CA1203387A - Rejuvenation of the anion exchanger used for uranium recovery - Google Patents
Rejuvenation of the anion exchanger used for uranium recoveryInfo
- Publication number
- CA1203387A CA1203387A CA000419652A CA419652A CA1203387A CA 1203387 A CA1203387 A CA 1203387A CA 000419652 A CA000419652 A CA 000419652A CA 419652 A CA419652 A CA 419652A CA 1203387 A CA1203387 A CA 1203387A
- Authority
- CA
- Canada
- Prior art keywords
- resin
- uranium
- solution
- exchange capacity
- ion exchange
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Manufacture And Refinement Of Metals (AREA)
Abstract
REJUVENATION OF THE ANION EXCHANGER
USED FOR URANIUM RECOVERY
ABSTRACT
A process is described for restoring and maintaining the total ion exchange capacity of the resin used for uranium recovery in in situ uranium leaching. The used resin of lowered exchange capacity is treated with a solution containing Na2CO3 or NaHCO3, or admixtures thereof. The process preferably is used in conjunction with acid elution of the uranium from the resin.
USED FOR URANIUM RECOVERY
ABSTRACT
A process is described for restoring and maintaining the total ion exchange capacity of the resin used for uranium recovery in in situ uranium leaching. The used resin of lowered exchange capacity is treated with a solution containing Na2CO3 or NaHCO3, or admixtures thereof. The process preferably is used in conjunction with acid elution of the uranium from the resin.
Description
33~
REJUVENATION OF THE ANION EXCHANGER
USED FOR U M NIUM RECOVERY
This invention relates generally to the recovery of mineral values, in particular uranium, from leachates produced during leaching operations in subterranean formations. More specifically, this invention provides processes for rejuvenating anion exchange resins which are used to concentrate the uranium from the leachate and which become at least partially spent during continuous or repe-titive use.
In situ leaching operations for recovering uranium from formations involve oxidizing the insoluble tetravalent uranium to its hexavalent form and solubilizing it. For example9 CO2/02 leaching solutions, which are often used for in situ leaching operations, result in oxidation U2 + ~] ~ H20 -~ U02~2 ~ 2 OH
and in ~ormation of a soluble uranyl carbonate complex, U2 +3 CO3 = ~ uo2(co~)3 ~4 Practically, one embodiment of the CO2/02 leaching solution involves injecting a solution of CO2 and 2 through at least one injecton well into the subterranean formation, allowing leachin~ to occur, and then pumping the leachate pregnant in uranium in the form of a soluble uranyl complex from the formation through a production well.
The leachate contains other mineral values in addition to the uranium. Ion exchanye techniques are now commercially used to recover, concentrate, and selectively isolate uranium. Such ion exchange techniques depend on the existence of anionic complexes of uranium in solution which, under proper conditions, are selectively adsorbed from a leachate by suitable synthetic resins. As suggested above, the complex anion of uranium, produced during CO2/02 ~3~
leaching, is the tetravalent uranyl tricarbonate anîon, [U02(C03)3] 4, which predominates although a divalent ion, [U02(C03)2.2 H2D] may exist at low carbonate concentrations. Generally, the adsorp~ion of the tetravalent uranyl tricarbonate anion, by ion exchange, is accomplished by use of strong base anionic exchange resins. The strong base anionic exchange resins contain quaternary ammonium functional groups as the active anion constituent. Some are made by the chloromethylation of polystyrene and subsequent treatment with a tertiary amine. Pyridinum groups may be substituted in part for the amine groups in some resins developed specifically for uranium recovery. ~he strong base anionic resins are highly ionized, usable over a wide pH range, stable in the absence of strong reducing or o~idizing agents, insoluble in most of the common solvents and will ~ithstand temperatures up to about 60C.
Notwithstanding the aforementioned properties of those resins, the performance of strong base anionic exchange resin ~eteriorates during usage, due to the repeated conditions of loading (adsorption), elution and poisoning. Performance deterioration of the resin is manifested by a decrease in loading capacity and early uraniurn "leakage." Performance deterioration may be irreversible if due to complete and actual removal of at least some of the active ion grops, but reversible if due to constructive removal of those active ion groups which form strong physical or chemical bonds with poisons and fouling agents.
The present invention is directed to improving the performance o~ strong base anionic exchange resins used in uranium recovery and which exhibit an undesirable decrease in loading capacity (early uranium leakage) and in total exchange capacity. Total exchange capacity of a resin is usually expressed as either milliequivalents per gram of anhydrous resin or per milliliter of water~swollen resinO Dowex 21K (trademark of Dow Chemical), a typical resin used in uranium recovery has a dry capacity of 4.5 milliequivalents per gram and a wet capacity of 1 25 milliequivalents per milliliter. Deterioration in performance, referred to above, involves a decrease in this total capacity of the resin.
~33~
F~0~4~ ~3~
The invention comprises treating a strong base anionic exchange resin exhibiting performance deterioration to remove physically adsorbed and occluded fouling agents and to remove poisons which may be chemically bound to active ion groups on the resin. The process of the invention involves treating the resin, after the uranium ion exchange stage, with an alkaline carbonate solution.
Preferably, the process involves treating the resin with an acid eluant prior to treating the resin with the alkaline carbona-te solution. It is believed that after resin has been used to recover uranium from a C02/02 leachate, the acid treatment dissolves insoluble fouling agents which are physically occluded or adsorbed by the resin and that the weak base treatment augments that result and probably removes poisons which are pysically or chemically bound to the resin.
In a preferred embodiment of the invention, the acid treatrnent of the strong base anion exchange, hereinafter referred to as "acid elution," precedes the weak base treatment of the resin. By way of illustration, it is this embodiment which will be discussed below. In this embodiment, the strong base anionic change may be loaded with uranium as at the end of the loading cycle.
In the pre~erred embodiment, the first stage of the invention process is an acid elution of the resin. In the acid elution, sufficient acid is passed over the resin to dissolve uranium in the form of uranyl carbonate anion complexes, CaC03 (calcite, which is removed from the subterranean formation and dissolved in the leachate during the leaching operation) and other foreign matter which is, or becomes, soluble in acid. Preferably, the acid eluant is HCl (and NaCl) so as to keep the resin free from calcite plugging. In one test the eluant contained 6 9/l NaCl and l.û N HCl. The acid elution restores the loading characteristics of the resin or, in other words, decreases uranium leakage. Such regeneration, it is believed9 is due to dissolution of calcite and other foreign matter9 resulting in improved diffusivity.
~ g .r ~
3~ ~
F-08~2 -4-Prior to this invention, it was suggested by others to elute with an alkaline carbonate solution of NaC1 60 9/1, NaHC03 5 9/1 and Na2CG3 5 9/1. However, as shown hereinafter use of an eluant oF
NaCl and HCl provides superior results.
After acid elution9 the eluted resin is treated by contact with an alkaline carbonate solution for a period of tirne sufficient to substantially restore the resin to its original total ion exchange capacity. Change in, and thus restoration of, total ion capacity can be measured by conventional acid/base titration. Typically, a carbonate solution, used in this stage, will contain both NaHC0~ and Na2C0~; each of which may be present in an amount ranging from 0.5 9/l to lOû 9~1. The time period of treatment can range from about O.S
to 100 hours. In a specific run, a resin having a total capacity of 1.4 meg/cc but which had deteriorated to 0.5 meg/cc was acid eluted.
Total ion exchange capacity was then restored when the resin was contacted with a solution containing 5 9/1 Na2C03 and 5 9/1 NaHC03 for six (6) hours.
Contact between the resin and the carbonate solution can be effected by soaking or, preferably, by continued washing. To conserve the solution, the rate of wash can be kept low, at about 0.05 to 5 cc of solution per cc of resin per hour.
The table set forth below reports data showing substantial restoration of the total resin capacity by acid elution and carbonate ~reatment of a resin exhibiting deteriorated loading capacity.
33g~ ~
f~-08~ ~5~
Treatrnent of Field Loaded Resins to Remove Poisons and Restore Exchange Capacity Run No. 802 804 Resin Source* IX-l, containing Acid washed, field CaC03, crushed loaded Elution NaCl: 6 g/l NaCl: 60 9/1 HCl: 1.0 N NaHC03: 5 9/1 ~a2C03: 5 9/
Treatment Na2C03: 20 g/l 5% NaOH
NaHC03: 20 g/l 24 hours 4 days a ~
meg/cc 0.92 0.82 * The resins used in Runs 802 and 804 were sold commercially under the trademark IRA 430 by Rohm and Haas Co.
The acid eluted resin which has not been subjected to treatment with the carbonate solution, in accordance with the process of the invention appears to contain poisons which lower the total capacity of the resin greatly, sometimes by as much as two-thirds.
Cecause oP this great reduction in the total capacity of the resin, it is believed that such poisons are more than physically adsorbed by the resin. Rather, the poisons can be anionic species which are strongly exchanged on the resin. Moreover, it is believed that such poisonous anions are uranyl chloride anions, U02C14 2, which are known to poison the resins. Thus, one theory of explaining the efficiency of the invention in restoring the total ion exchange capacity to the resin is that such a uranyl chloride resin is decomposed by the use of the carbonate solution, according to equilibrium er~uations (1~ and (2):
U02C14 ~ U2 ~+ + 4 Cl- (1) ~J2 + 3 C03 ~ U02(Co3)3 4 (2) ~33 F -oal~2 -6-~rha~ is, the possible explanation is that carbonate, in the carbonate solution, shifts both equilibriums, represented by equations (1) and ~2), to the right with resulting decomposition of U02C14 2.
Applicants, however, do not wish to be bound by this theory7 as it depends on characterization of the material which poisons the resin as necessarily being U02C14 2. However, if this theory is correct, it is clear that the carbonate solution should be free o-f, or substantially free of, chloride ions.
REJUVENATION OF THE ANION EXCHANGER
USED FOR U M NIUM RECOVERY
This invention relates generally to the recovery of mineral values, in particular uranium, from leachates produced during leaching operations in subterranean formations. More specifically, this invention provides processes for rejuvenating anion exchange resins which are used to concentrate the uranium from the leachate and which become at least partially spent during continuous or repe-titive use.
In situ leaching operations for recovering uranium from formations involve oxidizing the insoluble tetravalent uranium to its hexavalent form and solubilizing it. For example9 CO2/02 leaching solutions, which are often used for in situ leaching operations, result in oxidation U2 + ~] ~ H20 -~ U02~2 ~ 2 OH
and in ~ormation of a soluble uranyl carbonate complex, U2 +3 CO3 = ~ uo2(co~)3 ~4 Practically, one embodiment of the CO2/02 leaching solution involves injecting a solution of CO2 and 2 through at least one injecton well into the subterranean formation, allowing leachin~ to occur, and then pumping the leachate pregnant in uranium in the form of a soluble uranyl complex from the formation through a production well.
The leachate contains other mineral values in addition to the uranium. Ion exchanye techniques are now commercially used to recover, concentrate, and selectively isolate uranium. Such ion exchange techniques depend on the existence of anionic complexes of uranium in solution which, under proper conditions, are selectively adsorbed from a leachate by suitable synthetic resins. As suggested above, the complex anion of uranium, produced during CO2/02 ~3~
leaching, is the tetravalent uranyl tricarbonate anîon, [U02(C03)3] 4, which predominates although a divalent ion, [U02(C03)2.2 H2D] may exist at low carbonate concentrations. Generally, the adsorp~ion of the tetravalent uranyl tricarbonate anion, by ion exchange, is accomplished by use of strong base anionic exchange resins. The strong base anionic exchange resins contain quaternary ammonium functional groups as the active anion constituent. Some are made by the chloromethylation of polystyrene and subsequent treatment with a tertiary amine. Pyridinum groups may be substituted in part for the amine groups in some resins developed specifically for uranium recovery. ~he strong base anionic resins are highly ionized, usable over a wide pH range, stable in the absence of strong reducing or o~idizing agents, insoluble in most of the common solvents and will ~ithstand temperatures up to about 60C.
Notwithstanding the aforementioned properties of those resins, the performance of strong base anionic exchange resin ~eteriorates during usage, due to the repeated conditions of loading (adsorption), elution and poisoning. Performance deterioration of the resin is manifested by a decrease in loading capacity and early uraniurn "leakage." Performance deterioration may be irreversible if due to complete and actual removal of at least some of the active ion grops, but reversible if due to constructive removal of those active ion groups which form strong physical or chemical bonds with poisons and fouling agents.
The present invention is directed to improving the performance o~ strong base anionic exchange resins used in uranium recovery and which exhibit an undesirable decrease in loading capacity (early uranium leakage) and in total exchange capacity. Total exchange capacity of a resin is usually expressed as either milliequivalents per gram of anhydrous resin or per milliliter of water~swollen resinO Dowex 21K (trademark of Dow Chemical), a typical resin used in uranium recovery has a dry capacity of 4.5 milliequivalents per gram and a wet capacity of 1 25 milliequivalents per milliliter. Deterioration in performance, referred to above, involves a decrease in this total capacity of the resin.
~33~
F~0~4~ ~3~
The invention comprises treating a strong base anionic exchange resin exhibiting performance deterioration to remove physically adsorbed and occluded fouling agents and to remove poisons which may be chemically bound to active ion groups on the resin. The process of the invention involves treating the resin, after the uranium ion exchange stage, with an alkaline carbonate solution.
Preferably, the process involves treating the resin with an acid eluant prior to treating the resin with the alkaline carbona-te solution. It is believed that after resin has been used to recover uranium from a C02/02 leachate, the acid treatment dissolves insoluble fouling agents which are physically occluded or adsorbed by the resin and that the weak base treatment augments that result and probably removes poisons which are pysically or chemically bound to the resin.
In a preferred embodiment of the invention, the acid treatrnent of the strong base anion exchange, hereinafter referred to as "acid elution," precedes the weak base treatment of the resin. By way of illustration, it is this embodiment which will be discussed below. In this embodiment, the strong base anionic change may be loaded with uranium as at the end of the loading cycle.
In the pre~erred embodiment, the first stage of the invention process is an acid elution of the resin. In the acid elution, sufficient acid is passed over the resin to dissolve uranium in the form of uranyl carbonate anion complexes, CaC03 (calcite, which is removed from the subterranean formation and dissolved in the leachate during the leaching operation) and other foreign matter which is, or becomes, soluble in acid. Preferably, the acid eluant is HCl (and NaCl) so as to keep the resin free from calcite plugging. In one test the eluant contained 6 9/l NaCl and l.û N HCl. The acid elution restores the loading characteristics of the resin or, in other words, decreases uranium leakage. Such regeneration, it is believed9 is due to dissolution of calcite and other foreign matter9 resulting in improved diffusivity.
~ g .r ~
3~ ~
F-08~2 -4-Prior to this invention, it was suggested by others to elute with an alkaline carbonate solution of NaC1 60 9/1, NaHC03 5 9/1 and Na2CG3 5 9/1. However, as shown hereinafter use of an eluant oF
NaCl and HCl provides superior results.
After acid elution9 the eluted resin is treated by contact with an alkaline carbonate solution for a period of tirne sufficient to substantially restore the resin to its original total ion exchange capacity. Change in, and thus restoration of, total ion capacity can be measured by conventional acid/base titration. Typically, a carbonate solution, used in this stage, will contain both NaHC0~ and Na2C0~; each of which may be present in an amount ranging from 0.5 9/l to lOû 9~1. The time period of treatment can range from about O.S
to 100 hours. In a specific run, a resin having a total capacity of 1.4 meg/cc but which had deteriorated to 0.5 meg/cc was acid eluted.
Total ion exchange capacity was then restored when the resin was contacted with a solution containing 5 9/1 Na2C03 and 5 9/1 NaHC03 for six (6) hours.
Contact between the resin and the carbonate solution can be effected by soaking or, preferably, by continued washing. To conserve the solution, the rate of wash can be kept low, at about 0.05 to 5 cc of solution per cc of resin per hour.
The table set forth below reports data showing substantial restoration of the total resin capacity by acid elution and carbonate ~reatment of a resin exhibiting deteriorated loading capacity.
33g~ ~
f~-08~ ~5~
Treatrnent of Field Loaded Resins to Remove Poisons and Restore Exchange Capacity Run No. 802 804 Resin Source* IX-l, containing Acid washed, field CaC03, crushed loaded Elution NaCl: 6 g/l NaCl: 60 9/1 HCl: 1.0 N NaHC03: 5 9/1 ~a2C03: 5 9/
Treatment Na2C03: 20 g/l 5% NaOH
NaHC03: 20 g/l 24 hours 4 days a ~
meg/cc 0.92 0.82 * The resins used in Runs 802 and 804 were sold commercially under the trademark IRA 430 by Rohm and Haas Co.
The acid eluted resin which has not been subjected to treatment with the carbonate solution, in accordance with the process of the invention appears to contain poisons which lower the total capacity of the resin greatly, sometimes by as much as two-thirds.
Cecause oP this great reduction in the total capacity of the resin, it is believed that such poisons are more than physically adsorbed by the resin. Rather, the poisons can be anionic species which are strongly exchanged on the resin. Moreover, it is believed that such poisonous anions are uranyl chloride anions, U02C14 2, which are known to poison the resins. Thus, one theory of explaining the efficiency of the invention in restoring the total ion exchange capacity to the resin is that such a uranyl chloride resin is decomposed by the use of the carbonate solution, according to equilibrium er~uations (1~ and (2):
U02C14 ~ U2 ~+ + 4 Cl- (1) ~J2 + 3 C03 ~ U02(Co3)3 4 (2) ~33 F -oal~2 -6-~rha~ is, the possible explanation is that carbonate, in the carbonate solution, shifts both equilibriums, represented by equations (1) and ~2), to the right with resulting decomposition of U02C14 2.
Applicants, however, do not wish to be bound by this theory7 as it depends on characterization of the material which poisons the resin as necessarily being U02C14 2. However, if this theory is correct, it is clear that the carbonate solution should be free o-f, or substantially free of, chloride ions.
Claims (5)
1. A process for restoring the ion exchange capacity of a strong base anion exchange resin used for recovering uranium, in the form of uranyl carbonate anions, from solutions used to leach uranium from subterranean formations which comprises:
washing the resin with a solution containing 0.5 to 100 grams/liter of sodium carbonate, sodium bicarbonate, or admixtures thereof, for a time sufficient to substantially free the resin of materials which are either soluble in the solution or react with the solution.
washing the resin with a solution containing 0.5 to 100 grams/liter of sodium carbonate, sodium bicarbonate, or admixtures thereof, for a time sufficient to substantially free the resin of materials which are either soluble in the solution or react with the solution.
2. The process of Claim 1, wherein the resin has been used to absorb the uranium prior to the step of washing.
3. The process of Claim 1, wherein prior to the washing step the resin is treated with acid to elute the uranium.
4. Q process for isolating uranium which has been leached from subterranean formations by a leach solution containing carbon dioxide and oxygen wherein the leach solution has been contacted with a strong base anion exchange resin so that uranium contained in the leach solution is exchanged on the resin and for substantially restoring to the resin its original total ion exchange capacity prior to being contacted with the leach solution which comprises:
eluting the resin with hydrochloric acid to remove uranium in the form of uranyl carbonate anions, and contacting the resin with a solution of sodium carbonate, sodium bicarbonate, or admixtures thereof for a time sufficient to substantially restore the total ion exchange capacity.
eluting the resin with hydrochloric acid to remove uranium in the form of uranyl carbonate anions, and contacting the resin with a solution of sodium carbonate, sodium bicarbonate, or admixtures thereof for a time sufficient to substantially restore the total ion exchange capacity.
5. The process of Claim 4, wherein the solution contains 0.5 to 100 grams of sodium carbonate, sodium bicarbonate, or admixtures thereof per liter of solution.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000419652A CA1203387A (en) | 1983-01-18 | 1983-01-18 | Rejuvenation of the anion exchanger used for uranium recovery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000419652A CA1203387A (en) | 1983-01-18 | 1983-01-18 | Rejuvenation of the anion exchanger used for uranium recovery |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1203387A true CA1203387A (en) | 1986-04-22 |
Family
ID=4124367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000419652A Expired CA1203387A (en) | 1983-01-18 | 1983-01-18 | Rejuvenation of the anion exchanger used for uranium recovery |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1203387A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117467862A (en) * | 2023-12-22 | 2024-01-30 | 核工业北京化工冶金研究院 | Method for preventing resin organic matter poisoning in neutral leaching uranium mining hydrometallurgy process |
-
1983
- 1983-01-18 CA CA000419652A patent/CA1203387A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117467862A (en) * | 2023-12-22 | 2024-01-30 | 核工业北京化工冶金研究院 | Method for preventing resin organic matter poisoning in neutral leaching uranium mining hydrometallurgy process |
| CN117467862B (en) * | 2023-12-22 | 2024-03-29 | 核工业北京化工冶金研究院 | Method for preventing resin organic matter poisoning in neutral leaching uranium mining hydrometallurgy process |
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| MKEX | Expiry |