Showing papers on "Sodium metavanadate published in 2007"

Degradation of Yttria-Stabilized Zirconia Thermal Barrier Coatings by Vanadium Pentoxide, Phosphorous Pentoxide, and Sodium Sulfate

Abstract: The presence of vanadium, phosphorus, and sodium impurities in petcoke and coal/petcoke blends used in integrated gasification combined cycle (IGCC) plants warrants a clear understanding of high-temperature material degradation for the development of fuel-flexible gas turbines. In this study, degradation reactions of free-standing air plasma-sprayed (APS) yttria-stabilized zirconia (YSZ) in contact with vanadium pentoxide (V2O5), phosphorus pentoxide (P2O5), and sodium sulfate (Na2SO4) were investigated at temperatures up to 1200°C. Phase transformations and microstructural development were examined using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Molten V2O5 reacted with solid YSZ to form zirconium pyrovanadate (ZrV2O7) at temperatures below 747°C. However, at temperatures above 747°C, molten V2O5 reacted with YSZ to form yttrium vanadate (YVO4). The formation of YVO4 led to the depletion of the Y2O3 stabilizer and deleterious transformation to the monoclinic ZrO2 phase. In addition, studies on YSZ degradation by Na2SO4 and a Na2SO4+V2O5 mixture (50–50 mol%) showed that Na2SO4 itself had no effect on the degradation of YSZ. However, in the presence of V2O5 at high temperatures, Na2SO4 forms vanadate compounds having a lower melting point such as sodium metavanadate (610°C), which was found to degrade YSZ by the formation of YVO4 at a relatively lower temperature of 700°C. P2O5 was found to react with APS YSZ by the formation of zirconium pyrophosphate (ZrP2O7) at all the temperatures studied. At temperatures as low as 200°C and as high as 1200°C, molten P2O5 was observed to react with solid YSZ to yield ZrP2O7, which led to the depletion of ZrO2 in YSZ (i.e., enrichment of Y2O3 in t′-YSZ) that promoted the formation of the fluorite-cubic ZrO2 phase.

Effects of vanadium(V) and/or chromium(III) on L-ascorbic acid and glutathione as well as iron, zinc, and copper levels in rat liver and kidney.

Abstract: This study investigated the selected parameters of the antioxidant system in liver and kidney after in vivo administration of vanadium and/or chromium in rats. Outbred 2-mo-old albino male Wistar rats received drinking water for 12 wk with either sodium metavanadate (SMV; group II); chromium chloride (Cr; group III); or sodium metavanadate and chromium chloride (SMV-Cr; group IV); and group I (control) received deionized water. Chronic treatment with V alone or in combination with Cr produced a significant increase in kidney relative weight. Further, giving rats V alone also led to a significant elevation in liver relative weight. An increase in hepatic Fe concentration and renal Zn content occurred after treatment with V or Cr, respectively. The rats coadministered V and Cr had significantly higher levels of Fe in liver and Zn in kidneys. Simultaneous administration of these two elements resulted in a significant decrease in renal L-ascorbic acid concentration. V given alone significantly decreased GSH content and GSH/GSSG ratio in liver and kidney as well as increased GSSG concentration in liver, whereas Cr alone produced a significant decrease in GSH content in kidney and GSH/GSSG ratio in both organs. In the SMV-Cr-treated group a significant decrease in renal GSH concentration and GSH/GSSG ratio in both organs occurred. A significant increase in liver GSSG content was also found. The observed significant changes in kidney GSH content and in GSH/GSSG ratio in both rat tissues after Cr might result from the pro-oxidant actions of this metal. Thus, oxidative stress, which is a major pathway for V-induced toxicity, might also be associated with Cr(III)-induced adverse effects in rats.

Vanadium-induced testicular toxicity and its prevention by oral supplementation of zinc sulphate.

Abstract: Transition metal vanadium has been shown to modulate the cellular redox potential and catalyze the generation of reactive oxygen intermediates. Since free radical production and lipid peroxidation are potentially important mediators in testicular physiology and pathophysiology, the present study was conducted to elucidate the vanadium-induced oxidative damages in rat testis and the ameliorative role of zinc sulphate against such adverse effects of vanadium. Adult male rats were dosed for 26 days with daily intraperitoneal injection of 0.4 mg V/kg body weight as sodium metavanadate. One group of rats was treated with zinc sulphate orally simultaneously with vanadium for 26 days, while the other group was treated with zinc sulphate alone. Changes in testicular and accessory sex organ weight, different varieties of germ cells at stage VII of spermatogenic cycle, epididymal sperm count, and enzymatic (Delta(5)3beta- HSD, 17beta- HSD, SOD, catalase), lipid peroxidation, and hormonal milieu were monitored. Vanadium treatment resulted in a significant increase in the testicular lipid peroxidation and caused a marked inhibition in the activities of antioxidant and steroidogenic enzymes. Histopathological examination revealed inhibition of spermatogenesis and the preferential loss of maturing and elongated spermatids. However, coadministration of zinc sulphate to vanadium-treated animals resulted in normalizing these parameters appreciably, emphasizing the therapeutic potentials of zinc. Taken together, the results suggest that an increase in free radical formation relative to loss of the antioxidant defense system during vanadium exposure may render testis more susceptible to oxidative damage, leading to their functional inactivation. However, zinc sulphate supplementation can be an effective antidote in the treatment of vanadium poisoning.

High-throughput assessment of inhibitor synergies on aluminum alloy 2024-T3 through measurement of surface copper enrichment

Abstract: The identification of new corrosion inhibition systems remains dependent on experimentation for screening and characterization. One approach for the acceleration of this discovery process is through the use of high-throughput methods. This paper examines the measurement of surface copper enrichment as a method for the rapid and high-throughput screening of corrosion inhibitors and their combinations for aluminum alloy 2024-T3 (AA2024-T3). Ninety-six AA2024-T3 wire electrodes were assembled in a reaction frame with 2-mL cells and exposed to 0.6 M sodium chloride (NaCl) containing 3.4 mM total inhibitor concentration adjusted to pH 7. Eleven single inorganic chemical species were evaluated for corrosion inhibition: sodium chromate (Na2CrO4), sodium metavanadate (NaVO3), cerium chloride (CeCl3), barium metaborate (BaB2O4), yttrium chloride (YCl3), sodium metatungstate (Na2WO4-3WO3), potassium phosphate (KH2PO4), lanthanum chloride (LaCl3), sodium metasilicate (Na2SiO3), sodium phosphate (Na2PO4), an...

Extraction of vanadium and molybdenum compound from refused materials containing vanadium and molybdenum etc. multiple elements

Abstract: Extraction of vanadium and molybdenum from waste materials is carried out by physically or chemically pre-treating for raw materials by recovered oil, leaching out at a certain pH value, generating soluble sodium metavanadate and sodium molybdate, removing impurities, filtering, solid-liquid separating, precipitating ammonium metavanadate by amine salt, filtering, drying, decomposing, tabletting by smelting furnace to obtain sheeted vanadic anhydride, precipitating ammonium metavanadate filtrate, pouring it into vanadium extraction tank, extracting by organic phase, cleaning by saturated organic phase, reversed extracting, concentrating and crystallizing. It has better vanadium recovery rate and quality and more product yield.

Study of anti ulcer activity of sodium metavanadate on alcohol and pylorus ligation induced gastric ulcers in rats

Abstract: The present study was designed to evaluate the effects of sodium metavanadate against experimentally-induced gastric ulcers. In an attempt to establish the antiulcer effect and its mechanism of action, sodium metavanadate (3, 5 mg/kg, i.p.) was studied in ethanol and pylorus ligation-induced gastric ulcer models. Sodium metavanadate significantly reduced ulcer index in both the ulcer models. Besides it showed significant reduction in total acid out put along with significant rise in total carbohydrates and mucin activity in gastric juice in pylorus ligation model. Therefore, it is suggested that sodium metavanadate possesses significant antiulcer activity. The probable mechanisms for its antiulcer effect can be attributed to decrease in acid secretion and increase in mucoprotective substances.

Method for oxidizing-converting-leaching vanadium from converter steelmaking extracted vanadium slag under pressure field

Abstract: The invention relates to a method to oxidation transform leached vanadium from converter steel-making vanadium slag under pressure field. It makes the product through adding converter steel making vanadium slag, oxidant and leaching agent into autoclave, controlling suitable converting temperature, pressure and reaction time, and directly conform the vanadium in slag into solution. The vanadium would be released through the vitriol breaking up ferrovanadium spinelle structure and react with oxidant to form vanadium sulfate acid radical solution or sodium metavanadate that could be dissolved in water, and the other gangue constituent would be remained in ore. The invention has the advantages of simple technology, high metal yield, easy to separate vanadium, and low consumption for agent, and little pollution, etc.