Synthesis of petal-like δ-MnO2 and its catalytic ozonation performance

Abstract

Petal-like δ-MnO₂ microspheres were successfully synthesized by a very simple hydrothermal method with potassium permanganate (KMnO₄) as the only raw material. By adjusting the initial concentration of KMnO₄ solution and the time of the hydrothermal reaction, the morphology and crystallinity of δ-MnO₂ can be controlled. The synthesized δ-MnO₂ microspheres were characterized by XRD, SEM, TEM, TG/DSC, BET, ICP-AES and XPS. The catalytic ozonation performance of δ-MnO₂ prepared by a hydrothermal reaction at 160 °C for 24 h using 0.1 mol L⁻¹ KMnO₄ solution was tested. Its catalytic activity is excellent. The degradation efficiencies of bisphenol A and ibuprofen using 0.1 g L⁻¹ δ-MnO₂ as the catalyst were 68.2% and 68.5% in 20 min reaction time. The results were much better than those of individual ozone treatment and with commercial MnO₂ as the catalyst. The formation of hydroxyl radicals was not the main reason for the rapid degradation of organic compounds in the catalytic reaction with δ-MnO₂ as the catalyst. The strong interaction among the catalyst surface, ozone and organic molecules was the important reason for catalysis based on the related experimental results.