The Preparation of Spherical Activated Carbon-Supported MnO₂ and Its Performance in Formaldehyde Degradation

To develop indoor air purification materials with dual functions of adsorption and degradation, spherical activated carbon-supported mesoporous manganese dioxide (δ-MnO₂@SAC) composites were synthesized via a hydrothermal method. The influence of reaction temperature, KMnO₄ concentration, and reaction time on the morphology and structure of the materials was systematically investigated. The results indicated that a uniform fine rod-like δ-MnO₂ composite with high crystallinity was obtained using 0.05 mol/L KMnO₄ at 120 °C for 2 h. BET analysis revealed that δ-MnO₂@SAC retained the original microporous structure while developing substantial mesopores featuring an average pore size of 23.7 nm. XRD, Raman spectroscopy, and XPS confirmed that Mn existed in the +4 oxidation state and was covalently bonded to SAC, indicating the successful loading of δ-MnO₂ onto the SAC surface. Formaldehyde (HCHO) removal tests demonstrated that MnO₂@SAC achieved 90.66% removal efficiency within 150 min at room temperature and maintained 73% efficiency after six consecutive cycles. In contrast, pure SAC exhibited no further removal capacity after reaching adsorption saturation, highlighting the superior performance of MnO₂@SAC. When combined with wet nonwoven (WN) and melt-blown (MB) to form a composite material, the resulting WN/MnO₂@SAC/MB composite exhibited the PM2.5 filtration efficiency of 99.35% and excellent formaldehyde removal performance. This material shows promise as a novel functional material with great potential for application in indoor air purification.