Effectiveness of metal oxide catalysts for the degradation of 1,4-dioxane

1,4-dioxane, commonly used as a solvent stabilizer and industrial solvent, is an environmental contaminant and probable carcinogen. In this study, we explored the concept of using metal oxides to activate H₂O₂ catalytically at neutral pH in the dark for 1,4-dioxane degradation. Based on batch kinetics measurements, materials that displayed the most suitable characteristics (high 1,4-dioxane degradation activity and high H₂O₂ consumption efficiency) were ZrO₂, WO_x/ZrO₂, and CuO. In contrast, materials like TiO₂, WO₃, and aluminosilicate zeolite Y exhibited both low 1,4-dioxane degradation and H₂O₂ consumption activities. Other materials (e.g., Fe₂O₃ and CeO₂) consumed H₂O₂ rapidly, however 1,4-dioxane degradation was negligible. The supported metal oxide WO_x/ZrO₂ was the most active for 1,4-dioxane degradation and had higher H₂O₂ consumption efficiency compared to ZrO₂. In situ acetonitrile poisoning and FTIR spectroscopy results indicate different surface acid sites for 1,4-dioxane and H₂O₂ adsorption and reaction. Electron paramagnetic resonance measurements indicate that H₂O₂ forms hydroxyl radicals (˙OH) in the presence of CuO, and unusually, forms superoxide/peroxyl radicals (˙O₂⁻) in the presence of WO_x/ZrO₂. The identified material properties suggest metal oxides/H₂O₂ as a potential advanced oxidation process in the treatment of 1,4-dioxane and other recalcitrant organic compounds.

FTIR and surface poisoning results suggest 1,4-dioxane adsorbs to Lewis acid sites on metal oxide surfaces and is degraded by surface radical species.