Magnetic Extraction of Microplastics from Environmental Samples

Separating microplastics (MPs) from environmental samples is challenging, but necessary to determine their environmental prevalence. Current methods are not standardized across environmental sample type, and it is unclear how well they recover smaller sized MPs. In response, we developed a method that extracts plastics magnetically, taking advantage of their hydrophobic surface to magnetize the plastics. We created hydrophobic Fe nanoparticles that bind to plastic, allowing magnetic recovery. With this principle applied to a simple method, we recovered 92% of 10-20 μm polyethylene and polystyrene beads and 93% of >1 mm MPs (polyethylene, polyethylene terephthalate, polystyrene, polyurethane, polyvinyl chloride, and polypropylene) from seawater. We also recovered 84% and 78% of MPs (polyethylene, polystyrene, polyurethane, polyvinyl chloride, and polypropylene) ranging from 200 μm to 1 mm from freshwater and sediments, respectively. Overall, the procedure is efficient for various sizes, polymer types, and sample matrices and can be considered by researchers to be included as a step of the extraction procedure for MPs (i.e., post density separation) or stand-alone for cleaner samples (i.e., drinking water).