Nanocrystalline ZnMn ₂ O ₄ Photocatalyst from Spent Zinc–Carbon Batteries for Water Treatment

The alarming increase in pharmaceutical contaminants and toxic dyes in aquatic environments necessitates the development of innovative and sustainable remediation strategies. This study presents a circular economy‐driven method to synthesize nanocrystalline ZnMn ₂ O ₄ photocatalysts from spent zinc–carbon batteries for the degradation of ciprofloxacin, a widely used broad‐spectrum antibiotic. The ZnO (from the anode) and MnO ₂ (from the cathode) are recovered and used as precursors in the solid‐state synthesis of ZnMn ₂ O ₄ via thermal treatment. Characterizations by X‐ray diffraction, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy confirm the formation of a crystalline spinel structure with uniform elemental distribution. The synthesized ZnMn ₂ O ₄ exhibits strong visible‐light absorption with a narrow bandgap of 1.94 eV and high photocatalytic efficiency in degrading ciprofloxacin, with a 71% degradation. The material displays excellent stability, reusability, and degradation kinetics, making it suitable for real‐world applications. This work not only provides a sustainable method for valorizing battery waste but also offers a low‐cost, environmentally friendly photocatalyst for wastewater processing, following green chemistry guidelines and the circular economy.