Adsorptive removal of micron-sized polystyrene particles using magnetic iron oxide nanoparticles

Microplastics are able to pass through many filtration systems due to their small sizes, making it difficult to remove them from, for example, water. In this study, we evaluated the ability of using magnetic iron oxide (Fe₃O₄) nanoparticles to achieve the adsorptive removal of micron-sized polystyrene (microPS) particles. Application of a magnet for 3 min to an aqueous sample of microPS particles mixed with iron oxide nanoparticles for 1 min was able to effectively remove the microPS particles from the water. Transmission electron microscopy images of such samples showed the formation of Fe₃O₄-PS complexes due to the adsorption of PS particles onto iron oxide nanoparticles. This adsorption followed the pseudo-first order kinetic and Langmuir isotherm model. Hydrophobic interactions were concluded from our experiments to be the main interactions involved in the aggregation of iron oxide with PS particles. Ions present in an environmental freshwater sample inhibited the ability of iron oxide particles to become adsorbed PS particles, but the adsorption performance was improved by increasing the amount of iron oxide particles. The iron oxide particles could be recovered from the Fe₃O₄-PS complexes by desorption process. Our study showed the potential advantages of iron oxide particles for removing environmental pollutants of microplastics via highly efficient and environmental-friendly procedure.