Catalytic degradation of methylene blue through activation of bisulfite with CoO nanoparticles

A novel catalytic system was developed by activating NaHSO₃ with CoO nanoparticles for methylene blue (MB) degradation. The CoO nanoparticles were synthesized by a facile one-pot hydrothermal method followed by calcination. The crystallinity, morphology and elemental valence of the CoO were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. MB degradation rates of 91.5% in one minute and 99.4% in six minutes were obtained using the CoO/NaHSO₃ system, which may provide a more cost-effective and efficient way for decomposition of dye pollutants. The well-known classical quenching tests were used to investigate the free radicals involved in MB degradation along with electron paramagnetic resonance (EPR) spectra, the latter further confirmed the types of free radicals. Sulfate and hydroxyl radicals were proposed to be responsible for the excellent dye degradation achieved with the new CoO/NaHSO₃ system.