Abstract TiO2 immobilized in Sepiolite (TiO2/Sep) was successfully prepared by the sol-gel technique, with titanium isopropoxide as the precursor for the formation of TiO2 in the anatase phase calcined at 400 °C. The prepared samples were characterized by X-ray diffraction, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy coupled to energy dispersive spectroscopy, and thermogravimetric analysis. The results showed that TiO2/Sep structure was identified in all characterizations, showing the specific peaks, bands, mass loss, and morphology after the impregnation process. Photocatalytic experiments were performed under UV irradiation with various photocatalyst concentrations and pH effects in the reaction. The prepared samples presented 72% photocatalytic efficiency for eosin (EA) dye discoloration after 150 min under UV light. This efficiency was attributed to the radicals generated from the TiO2 and the high specific surface area, showing that TiO2/Sep is promising candidate in the degradation of organic pollutants.

ABSTRACT Titanate nanotubes (TiNTs) with the chemical composition Na2Ti3O7.nH2O (NaTiNT) were obtained through a hydrothermal method in highly alkaline medium. Protonated titanates nanotubes (H-TiNTs), with the composition H2Ti3O7.nH2O, were prepared by ion exchange reaction through a suspension of Na2Ti3OγnH2O nanotubes in HCl medium, promoting the exchange of Na+ ions by H+. Both Na2Ti3O7.nH2O and H2Ti3O7.nH2O products, as well the TiO2 used as raw material for the nanotubes processing, were used as starting material for the solar cells photoelectrodes sensitized using mesoporphyrin extracted from a precursor of cashew nut shell. Exposing the NaTiNT sample to solar radiation of 1258 W/m2, a short-circuit current density (ISC) of 13 µA/cm2 and an open-circuit voltage (VOC) of 370 mV were registered and, a current density of 7.6 µA/cm2 and a voltage of 256 mV for the prototype cell based on H-TiNTs. A current density of 1.1 µA/cm2 and an open-circuit voltage of 1.6 mV were obtained for the cell using TiO2 as electrode.

This research used the "cathodic cage (CC)" technique for TiO2 film deposition on duplex stainless steel substrate. This technique uses a multiple hollow cathode effect. Duplex stainless steel substrates were treated at temperatures of 300°C, 350°C and 400°C, giving a temperature value ratio (Ts/Tm) of 0.27 to 0.31 (Ts being the substrate temperature and Tm the melting temperature of the deposited material). Treatment times of 1, 2 and 4 hours were administered and polycrystalline TiO2 films were obtained. The films were analyzed by optical microscopy (OM), X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). During analysis, the formation of uniform films and the possibility of controlling the TiO2 phase were observed. It was also shown that with longer treatment times and higher temperatures the rutile phase predominates. For treatment times of 4 hours at all temperatures, the rutile structure was present. With treatment times of less than 4 hours, anatase was present. In addition, results showed that this simple, low cost technique can be an alternative method for depositions of TiO2 films, with the advantage of high levels of control over porosity, thickness and phase composition (anatase and rutile).