Synthesis of tungsten-modified δ-MnO₂ and its application in air purification

To improve the catalytic activity and stability of δ-MnO₂ for the formaldehyde decomposition at room temperature, tungsten (W)-modified δ-MnO₂ was prepared by liquid phase precipitation and thermal treatment methods, with potassium permanganate, manganese sulfate monohydrate and ammonium tungstate as raw materials. X-ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area analyzer and X-ray photoelectron spectroscopy (XPS) were used to characterize the phase, microstructure and chemical state of the synthesized δ-MnO₂.Meanwhile, the activity and stability of δ-MnO₂ catalytic decomposition of formaldehyde were studied, and its properties of decomposition volatile organic compounds (VOCs) and sterilization were tested. The results show that the addtion of tungsten element produces the petal-like δ-MnO₂ particles with small particle size and uniform distribution of tungsten, and its catalytic activity can be significantly improved by heat treatment at 200 ℃, with its activation energy of catalystic formaldehyde decomposition only 13.78 kJ/mol. Tungsten modification improves the catalytic activity and stability of δ-MnO₂ in a high humidity environment, and the formaldehyde removal rates remain above 91% in 7 times of cycle tests. At the same time, W-modified δ-MnO₂ also shows excellent performance in both the catalytic decomposition of VOCs gas and sterilization, which indicates broad application prospects in the field of air purification.