Co3O4 mediated microwave catalysis: A new innovative advanced oxidation process (AOP) for the removal of dye pollutants from water

MnO2 and Co3O4 are identified as two highly MW active catalysts for the degradation and eventual mineralization of trace amounts of the toxic pollutant dye IC in water. The degradation is much faster compared to identical conventional heating conditions suggesting that the MW effect is not just thermal. ‘Specific effects’ and ‘athermal effects’ of MW also contribute to the degradation of the pollutant. The effect of pH on the degradation is only marginal over a wide range of 4-10, thereby proving the ability of MW to modify the pH effect in many cases. Addition of H2O2 has limited influence on the MW-assisted degradation at lower concentration range while it has a positive enhancing effect at higher concentrations. Another oxidant persulphate enhances the MW/Co3O4 degradation. Natural water contaminants like salts/anions also do not affect the degradation significantly. The microwave radiation may not be affecting the surface characteristics of the oxides as in the case of other AOPs even though the lattice oxygen removed from the catalyst plays significant role in the degradation. This lattice oxygen vacancy is later replenished by dissolved oxygen taking MnO2 /Co3O4 to its respective original composition.