Efficient and stable extraction of nano-sized plastic particles enabled by bio-inspired magnetic "robots" in water

In this research, a rationally-designed strategy was employed to address the crucial issue of removing nano-plastics (NPs) from aquatic environments, which was based on fabricating sea urchin-like structures of Fe₃O₄ magnetic robots (MagRobots). Through imitating the sea urchin's telescopic tube foot movement and predation mechanism, the unique structures of the MagRobots were designed to adapt to the size and surface interactions of NPs, leading to a high efficiency of NPs removal (99%), as evidenced by the superior performance of 594.3 mg/g for the removal of polystyrene (PS) nanoparticles from water, with 3300% increase over magnetic Fe₃O₄ without structural design. The adsorption process was further analyzed using density functional theory (DFT) models and adsorption experiments, indicating that it was driven by electrostatic interactions. MagRobots maintained an adsorption capacity of up to 328 mg/g over four cyclic experiments and demonstrated high-capacity adsorption (close to 400 mg/g) in natural water bodies. The results of the simulations were supported by experiments that verified the excellent adsorption performance, regeneration effect, and environmental stability of the MagRobots under both simulated and real-world water conditions. This ingenious structural strategy provided valuable perspectives for the development of efficient magnetic porous materials for wastewater treatment, which would have potential applications for the treatment of NPs in real aquatic ecosystems. The unique sea urchin-like structures of the MagRobots could offer an innovative approach to tackle the challenge of NPs removal.