Closing the loop on nanoplastic pollution: A 3D printed coral-like adsorbent enabling cyclic adsorption and ice-crystal catalytic degradation for waste minimization

Nanoplastics obtained from the decomposition of plastics have received extensive attention from researchers worldwide because of their wide distribution and potential hazards to human health. In this study, based on the bionic principle of coral predation mechanism, an efficient adsorbent with a three-dimensional bionic structure was proposed, and the degradation behaviour of polystyrene (PS) nanoparticles (≤500 nm) under extrusion at the interface between the adsorbent surface and ice crystals was investigated. The composite adsorbent with bionic coral structure (3DGPC) was prepared by combining the composite of polyethyleneimine (PEI) and carbon nanotubes (CNT) with graphene oxide (GO) in a certain ratio (PEI: CNT: GO = 1:2:4), which had an adsorption capacity of 199.66 mg/g and a capture efficiency of up to 96% for the nanoplastics in the water. The adsorption mechanism was investigated with the help of XPS and DFT calculations, and the adsorption process was dominated by electrostatic and chemical bonding interactions between nanoplastics and adsorbents. The presence of anions in the actual water also affects the capture efficiency of nanoplastics by 3DGPC due to the competitive adsorption effect. Under the simulated freezing conditions in the extreme cold zone, the reactive oxygen species generated during the extrusion and squeezing of nanoplastics at the interface between the surface of the 3DGPC material and ice crystals can further promote the degradation of nanoplastics, and the adsorbent still maintains more than 80% of adsorption efficiency after five freeze-thaw cycles, and the degradation-regeneration at the interface of the ice crystals maintains the adsorption capacity of the material. Therefore, this study combines bionic structures with 3D printing and applies it for the first time to a special scenario of synergistic degradation of nanoplastics at the ice crystal interface.