Highly efficient CuO@ZnHCC heterostructure enabling rapid sunlight-driven detoxification of persistent organic dyes

Abstract

The toxicity, chemical stability, and resistance to biodegradation of synthetic dyes make their continuous release from industrial effluents into aquatic environments a serious environmental and public health hazard. This study used a green co-precipitation approach to create a CuO decorated zinc hexacyanocobaltate (CuO@ZnHCC) nanocomposite, which was then used to photocatalytically degrade Tropaeolin OOO (TOOO) and Methylene Blue (MB) dyes in the presence of natural sunlight. Using methods like XRD and SEM, the material's phase purity, composition, and morphology were described. The nanocomposite conformed to the Langmuir adsorption model along with first-order kinetics to attain degradation efficiencies of 97% for MB and 93% for TOOO in 90 minutes under ideal circumstances (10 mg/L dye, 20 mg–25 mg catalyst, pH 7–11). Due to its negative zeta potential (-22.6 mV), narrow band gap of approximately 1.68 eV, improved adsorption capacity, and inhibited electron–hole recombination, the CuO@ZnHCC composite demonstrated higher photocatalytic activity when compared to individual CuO and ZnHCC. Intermediate metabolites were identified by both GC-MS and LC-MS analyses, while scavenger experiments verified that photogenerated holes, O2•− and •OH radicals played key roles in the breakdown mechanism. Over nine cycles, the catalyst showed outstanding reusability with minimal activity loss. The findings emphasize the importance of integrating eco-friendly synthesis approaches with advanced photocatalysts for sustainable dye remediation. Keywords: Photocatalytic breakdown, CuO@ZnHCC nanocomposite, Organic pollutants, Green synthesis, Recyclability