Green synthesis of Co3O4 nanoparticles using spent coffee: Application in catalytic and photocatalytic dye degradation

Clean water is vital for societal progress, however, the pollution caused by dyes presents a significant global challenge. Dye-contaminated industrial effluent overwhelms wastewater treatment facilities, causing harm to water bodies and ecosystems. This study demonstrates the synthesis of Co₃O₄ nanoparticles using spent coffee extract as a bioreducing agent and its application in dye degradation. The structural and optical properties of nanostructures were confirmed using X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and UV–vis spectroscopy. The Co₃O₄-activated peroxymonosulfate (PMS) system exhibited exceptional catalytic efficiency by attaining a degradation rate of 89.27 % for Tartrazine dye within a 30-minute timeframe, even in the absence of illumination. When exposed to simulated visible light, the degradation kinetic rate increased by 37.60 %, highlighting the excellent photocatalytic activity of Co₃O₄ nanoparticles. Furthermore, leveraging natural sunlight led to a notable Tartrazine degradation rate of 97.11 %, signifying a substantial 45.41 % enhancement in reaction efficiency when contrasted with the conventional Co₃O₄/PMS system. Lastly, the Co₃O₄ nanoparticles illustrated remarkable degradation of synthetic industrial dye effluents (Tartrazine, Methyl Orange, and Remazol Brilliant Red), reaching up to 92.77 % removal, indicating its potential for use in real-world scenarios.