Gas-assisted low-field magnetic separation for efficient recovery of contaminants-loaded magnetic nanoparticles from large volume water solution

Abstract Gas-assisted low-field magnetic separation (GAMS) was proposed for efficient recovery of contaminants-loaded magnetic nanoparticles from the large volume of water solution. Pb2+ loaded magnetic nanoparticles (Fe3O4/HA) were selected as separation model of GAMS. It was demonstrated under the condition of no surfactant as flotation agent that bubbles could overcome the limitation of magnetic force on the capture distance and improve significantly the separation efficiency in low-field magnetic separation (MS). The greater improvement could be further obtained by adjusting some nonmagnetic factors such as gas flow rate, ionic strength, pH, and heavy metals loading amount. The enhancement mechanism of some factors on GAMS was disclosed by the electrostatic forces and hydrophobic forces, which was characterized by Zeta potential and contact angle. Compared with MS, GAMS had the advantages of good distant recovery, improved separation efficiency by nonmagnetic factors, low cost and high separation performance for diluted nanoparticles solution (about 10 times rate of MS).