Eco-friendly magnetic activated carbon modified with green tea extract for efficient adsorption of thiazine and azo dye contaminants from water

Abstract

This study describes the development of maghemite supported activated carbon (MAC) loaded with green tea extract (GTE), as a high-performance adsorbent for the effective extraction of both thiazine dye (methylene blue, MB) and an azo dye (methyl orange, MO) from water. The composite MAC–GTE was prepared through a straightforward wet-chemical method and demonstrated outstanding dye uptake of 491.47 mg g⁻¹ for MB at pH 9 and 337.89 mg g⁻¹ for MO at pH 3.0, with removal efficiency of 98.29% and 90.10%, respectively. Adsorption data showed stronger agreement with the Freundlich isotherm and pseudo-second-order kinetics, indicating multilayer chemisorption. The composite showed strong magnetic response enabling easy magnetic separation and successful recycling. The synergistic combination of maghemite and green tea extract polyphenols enhanced the surface reactivity and accessibility of active sites, suggesting that MAC–GTE may be a promising, and sustainable material for dyes removal applications.