Indoor formaldehyde removal by catalytic oxidation, adsorption and nanofibrous membranes: a review

Indoor pollution of air by formaldehyde poses a serious threat to human health because formaldehyde causes illnesses and discomfort even at low levels, thus calling for abatement techniques. Techniques include absorption, physisorption, chemisorption, biological and botanical filtration, photocatalytic decomposition, membrane separation, plasma and catalytic oxidation. Here we review the principles, performances, advantages and disadvantages of these techniques, with focus on catalytic oxidation, adsorption and the use of nanofibrous membranes. Supported noble metal and metal oxide-based materials are efficient catalysts for oxidation. We present photocatalytic oxidation under UV, visible and solar light using composites. Chemisorption method is reviewed with focus on amino-containing adsorbents, conditions of temperature and relative humidity and surface properties. Nanofibrous membranes display high density of active sites for pollutant interactions and allow formaldehyde removal without leaching out of catalyst nanoparticles or adsorbents.