Enhanced photodegradation of organic dyes using copper and zinc aluminate nanophotocatalysts

This study aims to enhance the photocatalytic efficiency of CuxZn1-xAl2O4 (x = 0.0, 0.2, 0.4, 0.6, and 0.8) nanophotocatalysts synthesized via a sol-gel self-combustion method. Rietveld analysis confirmed the formation of single-phase spinels with a face-centered cubic structure and Fd-3m space group symmetry, while electron density distribution analysis supported the ionic character of bonding within the material. Subsequent UV–visible spectroscopy revealed that the addition of Cu(II) reduced the band gap from 4.66 eV to 2.54 eV, facilitating enhanced light absorption. Consequently, the catalyst with x = 0.8 deteriorated 95 % of methyl orange (MO) and 93 % of rhodamine-B (RhB) in 120 min of visible light irradiation, following a pseudo-first-order kinetic model. The Cu0.8Zn0.2Al2O4 sample demonstrated significant reusability and stability, with degradation rates of 93–79 % for RhB and 95–81 % for MO after four cycles. Scavenging studies indicated that photoexcited holes (h), hydroxyl radicals (OH•), and superoxide radicals (O₂•⁻) were key factors in the degradation process. This study presents an improved approach for enhancing the photodegradation performance of the Cu0.8Zn0.2Al2O4 catalyst for pharmaceutical and wastewater treatment applications. •Sol-gel auto-combustion synthesis of CuxZn1-xAl2O4 (x = 0.0, 0.2, 0.4, 0.6, and 0.8) photocatalysts.•Tailoring structural properties of the aluminate polycrystalline spinels for photocatalytic activity.•Investigation of chemical states and electronic structures of the spinel systems.•Effect of Cu2+ cations substitution on structural and microstructural characteristics of the aluminate spinels.•Tuning optical band gap and solar-illuminated degradation response of aluminate spinel nano-catalysts towards organic toxins.