Preparation of Zr(IV)/Nb(V) Nasicon-like phosphates by a sol-gel method

The NbZr(PO₄)₃ and Na_0.5Nb_0.5Zr_1.5(PO₄)₃ Nasicon-like phases were prepared by the sol-gel method using (NH₄)₃ [NbO(C₂O₄)₃]·1.5H₂O, ZrOCl₂·8H₂O and NH₄H₂PO₄ in oxalic or tartaric acid mediums. The thermal evolution of the xerogels prepared was followed by XRD and IR techniques. Depending on reaction conditions, such as, pH and Zr⁴⁺/organic acid ratio, pure Nasicon-like phases can be prepared at different temperatures.     

Formation of titanium phosphate composites during phosphoric acid decomposition of natural sphene

Decomposition of mineral sphene, CaTiOSiO₄, by H₃PO₄ is investigated in detail. During the dissolution process, simultaneous calcium leaching and formation of titanium phosphate (TiP) take place. The main product of decomposition is a solid titanium phosphate-silica composite. The XRD, solid-sate NMR, IR, TGA, SEM and BET data were used to identify and characterize the composite as a mixture of crystalline Ti(HPO₄)₂·H₂O and silica. When 80% phosphoric acid is used the decomposition degree is higher than 98% and calcium is completely transferred into the liquid phase. Formation of Ti(HPO₄)₂·H₂O proceeds via formation of meta-stable titanium phosphate phases, Ti(H₂PO₄)(PO₄)·2H₂O and Ti(H₂PO₄)(PO₄).The sorption affinities of TiP composites were examined in relation to caesium and strontium ions. A decrease of H₃PO₄ concentration leads to formation of composites with greater sorption properties. The maximum sorption capacity of TiP is observed when 60% H₃PO₄ is used in sphene decomposition.The work demonstrates a valuable option within the Ti(HPO₄)₂·H₂O-SiO₂ composite synthesis scheme, to use phosphoric acid flows for isolation of CaHPO₄·2H₂O fertilizer.     

Hydrothermal synthesis and morphology variation of cadmium hydroxyapatite

Cadmium hydroxyapatite (Cd-Hap) crystals were synthesized by hydrothermal method at 200 °C using the solutions of Cd(NO₃)₂·4H₂O and (NH₄)₂HPO₄. Influences of pH values and reaction time on the crystalline phases and morphology of the products were investigated. In low pH reaction media, Cd₅H₂(PO₄)₄·4H₂O was formed and a relatively high pH reaction media was necessary to obtain Cd-Hap. Morphology of the Cd-Hap crystals changed from stubby hexagonal prismatic to rod-like in shape with the increase in the pH value. This morphological change was explained by the difference in growth mechanism through intermediate phases, Cd₅H₂(PO₄)₄·4H₂O in the low pH reaction media and Cd₂P₂O₇·5H₂O in the high pH reaction media.     

Non-isothermal kinetics of thermal decomposition of NH<Subscript>4</Subscript>ZrH(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>·H<Subscript>2</Subscript>O

Nanocrystalline NH₄ZrH(PO₄)₂·H₂O was synthesized by solid-state reaction at low heat using ZrOCl₂·8H₂O and (NH₄)₂HPO₄ as raw materials. X-ray powder diffraction analysis showed that NH₄ZrH(PO₄)₂·H₂O was a layered compound with an interlayer distance of 1.148 nm. The thermal decomposition of NH₄ZrH(PO₄)₂·H₂O experienced four steps, which involves the dehydration of the crystal water molecule, deamination, intramolecular dehydration of the protonated phosphate groups, and the formation of orthorhombic ZrP₂O₇. In the DTA curve, the three endothermic peaks and an exothermic peak, respectively, corresponding to the first three steps' mass losses of NH₄ZrH(PO₄)₂·H₂O and crystallization of ZrP₂O₇ were observed. Based on Flynn–Wall–Ozawa equation and Kissinger equation, the average values of the activation energies associated with the NH₄ZrH(PO₄)₂·H₂O thermal decomposition and crystallization of ZrP₂O₇ were determined to be 56.720 ± 13.1, 106.55 ± 6.28, 129.25 ± 4.32, and 521.90 kJ mol⁻¹, respectively. Dehydration of the crystal water of NH₄ZrH(PO₄)₂·H₂O could be due to multi-step reaction mechanisms: deamination of NH₄ZrH(PO₄)₂ and intramolecular dehydration of the protonated phosphate groups from Zr(HPO₄)₂ are simple reaction mechanisms.     

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.     

Thermodynamics of aqueous solutions of poly ethylene glycol di-methyl ethers in the presence or absence of ammonium phosphate salts

Precise measurements of density and sound velocity at different temperatures ranging from 283.15 to 308.15 K for solutions of PEGDME250, PEGDME500 and PEGDME2000 in water and of PEGDME500 in aqueous solutions of 0.500 mol kg⁻¹ ammonium di-hydrogen phosphate ((NH₄)H₂PO₄) and di-ammonium hydrogen phosphate ((NH₄)₂HPO₄), binodal curves at temperature ranges 293.15-318.15 K for the aqueous PEGDME500 + (NH₄)₂HPO₄, PEGDME500 + (NH₄)₃PO₄, PEGDME2000 + (NH₄)H₂PO₄, PEGDME2000 + (NH₄)₂HPO₄, PEGDME2000 + (NH₄)₃PO₄ and PPG400 + (NH₄)₂HPO₄ two-phase systems, and liquid-liquid equilibrium data at temperature ranges 298.15-318.15 K for the aqueous PEGDME500 + (NH₄)₂HPO₄ and PEGDME2000 + (NH₄)₂HPO₄ two-phase systems have been taken. From the experimental density and sound velocity data, the apparent specific volume, excess specific volume, isentropic compressibility and isentropic compressibility deviation values have been determined and the effect of temperature, charge on the anion of electrolytes and molar mass of PEGDME on the volumetric and compressibility properties of the investigated polymer solutions as well as on the salting-out effect of PEGDMEs produced by ammonium phosphate salts has been studied.     

Hydrothermal Synthesis and Structure of Two New Mo(V)-Oxide Phosphates

Two new members of Mo(V) phosphates were synthesized by hydrothermal methods. (enH₂)(enH)[NaMo₁₂O₂₄(OH)₆(HPO₄)₂(H₂PO₄)₆]·(en)₄·20H₂O(1)(en=H₂ NCH₂CH₂NH₂)[HAD-H₂]₂[HAD-H]₂[Zn₃Mo₁₂O₂₄(OH)₆(PO₄)₂(HPO₄)₆]·6H₂O (2) (HAD=H₂N(CH₂)₆NH₂). Compound 1 crystallized in the space group P2(1)/n, a=15.93120(10) Å, b=15.8946(2) Å, c=17.0665(2) Å, V=4316.02(8), =92.9060(10)°, Z=2. Compound 2 crystallized in the space group P(–1) with a=12.3726(3) Å, b=14.1948(3) Å, c=14.2310(4) Å, =72.7100(10), =65.0230(10), =69.5600(10)°, Z=2089.70(9) ų, and Z=1. The structure of 1 consists of sandwich-shaped cluster anion [Na{Mo^V ₆O₁₂(OH)₃(HPO₄)(H₂PO₄)₃}₂]^3– ({Na(Mo ^V ₆ ) ₂ }) held together via intermolecular hydrogen-bonding contacts. For the compound 2, the sandwich-shaped clusters Zn[Mo₆O₁₂(OH)₃(PO₄)(HPO₄)₃]₂ ({Zn(Mo ^V ₆ ) ₂} are linked by tetrahedrally-coordinated zinc into layers. Organic cations ([H₃N(CH₂)₆NH₃]²⁺ and [H₃N(CH₂)₆NH₂]⁺) are filled in the spaces between lamellas. The layers are held together by a hydrogen-bonded network, which involves the terminal phosphate P-OH groups, as well as organic cations and several waters of solvation.     

Structural characterizations and magnetic properties of three new reduced molybdenum phosphates

Three new molybdophosphates, [Co(dien)₂]·(H₃dien)₆·{[CoMo₁₂O₂₄(OH)₆(HPO₄)₂(PO₄)₆][Co(Hdien)]₂[CoMo₁₂O₂₄(OH)₆(PO₄)₈]}·(dien)·4H₃O·5H₂O (1), (H₃dien)₄[MMo₁₂O₂₄(OH)₆(HPO₄)₄(PO₄)₄]·10H₂O [M=Co for (2), Ni for (3); dien=diethylenetriamine], have been synthesized by employing hydrothermal method and characterized by single crystal X-ray diffraction. Compound 1 is built up of Co[P₄Mo₆]₂ units as the structural motif covalently linked by [Co(Hdien)] complex subunits to yield an unusual 1-D chain. Compounds 2 and 3 are isomorphic and both display covalent discrete M[P₄Mo₆]₂ cluster structures which are linked by the hydrogen bonds to form 3-D supramolecular networks. Both 1 and 2 display antiferromagnetic interaction and these three compounds all exhibit intensive photoluminescence.     

Hydrothermal synthesis and characterization of a new layered gallophosphate JGP-L1 with a Ga/P ratio of non-unity

A new compound, Ga₆(OH)₄(HPO₄)₂(PO₄)₅·C₈H₂₈N₅·3H₂O (denoted JGP-L1), with a gallophosphate layer and a Ga/P ratio of 6/7 has been synthesized hydrothermally by using tetraethylenepentamine as template. It is characterized by powder X-ray diffraction (XRD), elemental analysis, inductively coupled plasma, and TGA analysis and structurally determined by single-crystal XRD analysis. JGP-L1 crystallizes in the orthorhombic, space group Pna2₁ (no. 33), with a=16.422(3), b=11.898(2), c=18.730(4) Å, V=3659.6(13) Å³ and Z=4. The structure of JGP-L1 is built up by alternating of Ga(OH)₂O₄ octahedra, Ga(OH)O₄ trigonal bipyramids and PO₄ (or HPO₄) tetrahedra to form inorganic sheets. It is noteworthy that JGP-L1 was synthesized with extremely low reactant concentration, where the reaction mixture exhibits a H₂O:Ga₂O₃ molar ratio of 2220:1.     

ZrONO3)2-H3PO4-KF(HF)-H2O system at molar ratios of PO 43? /Zr = 0.5?1.6 as the basis for phase formation

The system ZrO(NO₃)₂-H₃PO₄-KF(HF)-H₂O was studied at ∼20°C along sections at molar ratios of PO₄³⁻ = 0.5, 1.0, and 1.6; KF: Zr = 1−5; and HF: Zr = 2−6. Phases in precipitates were identified by X-ray powder diffraction; IR spectroscopy; and crystal-optical, chemical, X-ray fluorescence and thermal analyses. The following crystalline phases were isolated: potassium fluorozirconates K₃ZrF₇, K₂ZrF₆, δ-KZrF₅, and KZrF₅ · H₂O; zirconium hydrophosphate Zr(HPO₄)₂ · 0.5H₂O; and potassium fluorophosphate zirconate K₃Zr₃F₃(HPO₄)₃(PO₄)₂. The following amorphous basic oxo(hydroxo)fluorohydrophosphate nitrates were isolated: K₄Zr₄O_2.5F₈(HPO₄)₂(NO₃)₃ · 6H₂O, K₂Zr₃O₃F₂(HPO₄)₂(NO₃)₂ · H₂O, and KZr₃O_1.5F₃(HPO₄)₂(NO₃)₃ · 2H₂O. Fields of solid phases were constructed, and the roles of anions and cations in the phase formation were considered.     

Standard enthalpy of formation of disodium hydrogen phosphate hexahydrate and sodium diphosphate

Commercial disodium hydrogen phosphate dodecahydrate (Na₂HPO₄·12H₂O) was used as a precursor for synthesizing disodium hydrogen phosphate hexahydrate (Na₂HPO₄·6H₂O) and sodium diphosphate (Na₄P₂O₇). The purity of the synthesized products was checked up by IR spectroscopy and X-ray diffraction. The heat of dissolution of these compounds, in acid solutions of several concentrations (w/w) of H₃PO₄ was measured in a C-80 SETARAM calorimeter. Many dilution and mixing processes were also realized in the calorimeter in order to get the standard enthalpy of formation of these products. The values obtained for the enthalpies of formation are: (?3210.5) and (?3516.5) kJ · mol^?1 for sodium diphosphate (Na₄P₂O₇) and disodium hydrogen phosphate hexahydrate (Na₂HPO₄·6H₂O), respectively.     

Microwave assisted low temperature synthesis of sodium zirconium phosphate (NaZr<Subscript>2</Subscript>P<Subscript>3</Subscript>O<Subscript>12</Subscript>)

Sodium zirconium phosphate [NaZr₂P₃O₁₂], a potential ceramic matrix for fixation of high level nuclear waste, was synthesized by heating the mixture of sodium carbonate [Na₂CO₃], zirconyl nitrate hydrate [ZrO(NO₃)₂·5H₂O] and ammonium dihydrogen phosphate [NH₄H₂PO₄] in air, in a resistance heated furnace and a microwave heating system respectively in the temperature range 450 to 650°C. The mixture heated for 1 h in a resistance furnace at 450°C yielded a poorly crystalline NaZr₂P₃O₁₂ [NZP]. Increasing the temperature to 650°C produced a highly crystalline product. The same mixture heated in a microwave oven at 450°C for 1 h however, yielded the most crystalline NZP.In an alternate method, the mixture of sodium dihydrogen phosphate (NaH₂PO₄), zirconium dioxide (ZrO₂) and diammonium hydrogen phosphate [(NH₄)₂HPO₄] heated in resistance furnace at 650°C for the same period did not react in air. It also did not yield the pure product at 450°C when heated in microwave assembly for 1 h.The authors thank the Board of Research in Nuclear Sciences (BRNS) of the Department of Atomic Energy (DAE) for the financial support for this work under the project No. 2000/37/19/BRNS/1959 dtd09-02-02.     

Magnetic and catalytic properties of the 2D copper(II) functionalized VPO hybrid system [{Cu(bpy)}2(VO)3(PO4)2(HPO4)2]·2H2O

The hybrid 2D compound [{Cu(bpy)}₂(VO)₃(PO₄)₂(HPO₄)₂]·2H₂O (1), has been investigated due to its interesting magnetic and catalytic properties. Compound (1) acts as an efficient catalyst in the epoxidation of cyclohexene and styrene. The chemoselectivity towards the epoxidation of cyclohexene is notoriously higher than the one observed towards styrene. The bulk antiferromagnetic behaviour of [{Cu(bpy)}₂(VO)₃(PO₄)₂(HPO₄)₂]·2H₂O (1) can be well described with a pentanuclear model, using five J values. Both antiferromagnetic and ferromagnetic interactions mediated by phosphate bridges are found to be present in this hybrid copper(II)–vanadium(IV) material.     

Structure of trihydrated rare-earth acid diphosphates LnHP2O7·3H2O (Ln=La, Er)

In trihydrated lanthanum acid-diphosphates LnHP₂O₇·3H₂O, prepared from acid LnCl₃ and Na₄P₂O₇ solutions (pH=1), two crystal forms were obtained. Layered structures of two representative members of this family have been determined by single-crystal X-ray diffraction (XRD) technique. In the case of orthorhombic LaHP₂O₇·3H₂O (type I), lanthanum cations are ninefold coordinated and diphosphate groups adopt a staggered (alternated) configuration. In the case of triclinic ErHP₂O₇·3H₂O (type II), erbium cations are eightfold coordinated and diphosphate groups adopt an eclipsed configuration. In agreement with Infrared (IR) spectroscopic data, a bended configuration for diphosphate groups has been deduced. In both structures, one-dimensional chains of edge-sharing rare-earth polyhedra are linked together by diphosphate groups to form the phosphate layers. In both diphosphates, PO₄ and HPO₄ environments have been identified by ³¹P MAS-NMR technique. In the two compounds, OH groups of HPO₄ tetrahedra point out of diphosphate planes interacting with adjacent layers. In La-diphosphate, the interaction between HPO₄ groups and water molecules of adjacent layers is favored; however, in Er-diphosphate, the interaction between phosphate acid groups of contiguous layers is produced. Based on structural information deduced, differences detected in IR and NMR spectra of two disphosphates are discussed.     

Solubility and Phase Behavior of Cr(III) Oxides in Alkaline Media at Elevated Temperatures

A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of Cr₂O₃ and FeCr₂O₄ in alkaline sodium phosphate, sodium hydroxide, and ammonium hydroxide solutions between 21 and 288°C. Baseline Cr(III) ion solubilities were found to be on the order of 0.1 nmolal, which were enhanced by the formation of anionic hydroxo and phosphato complexes. At temperatures below 51°C, the activity of Cr(III) ions in aqueous solution is controlled by a Cr(OH)₃·3H₂O solid phase rather than Cr₂O₃; above 51°C the saturating solid phase is -CrOOH. Measured chromium solubilities were interpreted via a Cr(III) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria were obtained from least-squares analyses of the data. The existence of four new Cr(III) ion complexes is reported: Cr(OH)₃(H₂PO₄)^–, Cr(OH)₃(HPO₄)^2–, Cr(OH)₃(PO₄)^3–, and Cr(OH)₄(HPO₄)-(H₂PO₄)^4–. The last species is the dominant Cr(III) ion complex in concentrated, alkaline phosphate solutions at elevated temperatures.     

Synthesis and characterization of uranium (IV) phosphate-hydrogenphosphate hydrate and cerium (IV) phosphate-hydrogenphosphate hydrate

A new uranium (IV) phosphate of proposed formula U₂(PO₄)₂HPO₄·H₂O, i.e. uranium phosphate-hydrogenphosphate hydrate (UPHPH), was synthesized in autoclave and/or in polytetrafluoroethylene closed containers at 150 °C by three ways: from uranium (IV) hydrochloric solution and phosphoric acid, from uranium dioxide and phosphoric acid and by transformation of the uranium hydrogenphosphate hydrate U(HPO₄)₂·nH₂O. The new product appears similar to the previously published thorium phosphate-hydrogenphosphate hydrate Th₂(PO₄)₂HPO₄·H₂O (TPHPH). From preliminary studies, it was found that UPHPH crystallizes in monoclinic system (, , , β=91.67(3)° and ). Heated under inert atmosphere, this compound is decomposed above 400 °C into uranium phosphate-triphosphate U₂(PO₄)P₃O₁₀, uranium diphosphate α-UP₂O₇ and diuranium oxide phosphate U₂O(PO₄)₂.Crystallized cerium (IV) phosphate-hydrogenphosphate hydrate Ce₂(PO₄)₂HPO₄·H₂O (CePHPH) was also synthesized from (NH₄)₂Ce(NO₃)₆ and phosphoric acid solutions by the same method (monoclinic system: , , , β=91.98(1)° and ). When heating above 600 °C, cerium (IV) is reduced into Ce (III) and forms a mixture of CePO₄ (monazite structure) and CeP₃O₉.     

Comparison of one-, two-, and three-dimensional iron phosphates containing ethylenediamine

A new two-dimensional (2d) iron phosphate, (C₂N₂H₁₀)Fe₂O(PO₄)₂, has been synthesized under hydrothermal conditions in the system of FeCl₃-H₃PO₄-C₂N₂H₈-H₂O. The crystal data is: space group P2₁/c, a=10.670(1) Å, b=10.897(1) Å, c=9.918(1) Å, β=105.632(1)°, Z=4. The layered structure consists of double sheet layers, of composition Fe₂O(PO₄)₂, built from FeO₅ trigonal bipyramids and PO₄ tetrahedra. The amine holds the layers together via H-bonding. The study of the magnetic properties reveals two magnetic transitions at 160 and 30 K with spin-glass-like behavior below 160 K. By varying the hydrothermal conditions, three other iron phosphates were synthesized: the one-dimensional (1d) (C₂N₂H₁₀)Fe(HPO₄)₂(OH)·H₂O, the 2d (C₂N₂H₁₀)Fe₂(PO₄)₂(OH)₂, and the three-dimensional (3d) (C₂N₂H₁₀)₂Fe₄O(PO₄)₄·H₂O. The 1d compound can be used as the starting reagent in the synthesis of both the 2d compound and the 3d lipscombite Fe₃(PO₄)₂(OH)₂ due to the similar building blocks in their structures. In the 3d phosphate (C₂N₂H₁₀)₂Fe₄O(PO₄)₄·H₂O, manganese can substitute for half of the iron atoms. Magnetic study shows ordering transitions at about 30 K, however, manganese substitution depresses the magnetic ordering temperature.     

Kinetics of H+/Na+ Ion Exchange on H1 ± xZr2 − xMx(PO4)3 (M = Y or Nb) NASICON Materials

The thermodynamic parameters of ion exchange have been estimated for HZr₂(PO₄)₃ · H₂O and the products of its aliovalent doping. Ion exchange occurs via formation of the (H₃O_{1 ? x}Na_x)Zr₂(PO₄)₃ solid-solution series. As in the case of ion exchange on layered zirconium phosphate (Zr(HPO₄)₂ · H₂O), the interdiffusion coefficient and the major interfacial defect generation processes are considerably affected by the contact-solution pH.     

IR and Raman spectra of two layered aluminium phosphates Co(en)3Al3P4O16 · 3H2O and [NH4]3[Co(NH3)6]3[Al2(PO4)4]2 · 2H2O

The FT IR and FT Raman spectra of Co(en)₃Al₃P₄O₁₆ · 3H₂O (compound I) and [NH₄]₃[Co(NH₃)₆]₃[Al₂(PO₄)₄]₂ · 2H₂O (compound II) are recorded and analysed based on the vibrations of Co(en)₃³⁺, Co(NH₃)₆³⁺, NH₄⁺, Al---O---P, PO₃, PO₂ and H₂O. The observed splitting of bands indicate that the site symmetry and correlation field effects are appreciable in both the compounds. In compound I, the overtone of CH₂ deformation Fermi resonates with its symmetric stretching vibration. The NH₄ ion in compound II is not free to rotate in the crystalline lattice. Hydrogen bonding of different groups is also discussed.     

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).