Self-aggregation separation of microplastics from water induced by topological cationic organogels

This work reveals a novel functionality and mechanism for the electric field-induced self-aggregation separation of microplastics from water, mediated by a topological cationic organogel. Nine self-synthesized topological cationic organogels were adopted as model probe materials, and analysis of their structure–activity relationships revealed that the densely secondary-crosslinked poly(amine salt) gel (PMASG) exhibited a superior treatment capacity of 2426.80 mg/g for polystyrene microplastics (PS-MPs), significantly outperforming most reported analogous materials. Furthermore, PMASG maintained a stable treatment performance in different water environments and for various types of other microplastics (PET, PVC, PTFE), and achieved efficient removal in ultra-dilute systems with microplastic concentrations as low as 0.01 mg/L, demonstrating excellent practical application potential. Thermogravimetric analysis indicated that the post-treatment residue can be completely thermally degraded under an inert atmosphere and possesses favorable combustion characteristics in air (ignition temperature: 328.96 °C, burnout temperature: 761.9 °C, comprehensive combustion characteristic index: 3.39 × 10 −5 ), enabling the elimination of post-treatment solid waste and achieving a green cycle for valorization. Based on kinetic/thermodynamic behavior studies and multi-spectroscopic micro/mesoscopic structural evolution analysis, a novel localized electrostatic-induced nucleation-driven self-aggregation (LEIN-SA) mechanism was established. In this mechanism, the topological cationic network of PMASG generates a localized electrostatic field that destabilizes and captures nearby microplastics, leading to the formation of a critical PMASG–PS composite cluster (nucleus). and subsequently driving the rapid aggregation of microplastics in water. In summary, this study develops a new strategy for water microplastic pollution remediation that combines ultra-high efficiency and total environmental friendliness.