Iron-doped g-C₃N₄ modified CoMoO₄ as an efficient heterogeneous catalyst to activate peroxymonosulfate for degradation of organic dye

Abstract

In this work, iron-doped graphite carbon nitride (Fe-g-C₃N₄) was integrated with CoMoO₄ through a simple hydrothermal route and high temperature calcination to synthesize distinctive composites, aiming to create a promising heterogeneous catalyst to active peroxymonosulfate (PMS) for the degradation of methylene blue (MB), a widely used organic dye. The characterization results, including SEM, EDX, FTIR, XRD and XPS, indicated that the crystal structure and physicochemical properties of CoMoO₄-Fe-g-C₃N₄ have changed after modification, with rougher surface and efficient catalytic activity. The effects of several operational factors (catalyst dosage, oxidant dosage, reaction temperature and initial pH) were also extensively evaluated. Under the condition of CoMoO₄-Fe-g-C₃N₄=0.1 g L⁻¹, oxidant = 2.0 mM, dye = 100 mg/L, T = 25 °C, the MB in the CoMoO4-Fe-g-C3N4/PMS catalytic system can reach almost complete degradation in 90 minutes without pH adjustment. Further, stability experiment showed that the CoMoO₄-Fe-g-C₃N₄ catalysts exhibited high stability and superior reusability, with 80% removal rate even after five concessive cycles of use. Additionally, through radical quenching experiments, it proved that SO₄^•− radicals were dominant and HO^• radicals also worked in the MB degradation process. An underlying mechanism was proposed based on the detection of XPS results that both radical and non-radical degradation pathways existed during MB degradation process. The electron transfer from high-valence iron species (Fe^IV=O) to MB resulting in the degradation of MB through a non-radical mechanism. From the investigation, the CoMoO₄-Fe-g-C₃N₄ composite was proved to have potential superiority as a promising catalyst for the degradation of refractory organic contaminant removal from water.