Magnetite-functionalized eggshell membrane composite: a high-performance magnetic adsorbent for Congo red dye

Abstract

This study develops a sustainable magnetic adsorbent, Fe₃O₄@ESM, by embedding magnetite nanoparticles onto an avian eggshell membrane (ESM) matrix for the efficient remediation of Congo red (CR) from wastewater. Characterization of the functionalized sorbent confirmed a mesoporous structure with a high surface area and abundant binding groups. Zeta potential analysis guided pH optimization. Multivariate optimization was used to identify the optimal conditions for experimental parameters. Under optimum conditions, the proposed sorbent exhibited a high adsorption capacity of 45.04 mg g⁻¹, achieving >96% CR removal. Isotherm and kinetic studies best fitted the Langmuir and pseudo-second-order models, respectively, indicating monolayer, chemisorption-dominated uptake. Thermodynamic studies confirmed a spontaneous, exothermic process with increased interface randomness. The magnetic core enabled simple post-adsorption separation. This work successfully transformed abundant biowaste into high-performance sorbents for sustainable dye removal from wastewater.