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Query: EC:4.1.2.42 (DTA)
 1,693 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Arsenic adsorption was carried out on simple materials such as goethite and amorphous iron hydroxide, and more complex matrices such as clay pillared with titanium(IV), iron(III), and aluminum(III). These matrices were synthesized from a bentonite whose montmorillonitic fraction was pillared according to optimized parameters. These sorbents were characterized by various methods: XRD, FTIR, BET, DTA/TGA, surface acidity, and zetametry. Elimination of arsenite and arsenate as a function of pH was studied. Arsenate elimination was favored at acidic pH, whereas optimal arsenite elimination was obtained at 4<pH<9. For pH values above 10, the pillared clays were damaged and elimination decreased. Equilibrium time and adsorption isotherms were also determined for arsenite and arsenate at each matrix auto-equilibrium pH. Amorphous iron hydroxide had the highest adsorption capacities both towards arsenate and arsenite. Adsorption capacities of goethite and iron- and titanium-pillared clays toward arsenate were similar, but those toward arsenite were different. Desorption experiments from the various matrices were carried out. Iron- and titanium-pillared clays showed a desorption capacity above 95% and around 40% respectively, but no desorption rate could be obtained for iron (hydr)oxides as they were damaged during the process.
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PMID:Arsenic adsorption onto pillared clays and iron oxides. 1270 67

The preparation and structural characterization of the novel polyoxoanion [(alpha-1,2,3-P(2)W(15)Ti(3)O(62))(4)[mu(3)-Ti(OH)(3)](4)Cl](45-) (1 a; abbreviated to [TiO(6)](16); FW approximately 16 000) which consists of four tri-Ti(IV)-1,2,3-substituted alpha-Dawson substructures, four Ti(OH)(3) bridging groups, and one encapsulated Cl(-) ion, are described. A water-soluble, all-inorganic composition compound of the tetrameric Ti-O-Ti-bridged anhydride form, Na(x)H(45-x)[1 a].y H(2)O (1; x=16-19, y=60-70), which was afforded by the reaction of the tri-lacunary Dawson polyoxotungstate Na(12)[B-alpha-P(2)W(15)O(56)].19 H(2)O with an excess of TiCl(4) in aqueous solution, was obtained as analytically pure, homogeneous colorless crystals. Single-crystal X-ray structure analysis revealed that 1 a was an inorganic, giant "tetrapod"-shaped molecule (inscribed to a sphere with a diameter of approximately 32 A) with approximately T(d) symmetry, in which the 16 edge- and/or corner-shared TiO(6) octahedra were contained. This number of TiO(6) octahedra was larger than that found in other titanium(IV)-substituted polyoxotungstates. Complex 1 was characterized by complete elemental analysis, TG/DTA, FTIR, UV/Vis absorption, and solution ((31)P and (183)W) NMR spectroscopy. The longest wavelength band in the UV/Vis absorption spectra of 1 in water was attributed to the O-->Ti(IV) ligand-to-metal charge-transfer (LMCT) transition: the wavelength of the LMCT band increased linearly as the number of TiO(6) octahedra contained in the Keggin and Dawson polyoxoanions increased. The Ti(n) chromophores formed in the Keggin and Dawson polyoxotungstates are water-soluble analogues of solid TiO(2) or SrTiO(3) as light-semiconductors and photocatalysts.
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PMID:Tetrameric, trititanium(IV)-substituted polyoxotungstates with an alpha-Dawson substructure as soluble metal-oxide analogues: molecular structure of the giant "tetrapod" [(alpha-1,2,3-P2W15Ti3O62)4[mu3-Ti(OH)3]4Cl]45-. 1295 93

Tetravalent metal phosphates (M=Zr, Ti, and Sn) were prepared and characterized by XRD, surface properties, and TG-DTA. The cation exchange and sorption behavior of these metal phosphates toward transition metal ions such as Cu(2+), Co(2+), and Ni(2+) have been studied comparatively as a function of temperature and concentration. The adsorption process was found to increases with increase in temperature and concentration. The selectivity order for alpha-titanium and alpha-tin phosphates is Cu(2+)>Co(2+)>Ni(2+), whereas for alpha-zirconium phosphate it is Cu(2+)>Ni(2+)>Co(2+). The ion exchange capacity of alpha-titanium phosphate is greater than those of other phosphates, which is explained on the basis of the surface behavior, disorderness of the system, degree of hydrolysis of incoming guest adsorbate metal ions, and structural steric hindrance of the exchangers during adsorption and sorption. The distribution coefficient, Gibbs free energy, enthalpy, and entropy values indicate that the ion-exchange processes are spontaneous.
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PMID:A comparative study on textural characterization: cation-exchange and sorption properties of crystalline alpha-zirconium(IV), tin(IV), and titanium(IV) phosphates. 1469 11

A simple external gelation process, taking full advantage of the gelation features of titanium and silica, was developed to prepare TiO2-SiO2 mixed gel spheres suitable for strontium adsorption. The source solutions used for the process were prepared from different mixtures of 1M TiCl4 and 1M Na2SiO3 solutions and converted into droplets in a gelation column. The suitable spheres for strontium adsorption were obtained using a hexone (methyl isobutyl ketone) solution as the drop formation medium and ammonia as the gelling agent. The mixed oxide gels were identified and characterized by DTA/TGA, FTIR and XRD analysis. The parameters affecting the strontium adsorption, such as weight ratio of TiO2, pH, temperature, shaking time and selectivity towards competing ions were investigated. Sorption data have been interpreted in terms of Freundlich, Langmuir and Dubinin-Radushkevich equations. Thermodynamic parameters for the sorption system have been determined at four different temperatures. The value of DeltaH degrees =39.553 kJ/mol and DeltaG degrees =-16.687 kJ/mol at 296 K prove that the sorption of strontium on mixed oxide gel is an endothermic and a spontaneous process.
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PMID:Preparation of TiO2-SiO2 mixed gel spheres for strontium adsorption. 1581 74

The preparation and structural characterization of a novel Ti-O-Ti bonding complex constructed in the mono-lacunary alpha-Keggin polyoxometalate (POM), are described. The water-soluble, crystalline complex with a formula of K5H2[[{Ti(OH)(ox)}2(micro-O)](alpha-PW11O39)] x 13H2O 1 was prepared in 30.2% (0.60 g scale) yield in a 1 : 3 molar-ratio reaction of the tri-lacunary species of alpha-Keggin POM, Na9[A-PW9O34] x 19H2O, with the titanium(IV) source, K2TiO(ox)2 x 2H2O (H2ox = oxalic acid), in HCl-acidic solution (pH 0.08), and characterized by complete elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), FTIR, solution (31P, 183W, 1H and 13C) NMR spectroscopy and X-ray crystallography. The complex was also obtained in 47.6% (0.81 g scale) yield in a 1 : 2 molar-ratio reaction of the mono-lacunary Keggin POM, K7[PW11O39] x 10H2O, with the anionic titanium(IV) complex under acidic conditions. The molecular structure of [[{Ti(OH)(ox)}2(micro-O)](alpha-PW11O39)]7- 1a, was successfully determined. This POM in the solid state is composed of one host (mono-lacunary site) and two guests (two octahedral Ti groups), in contrast to most titanium (IV)-substituted POMs consisting of one host and one guest. On the other hand, the 31P NMR measurements revealed that in aqueous solution this POM was present under a dissociation equilibrium which depends upon both temperature and pH.
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PMID:Novel Ti-O-Ti bonding species constructed in a metal-oxide cluster. 1647 Oct 56

A new titanium(IV) oxide-hectorite nanofilm photocatalyst was prepared on quartz slides. It was evaluated in the photooxidation of dibenzothiophene (DBT) in nonpolar organic solution (tetradecane), as a model for diesel fuel. A removal regimen was developed consisting of catalytic photooxidation followed by adsorption of products on silica gel. Photooxidation of DBT was performed with and without catalyst, at 254 and 300 nm. Comparison was made with a commercially available TiO(2) catalyst, Degussa P25. The catalyst was analyzed by nitrogen adsorption, XRD, SEM, and TGA-DTA. DBT concentrations were measured by HPLC and UV spectrophotometry. Preliminary qualititative analysis of products was performed by UV and HPLC. Results indicated that the outlined process was effective in reducing sulfur levels to below 10 ppm sulfur.
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PMID:Photooxidation of dibenzothiophene on TiO(2)/hectorite thin films layered catalyst. 1660 Feb 76

Biomaterials and tissue engineering technologies are becoming increasingly important in biomedical practice, particularly as the population ages. Cellular responses depend on topographical properties of the biomaterial at the nanometer scale. Structures on biomaterial surfaces are used as powerful tools to influence or even control interactions between implants and the biological system [; ]. The influence of nanometer sized surface structures on osteoblastlike cell interactions was tested with niobium oxide coatings on polished titanium slices (cp-Ti grade 2). The aim of the study was to investigate the influence of nanoscopic surface structures on osteoblast interactions in order to support collagen I production and cell adhesion. The coatings were done by means of the sol-gel process. The surface structure was adjusted by annealing of the metaloxide ceramic coatings due to temperature depended crystal growth. The applied annealing temperatures were 450, 550 and 700 degrees C for 1 h, corresponding to Ra-numbers of 7, 15 and 40 nm. The surfaces were characterized by means of AFM, DTA/TG, diffractometry and white light interferometry. The cell reactions were investigated concerning adhesion kinetics, migration, spreading, cell adhesion, and collagen I synthesis. The smooth surface (Ra=7 nm) resulted in the fastest cell anchorage and cell migration. The closest cell adhesion was reached with the surface structure of Ra=15 nm. The roughest surface (Ra=40 nm) impedes the cell migration as well as a proper spreading of the cells. The best results concerning cell adhesion and spreading was reached with an intermediate surface roughness of Ra=15 nm of the niobium oxide coating on cp-titanium slices.
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PMID:Biomimetic implant coatings. 1682 42

The preparation and structural characterization of a novel Ti-O-Ti bonding complex constructed in a dilacunary alpha-Keggin polyoxometalate (POM), [[{Ti(ox)(H2O)}4(mu-O)3](alpha-PW10O37)](7-) (H2ox = oxalic acid) (1a), are described. The water-soluble, crystalline complex with a formula of K6H[1a].0.5KCl.10H2O (1p) was prepared as the bulk sample in 28.0% (0.51 g scale) yield in a 1:4 molar-ratio reaction of the dititanium(IV)-substituted, dimeric form of an alpha-Keggin POM, K10[(alpha-1,2-PW10Ti2O39)2].18H2O, with the titanium(IV) source K2[TiO(ox)2].2H2O in HCl-acidic solution (pH 0.08). Prior to formation of 1p, the KCl-free crystalline compound (1c) obtained was characterized with X-ray crystallography. The compound 1p was unequivocally characterized with complete elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), FTIR, and solution (31P, 183W, and 13C) NMR spectroscopy. The molecular structure of 1a was determined. The POM 1a in the solid state was composed of the four octahedral Ti groups (four guests), i.e., the two Ti-O-Ti groups linked with the mu-O atom, incorporated to the two adjacent, octahedral vacant sites (two hosts) in the dilacunary Keggin POM. The formation of 1a, as well as the recently found POM [{Ti(ox)(H2O)}2(mu-O)](alpha-PW11O39)](5-) (2a), was strongly dependent on the reaction with [TiO(ox)2](2-), i.e., the anionic titanium(IV) complex as the titanium(IV) source. The POM 1a is contrasted to most titanium(IV)-substituted POMs consisting of a combination of a monolacunary site (one host) and an octahedral Ti group (one guest) and also contrasted to 2a as a combination of a monolacunary site (one host) and two octahedral Ti groups or a Ti-O-Ti group (two guests).
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PMID:Novel Ti-O-Ti bonding species constructed in a metal-oxide cluster: reaction products of bis(oxalato)oxotitanate(IV) with the dimeric, 1,2-dititanium(IV)-substituted Keggin polyoxotungstate. 1699 5

A new glass electrolyte formed by constant amounts of titanium oxide (TiO2) and various amount of phosphotungstic acid (PWA) doped P2O5-SiO2 is prepared using the sol-gel process. The structural formation is confirmed by Fourier infrared spectroscopy (FTIR) and from thermogravimetric and differential thermal analysis (TG/DTA) measurements, the glasses display good thermal stability. Further characterisation is undertaken by N2 adsorption/desorption measurements, proton conductivity and hydrogen permeability analyses and a H2/O2 fuel cell test is also performed. The glass materials with large pores and specific surface area are suitable for use as the electrolyte in H2/O2 fuel cells. The effect of TiO2 processing with constant amount of PWA in phosphosilicate glasses, is investigated and discussed. The hydrogen permeability is 1.57x10(-11) mol cm(-1) s(-1) Pa(-1) at 110 degrees C for 0.8 mm thick glass; a power density of 46.3 mW cm(-2) at 125 mA cm(-2) and a current density of 175 mA cm(-2) is obtained (T=28 degrees C, relative humidity).
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PMID:Development of new glass composite membranes and their properties for low temperature H2/O2 fuel cells. 1787 56

Hydroxyapatite (HAp) is commonly used to coat titanium alloys (Ti-6Al-4V) for orthopedic implants. However, their poor adhesion strength and insufficient long-term stability limit their application. Novel sphene (CaTiSiO5) ceramics possess excellent chemical stability and cytocompatibility. The aim of this study is to use the novel sphene ceramics as coatings for Ti-6Al-4V. The sol-gel method was used to produce the coatings and the thermal properties, phase composition, microstructure, thickness, surface roughness and adhesion strength of sphene coatings were analyzed by differential thermal analysis-thermal gravity (DTA-TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), atom force microscopy (AFM) and scratch test, respectively. DTA analysis confirmed that the temperature of the sphene phase formation is 875 degrees C and XRD analysis indicated pure sphene coatings were obtained. A uniform structure of the sphene coating was found across the Ti-6Al-4V surface, with a thickness and surface roughness of the coating of about 0.5-1 microm and 0.38 microm, respectively. Sphene-coated Ti-6Al-4V possessed a significantly improved adhesion strength compared to that for HAp coating and their chemical stability was evaluated by testing the profile element distribution and the dissolution kinetics of calcium (Ca) ions after soaking the sphene-coated Ti-6Al-4V in Tris-HCl solution. Sphene coatings had a significantly improved chemical stability compared to the HAp coatings. A layer of apatite formed on the sphene-coated Ti-6Al-4V after they were soaked in simulated body fluids (SBF). Our results indicate that sol-gel coating of novel sphene onto Ti-6Al-4V possessed improved adhesion strength and chemical stability, compared to HAp-coated Ti-6Al-4V prepared under the same conditions, suggesting their potential application as coatings for orthopedic implants.
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PMID:Novel sphene coatings on Ti-6Al-4V for orthopedic implants using sol-gel method. 1818 36


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