Preparation of activated carbon-metal (hydr) oxide materials by thermal methods. Thermogravimetric-mass spectrometric (TG-MS) analysis

Abstract

[EN] tActivated carbon (AC)-metal (hydr) oxide (MO) materials prepared by wet impregnation of a commercialAC with Al3+, Fe3+, Zn2+, SnCl2, TiO2and WO42−in water at pH between 1.37 and 9.54 in two successivesoaking and oven-drying steps are analysed by thermogravimetry-mass spectrometry (TG-MS) between25 and 900◦C. Under identical conditions, a blank sample (ACB) was first prepared using deionized waterand then thermally analyzed. The mass loss in the TG analysis is 1.35 wt% for AC, 2.12 wt% for ACB, andbetween 2.47 and 23.20 wt% for the AC-MO materials. For these materials, it depends on the impregnationagent and varies by SnCl2> Fe3+> Al3+> Zn2+> WO42−> TiO2. The number of thermal effects giving off CO2and CO is larger with the Al3+, Fe3+and Zn2+ions than with SnCl2, TiO2and WO42−. It is so in particular forCO2with the Fe3+ion and for CO with the Al3+ion. In general, the release of CO at high temperature hasbeen associated with the carbothermal reduction of metal oxides. As a result of the reaction low-meltingpoint metals such as Al, Zn and Sn, unlike Fe and W, are formed which vaporize and thereby contribute tothe mass loss. Only with Fe3+and TiO2, the amount of desorbed water is larger by dehydroxylation thanby dehydration. The masses of evolved H2O, CO2and CO are by far higher with SnCl2, whereas they arelower with TiO2and WO42−.