Innovative magnetic micromotor ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ for efficient visible light photodegradation of dyes

• Magnetic micromotors synthesized via a simple hydrothermal method. • All micromotors show near superparamagnetic behavior for easy recovery. • ZRFZ-MMs fully degrade CV and RhB in 10 and 160 min under sunlight. • Achieved 96% CV and RhB degradation under mercury lamp irradiation. • Photodegradation follows pseudo-first-order kinetics. The photocatalytic degradation of persistent organic dyes offers a sustainable and efficient approach for wastewater purification. In this study, ferrite–zinc-based magnetic micromotors were synthesized via a hydrothermal process, yielding α-Fe₂O₃/ZnFe₂O₄ (FZ-MMs), ZnO/α-Fe₂O₃/ZnFe₂O₄ (ZFZ-MMs), and the novel ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ (ZRFZ-MMs) heterostructures. Incorporation of reduced graphene oxide (RGO) into the ferrite–ZnO framework created an efficient heterojunction network that extended visible-light absorption, promoted charge separation, and improved electron transport. Structural and surface analyses confirmed the successful integration of ZnO, ferrite, and RGO phases with a porous hierarchical morphology and enlarged surface area, while magnetic measurements verified near superparamagnetic behavior, ensuring rapid and lossless recovery. Electrochemical studies revealed efficient interfacial charge transfer and n-type semiconductor behavior with favorable band alignment for visible-light excitation. Under sunlight irradiation, the ZRFZ-MMs achieved complete degradation of crystal violet (CV) within 10 min and rhodamine B (RhB) within 160 min, while mercury-lamp tests yielded over 96% dye removal. The superior activity is attributed to the synergistic heterojunction mechanism and the dominant role of superoxide and hydroxyl radicals, as confirmed by scavenging experiments. Furthermore, ZRFZ-MMs demonstrated outstanding durability across multiple reaction cycles, retaining nearly complete photocatalytic efficiency without significant loss. Their robust recyclability, combined with sunlight-powered operation and effortless magnetic separation, positions them as a practical alternative for dye removal and wastewater purification. This composite enables simple addition to and retrieval from treatment systems, preserving superior degradation performance while eliminating common challenges associated with photocatalyst separation.