# US 4,391,782 A · In situ uranium leaching using high pressure CO.sub.2 /O.sub.2 system to overcome chloride ion inhibition

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- Number: US 4,391,782 A
- Document ID: US4391782A
- Status: Granted
- Kind: A
- Application number: 06/221,556
- Filed: 1980-12-31
- Granted: 1983-07-05
- Earliest claimed: 1980-12-31
- Assignees: Mobil Oil Corporation
- Inventors: Tsoung-Yuan Yan
- Web page: https://patentgrep.com/patent/US4391782A

## CPC

- C22B 60/0226: {using acidic solutions or liquors}
- C22B 60/0265: {extraction by solid resins}
- C22B: PRODUCTION AND REFINING OF METALS (electrolytic C25); PRETREATMENT OF RAW MATERIALS

## Abstract

A process is described for improving yield and leaching rates of mineral values in uranium-bearing formations associated with high brine aquifers by using high pressure CO.sub.2 /oxidant in the leaching solution. The high pressure CO.sub.2 overcomes the inhibiting effect of NaCl on the rate of leaching. Uranium is recovered at the well head by ion exchange at a pH of about 4.5 to about 5.0 either under pressure to keep the CO.sub.2 in solution or with provision for CO.sub.2 recovery and recycle.

## Claims

### Claim 1

An improved process for the recovery of mineral values from a mineral-bearing subterranean formation, wherein the subterranean formation has a sufficient chloride concentration to substantially inhibit the leaching rate of the mineral values therein, comprising the steps of:
(a) penetrating the formation with at least one injection well and at least one production well in communication with the injection well;
(b) introducing into the formation an aqueous leaching solution containing an oxidant and carbon dioxide wherein the carbon dioxide is introduced under sufficient pressure to substantially overcome the inhibiting effect of the chloride ion on the leaching rate; and
(c) producing the aqueous leaching solution containing oxidized and solubilized mineral values.

### Claim 2 (depends on 1)

The process of claim 1 wherein the oxidant is selected from the group consisting of oxygen, oxygen-containing gas, air or any combination thereof.

### Claim 3 (depends on 2)

The process of claim 2 wherein the gaseous oxidant is injected into the formation prior to the injection of the aqueous leaching solution containing carbon dioxide.

### Claim 4 (depends on 1)

The process of claim 1 wherein the mineral values are uranium values.

### Claim 5 (depends on 1)

The process of claim 1 wherein the carbon dioxide is introduced into the leaching solution at bottom-hole location of the injection well.

### Claim 6 (depends on 1)

The process of claim 1 wherein the carbon dioxide is introduced at a pressure of about 10 to about 100 psig.

### Claim 7 (depends on 1)

The process of claim 1 wherein the carbon dioxide is introduced under sufficient pressure to give the produced aqueous leaching solution a pH of about 4.0 to about 5.0.

### Claim 8 (depends on 7)

The process of claim 7 further comprising the step of passing the produced solution through an ion exchange resin to recover mineral values therefrom.

### Claim 9

An improved process for the in situ recovery of uranium values from a uranium-bearing subterranean formation, having formation fluids with a sufficient chloride concentration to substantially inhibit the leaching rate of the uranium value therein, comprising the steps of:
(a) penetrating the formation with at least one injection well and at least one production well in communication with the injection well;
(b) introducing into the formation an aqueous leaching solution containing an oxidant and carbon dioxide wherein the carbon dioxide is introduced under sufficient pressure to substantially improve the uranium-leaching rate and to give the formation fluids a pH of from about 4.0 to about 5.0;
(c) producing pregnant leaching solution containing uranium values and having a pH of from about 4.0 to about 5.0; and
(d) passing the produced pregnant leaching solution through an ion exchange resin to recover uranium values therefrom.

### Claim 10 (depends on 9)

The process of claim 9 wherein the oxidant is selected from the group consisting of oxygen, oxygen-containing gas, air or any combination thereof.

### Claim 11 (depends on 10)

The process of claim 10 wherein the oxidant is introduced into the formation prior to the introduction of the aqueous leaching solution.

### Claim 12 (depends on 9)

The process of claim 9 wherein the carbon dioxide is introduced into the formation to the injection of the aqueous solution.

### Claim 13 (depends on 9)

The process of claim 9 wherein the carbon dioxide is introduced into the leaching solution at bottom-hole location of the injection well.

### Claim 14 (depends on 9)

The process of claim 9 wherein the carbon dioxide is introduced at a pressure of about 10 to about 100 psig.