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Reviste: » Environmental Engineering and Management Journal» European Journal of Science and Theology» Sănătate Sport și Nutriție
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PREDICTION OF TiO2 AND WO3 NANOPOWDERS SURFACE CHARGE BY THE EVALUATION OF POINT OF ZERO CHARGE (PZC) Autori: Laura Maria Bertus, Radu Adrian CarcelData aparitiei: August/2011 Revista: Environmental Engineering and Management Journal › Vol. 10 › Nr. 8 ISSN: 1843 - 3707 ![]() Abstract:
Point of zero charge (PZC) is defined as the condition at which the surface charge density of a material equals to zero and, for most of the solids it is strongly pH dependent. The PZC can be controlled by tuning the solid surface properties (crystalline structure, morphology) and by a proper environment control, thus it is important to evaluate the PZC for a certain type of material, in given working conditions, for enhancing the efficiency in the targeted application (e.g. layer by layer thin films deposition, adsorption including (photo)catalysis). TiO2 and WO3 are semiconductor materials with tremendous potential in environmental applications such as photocatalysis process used for water treatment. This paper presents the results obtained in PZC evaluation, by pH-titration, for the WO3 nanopowder (~30 nm) and the state of the art - TiO2 Deggusa P25. The pH titration was done using different amounts of TiO2 and WO3 nanopowders, in 0.1 M NaOH solution, by adding μL portions of 0.1 M HCl. Considering the WOx Pourbaix diagram, experiments were also done using NH4OH, for eliminating the Na2WO4 formation at the WO3 surface. The PZC was evaluated on the derivative of the pH titration curve, at the significant peak(s). The PZC values were found strongly dependent on the chemical surface composition and only slightly dependent on the crystalline structure and morphology. The results proved that, in PZC reporting it is important to specify the experimental conditions, especially for highly pH-reactive solids like WO3. |