Presence Of Na2MoO4 Research Articles

Excellent photocatalytic performance of PAA/Na2MoO4-Fe3+ hydrogel with Na2MoO4 as sacrificial agent for dye removal

Currently, the majority of photocatalytic materials primarily consist of insoluble semiconductors, whereas soluble semiconductor materials have limited applications in photocatalysis. In this study, it is proposed for the first time to use the soluble semiconductor sodium molybdate (Na2MoO4) as a sacrificial agent to fabricate a polyacrylic acid/sodium molybdate-Fe3+ hydrogel photocatalyst (PAA/Na2MoO4-Fe3+) through polymerization with Fe3+ ions and acrylic acid (AA) monomer. The hydrogel photocatalyst was thoroughly characterized and the results revealed that the presence of Na2MoO4 in ionic form within the hydrogel significantly enhanced its adsorption capacity for pollutant molecules. Additionally, Fe3+ ions coordinated with -COOH (L) groups on PAA to form [Fe(L)6]3+ ions, which acted as active sites of photocatalytic. Moreover, the PAA/Na2MoO4-Fe3+ hydrogel exhibited promising potential as a photocatalyst for the remove of dye pollutants (e.g. MB, MG, RhB and MO) from wastewater. Finally, we also explored and analyzed the photocatalytic mechanism of the hydrogel. It is noteworthy to conclude that the hydrogel possesses immense potential for the practical application of photocatalytic techniques in the treatment of dyes wastewater.

Corrosion mitigation ability of differently synthesized polypyrrole (PPy-FeCl3 & PPy-APS) conductive polymers modified with Na2MoO4 on mild steel in 3.5% NaCl solution: Comparative study and optimization

In this paper, polypyrrole (PPy) conductive polymers were created in the presence of ferric chloride (FeCl3) and ammonium peroxodisulfate (APS) oxidants. Sodium molybdate (Na2MoO4) is used for the PPy corrosion inhibitory effect in NaCl solution. According to the electrochemical impedance spectroscopy (EIS) results, the corrosion resistance of steel plates subjected to the Na2MoO4 containing solution with different ratios of PPy-FeCl3 and PPy-APS was significantly improved, revealing that the barrier properties of the PPy film have drastically improved in the presence of Na2MoO4. The polarization test results revealed noticeable corrosion rate decrement with the incorporation of molybdate to the PPy-FeCl3-containing solution.

Oxidative Desulfurization of Straight-Run Diesel Fraction

Oxidative desulfurization of straight-run nonhydrotreated diesel fraction with hydrogen peroxide in the presence of Na2MoO4 or Na2WO4, dibenzyl peroxide, and potassium permanganate; by air bubbling; and in the presence of ionic liquids has been studied. The oxidation products have been recovered from the oxidized diesel fraction using alumina, silica gel, or activated charcoal or via extraction with acetonitrile, N,N-dimethylformamide, or acetone. The best results of the diesel desulfurization have been achieved in the case of dibenzyl peroxide as an oxidizing agent in the presence of Na2MoO4.

Electrochemical Corrosion Behavior of 316L Stainless Steel in LiBr Solution in the Presence of Na2MoO4 As an Inhibitor

The inhibition effect of sodium molybdate (Na2MoO4) at concentrations of 50, 100 and 200­ppm in 60°C on the electrochemical corrosion behavior of 316L stainless steel in LiBr solution at 60°C was studied by polarization curves, electrochemical impedance spectroscopy (EIS) methods and electron microscopy. Polarisation curves indicate that Na2MoO4 acts as mixed-type inhibitor. The corrosion resistance of 316L stainless steel samples increases with the inhibitor concentration up to 200ppm. By increasing the inhibitor concentration from 50ppm to 200ppm, corrosion current density decreases. This result was confirmed by scanning electron microscopy. Figure 1

Selective Voltammetric Analysis of o‐Diphenols from Olive Oil Using Na2MoO4 as Electrochemical Mediator

AbstractThe complexing ability of molybdate vs. o‐diphenols has been exploited for their selective electrochemical detection. Graphite screen printed and carbon paste electrodes have been evaluated as electrochemical transducers for the selective mediated detection of o‐diphenol compounds in the presence of Na2MoO4. Immobilization of the mediator onto the electrode surface has also been achieved using different types of single and multiwall carbon nanotubes. The best sensor in terms of selectivity, sensitivity and stability was the Mo‐MW‐CNT‐NH2 modified electrode. Using the mediator either in solution or immobilized, detection of o‐diphenols with linearity in the ppm range was achieved. An amperometric flow injection analysis set‐up was used to detect the o‐diphenolic content of phenolic extracts obtained from olive oil samples.

Metal-catalysed organic transformations in water: From bromination to polymerisation

Reaction ofα,Β-unsaturated aromatic carboxylic acids with KBr and H2O2 in the presence of Na2MoO4·2H2O in aqueous medium affordsΒ-bromo alkenes in high yields. Metallocene dichlorides, Cp2MCl2 (M = Ti, Zr, or V) catalyse polymerisation of olefins in aqueous medium to afford high molecular weight polymers with low molecular weight distribution.

In Vitro Molybdenum Ligation to Molybdopterin Using Purified Components

We have previously shown that Escherichia coli MoeA and MogA are required in vivo for the final step of molybdenum cofactor biosynthesis, the addition of the molybdenum atom to the dithiolene of molybdopterin. MoeA was also shown to facilitate the addition of molybdenum in an assay using crude extracts from E. coli moeA(-) cells. The experiments detailed in this report utilized an in vitro assay for MoeA-mediated molybdenum ligation to de novo synthesized molybdopterin using only purified components and monitoring the reconstitution of human aposulfite oxidase. In this assay, maximum activation was achieved by delaying the addition of aposulfite oxidase to allow for adequate molybdenum coordination to occur. Tungsten, which substitutes for molybdenum in hyperthermophilic organisms, could also be ligated to molybdopterin using this system, though not as efficiently as molybdenum. Addition of thiol compounds to the assay inhibited activity. Addition of MogA also inhibited the reaction. However, in the presence of ATP and magnesium, addition of MogA to the assay increased the level of aposulfite oxidase reconstitution beyond that observed with MoeA alone. This effect was not observed in the absence of MoeA. The results presented here demonstrate that MoeA is responsible for mediating molybdenum ligation to molybdopterin, whereas MogA stimulates this activity in an ATP-dependent manner.

A green Hunsdiecker reaction: synthesis of beta-bromostyrenes from the reaction of alpha,beta-unsaturated aromatic carboxylic acids with KBr and H2O2 catalysed by Na2MoO4.2H2O in aqueous medium.

Reaction of alpha,beta-unsaturated aromatic carboxylic acids with KBr and H2O2 in the presence of Na2MoO4.2H2O in aqueous medium affords beta-bromo alkenes in high yield.

Kinetics and mechanism of the furan peroxide formation in the reaction of furfural with hydrogen peroxide in the presence or absence of sodium molybdate

The kinetics of the initial stage of the furfural reaction with hydrogen peroxide was studied in water in the presence of Na2MoO4 and in n-butanol without a catalyst. The mechanisms of furfural conversion in the Na2MoO4-H2O2 system and oxidation by hydrogen peroxide in the absence of sodium molybdate are discussed. Based on kinetic studies, the mechanism of furan peroxide formation is proposed.

Characterization of a spontaneous mutant of Azotobacter vinelandii in which vanadium-dependent nitrogen fixation is not inhibited by molybdenum.

A spontaneous mutant derivative of Azotobacter vinelandii CA12 (delta nif HDK), which vanadium-dependent nitrogen fixation is not inhibited by molybdenum (A. vinelandii CARR), grows profusely on BNF-agar containing 1 microM Na2MoO4, alone or supplemented with 1 microM V2O5. The expression of A. vinelandii vnfH::lacZ and vnfA::lacZ fusions in A. vinelandii CARR was not inhibited by 1 mM Na2MoO4, whereas molybdenum at much lower concentration inhibited the expression of vnfH::lacZ and vnfA::lacZ fusions in A. vinlandii CA12. The mutant also exhibited normal acetylene reduction activity in the presence of 1 microM Na2MoO4. The expression of A. vinelandii nifH::lacZ fusion in A. vinelandii CARR was low even though the cells were cultured under non-repressing conditions with urea as nitrogen source in the presence of Na2MoO4. The molybdenum content of A. vinelandii CARR cells was found to be about one-fourth that of A. vinelandii CA12. No nitrate reductase activity could be detected in A. vinelandii CARR when the cells were cultured in the presence of 10 microM Na2MoO4, whereas A. vinelandii CA12 exhibited some activity even with 100 pM Na2MoO4.

STUDY OF THE POLY(N-VINYL-2-PYRROLIDONE)-Na2MoO4 INTERACTIONS IN AQUEOUS SOLUTION: EFFECT ON THE POLYMER MORPHOLOGY

In this paper, the morphology of poly(N-vinyl-2-pyrrolidone) (PVP) in the presence of Na2MoO4 has been studied using scanning electron microscopy (SEM). Moreover the poly(N-vinyl-2-pyrrolidone) (PVP)(2)/water(1)/Na2MoO4(3) ternary system has been characterized by viscometry and densimetry. A lattice-like tridimensional structure of PVP due to its interaction with Na2MoO4 is observed. In this ternary system both a preferential adsorption of water at all solvent compositions studied is observed, except at 100 mM of Na2MoO4, concentration at which a preferential adsorption of salt is exhibited. Na2MoO4 behaves as a salting-in agent for the macromolecule, the binary solvent mixture being thermodynamically unfavourable at salt concentrations larger than 10 mM Na2MoO4. © 1997 Elsevier Science Ltd. All rights reserved

Phenotypic characterization of a tungsten-tolerant mutant of Azotobacter vinelandii.

A tungsten-tolerant mutant strain (CA6) of Azotobacter vinelandii first described in 1980 (P. E. Bishop, D. M. L. Jarlenski, and D. R. Hetherington, Proc. Natl. Acad. Sci. USA 77:7342-7346, 1980) has been further characterized. Results from growth experiments suggest that both nitrogenases 1 and 3 are utilized when CA6 grows in N-free medium containing Na2MoO4. Strain CA6.1.71, which lacks both nitrogenases 2 and 3, grew as well as strain CA in N-free medium containing Na2MoO4 after an initial lag. This indicates that nitrogenase 1 is fully functional in strain CA6. nifH-lacZ and anfH-lacZ transcriptional fusions were expressed in CA6 in the presence of Na2MoO4. Thus, in contrast to wild-type strain CA, transcription of the anfHDGK gene cluster in strain CA6 is not repressed by Mo. Expression of the vnfD-lacZ fusion was the same in both strains CA and CA6. In agreement with the results obtained with lac fusions, subunits of both nitrogenases 1 and 3 were found in protein extracts of CA6 cells grown in N-free medium containing Na2MoO4. However, CA6 cells, cultured in the presence of Na2WO4, accumulated nitrogenase 3 proteins without detectable amounts of nitrogenase 1 proteins. This indicates that expression of Mo-independent nitrogenase 3 is the basis for the tungsten tolerance phenotype of strain CA6. A measure of Mo accumulation as a function of time showed that accumulation by strain CA6 was slower than that for strain CA. When Mo accumulation was studied as a function of Na2MoO4 concentration, the two strains accumulated similar amounts of Mo in the concentration range of 0 to 1 microM Na2MoO4 during a 2-h period. Within the range of 1 to 5 microM Na2MoO4, Mo accumulation by strain CA increased linearly with increasing concentration whereas no further increases were observed for strain CA6. These results are consistent with the possibility that the tungsten tolerance mutation carried by CA6 is in a Mo transport system.

Molybdenum uptake through the anion exchanger in human erythrocytes.

Human red blood cells were incubated in the presence of Na2MoO4 and the initial rate of molybdenum uptake was measured by using inductively coupled plasma emission spectroscopy. About 99% of molybdenum uptake was inhibited by DIDS or by SITS. DIDS-sensitive molybdenum uptake was inhibited by external chloride, bicarbonate, sulphate and phosphate in the range of concentrations previously described for anion carrier fluxes. Trace elements, previously described to be translocated by the anion carrier, i.e. copper, zinc and cadmium, slightly inhibited molybdenum uptake. Molybdenum uptake was strongly stimulated by acidification, suggesting that the monovalent HMoO4- anion species, which is formed in acidic media (pK approximately 4.1), can be more rapidly translocated than the divalent anion complex MoO4(2-), which is the predominant form at physiological pH. In conclusion, the anion carrier can catalyse rapid molybdenum movements across red cells membranes. This supports previous reports of an enterohepatic circulation of molybdenum, with red blood cells acting as molybdenum carrier between the intestine and the liver.

Intracellular inhibition of chromatin binding and transformation of androgen receptor by 3′-deoxyadenosine.

Incubation of minced rat ventral prostate with 3'-deoxyadenosine (3'-dA) prior to labeling with the androgen, tritiated 7 alpha, 17 alpha-dimethyl-19-nortestosterone, reduced the level of androgen receptor bound to chromatin and increased the level of cytosolic androgen receptor and the fraction of cytosolic androgen receptor that did not bind to DNA. This effect was specific for 3'-dA and not mimicked by adenosine, 2'-deoxy-adenosine, cytidine, guanosine, or uridine. Adenosine was a competitive inhibitor of the 3'-dA effect. Labeled cytosolic androgen receptor from 3'-dA-treated prostate had properties that were similar to those exhibited by untransformed androgen receptor from prostate cytosol prepared in the presence of Na2MoO4, an inhibitor of receptor transformation in cell-free systems. Both androgen receptors had sedimentation coefficients of 8-9 S in low-salt gradients, did not bind to DNA tightly, and had a high affinity for DEAE-cellulose. The 3'-dA effect on these properties was not observed if androgen receptor from 3'-dA-treated prostate was isolated on high-salt gradients. These findings show that androgen receptor transformation does take place in intact prostate cells and suggest that 3'-dA inhibits chromatin binding of androgen receptor by interfering with androgen receptor transformation. The transformation process appears to involve removal of components from androgen receptor. Since 3'-dA is a potent inhibitor of the synthesis, polyadenylation, and nucleocytoplasmic transport of RNA, the 3'-dA effect may indicate a role for RNA in the mechanism of receptor transformation in intact target cells.

In vitro modulation of rat liver glucocorticoid receptor by urea.

We have examined the influence of urea on the properties of the rat liver glucocorticoid receptor (GR). A 1-h incubation of hepatic cytosol with 1-3 M urea at 0 or at 23 degrees C caused a progressive decrease in the steroid binding efficiency of GR. Urea treatment of cytosol incubated with 20 nM [3H]triamcinolone acetonide caused transformation of glucocorticoid-receptor complexes (GRc) and resulted in an increase in the binding of GRc to DNA-cellulose and ATP-Sepharose. The transforming effect was maximal with 2.5 M urea at 0 degrees C for 1 h, and it caused a shift in the rate of sedimentation of the 9 S untransformed GRc to a 4 S form, similar to that observed upon incubation of the cytosol GRc at 23 degrees C. This 9 to 4 S transformation could also be observed in the presence of Na2MoO4. The Stokes radii of the GRc eluted from a Bio-Gel-A-0.5m agarose column were determined to be 5.9 and 4.9 nm in the absence and presence of 2.5 M urea. The aqueous two-phase partitioning analysis revealed a significant change in surface properties of GR following urea treatment; the observed partition coefficient values (cpm upper phase/bottom phase) were 0.022, 0.208, and 0.60 for GRc, GRc + 23 degrees C, and GRc + 2.5 M urea, respectively. Furthermore, the urea treatment rendered the GRc less negatively charged, forcing their appearance in the flow-through fractions of a DEAE-Sephacel column. These results suggest that urea is a potent in vitro modulator of the physicochemical behavior of GR, influencing both the steroid binding and the process of receptor transformation.

Transcriptional regulation of nitrogen fixation by molybdenum in Azotobacter vinelandii.

Multiple genomic regions homologous to nifH were found in the diazotroph Azotobacter vinelandii. The nifHDK gene cluster, located on a 12.8-kilobase (kb) XhoI fragment and two additional XhoI fragments (7.4 and 8.4 kb) hybridized to a nifH-specific DNA template but the 7.4- and 8.4-kb fragments did not hybridize to nifD- or nifK-specific DNA probes. In vivo transcription of the nifHDK gene cluster was ammonia-repressible and required the presence of at least 50 nM molybdenum in the derepression medium. Three mRNA species were transcribed from the nifHDK gene cluster, a 4.2-kb transcript homologous to nifH-, nifD-, and nifK-specific DNA templates, a 2.6-kb transcript homologous to nifH- and nifD-specific DNA templates, and a 1.2-kb transcript homologous only to the nifH-specific DNA template. In strain CA11, a nifHDK deletion mutant, the nifHDK-specific transcripts were not produced and the strain was unable to grow in N-free medium in the presence of Na2MoO4 at concentrations of 50 nM or higher. However, at concentrations of 25 nM Mo or less, growth occurred in N-free medium. Under these conditions two nifH-homologous (but not nifD- or nifK-homologous) transcripts were observed (1.2 and 1.8 kb). Presumably these were transcribed from the additional nifH-homologous sequences present in the genome. These results are consistent with the existence of two N2 fixation systems in A. vinelandii which are regulated by molybdenum at the level of transcription.