Magnetic Nanocomposite-Driven Harvesting of Chlorella vulgaris: Enhancing Microalgal Biomass Recovery Using Fe3O4 and Fe3O4@PEG Nanoparticles

This study investigates magnetic harvesting of Chlorella vulgaris cultivated under saline and wastewater conditions using Fe3O4 and polyethylene-glycol-coated Fe3O4 (Fe3O4@PEG) nanoparticles synthesized by ultrasound-assisted coprecipitation. TEM showed agglomerated, quasi-spherical particles with mean diameters of 13 ± 1 nm (Fe3O4) and 15 ± 1 nm (Fe3O4@PEG). FTIR confirmed the Fe–O vibrational bands of magnetite and the characteristic PEG vibrations in the coated sample. VSM measurements indicated superparamagnetic behavior, with saturation magnetizations of 72.74 emu/g for Fe3O4 and 32.25 emu/g for Fe3O4@PEG. SEM–EDX of native and functionalized cells verified nanoparticle attachment on the algal surface. Magnetic separation experiments (OD684) showed a decrease in supernatant absorbance with increasing nanoparticle dose, consistent with biomass removal; the PEG-coated system showed a lower apparent biomass concentration after functionalization.