Co₃O₄/TiO₂ hetero-structure for methyl orange dye degradation

Advanced oxidation processes based on sulphate radical generated by peroxymonosulphate (PMS) activation is a promising area for environmental remediation. One of the biggest drawbacks of heterogeneous PMS activation is catalyst instability and metal ion leaching. In this study, a simple organic binder mediated route was explored to substitute Ti⁴⁺ ions into the Co₃O₄ host lattice structure to create a Co-O-Ti bond to minimise cobalt leaching during methyl orange degradation. The catalyst was characterised by X-ray diffraction, and scanning and transmission electron microscopy. The as-prepared catalysts with Co₃O₄:TiO₂ ratio of 70:30 exhibited minimal leaching (0.9 mg/L) compared to other ratios studied. However, the pristine Co₃O₄ exhibited highest catalytic activity (rate constant = 0.41 min^-1) and leaching (26.7 mg/L) compared to composite material (70:30 Co₃O₄:TiO₂). Interestingly, the morphology of the composite and leaching of Co²⁺ ions were found to be temperature dependent, as an optimum temperature ensured strong Co-O-Ti bond for prevention of Co²⁺ leaching. The classical quenching test was utilised to determine the presence and role of radical species on methyl orange degradation. The fabricated catalyst also exhibited good catalytic activity in degrading mixed dyes and good recyclability, making it a potential candidate for commercial application.