Rutile

Titanium (Ti) is the ninth most abundant element on earth. The titanium mineral ores are widely distributed in different parts of the world. The two main ores of titanium include rutile (TiO2) and ilmenite (FeO.TiO2). It is aimed to provide the readers with an insight to the main processes currently employed to extract and recover titanium tetrachloride (TiCl4) from different titanium ores. Due to the crucial importance of TiCl4 catalyst in the synthesis and polymerization of polyolefins, the present work examines the literature and developments made in the processing of ilmenite and rutile ores for the extraction of TiCl4. The attention has been paid to the chlorination processes and the main parameters affecting the recovery of TiCl4. Different approaches developed to date are reviewed. Different processes, reaction mechanisms and conditions as well as the kinetic models developed for extraction and purification of TiCl4 in fluidized bed reactors are also reviewed. A literature survey on the combined fluidized bed reactor systems developed for achieving a high-grade synthetic rutile via selective chlorination of low-grade titanium ores having high metal oxides content such as magnesium oxide (MgO) and calcium oxide (CaO) is also reported. Different strategies adopted to avoid agglomeration process during the extraction process are discussed too.

Abstract Titanium dioxide photocatalysts co-modified with iron and nitrogen (Fe–N–TiO2) were produced via hydrothermal method using iron(III) nitrate nonahydrate and urea as iron and nitrogen sources, respectively. The effects of different dopant concentrations were investigated. The modified TiO2 catalysts were characterized for phase composition, surface morphology, specific surface area, degree of doping, charge states and bandgap energy combining various techniques. The results showed that controlled iron and nitrogen concentrations significantly altered the physicochemical properties of the catalysts. The photocatalysts displayed the anatase/rutile/brookite crystal phase mixture. The rutile and brookite phase contents increased with increasing iron content. On the other hand, increasing nitrogen content inhibited the formation of rutile and brookite phases and the catalysts displayed predominantly the anatase phase. High iron and low nitrogen contents led to the highest BET surface areas. The surface morphology changed from nanorice to spherical shape with increasing iron content. The bandgap energy of all Fe–N–TiO2 samples was in the range 2.7–3.1 eV, being lower than that of undoped TiO2 and pure anatase phase. Nitrogen was incorporated into the TiO2 lattice on interstitial positions (Ti–O–N). The iron, substituting some Ti4+ in the lattice was presented in Fe2+ and Fe3+ oxidation state, as confirmed by XANES measurements. The photocatalytic degradation of antibiotic ciprofloxacin was performed under visible light using a LED illumination source and nearly 70 % of the antibiotic was removed in 6 h by using the most active sample (2.5 %N–1.5 %Fe). As verified by photoluminescence results, the iron and nitrogen dopants synergistically enhanced the charge separation, since they promoted the formation of the different TiO2 phases.

Hydrogenated TiO<sub>2</sub> (H-TiO<sub>2</sub>) is touted as a viable visible light photocatalyst. We report a systematic study on the thermal stability of H-implanted TiO<sub>2</sub> using nuclear reaction analysis (NRA), Rutherford backscattering spectrometry, ultraviolet photoelectron spectroscopy, and X-ray photoelectron spectroscopy. Protons (40 keV) implanted at a ∼2 atom % level within a ∼120 nm wide profile of rutile TiO<sub>2</sub>(110) were situated ∼300 nm below the surface. NRA revealed that this H-profile broadened toward the surface after annealing at 373 K, dissipated out of the crystal into vacuum at 473 K, and was absent within the beam sampling depth (∼800 nm) at 523 K. Photoemission showed that the surface was reduced in concert with these changes. Similar anneals had no effect on pristine TiO<sub>2</sub>(110). The facile bulk diffusivity of H in rutile at low temperatures, as well as its interfacial activity toward reduction, significantly limits the utilization of H-TiO<sub>2</sub> as a photocatalyst

In this research we report the gas-sensing properties of TiO2-x/TiO2-based hetero-structure, which was ‘self-heated’ by current that at constant potential passed through the structure. Amperometric measurements were applied for the evaluation of sensor response towards ethanol, methanol, n-propanol and acetone gases/vapours. The sensitivity towards these gases was based on electrical resistance changes, which were determined by amperometric measurements of current at fixed voltage applied between Pt-based contacts/electrodes deposited on the TiO2-x/TiO2-based layer. X-ray diffraction (XRD) analysis revealed the formation of TiO2-x/TiO2-based hetero-structure, which is mainly based on Ti3O5/TiO2 formed during the hydro-thermal oxidation-based sensing-layer preparation process. Additionally, photoluminescence and time-resolved photoluminescence decay kinetics-based signals of this sensing structure revealed the presence of TiO2 mainly in the anatase phase in the TiO2-x/TiO2-based hete...

In this research we report the gas-sensing properties of TiO2-x/TiO2-based hetero-structure, which was ‘self-heated’ by current that at constant potential passed through the structure. Amperometric measurements were applied for the evaluation of sensor response towards ethanol, methanol, n-propanol and acetone gases/vapours. The sensitivity towards these gases was based on electrical resistance changes, which were determined by amperometric measurements of current at fixed voltage applied between Pt-based contacts/electrodes deposited on the TiO2-x/TiO2-based layer. X-ray diffraction (XRD) analysis revealed the formation of TiO2-x/TiO2-based hetero-structure, which is mainly based on Ti3O5/TiO2 formed during the hydro-thermal oxidation-based sensing-layer preparation process. Additionally, photoluminescence and time-resolved photoluminescence decay kinetics-based signals of this sensing structure revealed the presence of TiO2 mainly in the anatase phase in the TiO2-x/TiO2-based hete...