Highly porous MnOx prepared from Mn(C2O4)·3H2O as an adsorbent for the removal of SO2 and NH3

Abstract

In this work, the possibility of substituting metal impregnated activated carbon with nanoporous metal oxides for the adsorption of SO2 and NH3 was investigated. Nanoporous manganese oxide (MnOx) was prepared from manganese oxalate trihydrate by thermal decomposition in air. The physical properties of the oxalate precursor and the resulting MnOx samples were characterized with SEM, TGA-DSC, mass spectroscopy, FTIR and powder XRD. The specific surface areas and porosity of MnOx were studied by single-point and multi-point BET measurements. The amorphous needle-like MnOx had a specific surface area of over 500 m2/g when the precursor was heated at 225 °C for 6 h. Dynamic SO2 and NH3 flow tests indicated that the adsorption capacity of MnOx depends primarily on the surface area. Compared to Mn3O4-impregnated activated carbon, nanoporous MnOx could remove about twice as much SO2 and 15% more NH3 per gram of adsorbent. This could lead to respirators of lower weight and smaller size which will be attractive to users.