Birnessite-Type Manganese Oxide on Granular Activated Carbon for Formaldehyde Removal at Room Temperature

Formaldehyde (HCHO) is a priority indoor air pollutant due to its adverse impact to human health. A layer of birnessite-type manganese oxide (MnOx) was facilely coated on the granular activated carbon (AC) via in situ reduction of permanganate with AC at room temperature. The properties and growing process of MnOx were characterized by scanning electron microscopy, energy-dispersive spectrometry, high-resolution transmission electron microscopy, X-ray diffraction, and Raman. As-prepared MnOx/AC exhibited high activity in removing HCHO at room temperature. Gas chromatography analysis indicates that removed HCHO can be finally transformed into CO2 for a much longer time. Accumulation of carbonate on the surface of MnOx and partial hydroxylation of MnOx lead to the deactivation of MnOx/AC. However, the deactivated sample can be regenerated at 60 °C for 2 h. These results indicate that as-prepared MnOx/AC can be applied for indoor air purification due to its easy preparation and regeneration and high activity for HCHO removal.