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Abstract  

The effect of additives (CuO, MnO2 and TiO2) on the thermal decomposition kinetics of potassium metaperiodate (KIO4) to potassium iodate (KIO3) has been studied in air by thermogravimetry under isothermal conditions. Irrespective of whether p- or n-type, the metal oxides show only a little or no influence on the rate of the decomposition except for the small decrease when the oxide concentration is as high as 10 wt%. The rate law for the decomposition of KIO4 (Prout–Tompkins model) remained unaffected by the additives.

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Abstract  

The synthesis of cyanoferrates of quadrivalent metals and the sorption of caesium ions by these materials have been studied. It has been found that the compositions of the compounds and their properties are strongly influenced by the degree of hydrolysis of the metal. These is no sorption of caesium by Zr4+ and Th4+ cyanoferrates, while the compounds of oxygencontaining bivalent complex cations exhibit behaviour similar to that of the other bivalent metals. The sorption of caesium by (TiO)2R is govermed by an ion-exchange mechanism; with (ZrO)2R changes occur in the crystal lattice, and (ThO)2R exhibits a low affinity towards caesium.

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Abstract  

Two samples of the microporous titanosilicate ETS-10 synthesised by different preparation procedures were compared for their ability to take up uranium from aqueous solutions using a batch-type technique. The ETS-10 samples were synthesised using either TiO2 or TiCl3 as a titanium source. The uptake of uranium on the materials was compared by determining the distribution coefficient and percentage sorption as a function of contact time, uranium concentration, and sorbent concentration. It was found that the difference in the synthesis procedures of the materials had a significant influence on the uptake of uranium.

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Abstract  

The aim of this work is the synthesis and the characterization of a microporous material obtained from gels with titanium and silicon: NTS (titanosilicate). The structure of NTS zeotype is similar to that of AM-1 and JDF-L1 (titanosilicates). The synthesis were carried out with gels of composition: 3.5Na2O–yTiO2–4.48HCl–xSiO2–110H2O with 1.0≤x≤12.0 and 0.2≤y≤0.7. The temperature of reaction was 1902C. In most of the cases NTS was prepared in a pelletted form. NTS pellets are produced at TiO2 content higher than 0.3 moles and SiO2 comprised between 3 and 7. NTS in a powder form is produced for TiO2<0.3 and SiO2 between 3 and 5 moles. It describes crystallization field and the kinetic curves of the titanosilicate. The samples are characterized by X-ray diffraction (XRD), thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), nuclear magnetic resonance spectroscopy-high resolution solid state MAS 29Si-NMR, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) X-ray microanalysis.

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The intrinsic kinetics, unaffected by diffusional and mass transfer effects, of the air oxidation of Na2TiF6 and Na3TiF6 were determined by using a nonisothermal technique. The oxidation of these sodium fluorotitanates proceeds through two-step reactions involving the formation of oxyfluorotitanate, i.e. Na3TiOF5, as the intermediate. The oxidation rate shows a first-order dependence on the amount of the unreacted solids for each of the two-step reactions for both fluorotitanates. The activation energy for the further oxidation of Na3TiOF5 to a mixture of NaF + TiO2 was determined to be 52.4 kJ/mol and 55.3 kJ/raol for Na2TiF6 and Na3TiF6 as reactants, respectively.

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Abstract  

Degradation of ethylenediaminetetraacetic acid (EDTA) present in the liquid waste was demonstrated by photocatalytic oxidation route by using nanoparticles of anatase titania. Nano sized titania photocatalyst was synthesized using sol–gel method coupled with ultrasonication mode and characterized using X-ray diffraction, transmission electron microscope, BET, Fourier transform infrared spectroscopy and TG–DTA. A cylindrical photoreactor was employed for the degradation studies. Five milligram of the nano anatase TiO2 + 0.5 ml of 30% H2O2 were employed as catalysts for the degradation studies of 1,000 mg/L EDTA. EDTA degradation was followed by a complexometric titration method. Complete degradation of 1,000 mg/L EDTA could be achieved in 90 min and the photocatalytic efficiency of the synthesized titania photocatalyst was higher than that of P-25 TiO2 for EDTA degradation. The influence of pH on the degradation of EDTA follow the order acidic > neutral > alkaline. More than ten fold increases in the decontamination factors were obtained for the chemical precipitation step for the liquid waste containing degraded EDTA compared to liquid waste without EDTA degradation.

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Introduction TiO 2 and Fe 2 O 3 can be found in wide applications, such as catalysts [ 1 ] and gas sensors [ 2 , 3 ]. Recently, binary mixed oxides were reported to be good catalysts with improved photocatalytic properties

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Abstract  

A Ti–45.9Al–8Nb (at%) alloy with a lamellar structure (γ+α2) was oxidised in air at 700, 800, 850 and 900°C in isothermal and thermal cycling conditions. The reaction progress was followed by thermogravimetric measurements. In isothermal conditions the oxidation kinetics followed approximately a parabolic rate law and the rate constants ranged from about 10–12 kg2 m–4 s–1 at 700°C to 10–10 kg2 m–4 s–1 at 900°C. The oxide scales were built of Al2O3 and TiO2, the former being the main component of the outermost layer. The oxidation behaviour of Ti–45.9Al–8Nb was referred to a commercial titanium alloy, WT4 (Ti–6Al–1Mn), and selected oxidation-resistant alloys.

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Abstract  

The crystallization kinetics of some glass-ceramics obtained from Romanian (Şanoviţa) basalt has been studied in non-isothermal conditions using DTA technique. The activation energies of the crystallization processes were calculated using the isoconversional methods Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall. The results obtained show a dependence of the activation energy (E α) on the crystallized fraction (α) that proves the complex mechanism of the glass-ceramics crystallization process. It has been proved that the Johnson-Mehl-Avrami model cannot be applied for the studied glass-ceramics crystallization process. The effect of 2% TiO2 as nucleating agent upon the crystallization kinetics and upon the microstructure of the studied glass-ceramics was analyzed.

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Abstract  

The aim of this paper is to define the characteristics of crystalline phase ETS-10 obtained from gel with dodecyltrimethylammonium bromide, as an organic template. ETS-10 zeolites has been synthesised under hydrothermal conditions from gels of composition 5Na2O–3KF–TiO2–6.4HCl– xC12TMAB –7.45SiO2–197.5H2O (where x=0.0, 0.25, 0.55, 1.0 and 1.5) with dodecyltrimethylammonium bromide. The crystalline phases synthesised with organic salt have an exothermal peak at ca. 360°C, due to the degradation of organic entrapped in the porous structure. Physical-chemical properties of C12TMAB -ETS-10 are studied by XRD, SEM and thermal analyses.

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