Nanocrystalline metal oxides as new adsorbents for air purification

Nanocrystals of MgO, CaO, and Al₂O₃ were prepared by aerogel (AP-samples) or conventional (CP-samples) methods. High surface areas/gram were obtained, often as high as 500 m²/g (1). These materials were investigated as adsorbents for typical volatile organic compounds that are representative of air pollutants. As a result of their high surface areas and their enhanced surface reactivity, nanocrystalline MgO, CaO and Al₂O₃ have shown remarkably high capacities to chemically adsorb such organic compounds. Compared to high surface area activated carbon, the most widely used material in this application, our nanocrystalline materials have exhibited higher capacities and the ability to destructively adsorb rather than physisorb these chemicals. FT-IR investigation of acetaldehyde adsorption on AP- and CP-MgO indicates that a multilayer dissociative adsorption took place. Adsorption of other organic compounds was also investigated including acetone, propionaldehyde, benzaldehyde, trimethylacetaldehyde, ammonia, dimethylamine, N-nitrosodiethylamine, and methanol, most of which were found to adsorb well on AP-MgO. In addition, long term air exposure did not have detrimental effects on the adsorption properties of AP-MgO.