Vanadium Absorption Research Articles

Flux enhancement with titanium or vanadium oxides addition for superior submerged arc welding of HSLA steel plates

A high-strength low-alloy (HSLA) steel plate of 10 mm thickness underwent submerged arc welding with enhanced fluxes containing additional titanium oxide (TiO2) or vanadium oxide (V2O5). The addition of TiO2 led to the development of a finer acicular ferrite structure but coarsening the carbide and martensite/austenite (M/A) constituents, which marginally improved the hardness, tensile strength, and ductility of weld metal. Conversely, incorporating V2O5 facilitated a substantial vanadium absorption (0.7 wt. %) in the weld metal, giving rise to a distinctive acicular microstructure less reliant on ferrite nucleation at non-metallic inclusions than conventional acicular ferrite. The distinctive microstructure, unique to vanadium steels, combined lath bainite with irregularly shaped granular bainite. The resultant dual-mode bainitic structure, coupled with a more uniform distribution of refined microphase constituents, outperformed the conventional acicular ferrite, delivering more than 20% and 13% improvements in yield and tensile strengths respectively, as evidenced by transverse tensile tests on the weld metals.

Effects of State of Charge on the Physical Characteristics of V(IV)/V(V) Electrolytes and Membrane for the All Vanadium Flow Battery

The VO2+/VO2+ redox couple commonly employed on the positive terminal of the all-vanadium redox flow battery was investigated at various states of charge (SOC) and H2SO4 supporting electrolyte concentrations. Electron paramagnetic resonance was used to investigate the VO2+ concentration and translational and rotational diffusion coefficient (DT, DR) in both bulk solution and Nafion membranes. Values of DT and DR were relatively unaffected by SOC and on the order of 10−10 m2s−1. Cyclic voltammetry measurements revealed that no significant changes to the redox mechanism were observed as the state of charge increased; however, the mechanism does appear to be affected by H2SO4 concentration. Electron transfer rate (k0) increased by an order of magnitude (10−6 ms−1 to 10−8 ms−1) for each H2SO4 concentrations investigated (1, 3 and 5 M). Analysis of cyclic voltammetry switching currents suggests that the technique might be suitable for fast determination of state of charge if the system is well calibrated. Membrane uptake and permeability measurements show that vanadium absorption and crossover is more dependent on both acid and vanadium concentration than state of charge. Vanadium diffusion in the membrane is about an order of magnitude slower (~10−11 m2s−1) than in solution (~10−10 m2s−1).

Symbiotic bacteria associated with ascidian vanadium accumulation identified by 16S rRNA amplicon sequencing

Ascidians belonging to Phlebobranchia accumulate vanadium to an extraordinary degree (≤ 350 mM). Vanadium levels are strictly regulated and vary among ascidian species; thus, they represent well-suited models for studies on vanadium accumulation. No comprehensive study on metal accumulation and reduction in marine organisms in relation to their symbiotic bacterial communities has been published. Therefore, we performed comparative 16S rRNA amplicon sequence analyses on samples from three tissues (branchial sac, intestine, and intestinal lumen) involved in vanadium absorption, isolated from two vanadium-rich (Ascidia ahodori and Ascidia sydneiensis samea) and one vanadium-poor species (Styela plicata). For each sample, the abundance of every bacteria and an abundance value normalized to their abundance in seawater were calculated and compared. Two bacterial genera, Pseudomonas and Ralstonia, were extremely abundant in the branchial sacs of vanadium-rich ascidians. Two bacterial genera, Treponema and Borrelia, were abundant and enriched in the intestinal content of vanadium-rich ascidians. The results suggest that specific selective forces maintain the bacterial population in the three ascidian tissues examined, which contribute to successful vanadium accumulation. This study furthers the understanding of the relationship between bacterial communities and metal accumulation in marine life.

Bioaccumulation of Vanadium by Vanadium-Resistant Bacteria Isolated from the Intestine of Ascidia sydneiensis samea.

Isolation of naturally occurring bacterial strains from metal-rich environments has gained popularity due to the growing need for bioremediation technologies. In this study, we found that the vanadium concentration in the intestine of the vanadium-rich ascidian Ascidia sydneiensis samea could reach 0.67mM, and thus, we isolated vanadium-resistant bacteria from the intestinal contents and determined the ability of each bacterial strain to accumulate vanadium and other heavy metals. Nine strains of vanadium-resistant bacteria were successfully isolated, of which two strains, V-RA-4 and S-RA-6, accumulated vanadium at a higher rate than did the other strains. The maximum vanadium absorption by these bacteria was achieved at pH 3, and intracellular accumulation was the predominant mechanism. Each strain strongly accumulated copper and cobalt ions, but accumulation of nickel and molybdate ions was relatively low. These bacterial strains can be applied to protocols for bioremediation of vanadium and heavy metal toxicity.

Bioavailability of Vanadium in Alfalfa in V-Cd Contaminated Soil

A greenhouse experiment was performed to investigate the vanadium bioavailability of alfalfa grown in vanadium-cadmium contaminated soil. The results show bioavailable and total vanadium concentration in rhizosphere soil is higher than it in non-rhizosphere soil. With increasing vanadium addition, its speciation in soil is transformed to AC, RE, and OX fraction, especially to RE fraction. Alfalfa has high vanadium accumulation (up to 1221.86 mg/kg), and 70% of root samples belonged to strong absorption to vanadium. Both bioavailable and total vanadium in rhizosphere and non-rhizosphere soil have direct correlation with its content in alfalfa root. The increasing cadmium addition may inhibit vanadium absorption in alfalfa roots.

A new experimental system of using fertile chick eggs to evaluate vanadium absorption and antidotal effectiveness to prevent vanadium uptake

To establish the absorption of vanadium compounds such as vanadium chloride, vanadyl sulfate, and sodium metavanadate and to find effective chelating and reducing agents to cope with the absorption and uptake of vanadium compounds by embryonic chicks, aqueous vanadium solutions with or without chelating and reducing agent solutions were introduced into the air sacs of 14-day-old fertile chick eggs. After incubation of a further 5 days, mortality, embryonic weight, and vanadium content in the legs and toes were measured. Vanadium concentration in the legs and toes increased linearly as the administration of vanadium compounds increased and can be used as an index for vanadium absorption. Vanadium accumulation in the legs and toes, embryonic growth, and mortality showed no essential differences among VCl 3, VOSO 4, and NaVO 3. Among 19 antidotal substances tested, deferoxamine mesylate was the most effective, and Xylenol Orange, EDTA, and basophenathroline were secondarily effective to prevent vanadium uptake. Tiron could not prevent absorption from VOSO 4 as effectively as NaVO 3. Deferoxamine was the most effective in decreasing the death rate and increasing embryonic growth. Tiron was secondarily effective when excessive Tiron was administered. Antidotal effectiveness of deferoxamine was observed when it was simultaneously administered with vanadium compounds. Deferoxamine and VOSO 4 formed an equimolar complex that is unabsorbable. These results are comparable with the results shown in previous reports using rats and mice. The present experimental system using fertile chick eggs had advantages in the examination of mineral absorption and in the screening for effective antidotes from the viewpoints of ease of experimental procedure and animal welfare in comparison with conventional methods using laboratory animals.

Vanadium absorption by plants:the uptake of vanadium by excised barley roots (Hordeum Vulgare c.v. Maris Mink)

The absorption of vanadium by plants has received only limited attention [1]. However it presents an interesting problem since this element is not only capable of existing in a wide range of oxidation states but the most biologically significant of these, vanadium(IV) and vanadium(V), are characterised not by simple cations, but by more complex species [2], commonly described as vanadyl (VO 2+) and vanadate (VO 4 3− ions, respectively. Studies have therefore been conducted to delineate the differences between the uptake patterns of vanadium supplied in these different forms. The effects of various physical parameters, notably temperature and pH have been examined and clear differences between the uptake of vanadium in different oxidation states have been demonstrated. The uptake of vanadium(V), as vanadate, was found to increase with concentration and pH (over the range pH = 3–7) but was unaffected by temperature changes in the range 0–30°C. For vanadium(IV), as vanadyl ion, uptake again increased with concentration and pH was observed to have an effect, but no significant temperature effect was observed. The uptake of the vanadyl cation was generally greater than that of the vanadate anion (or related polymeric oxoanion) under similar conditions. These effects can all be rationalised in terms of the known chemistry of the vanadium species and the general processes of ion uptake by plant roots.

Vanadium Uptake by Plants

The kinetics of vanadium absorption by excised barley (Hordeum vulgare L., cv. Eire) roots were investigated with respect to ionic species of V in solution, time and concentration dependence, Ca sensitivity, and interaction with various anions, cations, and pH levels. The role of metabolism in V absorption was also studied using anaerobic treatment (N(2) gas) and chemical inhibitors (NaN(3), KCN, or 2,4-dinitrophenol). Approximately one-third of the labeled V initially taken up by excised roots was desorbed to a constant level after 45 min in unlabeled V solutions. The rate of absorption of labeled V from 5 mum NH(4)VO(3) solutions containing 0.5 mm CaSO(4) was constant for at least 3 hours. Omission of Ca resulted in a 72% reduction in V uptake when compared to controls with 0.5 mm CaSO(4). The rate of uptake of V was highest at pH 4 but dropped to a very low level at pH 10. It was relatively constant between the pH levels of 5 and 8 at which the VO(3) (-) ion is the predominant ionic species in solution. The rate of absorption of V was followed as a function of concentrations from 0.5 to 100 mum NH(4)VO(3). It was found to be a linear function of concentration and did not follow saturation kinetics. Absorption experiments carried out with labeled V from either N(a)VO(3) or NH(4)VO(3) sources gave similar results. No anion studied (i.e. HPO(4) (2-), HAsO(4) (2-), MoO(4) (2-), SeO(4) (2-), SeO(3) (2-), CrO(4) (2-), BO(3) (3-), No(3) (-), and Cl(-)) interfered appreciably (i.e. less than 30% inhibition) with the absorption of labeled V. Anaerobic treatment of absorption solution with N(2) gas did not inhibit V absorption by excised roots. The results obtained using chemical inhibitors were not consistent. It was concluded that V is not actively absorbed by excised barley roots.

Vanadium Concentration of Urine

Abstract A rapid, convenient test for the estimation of small amounts of vanadium in urine is described. The method is based on the catalytic effect of vanadium on the oxidation of N, N-diethyl-p-phenylenediamine by potassium chlorate. Only 1 ml. of urine is required and the test is sensitive to quantities of vanadium as low as 0.01 µg. per ml. of urine. Semiquantitative analyses can be made over a range of 0-1 µg. of vanadium per ml. of urine. The test is designed for application in rapid clinical analyses on small amounts of urine to determine possible vanadium absorption and is suggested for use as a screening test to determine on-the-job exposure of workers to vanadium compounds in excess of the suggested threshold limit value. Data showing the application of the test in several species are given.