Imprinted Polymers Embedding Fe(III) Complexes for Dye Pollutant Removal: Toward Green and Efficient Wastewater Remediation

Dye pollutants from textile and related industries are highly recalcitrant, posing significant environmental and health risks. In this study, we evaluate a family of Fe(III) complexes and their corresponding molecularly imprinted polymers (MIPs) as efficient, green catalysts for the oxidative degradation of representative dyes: methyl orange, methylene blue (MB), and malachite green (MG). In solution studies revealed that the nature of the ligand influences the relative contributions of radical-mediated and high-valent Fe(V)═O oxidation pathways, enabling tunable reactivity. The most active complexes were used as templates to generate water-compatible MIPs that combine adsorption with Fenton-like degradation. The best performing MIPs were those containing the bis(2-pyridylmethyl)amine complex (Fe-BMPA@MIP), prepared either without pH adjustment ( ca. pH 3) or at pH 6. Both achieved 65–98% dye decolorization in 3 h while minimizing iron leaching and converted MB and MG into lower molecular weight products with reduced cytotoxicity. A test in MB-spiked paper-mill effluent further confirmed near-complete decolorization by Fe-BMPA@MIP under realistic conditions. Collectively, these results highlight Fe(III)-complex-imprinted polymers as promising for the design of versatile and efficient pre-treatment platforms that reduce dye pollutant hazards in greener wastewater treatment processes.