Fe3O4 nanoparticles anchored 3D printed halloysite nanoclay porous ceramics for high-efficient removal of microplastics

Microplastic pollution has become a global environmental problem that urgently requiring efficient and recyclable remediation technologies. Herein, direct ink writing (DIW) 3D printing technique was used to construct halloysite clay-based porous ceramics scaffolds (PCS) with a pore-forming agent of polymethylmethacrylate (PMMA) microparticles in ~20 μm. Fe 3 O 4 nanoparticles in ~200 nm is then grown on the PCS surface to prepare Fe 3 O 4 @PCS ceramics to increase the interfacial interactions between the PCS and the nanoscale polystyrene (PS) microplastics. The rheological properties and printability of the halloysite composite ink are investigated, and then the synergistic construction of the multi-scale porous structure is achieved. In a dynamic circulation apparatus, Fe 3 O 4 @PCS can reach a maximum equilibrium adsorption capacity of 18.7 mg/g for 100 mg/L nanoscale PS microplastics at 298 K, with a removal efficiency of 98.7%. The dynamic adsorption process conforms to pseudo-second-order kinetics and the Sips isotherm model, suggesting the heterogeneous multilayer adsorption process with intraparticle diffusion. In complex matrices such as lake water, seawater, cation-interfered water, and simulated organic and biological wastewater, Fe 3 O 4 @PCS maintains a removal efficiency of ~93%. After 10 adsorption-thermal degradation cycles, the nanoscale PS microplastic removal efficiency by Fe 3 O 4 @PCS is higher than 90%, which is superior to most reported adsorbents. This work provides a natural clay based porous materials for efficient, tailorable, and sustainable remediation of nanoscale PS microplastics in aquatic environments.