Development of a Fast and Efficient Strategy Based on Nanomagnetic Materials to Remove Polystyrene Spheres from the Aquatic Environment

Microplastics contamination is growing globally, being a risk for different environmental compartments including animals and humans. At present, some Spanish beaches and coasts have been affected by discharges of these pollutants, which have caused a serious environmental problem. Therefore, efficient strategies to remove microplastics (MPs) from environmental samples are needed. In this study, the application of three magnetic materials, namely iron oxide (Fe₃O₄) and the composites Fe₃O₄@Ag and Fe₃O₄@Ag@L-Cysteine, to remove MPs, specifically polystyrene (PS), from water samples has been assessed. The magnetic nanoparticles were synthesized and characterized by field effect scanning electron microscopy with energy dispersive X-ray spectroscopy detection (FESEM-EDX). Experimental conditions such as temperature, time, and pH during the removal process were assessed for the different adsorbent materials. The removal rate was calculated by filtering the treated water samples and counting the remaining MPs in the water using ImageJ software. The strongest removal efficiency (100%) was shown using Fe₃O₄@Ag@L-Cysteine for PS at 50 mg L^-1 within 15 min of the separation process at room temperature and a neutral pH. A thermodynamic study demonstrated that the developed MPs elimination strategy was a spontaneous and physisorption process. Coated Fe₃O₄ magnetic nanoparticles were demonstrated to be an efficient adsorbent for MP removal in aquatic environments and their use a promising technique for the control of MPs contamination.