Engineering a chitosan-encapsulated PDA/Fe3O4@cenosphere composite for dual adsorption of microplastics and organic dyes

Microplastics and dye pollutants threaten aquatic ecosystems and human health, prompting the need for sustainable solutions. Converting industrial solid waste into value-added adsorbents provides an effective remediation pathway. In this work, industrial solid waste—fly ash cenospheres—was transformed into a value-added adsorbent (PMFL) by coating with polydopamine (PDA) and Fe 3 O 4 , imparting magnetic recoverability and high adsorption capacity for polystyrene (PS) microplastics (312.00 mg/g). To further improve practical applicability and broaden pollutant removal capacity, PMFL was immobilized within a chitosan matrix to form a monolithic CS@PMFL composite. This structure not only enables facile recovery but also exhibits strong adsorption affinity toward both PS microplastics and Congo red dye. Mechanistic investigations indicated that adsorption involved a combination of electrostatic, chemical, and physical interactions, including π–π stacking, hydrogen bonding, hydrophobic effects, surface complexation and physical entrapment. The materials maintained high adsorption performance across a wide range of pH and ionic conditions, demonstrating robust environmental adaptability. Overall, this study presents a scalable approach for converting industrial waste into multifunctional adsorbents capable of simultaneously removing diverse pollutants.