Green Conversion of Industrial Red Mud for Multifunctional Photocatalysis

Red mud is an industrial waste generated during alumina production from bauxite ore. It contains abundant minerals with strong reactivity. By converting it into functional materials, red mud can be utilized as an adsorbent or photocatalyst for wastewater treatment, effectively removing dyes and heavy metals. In this study, iron oxide and TiO₂–doped zeolites (FETIZE) were synthesized from red mud (RM) through an alkali fusion process with NaOH followed by hydrothermal treatment and applied for the photocatalytic degradation of methylene blue (MB), methyl orange (MO), and congo red (CR) dyes. A magnetic separation step was employed to lower the iron content of RM prior to synthesis. Under optimized conditions (10 ppm dye concentration, 100 mg/L FETIZE, pH ~ 5, and calcination at 870–873 K under UV light), FETIZE achieved degradation efficiencies of ~ 66% for MB, 8% for MO, and 37% for CR within 3 hours, while commercial zeolites doped with iron oxide and TiO₂ showed comparatively higher degradation rates over longer durations. Structural and surface characterizations by XRD, XRF, SEM, and UV-DRS, along with electrochemical studies, confirmed FETIZE’s enhanced surface area, improved charge separation, reduced charge transfer resistance, and increased photocurrent density relative to RM. Furthermore, FETIZE maintained good reusability over three consecutive cycles. Overall, this work demonstrates the dual advantage of converting industrial solid waste into a functional photocatalyst while providing an effective strategy for dye-contaminated water treatment.