Sedimentation-induced detachment of magnetite nanoparticles from microalgal flocs.

•Sedimentation through dense/viscous solution removes nanoparticles from flocs.•Effectiveness of separation is increased with higher solution density and viscosity.•Centrifugal and magnetic sedimentation effectively remove nanoparticles from flocs.•The approach did not show cytotoxicity.•The mechanism of sedimentation-induced removal is discussed.