Photocatalytic degradation of Congo Red dye using Na and K doped ZnO nanoparticles obtained via sour orange ( Citrus aurantium L.) extracts

This work addresses the environmental issue generated by the discharge of industrial effluents containing the azo dye Congo Red. With the objective of proposing an alternative treatment, zinc oxide nanoparticles doped with sodium and potassium were obtained through a sustainable synthesis route utilizing sour orange. X-ray diffraction confirmed a wurtzite phase with an average crystallite size of 39 nm, while X-ray photoelectron spectroscopy validated the effective incorporation of the alkaline dopants. Scanning electron microscopy analysis revealed that sodium promotes the formation of agglomerated nanorods, whereas potassium favors porous coral-like structures. Ultraviolet visible (UV-Vis) spectroscopy showed a reduction in the band gap from 3.22 eV to 3.18 eV. The potassium-doped ZnO catalyst presented the best performance, achieving 100% removal of Congo Red in 180 min. Thus, the integration of alkaline dopants generates nanoparticles with enhanced properties compared to undoped ZnO, positioning the potassium-doped system as a high-performance photocatalyst for industrial wastewater treatment.