Functional roles of magnetic iron oxide nanoparticles in mixed matrix membrane technology for wastewater treatment: a critical review

Abstract

Magnetic nanoparticles (MNPs) have emerged as highly promising functional additives in mixed-matrix membranes (MMMs) for advanced wastewater treatment. Their unique magnetic responsiveness, large surface area, tunable surface chemistry, and catalytic activity enable enhanced pollutant removal efficiency, membrane permeability, and antifouling performance. This review highlights the fundamental properties of common MNPs such as magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃). It discusses their incorporation into various polymeric membranes to target heavy metals, organic dyes, pharmaceuticals, and pathogens. The mechanisms governing pollutant separation, including adsorption, catalytic degradation, and magnetic-assisted separation, are examined in detail. Additionally, the effects of particle loading, surface modification, and dispersion techniques on membrane structural integrity and filtration performance are analyzed. Challenges such as nanoparticle leaching, stability under operational conditions, scaling-up synthesis, and environmental safety considerations are also evaluated. Finally, MNP-embedded MMMs offer a promising pathway toward efficient, selective, and energy-saving wastewater purification technologies.