The thermodynamic equilibrium diagrams of Mg2＋- 3-4PO - ＋4NH -H2O system at 298 K were established based on the thermodynamic calculation. From the diagram, the thermodynamic conditions for removing phosphorus from ...The thermodynamic equilibrium diagrams of Mg2＋- 3-4PO - ＋4NH -H2O system at 298 K were established based on the thermodynamic calculation. From the diagram, the thermodynamic conditions for removing phosphorus from the tungstate solution by magnesium salt precipitation were obtained. The results show that when the concentration of total magnesium increases from 0.01 mol/L to 1.0 mol/L, the optimal pH for the phosphorus removal by magnesium phosphate decreases from 9.8 to 8.8. The residual concentration of total phosphorus almost keeps the level of 4.0×10-6 mol/L in the system. MgHPO4, Mg3（PO4）2 and the mixture of Mg3（PO4）2 and Mg（OH）2 are stabilized in these system, respectively. However, increasing the total concentration of magnesium has little effect on phosphorus removal by magnesium ammonium phosphate, while it is helpful for phosphorus removal by increasing the total ammonia concentration. The calculated results demonstrate that the residual concentration of total phosphorus can decrease to 5.0×10-7 mol/L as the total concentration of ammonia reaches 5.0 mol/L and the optimal pH value is 9-10. Finally, verification experiments were conducted with home-made ammonium tungstate solution containing 50 g/L WO3 and 13 g/L P. The results show that when the dosage of MgCl2 is 1.1 times of the theoretical amount, the optimum pH for removing phosphorus is 9.5, which matches with the results of the theoretical calculation exactly.展开更多
An adsorbent, Na1.6Al0.6Ti1.4（PO4）3 （or NATP）, was prepared by controlled crystallization of glasses in the Na2O-Al2O3-CaO-TiO2-P2O5 system. The crystalline phases characterized by X-ray diffraction （XRD） show t...An adsorbent, Na1.6Al0.6Ti1.4（PO4）3 （or NATP）, was prepared by controlled crystallization of glasses in the Na2O-Al2O3-CaO-TiO2-P2O5 system. The crystalline phases characterized by X-ray diffraction （XRD） show that the sample glasses crystallizes into two phases, i.e. NATP and Ca9Al（PO4）7, while the Ca9Al（PO4）7 phase can be leached selectively with HCl, leaving a massive number of pores in the material. Through the experimental research, the effects of contact time, solution pH, and the initial concentration of Na＋on the cation exchange properties were investigated. The batch sorption kinetics and equilibria can be described by Pseudo-second-order kinetic equations and Langmuir isotherm equations respectively. Furthermore, the experiments with an industrial solution show that the removal rate of sodium from industrial （NH4）2WO4 is higher than 97%. Cycle experiment also shows that the NATP has a good cyclic performance.展开更多
A mononuclear tungsten-benzilate, (NH4)2[WO2(Ph2COCOO)2]?H2O was ob- tained by the reaction of ammonium tungstate(VI) with excess benzilic acid in ethanol solution at pH 5~6. The title compound crystallizes in monocli...A mononuclear tungsten-benzilate, (NH4)2[WO2(Ph2COCOO)2]?H2O was ob- tained by the reaction of ammonium tungstate(VI) with excess benzilic acid in ethanol solution at pH 5~6. The title compound crystallizes in monoclinic system, space group P21/n with a = 8.1078(5), b = 25.797(2), c = 13.6815(8) ? b = 91.001(1)? V = 2861.1(3) 3, Dc = 1.719 g/cm3, F(000) = 1472, C28H32N2O10W, Mr = 740.41, m(MoKa) = 4.097 mm-1 and Z = 4. The full-matrix least-squares refinement resulted in R = 0.033 and Rw = 0.068 for 3974 observed reflections with I >2s(I). The tungsten atom is six-coordinated by two cis-oxo groups and two bidentate benzilate ligands through deprotonated a-alkoxyl and a-carboxyl groups, forming a stable five-membered chelate ring. The compound has a distorted octahedral geometry, which is mainly attributable to the bulky ligand-ligand repulsions.展开更多
The photocatalytic degradation of norfloxacin by bismuth tungstate(Bi2WO6)with different hierarchical architectures wasinvestigated under visible light irradiation.Bi2WO6was prepared by hydrothermal method with the re...The photocatalytic degradation of norfloxacin by bismuth tungstate(Bi2WO6)with different hierarchical architectures wasinvestigated under visible light irradiation.Bi2WO6was prepared by hydrothermal method with the reaction solution pH rangingfrom4to11.The relatively ultrathin Bi2WO6nanoflakes prepared at pH4showed excellent adsorption and photodegradationefficiency towards norfloxacin.The characterization results showed that Bi2WO6prepared at pH4had a larger specific area andfaster photo-generated carrier separation rate.The decay rate reached the maximum in weak alkaline reaction solution,which couldbe attributed to the presence of moderate OH-anions.The present study demonstrated that the smaller size of Bi2WO6could be anefficient photocatalyst on the degradation of norfloxacin in the aquatic environment.展开更多
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 charact...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.展开更多
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 ...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.展开更多
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...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.展开更多
In this work,the tunable introduction of oxygen vacancies in bismuth tungstate was realized via asimple solvothermal method with the assistance of iodine doping.With the predictions afforded bytheoretical calculations...In this work,the tunable introduction of oxygen vacancies in bismuth tungstate was realized via asimple solvothermal method with the assistance of iodine doping.With the predictions afforded bytheoretical calculations,the as-prepared bismuth tungstate was characterized using various tech-niques,such as X-ray diffraction,Raman spectroscopy,scanning electron microscopy,transmissionelectron microscopy,X-ray photoelectron spectroscopy,electron spin resonance spectroscopy,anduV-Vis diffuse reflectance spectroscopy.The different concentrations of the oxygen vacancies onbismuth tungstate were found to be intensely correlated with iodine doping,which weakened thelattice oxygen bonds.Owing to the sufficient oxygen vacancies introduced in bismuth tungstate as aresult of iodine doping,the molecular oxygen activation was remarkably enhanced,thus endowingbismuth tungstate with high activity for the photocatalytic degradation of sodium pentachloro-phenate.More encouraging is the total organic carbon removal rate of sodium pentachlorophenateover iodine-doped bismuth tungstate that exceeded 90%in only 2 h and was 10.6 times higher thanthat of the pristine bismuth tungstate under visible light irradiation.Moreover,the mechanism,through which the degradation of sodium pentachlorophenate over iodine-doped bismuth tung-state is enhanced,was speculated based on the results of radical detection and capture experiments.This work provides a new perspective for the enhanced photocatalytic degradation of organochlo-rine pesticides from the oxygen vacancy-induced molecular oxygen activation over iodine-dopedbismuth tungstate.展开更多
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 ac...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.展开更多
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...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.展开更多
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...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%.展开更多
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 contaminatio...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.展开更多
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 c...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.展开更多
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 t...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.展开更多
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-V...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.展开更多
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 ...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.展开更多
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...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.展开更多
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 usi...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.展开更多
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 polari...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.展开更多
基金Project(2012BAB10B04)supported by the National Key Technologies R&D Program of China
文摘The thermodynamic equilibrium diagrams of Mg2＋- 3-4PO - ＋4NH -H2O system at 298 K were established based on the thermodynamic calculation. From the diagram, the thermodynamic conditions for removing phosphorus from the tungstate solution by magnesium salt precipitation were obtained. The results show that when the concentration of total magnesium increases from 0.01 mol/L to 1.0 mol/L, the optimal pH for the phosphorus removal by magnesium phosphate decreases from 9.8 to 8.8. The residual concentration of total phosphorus almost keeps the level of 4.0×10-6 mol/L in the system. MgHPO4, Mg3（PO4）2 and the mixture of Mg3（PO4）2 and Mg（OH）2 are stabilized in these system, respectively. However, increasing the total concentration of magnesium has little effect on phosphorus removal by magnesium ammonium phosphate, while it is helpful for phosphorus removal by increasing the total ammonia concentration. The calculated results demonstrate that the residual concentration of total phosphorus can decrease to 5.0×10-7 mol/L as the total concentration of ammonia reaches 5.0 mol/L and the optimal pH value is 9-10. Finally, verification experiments were conducted with home-made ammonium tungstate solution containing 50 g/L WO3 and 13 g/L P. The results show that when the dosage of MgCl2 is 1.1 times of the theoretical amount, the optimum pH for removing phosphorus is 9.5, which matches with the results of the theoretical calculation exactly.
基金Project(2012AA063205)supported by the High-tech Research and Development Program of China
文摘An adsorbent, Na1.6Al0.6Ti1.4（PO4）3 （or NATP）, was prepared by controlled crystallization of glasses in the Na2O-Al2O3-CaO-TiO2-P2O5 system. The crystalline phases characterized by X-ray diffraction （XRD） show that the sample glasses crystallizes into two phases, i.e. NATP and Ca9Al（PO4）7, while the Ca9Al（PO4）7 phase can be leached selectively with HCl, leaving a massive number of pores in the material. Through the experimental research, the effects of contact time, solution pH, and the initial concentration of Na＋on the cation exchange properties were investigated. The batch sorption kinetics and equilibria can be described by Pseudo-second-order kinetic equations and Langmuir isotherm equations respectively. Furthermore, the experiments with an industrial solution show that the removal rate of sodium from industrial （NH4）2WO4 is higher than 97%. Cycle experiment also shows that the NATP has a good cyclic performance.
基金This work was supported by the Ministry of Science & Technology of China (001CB108906) and the National Natural Science Foundation of China (29933040)
文摘A mononuclear tungsten-benzilate, (NH4)2[WO2(Ph2COCOO)2]?H2O was ob- tained by the reaction of ammonium tungstate(VI) with excess benzilic acid in ethanol solution at pH 5~6. The title compound crystallizes in monoclinic system, space group P21/n with a = 8.1078(5), b = 25.797(2), c = 13.6815(8) ? b = 91.001(1)? V = 2861.1(3) 3, Dc = 1.719 g/cm3, F(000) = 1472, C28H32N2O10W, Mr = 740.41, m(MoKa) = 4.097 mm-1 and Z = 4. The full-matrix least-squares refinement resulted in R = 0.033 and Rw = 0.068 for 3974 observed reflections with I >2s(I). The tungsten atom is six-coordinated by two cis-oxo groups and two bidentate benzilate ligands through deprotonated a-alkoxyl and a-carboxyl groups, forming a stable five-membered chelate ring. The compound has a distorted octahedral geometry, which is mainly attributable to the bulky ligand-ligand repulsions.
基金Projects(51579096,51222805,51521006,51508175) supported by the National Natural Science Foundation of ChinaProject supported by the National Program for Support of Top-Notch Young Professionals of China+1 种基金Project(NCET–11–0129) supported by the Program for New Century Excellent Talents in University from the Ministry of Education of ChinaProject(CX2015B095) supported by the Hunan Province Innovation Foundation for Postgraduate,China
文摘The photocatalytic degradation of norfloxacin by bismuth tungstate(Bi2WO6)with different hierarchical architectures wasinvestigated under visible light irradiation.Bi2WO6was prepared by hydrothermal method with the reaction solution pH rangingfrom4to11.The relatively ultrathin Bi2WO6nanoflakes prepared at pH4showed excellent adsorption and photodegradationefficiency towards norfloxacin.The characterization results showed that Bi2WO6prepared at pH4had a larger specific area andfaster photo-generated carrier separation rate.The decay rate reached the maximum in weak alkaline reaction solution,which couldbe attributed to the presence of moderate OH-anions.The present study demonstrated that the smaller size of Bi2WO6could be anefficient photocatalyst on the degradation of norfloxacin in the aquatic environment.
文摘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.
基金support of NSFC 51702284Fundamental Research Funds for the Central Universities (112109*172210171)+2 种基金the Startup Foundation for Hundred-Talent Program of Zhejiang University (112100-193820101/001/022)support of the NSFC 21501138the Science Research Foundation of Wuhan Institute of Technology (K201513)
文摘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.
基金supported by the National Science Foundation, Grant No. CHE0714183supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886+1 种基金supported by the U.S. DOE under Contract No. DE-AC02-06CH11357Additional support was provided by the National Research Foundation of Korea grant funded by the Korean government (MSIP) (No. 2014R1A2A2A01007294)
文摘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.
文摘In this work,the tunable introduction of oxygen vacancies in bismuth tungstate was realized via asimple solvothermal method with the assistance of iodine doping.With the predictions afforded bytheoretical calculations,the as-prepared bismuth tungstate was characterized using various tech-niques,such as X-ray diffraction,Raman spectroscopy,scanning electron microscopy,transmissionelectron microscopy,X-ray photoelectron spectroscopy,electron spin resonance spectroscopy,anduV-Vis diffuse reflectance spectroscopy.The different concentrations of the oxygen vacancies onbismuth tungstate were found to be intensely correlated with iodine doping,which weakened thelattice oxygen bonds.Owing to the sufficient oxygen vacancies introduced in bismuth tungstate as aresult of iodine doping,the molecular oxygen activation was remarkably enhanced,thus endowingbismuth tungstate with high activity for the photocatalytic degradation of sodium pentachloro-phenate.More encouraging is the total organic carbon removal rate of sodium pentachlorophenateover iodine-doped bismuth tungstate that exceeded 90%in only 2 h and was 10.6 times higher thanthat of the pristine bismuth tungstate under visible light irradiation.Moreover,the mechanism,through which the degradation of sodium pentachlorophenate over iodine-doped bismuth tung-state is enhanced,was speculated based on the results of radical detection and capture experiments.This work provides a new perspective for the enhanced photocatalytic degradation of organochlo-rine pesticides from the oxygen vacancy-induced molecular oxygen activation over iodine-dopedbismuth tungstate.
文摘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.
基金financially supported by the National Natural Science Foundation of China(21875265,22293015,22121002)。
文摘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.
文摘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%.
基金the Guangdong Basic and Applied Basic Research Foundation(No.2020B1515020038)。
文摘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.
文摘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.
基金Supported by the Research Foundation of Akdeniz University,Turkey
文摘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.
文摘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.
文摘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.
文摘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.
文摘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.
文摘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.
