Supported Co₃O₄ on expanded graphite as a catalyst for the degradation of Orange II in water using sulfate radicals

Abstract

A kind of heterogeneous catalysts is fabricated in situ by the decomposition of cobalt nitrate through heat and crystal growth of cobalt oxide (Co₃O₄) on the surface of expanded graphite (EG) in 1-hexanol solvent. The Co₃O₄/EG catalyst can activate peroxymonosulfate for the degradation of Orange II in water. The test results of X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy (Raman), scanning electron microscopy, and high resolution transmission electron microscopy show that the Co₃O₄/EG catalysts are EG decorated homogenously with well-dispersed Co₃O₄ nanoparticles. The Co₃O₄/EG catalysts exhibit an unexpectedly high catalytic activity than Co₃O₄ or EG alone in the degradation of Orange II in water by advanced oxidation processes based on sulfate radicals, and 100% decomposition can be achieved in 8 min. These phenomena suggest that there is a synergistic catalytic activity between Co₃O₄ and EG.

Keywords:

• Expanded graphite
• Cobalt oxide
• Sulfate radical
• Advanced oxidation processes
• Orange II

Acknowledgements

The study was supported by the Fundamental Research Funds for the Central Universities (12D11319), Shanghai Tongji Gao Tingyao Environmental Science & Technology Development Foundation (STGEF), Innovation Program of Shanghai Municipal Education Commission (12ZZ069), Shanghai Municipal Natural Science Foundation (No. 11ZR1400400), Fundamental Research Funds for the Central Universities (No. 11D11303), and Shanghai Leading Academic Discipline Project (No. B604).