficiency of 99.5% at a dosage of 0.33 g MNPs/g dry biomass, and the harvesting performance was less dependent on pH values in the range of 5.0–9.0. Treated with ultrasonic chloroform/methanol (2:1, v/v) solvent, the biomass was enriched and MNPs were reactivated and maintained ~60% harvesting effectiveness after 5 cycles. Regardless of the negative zeta potential for both MNPs and microalgae, MNPs-microalgae interactions were explained by surface-enhanced Raman spectroscopy (SERS) and extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory, and phospholipids over microalgal membrane were located as anchors for MNPs adhesion onto the microalgae. This work provided deeper insights into microalgae harvesting by MNPs and offered the powerful SERS technique for unlocking the door to MNPs-microalgae interface interactions.