Aqueous zirconium carbonates

Dervin [72DER] and Veyland [99VEY]. The two latter referenees together with [80MAL/CHU], [82KAR/CHU] inelude most of the usable data and, therefore, have been reviewed in great detail. 

One of the major difficulties in evaluating Zr complexation constants is the unavoidable coexistence with hydroxo species over all pH regions of interest. Therefore, any determination of stability constants for complex formation with ligands other than OH critically depends on the quality and precision of the stability constants assigned to the hydrolysis. This is particularly true in the carbonate system where OH and CO3 concentrations will co-vary with pH. In the course of the review, it became evident that all Zr-carbonate constant determinations found in the literature relied on a hydrolysis model that differs from that selected in this review. Consequently, all constant determinations had to be re-evaluated. Due to the limited information provided by most references (missing raw data, insufficient declaration of experimental conditions), or because of the inherent unsuitability of the data, a meaningful reinterpretation was possible only in a few cases (mainly for potentiometric titrations). Table V-37 is a compilation of the Zr-carbonate complexation constants reported in the 

Method Ionic strength t logioAi logioA Reference 

From the study of the literature, it clearly emerged that a considerable number of Zr-carbonate species exist (including polynuclear complexes and ternary carbonato-hydroxo species). The domain of existence of the various species apparently depends on absolute Zr and carbonate concentrations, COa/Zr total concentration ratios and pH. Nevertheless, there is convincing evidence that Zr(C03)4 is the limiting complex when carbonate concentrations are in large excess of zirconium concentrations i.e. COa/Zr ratios above ca. 10). Although the results and the re-interpretations obtained in 

From most of the data mentioned above, it was not possible to derive reliable thermodynamic constants. A unique exception were the solubility measurements carried out by Dervin [72DER] on amorphous Zr(OH)4 in NH4NO3 (/ = 1 M), from which the following conditional constant for the formation of Zr(C03)4 could be derived  

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Oxide Chlorides. Zirconium oxide dichloride, ZrOCl2 -8H2 0 [13520-92-8] commonly called zirconium oxychloride, is really a hydroxyl chloride, [Zr4(OH)g T6H2 0]Clg T2H2O (189). Zirconium oxychloride is produced commercially by caustic fusion of zircon, followed by water washing to remove sodium siUcate and to hydrolyze the sodium zirconate the wet filter pulp is dissolved in hot hydrochloric acid, and ZrOCl2 -8H2 O is recovered from the solution by crystallization. An aqueous solution is also produced by the dissolution and hydrolysis of zirconium tetrachloride in water, or by the addition of hydrochloric acid to zirconium carbonate. 

All aqueous zirconium compounds have polymeric structures, sometimes with ligands bonded to the zirconium-based polymer. Whether ligands are bonded to the zirconium depends on the counterion. In very general terms, oxygenated ions such as carbonate and sulphate bond to the zirconium whilst halides such as chloride do not. 

The aqueous chemistry of zirconium is complex and dominated by hydrolysis. One aspect is that polymerization takes place when salt solutions are diluted. The polymeric species can be cationic, anionic, or neutral. Polymers that are formed include ammonium zirconium carbonate, zirconium acetate, and zirconium oxychloride. 

All of the members of the final review team contributed, if not text, then comments to all of the chapters of the book. Their primary responsibilities for the different sections/chapters were divided as follows. Paul Brown prepared the introduction, and the sections on elemental zirconium, the zirconyl ion, the gaseous zirconium oxides, zirconium hydride, the halogen compounds and complexes, the chalcogen compounds and complexes, the Group 15 compounds and complexes, zirconium carbides and silicates. He was assisted by Christian Ekberg in the interpretation of aqueous zirconium complexes in these sections. Some initial work was done by Ken Jackson on the zirconium sulphate, nitrate and phosphate compounds and complexes. Bernd Grambow was responsible for the drafting of the sections on zirconium hydrolysis, the ion and the section on crystalline and amorphous zirconium oxides. Enzo Curti drafted the section on the zirconium carbonates. 

Hexafluorozirconic acid [12021 -95-3]], H2ZrP, is formed by dissolving freshly prepared oxide, fluoride, or carbonate of zirconium in aqueous HP. This acid is produced commercially in a concentration range of 10 to 47%. The acid can be stored at ambient temperatures in polyethylene or Teflon containers... 

Degraded TBP process solvent is typically cleaned by washing with sodium carbonate or sodium hydroxide solutions, or both. Such washes eliminate retained uranium and plutonium as well as HDBP and H2MBP. Part of the low-molecular-weight neutral molecules such as butanol and nitrobutane, entrained in the aqueous phase, and 90-95% of the fission products ruthenium and zirconium are also removed by the alkaline washes. Alkaline washing is not sufficient, however, to completely restore the interfacial properties of the TBP solvent, because some surfactants still remain in the organic phase. 

Zirconium and hafnium trifluoracetylacetonates were prepared by Larsen, Terry, and Leddy, who measured some of their properties. They prepared these compounds by the dropwise addition of the ligand to an aqueous solution of the metal oxide chloride, using intermittent addition of sodium carbonate to maintain the proper pH. 

An even more striking reaction of the alkylzirconium compounds formed by hydrozirconation is insertion of carbon monoxide into the C—Zr bond to form zirconium-acyl complexes. For example, 1-hexene or an internal hexene is treated in benzene with (1) to form the alkylzirconium complex (6), which is then allowed to react under 20 psi of carbon monoxide at room temperature. The colorless acyl complex (7) is formed within several hours. An intermediate zirconium carbonyl species is not detected. The acyl complex (7) is converted into an aldehyde (8) on protonolysis, into a carboxylic acid (9) by treatment first with aqueous NaOH and then 30% H2O2, or into an ester (10) by treatment with NBS and then with an alcohol. This procedure differs significantly from... 

The most stable solid oxide phase corresponds to the stoichiometry Zr02. Oxygen deficient Zr02 x or zirconium-oxygen alloys exist only under extremely reducing conditions. Reduction of zirconium dioxide by carbon at 1610 to 1680 K leads to the formation of ZrO 95 [78KUT/ZHE]. Amorphous hydrous oxides and basic salts are known to precipitate from aqueous solution. 

VEY/DUP] Veyland, A., Dupont, L., Rimbault, J., Pierrard, J.-C., Aplincourt, M., Aqueous chemistry of zirconium(IV) in carbonate media, Helv. Chim. Acta, 83, (2000), 414-427. Cited on pages 210, 351. 

In aqueous media where hydrochloric and hypochlorous acid and halogens are present in either vapor or liquid phase, the utility of the above materials of construction is severely lin ited and can best be determined by rates of corrosion study during pilot laboratory operation. Tantalum, zirconium, and titanium are usually resistant but expensive. The plastics are of variable resistance and are severely limited by temperature and solvent attack. Stoneware, Karbate, glass, glazed tile, carbon brick, and enameled steel all have utility within rigid limits. The other metals and alloys are usually questionable but may be desirable for replaceable piarts i... 

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