CA1181953A - Method and apparatus for recovery of uranium from carbonate leach liquors - Google Patents

Abstract

ABSTRACT OF THE INVENTION

A process and apparatus for recovering uranium from a carbonate solution containing uranium ions whereby the carbonate solution containing uranium ions is brought in contact with a cation exchanger so that a uranium cation is removed from solution and adsorbed by the cation exchanger, and the uranium cation is then removed from the cation exchanger. The treated carbonate solution from which uranium ions have been removed by cation exchange is then further processed by removing carbon dioxide from the treated carbonate solution to produce a decarbonated solution, and passing the decar-bonated solution through a membrane process to remove some remaining impurities.

Description

METHOD AND APPARATUS FOR RECOVERY OF
URAIII II~ F'ROM ~ARBONATE LE~CH LII;2UORS

BACKGROUND OF T~: INVENTION
The present invention relate~ to a method and apparatus for r covery of uranium from carbona~e solu-tions, such as leach liquor~ resulting from leaching of uranium deposits with a ~olution of sodium or ammonium carbonate or bicarbona~e, or even carbon dioxide olu~
tions. A further embodiment of the pre~ent i~vention is directed toward restoring the liguid remaining after the uranium has been removed to a purified condition ~uitable, for instance, for re~urn to the groundwater.
Much of the known uranium now ~xisting in ~e world is in ores with uranium conten~ below 0.2% U30B.
One typical method to remove uranium from ~uch low grade ores is to leach the ore, Pither above ~he ground or under ~he ground (in situ l~aching), to produce a ~airly low ~rade uranium leach liquor, and then to recover the uranium from th~! leach liquor. The end product is typically xeferred to as uranium yellow cake, which is usually sent to a refinery where it is further purified into a form suitable for enrichment and fuel ~abrication.

The waste liquor fol70wing uranium recovery must be treated, particularly during in situ leaching operations. It must be restored to the original ground-water conditions prior to disposal. Recovery of uranium during such a restoration process is highly desirable.
~ everse osmosis, ~ith o:r without a preceediny lime ~oftening step, is one known technigue for xestoring suc~ solu~ions. Residual uranium is not always recover able through such a technigue, because reverse osmosis is not selective; it al~o removes a large number of other dissolved solids from which ~he uranium must later be ~epaxated. Furthermore, the reverse osmosis membxanes scale easily, and pretreatment of reverse osmosis in-fluent feed with acid and polyphosphates is not always an efficient and inexpensive way to prevent scaling.
One of the most inexpensive acid leaching sys-tems utilizes ~ulfuric acid; h~drochloric and nitric acid are effec~ive though ~ometimes con~idered too ex-pensive. Sulfuric acid leaching provides a leach liguor which contains many cations, ~ome of which are divalent or trivalent. Some of these cations are Fe+3, Fe ~, Al+3 Mg+2 ~a~2 Mn~2, Zn~2, Na , and K -Typical prior art methods ~o recover uraniumfrom such leach liguors include precipitation and anion exchange. Some of these methods are disclosed in two books by Robert Kunin, one of the inventors of the present invention: Elements of _on_Ex~han~e (1971) at 102-109, and lon Exchan~e Reslns (1972) at pages 190-197.
These latter two prior art methods also present problems. For instance, direct ~recipitation of uranium ~rom acid leach liquors with such compounds as ammonia is not preferred because the precipitate does not contain a ~ignificantly greater percentage of uranium than the original ore. Also, anion exchange processes adsorb, in addition to uranium anions, HSO~ , S04 2, and a number of other anion sulfate complexes containing titanium, zirconium, vanadium, molybdenum, iron and thorium.

;3 Vanadium, iron, and molybdenum are o~ten adsorbed in highly undesirable guantitie6. Prior art techniques to accommodate this unwanted adsorption of vanadium and ~olybdenum include selective elution, as discussed in 5 U~S. Patent No. 2,864,667 (Bailes et al.3, adjusting the pH of the leach solution, as discussed in U.S.
Patent No. 2,841,468 (Wilson~, and contactiny a reduced pH eluate with activated carbon, as discussed in U.S.
Patent No. 4,092,399 (Narayan e~ al.). Such known tech-niques do not alter ~he fact that anion exchange resinsof~en adsorb molybdenum and vanadium in highly undesir-able quantities.
While it has been hypothesized that highly ~elective cation exchange recins might be able to work on uranium sulfate leach liquors (see Kunin, Elements o~
Ion Exchan~e 104 (1971)~, the process generally used is an anion exchange process/ as discussed in ~errit, The Extractive Metallurqy of Urani~m 137~63 (1971). Cation exchange processes on the products of ~ulfuric, hydro-chloric, or nitric acid leaching adsorb, along with theuranium, even ~ore unwanted ions than anion exchange processes~ such as calcium, magnesium, iron, aluminum and ~o forth. Liguid cation exchangers ~uch as perflu-orooctanoic acid and di-2-ethylhexylphosphoric a~id (D2EHPA), while used in ~ome uranium plants on acid leach liguors, typically have high ~olubility and a tendency to form emulsions. It is not believed that liguid ca~ion exchangers have previously been used on carbonate leach liguors.
It should be noted at this point that, through-out the application herein, the term "adsorption" is used to refer both to processes of ion exchange which occur at surface of ion exchange resins and ~o those processes which occur throughout the entire resin stxuc-ture. By using the t.erm adsorption in this application, including ~he c]Laims herein, applicants do not intend to limit the claims to processes or apparatus involving surface actions on ion exchange resins .

~, .~ , ,~

While the above-noted problems occur when prior art leaching methods wi~h sulfuric, hydrochloric, or nitric acid are u~ed, leaching wi~h hydrochloric or nitric acid has particular drawbacks. Cation exchange ~echniques on chloride ~olution~ usin~ Amberlite*I~C 50 are discussed in ~he U. S. Atomic Energy Commission Report ~MO 2502 (now declassi~ied~ for July 1, 1~51 throush August 1, 1951, and disadvantages with increased chloride concen-~ration and the addition of calcium were reported.
Furthermore, anion exchange does not e~ficiently remove uranium from hydrochloric or nitric acid leach liguors.
In hydrochloric acid ~olutions the uranyl cation forms anionic complexes but these are much weaker complexes than those formed with the iron, zinc, and other ca~ions that are present in the ~olution. Th~refoxe, anion ex-change will not be sufficiently selective on the hydro-chloric leach liguor ~o efficiently remove uranium.
Also, anion exchange will not remove uranium from nitric acid le.ach liquors because ~he uranyl cation, U02+2, does not form anio~ic complexes wi~h nitrates.
Sulfuric, hydrochlori~ or nitric acid leaching agents cannot be u~ed economically with ores having a high limestone content. In such cases, leachi~g of ~he uranium can be achieved on the alkaline ~ide with a 601u-tion of sodium or ammonium carbonate and/or bicarbonate,or even with caxbon dioxide ~olutions. It i5 the product of that leaching process that ~he present invention is directed toward treating. For the purposes of this description and the claim~ herein, the phrase "carbonate solution" is used in a broad ~ense to include at least the l~ach liquor produced by sodium or ammonium ~arbonate and/or bicarbonate or by a carbon dioxide ~olution.
Such a ~arbonate solution pxobably contains complex carbonat:e ions, and it is believed that ~he ionic ~pecies are governed by the ~ollowing e~uilibrium reaction although the u~clerlying processes are not fully understood:

*Trade Mark U2 ~2 + ~ CO3 ~ )n ~ [U2 ( C3 ~n] ~
Prob~bly the mos~ common anionic comple~ presen~ is [U~2 (~3~]
~o that the uranyl carbonate anion complex i~ probably 5 in e~ilibrium with ~e uranyl c~tion as :Eollows:
~02~2 ~ 2 ( CO3 ) ~ [UO~ ( CO3 );2 ~ 2 Accoxding to prior art methods, ~uch as dis-closed in Kunin, lo~ cl~ ~ins (1972) a~ pages 195 97, the uranilam can be recovered from the carb~nate 10 olution in ~;ever~l ways. First, alkali could be added ~o precipitate Na2U2O7 . The filtra te from t;his precipi-tation would be recarbonated with carbon dioxide for reuse in leaching more ore. Second, the carbsna~e ~olu-~ion could be acidified with hydrochloric acid and boiled 15 to remove carbon dioxide, with uranium precipitated as the hydroxide ~y adjusting the pE to neutralltyO Last~
it appears tha~ anion exchan~e cQuld opera~e on ~e anionic uranium complex ~o recover the uranium. Ion exchange recovexy is par~iculaxly useful when the digested pulp presents difficult filtration problems. Since many carbonate ores contain bentoni~e clay, filkration is often difficult, leaving ion exchange Gn the unclarified pulp as the most attractive prior art method in such a situation.
Known prior art methods of recovering uranium from carbo~ate leach li~uors utilized anion exchange, even though cation exchange was c~nsidered a possibility for tIeating chlo~ide leach li~uor~, and a highly selec-tive cation exchange resin might remove uranium ~rom a sulfate leach li~uor. Such anion exchange processes for removal o~ uranium from carbonate leach liquors are discussed in U.S. Patent No. 4,155,982 (~unkin et al.), U.5. Patent No~ 2,982,605 (~oure~ et ~ U.S. Patent No. 2,811,412 (Poiri~r), U.S. Patent No. 2,780,514 (Lutz) an~ Merrit, The Extr~ct~we P~t~llur~y of Uranium 151-56 and 16~ 3 ~7~ ve~ ly~ um and vanadî~, ~6--often present in carbonate leach solutions, are also adsorbed in ~ndesirable quantities by ~he anion exchange resin, as discus~ed above. Prior to the presen~ inven-tion, it was ~ot con~idered feasible to use a cation exchange pxocess on carbonate leach solutions containing uranium, because of the relative:ly high level of cations ~hat would be separated from solution along with ~he uranium ju~t as when cation exchange processes ~re used on sulfuric, hydrochloric or nitric acid leach ~olutions.

SVMP~RY OF THE I~ ~NTION
According to ~he present invention, and in contrast wi~h the prior art us~d on carbonate leach ~olu-tions containing uranium ions, a cation exchange process is used. A carbonate ~olu~ion containing uranium ions is caused to contact a weakly acidic cation exchanger whereby uranyl cations are removed. This removal of uranyl cations drives the aforementioned equilibrium equation to the left, thereby producing more uranyl cations for re~oval by cation exchange.
An added advantage of using a cation exchanger according to ~he presen~ inv~ntion is ~he formation of more uranyl cations by removal of carbonate ana bicar bonate ions through ~he cation exchange process. This further increases the concentration of uram um in the cation resin, and is demonstrated in the reaction set forth below:
2RCOOH ~ Na2C03 ~ 2RCOONa ~ CO~ ~ H20 2RCOOH + Ca(HC03~2~ (RC00)2~a + 2C02 ~ 2H2 in which 2RCOOH represents a carboxylic ac.id cation exchange resin.
In summary, then, according to the present inven-tion, there is provided a process for recoveri.ng uranium from a carbonate solution including uranium ions comprising, first, causing the carbonate solution including uranium ions to come in contact with a carboxylic acid ca-tion exchange resin so that the uranium cations are removed from solution and adsorbed 3~3 by the resin, and second, removing the uranium cations from the cation exchange resin. The preferred form of cation exchanger is a carboxylic acid cation exchange resin. The preferred method of removing the uranium cation from the cation exchange resin is by elution with a mineral acid such as hydrochloric acid. The uranium ion is then removed from the uranium solution by precipitation or contact with an anion exchange resin. According to a further emeodiment of the process of the invention, carbon dioxide is removed from the treat:ed carbonate solution produced by the cation exchange resin unit to leave a decarbonated solution, and the decarbonated solution is passed througha membrane to remove some of the remaining impurities. A suitable membrane process to restore the decarbonated, uranium~free solutions to acceptable environ-mental levels is either reverse osmosis or electrodialysis.
According to the apparatus of the invention there is provided an apparatus for recovering uranium from a carbonate solution containing uranium ions com-prising a cation exchange unit, a uranium precipitation vessel connected to the cation exchange unit, a decar-bonator for receiving effluent from the cation exchange resin unit, and a membrane process unit for treating effluent from the decarbonator. In some instances the decarbonator or membrane unit could be eliminated. The preferred form of cation exchangeris a weakly acidic cation exchange resin in the hydrogen form.
Thus, broadly, the inventive apparatus for recovering uranium from a carbonate solution containing uranium ions comprises a cation exchange unit, a uranium precipitation vessel connected to the cation exchange unit, a decarbonator for receiving effluent from the cation exchange unit, and a membrane process unit for treating effluent from the decarbonator.
The apparatus and method of the present invention for recovery of uranium from a carbonate and/or bicarbonate solution produces at least the following advantages and benefits. First, recovery of uranium by ~8--removal of cationic species produces an ideal feed for rever~e osmosis apparatus. Calcium is removed and car-bonate reduced. This is especially impoxtant when it is desirable to restore the trea-ted carbonate solution (with uranium and other cations removed) to a low enough level of impurities ~or return tc) the groundwater. The reverse osmosis processes could t:hen work primarily on the remaining impurities left in the treated carbonate ~olution without scaling or fouli.ng of the m~embrane.
Such an improved feed :reguires fe~wer chemical agents, including acid and anti-~calants.
Second, since the uranium is recovered as the alkalinity i8 removed, ~e overall salirli~y of the car-bonate solution is reduced. It may be possible, through a recycle procedure~ to reduce the effluent ~arbonate solution from a cation exchange process to accept~ble levels of impurities for return to ~he groundwater, without reverse osmosis, electrodialysis, or other post-ion exchange txeatment.
Third, since many carbonate leach solutions contain vanadiwm and molybdenum present as anions, the use of anion exchange resins for xecovering uranium yields yellow cakes c:ontaminated with objectionable guantities of vanadium and molybdenum. However, since the vanadium and molybdenum are present as very stable anions, the weakly aci~ic cation exchange resins of the preferred embodiment of the presen~ invention cannot adsorb the molybdenum and vanadium, and therefore the apparatus and process of the present ~nvention yield a 3~ very pure yellow cake uranium product free of objection-able vanadium and molybdenum.
Four~h, because of the unusual propertie~ of the wealcly acidic cation exchange resin, an acid eluate obtained during regenexation with acid, such a6 hydro-chloric acid, ccm be recycled ~everal times af~ex re~fortificatioIl wi.th acid b~fore precipating the uranium.
This procedure will yield a higher uranium eluate con centration, a hi.gher waste concentra~ion, and a lower waste volume, making for a more ef~icient recovery and ~0 an environmentally acceptable sy~tem.
Fifth, a weakly acidic cation exchange resin will also remove~ ~races of radium in the influent carbonate . ., ~ .

leach solution, and al60 ~hould remove barium which fouls reverse os:nosis membranes.
Sixth, the apparatus and process of the present invention is a distinct advantage! over lime sof~ening 5 and reverse osmosi~ processes typic lly used in ~he prior ~rt to restore waste solutions from which uxanium has been removed. Lime ~ofter~ g i~ disadvantageous because large quantities o~ chemicals are~ required and relatively large volumes of waste are produced. The present inven-10 tion overcomes the disadvantages of lime softerling andsubseguent precipitate removal because th~3 present inven-tion yields a much purer yellow cake t~an through lime softening processes alone.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description of the preferred embodiment in conjunc-~ion with the drawing, which illustrates generally, in schematic form, ~he apparatus of the present invention suitab~e for carrying out recovery of uranium from carbon-ate sslutions by means of a cation exchange unit, decar-bonator, a membrane process, such as reverse osmosis or electrodialysis, and a urani~m recovery vessel for removal of uranium by precipitation or ion exchange.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawing, ~he apparatus of the preferred embodiment of the present invention comprises a cation exchange unit, including a service tank 10, a regeneration tank 12, and a wash tank 14; a decarbonator 110; a membrane process unit 120; and a uranium recovery unit 130. The sizes of the tanks andother units on the drawing is not necessarily the rela-tive size of ~le apparatUs in practice, as their relative size is adapted to the capacities re~uired for service, regeneration, washing, decarbonation, membrane process, and uranium precipitation.

3`

The cation exchange unit can be of the fixed bed type or of the continuous countercurrent ion exchange type~
such as disclosed in U.S. Patent No. 3,595,784, assigned to the assignee herein. The discussion herein of the cation exchange unit is adapted from the disclosure of that patent.
The ion exchange resin used he:rein is preferably a weakly acidic cation exchanc~e resin. Although various weakly acidic cation exchangers such as the alumino-silicates (gels and molecular sieve zeolites) or liquid cation exchangers such as perfluorooctanoic acid and di-2~ethylhexylphosphoric acid (D2EHPA) could be used by one of ordinary skill in the art, the pre-ferred cation exchanger is a resin because inorganic zeolites would not be stable under the conditions of the uranium recovery process herein. The preferred forms of cation exchange resins are carboxylic acid resins such as those based on methacrylic acid divinylbenzene (DVB) and hydrolyzed methyl or ethyl acrylate divinylbenzene (DVB) copolymers. Crosslinked copolymers based upon maleic and resorcylic acids could also be used, with acrylic polymers preferred.
Examples of suitable cationic resins in the methacrylic acid/DVB type are: ~nberlite* IRC-50 from Rohm & ~.aas Co., Ionac* CC from Ionac Co., and Duolite*
C-464 from Diamond Shamrock Co. Suitable cationic resins in the hydrolyzed acrylatetDVB ester type are: Amberlite~
IRC-84 from Rohm and Haas Co., Ionac* CNN from Ionac Co., Dowex* CCR-2 from Dow Chemical Co., and Duolite* C-433 from Diamond Shamrock Co. Also the ion exchange resin is preferably in bead Eorm. Fluid beds or fixed beds of such resin may be used, as is known by those of ordinary skill.
The cation exchange apparatus will now be dis-cussed in greater detail. According to the preferred embodiment, a regenerated resin reservoir 16 communi-cates with an upper portion of the service tank 10 *Trade Marks ;i3 ~11~

through a xesin conduit 18 having a transfer valve 20.
Similarly, the regeneration tank 12 has an exhausted resin reservoir 22 communicating with an upper portion thereof ~hrough a resin conduit 24 having a transfer valve 26. Finally, ~he wash tank 14 has a metering reservoir 28 c~mmunicatin~ with cm upper portion ~hereof through a resin conduit 30 havins~ a valve 32. As with the tanks 10 r 12, and 14, the reservoirs ~6, 2~, and 28 will not necessarily be the same size. Resin ~ransfer conduits 34 are connected to permit the transfer of resin from a lower portion of the service tank 10 to ~he exhausted re~in reservoir 22, from a lower portion o~ the regener~tion tank 12 to the metering re~ervoir 28, and from a lower por~ion of the wash tank 14 to ~he regenerated resin reservoir 16. Although ~he preferred e~bodiment ~hows ~hree tanks 10, 12, and 14 for efficient ~ervice cycle operation, f wer ~anks may be used.
Also, instead of using one service tank for cation exchange, more ~han one ~rvice tank in s~ries may be used as is ~nown in the art. Such a dual service tank system may be desirable when the influent ~olution to the first service tank contains large amounts of non uranium cations that ~ould compete for adso~ption on the cation exchange resin. Uranium ~hat would leak from the first tank prior to saturation of the cation exchange resin in ~he first tank would be adsorbed in the second tank.
In operation, the carbonate solution contain-ing uranium ions is delivered to the service tank 10 through a ~ervice inlet 36 having a service inlet valve 38, and the treated carbonate solution with a major por tion of the uranium ions removed is withdrawn at a ser-vice outlet line 40 having a service outlet valve 42.
A drain line 50 having a drain valve 52 communicates with the service tank 10 at a lower portion.
During operation, the service tank 10 is inter-nally pressuriæed, and has a major portion of ~he resin compacted in an area above the level of the service inlet line 36. ~ void zone, containing li~uid only, is formed between the service inlet line 36 and an area just above the ~ot~om of the ~ank 10, where there is also some com-5 pacted resin. As it periodically becomes necessary to rPplace a portion of the exhausted resin in the ~ervice tank 10 with fresh re~in from the regenerated resin reservoir 16, the service inlet valve 38 and service outlet valve 42 are closed, and l~e drain valve 52 is opened, depressurizing ~he tank 10. The transfer valve 20 is opened, and the bed of re~in flows downwardly under the influence of gravityO Additional resin flows in from the regenerated resin reservoir 16 as a result of the opening of the transfer valve 20. ~fter sufficient resin has entered the tank 10, ~he drain valve 52 and transfer valve 20 are closed, and the tank 10 is pres-surized by again opening th~ service inlet valve 3~ and the outlet valve 42. The repressurization compacts ~he bed, and again produces a void zone below the inlet line 36, forcing a portion of the e~hausted resin through the ~ransfer conduit 34 to ~he exhausted resin reservoir 22.
The regeneration tank 12 is the site of ~his elution of the uranium ions from the cation exchange resin to form a solution containing uranium ions at a greater concentration than that of ~he in~luent carbon-ate solution. The regeneration tank 12 has an upper liquid outl~t line 60, a regenerant inlet line 78 below the outlet line 60, and preferably near the midpoint of the tank 12l and a separation liquid inlet line 90 com-municating with the tank 12 below the regenerant inlet line -l8 at a poi.nt above the bottom of the tank 12.
Near the ~ottom of ~ank 12 and below the ~eparatio~
liguid inlet line 90 a drain line 66 having a drain valve 68 communicates wi~h the tank 12. As shown in the drawing, the upper liguid outlet line 60 has an outlet valve 70 located thereon, and the separation ligui.d inle~ line 90 has a valve g2 located ~hereon.

In ~he wash tank 14, final cleansing of ~he resin is preferably carried out on a fluidized bed prin ciple. The wa~h tank 14 has a cleansing liguid inlet line 94 and a cleansing liquid outlet 96, each ha~ing valve~ desigaated re pectively by reference numerals 98 and 100.
- In operation, during the reyeneration of resin and elutlon of uranium ions from ~he cation exchange resin, all valves on lines leading to ~he regeneration tank 1~ are closed except for the outlet valve 70, ~he valve 82 on the regenerant inl~t line 78, and the valve 92 on the separation liquid inlet line 90. In addition, the valve 32 on the resin conduit 30 below the metering reservoir 28 is closed. The separation li~uid is de-livered under sufficient pressure to maintain the resinin the tank 12 packed a~o~e the level of the separation liquid inlet line 90, &0 that a void zone, containing primarily li~uid, is pre~ent below this inlet line 90.
Some additional resin will also normally be present in ~he bottom of the tank 12. This resin is prevented from leaving the tank 12 ~ince the metering reservoir 28, as well as the transfer conduit 34 between the metering reservoir 28 and ~he reseneration tank 12, are filled with a slurry of resin.
As the separation liquid, which will ordinarily be water, travels upwardly, it mixes with the regenerant being intxoduced at the regenerant inlet line 78. In the preferred embodiment of the present invention, ~he regenerant i~ a mineral acid, such as hydrochloric acid.
Other suitable mineral acids ~re nitric acid and ~ulfuric acid. The mineral acid both regenerates the cation ex-change resin and elutes the uranium, as U02 +2 or [U2 ~2 (C13)] , when hydrochloric acid is used. Both the regenerant and ~.paration liquid are withdrawm from the tank 12 at the upper liguid outlet line 60. Therefore, the upper liguid outlet line ~0 contains a solution hav-ing a greater uranium ion concentration than that of the influent carbonate solution in ~he inlet line 36, making the uranium ion 601ution in ~he upper liquid out~
let line 60 ~uitable for removal of the uranium by pre~
cipitation or anion exchange. The eluant can al50 be 5 recycled through the regeneration tank 12, instead of eluting with fresh mineral acid, until ~he desired con centration of uranium ion in the eluant is obtained.
Below the separation li~uid inlet line 90, ~here will be rPlatively little u.pward flow. The small amount of upward flow that does exist will be produced by liguid ~hat enters the tank 12 from a pu~hwater pipe 102, which communicates with ~he resin transfer conduit 34 just below the regeneration tank 12. It is the func-tion of this pushwater pipe 102 to aid in the transfer of resin between the regenera~ion tank 1~ and the meter-ing reservoir 2B as described herein.
Periodically, a portion of ~Islug~ of regener-ated resin is removed from the regeneration tank 12 and transferred to the metering res~rvoir 28. To initiate this cycle, the valves 70, 82, 92 on the outlet line 60, the regenerant inlet line 78, and the ~eparation liguid inlet line 90 are ~losed, shu~ting off flow within the tank 12. The drain valve 68 and ~he tran~fer valve 26 are then opened, depressurizing the tank. Exhausted resin from the reservoir 22 flows into the tank 12 under the influence of gravity. At the same time, ~he valve 32 below ~he metering reservoir 28 is opened, allowing resin to flow from the metering reservoir 2B into the wash tank 14.
After the tank 12 has been nearly completely filled with loose resin, the repxessurization step is initiated. The drain valve 6B and transfer valve 26 a.re closed, and the valves 70, B2, 92 on the outlet line 60, the inlet line 78, and the separation liquid inlet line 90 are again opened. The valve 32 below the meter~
ing reservoir ~ is closed, halting the flow of resin into the wash tank 14.

~15 Washed resin from ~he wash tank 14 is trans-ferred at various tim2s ~hrough the transfer line 34 to the regenerated r~sin reservoir 16. Primary effluent 6treams fxom the cation exchange apparatus described above are thus the treated carbonate solution in service outlet line 40 (that is, ~i~h uranium and other cations removed) and ~he concentrated uranium ion ~olu~ion in outlet line 60. In order to accomplish recovery of the urani~n removed from ~he carbonate solution, the concen-trated uranium ion ~olution is passed through line 74and pumped by transfer pwmp 133 into ~he uxanium recovery vessel 130.
In one form of the present inven~ion, uranium is precipita~ed by adding the ammonium ion via NH3 until a pH of 6.8 to 7.0 is r~achedO As discussed in Kunin, El ~ (1971) at pages 108-09, the precipitation can also be accomplished by adding either NaO~ or MgO. The precipitat~ may be thought of as diuranate, Na2U207 . xH~O, although some UO3 . xH~O is also present. The precipitated uranium is then filtered, dried or calcined, and i~ then shipped as "yellow cake"
~eed material for uranium refineries.
Alternatively, the hydrochloric acid eluate containing the uxanium may be furthex concentrated and purified by passage through any of a number o~ anion exchange resins, ~trongly and weakly basic, such as Amberlite*IRA-400 from Rohm and ~aas Co., Dowex*21K from Dow Chemical Co., and Amberlite*IRA-93 from Rohm and Haas Co. The uranium is then elu~ed from ~he anion ex-change resin wi~:h water to form a solution irom whichthe uranium may be precipitated with an alkaline reasent, such as ammonia or sodium hydroxide, or with hydrogen peroxide.
The treated carbonate solution contains other ions, as noted ~o~e, such as vanadium, molybdenum, as well as .resicLual amounts o~ sodium and magnesium.
If it is necessary or desirable in the uranium leaching system to restore the treated *Trade Marks ;3~aS3 carbonate ~olution to acceptable original groundwater levels~ then additional filtration and trea~ment may be required. According to the prefexred e~bodiment of ~he present invention, thi~ tre~tment. is accomplished in a decarbonator unit 110 and a membrane process unit 120.
When the outlet valve 42 is open, treated caxbonate solution passes into the decarbonator unit 110 through transfer line 104, where under a process as known in ~he art, C02 is released. One such suitable decarbon-ator is disclosed in U.S. Patent NG. 2,807,582 ~Applebaum~.Suitable gas influent can be added ~hrough the conduit 112 by opening the valve 111 to release C02 from solution.
The C02 is vented through the vent 143.
The effluent of the decarbcnator 110 is then transferred through ~he transfer line 106 to ~he membrane process unit 120 to remove remainin~ ions, by opening valves 113 and 118 and operating pump 116. ~s is known in the art, the membxane process unit can ~e operated at a rate sufficien~ to accomplish desired removal of remaining salts, and other cations and anions generally.
The membrane process unit 120 may be a reverse o~mosis unit, or may be an electrodialy~is unit. Th~ preferred form is a reverse osmosis uni~, ~ontaining a known semi-permeable membrane. Other ~uitable membxane processes will be apparent to those of ordinary ~kill. The effluent from the membrane process unit 120 ~hen consists of two forms, released selectively by valves 126 and 122, respec-tively, when valve llB is opened. These effluents are purified water in outlet line 128, suitable for xeturn to the groundwater, and a waste stream in outlet line 124 for disposal.
Of course, it should be understood that modi-fications and changes to the preferred embodiments dis-closed herein may be apparent to those of ordinaxy skill in the art without departiny from the spirit and scope of the present invention, and without diminishing its attendant advantages. It is therefore intended ~hat all such modifications and changes be ::overed by the following claims.

Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for recovering uranium from a carbonate solution including uranium ions, the process comprising:
causing the carbonate solution including uranium ions to come in contact with a carboxylic acid cation exchange resin so that uranium cations are removed from solution and adsorbed by said resin; and removing the uranium cations from the cation exchange resin.

2. The uranium recovery process of Claim 1 wherein uranium cations are removed from the carboxylic acid cation exchange resin by elution with hydrochloric acid.

3. A process for recovering uranium from a carbonate solution including uranium ions, the process comprising:
causing the carbonate solution including uranium ions to come in contact with a carboxylic acid cation exchange resin so that uranium cations are removed from solution and adsorbed into the cation exchange resin;
removing the uranium cations from the cation exchange resin to produce a uranium solution; and eluting said uranium cations from the uranium solution.

4. The process of Claim 1 wherein said carboxylic acid cation exchange resin is methacrylic acid divinyl-benzene copolymer or hydrolyzed methyl acrylate divinylbenzene copolymer or hydrolyzed ethyl acrylate divinylbenzene co-polymer.

5. The process of Claim 1 wherein said carboxylic acid cation exchange resin is selected from the group consisting essentially of methacrylic acid divinylbenzene copolymer, hydrolyzed methyl acrylate divinylbenzene copolymer, and hydrolyzed ethyl acrylate divinylbenzene copolymer.

6. A process for recovering uranium from a carbonate solution including uranium ions, which process comprises:
contacting the carbonate solution including uranium ions with a weakly acidic carboxylic acid cation exchange resin selected from the group consisting essentially of methacrylic acid divinylbenzene copolymer, hydrolyzed methyl acrylate divinylbenzene copolymer, and hydrolyzed ethyl acrylate divinylbenzene copolymer to remove uranium cations from solution and to adsorb the uranium cations into said carboxylic acid cation exchange resin, and to produce a treated carbonate solution;
eluting the uranium cations from said carboxylic acid cation exchange resin with hydrochloric acid to produce a uranium cation solution;
selectively precipitating said uranium cations from solution with ammonium ions;
decarbonating said treated carbonate solution; and filtering said decarbonated solution to remove remaining impurities.

7. The uranium recovery process of Claim 3 wherein the step of removing uranium ions from solution is accom-plished by adding ammonium ions to the uranium ion solution so that a uranium precipitate is formed.

8. A process for recovering uranium from a carbonate solution including uranium ions, the process comprising:
causing the carbonate solution including uranium ions to come in contact with a weakly acidic carboxylic acid cation exchange resin so that uranium cations are removed from solution and adsorbed into the cation exchange resin, and a treated carbonate solution is produced;
eluting the uranium cations from the cation ex-change resin to produce a uranium ion solution;
removing uranium ions from the solution by selective precipitation and removing carbon dioxide from the treated car-bonate solution to produce a decarbonated solution.

9. The uranium recovery process of Claim 8 further including the step of filtering the decarbonated solution through a membrane process.

10. The uranium recovery process of Claim 9 wherein the membrane process is reverse osmosis.

11. The uranium recovery process of Claim 9 wherein the membrane process is electrodialysis.

12. A process for recovering uranium from a carbonate solution including uranium ions, which process comprises:
contacting the carbonate solution including uranium ions with a weakly acidic carboxylic acid cation exchange resin to remove uranium cations from solution and to adsorb the uranium cations into said carboxylic acid cation exchange resin, and to produce a treated carbonate solution;
eluting the uranium cations from said carboxylic acid cation exchange resin with hydrochloric acid to produce a uranium cation solution;
selectively precipitating said uranium cations from solution with ammonium ions;
decarbonating said treated carbonate solution; and filtering said decarbonated solution to remove remaining impurities.

13. Apparatus for recovering uranium from a carbonate solution containing uranium ions comprising:
cation exchange means for removing a uranium cation from solution and adsorbing the uranium cation into a cation exchange resin so that a treated carbonate solution is produced;
means for eluting the uranium cation from the cation exchange resin to produce a uranium solution;
means for recovering the uranium ion from the uranium solution;
means for decarbonating the treated carbonate solution; and membrane process means for removing impurities from the decarbonated solution.

14. Apparatus for recovering uranium from a car-bonate solution containing uranium ions comprising.
a cation exchange unit;
a uranium precipitation vessel connected to the cation exchange unit;
a decarbonator for receiving effluent from the cation exchange unit; and a membrane process unit for treating effluent from the decarbonator.

15. Apparatus for recovering uranium from a car-bonate solution containing uranium ions comprising:
weakly acidic cation exchange resin in the hydrogen form;
a cation exchange resin unit including at least two columns for containing the weakly acidic cation ex-change resin;
a uranium precipitation vessel connected to the cation exchange resin unit;
a decarbonator connected to the cation exchange resin unit; and an electrodialysis apparatus for treating effluent from the decarbonator.