Search

Using the hydrothermal method, the iron hydroxyl phosphate materials Fe5(PO4)4(OH)3·2H2O (giniite), with an orthorhombic crystal structure were obtained. SEM analysis showed that the morphology of these iron hydroxyl phosphates is influenced by the pH of the aqueous solution from the hydrothermal synthesis: for pH=1.5 (Sample A) the shape of particles is spherical and by increasing the pH to 4.5 (Sample B) the particles transforms into dendrites. The electrical conductivity σ of these two giniite samples was studied in 20 Hz to 2 MHz frequency range at room temperature. The results show that the spectrum of σ conductivity, presents two regions: i) a first region, where σ remains constant at low frequency (the σDC component) and ii) a dispersion region, where the σ increases with increasing the frequency (the σAC component). For both samples, at the frequency f=1 kHz, the temperature dependence of conductivity (σ) and resistivity (ρ) at the variation of temperature between 25 °C to 200 0C, have been analyzed. The results show that the slope of ρ, changes with the increase of temperature at two temperatures, between (60-80) °C and respectively (160- 170) °C, which may be associated with changes in the structure of giniite samples, due to loss of water molecules by increasing of temperature. [ABSTRACT FROM AUTHOR]

In this paper, a photocatalytic evaluation was carried out for several synthetized samples of glass foam coated with different amounts of TiO2 and WO3, respectively in order to investigate their capacity to remove Rhodamine B (RhB) from aqueous solution, under simulated solar irradiation. As the organic dyes are considered a major source of pollution to the environment, RhB was selected for this study as a dye model of organic dyes pollutants. The morphology of the glass foams impregnated with TiO2 and WO3 was examined by 3D laser scanning microscopy and SEM microscopy. Additionally, physical and chemical properties of the samples were determined using FT-IR and Raman spectroscopy. The artificial solar light was provided by a solar simulator Sol 2A and 20 ml RhB aqueous solution with initial concentration of 0.0015 g L-1 was used for each sample for the photocatalytic experiments. The degradation of RhB was determined by monitoring the absorbance of RhB solution by UV-VIS spectroscopy for 2 hours, at every 10 minutes, subsequent to the adsorption-desorption equilibrium reached in dark conditions. Enhanced photocatalytic properties were obtained for the samples of glass foams coated with TiO2, with a maximum degradation of RhB of 92%, whereas the degradation of RhB in the presence of WO3 fixed on glass foams reached a maximum value of 58%. [ABSTRACT FROM AUTHOR]