Nitric acid from zirconium

In the tributyl phosphate extraction process developed at the Ames Laboratory, Iowa State University (46—48), a solution of tributyl phosphate (TBP) in heptane is used to extract zirconium preferentially from an acid solution (mixed hydrochloric—nitric or nitric acid) of zirconium and hafnium (45). Most other impurity elements remain with the hafnium in the aqueous acid layer. Zirconium recovered from the organic phase can be precipitated by neutralization without need for further purification. 

In the TBP process, which was developed in the USA283 and in England,286 zirconium(IV) hydroxide (produced, for example, by the hydrolysis of the material obtained from the caustic fusion of zircon sand) is dissolved in nitric acid to give a solution containing 30-100 g of zirconium (plus hafnium) per litre and 5-8 M free nitric acid. The zirconium is extracted into a 50-60% solution of TBP in a suitable hydrocarbon diluent, the loaded organic phase is washed in 5 M nitric... 

The thorium nitrate solution from the dissolver will be about 9 Af in nitric acid. To obtain satisfactory decontamination of thorium from fission-product protactinium, ruthenium, and zirconium-niobium, it was found necessary to remove all of the nitric acid from the solution and make the solution around 0.15 Af acid-deficient in nitrate ion by converting a fraction of the A1(N03)3 to a water-soluble basic nitrate. This also converts the readily hydrolyzed nitrates of these fission products to basic nitrates that are less extractable than the species present in the acid dissolver solution. 

Zirconium Nitrate. NtO Zr mol wt 339.25. N 16.52%, O 56.59%, Zr 26.89%. Zr(NOj)4. Prepn according to the equation ZrCl4 + 4N2Os — Zr(N03)4 + 4NOjCl Field, Hardy, Proc. Ckem. Soc. 1962, 76. Penlahydrate obtained from strong nitric acid. The zirconium nitrate of commerce is usually somewhat basic. 

High molecular weight primary, secondary, and tertiary amines can be employed as extractants for zirconium and hafnium in hydrochloric acid (49—51). With similar aqueous-phase conditions, the selectivity is in the order tertiary > secondary > primary amines. The addition of small amounts of nitric acid increases the separation of zirconium and hafnium but decreases the zirconium yield. Good extraction of zirconium and hafnium from ca 1 Af sulfuric acid has been effected with tertiary amines (52—54), with separation factors of 10 or more. A system of this type, using trioctylarnine in kerosene as the organic solvent, is used by Nippon Mining of Japan in the production of zirconium (55). 

Zirconium tetrafluoride dissolves in dilute acid without hydrolysis, and can be recovered as the monohydrate [14956-11-3] by crystallization from nitric acid solutions. If the solution is acidified with hydrofluoric acid, ZtF 3H20 [14517-16-9] crystallizes at 10—30 wt % HF HZtF 20 [18129-16-9] crystallizes at 30—35 wt % HF, and at higher HF concentrations H2ZtF -2H20 [12021 -95-3] can be recovered. 

Nitrates. Anhydrous zirconium tetranitrate [12372-57-5] Zr(N02)4, is prepared from zirconium tetrachloride and nitrogen pentoxide (201). The hydrated compounds are obtained from aqueous nitric acid (165) Zr0(N02)2 2H20 [20213-65-4] is most commonly used Zr(N02)4 5H20 [12372-57-5] can be produced from strong nitric acid. 

It can be seen from Figure 5.18 that the KD values for zirconium are higher than those for hafnium at all nitric acid concentrations. This is because the dissolution of zirconium nitrate (Zr(N03)4) into zirconyl (Zr02+) and nitrate (NOj) ions takes place to a lower extent as compared to the corresponding dissolution of hafnium nitrate in an aqueous medium. Hence, separation is feasible. However, at higher nitric acid concentrations the separation factor is reduced significantly because the dissociation of hafnium nitrate (Hf(NOs)4) decreases sharply with increasing nitric acid concentration, with the result that the separation factor, p, falls off rapidly. Hence, the separation process calls for the adjustment of the nitric acid concentration to a suitably low value. 

After adjusting to 2 mol 1 1 in hydrochloric acid, 500 ml of the sample is adsorbed on a column of Dowex 1-XS resin (Cl form) and elution is then effected with 2 M nitric acid. The solution is evaporated to dryness after adding 1M hydrochloric acid, and the tin is again adsorbed on the same column. Tin is eluted with 2 M nitric acid, and determined in the eluate by the spectrophotometric catechol violet method. There is no interference from 0.1 mg of aluminium, manganese, nickel, copper, zinc, arsenic, cadmium, bismuth, or uranium any titanium, zirconium, or antimony are removed by ion exchange. Filtration of the sample through a Millipore filter does not affect the results, which are in agreement with those obtained by neutron activation analysis. 

Preequilibration of the solvent may be required. In some systems, this cost is minimal, but in others it may be high for example, in uranium extraction from sulfate solutions using tertiary amines, the sulfuric acid preequilibration of the solvent before extraction is a few cents or less per pound of UsOg produced. By comparison, in a TBP-HNO3 system for the recovery of zirconium, the preequilibration costs, using nitric acid, amount to about 50 cents per pound of Zr produced. 

In the extraction and separation of zirconium from hafnium in a nitric acid system, using TBP, the system operates best if run at about 10% less than saturation [56]. As saturation of the solvent is approached, a zirconium compound precipitates in the presence of the solvent, causing cruds and emulsions. This problem is also encountered in rare earth circuits using DEHPA. 

Cerous iodates and the iodates of the other rare earths form crystalline salts sparingly soluble in water, but readily soluble in cone, nitric acid, and in this respect differ from the ceric, zirconium, and thorium iodates, which are almost insoluble in nitric acid when an excess of a soluble iodate is present. It may also be noted that cerium alone of all the rare earth elements is oxidized to a higher valence by potassium bromate in nitric acid soln. The iodates of the rare earths are precipitated by adding an alkali iodate to the rare earth salts, and the fact that the rare earth iodates are soluble in nitric acid, and the solubility increases as the electro-positive character of the element increases, while thorium iodate is insoluble in nitric acid, allows the method to be used for the separation of these elements. Trihydrated erbium iodate, Er(I03)3.3H20, and trihydrated yttrium iodate, Yt(I03)3.3H20,... 

The ZEALEX Process Researchers from KRI have shown that the zirconium salt of dibutyl phosphoric acid (ZS-HDBP) was soluble in Isopar-L in the presence of 30% TBP. This super PUREX solvent, known as ZEALEX, extracts actinides (Np-Am) together with lanthanides and other fission products, such as Ba, Cs, Fe, Mo, and Sr from nitric acid solutions. The extraction yields depend on both the molar ratio between Zr and HDBP in the 30% TBP/Isopar-L mixture and the concentration of HN03 (232). Trivalent transplutonium and lanthanide elements can be stripped together from the loaded ZEALEX solvent by a complexing solution, mixing ammonium carbonate, (NH4)2C03, and ethylenediamine-N.N.N. N -tetraacetic acid (EDTA). An optimized version of the process should allow the separation of... 

Shmidt, O.V., Zilberman, B.Ya., Fedorov, Yu.S., Suglobov, D.N., Puzikov, V.A., Mashkov, L.G., Palenik, Yu.V., Glekov, R.G. Extraction properties of dibutylphosphoric acid zirconium salt in recovery of transplutonium and rare-earth elements from nitric acid solution. Radiokhimiya (2002), 44 (5), 428 133. 

Zilberman, B.Y., Goletskii, N.D., Shmidt, O.V., Puzikov, E.A., Blazheva, I.V., Egorov, G.E., Afanas ev, O.P. 2007. Distribution of HDBP in two-phases systems consisting of aqueous nitric acid, organic diluent (with or without TBP), and HDBP or its zirconium salt. Radiochemistry 49(4) 391-396. (Translated from Radiokhimimiya 49(4) 344—347.)... 

When researching the process of zirconium extraction by tributyl-phosphate from nitric acid solution, two factors, Xi and X2 have been analyzed. The observed factors and response are shown by these relations ... 

Zirconium ores contain 1+3% of hafnium, and the construction requirement demands its contents to be less than a hundredth part of one per cent. Extraction procedures of separating zirconium and hafnium proved to be the best. The most frequently used extraction is by TBF in an inert solvent from nitric acid solutions. 

According to the results of different authors [61], the concentration of the sum of metals goes from 35 to 120 g/1. It is aggregate to chose values from 20 to 150 g/1 for the domain of concentration of the sum of metals. The other factor-concentration of nitric acid below 3 mol/1 has as a consequence poor extraction of zirconium and hafnium. With an increase of acid concentration above 5 mol/g, hafnium separates well in organic phase, but its separation falls. We choose the domain of nitric acid concentration from 3 to 8 mol/g. 

Normally, nitration of deactivated compounds (and therefore polynitration of toluene) is carried out using aggressive nitric acid - oleum mixtures. Dinitration of toluene with mixed acids produces a 4 1 ratio of 2,4- and 2,6-dinitrotoluenes, from which the former is isolated for manufacture of toluenediisocyanate (TDI) and toluenediamine, both of which are used in the manufacture of polyurethanes. Zirconium and hafnium derivatives catalyse nitration of o-nitrotoluene, but ratios of 2,4- 2,6-dinitrotoluene are modest (66 34).12 Dinitration of toluene using Claycop (copper nitrate on K10 clay), acetic anhydride and nitric acid in the presence of carbon tetrachloride produced dinitrotoluenes in a yield of 85% with a ratio of 2,4- 2,6-dinitrotoluene of 9 1.13 This method, however, requires a large excess of nitric acid, the use of an unacceptable solvent and long reaction times. The direct nitration of toluene to 2,4-dinitrotoluene using nitric acid over a zeolite P catalyst, with azeotropic removal of water, is reported to give a 2,4 2,6 ratio of 14, but full results are yet to be published.14... 

Potassium iodate solution white precipitate of cerium(IV) iodate, Ce(I03)4, from concentrated nitric acid solution (difference from cerium(III) thorium and zirconium give a similar reaction). 

Hydrous zirconium oxide and phosphate may be obtained from Bio-Rad Laboratories, Richmond, Calif. As ordinarily supplied, the oxide is severely contaminated with chloride, but at a modest extra cost, Bio-Rad will provide oxide in the nitrate form from which most of the chloride has been leached with 0.1 if nitric acid. This is the material that has been used, but even it requires exhaustive washing to remove the last traces of chloride, t Perchloric add may be substituted for nitric. 

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