Γ-zirconium Phosphate Research Articles

Ion-exchange Properties of γ-Zirconium Phosphate.

γ-Zirconium phosphate (γ-ZrP) has potential as a very useful inorganic ion-exchanger due to its stability under thermal and acidic conditions. We recently reported its facile synthesis using a modified solventless method, which could make the exploitation of its ion-exchange properties for cleanup of radioactive materials and extraction of valuable ions feasible. The adsorption isotherms of Rb+ and Sr2+ over γ-ZrP are described well with the Langmuir model, with maximum adsorption capacity of 1.52 and 1.31 mmol/g, respectively. Both ions adsorb on γ-ZrP following pseudo-second order kinetics with a much faster uptake of Rb+ than of Sr2+ . γ-Zirconium phosphate shows very high affinity for Rb+ , allowing its enrichment from low-concentration solutions. Notably, Rb+ is selectively removed from complex solutions containing large amounts of Na+ , Mg2+ , Ca2+ , or transition metals such as Cu2+ , Ni2+ , Fe2+ , Fe3+ , Co2+ and Zn2+ . The used sorbent can be fully regenerated by nitric acid, enabling the recovery of Rb+ .

Adsorption of gaseous aromatic compounds by linear quaternary ammonium-modified γ-zirconium phosphate

In this work, the intercalation of alkyl trimethylammonium ion (CnN+) and dialkyl dimethylammonium ion (2CnN+) were attempted for α‑zirconium phosphate (α-ZrP) and γ-ZrP. And then a pure intercalation compounds were obtained only for γ-ZrP. It was expected that the intercalation of linear quaternary ammonium ion would produce not only a hydrophobic environment in the interlayer space but also form an appropriate void for the adsorption of hydrophobic air pollutants. The basal spacing of 2CnN+-intercalated γ-ZrP was greater than that of CnN+-intercalated γ-ZrP because CnN+ was arranged in a mono-molecular structure in the interlayer space contrary to the bi-molecular structure of 2CnN+. Furthermore, the alkyl chain in the interlayer space of γ-ZrP was in a gauche form for CnN+, for a smaller carbon number (n), and changed to a trans structure for a larger n. γ-ZrP with a modified interlayer space could adsorb gaseous aromatic hydrocarbons contrary to the nonmodified γ-ZrP. Maximum adsorption was attained for C18N+-intercalated γ-ZrP with a mono-molecular structure and trans structure alkyl chain, although the basal spacing and uptake of alkyl ammonium reached a maximum for 2C18N+-intercalated γ-ZrP. Hence, not only the basal spacing and carbon number but also the void space in the interlayer region affected adsorption. It was interesting to note that the conformation of the long alkyl chain was reversibly changed through adsorption and desorption.

Circumstances of La, Eu, Dy, and Yb Cations Intercalated via Ion Exchange in γ-Zirconium Phosphate.

Both α- and γ-zirconium phosphate were examined for use as ion exchangers for recovery of rare earth elements. Trivalent rare earth elements can be partially substituted for protons in the interlayer space, and γ-zirconium phosphate shows a much better ion exchange competency than α-zirconium phosphate. The exchanged cation of the rare earth elements might be related to different amounts of oxygen from P-OH and H2O, and these rare earth elements were thus positioned at a different separations from the zirconium phosphate layer. The radial structure function (RSF) curve from extended X-ray absorption fine structure data implied that the calibrated M-O distance and coordination number changed with the ionic radius. The calibrated M-O distances from RSF were 2.52, 2.42, 2.38, and 2.28 for La, Eu, Dy, and Yb, respectively. The coordination numbers of oxygen for Yb were approximately 7 and greater than 10 for La and Eu, respectively. These smaller coordination numbers for smaller cations may result from the strong interaction between the cations and the zirconium phosphate layer. The Debye-Waller factor also increased with an increase in the ionic radius. These factors show a strong relation to the coordination state of rare earth elements in the unit cell of the γ-zirconium phosphate and to the interaction strength.

Mechanochemistry-Based Synthesis of Highly Crystalline γ-Zirconium Phosphate for Selective Ion Exchange.

Highly crystalline γ-zirconium phosphate has been synthesized by a novel minimalistic approach and investigated as a selective ion exchanger for cesium, ammonium and potassium. In contrast to current solution-based preparations, the mechanochemistry-based synthesis provides easy access to γ-zirconium phosphate with short synthesis times and low crystallization temperature. The addition of NaF as a mineralizer increases the crystallinity of γ-zirconium phosphate, which forms micrometer-sized uniformly shaped rectangular platelets. The crystalline material has extremely high selectivity to cesium even in the presence of 1000- or 500-fold excess Na+ or Ca2+, respectively. The removal efficiency was >98% in the pH range of 2-5.5. As an ion exchanger for purification of dialysate, crystalline γ-zirconium phosphate shows higher uptake of ammonium and potassium ions than the amorphous gel compound currently used in sorbent cartridges. This sustainable protocol opens up opportunities for many practical applications of γ-zirconium phosphate.

Adsorption Behavior of Rare Earth Metal Cations in the Interlayer Space of γ-ZrP.

Adsorption competencies of rare earth metal cations in γ-zirconium phosphate were examined by ICP, synchrotron X-ray diffraction (SXRD), and ab initio simulation. The adsorption amounts are around 0.06-0.10 per zirconium phosphate. From the SXRD patterns of the adsorbed samples, the basal spacing estimated by c sin β increased linearly with an increasing ionic radius of rare earth metal cation, though a and b lattice constants show no change. These SXRD patterns can be classified into four groups that have different super lattices. The four superlattices have multiplicities of x131, x241, and x221 for the xabc axis, and the location of the rare earth metal cation in the original unit cell changes depending on the superlattice cell. In the x131 superlattice, Yb and Er occupied the site near the zirconium phosphate layer, though La and Ce in the x221 superlattice remained in the center position between the phosphate sheet. For the ab initio simulation of γ-ZrP with the typical rare earth metal cations (Tb, Eu, Dy, and La), the results of simulation show a similar tendency of the position estimated by SXRD refinements.

Baeyer–Villiger Oxidation of Aromatic Aldehydes Catalysed by Zirconium Phosphates Intercalated with Ionic Liquids

Crystalline α-zirconium phosphate intercalated with 1-ethyl-3-methylimidazolium chloride or 1-hexyl-3-methylimidazolium chloride, and crystalline γ-zirconium phosphate intercalated with 1-ethyl-3-methylimidazolium chloride were synthesised, characterized and evaluated as selective catalysts in the Baeyer–Villiger oxidation of p-methoxybenzaldehyde, o-methoxybenzaldehyde and 2,4,6-trimethylbenzaldehyde by hydrogen peroxide, in glacial acetic acid or without solvent. The best selectivities of p-methoxyphenol (100 %), o-methoxyphenol (95 %) and 2,4,6-trimethylphenol (55 %) were achieved without solvent and are explained by the properties and structure of each catalyst.

吡嗪-2-羧酸在γ-改性磷酸锆中的插层组装及发光性能

采用直接沉淀法制备了层状框架γ-磷酸锆(γ-ZrP)及改性磷酸锆(γ-DDZrP),通过插层化学法将吡嗪-2-羧酸生色团与改性磷酸锆进行杂化组装。X射线衍射结果显示,γ-DDZrP的层间距(3.70 nm)远远大于γ-ZrP(1.11 nm),这有利于吡嗪-2-羧酸生色团的插入。组装后层状框架的层间距由3.70 nm减小为3.33~3.29 nm。荧光光谱表明,最大发射峰位置发生了明显蓝移,由溶液中的373 nm蓝移至悬浮液的366 nm。研究发现,吡嗪-2-羧酸在水溶液中的荧光强度很低,但形成插层组装后,悬浮液的荧光强度有了很大程度的提高,当浓度为15μmol/L时,荧光强度增大了6倍。这说明γ-DDZrP能够改善吡嗪-2-羧酸的荧光性能,有利于其在分子识别和荧光探针等领域的应用。

Layered γ-Zirconium Phosphate Intercalated with Ru(bpy)3-Viologen Dyads as Unusual Materials for Dye-Sensitised Solar Cells: Improving Efficiency by Double Sensitisation

The intercalation materials prepared from the laminar salt γ-zirconium phosphate and various dyads formed from Ru(bpy)3 and viologens were tested as photoactive components in dye-sensitised solar cells. The efficiencies significantly increased, up to 0.2 %, when the materials were treated with the panchromatic N535 dye. A mechanism for this double sensitisation process is proposed, which should enable further improvement of these γ-ZrP-based materials as a reasonable alternative to the usual Ti-based dye-sensitised solar cells.

Synthesis and structural characterization of a new chiral porous hybrid organic–inorganic material based on γ-zirconium phosphates and l-(+)-phosphoserine

Abstract In the present work, a chiral layered derivative of γ-zirconium phosphate (γ-ZrP) containing l -(+)-phosphoserine (γ-ZrP-PS*) covalently attached to inorganic layers has been prepared by means of topotactic exchange reaction. This organic–inorganic derivative is characterized by X-ray diffractometry, Solid 13 C–NMR and FT-IR spectrophotometries and thermal analyses. A maximum level of topotactic replacement of 20% is achieved. Under both the acidic environment of the interlayer region of γ-ZrP and the acidic synthesis conditions, the hydrolysis of the ester bond of PS* is expected to take place to some extent. For this reason, it was impossible to exceed the recent percentage, which in turn reflects the relative moderate stability of the above mentioned bond under these conditions. In order to be more certain with regard to an expected further hydrolysis for this bond after separation, a sample of γ-ZrP-PS* was stored in a desiccator over a saturated solution of BaCl 2 (90% relative humidity) for three months, and then the sample re-analyzed once again. Surprisingly, the results show that the sample still keeps almost the same level of exchange (i.e., 20%). Second, it is revealed that the sample almost gives the same spectroscopic and thermal behavior. This could be attributed to the less acidic character of the partially exchanged inorganic layers of the sample in comparison with that of the precursor γ-ZrP. Therefore, the PS* molecules persist and stay there into the interlayer gallery without further hydrolysis.

Preparation of Some Useful Compounds of Zirconium from Bangladeshi Zircon

A number of useful zirconium compounds, such as hydrated zirconyl chloride, hydrated zirconium sulfate, zirconium dioxide, γ-zirconium ammonium phosphate, γ-zirconium phosphate, γ-zirconium phosphate phosphite, and γ-zirconium phosphate hypophosphite have been prepared from Bangladeshi zircon following the NaOH-fusion, acid (HCl and H2SO4)-leaching, precipitation, calcination/pyrolysis, condensation polymerization, ion exchange and the tap tactic reaction methods. The products have been characterized by chemical and thermogravimetric analyses in all cases, together with the XRD patterns and sodium exchange capacities in some cases.

Surfactant-assisted intercalation of crystal violet in layered γ-zirconium phosphate. Dye uptake from aqueous solutions

Batch intercalation experiments have carried out using γ-zirconium phosphate (γ-ZrP) and one of its cationic surfactant forms (γ-ZrP/SUR+) for removing crystal violet from aqueous solutions. The intercalation reactions have conducted along two different intervals of time (24 and 48 h). The intercalation process has followed up by X-ray diffractometry (XRD), UV–Visible and FT-IR spectrophotometries. Regarding γ-ZrP, XRD patterns show that obtained phases are impure, even after 48 h of the reaction time at a maximum dye loading of 18%. On the other side, γ-ZrP/SUR+ gives an impure phase after 24 h while a pure one (2.47 nm) is obtained after 48 h at a maximum dye loading of 19%. In both cases, the observed dye loading values are approximately equal to the one calculated by molecular modeling (ca. 20%). The used analysis approaches prove that dye uptake capacity is a function of the reaction time and inclination angle of the dye molecules inside the solid matrices, where the highest dye uptakes are observed with γ-ZrP and γ-ZrP/SUR+ after 48 h of the reaction time. This time (48 h) is long enough for the dye molecules to be sufficiently accumulated inside the interlayer regions, in such situation dye molecules are forced to stand up perpendicular to the inorganic layers. With respect to intercalation properties, the difference between γ-ZrP and γ-ZrP/SUR+ could be referred to the difference between their gallery heights (1.22 and 3.00 nm, respectively). The pre-intercalation of γ-ZrP with the surfactant molecules assists the inclusion and intercalation of the huge dye molecules into the interlayer region.

Intercalation of malachite green ([C6H5C(C6H4N(CH3)2)2]Cl) in layered γ-zirconium phosphate. Effect of cationic surfactants

The intercalation of malachite green (MG) in γ-zirconium phosphate (γ-ZrP) and one of its cationic surfactant forms (γ-ZrP/SUR+) has been investigated by the batch method and followed by X-ray diffractometry. X-Ray diffraction patterns showed that an impure phase (1.18 and 1.96 nm) was obtained with γ-ZrP while a pure one (2.47 nm) with γ-ZrP/SUR+ at a dye loading of 14% and 18%, respectively. In both cases, computer models and calculations based on the dye dimensions and the structure of the host showed that the maximum ion-exchange capacity is ca. 12–16%, which reflects the very high capacity by which γ-ZrP and γ-ZrP/SUR+ are characterized in the uptake of MG. The difference in the dye loading between the corresponding derivatives of pristine γ-ZrP and γ-ZrP/SUR+ is attributed to the difference in interlayer distances and the variable cross-section of the dye depending on its orientation and/or conformation within the interlayer region.

Layered γ-zirconium phosphate as novel semiconductor for dye sensitized solar cells: Improvement of photovoltaic efficiency by intercalation of a ruthenium complex-viologen dyad

The performance of photovoltaic cells using as semiconductor a film of layered γ-zirconium phosphate (γ-ZrP) containing Ru(bpy)3 and bipyridinium ions (viologens) as electron relays has been studied. The materials are easily prepared by intercalation of Ru complexes and the bipyridinium ions into preformed γ-ZrP nano sheets as colloidal solutions in the appropriate solvent and concentration. High loading of these two guests has been obtained as determined by elemental analysis. Inclusion of Ru(bpy)3 complex and bipyridinium in the intergallery spaces of γ-ZrP can be assessed by powder XRD monitoring of the d100 peak. A dyad was also synthesized where the Ru(bpy)3 and the 4,4′-bipyridinium were covalently connected by a four-methylene tether. The semiconducting behavior of layered γ-ZrP was supported by cyclic voltammetry (reversible reduction peak at −0.6 V), observation of photocurrent and Mott-Schottky measurements (flat band potential ∼−1.3 V vs.NHE) of thin films of this material supported on FTO electrode. Photovoltaic cells based on γ-ZrP containing Ru(bpy)3, exhibited similar VOC (∼0.5 V) and fill-factor values (0.3–0.4), differing in the current density and therefore in their efficiency. The maximum efficiency was obtained for the material containing high loading of the dyad (JSC = 0.383 mA/cm2, efficiency 0.1%). The photo response spectrum shows that the main limitation of these materials is still the inefficient photo sensitization of the semiconductor by the dye, probably due to the high negative flat band potential of γ-ZrP.

Creating libraries of porous materials derived from γ-zirconium phosphate: Pillaring with polyphenylethynyl diphosphonates

The synthesis of polyphenylethynyl diphosphonic acids was accomplished as well as their incorporation to γ-ZrP by topotactic phosphate/phosphonate partial exchange. The materials, characterized by solid-state NMR, XRD, elemental analysis and molecular modelling, bore truly pillared structures with a high degree of ultramicroporosity. The remaining surface phosphates from the partial phosphate/phosphonate replacement were further exchanged with methylphosphonate, phosphite or hypophosphate leading to a library of new materials that retained the pillared ultramicroporous structure. The porous solids displayed reasonable capacities to store hydrogen by physisorption.

Valorization of bio-glycerol: New catalytic materials for the synthesis of glycerol carbonate via glycerolysis of urea

The glycerolysis of urea plays an important role in the conversion of glycerol into glycerol carbonate because it is a phosgene-free process that uses easily available and low-cost raw materials that have a low toxicity. γ-Zirconium phosphate shows a good activity as catalyst as it affords 80% of conversion of glycerol under mild reaction conditions. The catalyst is easily recoverable and reusable in subsequent cycles of reaction. The kinetics of the reaction has been studied considering the full parameter space. The best temperature is 418 K, with 3 h of reaction using an equimolar amount of the two reagents (glycerol and urea) with a catalyst load of 0.6–1.5% w/w with respect to glycerol. The behaviour of the catalyst has been investigated by using the TPD technique. Multinuclear 1H and 13C NMR and FTIR have been used for the characterization of intermediates and by-product. The reaction mechanism is fully elucidated.

Kinetic study of decomposition for Co(II)- and Ni(II)-1,10-phenanthroline complexes intercalated in γ-zirconium phosphate

The thermal behaviour of the complexes formed in situ between the aromatic diamine 1,10-phenanthroline and the Co(II) and Ni(II) ions intercalated between the layers of γ-zirconium phosphate was studied by simultaneous TG/DSC techniques. The obtained materials show similar thermal behaviour: after a multi-step dehydration process they showed an oxidative decomposition in only one step. The kinetic study of the decomposition process was performed using both the model-free methods of Ozawa-Flynn-Wall and Kissinger. The former method provides a negligible dependence of activation energy on the degree of reaction α for both materials. Activation energies derived by the Kissinger method show a good agreement with the mean values derived by the Ozawa-Flynn-Wall method. The Arrhenius rate constants determined using also the pre-exponential factor values demonstrate that their thermal stability can be considered comparable, within the experimental uncertainty. Finally, a reliable method was applied to determine the model function from the best fit between the numerical dependence of the integral function g(α) vs. α and several theoretical model dependencies reported in literature for the most commonly used models. A Mampel first-order reaction model was selected to describe the thermal decomposition in both the materials studied.

Click-chemistry-based bis-triazolylpyridine diphosphonate ligand for the sensitized luminescence of lanthanides in the solid state within the layers of γ-zirconium phosphate

The synthesis by means of ‘click’ chemistry of a new ligand bearing the bis-triazolylpyridine motif and pendant phosphonate groups is described. The topotactic phosphate/phosphonate exchange of the ligand into gamma-zirconium phosphate led to an organic–inorganic-layered material which revealed an excellent matrix to achieve the efficient sensitization of emitting lanthanides.

Intercalation of tris-(2,2′-bipyridyl) ruthenium (II) in α- and γ-zirconium phosphate: synthesis, thermal behaviour and X-ray characterization

Intercalation compounds such as the ruthenium trisbipyridyl complex in inorganic layered ion-exchangers (α- and γ-zirconium phosphate) have been synthesized using the batch method. There is no loss of bipyridyl ligand from the metal ion during the exchange of the ruthenium trisbipyridyl complex in these host matrices. The materials obtained are thermally stable up to ~330 °C (γ-phase) or ~380 °C (α-phase). The complex decomposition occurs in one or more steps and at ~600 °C the complex decomposition is complete. The X-ray patterns of ruthenium materials show a new phase with an increase in the interlayer distance with respect to the initial phase. Microanalysis measurements confirm the fact that the ruthenium complex is not modified when exchanged and the complex decomposition depends on its position in the host matrices.

Preparation and characterization of ionic liquid intercalation compounds into layered zirconium phosphates

In this work, immobilizing a series of ionic liquids (ILs) 1-alkyl-3-methylimidazolium chloride [Cnmim]Cl (n = 2, 4, 6, 8) on the layered zirconium phosphates were investigated. [C4mim]Cl was used to explore in detail the factors affecting intercalation. By comparing several starting materials including α-zirconium phosphate (α-ZrP), γ-zirconium phosphate (γ-ZrP) and the corresponding alkylamine preintercalated composites, it was found that the α-ZrP · 2BA (i.e., preintercalated BA were arranged in a bilayer mode at the galleries of α-ZrP) was a suitable host for intercalating ILs. Intercalation was verified with X-ray diffraction (XRD), Raman, UV–Vis and other instrumental approaches. pH effect on immobilization was investigated. Other ionic liquids including [Cnmim]Cl (n = 2, 6, 8) intercalation compounds were prepared. Based on XRD data, the interlayer distances of the studied intercalation compounds were similar, suggesting that the ionic liquids were arranged in an approximately planar manner, as confirmed by molecular modeling.

Hydrogen Storage in a Highly Porous Solid Derived from γ‐Zirconium Phosphate

Having a gas: Topotactic exchange (65 %) of γ-zirconium phosphate with terphenyldiphosphonic acid yielded a pillared material with a specific area of 90 m2 g−1. Subsequent treatment with hypophosphorous acid afforded a material of α type, with no incorporated hypophosphite and a specific area of 400 m2 g−1, which took up 74 cm3g−1 of H2 at 650 Torr and 77 K.