Sodium Molybdate Solutions Research Articles

Electrodeposited α- and β-Phase MoO3 Films and Investigation of Their Gasochromic Properties

α- and β-Phase MoO3 are synthesized using an electrodeposition method on fluorine-doped tin oxide (FTO) glass substrates from sodium-molybdate (Na2MoO4) solutions. We show that it is possible to obtain both α- and β-MoO3 by manipulating the cyclic voltammetry (CV) parameters during electrodeposition. Raman spectroscopy, X-ray diffraction, and scanning electron microscopy indicate that the applied potential range and sweep rate are strongly influential on the phase obtained and the surface morphology of the electrodeposited thin films. Gasochromic measurements were carried out on the annealed samples by exposing them to H2 gas. It was revealed that α-MoO3 thin films provided better response to H2 interaction than β-MoO3 films did. Additionally, porous films provided significantly larger responses than smooth films.

Recovery of vanadium during ammonium molybdate production using ion exchange

The recovery of vanadium in ammonium molybdate production with raw sodium molybdate solution was studied. Experimental results showed that the vanadium and some of impurities P, As and Si can be adsorbed along with the molybdenum from the feed liquid by the weak base resin D314 in the pH range of 2.5–3.5 and then they can be eluted from the loaded resin with ammonia liquor. The vanadium can partially natural-precipitate from the eluted solution. The lower the pH value is and, the longer the standing time is, the less the vanadium remained in the solution will be. Standing for 24 h in pH value 6.9, the vanadium in the solution was reduced to 0.51 g/L V 2O 5. It was found that the precipitate is ammonium isopoly-vanadate and it is impure. By washing the precipitate with hydrochloric acid and ammonia solution sequentially and then roasting at 500 °C for 2 h, the product of V 2O 5 with the purity 99.12% was obtained. The impurities P, As and Si in the stood solution were removed by purifying with MgCl 2 under the pH value range of 8.0–9.0 at 60–80 °C for about 2 h, while the removal of the vanadium in the solution was performed by adsorbing with the strong base resin D296 in pH value about 7.0. The devanadiumized solution can be used to produce high-quality ammonium molybdate. The loaded vanadium resin was eluted with HCl 6 mol/L and, the eluted solution was returned to adjust the sodium molybdate solution pH value. The vanadium can be effectively separated and recovered in the process.

Surface modification with multiphilic ligands at detectable well defined active positions of nano-object of giant wheel shaped molybdenum blue showing third-order nonlinear optical properties

The reaction of an aqueous solution of sodium molybdate with l-tyrosine in the presence of reducing agent results in the formation of a new compound of the formula of Na 8Co 3[Mo VI 126 Mo V 28O 462H 14(H 2O) 46(HOC 6H 4CH 2CH( NH 3 + )COO −) 12]·ca. 200H 2O. The compound contains nanosized ring-shaped clusters with tyrosine ligands possessing different types of functional groups (one –CO 2, one – NH 3 + and one –ArOH) coordinated through the carboxylate groups at the active sites of the inner cavity. Importantly, the result demonstrates that not only active sites/areas of the cluster surface under a specified condition can be directly monitored and detected but also novel type surfaces within the cavity of a nano-structured ring-shaped cluster can be generated simultaneously. The nonlinear optical properties of the new cluster are studied using the well-known Z-scan technique at a wavelength of 532 nm with laser pulse duration of 18 ps. The results show that the new cluster exhibits interesting self-focusing nonlinear optical response with the real and imaginary parts of the third-order nonlinear optical susceptibility χ (3) being 1.069 × 10 −13(esu) and 2.529 × 10 −15(esu), respectively, which may find application in material science.

Selective extraction and deep removal of tungsten from sodium molybdate solution by primary amine N1923

Selectively extracting tungsten to purify sodium molybdate solution was studied using primary amine N1923, including various conditions, such as equilibrium pH values, concentrations of extractant in organic phase and metals in feed solution, contact time of extraction and stripping, types of acidic solutions added, temperature of extraction and the dosage of stripping agent. Graphical method using McCabe-Thiele diagram and counter-current extraction simulation (CCES) were used to determine the required stages of deep removal of tungsten. The results show that appropriate concentrations of tungsten and molybdenum in feed solution have great influence on the difficult degree of the separation between the two metals. Organic phase including 0.051 M of N1923 modified by LK-N21X diluted in kerosene can extract 92.7% of tungsten in sulfuric acid solution at equilibrium pH value of 7.07 for 10 min in one-stage extraction at 15.5 °C, and the separation factor reaches 329 under those optimum conditions. A two-stage CCES removes 99.83% of tungsten and obtains the purified sodium molybdate solution where W/Mo (mass ratio) reaches 2.9 × 10 −5. Stripping can be accomplished by NaOH solution completely and quickly. Furthermore, the extraction and stripping reactions of tungsten and molybdenum in equilibrium were proposed.

Synthesis and Characterization of Cu(II) Substituted Hexa Tungstate and Molybdate of the Anderson Type Anion [Xn+M6O24]-(12-n)

Sodium salts of copper substituted heteropoly compounds having molecular formula Na10[CuIIWVI6O24].22H2O(1) and Na10[CuIIMoVI6O24]. 19H2O(2) analogous to the Anderson type anion [Xn+M6O24]─(12-n)were synthesized according to the literature method. Compound(1) was synthesized from aqueous acidic solution containing sodium tungstate and copper chloride and compound(2) from sodium molybdate and copper chloride solution. The elemental analyses show 1:6 atomic ratio of the heteroatom to the addenda in both the compounds. The IR spectra for both the compounds are in good agreement with the reported formulae. A small deviation in IR spectra are observed than that established for Keggin anions. CuO6acts as hetero group which replaces MO6(M=W or Mo) from the Anderson structure. The thermal analyses of the compounds show the loss of the peripheral water molecules. The molecular weight of the compound (1) and (2) have been found as 2212.5 and 1600.5 respectively.

Synthesis and characterization of binuclear oxomolybdenum(V) and dioxomolybdenum(VI) O, O′-ditolyl dithiophosphate complexes. : Crystal structures of Mo 2O 3[S 2P(OC 6H 4Me- o) 2] 4, Mo 2O 3[S 2P(OC 6H 4Me- m) 2] 4 and MoO 2[S 2P(OC 6H 4Me- p) 2] 2

A series of binuclear oxomolybdenum(V) O, O′-ditolyl dithiophosphate complexes, Mo 2O 3[S 2P(OR) 2] 4 (R = o-, m-, p-C 6H 4Me) were synthesized by drop wise addition of aqueous solution of the ammonium salt of O, O′-ditolyl dithiophosphoric acid into an acidic solution of sodium molybdate with constant stirring to yield purple solids. Dioxomolybdenum(VI) O, O′-ditolyl dithiophosphate complexes, MoO 2[S 2P(OR) 2] 2 (R = o-, m-, p-C 6H 4Me and CH 2C 6H 5) were also synthesized by reducing Mo 2O 3[S 2P(OR) 2] 4 with OPPh 3 in benzene to yield yellow solids. These complexes were characterized by elemental analysis and IR, 1H and 31P NMR spectroscopy and, in three cases, by X-ray crystallography. In Mo 2O 3[S 2P(OC 6H 4Me- o) 2] 4 and Mo 2O 3[S 2P(OC 6H 4Me- m) 2] 4, the environment around each molybdenum atom can be described as the expected distorted octahedral, consisting of one terminal and one bridging oxygen along with the four chelating sulfur atoms of the dithio ligands, with one Mo–S distance being significantly longer than the other three. In MoO 2[S 2P(OC 6H 4Me- p) 2] 2 the geometry around the Mo atom is again distorted octahedral with two cis terminal oxygen atoms and two anisobidentate dithiophosphate ligands.

Kinetics of isotopic exchange between calcium molybdate and molybdate ions in aqueous solution

The heterogeneous isotopic anion exchange kinetics and equilibria between calcium molybdate and sodium molybdate solutions have been studied by using 99Mo as tracer in batch experiments. The values of exchange ratio lower than unity suggest that rate-limiting step is particle diffusion process and the effect of re-crystallization can be neglected. The self-diffusion coefficients calculated using both Paterson´s and Nernst–Plank approximations are increased by the temperature. The observed values for isotope exchange characteristics such as exchange fractions, exchanging amounts and fractional attainment of equilibrium are consistent with those of their calculated values. Activation energy and thermodynamic parameters calculated based on transition state theory indicate the existence of both energy and entropy barrier in the system.

Synthesis and characterization of a new inorganic cation-exchanger—Zr(IV) tungstomolybdate: Analytical applications for metal content determination in real sample and synthetic mixture

An amorphous sample of inorganic cation-exchanger Zr(IV) tungstomolybdate was prepared by mixing varying ratios of 0.1 M aqueous solution of sodium tungstate and 0.1 M aqueous solution of sodium molybdate into 0.1 M aqueous solution of zirconium oxychloride at pH 1. This cation-exchanger was found to have a good ion-exchange capacity (2.40 mequiv. g −1 for Na +), high thermal and chemical stability. A tentative structural formula was proposed on the basis of chemical composition, FTIR and thermogravimetric analysis. Distribution coefficients ( K d) values of metal ions in various solvent systems were determined. Some important and analytically difficult quantitative binary separations viz. Ni(II)–Pb(II), Ni(II)–Zn(II), Ni(II)–Cd(II), Mg(II)–Al(III), etc. were achieved. The practical applicability of the cation-exchanger was demonstrated in the separation of Cu(II)–Zn(II) from a synthetic mixture as well as from real samples of pharmaceutical formulation and brass alloy.

Molybdate-exchanged layered double hydroxides for the catalytic disproportionation of hydrogen peroxide into singlet oxygen: Evaluation and improvements of 1O 2 generation by combined chemiluminescence and trapping experiments

The generation of singlet molecular oxygen ( 1O 2) from H 2O 2 catalyzed by molybdate-exchanged layered double hydroxides (Mo-LDHs) was studied by chemiluminescence (CL) and chemical trapping (CT) experiments. In the first part, the utility of chemiluminescence spectroscopy to quantify the amount of 1O 2 produced in heterogeneous media was evaluated by comparison with 1O 2 yields determined in homogeneous solutions of sodium molybdate. On the other hand, the 1O 2 yields determined by CL spectroscopy were compared with those obtained via chemical trapping of 1O 2 with β-citronellol as an olefinic substrate. Advantages and limitations of CL spectroscopy for the determination of 1O 2 yields in heterogeneous media are discussed. CL spectroscopy allows the rapid screening of heterogeneous catalysts for the generation of 1O 2. On the other hand, the spectroscopic technique only yields the total amount of 1O 2 and provides no information on the availability of the produced 1O 2 for reaction with olefinic substrates. In the second part, CL and CT experiments were used to determine optimized conditions for the generation of 1O 2 from Mo-LDHs. Compositional parameters of the catalyst and reaction conditions were varied. A Mo-LDH catalyst possessing a low Mg/Al molar ratio and a low Mo loading was identified as the optimum catalyst in terms of activity and efficiency. Methanol and N, N-dimethylformamide are the optimum solvents.

Electrolytic molybdenum oxides in lithium batteries

Nonstoichiometric molybdenum oxides (e-MoxOy) were synthesized by cathodic reduction of aqueous ammonium and sodium molybdate solutions. Surface morphology of electrolytic (e) deposits, the chemical composition, crystal lattice structure, and the characteristics of electrochemical Li+ intercalation for such synthesized oxides were determined by the cation composition of molybdate solution and the conditions of deposit annealing. The electrochemical intercalation of Li+ ions in these Mo-oxides was investigated in thin-layer “ballast-free” electrodes, as a pasted соmposite cathode in lithium batteries, and as an anode in lithium-ion batteries, with liquid organic and polymer electrolytes. The reversible discharge capacity of e-Mo4O11 synthesized from ammonium molybdate electrolyte in thin-layer ballast-free electrodes can exceed 225 mAh g−1 for more than 170 cycles.

Electrolytic Synthesis of Complex Oxide Systems by Cathodic Deposition of Molybdenum Oxide from Aqueous Solutions in the Presence of Nickel(II) and Thiosulfate Ions

Cathodic processes occurring in electrolytic deposition of molybdenum oxide from aqueous solutions of sodium molybdate in the presence of nickel(II) and thiosulfate ions were studied. Conditions for formation of cathodic deposits in the form of complex oxide systems Mo-Ni and Mo4O11-MoS2 were determined.

The isolation and X-ray characterization of a new sodium heptamolybdate compound, Na 7[Mo 7O 24]OH·21H 2O

The sodium heptamolybdate compound ( 1) was crystallized at pH ∼6.9 from an acidified sodium molybdate solution. X-ray structural analysis shows a novel empirical formula of Na 7[Mo 7O 24]OH·21H 2O for this compound in which a complex network of ion–dipole interactions and hydrogen bonds were found to stabilize the crystal structure.

Electrochemical Synthesis of Molybdenum Oxide Thin Films: Deposition Mechanism and Template-Directed Assembly of Nanostructured Materials and Components

AbstractWe describe the electrochemical deposition of molybdenum oxide thin films prepared from aqueous solutions containing peroxo-poly and oxometallate complexes of molybdenum(VI). Electrochemical quartz crystal microgravimetry (EQCM) was used to establish corresponding reaction mechanisms for films grown at different deposition potentials. Electrodeposition from acidified sodium molybdate solutions proceeds by the reduction of molybdic acid; whilst deposition from aqueous peroxo-based solutions involves the graded reduction of several solution components, primarily comprising molybdic acid and peroxopolymolybdates. Films grown from acidified sodium molybdate solutions are weakly adherent and easily rinsed off, while those grown from peroxo-polymolybdate solutions are strongly attached and stable. Careful regulation of the deposition potential allows for controlled growth of distinct molybdenum oxide compositions to produce films with varied water content and valency. Electrochemical deposition through sacrificial colloidal-crystal templates is also demonstrated to prepare macroporous thin films comprising hexagonally close-packed arrays of spherical pores.

Evaluation of food additives and low-toxicity compounds as alternative chemicals for the control of Penicillium digitatum and Penicillium italicum on citrus fruit.

The effectiveness of low-toxicity chemicals as possible alternatives to synthetic fungicides for the control of post-harvest green and blue moulds of citrus was evaluated. A preliminary selection of chemicals, mostly common food additives, was made through in vivo primary screenings with oranges artificially inoculated with Penicillium digitatum or P italicum. Selected compounds and mixtures were tested as heated solutions in small-scale trials. Immersion of artificially inoculated oranges or lemons for 120 s in solutions at 40.6 degrees C and natural pH of potassium sorbate (0.2 M), sodium benzoate (0.2 M) or mixtures (0.1 + 0.1 M) of potassium sorbate with sodium benzoate, sodium propionate or sodium acetate were the most effective organic acid salts tested and reduced green mould by 70-80% after 7 days of storage at 20 degrees C. The mixtures did not significantly enhance the effectiveness of potassium sorbate or sodium benzoate alone. These solutions were as effective as sodium carbonate or calcium polysulphide treatments and, in general, they were more effective on lemons than on oranges. Satisfactory control of green and blue moulds was obtained by dipping oranges for 150 s in solutions of sodium molybdate (24.2 mM) or ammonium molybdate (1.0 mM) at 48 or 53 degrees C, but not at 20 degrees C. At 53 degrees C, however, the effectiveness of hot water was not enhanced by either molybdate. Molybdenum salts at higher concentrations were phytotoxic and stained the fruit. At non-phytotoxic concentrations, the effectiveness of these solutions was more influenced by temperature than by concentration. In general, the inhibitory effects of all compounds tested were not fungicidal but fungistatic and not very persistent. In conclusion, potassium sorbate, sodium benzoate and ammonium molybdate, among the wide range of chemicals tested, were superior for the control of post-harvest Penicillium decay of citrus fruit.

Isotope exchange of strontium and molybdate ions in strontium polymolybdates

The heterogeneous isotopic exchange reactions in strontium polymolybdates of Sr2+ and MoO42- ions in the strontium nitrate and sodium molybdate solutions have been studied using 90Sr and 99Mo as tracers. Electrometric methods have been used to study the compositions of strontium molybdates obtained by adding strontium chloride to a progressively acidified solution of sodium molybdate. It has been found that the exchange fraction increases with increasing chain length of strontium polymolybdate. The exchange equilibrium constant (Kex) has been calculated between 298 and 348 K as well as DG°, DH° and DS°. The results indicate that Sr2+ cations have a much higher affinity for exchangers than MoO42- anions. By fitting the data to the Dubinin-Radushkevich (D-R) isotherm it has been shown that the exchange capacity (Xm) for both ions is affected by the ion adsorption process at low temperatures and by the ion exchange process at high temperatures. At high concentrations, the recrystallization process contributes to on the cation exchange but is ineffective on the anion exchange mechanism.

Outer-sphere addition compounds of MoO 2Br 2(H 2O) 2 with ethers. Molecular structure of MoO 2Br 2(H 2O) 2·L (L=2,5,8-trioxanonane; 2,5,8,11,14-pentaoxapentadecane)

Outer-sphere addition compounds of MoO 2Br 2(H 2O) 2 with diethyl ether, dioxane, glyme, diglyme, triglyme and tetraglyme have been readily prepared by crystallizing diethyl ether extracts of a solution of sodium molybdate in concentrated hydrobromic acid in the presence of the corresponding ether. The molecular structures of MoO 2Br 2(H 2O) 2·L (L=2,5,8-trioxanonane; 2,5,8,11,14-pentaoxapentadecane) have been established by X-ray diffraction analysis.

(CH3)2NH2]4[H4PMo12O40]Cl2·4H2O

The hydro­thermal reaction of an aqueous solution of sodium molybdate, hypo­phospho­rous acid, hydro­chloric acid and N,N-di­methyl­form­amide (DMF) gave rise to tetradi­methyl­ammonium tetra­hydroxy­dotriacontaoxo­(tetraoxophosphato)­dodecamolybdate di­hydro­chloride tetrahydrate. The poly­anion has a β-Keggin structure, with P—O distances ranging from 1.535 (5) to 1.552 (5) A and Mo—O distances from 1.664 (4) to 2.509 (4) A.

Na4(H2O)7][Fe(OH)6Mo6O18]: A new [12] metallacrown-6 structure with an octahedrally coordinated iron at the center

The reaction of an aqueous solution of sodium molybdate with iron powder at low pH (∼0.184) gives rise to the formation of a six-member Mo ring-shape cluster with an Fe (II) encapsulated at the center, [Na4(H2O)7][Fe(OH)6Mo6O18](1), which is further linked to a remarkable three-dimensional network via sodium ions.

Some molybdenum-containing chelating ion-exchange resins (polyampholites) as catalysts for the epoxidation of alkenes by organic hydroperoxides

Heterogeneous molybdenum-containing polymeric catalysts for the epoxidation of alkenes by organic hydroperoxides were prepared by a simple treatment of the chelating ion exchange resins (polyampholites) Amberlite IRC718, Amberlite IRC748 and Duolite C467 (Rohm&Haas, USA) with both the aqueous solution of sodium molybdate at pH 3.5 and solution of molydenyl acetylacetonate in toluene. The formation of the catalytically active centres by the interaction of the oxomolybdenum species from the reaction solution with ligand functional groups of the ion exchangers was proved. The stability of these polymeric complexes on multiple use with the epoxidation of cyclohexene by tert-butylhydroperoxide (TBHP) in the absence of an inert solvent at temperature 79°C and initial TBHP concentration of 1.2–1.3 mol l −1 was studied.

Assembling nanosized ring-shaped synthons to an anionic layer structure based on the synergetically induced functional complementarity of their surface-sites: Na21[MoVI126MoV28O462H14(H2O)54(H2PO2)7]·xH2O (x ≈ 300)

The reaction of an aqueous solution of sodium molybdate with hypophosphorous (phosphinic) acid acting both as reducing agent and ligand at low pH values (≈1) results in the formation of nanosized ring-shaped cluster units which assemble to form layers of the compound Na21[MoVI126- MoV28O462H14(H2O)54(H2PO2)7]·xH2O 1 (x ≈ 300); the assemblage is based on the synergetically induced functional complementarity of amphiphilic OMoL (L = H2O, H2PO2–) groups and corresponds to the replacement of H2O ligands of rings by related terminal MoO groups of other rings (and vice versa) the nucleophilicity of which is induced by coordinated H2PO2– ligands.