2005

Štengl, V.; Maříková, M.; Bakardjieva, S.; Šubrt, J.; Opluštil, F.; Olšanská, M., Reaction of sulfur mustard gas, soman and agent VX with nanosized anatase TiO2 and ferrihydrite. Journal of Chemical Technology and Biotechnology 2005, 80 (7), 754-758.

Abstract: Homogeneous hydrolysis of titanium oxo-sulfate and iron(III) sulfate has been used to prepare anatase TiO2 and ferrihydrite with high specific surface area. Resulting samples were characterised by specific surface area (Brunauer–Emmett–Teller method) and porosity (Barrett–Joyner–Halenda method) measurements, X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The samples of anatase TiO2 and ferrihydrite were evaluated for their ability to degrade chemical warfare agents (sulfur mustard gas, soman and agent VX) to non-toxic products. The largest percentage of mustard gas converted into non-toxic products after the completion of the reaction was 99%. Link

Štengl, V.; Bakardjieva, S.;  Šubrt, J.; Večerniková, E., Characteristic of hydrous iron (III) oxides prepared by homogeneous precipitation of iron (III) sulphate with urea. Solid State Sciences 2005, 7 (4), 367-374.

Abstract: Hydrous iron (III) oxides agglomerated into uniform porous spherical clusters with submicrometre size and high specific surface area were obtained. Homogeneous precipitation of iron (III) sulphate was carried out in boiling aqueous solution that contained excess of urea. The prepared precursor precipitates were heated for 2 h at various temperature (from 200 to 800 °C) to yield fine iron oxides powders. The structure evolution during heating of powders was investigated by X-ray diffraction (XRD). The morphology and microstructure characteristics were also obtained by means of scanning electron microscopy (SEM), (BET) and (BJH). In order to see the phase transition temperature thermogravimetric analysis/differential thermal analysis studies were performed. It was found that formation of different hydrous iron (III) oxides was affected by experimental conditions: aging time, mixing procedure, pH and temperature. Link

Bakardjieva, S.; Šubrt, J.; Štengl, V.; Dianez, M. J.; Sayagues, M. J., Photoactivity of anatase-rutile TiO2 nanocrystalline mixtures obtained by heat treatment of homogeneously precipitated anatase. Applied Catalysis B-Environmental 2005, 58 (3-4), 193-202.

Abstract: Nanosized titanium dioxide photocatalysts with varying amount of anatase and rutile phases have been synthesized. Homogeneous precipitation of aqueous solutions containing TiOSO4 with urea was used to prepare porous spherical clusters of anatase TiO2. Photoactive titania powders with variable amount of anatase and rutile phases were prepared by heating of pure anatase in the temperatutre range 800–1150 °C. The structure evolution during heating of the starting anatase powders was studied by XRD analysis in overall temperature range of phase transformation. The morphology and microstucture characteristics were also obtained by HRTEM, BET and BJH. The spherical particle morphology of TiO2 mixtures determined by SEM was stable in air up to 900 °C. The photocatalytic activity of the sample titania TIT85/825 heated to 825 °C in air, contained 77.4% anatase and 22.6% rutile was higher than that nanocrystalline anatase powder. Titania sample TIT85/825 reveals the highest catalytic activity during the photocatalyzed degradation of 4-chlorophenol in aqueous suspension. Link

Balek, V.; Todorova, N.; Trapalis, C.; Štengl, V.; Večerníková, E.; Šubrt, J.; Málek, Z.; Kordas, G., Thermal behavior of Fe2O3/TiO2 mesoporous gels. Journal of Thermal Analysis and Calorimetry 2005, 80 (2), 503-509.

Abstract: Titania-based photocatalytic materials were prepared by sol-gel method using Fe3+ and polyethyleneglycol (PEG600) as additives. Thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) with MS detection were used to elucidate processes that take place during heating of Fe3+ containing titania gels. The microstructure development of the Fe2O3/TiO2 gel samples with and without PEG600 admixtures was characterized by emanation thermal analysis (ETA) under in situ heating in air. A mathematical model was used for the evaluation of ETA results. Surface area and porosity measurements of the samples dried at 120°C and the samples preheated for 1 h to 300 and 500°C were compared. From the XRD measurements it was confirmed that the crystallization of anatase took place after thermal heating up to 600°C. Link