High-entropy Fe-based spinel oxide for simultaneous electrochemical desalination and dye adsorption in textile wastewater remediation

The treatment of textile wastewater, which contains complex mixtures of persistent dyes and inorganic salts, remains a critical challenge due to the limitations of conventional biological and physicochemical methods. We developed a high-entropy Fe-based spinel oxide (HEFSO, (Co_0.2Ni_0.2Zn_0.2Mg_0.2Cu_0.2)Fe₂O₄) that demonstrates superior performance in simultaneous dye adsorption and capacitive deionization compared to conventional Fe₃O₄. For salt removal, the HEFSO achieves a superior electrosorption capacity of 98.8 mg g⁻¹ and 95 % capacity retention over 100 cycles, attributed to its entropy-stabilized lattice distortions and oxygen vacancies. Density functional theory calculations reveal that multication synergy reduces Na⁺ migration barriers by 1.09 eV and adjusts adsorption sites, explaining the accelerated ion kinetics and enhanced adsorption ability. Furthermore, the HEFSO exhibits a strongly negative surface charge (zeta potential = −23.15 mV at pH 7), enabling up to 92 % higher adsorption capacity for cationic dyes (methylene blue, rhodamine 6G) than Fe₃O₄. This work not only demonstrates the first application of high-entropy spinel oxides in hybrid capacitive deionization (HCDI) but also provides atomic-level insights into their dual-functionality, offering a scalable material platform for textile wastewater remediation.