Zirconium ions

Electrolysis. Electrowinning of zirconium has long been considered as an alternative to the KroU process, and at one time zirconium was produced electrolyticaHy in a prototype production cell (70). Electrolysis of an aH-chloride molten-salt system is inefficient because of the stabiUty of lower chlorides in these melts. The presence of fluoride salts in the melt increases the stabiUty of in solution, decreasing the concentration of lower valence zirconium ions, and results in much higher current efficiencies. The chloride—electrolyte systems and electrolysis approaches are reviewed in References 71 and 72. The recovery of zirconium metal by electrolysis of aqueous solutions in not thermodynamically feasible, although efforts in this direction persist. 

Cubic zirconia Oxygen ions O Zirconium ions... 

The effect of fluoride ions on the electrochemical behaviour of a metal zirconium electrode was studied by Pihlar and Cencic in order to develop a sensor for the determination of zirconium ion. Because elemental zirconium is always covered by an oxide layer, the anodic characteristics of a Zr/Zr02 electrode are closely related to the composition of the electrolyte in contact with it. These authors found the fluoride concentration and anodic current density to be proportional in hydrochloric and perchloric acid solutions only. In other electrolytes, the fluoride ion-induced dissolution of elemental zirconium led to an increase in the ZrOj film thickness and hindered mass transport of fluoride through the oxide layer as a result. The... 

Co(II) acetate in acetic acid with acetaldehyde also gives good selectivity in the formation of adipic acid (73% at 88% conversion at 90oC).200 The role of acetaldehyde is to promote oxidation of Co(II) to Co(III) and maintain a steady-state concentration of Co(III). Later during the reaction, however, cyclohexanone formed as an intermediate in oxidation serves as promoter. Zirconium ions also exhibit a significant promoter effect.201... 

In other ions a C5H3 unit is shown as o-bonded to both zirconium ions with the formation of a five-membered ring (II). 

The influence of an anionic counterpartner of the metallocenium cation on its stereospecificity can also be seen when considering polymerisation conditions such as the kind of solvent and temperature. For example, the loss of stereospecificity when propylene polymerisation with Me2C(Cp)(Flu)ZrCl2-based catalysts is performed in polar solvents [142] seems to be caused by inversion of the configuration of the solvent-separated zirconium ion via... 

A second solvent extraction process (Pharex) was developed to partition the transcurium actinides from the americium and curium in the Tramex product ( 3) The Pharex process utilized 2-ethylhexyl phenylphosphonic acid as the extractant for the transcurium actinides. During early operations/ the selectivity of the Pharex extractant was found to be severely reduced by the presence of zirconium ions, which were introduced into the process solutions by corrosion of Zircaloy-2 equipment in TRU. At zirconium concentrations above 10 ppm, the achievable separation began to be diminished and, at 100 ppm, a practical separation could not be made (4). Thus, a replacement for the Pharex process was needed, and the LiCl AIX process was the most immediate alternative ... 

The results of fundamental investigations of the formation of hydrated zirconium dioxide are reported in [41]. The oxidation degree of zirconium ions is -t4 in nearly all its compounds. Possessing rather large radius (0.092 nm) and rather low ion potential, it forms sterically maximal number of bonds. Accordingly, in the major part of its compounds, Zt ions exhibits coordination number 8. 

TABLE TITLE Zirconium (Zr) Zirconium, alpha (Zr) Zirconium, beta (Zr) Zirconium (Zr) Zirconium (Zr) Zirconium (Zr) Zirconium, ion (Zr ) Zirconium, ion (Zr )... 

Figure 6. Sequence of events in reacting zirconium ions with a mixture of phenyl-phosphonic and phosphorous acids.

Zirconium ions (in dilute HCl) react with Eriochrome Cyanine R (ECR) (formula 4.17) to form red complexes. The complex formed at a deficiency of ECR ( max = 515 nm) is favoured by a more acidic medium (pH 0-1). Conversely, the complex formed in the presence of excess of ECR ( max = 540 nm) is formed at lower acidities (pH 1-2). The absorption maximum of Eriochrome Cyanine R in dilute HCl is at 475 nm. 

Zirconium (Zr, at. mass 91.22) occurs in its compounds exclusively in the IV oxidation state it is similar to titanium in its properties. In HNO3 and HCIO4 solutions, zirconium Zr and zirconyl ZrO ions occur. They tend to polymerize as the concentration increases. Hydrolysis of zirconium ions begins at pH 1-1.5. Zr(OH>4 has no amphoteric properties. Zirconium forms stable complexes with fluoride, EDTA, and hydroxy acids. 

Zirconium (like Hf) reacts with Arsenazo III (formula 4.10) in 2-10 M HCl medium to form an emerald-green water-soluble complex. At this acidity hydrolysis and polymerization of zirconium ions no longer occur, which secures good reproducibility. 

Zr-Zr bonds are 7, 4, and 1, respectively. The zirconium ions form layers parallel to the (100) planes of the unit cell, with the Oj ions on one side and the 02 ions on the other side. The distance between two layers of zirconium ions is larger when they are separated by Oj ions. 

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