Kinetics of forward extraction of Ti(Ⅳ) from H2SO4 medium by P507 in kerosene using the single drop technique

The kinetics of forward extraction of Ti(Ⅳ) from H2SO4 medium by P507 in kerosene has been investigated using the single drop technique.10-5.07[TiO2+][H+]-1[NaHA2](o). Analysis of the rate expression reveals that the rate determining step is(TiO)2+(i)+ (HA2)-(i)(←→)spectively. The experimental negative △S± values indicate that the reaction step occurs via SN2 mechanism.     

Phase Equilibria in the System Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-CaO-CoO and Gibbs Energy of Formation of Ca<Subscript>3</Subscript>CoAl<Subscript>4</Subscript>O<Subscript>10</Subscript>

An isothermal section of the system Al₂O₃-CaO-CoO at 1500 K has been established by equilibrating 22 samples of different compositions at high temperature and phase identification by optical and scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy after quenching to room temperature. Only one quaternary oxide, Ca₃CoAl₄O₁₀, was identified inside the ternary triangle. Based on the phase relations, a solid-state electrochemical cell was designed to measure the Gibbs energy of formation of Ca₃CoAl₄O₁₀ in the temperature range from 1150 to 1500 K. Calcia-stabilized zirconia was used as the solid electrolyte and a mixture of Co + CoO as the reference electrode. The cell can be represented as: From the emf of the cell, the standard Gibbs energy change for the Ca₃CoAl₄O₁₀ formation reaction, CoO + 3/5CaAl₂O₄ + 1/5Ca₁₂Al₁₄O₃₃ → Ca₃CoAl₄O₁₀, is obtained as a function of temperature: /J mol⁻¹ (±50) = −2673 + 0.289 (T/K). The standard Gibbs energy of formation of Ca₃CoAl₄O₁₀ from its component binary oxides, Al₂O₃, CaO, and CoO is derived as a function of temperature. The standard entropy and enthalpy of formation of Ca₃CoAl₄O₁₀ at 298.15 K are evaluated. Chemical potential diagrams for the system Al₂O₃-CaO-CoO at 1500 K are presented based on the results of this study and auxiliary information from the literature.     

Evaluation of in vitro and in vivo tests for surface-modified titanium by H<Subscript>2</Subscript>SO<Subscript>4</Subscript> and H<Subscript>2</Subscript>O<Subscript>2</Subscript> treatment

Titanium is widely used as an implant material for artificial teeth. Furthermore, various studies have examined surface treatment with respect to the formation of a fine passive film on the surface of commercial titanium and its alloys and to improve the bioactivity with bone. However, there is insufficient data about the biocompatibility of implant materials in the body. The purpose of this study was to examine whether surface modification affects the precipitation of apatite on titanium metal. Specimens were chemically washed for 2 min in a 1∶1∶1.5 (vol.%) mixture of 48 %HF, 60%HNO₃ and distilled water. The specimens were then chemically treated with a solution containing 97%H₂SO₄ and 30%H₂O₂ at the ratio of 1∶1 (vol.%) at 40°C for 1h, and subsequently heat-treated at 400°C for 1h. All the specimens were immersed in HBSS with pH 7.4 at 36.5°C for 15d, and the surface was examined with TF-XRD, SEM, EDX and XPS. In addition, specimens of commercial pure Ti, with and without surface treatment, were implanted in the abdominal connective tissue of mice for 28 d. Conventional aluminum and stainless steel 316L were also implanted for comparison. An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a solution of H₂SO₄ and H₂O₂. The average roughness was 2.175 μm after chemical surface treatment. The amorphous titania was subsequently transformed into anatase by heat treatment at 400°C for 1h. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was 47.1μm in the chemically treated Ti, and 52.2, 168.7 and 101.9μm, respectively, in the untreated commercial pure Ti, aluminum and stainless steel 316L.     

The corrosion inhibition of Ti-alloy (VT-9) in mixture of H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-NaF by organic compounds

This investigation deals with corrosion behavior of high strength titanium alloy in concentrated sulphuric acid solution containing different concentrations (500, 1000, 1500 ppm) of fluoride ion (F⁻) using various organic compounds (MPA, L-OH, NFP) as inhibitor, potentiodynamically. The open circuit potential values noted before and after each experiment, varied appreciably. These values were negative before polarization but after completion of the experiment turned positive and remained stable over long period of time. It is observed that cathodic current density values increase with increasing cathodic potential (more negative) and fluoride ion. The values of cathodic Tafel slopes derived from the curves (∼110 − 140 mV/dec I) indicate hydrogen evolution reaction (h.e.r). The corrosion potential (E _corr) varied slightly with addition of inhibitors. The corrosion current densities (I _corr) increased with increasing fluoride ion concentration, but these values decreased appreciably when inhibitor (MPA) was used. SEM micrograph reveals reduction of pits in the presence of inhibitor (MPA). So this concludes that organic compound was used in this case acts as a good inhibitor. The article is published in the original.     

煤油体系中采用D2EHPA,EHEHPA,CYANEX 272从硫酸介质中萃取钒（IV）的机理及热力学（英文）

采用有机磷类萃取剂—D2EHPA,EHEHPA和CYANEX 272在煤油体系中从硫酸介质中萃取钒（IV）。考察溶液pH值、萃取剂浓度、钒离子浓度、温度对钒萃取性能的影响,并确定萃合物的组成。结果表明：随着水相pH值、萃取剂浓度和温度的升高,钒（IV）的分配比增大。D2EHPA可以在更低的pH值下萃取钒（IV）,表明其对钒的萃取能力大于EHEHPA和CYANEX 272。萃取机理研究结果表明：3种有机磷类萃取剂对钒的萃取均符合离子交换机理,在低pH值条件下萃合物组成为VOR2（HR）2,在高pH值下萃合物组成为VOR2（R表示萃取剂）。     

Kinetics of cerium(IV) and fluoride extraction from sulfuric solutions using bifunctional ionic liquid extractant (Bif-ILE) [A336][P204]

The extraction kinetics of Ce(IV) and Ce(IV)-F^? mixture systems from sulfuric solutions to n-heptane solution containing Bif-ILE [A336][P204] ([trialkylmethylammonium][di-2-ethylhewanxylphosphinate]) with a constant interfacial area cell with laminar flow were studied, just to elucidate the extraction mechanism and the mass transfer models. The data were analyzed in terms of pseudo-first-order constants. The effects of stirring speed, specific interfacial area and temperature on the extraction rate in both systems were discussed, suggesting that the extractions were mixed bulk phases-interfacial control process. Supported by the experimental data, the corresponding rate equations for Ce(IV) extraction system and Ce(IV)–F^? mixture extraction system were obtained. The experimental results indicated the rate-controlling step. The kinetics model was deduced from the rate-controlling step and consistent with the rate equation.     

Influences on the H<Subscript>2</Subscript>-sorption properties of Mg of Co (with various sizes) and CoO addition by reactive grinding and their thermodynamic stabilities

We attempted to improve the H₂-sorption properties of Mg by mechanical grinding under H₂ (reactive grinding) with Co (with various particle sizes) and with CoO. The thermodynamic stabilities of the added Co and CoO were also investigated. CoO addition has the best influence and addition of smaller particles of Co (0.5–1.5 μm) has a better effect than the addition of larger particles of Co on the H₂-sorption properties of Mg. The activated Mg+10 wt.% CoO sample has about 5.54 wt% hydrogen-storage capacity at 598 K and the highest hydriding rate, showing an H_a value of 2.39 wt.% after 60 min at 598 K, 11.2 bar H₂. The order of the hydriding rates after activation is the same as that of the specific surface areas of the samples. The reactive grinding of Mg with Co or CoO and hydriding-dehydriding cycling increase the H₂-sorption rates by facilitating nucleation of magnesium hydride or α solid solution of Mg and H (by creating defects on the surface of the Mg particles and by the additive), and by making cracks on the surface of Mg particles and reducing the particle size of Mg, thus shortening the diffusion distances of hydrogen atoms. The cobalt oxide is stable even after 14 hydriding cycles at 598 K under 11.2 bar H₂. Discharge capacities are measured for the sampple Mg+10 wt.%CoO and Mg+10wt.%Co (0.5−1.5 μm) with good hydrogen-storage properties.