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.     

Structural investigations on zirconium phosphate-phosphite and on itsn-butylamine intercalate

Zirconium phosphate-phosphite have various structure belonging to the drying heat of the sample. While sample dried above sat. NaCl solution had interlayer distance of 1.30 nm (result fromd ₁=0.74 nm andd ₂=0.56 nm for phosphite layer), the sample dried under IR lamp on air having interlayer spacingd=0.74 nm charactderistic for -Zr(HPO₄)₂·H₂O containing little amount of phosphite groups. The composition of the first sample can be characterized by chemical formula, as Zr(HPO₄)_0.7(HPO₃)_1.3· ·0.5H₂O. The X-ray powder diffraction data ofn-butylamine intercalate suggest that in the process take place only the phosphate region of zirconium phosphate-phosphite (ZrPP).     

Quantitative extraction of uranium(VI) in aqueous solutions with n-alkylamine intercalates of γ-titanium phosphate

The intercalation compounds Ti(C₃H₇NH₂)(HPO₄)₂·H₂O (18.4 Å) (-TiP/n-Pr) and Ti(C₄H₉NH₂)(HPO₄)₂·H₂O (20.5 Å) (-TiP/n-Bu) have been prepared using -titanium phosphate, Ti(HPO₄)₂·2H₂O (11.6 Å), as precursor. The retention of UO ₂ ²⁺ , in aqueous solutions by -TiP is very low being only a superficial adsorption phenomenon. When the intercalated materials are used, the retention is quantitative until 95% of the cation exchange capacity in the -TiP/n-Pr case (c.e.c.=6.30 mequiv./g), and over 80% for the -TiP/n-Bu compound (c.e.c.=6.04 mequiv./g).     

Solubility behavior of titanium(IV) oxide in alkaline media at elevated temperatures

A platinum-lined, flowing autoclave facility was used to investigate the solubility behavior of titanium dioxide (TiO₂) in aqueous sodium phosphate, sodium hydroxide and ammonium hydroxide solutions between 17 and 288°. Baseline Ti(IV) solubilities were found to be on the order of one nanomolal, which were enhanced by the formation of anionic hydroxo- and phosphato-complexes. The measured solubility behavior was examined via a titanium(IV) ion hydrolysis/complexing reaction equilibria were obtained from a least squares analysis of the data. The existence of three new Ti(IV) ion complexes is reported for the first time: Ti(OH)₄(HPO₄)^2–, Ti(OH)₅(H₂PO₄)^2– and Ti(OH)₅(HPO₄)^3–. The triply-charged anionic complex was the dominant Ti(IV) species in concentrated, alkaline phosphate solutions at elevated temperatures. This complex is expected to exhibit C.N.=4 (i.e., Ti(OH)₂OPO ₄ ^3– ). A summary of thermochemical properties for species in the systems TiO₂-H₂O and TiO₂-P₂O₅-H₂O is also provided.     

Mixed insoluble acidic salts of tetravalent metals V. Effect of gamma radiation and drying temperature on granular mixed zirconium-titanium phosphates

Solid ZrOCl₂·8H₂O was added in a slow stream to a solution of phosphoric acid or to a solution of TiCl₄ in phosphoric acid to obtain granules of amorphous Zr(HPO₄)₂·nH₂O or Zr_xTi(_1–x) (HPO₄)₂·nH₂O(where x=0.95–0.80). Half of each product had been soaked in ethanol to produce alcohol solvated materials. It was found that the particle size of the resulting materials is very similar to that of ZrOCl₂·8H₂O, in such a way that it may be controlled indirectly. These materials are suitable for ion-exchange column operations. The relatively high gamma radiation doses of⁶⁰Co source did not alter its exchange properties. pH-titrations were performed by an automatic titrimeter and the exchange capacities of alkali metal ions were determined by isotopic tracer technique. Effect of drying temperature on the ion exchange properties of Na⁺, K⁺ and Cs⁺ on the granular materials have been studied. Other characterizations were made by usual chemical analysis and thermography.     

Synthesis and structural characterisation using Rietveld and pair distribution function analysis of layered mixed titanium-zirconium phosphates

Crystalline metal (IV) phosphates with variable zirconium-to-titanium molar ratios of general formula (Ti_1−xZr_x)(HPO₄)₂·H₂O have been prepared by precipitation of soluble salts of the metals with phosphoric acid and heating the amorphous solids in 12 M H₃PO₄ in an autoclave. The new materials are structurally characterised by Rietveld analysis of synchrotron X-ray powder diffraction data and pair distribution function (PDF) analysis of high energy synchrotron X-ray total scattering data. A broad range of zirconium-titanium phosphate solid solutions were formed showing isomorphous substitution of titanium by zirconium in the α-titanium phosphate lattice and vice versa for titanium substitution into the α-zirconium phosphate lattice. In both cases the solubility is partial with the coexistence of two substituted phases observed in samples with nominal compositions between the solubility limits.     

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.     

Zinc(II) oxide solubility and phase behavior in aqueous sodium phosphate solutions at elevated temperatures

A platinum-lined, flowing autoclave facility is used to investigate the solubility/phase behavior of zinc(II) oxide in aqueous sodium phosphate solutions at temperatures between 17 and 287°C. ZnO solubilities are observed to increase continuously with temperature and phosphate concentration. At higher phosphate concentrations, a solid phase transformation to NaZnPO₄ is observed. NaZnPO₄ solubilities are retrograde with temperature. The measured solubility behavior is examined via a Zn(II) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria are obtained from a least-squares analysis of the data. The existence of two new zinc(II) ion complexes, Zn(OH)₂(HPO₄)^2– and Zn(OH)₃(H₂PO₄)^2–, is reported for the first time. A summary of thermochemical properties for species in the systems ZnO–H₂O and ZnO–Na₂O–P₂O₅–H₂O is also provided.     

Vibrational spectra and H-bondings in anhydrous and monohydrate α-Zr phosphates

A new FTIR and FT-Raman investigation on α-zirconium phosphate (Zr(HPO₄)₂·H₂O) and its anhydrous form has been performed in order to obtain an affordable assignment of their vibrational spectra as well as to highlight the hydrogen bonding structure formed by the P-OH groups and the intercalated water molecules. To this end the spectral changes induced by both temperature and isotopic exchange were observed on several high-purity grade samples of different morphology especially prepared and well characterized by SEM, RX, DSC and TGA. In particular, it is also presented as a detailed discussion of the results obtained by FTIR-PAS for different sample morphology. The observed spectra have been analyzed and interpreted according to the α-Zr(HPO₄)₂·H₂O crystal structure and H-bond geometry. The obtained results allowed to clarify the mechanism of the α-Zr(HPO₄)₂·H₂O→α-Zr(HPO₄)₂ dehydration process as well as the H-bonding changes involved in the high temperature phase transition of anhydrous α-Zr(HPO₄)₂.     

Synthesis and structure of a new zirconium phosphate with double-stranded chains

The zirconium phosphate [Zr(HPO₄)(PO₄)F₂] · 1.5H₂en was prepared, and its structure was determined by X-ray diffraction analysis.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1897–1901, November, 1994.The work was carried out with financial support from SERC (UK) and the National Foundation of Natural Sciences (China).     

Intercalation of phenylethylamines intoα-zirconium phosphate and characterization of intercalates

The intercalation of phenylethylamines into-zirconium phosphate has been investigated by the pH titration method.dl-1-Phenylethylamine (dl-PEA) is taken up in two stages. New phases were obtained: Zr(HPO₄)₂(dl-PEA) · H2O in the first, and Zr(HPO₄)₂(dl-PEA)_/43· H₂O in the second stage. 2-Phenylethylamine (2-PEA) also is loaded in two stages, but the first end point is not observed clearly. A new phase, Zr(HPO₄)₂(2-PEA)₂ · H₂O has been formed at the second stage. The new phases have been characterized by elemental analysis, X-ray diffractometry, thermal analysis and IR spectroscopy.     

From thorium phosphate hydrogenphosphate hydrate to β-thorium phosphate diphosphate: Structural evolution to a radwaste storage ceramic

β-Thorium phosphate diphosphate (β-TPD), considered as a very promising radwaste storage material, was obtained from thorium phosphate hydrogenphosphate hydrate (TPHPH) precursor through dehydration and hydrogen phosphate condensation. The structures of TPHPH, intermediate α-thorium phosphate diphosphate (α-TPD) and its hydrate (α-TPDH) have been resolved ab initio by Rietveld analysis of their synchrotron diffraction patterns. All were found orthorhombic (space group Cmcm) and similarly composed of [ThPO₄]₄⁴⁺ slabs alternating with disordered layers hosting either [HPO₄·H₂O]₂⁴⁻ (TPHPH), [P₂O₇·2H₂O]⁴⁻ (α-TPDH), or [P₂O₇]⁴⁻ (α-TPD), unlike the 3D structure of β-TPD. The diphosphate groups of α-TPD and α-TPDH are strongly bent. The irreversible transition to the final β-TPD consists in a shearing of the slabs and a reduction of the interslabs cavities that explains the stability of this high-temperature form.     

A Study of Physicochemical Processes in Film-forming Ethanol Solutions of Zirconium and Cobalt Salts and Properties of Thin Films Obtained on Their Base

The main physicochemical processes that occur in film-forming solutions based on zirconium oxochloride ZrOCl₂ · 8H₂O, cobalt salts CoCl₂ · 6H₂O and Co(NO₃)₂ · 6H₂O, and ethanol were studied. The intermolecular interaction in film-forming solutions was analyzed qualitatively and quantitatively.     

Coupled diffusion produced by hydrolysis of aqueous potassium phosphate

Conductimetric and diaphragm cell techniques have been used to measure diffusion of aqueous potassium phosphate solutions at 25°C from 0.01 to 0.10 mol-dm^–3 (M). A significant portion of the aqueous K₃PO₄ component diffuses as equimolar amounts of potassium hydrogen phosphate and potassium hydroxide produced by hydrolysis: K₃PO₄+H₂O=K₂HPO₄+KOH. Because OH^– diffuses more rapidly than HPO ₄ ^2– , the total flow of KOH exceeds the flow of K₂HPO₄. The extra flow of KOH constitutes coupled transport of a second solute component. Ternary diffusion coefficients that describe interacting flows of K₃PO₄ and KOH components are reported. At low concentrations where phosphate is strongly hydrolyzed, the molar flux of the KOH component produced by diffusion of K₃PO₄ is six times larger than the flux of the K₃PO₄ component. Binary diffusion coefficients for aqueous K₂HPO₄ solutions are also reported. It is shown that ternary transport coefficients for K₃PO₄ solutions can be estimated from the properties of binary solutions of K₂HPO₄ and KOH.     

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.     

Speciation of water-soluble titanium citrate: Synthesis,structural, spectroscopic properties and biological relevance

Titanium(IV) citrate complexes with different anions Na₃[Ti(H₂cit)₂(Hcit)] · 9H₂O (1), K₄[Ti(H₂cit)(Hcit)₂] · 4H₂O (2), K₅[Ti(Hcit)₃] · 4H₂O (3) and Na₇[TiH(cit)₃] · 18H₂O (4) (H₄cit = citric acid) were isolated in pure forms from the solutions of titanate and citrate at various pH values. X-ray structural analyses revealed the presence of a monomeric tricitrato titanium unit in the four complexes. Each Ti(IV) ion is coordinated octahedrally by the three citrate ligands in different protonated forms. The citrate ligand chelates bidentately to the titanium ion through its negatively charged α-alkoxy and α-carboxy groups. This is consistent with the large downfield ¹³C NMR shifts for the carbon atoms bearing the α-alkoxy and α-carboxy groups. The very strong hydrogen-bonds existing in the protonated and deprotonated β-carboxy groups may be the key factor for the stabilization of the titanium citrate complexes. When the pH value is lower than 7.0, ¹³C NMR spectra of 1:3 Ti:citrate solutions are similar to those of the titanium citrate complexes isolated at the corresponding pH values. The dissociation of free citrate increases with the rise of pH value. However, ¹³C NMR spectra of 1:3 Ti:citrate solutions indicate that there may exist different citrate titanium species when the pH value is higher than 7.0.     

The hydrogenphosphate complex of (1,5-cyclooctadiene)iridium(I), {[Bu4N][(1,5-COD)Ir · HPO4]}n: synthesis, spectroscopic characterization, and ES-MS of a new, preferred precursor to HPO4 and Bu4N stabilized Ir(0)n nanoclusters

The synthesis and characterization of a previously unknown, rare organometallic-phosphate complex, {[Bu₄N][(1,5-COD)Ir · HPO₄]}_n (1), is described. Characterization of 1 was accomplished by elemental analysis, electrospray mass spectrometry (ES-MS), and ¹H and ¹³C NMR which established the symmetry of the product as at least C₂ or C_s. The ES-MS reveals an interesting, Ir(I) to Ir(III) oxidative process with intense peaks displaying the ¹⁹¹Ir/¹⁹³Ir isotopic distribution patterns expected for the fragments [(1,5-COD)Ir^III(HPO₄)₂]⁻, [(C₈H₁₁)₂(Ir^III)₂(PO₄)(HPO₄)(H₂O)]⁻, and [(C₈H₁₁)₂(Ir^III)₂(PO₄)(HPO₄)(H₂O)₂]⁻. These fragments, in turn, provide evidence for a structure with two HPO₄²⁻ groups attached to a single Ir, for example ring structures (of at least such C₂ or C_s symmetry) such as {[Bu₄N][(1,5-COD)Ir · HPO₄]}₂. Complex 1 is significant since it is known to be the preferred, compositionally precise precursor to the prototype example of a recently discovered class of novel, HPO₄²⁻ and Bu₄N⁺ stabilized nanoclusters, (Bu₄N)_2n²ⁿ⁺[Ir(0)_n · (HPO₄)_n]²ⁿ⁻. Such nanoclusters are being extended, via their analogous hydrogenphosphate-organometallic precursors (1,5-COD)M^{+ or 2+}/HPO₄²⁻ (M=Rh(I), Ru(II), Pt(II)) to their corresponding, catalytically active [M(0)_n · (HPO₄)_n]²ⁿ⁻ nanoclusters.     

Investigations of crystalline structure of gamma-zirconium phosphate

The -crystalline form zirconium phosphate was investigated. For its lattice parameters was found:a=0.538 nm,b=0.664 nm,c=2.459 nm, =94.2° and basal spacing (d)=1.22 nm. It was determined by IR spectrophotometric method that the phosphate is present in groups of H₂PO ₄ ^– and PO ₄ ^3– of equal quantity. Two moles of crystalline water per formula unit were found where the moles are bound differently. The compound can be characterized by the following chemical formula: Zr(HPO₄)(PO₄)·2H₂O.     

Synthesis and structure of [C6H14N2][(UO2)4(HPO4)2(PO4)2(H2O)]·H2O: An expanded open-framework amine-bearing uranyl phosphate

A new open-framework compound, [C₆H₁₄N₂][(UO₂)₄(HPO₄)₂(PO₄)₂(H₂O)]·H₂O, (DUP-1) has been synthesized under mild hydrothermal conditions. The resulting structure consists of diprotonated DABCOH₂²⁺ (C₆H₁₄N₂²⁺) cations and occluded water molecules occupying the channels of a complex uranyl phosphate three-dimensional framework. The anionic lattice contains uranophane-like sheets connected by hydrated pentagonal bipyramidal UO₇ units. [C₆H₁₄N₂][(UO₂)₄(HPO₄)₂(PO₄)₂(H₂O)]·H₂O possesses five crystallographically unique U centers. U(VI) is present here in both six- and seven-coordinate environments. The DABCOH₂²⁺ cations are held within the channels by hydrogen bonds to both two uranyl oxygen atoms and a μ₂-O atom. Crystallographic data (193 K, Mo Kα, λ=0.71073 Å): DUP-1, monoclinic, P2₁/n, a=7.017(1) Å, b=21.966(4) Å, c=17.619(3) Å, β=90.198(3)°, Z=4, R(F)=4.76% for 382 parameters with 6615 reflections with I>2σ(I).     

Hydrothermal synthesis and characterization of layered vanadium phosphite: [HN(C2H4)3N][(VO)2(HPO3)2(OH)(H2O)]·H2O

A novel compound, [HN(C₂H₄)₃N][(VO)₂(HPO₃)₂(OH)(H₂O)]·H₂O, was hydrothermally synthesized and characterized by single crystal X-ray diffraction. This compound crystallizes in the monoclinic system with the space group C2/c and cell parameters a=11.0753(3) Å, b=17.8265(6) Å, c=16.5229(5) Å, and β=92.362(2)°. The structure of the compound consists of vanadium phosphite layers which are built up from the infinite one-dimensional chains of [(VO)(H₂O)(HPO₃)₂]²⁻ of octahedral VO₅(H₂O) and pseudo pyramidal [HPO₃], and bridging binuclear fragments of [VO(OH)]₂. Thermogravimetric analysis and magnetic susceptibility data for this compound are given.