Zirconium metal production

The pyrochemical process of zirconium-hafnium separation is particularly attractive not only because it makes the entire process of nuclear-grade zirconium metal production from zircon more economical than that involving a hydrometallurgical separation stage, but also... 

Shelton, S. M., Dilling, E. D. and McClain, J. H. Zirconium metal production. Proc. Iff Int. Conf. on the Peaceful Uses of Atomic Energy, Geneva, 1955. Paper 533. 

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. 

Zirconium metal is marketed in three forms zirconium-containing silicon—manganese, kon, ferrosiUcon, or magnesium master alloys commercially pure zirconium metal and hafnium-free pure zirconium metal. The use of zkcon for the production of zirconium metal of all three types is ca 5—8% of the total U.S. zkcon consumption. 

Metallothermic reduction of chlorides has been the basis of some very important processes for reactive metals production. Examples include the Kroll and Hunter processes for the preparation of zirconium and titanium, and calcium or lithium reduction processes for the rare earths. 

Suggest a procedure for the industrial production of hafnium-free zirconium metal from baddeleyite (Zr02), on the basis of information given in this chapter and in Appendix C. 

The most important ore for production of zirconium metal is zircon ZrSi04, which occurs in several regions in the form of a beach sand,... 

The zirconium tetrachloride product must then be purified before reduction to metal. In particular, hafnium must be removed to less than 100 ppm Hf Zr because of the high neutron absorption cross-section it exhibits, and phosphorus and aluminum must be removed to even lower specifications due to their deleterious metallurgical impact on the final zirconium alloys. The tetrachloride product is first dissolved in water under carefully controlled conditions to produce an acidic ZrOCl2 solution. This solution is complexed with ammonium thiocyanate, and contacted with methyl isobutyl ketone (MIBK) solvent in a series of solvent extraction columns. Advantage is taken of the relative solubilities of Zr, Hf, and Fe thiocyanate complexes to accomplish a high degree of separation of hafnium and iron from the zirconium. 

Zirconium dioxide is then carbochlorinated a second time (pure chlorination) and converted once again to ZrCl4. This operation is very similar to crude chlorination, but takes place at lower temperature due to more favorable thermodynamics. The purified ZrCl4 product is then reduced to zirconium metal by direct reaction with molten magnesium metal, according to... 

The ZrF sample employed by McDonald et al. ( ) for enthalpy measurement was prepared by dissolving hafnium-free zirconium metal in 48% aqueous HF, and the resulting solution was evaporated to dryness. The crystalline product was heated slowly to 773 K in a platinum boat in a slow current of anhydrous HF. X-ray diffraction showed only crysalline ZrF. Wet analysis indicated 54.6% Zr (theory 54.55) and 44.9% F (theory 45.45). Due to the above facts we are uncertain whether the sample prepared is a mixture of a and B forms of a pure ZrF (B). Smith et al. (4) obtained their ZrF sample from the Oak Ridge National Laboratories, Oak Ridge, Tenn. Since the method of preparation of the compound is unavailable from the report, we do not know what kind of sample they used for measurement. 

X-ray diffraction data obtained for some of those ate complexes are consistent with a zwitterionic form incorporating a four coordinate cyclic phospho-nium center and a pentavalent 18-electron zirconium metal center. It is reasonable to postulate that the first step of the reaction is the nucleophilic attack of the phosphino group in 16a on an acetylenic carbon atom with formation of the corresponding transient zwitterion. In the second step, an intramolecular cyclization of the carbanionic center on the zirconium metal fragment occurs to form stable zirconate products 20 a -f. It was shown that the nature of the het-... 

Use (Unstabilized) Production of piezoelectric crystals, high-frequency induction coils, colored ceramic glazes, special glasses, source of zirconium metal, heat-resistant fibers, (hydrous) odor absorbent, to cure dermatitis caused by poison ivy. (Stabilized with CaO refractory furnace linings, crucibles, solid electrolyte for batteries operating at high temperature. 

Thermal dissociation of Th. Veigel et al. [VI] have prepared massive thorium metal of high purity in lots of several hundred grams each by the Van Arkel-de Boer hot-wire process, which has been used for semicommercial production of zirconium as described in Sec. 8.4 of Chap. 7. The process is less suitable for thorium because the thorium metal product is less coherent, so that batch sizes are small. In this process, ThU is evaporated at 455 to 480°C in an evacuated vessel containing a metal filament heated to 900 to 1700°C. The iodide dissociates at the higher temperature,... 

Zirconium dioxide can be partially reduced to zirconium metal by reactive metals such as calcium or magnesium, but the product is contaminated by some unreduced oxide, owii to the solubility of oxide in the metal. 

In this way zircon, NajSiF, and aluminum are converted to zirconium metal, hafnium-rich zirconium, and by-product (NaF)i.jAlF3 and SiOj. 

The total cycle time is aroimd 40 h, of which 18 h is for the reduction reaction itself. The product of the reaction is a lower layer of spongy zirconium metal mixed with MgG2, covered by a layer of frozen. ... 

Zircon is a sihcate of formula ZrSi04 and occurs as the gemstones hyacinth and zirconite. Synthetic gemstones are prepared from zircon and from the oxide Zr02. Zirconium metal is difficult to produce. Its production requires treatment of the tetrachloride ZrC with magnesium metal. Zirconium metal is silvery-gray, ductile, and malleable. 

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