Zirconium phosphate, precipitation

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). 

These methods may prove useful in the qualitative analysis of organic compounds, once the selectivities of the precipitants are understood. The metallic oxides suffer from the disadvantage of producing a precipitate which is difficult to filter, while calcite and zirconium phosphates produce relatively well-mannered precipitates. Even when the efficiencies of collection of various model compounds in seawater is known, the immense variety of organic compounds in seawater will keep this technique largely qualitative. 

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]. 

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... 

Protactinium (of mass number 231) is found in nature iu all uranium ores, since it is a long-lived member of the uranium series. It occurs in such ores to the extent of about part per million parts of uranium. An efficient method for the separation of protactinium is by a carrier technique using zirconium phosphate which, when precipitated from strongly acid solutions, coprecipitates protactinium nearly quantitatively. Then the protactinium is separated from the carrier by fractional crystallization of zirconium oxychloride. 

Another preparative method in which the rate of precipitation is slow involves slow decomposition of zirconium fluoro complexes [14], These are first prepared by adding an appropriate amount of hydrofluoric acid (HF) to the zirconyl salt and these complexes are decomposed in the presence of phosphoric acid, with a slow stream of nitrogen or water vapor passing through the system. The rate of precipitation of zirconium phosphate is controlled by the rate of removal of HF from the system, and when this is very slow, a highly crystalline a-ZrP is obtained. The gamma form of the metal phosphate differs significantly from the alpha and current discussion will be concerned with the latter phase. 

Hafnium chloride, 4 121 Hafnium phosphate, precipitation of, with zirconium phosphate, 3 71... 

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. 

Zirconium phosphate. Reject. Test if all phosphate has been precipitated by the addition of a drop of the zirconium(IV) nitrate reagent. Add about 0-5 g solid NH4C1, heat to boiling, add a slight excess of dilute NH3 solution (i.e. until the odour of NH3 is permanent in the boiling solution), boil for 2-3 minutes and filter. ... 

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). 

If both Tiand Zr are present, the precipitate of zirconium phosphate may be filtered off (best in the presence of a little macerated filter paper, or a Whatman filtration accelerator), and the filtrate treated with Na2S03 or with Na2S203 solution and warmed. The peroxotitanic acid is reduced and titanium phosphate precipitates. It may be necessary to reduce the acidity of the solution somewhat to precipitate the titanium completely. Zr may also be identified by the alizarin-S reaction. 

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. 

Ri/M 2(P04)3. a double americium zirconium phosphate Ami/3Zr2(P04)3 (M = Zr) was synthesized and characterized by X-ray diffraction methods [74,75], This phosphate belongs to the NZP structure type. The NH4H2PO4 solution was added to the starting solution of americium nitrate and ZrOCU thermal treatment of the precipitates was carried out stage-by-stage up to 800°C. 

In contrast to the conventional approach whereby various organic groups are subsequently bound to a previously prepared surface, we have been synthesizing a broad series of anchored, layered-structure solids by precipitating the pre-derived phosphonate salts with tetravalent metal ions. The two-dimensional backbone has the zirconium phosphate structure however, substituted for hydroxylic groups are the desired organics, oriented away from the basal surfaces in a bilayered fashion in the interlayer region. 

For precipitation of zirconium as the hydroxide, Fe(III) or Ti is used as scavenger [2]. Depending on the elements from which the zirconium is to be separated, Zr(OH)4 is precipitated with either ammonia or NaOH solution. Zirconium is separated from titanium by precipitation in the presence of H2O2. If zirconium phosphate is dissolved in oxalic acid and the solution made alkaline with NaOH solution, Zr(OH)4 is precipitated (more sparingly soluble than the phosphate) [3J. 

After fusion of the sample or of the ignited hydroxide or phosphate precipitate with Na2C03 or NaOH + Na202, followed by leaching of the melt with water, zirconium is in the precipitate, whereas phosphate, fluoride, and sulphate, as well as As, V, Cr, Mo, W, and A1 remain in anionic forms in the solution. 

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