Sequential Adsorption–Magnetic Separation Strategy for the Removal of Microplastics and Metal(loid)s

The presence of metals and microplastics in the water environment is a threat to the environment and human health. The development of analytical strategies to remove both pollutants simultaneously is very important. Iron-based adsorbents are environmentally friendly and have a high capacity to remove pollutants from the environment. In this work, Fe3O4 magnetic nanoparticles were applied to eliminate microplastic polyethylene from water and, because of the capacity of MPs to absorb metals, lead and arsenic were simultaneously removed in a single step. All experimental conditions were optimized to achieve the highest removal efficiency of the three pollutants. The optimal experimental parameters were 210 min of contact time at room temperature and pH 7 using Fe3O4 NPs as an adsorbent, achieving removal efficiencies of 98% of PE-MPs, 80% of Pb(II) and 96% of As(III). Although the adsorption steps occur sequentially—first the adsorption of Pb(II) and As(III) onto the surface of the PE-MPs, followed by the magnetic capture of the metal-loaded microplastics using Fe3O4 nanoparticles—the proposed methodology achieves the simultaneous removal of all three pollutants in a single magnetic separation step. The thermodynamics of the process were characterized, revealing a spontaneous Langmuir-type physisorption, and the adsorbents were characterized before and after the removal process by employing field-effect scanning electron microscopy and energy-dispersive X-ray spectroscopy.