Construction of 2D Ni₃S₂ nanosheets-modified ZnO supported on red mud waste-derived aluminosilicate matrix for enhanced photodegradation performance

The development of high-performance photocatalysts utilizing industrial waste-derived supports represents a sustainable approach to environmental remediation. In this study, a novel ternary heterostructure was synthesized, in which two-dimensional nickel sulfide (2D Ni₃S₂) nanosheets and zinc oxide (ZnO) nanoparticles are anchored onto a mesoporous aluminosilicate framework derived from industrial red mud (RMA). Structural and chemical characterizations, including X-ray photoelectron spectroscopy and physisorption analysis, confirmed the successful integration of all components and the preservation of a high-surface-area porous network. Incorporation of 2D Ni₃S₂ nanosheets significantly enhanced the light-harvesting capabilities of the composites, narrowing the optical bandgap from 3.35 eV (pristine ZnO) to 2.93 eV, thereby enabling robust activity under visible light. Photocatalytic evaluations demonstrated that the ternary composite exhibits superior efficiency for the degradation of methylene blue compared to pristine and binary counterparts. The 2D morphology of the Ni₃S₂ nanosheets is critical to this performance, providing extensive charge diffusion and thereby facilitating ion pathways that enable rapid spatial separation of photogenerated carriers. Optimization studies indicated that a catalyst dosage of 60 mg and an alkaline environment (pH 10) maximize degradation kinetics by enhancing electrostatic attraction between the cationic dye and the negatively charged catalyst surface. Furthermore, the composite demonstrated moderate stability, maintaining over 90% removal efficiency after four consecutive cycles. These results underscore the potential to valorize industrial waste into advanced materials for efficient, durable light-driven water purification. Finally, the mechanism underlying MB photodegradation has been clearly elucidated.