US2690376A - Recovery of pure uranium compounds from ores - Google Patents

Description

Sept. 28, 1954 l, HOFFMAN 2,6?9376 RECOVERY OF PURE URANIUM COMPOUNDS FROM ORES Filed June 17, 1942 PREFERRED P/PO CED U/EE GEN us ORE PEEP/3R5 ORE Foe DIGEST/0N PULVER/LE J1 H N0 v 1"" [+1 3 V D/GE57' T l E W CONVERT URANIUM L 4- E P E To VA y UEAHYL NITRATE r- ETHER EXTRACT Ream Q l 5U5JECT To EXTRACT f PERU/Y FOR I FURTHER URANYL NITRATE I ETHE'? fXTEACT/D EXTRACT/0H WITH ETHER 0F Uzmuum NITRATE 47 .L

l H 0 Pue/E/Eo BYMIHOR l l s A 2 V WATER EXTRACTION 5 P20011615 5 i MTEE ExTRAcTm/v Y RECOVER [JEAN/um FROM ETHEE EVAPOEA TE /GNITE 7b 5mm URANIUM 0x/ DE Jh/wEs Z HOFFMAN INVENTOR ATTORNEY Patented Sept. 28, 1954 RECOVERY OF PURE URANIUM COMPOUNDS FROM ORES Application June 1'1, 1942, Serial No. 447,465

(Granted under Title 35, U. S. Code (1952),

sec. 266) 4 Claims.

The invention or discovery described herein may be mad and used by or for the Government of the United States without the payment to me of any royalty therefor.

This invention relates to a method of ore treatment, and more particularly to a method of recovering uranium oxide from uranium-bearing ores as, for example, pitchblende, carnotite, autunite or becquerelite.

Various methods have heretofore been proposed for the recovery of uranium from such ores but in the main, such recovery has been incidental to the disassociation of other elements, as for example, radium therefrom. Furthermore, the methods heretofore in use have been subject to various disadvantages, such as the requirement of an undue length of time, the recovery of uranium in an impure state, contaminated by such substances as vanadium and/or molybdenum, and the necessity of utilizing relatively expensive reagents.

The primary object of this invention is, therefore, the provision of a process of recovering uranium oxide directly from uranium-bearing ores in a high state of purity, in a comparatively rapid, simple and efficient manner by a method utilizing only relatively plentiful and inexpensive reagents.

A secondary object is the recovery of uranium as above stated in a manner calculated to reduce to a minimum the hazard of fire or explosion.

Other objects will in part be obvious and in part, pointed out hereinafter, as the disclosure of the invention proceeds.

It may here be pointed out that present military as well as economic usages require increasing quantities of relatively pure uranium oxide and that, whereas heretofore uranium has been largely treated as a by-product, it has now become sound practice to recover uranium as a principal product, the various other constituents of the ores thereby becoming by-products. An additional advantage of the present invention, also, lies in the fact that after the extraction of uranium in the manner hereinafter described, the residual matter contains such elements as radium in a materially increased concentration permitting a relatively high yield in radium recovery by known conventional processes.

Referring now to the invention proper, it has heretofore been known that uranyl nitrate UO2(NO3)2.6H2O is relatively highly soluble in ether but such facts have never, to my knowledge, been employed in uranium ore treatment. The present invention contemplates broadly the application of nitric acid directly to uraniumbearing ores to convert the uranium content to uranyl nitrate, the absorption of the uranyl nitrate in ether, reabsorption of the uranyl nitrate from the ether in water, evaporation of the water and conversion of the uranyl nitrate to uranium oxide, and is based on my discorvery that, unexpectedly, such process when carried out in the manner hereinafter described, effects a recovery, in a single treatment, of approximately two-thirds of the original uranium content of the ore, substantially free from impurities while leaving substantially all of the radium content in the residue, thus providing a relatively high residual concentration for sub-processing. It has further been discovered that retreatment, in the manner hereinafter described, of the residual matter resulting from the initial extraction of two-thirds of the uranium content of the ore will further result in the extraction of substantially two-thirds of the remaining uranium. The process can, therefore, be carried out repeatedly until the quantity of extracted uranium becomes so minute as to render repeated operations economically unsound.

In detail, on a laboratory scale, the invention may be practiced as follows:

Example 1.-Ea3traction of uranium oxide from carnotite ore utilizing ethyl ether Place 50.0 grams of pulverized carnotite (20 mesh or finer) in a 600 ml. beaker and add ml. of dilute nitric acid (1+1). Cover the beaker and digest on a steam bath for approximately half an hour at about 100 C. At the conclusion of this period uncover the beaker and evaporate the resultant solution to dryness. Allow the residue to cool and add approximately 15 ml. of water to loosen the mass in the beaker. The cooled residue may now be transferred to a 300 ml. Erlenmeyer flask to facilitate handling. Add 50 ml. of ethyl ether [(C2H5) 20] to the flask, stopper and shake vigorously for two or three minutes. The ether, which should be almost clear, should now be poured off into a separatory funnel. Repeat this procedure three times (making four extractions in all) using 50 ml. of other each time.

Now to the combined extracts of ether add 2 ml. of water and shake vigorously for at least one minute, then allow the mixture to separate into two layers and drain off the water. A relatively small portion of the uranyl nitrate may be retained in the water so drawn on and this may be saved for subsequent treatment if it is desired to recover this portion of the uranyl nitrate. Repeat the above operation twice, (making three extractions in all) each time utilizing two ml. portions of water and withdrawing the water.

The ether in the separatory funnel now contains substantially all the uranyl nitrate in a relatively high state of purity.

It may here be pointed out that the various impurities found in carnotite and other uranium ores are, in the main, more soluble in water than in ether. Hence, the mixture and agitation of these two substances with as small a quantity of water as 1% will extract the bulk of these impurities from the ether. Uranyl nitrate, though more soluble in water than in ether, is nonetheless so soluble in ether as to be substantially unaffected by the relatively small percentage of water above described. A larger percentage of water will, however, as hereinafter described, result in the transfer of the relatively pure uranyl nitrate from solution in ether to solution in water.

After the steps above described, the ether may be cautiously evaporated and the residue ignited at a temperature of 1000 C. in a known manner to produce uranium oxide.

However, due to the possibility of violent reaction between ether and uranyl nitrate, if the temperature at which the ether is evaporated becomes too high, and likewise to conserve the ether for reuse, the following procedure is preferred:

To the approximately 200 ml. of ether solution above described, add 20 ml. (about of water and shake vigorously for one minute or more, allow the liquid to separate into two layers and drain the water into a suitable receptable. Repeat with successive 20 ml. portions of water until the ether above the water is substantially colorless. Three or four such extractions are usually sufficient to extract the uranyl nitrate, due to the relatively high solubility thereof in water, as mentioned previously. The remaining ether may be reutilized in treating the next batch of ore.

Now evaporation of the combined water extracts which may be accomplished without undue risk of fire or explosion, will leave a residue of substantially pure UO2(NO3)2.6H2O, which may be readily converted at 1000 C. to U308 in a known manner.

Example 2.--Extraction of uranium oxide from uraninite or pitchblende utilizing iso-propyl ether Place 50.0 grams of pulverized pitchblende (20 mesh or finer) in a suitable receptacle and add 100 ml. of diluted nitric acid (1+1) and proceed as in Example 1 to the step of adding ether. Then add 250 ml. of iso-propyl ether (CHa l: cut

and agitate vigorously and drain off as in Example 1. Repeat this process three times and. add to the combined ether so withdrawn ten ml. of water. Proceed as in Example 1 until substantially all the pure uranyl nitrate is in solution in the ether.

With iso-propyl as well as the ethyl ether it is desirable to redissolve the uranyl nitrate in water and to accomplish this, 100 ml. of water may now be added to the ether and the mixture agitated and separated as before, the process being repeated until the ether is substantially colorless, whereupon procedure as in Example 1 will yield uranium oxide.

The results achieved by the process described in Example 2 are substantially the same as those achieved in the process described in Example 1, with the exception that the use of ethyl ether results in the elimination of a slightly greater percentage of impurities and the yield of slightly greater quantities of uranium due to the higher solubility of uranyl nitrate therein.

In the accompanying drawing constituting a flow sheet, the reagents employed in the preferred procedure are indicated in the left hand column. The various process steps are indicated in the center column (it being noted that each step, although several repetitions thereof may be required is indicated as a. single block), and the resultants are shown in the third column. Return of reagents for reuse is indicated by dotted lines. The fourth column to the right indicates the generic steps of the process.

As will be apparent from the foregoing descriptions and the attached flow sheet, the process herein described is exceptionally rapid as well as economical. The reagents emloyed, ether, nitric acid and water, are inexpensive and in the case of ether and nitric acid may be reutilized repeatedly, very small quantities being lost in successive operations. The recovery of uranium is thorough and, as previously pointed out, by retreatment of the residue, successive fractional portions of the remainder may be extracted until the yield becomes so minute as to be economically unwarranted. Furthermore, other constituents of the ore which are regarded for the purpose of uranium extraction as impurities, but which may be of high value (1. e. radium) and rare earth elements are left in condition to be readily recovered by known processes. In fact, in the case of radium the utilization of this process initially leaves in the ore a relatively higher radium concentration, thus facilitating recovery thereof.

From the foregoing description it will now be apparent to those skilled in the art that the instant invention provides a practical, inexpensive and relatively simple method of extracting uranium directly from ore in a manner fulfilling the stated objects of this invention and others, including many advantages of great commercial utility.

It is to be understood that all matter hereinbefore set forth is to be considered as illustrative and not in a limiting sense, and that the scope of the inventive concept is limited only by the appended claims.

I claim as my invention:

1. A method of obtaining highly purified U303 from a uranium containing ore which comprises digesting the uranium containing ore with nitric acid to produce uranyl nitrate, evaporating said digested ore mass to dryness, treating said dried ore mass with an aliphatic ether to selectively extract the uranyl nitrate therefrom, washing said ether extract with not more than 1% by volume of Water several times to remove impurities, separating the purified ether layer successively from the several aqueous wash layers, extracting the highly purified uranyl nitrate from the ether with several portions of Water, each having a volume of about 10% of the volume of the ether being extracted, combining said water extracts, evaporating said combined extract to dryness to leave a residue of substantially pure UO2(NO3) 2.6H2O, and the heating said residue at 1000 C. to convert it to U308- 2. A method of obtaining highly purified U308 from a uranium containing ore which comprises digesting the uranium containing ore with nitric acid to produce uranyl nitrate, evaporating said digested ore mass to dryness, treating said dried ore mass with an aliphatic ether to selectively extract the uranyl nitrate therefrom, washing said ether extract at least twice with not more than 1% by volume of water to remove impurities, separating the purified ether layer successively from the several aqueous wash layers, extracting the highly purified uranyl nitrate from the ether at least twice with about by volume of water, combining said water extracts and evaporating them to dryness, and converting the uranyl nitrate thus obtained to purified UaOa by heating.

3. A method of obtaining highly purified UaOa from carnotite which comprises digesting the carnotite with nitric acid to produce uranyl nitrate, evaporating said digested ore mass to dryness, treating said dried ore mass with ethyl ether to selectively extract the uranyl nitrate therefrom, washing said ether extract at least twice with not more than 1% by volume of water to remove impurities, separating the purified ether layer successively from the several aqueous wash layers, extracting the highly purified uranyl nitrate from the ether at least twice with about 10% by volume of water, combining said water extracts and evaporating them to dryness, and converting the uranyl nitrate thus obtained to purified UaOa by heating.

4. A method of obtaining highly purified U308 from pitchblende which comprises digesting the pitchblende with nitric acid to produce uranyl nitrate, evaporating said digested ore mass to dryness, treating said dried ore mass with iso- References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 440,143 Dode Nov. 11, 1890 1,897,740 Teller Feb. 14, 1933 2,211,119 Hixson Aug. 13, 1940 2,227,833 Hixson Jan. 7, 1941 FOREIGN PATENTS Number Country Date 16,228 Great Britain Sept. 14, 1916 OTHER REFERENCES Crookes, Proceedings of the Royal Society of London, volume 66, pp. 409-422 (1900). (Copy in scientific Library.)

Boltwood, American Journal of Science, 4th Ser., volume 25, page 276 (1908). (Copy in Scientific Library.)

Misciattelli, London, Edinburgh and Dublin Philosophical Magazine, 7th Ser., volume 7, page 670 (1929). (Copy in Scientific Library.)

Treatise on Physical Chemistry, by Taylor, 2nd ed., vol I (1931), D. Van Nostrand Co., Inc., New York, N. Y., pp. 485-487.

Claims (1)

1. A METHOD OF OBTAINING HIGHLY PURIFIED U3O8 FROM A URANIUM CONTAINING ORE WHICH COMPRISES DIGESTING THE URANIUM CONTAINING ORE WITH NITRIC ACID TO PRODUCE URANYL NITRATE, EVAPORATING SAID DIGESTED ORE MASS TO DRYNESS, TREATING SAID DRIED ORE MASS WITH AN ALIPHATIC ETHER TO SELECTIVELY EXTRACT THE URANLY NITRATE THEREFROM, WASHING SAID ETHER EXTRACT WITH NOT MORE THAN 1% BY VOLUME OF WATER SEVERAL TIMES TO REMOVE IMPURITIES, SEPARATING THE PURIFIED ETHER LAYER SUCCES-

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