Micellar Catalysis on the Redox Reaction of Ascorbic Acid-Vanadium(V) System

Stoichiometry of the redox reaction of vanadium(V) by ascorbic acid (H₂A) has been experimentally determined to be H₂A + 2V(V) → A + 2V(IV) + 2H ⁺ . Evidence of induced polymerization of acrylonitrile and the reduction of mercuric chloride indicates that a free-radical mechanism operates during the course of reaction. Vanadium(V) is only reduced to vanadium(IV). The kinetics of this redox reaction have been investigated spectrophotometrically at 35°C in acidic media of H₂SO₄. In this kinetic study we have observed the nature of vanadium(V)-H₂A interaction in presence of anionic surfactant of SDS. In V(V)-H₂A system, the addition of anionic surfactant (SDS) enhanced the reaction rate and shows catalytic effect. This trend was explained by the incorporation/solubilization of vanadium(V) and ascorbic acid in the Stern layer.     

Ag3PO4/Ag2S/g-C3N4复合光催化剂的制备与性能

通过沉积法和离子交换法成功地制备了Ag_3PO_4/Ag_2S/g-C_3N_4复合型光催化剂。利用X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、N_2吸附-脱附等温线、紫外-可见漫反射光谱、荧光光谱等手段对样品进行了表征。通过降解罗丹明B考察其可见光催化活性及稳定性,研究了硫化钠与磷酸银物质的量的比值(n_(Na_2S)/n_(Ag_3PO_4))、g-C_3N_4添加量对所制备复合光催化材料性能的影响,同时对光催化机理进行了探讨。结果表明,随着n_(Na2S)/n_(Ag3PO4)的增加,所得复合催化材料活性先增加后降低;当n_(Na2S)/n_(Ag_3PO_4)为1.5%、g-C_3N_4与Ag_3PO_4的质量比为3∶7时制备的催化剂ASC1.5的光催化活性最好,在可见光照射下,40 min内可将罗丹明B完全降解,且5次循环使用后仍保持较高的催化活性。和Ag_3PO_4相比,Ag_3PO_4/Ag_2S/g-C_3N_4复合型光催化材料的活性与稳定性都得到明显提高,这主要归因于复合催化剂比表面积和孔结构的增加,载流子分离效率的提高。光催化机理研究表明,空穴(h~+)、超氧阴离子自由基(·O~(2-))和羟基自由基(·OH)都是光催化过程中的主要活性物种。三者作用大小依次为:h~+·O~(2-)·OH。     

Testing the retardancy effect of various inorganic chemicals on smoldering combustion of Pinus halepensis needles

The fire retarding performance of 28 different inorganic chemical substances was tested by measuring the relative particle fire hazard properties of Pinus halepensis needles treated with these chemicals. The tests were performed using a new method, based on a specifically designed apparatus for monitoring the forest species temperature, under precisely controlled temperature and static air atmosphere conditions. The relative ignition and smoldering combustion properties determined were: the ignition delay time, the combustion rate, the heat content and the mass residue of forest samples. The key elements for the effectiveness of fire retardants were the delay of ignition and the reduction of heat and combustion rate. The chemicals examined were: Cu, Fe, Al₂O₃, Fe₂O₃, SiO₂·H₂O, NaHCO₃, KI, KBr, KCl, NaCl, CaCO₃, MnSO₄·5H₂O, CuSO₄·5H₂O, MgCl₂·6H₂O, Na₂B₄O₇·10H₂O, Na₂HPO₄, Na₂CO₃, Na₂SiO₃, ZnSO₄·7H₂O, Zn₃(PO₄)₂·2H₂O, NH₄Br, NH₄Cl, NH₄HCO₃, (NH₄)₂CO₃, NH₄H₂PO₄ (MAP), (NH₄)₂SO₄ (AS), (NH₄)₂HPO₄ (DAP) and a commercial retardant containing both DAP and AS. Among them the best performance was exhibited by ammoniac phosphates, followed by ammoniac sulfates and silica.     

Interaction Between Two Similar Plane Parallel Double Layers for (NH4)2Fe(SO4)2 or (NH4)2Cu(SO4)2 Type Complex Salt Electrolytes at Positive Surface Potential

Interaction energies between two similar plane parallel double layers for (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ type complex salt electrolytes at positive surface potential were expanded in a power series and accurate numeral results were given for 0.1 ≤ y _e  < y ₀ ≤ 20. The general expressions were given for the interaction energies of A _ν +B _ν′ +C_ν? type complex salt electrolytes at y > 0. The interaction energies for simple salts NaCl, CaCl₂, Na₂SO₄, FeCl₃, Na₃PO₄, Mg₃(PO₄)₂, Al₂(SO₄)₃, and complex salts (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ at y ₀ = 1 were compared. There was hardly difference between these simple salts and this complex salt for the interaction energies. The interaction energy for complex salt (NH₄)₂Fe(SO₄)₂ was close to that for simple salt Na₃PO₄.

Supplemental files are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.     

Les systemes binaires AlPO4−M3PO4 (M=Li,Na, K)

The liquid-solid phase diagram of the binary systems AlPO₄?M₃PO₄(M=Li, Na, K) have been established. The additional compounds Na₃Al(PO₄)₂, Na₃Al₂(PO₄)₃ and K₃Al₂(PO₄)₃ have been found again. A new compound K₃Al(PO₄)₂ is observed. The melting point of Na₃PO₄ is 1545°C and K₃PO₄ does not melt up to 1700°C.     

Carbon coated Na3V2(PO4)3 as novel electrode material for sodium ion batteries

A Na₃V₂(PO₄)₃ sample coated uniformly with a layer of 6 nm carbon has been successfully synthesized by a one-step solid state reaction. This material shows two flat voltage plateaus at 3.4 V vs. Na⁺/Na and 1.63 V vs. Na⁺/Na in a nonaqueous sodium cell. When the Na₃V₂(PO₄)₃/C sample is tested as a cathode in a voltage range of 2.7-3.8 V vs. Na⁺/Na, its initial charge and discharge capacities are 98.6 and 93 mAh/g. The capacity retention of 99% can be achieved after 10 cycles. The electrode shows good cycle performance and moderate rate performance. When it is tested as an anode in a voltage range of 1.0-3.0 V vs. Na⁺/Na, the initial reversible capacity is 66.3 mAh/g and the capacity of 59 mAh/g can be maintained after 50 cycles. These preliminary results indicate that Na₃V₂(PO₄)₃/C is a new promising material for sodium ion batteries.     

Incorporation of cesium ion from CsNO3 into NH4Zr2(PO4)3 studied by TG-IR spectroscopy and powder XRD

The incorporation mechanism of Cs⁺ ions from CsNO₃ into NH₄Zr₂(PO₄)₃ was studied on a mixture of CsNO₃ and NH₄Zr₂(PO₄)₃ by powder X-ray diffraction analysis and by monitoring off-gases released from the mixture upon heating with a thermogravimetry analyzer connected to an infrared spectrometer. With increasing temperature, the decomposition of CsNO₃ first started, followed by the conversion of NH₄Zr₂(PO₄)₃ to HZr₂(PO₄)₃ with the release of NH₃. At around 500°C, the Cs Zr₂(PO₄)₃ phase started to appear as a result of the H⁺/Cs⁺ ion exchange. No Cs⁺ ion loss was observed at thermal treatment temperatures of 900°C and lower.     

可见光响应的Co3(PO4)2/Ag3PO4纳米复合光催化剂的制备及表征

采用简单的化学偏聚法合成出Ag₃PO₄纳米颗粒、磷酸钴（Co₃（PO₄）₂,CoP）纳米片以及它们两者的纳米复合结构（CoP/Ag₃PO₄）,同时还比较了它们的可见光催化活性. 采用场发射扫描电镜（FESEM）、X 射线衍射（XRD）、紫外-可见（UV-Vis）吸收光谱以及光致发光谱等手段对其形貌、结构、光学以及可见光催化性能等进行表征. 结果表明,CoP/Ag₃PO₄复合纳米结构的可见光降解甲基橙（MO）的速率和循环稳定性均明显优于其它两种物质. 这表明CoP应该起着共催化剂的作用,它能够抑制光生电子与空穴之间的复合,并且提供大量高活性的光生空穴. 此外,我们还发现CoP/Ag₃PO₄降解另一种阳离子型染料——罗丹明B（RhB）的能力则远不如纯Ag₃PO₄,这可能是与光催化剂的表面性质发生改变有关,造成更低的RhB吸附能力. 本文提供了一种廉价制备高效可见光催化剂的新方法.     

Chromium(III) Hydroxide Solubility in The Aqueous Na+-OH?-H2PO?4-HPO2?4-PO3?4-H2O System: A Thermodynamic Model

Chromium(III)-phosphate reactions are expected to be important in managing high-level radioactive wastes stored in tanks at many DOE sites. Extensive studies on the solubility of amorphous Cr(III) solids in a wide range of pH (2.8–14) and phosphate concentrations (10^–4 to 1.0 m) at room temperature (22±2)°C were carried out to obtain reliable thermodynamic data for important Cr(III)-phosphate reactions. A combination of techniques (XRD, XANES, EXAFS, Raman spectroscopy, total chemical composition, and thermodynamic analyses of solubility data) was used to characterize solid and aqueous species. Contrary to the data recently reported in the literature,⁽¹⁾ only a limited number of aqueous species [Cr(OH)₃H₂PO^–₄, Cr(OH)₃(H₂PO₄)^2–₂), and Cr(OH)₃HPO^2–₄] with up to about four orders of magnitude lower values for the formation constants of these species are required to explain Cr(III)-phosphate reactions in a wide range of pH and phosphate concentrations. The log K^o values of reactions involving these species [Cr(OH)₃(aq)+H₂PO^–₄&#x21CC;Cr(OH)₃H₂PO^–₄; Cr(OH)₃(aq)+2H₂PO^–₄&#x21CC;Cr(OH)₃(H₂PO₄)^2–₂; Cr(OH)₃(aq)+HPO^2–₄&#x21CC;Cr(OH)₃HPO^2–₄] were found to be 2.78±0.3, 3.48±0.3, and 1.97±0.3, respectively.     

Gases Released During the Conversion of NH4Zr2(PO4)3 to HZr2(PO4)3

Gases released during the conversion of NH₄Zr₂(PO₄)₃ to HZr₂(PO₄)₃ were identified using an apparatus in which gases released from a sample placed in a thermogravimetric analyzer were directly introduced to a gas cell of an IR spectrometer. Such acidic gases as N₂O and NO were detected besides the basic NH₃ gas, and their formation mechanism was discussed.This revised version was published online in November 2005 with corrections to the Cover Date.     

ChemInform Abstract: Isomorphous Substitution of Rare‐Earth Elements in Lacunary Apatite Pb8Na2(PO4)6.

Pb_8‐xLn_xNa₂(PO₄)₆ (x = 0—2.0; Ln: Y, La, Pr—Ho, Tm—Yb) with void structural channels are prepared by solid state reaction of PbO, Na₂CO₃, (NH₄)₂HPO₄, and Ln oxides (Al₂O₃ crucible, 800 °C, 2—10 d).     

A novel chain-like molybdenum phosphate: hydrothermal synthesis,crystal structure and characterization of [NH3(CH2CH2)2NH3]3[NH3(CH2CH2)2NH2]-Na5[Mo6O12(OH)3(PO4)(HPO4)3]2·4H2O

A novel organic/inorganic hybrid molybdenum phosphate, [NH₃(CH₂CH₂)₂NH₃]₃[NH₃(CH₂CH₂)₂NH₂]Na₅-[Mo₆O₁₂(OH)₃(PO₄)(HPO₄)₃]₂·4H₂O (1), involving molybdenum presented in V oxidation, has been hydrothermally prepared and characterized by elemental analysis, i.r., u.v.–vis., x.p.s., t.g. and single crystal X-ray diffraction. The structure of the title compound (1) may be considered to consist of two [Mo₆O₁₂(OH)₃(PO₄)(HPO₄)₃] units bonded together with NaO₆ octahedra, forming dimers. Further, these dimers connect with each other through four Na⁺ cations as bridges, giving rise to novel one-dimensional chain-like skeleton. Piperazines exist among inorganic chains acting as charge balancing cations.     

Two caesium vanadium hydrogenphosphates with tunnelled structures: Cs2V2O3(PO4)(HPO4) and Cs2[(VO)3(HPO4)4(H2O)]·H2O

Dicaesium divanadium trioxide phosphate hydrogenphosphate, Cs₂V₂O₃(PO₄)(HPO₄), (I), and dicaesium tris[oxidovanadate(IV)] hydrogenphosphate dihydrate, Cs₂[(VO)₃(HPO₄)₄(H₂O)]·H₂O, (II), crystallize in the monoclinic system with all atoms in general positions. The structures of the two compounds are built up from VO₆ octahedra and PO₄ tetrahedra. In (I), infinite chains of corner‐sharing VO₆ octahedra are connected to V₂O₁₀ dimers by phosphate and hydrogenphosphate groups, while in (II) three vanadium octahedra share vertices leading to V₃O₁₅(H₂O) trimers separated by hydrogenphosphate groups. Both structures show three‐dimensional frameworks with tunnels in which Cs⁺ cations are located.     

Topotactic insertion of lithium in the layered structure Li4VO(PO4)2: The tunnel structure Li5VO(PO4)2

A new V(III) lithium phosphate Li₅VO(PO₄)₂ has been synthesized by electrochemical insertion of lithium into Li₄VO(PO₄)₂. This phase, which crystallizes in the space group I4/mcm, exhibits a tunnel structure closely related to the layered structure of Li₄VO(PO₄)₂ and to the tunnel structure of VO(H₂PO₄)₂. The topotactic reactions that take place during lithium exchange and intercalation, starting from VO(H₂PO₄)₂ and going to the final phase Li₅VO(PO₄)₂ are explained on the basis of the flexible coordinations of V⁴⁺ and V³⁺ species. The electrochemical and magnetic properties of this new phase are also presented and explained on the basis of the structure dimensionality.     

Counter-current extraction process for recovery of U(IV) from phosphoric acid using octylphenyl acid phosphate (OPAP) extractant

The extraction of U(IV) from phosphoric acid by octylphenyl acid phosphate (OPAP) in kerosene was investigated. Parameters affecting the extraction of U(IV) from phosphoric acid were investigated. The effects of H₃PO₄, H₂SO₄, H₂O₂, Na₂CO₃ and (NH₄)₂CO₃ concentrations, phase ratio and temperature on the stripping of uranium from the organic phase were studied. Based on the bench-scale results, a continuous counter-current extraction flow sheet was developed and tested using a 16-stage horizontal type mixer settler. The continuous extraction scrubbing stripping showed that the extraction efficiency of the developed process is 99%, whereas the stripping efficiency is 97%.     

Gelled Na<Subscript>2</Subscript>HPO<Subscript>4</Subscript> · 12H<Subscript>2</Subscript>O with amylose-g-sodium acrylate: heat storage performance,heat capacity and heat of fusion

A novel gelling method was studied to stabilize phase change material Na₂HPO₄ · 12H₂O with amylose grafted sodium acrylate. Gelled Na₂HPO₄ · 12H₂O shows stable heat storage performance prepared at optimized conditions: 2.7mass/mass% sodium acrylate, 0.4 mass/mass% amylose, 0.05–0.09 mass/mass% N, N′-methylenebisacrylamide, 0.05–0.09 mass/mass% K₂S₂O₈ and Na₂SO₃ (mass ratio 1:1), at 50 °C. Na₂HPO₄ · 12H₂O was dispersed in gel network as tiny crystals less than 0.1 mm. Melting points were in the range 35.4 ± 2 °C. Short-term thermal cycling proves the effectiveness of the novel method for eliminating phase separation in the gelled salt. Adiabatic calorimetric measurement of heat capacities shows two phase transitions, which correspond to melting of Na₂HPO₄ · 12H₂O and freezable bond water in gel, respectively. Heat of fusion of pure Na₂HPO₄ · 12H₂O was determined as 260.9 J g⁻¹. Distribution of extra water is: free water:freezable water:nonfreezing water = 0:0.85:0.15.     

A new whitlockite,Ca8.42Na1.16V(PO4)7

Single crystals of a new complex phosphate, calcium sodium vanadium phosphate, Ca_8.42Na_1.16V(PO₄)₇, have been grown from a melt under an inert atmosphere. The crystal structure has rhombohedral (R3c) symmetry and belongs to the whitlockite structure type. Vanadium(III) ions occupy nearly regular octa­hedral sites (M5 with 3 point symmetry), which share corners with six PO₄ tetra­hedra to form isolated units. The calcium ions occupy eight‐ and nine‐coordinated sites. The sodium ions partially occupy one octa­hedral position and share one nine‐coordinated position with a Ca atom.     

A new structure type of phosphate: Crystal structure of Na2Zn5(PO4)4

A new compound, Na₂Zn₅(PO₄)₄, was identified in the system ZnONa₂OP₂O₅ and high-quality crystal was obtained by the melt method. The crystal structure of this compound was solved by direct method from single crystal X-ray diffraction data. The structure was then refined anisotropically using a full-matrix least square refinement on F² and the refinement converged to R₁=0.0233 and wR₂=0.0544. This compound crystallizes in the orthorhombic system with space group Pbcn, lattice parameters a=10.381(2) Å, b=8.507(1) Å, c=16.568(3) Å and Z=4. The structure is made up of 3D [Zn₅P₄O₁₆]_n²ⁿ⁻ covalent framework consisting of [Zn₄P₄O₁₆]_n⁴ⁿ⁻ layers. The powder diffraction pattern of Na₉Zn₂₁(PO₄)₁₇ is explained by simulating a theoretical pattern with NaZnPO₄ and Na₂Zn₅(PO₄)₄ in the molar ratio of 1:4 and then by Rietveld refinement of experimental pattern. Na₂Zn₅(PO₄)₄ melts congruently at 855 °C and its conductivity is 5.63×10⁻⁹ S/cm.     

溶胶-凝胶法制备Li3V2(PO4)3及其性能研究

0引言具有类NASICON结构的Li3V2(PO4)3是继过渡金属氧化物LMO后的一种新型的锂离子二次电池正极材料。与目前市场上应用最为广泛的正极材料LiCoO2相比,Li3V2(PO4)3具有超常的稳定性,即使在脱出的Li 与过渡金属原子的物质的量之比大于1的时候仍然具有超乎寻常的稳定性,而通常情况下1mol LiCoO2在脱出0.5mol Li 就会变得不稳定。并且Co是一种战略物资,全球储量十分有限;Co也是一种有毒金属,对于环境污染较为严重。LiNiO2因其合成较为困难而使应用受限,尖晶石LiMn2O4虽然属于环境友好型化合物,但其理论比容量仅为148mAh·g-1,且…     

电池正极材料Li3V2(PO4)3/C的水热合成和性能

以LiOH·H2O, NH4VO3, NH4H2PO4 和麦芽糖等为原料, 采用水热法合成了碳包覆的磷酸钒锂化合物, 考察了碳含量对材料电化学性能的影响. 利用XRD, TEM, SEM和恒流充放电测试等手段对产物的结构、 形貌和电化学性能进行表征. 结果表明, 在650℃煅烧的样品为单一纯相的单斜晶体结构. 晶体颗粒分布为100~300 nm, 粒度分散均匀, 分散性良好, 无团聚现象, 且在颗粒表面包覆了一层无定形碳, 这有利于改善材料的导电率. 含碳量为10.23%的样品, 在倍率1.0C的电流密度下, 在3.0~4.3 V电压范围内, 样品的首次放电比容量高达118.8 mA·h/g, 循环15圈后放电比容量为115.1 mA·h/g, 容量保持率为96.88%.