An efficient strategy to separate nanoplastics from water using anisotropic magnetic Janus particles

Nanoplastics (NPs) are emerging contaminants that threaten drinking water safety, and their selective removal remains challenging. Herein, amphiphilic magnetic Janus particles (MJPs) were synthesized to capture NPs from water, achieving high NP capture capacities (10.3-19.2 mg/g) approximately 4-7 times greater than those of previously reported materials. Hydrophobic interactions strongly drove NP capture, enabling MJPs to retain 80 % of their efficiency for selective NP removal, even in the presence of competing contaminants. Crucially, NP capture is governed by the confinement effect induced by the unique asymmetric structure of MJPs. Their negatively curved hydrophobic surface significantly enhances the interfacial activity and adsorption energy, resulting in a hydrophobic affinity that surpasses that of even more hydrophobic materials with positively curved surfaces. The applicability of MJPs was further evaluated for various NP types and verified in NP-contaminated drinking water, demonstrating their strong potential for capturing diverse NPs under real-water conditions. These findings highlight MJPs as an effective and novel solution for NP removal in water purification.