Single atom cobalt catalyst derived from co-pyrolysis of vitamin B12 and graphitic carbon nitride for PMS activation to degrade emerging pollutants

This study prepared the carbon-supported cobalt catalyst (Co-C-X) for activating peroxymonosulfate (PMS), and investigated the effect of co-pyrolysis temperature of graphitic carbon nitride (g-C 3 N 4 ) and vitamin B 12 on the catalytic activity. It was found that with the increase of co-pyrolysis temperature, the catalytic activity of Co-C-X increased, due to the different coordination structures of cobalt. At 500 °C (Co-C-500), cobalt existed as CoO; while it was single atom Co at 600 °C (Co-C-600); and small size CoO at 700 °C (Co-C-700). Co-C-X could activate PMS to produce hydroxyl radicals, sulfate radicals, high-valent cobalt-oxo and singlet oxygen, which depended on the pyrolysis temperature. Although Co-C-700 had the highest catalytic activity, the leaching cobalt was also highest (3.23 mg/L), compared with that of Co-C-500 (0.27 mg/L) and Co-C-600 (0.14 mg/L). Co-C-600 had fast degradation for atrazine, nitrobenzene , bisphenol A, phenol and 4-chlorophenol, which also had wide pH range and high tolerance to inorganic ions.