Complete degradation of high-loaded phenol using tungstate-based ionic liquids with long chain substituent at mild conditions

Phenol in waste water threatens human health and is difficultly to be decomposed by nature.Efficient degradation of high-loaded phenol in water under mild condition is still a great challenge.Herein,ionic liquids with tungstate anion were designed and prepared.It was found that dodecyltrimethylammonium tungstate could catalyzed degradation of phenol into gases and water thoroughly at 323 k in 8 h.Tungstate anion revealed good catalytic oxidative activity and long carbon chain group connecting with cation of ionic liquids enriched phenol around catalysts,which induced the complete degradation of phenol at mild conditions.Increasing the amounts of hydrogen peroxide benefited to the total degradation of phenol.In addition,the ionic liquid could be reused for its excellent thermal stability.Our work provided a different strategy to treat waste water containing phenol efficiently.

Nanostructured Ternary Metal Tungstate-Based Photocatalysts for Environmental Purification and Solar Water Splitting:A Review

Visible-light-responsive ternary metal tungstate(MWO_4) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including low cost,eco-friendliness, and high stability under acidic and oxidative conditions. However, rapid recombination of photoinduced electron–hole pairs and a narrow light response range to the solar spectrum lead to low photocatalytic activity of MWO_4-based materials, thus significantly hampering their wide usage in practice. To enable their widespread practical usage, significant efforts have been devoted, by developing new concepts and innovative strategies. In this review, we aim to provide an integrated overview of the fundamentals and recent progress of MWO_4-based photocatalysts. Furthermore, different strategies, including morphological control, surface modification, heteroatom doping, and heterojunction fabrication, which are employed to promote the photocatalyticactivities of MWO_4-based materials, are systematically summarized and discussed. Finally, existing challenges and a future perspective are also provided to shed light on the development of highly efficient MWO_4-based photocatalysts.

Alkali salts of heteropoly tungstates: Efficient catalysts for the synthesis of biodiesel from edible and non-edible oils

Alkali salts of tungsten based heteropoly acids with different central atom such as P, Si and Co were prepared and evaluated for transes- terification of both edible and non-edible oils to their corresponding fatty acid methyl esters. The catalyst of sodium salt of tungstic acid with Co as central atom （Na5CoW12O40） showed optimum activity towards transesterification compared with other heteropoly tungstates. The catalysts activities were correlated with the observed physico-chemical characteristics derived from FT-infrared （FT-IR）, X-ray diffraction （XRD）, temperature-programmed desorption of ammonia （NH3-TPD） and carbon dioxide （CO2-TPD）. The Na5CoW12O40 catalyst exhibiting high activity even at 65 ℃ is due to the presence of strong acidic as well as basic sites. The disclosed catalyst is tolerable towards water and free fatty acids present in the oils. The influence of catalyst loading, reaction time and reaction temperature is studied to optimize the reaction parameters.

Simultaneous determination of some trace metal impurities in high-purity sodium tungstate using coprecipitation and inductively coupled plasma atomic emission spectrometry

A method based on the combination of coprecipitation with inductively coupledplasma atomic emission spectrometry (ICP-AES) was developed for the determination of impurities inhigh-purity sodium tungstate. Six elements (Co, Cu, Fe, Mn, Ni, and Pb) were coprecipitated bylanthanum hydroxide so as to be concentrated and separated from the tungsten matrix. Effects of somefactors on the recoveries of the analytes and on the residual amount of sodium tungstate wereinvestigated, and the optimum conditions for the coprecipitation were proposed. Matrix-matchingcalibration curve method was used for the analysis. It is shown that the elements mentioned abovecan be quantitatively recovered. The detection limits for Co, Cu, Fe, Mn, Ni, and Pb are 0.07, 0.4,0.2, 0.1, 0.6, and 1.3 μg·g^(-1), respectively. The recoveries vary from 92.5% to 108%, and therelative standard deviations (RSDs) are in the range of 3.1%-5.5%.

Effect of sodium tungstate on visual evoked potentials in diabetic rats

AIM： To evaluate the effect of sodium tungstate on visual evoked potentials（VEPs） in diabetic rats.· METHODS： Wistar rats were randomly divided into three groups as normal control, diabetic control and diabetic rats treated with sodium tungstate. Diabetes was induced by single intraperitoneal injection of streptozotocin（50 mg/kg）. Sodium tungstate [40 mg/（kg·d）]was administered for 12 wk and then VEPs were recorded.Additionally, thiobarbituric acid reactive substance（TBARS） levels were measured in brain tissues.·RESULTS： The latencies of P1, N1, P2, N2 and P3 waves were significantly prolonged in diabetic rats compared with control group. Diabetes mellitus caused an increase in the lipid peroxidation process that was accompanied by changes in VEPs. However, prolonged latencies of VEPs for all components returned to control levels in sodium tungstate-treated group. The treatment of sodium tungstate significantly decreased brain TBARS levels and depleted the prolonged latencies of VEP components compared with diabetic control group.· CONCLUSION： Sodium tungstate shows protective effects on visual pathway in diabetic rats, and it can be worthy of further study for potential use.

Hydrothermal Synthesis,Crystal Structure and Spectral Characterization of a New Copper Isopolytungstate: [Cu(phen)_3][W_6O_(19)]

An unusual inorganic-organic hybrid hexatungstate complex [Cu（phen）3][W6O19] 1 （C36H24 CuN6O19W6, Mr= 2011.20） was hydrothermally synthesized and characterized by singlecrystal X-ray diffraction, IR spectrum, UV-VIS spectrum and elemental analyses. This compound crystallizes in the monoclinic system, space group C2/c with a = 19.1005（11）, b = 11.2585（11）, c = 20.2867（15） A, β= 102.177（2）°, V= 4264.4 A^ 3, μ（MoKa） = 16.691 mm^-1, Dc = 3.133 g/cm^3, Z = 4, F（000） = 3628, the final R = 0.0338 and wR = 0.0798 for 4090 observed reflections with I 〉 2σ（I）. The result of structure determination shows that the crystal structure is constructed from [W6O19]^2- cluster anions and [Cu（phen）3]^2＋ complex fragments, which are held together into a three-dimensional network through hydrogen-bonding interactions.

NON-ISOTHERMAL KINETIC STUDY ON THE THERMAL DEHYDRATION OF SODIUM TUNGSTATE DIHYDRATE

１ＩＮＴＲＯＤＵＣＴＩＯＮＳｏｄｉｕｍｔｕｎｇｓｔａｔｅｄｉｈｙｄｒａｔｅｉｓｕｓｅｄｉｎｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆｃｏａｔｅｄｅｌｅｃｔｒｏｄｅｓｆｏｒｅｌｅｃｔｒｏｃａｔａｌｙｓｉｓ［１］ａｎｄａｓｆｉｒｅｒｅｔａｒｄａｎｔｆｏｒｆａｂｒ...

Expanded Industrial Experiments of Free-alkali Recovery from Sodium Tungstate Solution by the Membrane Electrolysis Process

The expanded industrial experiments were conducted with practical industrial liquor to separate free alkali from sodium tungstate solution by electrolysis with cation-exchange membrane. Experimental results show that on the condition that the temperature is 50-55 degreesC and the current density is 1000 A/m(2), the single electrolysis cell is operated stably and 80% free-alkali in mass fraction is separated from the anode feed liquor of sodium tungstate, with electric efficiency up to more than 88% and the unit energy consumption E lower than 1900 kWh/t; while three electrolysis cells in series are operated, under the condition that the temperature is 60-65 degreesC and the current density is 1000 A/m(2), the electric efficiency can reach higher than 88% and the unit energy consumption E can be lower than 2250 kWh/t.

New cadmium and rare earth metal tungstates with the scheelite type structure

New cadmium and rare earth metal tungstates with the formula Cd0.25RE0.50 0.25WO4 （RE=Nd, Sin, Eu, Gd, D-statistical distrib- uted vacancies in cation sublattice） were synthesized by the solid-state reaction between CdWO4 and corresponding RE2W209. The obtained phases crystallize in the scheelite type structure. The Cd0.25RE0.5 0.25WO4 compounds were characterized by X-ray diffractometer （XRD）, （DTA-TG）, infrared （IR） and EPR methods.

ELECTRODE SELECTION OF ELECTROLYSIS WITH MEMBRANE FOR SODIUM TUNGSTATE SOLUTION

Xiao Liansheng Wang Wei Zhang Qixiu Gong Bofan Cao Jiashu (Department of Metallurgical Science and Engineering, Central South University of Technology, Changsha 410083, China) Abstrac By measuring the electrode polarization curves of many kinds of materials and life spans of electrodes through intensifying electrolysis in the process, the appropriate electrode materials for different stages of electrolysis of sodium tungstate solution with membrane have been selected The effects of the electrodes with different shapes on electrolysis have been investigated. The result shows that network electrode is more suitable to electrolysis of sodium tungstate solution.

Preparation of High－purity Sodium Tungstate from Low－grade Tung－sten－concentrate with a High Content of Calcium and Other Impurities

A new technological process for production of talium tungstate from low-grade tungsten-concentrate witha high content of calcium and other impurities has been studied. The experiments showed that average tungstenleaching efficiency of more than 96. 92 % can be obtained with a low NaOH consumption by using the mechani-cal activating caustic decomposition , and the content of main impurities (P, As, Si) in Na_2WO_4 solution ob-tained is competitive with that from standard wolframite concentrate by traditional caustic decomposition. Afterrecovering caustic liquor by first crystallization, molylxlenum is removed from Na_2WO_4 solution by ion ex-change method. High-purity sodium tungstate is obtained by second crystallization of Na_2WO_4 solution. Thistechnology has the advantages of good adaptability for raw materials, high removing efficiency of impurities,high tungsten recovery and high economic benefit.

Luminescence properties of calcium tungstate activated by lanthanide(Ⅲ) ions

Calcium tungstate phosphors activated by the Ln3＋ ions （Ln-Pr, Nd, Tb, Yb） were synthesized by a traditional high-temperature solid-state method. The crystal structures and morphologies of the products were characterized by scanning electron microscopy （SEM）, X-ray powders diffraction （XRD） and infrared spectra （FT-1R）. The samples were fotmd to show luminescence properties （down-conversion, DC, at excitation wavelength 254 nm and up-conversion, UC, at excitation wavelength 980 nm）. CaWO4 doped with Tb3＋/yb3＋ showed green DC and UC luminescence characteristic of Tb（Ⅲ） ion in the range of 470-660 nm, cor- responding to the 5D4→7F6,5,4,3,2 electronic transition. CaWO4 doped with Pr3＋/Yb3＋ showed week blue, green and red （DC and UC） luminescence of Pr（Ⅲ） ion, in the wavelength region of 450-700 nm. Emission peaks were ascribed to the 3P1→3H4,5,6, 3P0→3H4,5,6, 3P1→3F2 and 3P0→3F2 transitions, respectively. CaWO4 doped with Nd3＋/yb3＋ phosphor emitted orange UC luminescence at 450-690 nm （2p3/2→4I15/2, 4G7/2→419/2,11/2,13/2） and strong near-infrared UC luminescence at 720-900 nm （4F7/2＋4S3/2→4419/2, 4F5/2＋2H3/2→419/2, 4F3/2→4I9/2） which is the characteristic of Nd（Ⅲ） ion.

Formation of CoAl layered double hydroxide on the boehmite surface and its role in tungstate sorption

Sorption of tungstate on boehmite（γ-Al OOH）is increased by co-sorption with Co^（2＋）over the near-neutral p H range.Batch uptake experiments show up to a 3-fold increase in tungstate uptake over the range WO4^（2-）=50–1000μmol/L compared to boehmite not treated with Co^（2＋）.Desorption experiments reveal a corresponding decrease in sorption reversibility for tungstate co-sorbed with Co^（2＋）.Reaction of boehmite with Co^（2＋）results in the formation of Co Al layered double hydroxide（LDH）,as confirmed by X-ray diffraction and X-ray absorption spectroscopy.Tungsten L3-edge X-ray absorption near edge structure（XANES）reveals that W（VI）is octahedrally coordinated in all sorption samples,with polymeric tungstate species forming at higher tungstate concentrations.X-ray diffraction and X-ray absorption spectroscopy indicate that the mechanism for enhancement of tungstate uptake is the formation of surface complexes on boehmite at low tungstate concentrations,while exchange into the Co Al LDH becomes important at higher tungstate concentrations.The results provide a basis for developing strategies to enhance tungstate sorption and to limit its environmental mobility at near-neutral pH conditions.

The growth units and hydrothermal preparation of lead tungstate (PbWO_4) crystallites

The crystal structure of lead tungstate (PbWO4) can be regarded as ordered combination of the tungsten oxide tetrahedrons (WO4) and lead ions (Pb2+). According to the growth unit model, the growth units of lead tungstate are the aggregations of the tungsten oxide tetrahedrons and lead cations with various geometry configurations. It is suggested that the favorable growth units of lead tungstate crystal are pyramidal, tetragonal prism and quadrangular units corresponding to geometric orientations of the simple forms of the crystal. Under low restricted growth conditions, the growth form of lead tungstate crystallites is the aggregation of the geometric configurations of these favorable growth units. The above conclusions are completely confirmed by the experiment on hydrothermal preparation of lead tungstate crystallites.

Luminescence properties of Tm^(3+) /Yb^(3+) ,Er^(3+) /Yb^(3+) and Ho^(3+) /Yb^(3+) activated calcium tungstate

CaWO4 phosphor activated by the Tm^3＋/Yb^3＋, Er^3＋/Yb^3＋ and Ho^3＋/Yb^3＋ ions were synthesized by a traditional high-temperature solid-state method. The crystal structures and morphologies of the products were characterized by X-ray powders diffraction method （XRD）, infrared spectra （FT-IR） and scanning electron microscopy （SEM）. The samples were found to show up-conversion luminescence properties. CaWO4 doped with Tm^3＋/Yb^3＋ showed blue luminescence characteristic of Tm（Ⅲ） ion in the range of 460-485 urn, corresponding to the ^1G4→^3H6 electronic transition. CaWO4 doped with Er^3＋/Yb^3＋ showed strong green luminescence at 510-565 nm （^2H11/2, ^4S3/2→^4I15/2） and weak red luminescence at 640-685 nm （^4F9/2→^4I15/2） of Er（Ⅲ） ion. CaWO4 doped with Ho^3＋/Yb^3＋ phosphor emitted green luminescence at 525-560 nm （5S2, 5F4→518） and red luminescence at 6304i70 um （SFs→518） and at 730-770 nm （^5S2, ^5F4→^5I7）, which is the characteristic of Ho（Ⅲ） ion.

Two-dimensional tungstate nanosheets for constructing novel photochromic hydrogel with ultrahigh flexibility

A hydrogel possessing interesting photochromic behaviors was developed by in situ ultraviolet(UV)irradiation-assisted polymerization of an aqueous solution of N-isopropylacrylamide monomer in the presence of cesium tungstate nanosheets.By this process,a hierarchical porous network structure was finely constructed while showing ultrahigh flexibility.More importantly,the newly prepared hydrogel retained the photochromic properties of the cesium tungstate nanosheets.The color transitions could be readily controlled by UV laser irradiation and were completely reversible via laser exposure or dark treatment.The nanocomposite hydrogel with its excellent photochromic properties and ultrahigh flexibility will have great applications in flexible photochromic devices.The synthetic procedure is simple and has promises to be extended to developing other hydrogels with various new functionalities.

Visible light-assisted peroxydisulfate activation via hollow copper tungstate spheres for removal of antibiotic sulfamethoxazole

The contamination of antibiotics in aqueous environment causes increasing concerns recently.Lightassisted activation of peroxydisulfate(PDS)has been demonstrated as an efficient technology for re moval of contamination in water.Herein,a hollow sphere of CuWO_(4)(h-CuWO_(4))was employed as a visible lightactivated photocatalyst for the activation of PDS,and following with high removal efficiency(98%)of antibiotic sulfamethoxazole(SMX).Under visible light irradiation,the degradation rate on hollow structures system is nearly 2 times higher than the traditional solid CuWO_(4) spheres.Furthermore,the underlying mechanism and detailed pathway of SMX degradation were proposed based on density functional theory(DFT)calculations and liquid chromatography-mass spectrometry(LC-MS).This work provides a new feasible way for advanced oxidation processes to remove antibiotics SMX in heterogeneous system,and open up new application possibilities of CuWO_(4)-based materials.

Shining light on transition metal tungstate-based nanomaterials for electrochemical applications:Structures,progress,and perspectives

Transition metal tungstate-based nanomaterials have become one of the research hotspots in electrochemistry due to their abundant natural resources,low costs,and environmental friendliness.Extensive studies have demonstrated their significant potentials for electrochemical applications,such as supercapacitors,Li-ion batteries,Na-ion batteries,electrochemical sensing,and electrocatalysis.Considering the rapidly growing research enthusiasm for this topic over the last several years,herein,a critical review of recent progress on the application of transition metal tungstates and their composites for electrochemical applications is summarized.The relationships between synthetic methods,nano/micro structures and electrochemical properties are systematically discussed.Finally,their promising prospects for future development are also proposed.It is anticipated that this review will inspire ongoing interest in rational designing and fabricating novel transition metal tungstate-based nanomaterials for high-performance electrochemical devices.

An environmentally friendly synthesis of 1,4-dihydropyrano[2,3-c]pyrazole derivatives catalyzed by tungstate sulfuric acid

An efficient three-component synthesis of 6-amino-4-aryl-5-cyano-3-metriyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazoles via a reaction between 3-methyl-1-phenyl-2-pyrazolin-5-one,aromatic aldehydes and malononitrile using tungstate sulfuric acid as a catalyst was described.Mild conditions,good to excellent yields,easily available catalyst and easy work-up are the key features of this method.

A comprehensive study on butanolysis of furfuryl alcohol to butyl levulinate using tungstated zirconia and sulfonated carbon catalysts

This work presents the formation of butyl levulinate,a potential fuel additive,and an excellent renewable chemical obtained by the butanolysis of furfuryl alcohol(FAL)over a solid acid catalyst.The butanolysis of furfuryl alcohol reaction is a strong function of acidity for which tungstated zirconia(WO_(3)-ZrO_(2)),a robust solid acid catalyst,and a sulfonated carbon catalyst were employed to produce high yields of butyl levulinate targeting a lower initial molar ratio of butanol to FAL.A maximum of 28 mol%yield of butyl levulinate was obtained with tungstated zirconia catalyst.Easily prepared sulfonated carbon catalyst at high reaction temperatures facilitated the complete conversion of reaction intermediate,2-butoxymethylfuran(2-BMF)through which butyl levulinate was formed,and as high as 80 mol%of butyl levulinate yield was produced at an initial mole ratio of 8.5:1 of butanol to FAL.The better results of sulfonated carbon catalyst could be attributed to the presence of-SO3H,carboxylic acid,and phenolic OH groups on the carbon surface.