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 (MnO x ) 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 MnO x were characterized by scanning electron microscopy, energy-dispersive spectrometry, high-resolution transmission electron microscopy, X-ray diffraction, and Raman. As-prepared MnO x /AC exhibited high activity in removing HCHO at room temperature. Gas chromatography analysis indicates that removed HCHO can be finally transformed into CO 2 for a much longer time. Accumulation of carbonate on the surface of MnO x and partial hydroxylation of MnO x lead to the deactivation of MnO x /AC. However, the deactivated sample can be regenerated at 60 °C for 2 h. These results indicate that as-prepared MnO x /AC can be applied for indoor air purification due to its easy preparation and regeneration and high activity for HCHO removal.