Zirconium hydrogen phosphates

Sodium hydrogen zirconium phosphate [34370-53-17 is an ion-exchange material used in portable kidney dialysis systems which regenerate and reckculate the dialysate solution. The solution picks up urea during the dialysis. The urea reacts with urease to form ammonia, which is absorbed by the sodium hydrogen zirconium phosphate. 

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The main interest in zirconium phosphates relates to their ion-exchange properties. If amorphous zirconium phosphate is equiUbrated with sodium hydroxide to pH 7, one hydrogen is displaced and ZrNaH(P0 2 3H20 [13933-56-7] is obtained. The spacing between the zirconium layers is increased from 0.76 to 1.18 nm, which allows this phosphate to exchange larger ions. 

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). 

Layered inorganic solids have been used for site isolation, for example, nickel phosphine complexes confined within the interlayer spaces of sepiolite have been used as olefin hydrogenation catalysts [63], and similarly there has been the encapsulation of metal complexes into zirconium phosphates [64], The principal idea is illustrated in Figure 5.8. The metal complex can be encapsulated by covalent means (a) or by non-covalent interactions (b). 

The zirconium phosphate, a-ZrP, behaves as an ion exchanger where both hydrogen ions of the orthophosphate groups are exchangeable with sodium, potassium, and ammonium in two stages [109], It has an exchange capacity of 6.64 mequiv/g [111],... 

In fact the precipitate is of variable composition, depending on the concentrations of zirconium, phosphate, and hydrogen ions. Species like Zr0(H2P04)2 and ZrP04 may also be formed. 

Sodium phosphate solution white precipitate of zirconium phosphate, Zr(HP04)2 or Zr0(H2P04)2, even in solutions containing 10 per cent sulphuric acid by weight and also tartrates and citrates. No other element forms an insoluble phosphate under these conditions except titanium. The latter element can be kept in solution as peroxotitanic acid by the addition of sufficient hydrogen peroxide solution, preferably of 100-volume strength, before the sodium phosphate is introduced. 

Hydrogen peroxide white precipitate of peroxozirconic acid, HOO-Zr(OH)3, from slightly acid solutions this liberates chlorine when warmed with concentrated hydrochloric acid. When both hydrogen peroxide and sodium phosphate are added to a solution containing zirconium, the precipitate is zirconium phosphate (see reaction 3). 

Enones are reduced to saturated ketones by catalytic hydrogenation provided the reaction is stopped following the absorption of 1 mol of hydrogen. " A number of catalysts were found useful for this, including platinum, platinum oxide,Pt/C, " Pd/C, - Rh/C, " tris(triphenylphosphine)rhodium chloride, - nickel-aluminum alloy in 10% aqueous NaOH, and zinc-reduced nickel in an aqueous medium. Mesityl oxide is formed from acetone and reduced in a single pot to methyl isobutyl ketone using a bifunctional catalyst which comprised palladium and zirconium phosphate (Scheme 20). 

The silicon is inactive but phosphorus-30 is a +-emitter. When the irradiated aluminium is dissolved in hydrochloric acid, all the radioactivity goes with the hydrogen, presumably as phosphine. Aqua regia oxidises it to phosphoric acid which can be precipitated as radioactive zirconium phosphate. 

In general, the crystalline form does not hydrolyze to the extent that the amorphous form does (19,123, 237), although ion exchange which is accompanied by an increase in distance between the layers makes the crystalline form more susceptible to hydrolysis (23). Since the j8 and y forms of zirconium phosphate are more open, exchange of cations such as Cs+ and Ba +, which are excluded in the a form, can occur in these forms. Since one hydrogen is opposed to the other, the theoretical capacity of 7.06 meq/gm is not achieved. 

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