[Activated Carbon Supported Co₃O₄ Catalysts to Activate Peroxymonosulfate for Orange G Degradation]

Activated carbon supported cobalt catalysts (Co/AC) were prepared through wet impregnation and high temperature calcination methods. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) characterization results showed that Co₃O₄ was the major form of Co species distributed on AC. The performance of Co/AC was evaluated as catalyst to activate peroxymonosulfate (PMS) to produce sulfate radicals (SO₄^-·) for Orange G (OG) degradation in solution. The activation mechanism and several influential factors were also investigated. The results demonstrated that SO₄^-·played a dominant role in OG degradation. And the degradation efficiency of OG increased with increasing Co/AC dosage, higher PMS concentration or elevating reaction temperature. Initial pH had a significant effect on OG degradation, with pH range of 4 to 8 as the optimal pH for degradation. In addition, the strong acidic or alkaline conditions were unfavorable for OG degradation. A dual effect of chloride ions (Cl^-) was observed. The high Cl^- concentration promoted degradation, while low concentration led to inhibition. The Co/AC also exhibited excellent reusability and its activating performance toward PMS was still observed after 6 rounds of tests. Finally, the degradation process and intermediate products of OG were analyzed with UV-visible spectroscopy and gas chromatography-mass spectrometry (GC/MS).