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Abstract  

A novel adsorbent, TiO2/eggshell composite, was synthesized by sol–gel method, and characterized by XRD and FTIR. The removal of 60Co(II) from aqueous solution by TiO2/eggshell was studied as a function of contact time, pH, ionic strength, foreign ions, humic substances and temperature. The results indicated that the sorption of 60Co(II) on TiO2/eggshell was strongly dependent on pH and ionic strength. The Langmuir, Freundlich and D-R models were applied to simulate the sorption of 60Co(II) at temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH 0, ΔS 0, ΔG 0) calculated from the temperature dependent sorption isotherms indicated that the sorption process of 60Co(II) on TiO2/eggshell was endothermic and spontaneous. At low pH, the sorption of 60Co(II) was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. TiO2/eggshell composites have good potentialities for cost-effective disposal of 60Co(II) bearing wastewaters.

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Abstract  

A microcomposite powder in the system TiO2—ZrO2 as a precursor of zirconium titanate (ZT) materials has been studied by thermal methods (DTA-TG) and X-ray diffraction (XRD). The microcomposite powder has been prepared by chemical processing of crystalline TiO2 (rutile, 10 mass% anatase),as inner core, coated with in situ precipitated amorphous hydrated zirconia gel, asouter core. The morphology and chemical composition of the resultant powders has been examined by SEM-EDX (Scanning electron microscopy-energy dispersive X-ray spectroscopy). Thermal behaviour of the microcomposite powder was reported, showing the dehydration and dehydroxylation of the zirconia gel, the crystallization into metastable cubic/tetragonal zirconia at temperatures 400—470°C, and the feasibility of preparing ZT powder materials by progressive reaction of TiO2 and ZrO2 at higher temperatures (1400°C).

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Abstract  

Electrical conductivity and Seebeck voltage developed in thermally pretreated and -irradiated TiO2 was measured as a function of temperature. The conversion of n-type TiO2 into p-type and vice versa observed after irradiation was explained in terms of ionization of Ti3+ donors and lattice O= species, subsequent trapping of carriers in adsorbed oxygen and further formation of p-type inversion layer on the oxide surface during irradiation. The sign of the EMF of the electrochemical Ag/Ag+ concentration cell by the addition of heated and -irradiated TiO2 in one of the compartment of the cell was found to be opposite to that due to the addition of the corresponding heated but non-irradiated oxide sample.

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Journal of Thermal Analysis and Calorimetry
Authors:
Maria Crişan
,
Ana Brăileanu
,
D. Crişan
,
Mălina Răileanu
,
N. Drăgan
,
Diana Mardare
,
V. Teodorescu
,
Adelina Ianculescu
,
Ruxandra Bîrjega
, and
M. Dumitru

Abstract  

Among the great number of sol-gel materials prepared, TiO2 holds one of the most important places due to its photocatalytic properties, both in the case of powders and coatings. Impurity doping is one of the typical approaches to extend the spectral response of a wide band gap semiconductor to visible light. This work has studied some un-doped and Pd-doped sol-gel TiO2 nanopowders, presenting various surface morphologies and structures. The obtained powders have been embedded in vitreous TiO2 matrices and the corresponding coatings have been prepared by dipping procedure, on glass substrates. The relationship between the synthesis conditions and the properties of titania nanosized materials, such as thermal stability, phase composition, crystallinity, morphology and size of particles, and the influence of dopant was investigated. The influence of Pd on TiO2 crystallization both for supported and unsupported materials was studied (lattice parameters, crystallite sizes, internal strains). The hydrophilic properties of the films were also connected with their structure, composition and surface morphology. The methods used for the characterization of the materials have been: simultaneous thermogravimetry and differential thermal analysis, powder X-ray diffraction, electron microscopy (TEM, SAED) and AFM.

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The thermal decomposition of sodium nitrite or nitrate pre-adsorbed upon TiO2 surfaces has been investigated by employing several techniques as infrared spectroscopy (IR) and temperature programmed desorption in conjunction with mass spectrometry analysis (TPD-MS) to study the features observed during these thermal decompositions. Differential thermal analysis (DTA) in combination with X-ray diffraction analysis (XRD) were used to investigate the possibility of a solid state chemical reaction between the solid products originated from the thermal decomposition of the pre-adsorbed species and the TiO2. On the basis of our results, various characteristic features of these thermal decomposition reactions will be discussed.

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Abstract  

The influence of perchloric acid and hydrogen peroxide concentrations on the elution rates of vanadium and titanium from Dowex-50W X 8 resin was studied. The amounts of perchloric acid and of hydrogen peroxide were adjusted to provide an optimum eluent for the separation of vanadium from the irradiated titanium (TiO2) target.

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Abstract  

Hydrogen gas (H2) was produced by gamma-irradiation of pure water in the presence of various TiO2 catalysts. Most catalysts used in this work largely enhanced the radiolytic decomposition of water and subsequent production of H2. The different activity of catalysts was characterized by X-ray diffraction (XRD) patterns and by electron paramagnetic resonance (EPR) spectra. The addition of methanol as a sacrificing agent further increased the H2 production by scavenging hydroxyl radicals and the scavenging activity was directly identified using an EPR/spin-trapping technique. Among the catalysts studied, nanosized TiO2 (nTiO2) showed an excellent activity in the production of H2. Furthermore, the addition of EDTA instead of methanol largely increased the H2 production. This is quite promising since waste compounds such as EDTA can be removed with concomitant H2 production

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Abstract  

The characterization of different sized TiO2 (25 nm, 80 nm, and 155 nm) was carried out by transmission electron microscopy (TEM) and the micro-distributions of TiO2 in the olfactory bulb of mice after nasal inhalation were investigated by microbeam SRXRF mapping techniques. The results show that TiO2 particles can be translocated to the olfactory bulb through the olfactory nerve system after inhalation. The distributions of Fe, Cu, and Zn in the olfactory bulb were also studied.

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Abstract  

The preparation of rutile type solid solutions in (TiO2)x -(RuO2)1−x system in the 0≤x ≤0.7 concentration range is described. The single phase solid solutions are formed by controlled nanocrystallization of amorphous gels prepared by the sol-gel method. The kinetics of this crystallization process has been analyzed. It was found that the crystallization does not correspond to the Johnson-Mehl-Avrami model and it can be described by the two-parameter Šestk-Berggren kinetic model.

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Abstract  

The crystallization of K2O·TiO2·3GeO2 glass under non-isothermal condition was studied. In powdered glass with particle sizes less than 0.15 mm, surface crystallization was dominant and an activation energy of crystal growth of E a,s=327±50 kJ mol−1 was calculated. In the size range 0.15 to 0.45 mm, both surface and volume crystallization occurred. For particle sizes >0.45 mm, volume crystallization dominated with spherulitic morphology of the crystals growth and E a,v=359±64 kJ mol−1 was calculated.

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