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

• For the AC-MO materials, the total loss of mass varies between 2.47 and 23.20 wt%.
• Dehydration, dehydroxylation, decarboxylation, carbothermal reduction, etc. occur.
• The number of thermal effects desorbing CO2 and CO is larger with the metal ions.
• Dehydroxylation is stronger than dehydration only with the Fe3+ ion and with TiO2.
• The masses of evolved gases are much higher for the sample prepared with SnCl2.

Activated carbon (AC)-metal (hydr) oxide (MO) materials prepared by wet impregnation of a commercial AC with Al3+, Fe3+, Zn2+, SnCl2, TiO2 and WO42− in water at pH between 1.37 and 9.54 in two successive soaking and oven-drying steps are analysed by thermogravimetry-mass spectrometry (TG-MS) between 25 and 900 °C. Under identical conditions, a blank sample (ACB) was first prepared using deionized water and then thermally analyzed. The mass loss in the TG analysis is 1.35 wt% for AC, 2.12 wt% for ACB, and between 2.47 and 23.20 wt% for the AC-MO materials. For these materials, it depends on the impregnation agent and varies by SnCl2 > Fe3+ > Al3+ > Zn2+ > WO42− > TiO2. The number of thermal effects giving off CO2 and CO is larger with the Al3+, Fe3+ and Zn2+ ions than with SnCl2, TiO2 and WO42−. It is so in particular for CO2 with the Fe3+ ion and for CO with the Al3+ ion. In general, the release of CO at high temperature has been associated with the carbothermal reduction of metal oxides. As a result of the reaction low-melting point metals such as Al, Zn and Sn, unlike Fe and W, are formed which vaporize and thereby contribute to the mass loss. Only with Fe3+ and TiO2, the amount of desorbed water is larger by dehydroxylation than by dehydration. The masses of evolved H2O, CO2 and CO are by far higher with SnCl2, whereas they are lower with TiO2 and WO42−.