SOME REGULARITIES OF OZONE DECOMPOSITION OVER NATURAL BENTONITE ANCHORED 3d METAL ACIDO COMPLEXES

Abstract

Polyphasicity of both natural bentonite and catalysts based on the latter has been found by X-ray phase analysis and IR spectroscopy. In natural bentonite, the indentified phases were montmorillonite, α-quartz and calcite as an impurity. The formation of MCl2/N-Bent catalysts (M = Cu2+, Co2+, and Mn2+) does not lead to significant structural changes or to the formation of new phases from the catalyst components. However, an increase in a basal distance d001 for montmorillonite observed in this case can be evidence of the metal ion entering into its interlayer space because this increase agrees with the sizes of the metal ions (rCo < rCu < rMn). In the IR spectrum of natural bentonite, the bands assigned to stretching vibrations of OH groups bound with octahedral cations (M-OH) and to water molecules associated through hydrogen bonds are situated in the region 4000-3000 cm-1, the absorption bands of the silicate structure are concentrated in the region 1400-400 cm-1. The absorption band at 1421 cm-1 assigned to stretching vibrations of carbonate ion confirms calcite presence in this natural bentonite. Anchoring of Cu(II), Co(II) or Mn(II) chlorides onto natural bentonite results in a low-frequency shift of this absorption band. For the first time, the kinetics of the lowtemperature ozone decomposition over the MCl2/N-Bent compositions was investigated. It has been found that the CuCl2/N-Bent sample shows the lowest activity that can be explained by the thermodynamic forbiddenness of Cu(II) oxidation with ozone. The activity of the MnCl2/N-Bent and CoCl2/N-Bent samples depends on metal ion concentrations. Ozone decomposition over the MnCl2/N-Bent samples with CМnCl2 of 1.2∙10-6 and 2.4∙10-4 mol/g was effective only at the initial stage of the ozone-air mixture, OAM, passage through the sample, whereas, for CoCl2/N-Bent samples, the kinetic curve portions parallel to x-axis indicated that the steady state mode was settled. At CСоCl2= 2.4∙10-4 mol/g, C f O3 was 47 mg/m3 (CinO3 = 100 mg/m3) even in 30 h of the OAM passage. Thus, it has been found that the catalytic activity of the MCl2/N-Bent samples towards the ozone decomposition changes in the orders: at CМnCl2= 1.2∙10-6 mol/g: N-Bent < СuСl2/N-Bent < CoСl2/N-Bent < MnСl2/N-Bent (І), at CМnCl2= 2.4∙10-6 mol/g: N-Bent < СuСl2/N-Bent << MnСl2/N-Bent < CoСl2/N-Bent (ІІ).

Keywords

• бентоніт
• фазовий склад
• розкладання озону