Separation experiment and mechanism study on PVC microplastics removal from aqueous solutions using high-gradient magnetic filter

Abstract

Microplastics have posed a threat to organisms and human health in the water environment. Seeking environmentally friendly and efficient method to remove microplastics from aqueous solution has garnered research interest. We studied the magnetic separation method of microplastics using a magnetic filter, and discussed the removal mechanism in the coupled field including the flow and magnetic fields. The results show that the Fe3O4 magnetic medium carrier can effectively combine and wrap itself onto the surface of microplastic particles (polyvinyl chloride, PVC) to form high strength magnetic aggregates, with strong magnetic characteristics. The designed magnetic filter has a high intensity magnetic field strength of 4–8 T near the magnetic matrices, and also has a stable separation flow field. The magnetic aggregates were firmly captured on the magnetic matrices to realize the effective separation of magnetic aggregates from the aqueous solution. The removal efficiency increased gradually and reached 100 % with the increase of reaction time. Furthermore, the Fe3O4 magnetic medium carrier was recovered by a tubular furnace and recycled experiments were subsequently conducted. The PVC removal rate after five cycles reduced due to the mass loss, but could still be maintained above 94 %. In this study, the easily prepared Fe3O4 was selected as the magnetic medium carrier and applied to the magnetic separation method to remove the microplastics in the aqueous solution, and was efficient, economically feasible, and environmentally friendly.