Zirconium phosphate gel

Addition of a soluble Zr(IV) salt to phosphoric acid results in the precipitation of a gelatinous amorphous solid. The stoichiometric crystalline zirconium phosphate can be prepared by refluxing zirconium phosphate-gel in concentrated phosphoric acid [5]. The procedures for synthesis of zirconium phosphate have been described in detail elsewhere [6]. 

Anhydrous zirconium phosphate (P04/Zr = 2) and the dihydrate are prepared by adding 100 ml of 1 ilf zirconium oxychloride 8H20 dropwise to constantly stirred, refluxing phosphoric acid solution prepared by dissolving two moles of sodium dihydrogenphosphate H2O in 200 ml of 3 ilf HCl. The zirconium phosphate gel is refluxed in its mother liquor for 25 hours and then washed until free of chloride. When air-dried, the dihydrate or y phase was obtained when vacuum-dried over calcium sulfate, the anhydrous a phase was obtained 117). 

Segawa et al. (78,791 have examined the catalytic activity of several zirconium phosphates for 1-butene isomerization. They concluded that the e phase remains active even after evacuation at 773 K, while the zirconium phosphate gel and the a form show significant decreases in activity. The pyrophosphate has the highest activity. All three forms dehydrate upon evacuation at temperatures above 1000 K and eventually become the pyrophosphate ZrP207 above 1300 K as the P-OH groups condense to form P-O-P linkages simultaneous with the total loss of catalytic activity for butene isomerization. P MAS-NMR (79] of zirconium phosphate gel, the a form, and the e form of ZrP (Fig. 12) show that the a form has its phosphorus resonance at — 16.6 ppm, while in the e form it occurs at - 21.7 ppm (with reference to H3FK>4 at 0 ppm). The gel shows peaks at - 11.8,... 

The gels precipitated as described above are not useful in ion-exchange systems because their fine size impedes fluid flow and allows particulate entrainment. Controlled larger-sized particles of zirconium phosphate are obtained by first producing the desired particle size zirconium hydrous oxide by sol—gel techniques or by controlled precipitation of zirconium basic sulfate. These active, very slightly soluble compounds are then slurried in phosphoric acid to produce zirconium bis (monohydrogen phosphate) and subsequently sodium zirconium hydrogen phosphate pentahydrate with the desired hydrauhc characteristics (213,214). 

Adsorption of mercury. All chemicals used were Merck or Baker analytical quality reagents, unless stated otherwise. From the commercially available adsorbents the following were used silica gel 60 A porosity, 0.063-0.200 mm particle size (Merck) charcoal 0.3-0.5 mm particle size, gas-chromatographic quality (Merck) alumina R Woelm hydrous zirconium oxide HZ0-1, 100-200 mesh, (Bio-Rad). Except for zirconium phosphate, which was prepared according to Amphlett ( ), all other sorbents were prepared by coating (precipitation) on acid-purified silica gel, as described in (1 ). The Si0 -NH was prepared according to Leyden et al (11). L... 

Sol-gel methods are used to prepare a heterogeneous, nanometer composite of calcium zirconium phosphate and strontium zirconium phosphate, Cao.sSro.sZrsOn. In this composite, individual domains both expand and contract upon heating, leading to a material with virtually zero thermal expansion over the range 0-500 °C. 

There are several forms of metal(IV) phosphates, including amorphous, crystalline, and pellicular. However, here only the preparation of amorphous zirconium phosphate is described. Phosphoric acid (10 % w/w. 162 ml) was added to zirconyl chloride octahydrate (14.4 g in 112 ml of demineralized water), and stirred at room temperature for 4 h. The resulting gel was washed repeatedly with demineralized water (3 x 500 ml) and centrifuged each time. 

Inorganic ion exchangers include both naturally occurring materials such as mineral zeolites (sodalite and clinoptilolite), the greensands, and clays (themontmorillonite group) and synthetic materials such as gel zeolites, the hydrous oxides of polyvalent metal (hydrated zirconium oxide) and the insoluble salts of polybasic acids with polyvalent metals (zirconium phosphate). 

Early work on the exchange properties of amorphous zirconium phosphate has been summarized by Amphlett (29). In addition, Ahrland et al. (13,15) have studied the exchange behavior of representative fission product ions, for which they found an affinity order of UO, Ce, Y " ", Sr +, Cs+, Rb+, Na+, when amorphous gels of high P04/Zr ratios were used. The separation of certain transplutonium ions (250) on amorphous... 

Matoso, E. Kubota, L.T. Cadore, S. Use of sihca gel chemicahy modified with zirconium phosphate for preconcentration and determination of lead and copper by flame atomic absorption spectrometry. Talanta 2003,60 (6), 1105. 

Moreover, composite membranes based on S-PEEK-WC can be obtained by incorporating an amorphous zirconium phosphate suUbphenylenphosphonate gel with a fixed 20 wt% content. They, indicated as Zr(SPP)/S-PEEK-WC, absorb less water and methanol than the pure S-PEEK-WC and the methanol absorption does not increase significantly with temperature on the contrary of the pure S-PEEK-WC, especially in the case of high DS. The Zr(SPP)/S-PEEK-WC methanol permeability is lower than that of Nafion due to its microstructure with narrow and highly branched channels, which are responsible for the lower methanol crossover. 

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