Zirconium hydroxide

Another important class of titanates that can be produced by hydrothermal synthesis processes are those in the lead zirconate—lead titanate (PZT) family. These piezoelectric materials are widely used in manufacture of ultrasonic transducers, sensors, and minia ture actuators. The electrical properties of these materials are derived from the formation of a homogeneous soHd solution of the oxide end members. The process consists of preparing a coprecipitated titanium—zirconium hydroxide gel. The gel reacts with lead oxide in water to form crystalline PZT particles having an average size of about 1 ]lni (Eig. 3b). A process has been developed at BatteUe (Columbus, Ohio) to the pilot-scale level (5-kg/h). 

C and 6.9 MPa (70.3 kg/cm ) in 100% selectivity (113). The neoalcohol was also produced in selectivities of 99% by employing zirconium hydroxide catalysts (114,115). The rates of the latter process, however, are reportedly low at Hquid hourly space velocity (LHSV) of <1 kg/catalyst-h. A catalyst from... 

Carbonates. Basic zirconium carbonate [37356-18-6] is produced in a two-step process in which zirconium is precipitated as a basic sulfate from an oxychloride solution. The carbonate is formed by an exchange reaction between a water slurry of basic zirconium sulfate and sodium carbonate or ammonium carbonate at 80°C (203). The particulate product is easily filtered. Freshly precipitated zirconium hydroxide, dispersed in water under carbon dioxide in a pressure vessel at ca 200—300 kPa (2—3 atm), absorbs carbon dioxide to form the basic zirconium carbonate (204). Washed free of other anions, it can be dissolved in organic acids such as lactic, acetic, citric, oxaUc, and tartaric to form zirconium oxy salts of these acids. 

Zirconium reduces almost all oxygen-containing salts. This is the case for alkali hydroxides (accidents with the lithium, sodium and potassium compounds) and zirconium hydroxide, lithium, sodium and potassium carbonates, alkaline sulphates sodium tetraborate and copper (II) oxide. This is true especially for oxidising salts such as alkaline chromates and dichromates, chlorates (accident with potassium salt) and nitrates (accident with potassium salt). 

In the drying of compound intermediates of refractory and reactive metals, particular attention is given to the environment and to the materials so that the compound does not pick up impurities during the process. A good example is the drying of zirconium hydroxide. After the solvent extraction separation from hafnium, which co-occurs with zirconium in the mineral zircon, the zirconium values are precipitated as zirconium hydroxide. The hydroxide is dried first at 250 °C for 12 h in air in stainless steel trays and then at 850 °C on the silicon carbide hearth of a muffle furnace. 

The pure product solution, which on analysis is shown to contain 80-100 g l-1 zirconium oxide, is treated with ammonia to precipitate zirconium hydroxide which, upon calcination at 850 °C, yields pure zirconium oxide. 

In a method described by Yoshimura and Uzawa [ 144], cadmium in seawater is coprecipitated with zirconium hydroxide (Zr(OH)4) prior to determination by square-wave polarography. The precipitate is dissolved in hydrochloric acid, and cadmium concentration is determined from the peak height of the... 

Cadmium Co-precipitation with zirconium hydroxide, dissolution of Square wave polarography at precipitate in hydrochloric acid -0.6 V [144]... 

Organic phosphonates represent another class of anchoring agents, which react with zirconium hydroxide to form pillared structures. These are also referred to as molecularly engineered layered structures (MELS). Layered compounds of organic phosphonates of zirconium with the formula of Zr(RP03)2 have been rec-... 

When ion-exchange resin containing zirconium hydroxide comes into contact with acidic brine in the RNDS , zirconium hydroxide adsorbs bisulphate ions thus sulphate is removed from brine. For regeneration of the ion-exchange resin, a basic solution is supplied and when it comes into contact with the resin, sulphate desorption starts. 

In the operating commercial plant, columns are filled with ion-exchange resin containing zirconium hydroxide. Acidic brine is supplied to the column from the bottom, where bisulphate ions are adsorbed, by way of a fluidised bed arrangement, based on the equations ... 

Ion-exchange resin, containing zirconium hydroxide, is packed into the column to which brine containing iodide is supplied from the top. The observed sequence by rate of removal is iodide ion [Pg.171]

In order to remove effectively iodide by RNDS , oxidation of iodide to iodate or periodate is necessary. Iodide is oxidised to iodate with excess chlorine. Through contact of dechlorinated brine with the ion-exchange resin containing zirconium hydroxide, the iodide is therefore removed from the brine. 

Brine is supplied to the column until the concentration of iodate ions reaches a pre-set value, as measured at the outlet of the column. When this value has been reached, iodate ions held by the zirconium hydroxide are desorbed. Alkaline water is supplied to the column from the top. Iodate ions are desorbed in the following reaction by way of fixed bed ... 

In the brine electrolysis system, silica is also contained in raw salt. Silica will precipitate on to membranes in the presence of calcium, strontium, aluminium and iodine resulting in the loss of current efficiency [8-10]. Silica can also be removed in a column filled with ion-exchange resin containing zirconium hydroxide, just like the iodide ion. 

As was mentioned previously, an effective system, RNDS , has been developed to remove particular impurities from brine used in membrane electrolysis procedures. The basic concept of RNDS is to bring the feed brine into contact with an ion-exchange resin containing zirconium hydroxide for the adsorptive removal of impurities. For the removal of the sulphate ion from brine, commercial plants utilising RNDS are already in service. For the elimination of iodide and silica, pilot-scale testing is being planned. 

The crude tetrachloride mixture of zirconium and hafnium is dissolved in ammonium thiocyanate solution. The solution is extracted with methyl isobutyl ketone (MIBK). MIBK is passed countercurrent to aqueous mixture of tetrachloride in the extraction column. Halhium is preferentially extracted into MIBK leaving zirconium in the aqueous phase. Simultaneously, zirconium tetrachloride oxidizes to zirconyl chloride, ZrOCb. When sulfuric acid is added to aqueous solution of zirconyl chloride, the chloride precipitates as a basic zirconium sulfate. On treatment with ammonia solution the basic sulfate is converted into zirconium hydroxide, Zr(OH)4. Zirconium hydroxide is washed, dried, and calcined to form zirconium oxide, Zr02. 

Zirconium hydroxide is used in glass colorants. The compound also is used to prepare zirconium oxide, sulfate, phosphate, and other salts. 

Elemental composition Zr 57.28%, H 2.53%, O 40.19%. The compound is dissolved in acid and analyzed for zirconium (See Zirconium). Hydroxide is heated at about 550°C and residual Zr02 is measured hy gravimetry. Also, the oxide formed may he identified hy x-ray diffraction. 

Also, the oxide may be prepared in the laboratory by thermal decomposition of zirconium hydroxide or zirconium carbonate ... 

Zirconium sulfate is prepared by the action of sulfuric acid on zirconium hydroxide ... 

Zirconium tetrachloride is obtained as an intermediate in recovering zirconium metal from zircon and other minerals (See Zirconium, Recovery). The tetrachloride is obtained by heating a mixture of zirconium hydroxide and car-... 

Also, tetrachloride can be made by reacting zirconium hydroxide with hydrochloric acid ... 

Zirconium Carbide Zirconium Hydride Zirconium Hydroxide Zirconium Nitrate Zirconium Oxide Zirconium Silicate Zirconium Sulfate Zirconium Tetrachloride Zirconyl Chloride Chemical Substances Index CAS Registry Number Index... 

Diammino-zirconium Tetrachloride, [Zr(NH3)2]Cl4, is prepared by passing dry ammonia gas over solid zirconium tetrachloride at ordinary temperature.2 The compound is a fine white powder which readily loses ammonia in moist air, and is decomposed by water with formation of zirconium hydroxide, Zr(OII)4, and ammonium chloride. At higher temperatures more ammonia is absorbed, and tetrammino-zirconium tetrachloride, [Zr(NH3)4]Cl4, is formed. 

P. T. Cleve obtained an amorphous mass—presumably of thorium perchlorate—by treating thorium sulphate in a similar way. F. P. Yenable and I. W. Smithey prepared zirconyl perchlorate by dissolving zirconium hydroxide in 30 per cent, perchloric acid with 60 per cent, acid, the hydroxide dissolves... 

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