Supported cobalt oxide on graphene oxide: highly efficient catalysts for the removal of Orange II from water.

The current paper investigated the removal of the azo dye Orange II from water using advanced oxidation processes based on sulfate radicals. The cobalt oxide catalyst immobilized on graphene oxide (GO) can activate peroxymonosulfate (PMS) for the degradation of Orange II in water. The Co(3)O(4)/GO catalyst system was characterized via X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and X-ray spectroscopy. Results showed that Co(3)O(4) was distributed on GO. The Co(3)O(4)/GO catalyst system exhibited high activity in Orange II oxidation when the Co(3)O(4)/GO catalyst has an optimum Co(3)O(4) loading. In addition, 100% decomposition could be achieved within 6 min with 0.2mM Orange II, 0.1 g L(-1) catalyst, and 2mM PMS. Meanwhile, inductively coupled plasma analysis revealed that the leach of cobalt ions was low. The catalyst also exhibited stable performance after several rounds of regeneration. Several operational parameters, such as catalyst amount, oxidant amount, pH, temperature, and oxidation rate, affected the degradation of Orange II.