Zirconium oxalate

Zirconium oxalates exist as compounds, double compounds, and mixed oxalato complexes (165,195,225—226). When the carboxylate ligand is a longer alkyl chain, the materials often are called zirconium soaps. 

Oxalic acid solution white precipitate of zirconium oxalate, readily soluble in excess of the reagent and also in ammonium oxalate solution (difference from thorium). 

Available forms Zirconium oxalate complex in oxalic acid solution. 

Zirconium oxalate of composition Zr0(0H)(C204H) was found to have ion exchange properties 360), although the selectivity for the alkali metals was not favorable compared to the phosphate. The oxalate is also chemically unstable in strong base and acid solutions. 

Typical ferroelastic is zirconia, which can be obtained from the unstable compounds in the form of powders. As a result of calcination of zirconium oxalate or hydroxide under non-isothermal conditions, the extreme dependence of the specific surface area of zirconia nanoparticles on heating rate has been revealed. This dependence has been confirmed for both pure Zr02 and stabilized with different dopants (Fig. 5.21). In accordance with [301], the maximum surface area for the amorphous powders of yttrium stabilized zirconia with particle size less than 5 nm, growing during crystallization and coarsening to 8-10 nm, depends on the heating mode. 

On the other hand, the provision of vast numbers of minute nuclei assists the phosphate coating reaction to start at a multitude of centres, resulting in a finely crystalline coating. This effect can be obtained chemically by a predip in a solution of sodium phosphate containing minutely dispersed traces of titanium or zirconium salts or in weak solution of oxalic acid. This type of pre-dip entirely eliminates any coarsening effect due to previous treatment in strong alkalis or acids. 

After separation from other rare earths, ytterbium is usually obtained as its oxide, Yb203. If separated as oxalate, oxalate is converted into oxide by high temperature. Ytterbium oxide is reduced to metallic ytterbium by heating with lanthanum metal in high vacuum. The metal is purified by sublimation and collected over a condenser plate. Aluminum, zirconium, and cerium also are effective reducing agents and may be used instead of lanthanum. 

A variety of peroxo and hydroperoxo complexes of zirconium(IV) and hafnium(IV) have been isolated from aqueous or aqueous methanolic hydrogen peroxide solutions that contain additional ligands such as sulfate, oxalate or fluoride. Examples of recently reported complexes are listed in Table 8 along with characteristic vibrational frequencies and the pH employed in the aqueous preparations. Earlier work on peroxo compounds has been reviewed by Connor and Ebsworth180 and by Larsen.5... 

SZ recovery of copper and zirconium using oxalic acid and sodium fluoride, respectively, as precipitants... 

System 1 is based on MC8 (0.065 M) but needs the addition of TBP (1.5 M) in the organic phase and the introduction of oxalic acid in the liquid waste to prevent the extraction of zirconium by TBP. It has been pointed out that the addition of oxalic acid is necessary for the PALADIN process, previously implemented for the extraction of minor actinides. The addition of TBP which extracts several cations, leads to a lesser selectivity of the solvent. 

For stripping Pu from HDEHP, Fardy recommended an organic reducing agent (6). Our experiments prove that Pu(IV) can be quantitatively stripped by oxalic acid from HDEHP, while extracted zirconium remains in the organic phase. Usually, a decontamination factor of 200-300 for Zr/Pu can be obtained. 

Use may be made of the fact that even solid calcium fluoride reacts with the zirconium-alizarin-S reagent (compare Section IV. 17, reaction 6) and, in consequence, the fluoride test may be carried out in the presence of oxalate and phosphate, which interfere in aqueous solution. The calcium salts are precipitated in neutral or faintly basic solution. The precipitate is ignited and digested with dilute acid. The residue is then tested for fluoride by the zirconium-alizarin-S test the red hue of the reagent disappears and a yellow colouration results (see Section IV.17, reaction 6). 

The zirconium-alizarin-S test (IV.17, 6) may be used if oxalate is known to be absent and also in the absence of sulphates, thiosulphates, nitrites, phosphates, and arsenates in quantities greater than that of the fluoride. 

Oxalic acid or ammonium oxalate solution no precipitate (difference from thorium, zirconium, and cerium). 

Note A solution of zirconium sulphate or a zirconium salt solution containing excess sulphate ions does not give a precipitate with either ammonium oxalate or oxalic acid. This is due to the fact that the zirconium is present as the anion [Zr0(S04)2]2, hence sulphuric acid should be avoided in preparing solutions of zirconium salts. 

Ammonium oxalate solution white precipitate of thorium oxalate, which dissolves on boiling with a large excess of the reagent forming trioxalato-thorate(IV) anion, [Th (COO)2 3]2, but is reprecipitated upon the addition of hydrochloric acid (difference from zirconium). 

Oxalic acid or ammonium oxalate solution white precipitate of cerium(III) oxalate, insoluble in excess reagent (compare thorium and zirconium), and in very dilute mineral acids. 

Some seemingly simple zirconium salts are best regarded as essentially covalent molecules or as complexes examples are the carboxylates Zr(OCOR)4, the tetraace-tylacetonate, the oxalate, and the nitrate. Like its Ti analogue, the last of these is made by heating the initial solid adduct of N205 and N204 obtained in the reaction... 

The thorium compound (10 g.) reacts with water (100 ml.) to give an insoluble portion for which the oxalate/thor-ium mol ratio is 2.67 and a soluble portion which can be recovered by precipitation with alcohol and which has an oxalate/thorium mol ratio of 2.99. The remainder of the oxalate is lost by replacement by hydroxide ion and water and stays in solution. The zirconium and hafnium compounds, on the other hand, can be recrystallized from water with very little loss of oxalate. 

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, oxalic, and tartaric to form zirconium oxy salts of these acids. 

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