U.S. patent application number 14/760377 was filed with the patent office on 2015-12-10 for continuous ion exchange process integrated with membrane separation for recovering uranium.
This patent application is currently assigned to Rohm and Haas Company. The applicant listed for this patent is DOW GLOBAL TECHNOLOGIES LLC, ROHM AND HAAS COMPANY. Invention is credited to Peter E.M. Aerts, Robert T. Krueger, Areski Rezkallah.
Application Number | 20150354027 14/760377 |
Document ID | / |
Family ID | 50151369 |
Filed Date | 2015-12-10 |
United States Patent
Application |
20150354027 |
Kind Code |
A1 |
Rezkallah; Areski ; et
al. |
December 10, 2015 |
CONTINUOUS ION EXCHANGE PROCESS INTEGRATED WITH MEMBRANE SEPARATION
FOR RECOVERING URANIUM
Abstract
A continuous ion exchange system and method for recovering
uranium from a pregnant liquor solution wherein the method includes
the steps of: (a) treating the pregnant liquor solution (16) with a
membrane (28) to produce: i) a leach permeate solution (30) at
least partially depleted of uranium and carbonate and ii) a leach
concentrate solution (30') having a relatively higher concentration
of uranium and carbonate and which is at least partially depleted
of chloride; (b) passing the leach concentrate stream (30') through
an ion exchange bed to load uranium onto a strong base anion
exchange resin and produce an untreated barren (18) solution
depleted of uranium, (c) passing an eluant solution (20) comprising
bicarbonate through the loaded ion exchange bed to strip uranium
from the strong base anion exchange resin and produce an eluate
(22) comprising uranium and bicarbonate, (d) precipitating uranium
(24) from the eluate (22) to produce a residual eluant solution
(26) depleted of uranium, and (e) repeating steps (a)-(d).
Inventors: |
Rezkallah; Areski;
(Lezennes, FR) ; Aerts; Peter E.M.; (Hulst,
NL) ; Krueger; Robert T.; (Huntersville, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROHM AND HAAS COMPANY
DOW GLOBAL TECHNOLOGIES LLC |
Philadelphia
Midland |
PA
MI |
US
US |
|
|
Assignee: |
Rohm and Haas Company
Philadelphia
PA
|
Family ID: |
50151369 |
Appl. No.: |
14/760377 |
Filed: |
January 27, 2014 |
PCT Filed: |
January 27, 2014 |
PCT NO: |
PCT/US2014/013106 |
371 Date: |
July 10, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61767286 |
Feb 21, 2013 |
|
|
|
Current U.S.
Class: |
423/7 |
Current CPC
Class: |
C22B 60/0265 20130101;
C22B 3/42 20130101 |
International
Class: |
C22B 60/02 20060101
C22B060/02; C22B 3/42 20060101 C22B003/42 |
Claims
1. A method for recovering uranium from an alkaline pregnant liquor
solution comprising uranium, carbonate and chloride, by passing the
pregnant liquor solution through a plurality of ion exchange beds
(12, 14) containing strong base anion exchange resin that cycle
through process zones as part of a repeating uranium recovery
circuit, wherein the method comprises the steps of: (a) treating
the pregnant liquor solution (16) with a membrane (28) to produce:
i) a leach permeate solution (30) at least partially depleted of
uranium and carbonate and ii) a leach concentrate solution (30')
having a relatively higher concentration of uranium and carbonate
and which is at least partially depleted of chloride; (b) passing
the leach concentrate stream (30') through an ion exchange bed to
load uranium onto the ion exchange resin and produce an untreated
barren (18) solution depleted of uranium, (c) passing an eluant
solution (20) comprising bicarbonate through the loaded ion
exchange bed to strip uranium from the ion exchange resin and
produce an eluate (22) comprising uranium and bicarbonate, (d)
precipitating uranium (24) from the eluate (22) to produce a
residual eluant solution (26) depleted of uranium, and (e)
repeating steps (a)-(d).
2. The method of claim 1 including the steps of: (f) treating a
portion of the untreated barren solution (18) of step (b) with a
membrane (31) to produce: i) a barren permeate solution (32) at
least partially depleted of carbonate and ii) a barren concentrate
solution (32') having a relatively higher concentration of
carbonate, and (g) combining the barren permeate solution (32) with
at least one of the pregnant liquor solution (16) or the leach
leach concentrate solution (30') of step (a).
3. The method of claim 1 including the steps of: (h) treating a
portion of the residual eluant solution (26) of step (d) with a
membrane (38) to produce: i) a residual eluate permeate solution
(40) at least partially depleted of bicarbonate and ii) a residual
eluate concentrate solution (40') having a relatively higher
concentration of bicarbonate than the residual eluate solution
(26), and (i) combining the residual eluate concentrate solution
(40') with at least one of the pregnant liquor solution (16) or the
leach concentrate solution (30') of step (a).
Description
FIELD
[0001] The present invention is directed toward a continuous ion
exchange process for recovering uranium from pregnant liquor
solutions.
INTRODUCTION
[0002] Continuous ion exchange (CIX) processes have been used since
the 1970's to recover uranium from pregnant liquor solutions (PLS).
A brief overview of the process is described by: Anton R. Hendriksz
and Ronald R. McGregor, "The extraction of uranium from in-situ
leach solutions using NIMCIX ion exchange contactor," Annual
Uranium Seminar (proceedings) 1980, 4.sup.th, pages 121-124. In
general, the CIX process involves the use a uranium recovery
circuit including of a plurality of ion exchange beds, commonly
arranged in carousal, which repetitively cycle through individual
process zones including uranium loading and elution. Various anions
(e.g. chloride, sulfate, carbonate, bicarbonate) present in the PLS
can also absorb on resin exchange sites during the resin loading
phase of the process. The extent to which these anions ultimately
compete with uranium anions is influenced by their relative
concentration and affinity for the resin along with the pH and
temperature of the leach solution. The recycling of barrens or
residual eluant exacerbates this problem by effectively
concentrating these competing anions to the point where they result
in a loss of separation efficiency, e.g. lower resin capacity, more
frequent resin elution, eluant replacement, dilution of PLS, and
the like.
SUMMARY
[0003] The present invention includes a continuous ion exchange
system and method for recovering uranium from a pregnant liquor
solution that integrates the use of one or more membrane
separations to reduce the concentration of competing anions. In one
embodiment, the method includes recovering uranium from an alkaline
pregnant liquor solution including uranium, carbonate and chloride.
The pregnant liquor solution is passed through a plurality of ion
exchange beds (12, 14) resin that cycle through process zones as
part of a repeating uranium recovery circuit. The method includes
the steps of: (a) treating the pregnant liquor solution (16) with a
membrane (28) to produce: i) a leach permeate solution (30) at
least partially depleted of uranium and carbonate and ii) a leach
concentrate solution (30') having a relatively higher concentration
of uranium and carbonate and which is at least partially depleted
of chloride; (b) passing the leach concentrate stream (30') through
an ion exchange bed to load uranium onto a strong base anion
exchange resin and produce an untreated barren (18) solution
depleted of uranium, (c) passing an eluant solution (20) comprising
bicarbonate through the loaded ion exchange bed to strip uranium
from the strong base anion exchange resin and produce an eluate
(22) comprising uranium and bicarbonate, (d) precipitating uranium
(24) from the eluate (22) to produce a residual eluant solution
(26) depleted of uranium, and (e) repeating steps (a)-(d).
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a schematic view of an embodiment of the present
continuous exchange system.
DETAILED DESCRIPTION
[0005] The invention includes a system and method for recovering
uranium from a pregnant liquor solution, ("PLS"). The source of the
PLS is not particularly limited but is typically produced by heap
leaching, in-situ leaching, vat leaching or pressure leaching of
carbonate-containing uranium ores. In one embodiment, the leach
ores reside in a lixiviation tank from which the PLS is drawn. The
PLS comprises an alkaline solution preferably having a pH of at
least 9 and more preferably at least 10; and further includes
uranium, bicarbonate, carbonate, sulfate and chloride anions along
with their counter cations and corresponding salts. Even though the
concentration of these anions is dynamic, they are preferably
maintained within the following ranges: carbonate: 10-60 g/L;
bicarbonate: 1-20 g/L; chloride: 0 to 10 g/L; sulfate: 0-25 g/L.
While the tetravalent uranyl tricarbonate complex anion
UO.sub.2(CO.sub.3).sub.3.sup.4-- predominates, a divalent ion
UO.sub.2(CO.sub.3).sub.2.sup.2- 2H.sub.2O may exist at low
carbonate concentration. During the loading phase of the process,
the mobile exchange ion ("X," e.g. chloride, hydroxyl, etc.)
initially adsorbed on the exchange resin (R) and the uranium anions
in solution will proceed as follows:
4RX+UO.sub.2(CO.sub.3).sub.3.sup.4-.fwdarw.R.sub.4UO.sub.2(CO.sub.3).sub-
.3+4X.sup.-
When an anion exchange resin is provided in the carbonate form, the
loading reactions proceeds as follows:
2(R.sup.+).sub.2CO.sub.3.sup.2-+UO.sub.2(CO.sub.3).sub.3.sup.4-.fwdarw.(-
R.sup.+).sub.4UO.sub.2(CO.sub.3).sub.3.sup.4-+2CO.sub.3.sup.2-
During the elution phase, an eluant solution (e.g. from 50 g/L to
saturated aqueous bicarbonate solution) is passed through the
uranium loaded ion exchange bed and exchanges eluant anions for
uranium anions.
[0006] As part of the present method, the PLS is subject to
continuous ion exchange (CIX) including the step of passing PLS
through a plurality of ion exchange beds containing strong base
anion exchange resin. The beds pass through individual process
zones as part of a repeating uranium recovery circuit schematically
illustrated in FIG. 1. More specifically, a CIX unit is generally
shown at 10 including a plurality of ion exchange beds (12, 14)
containing a strong base anion exchange resin that sequentially
pass through individual process zones (e.g. A, B) as part of a
uranium recovery circuit. Each zone preferably includes at least
one ion exchange bed or column, and in practice may include a
plurality of individual beds. The method includes the following
sequential steps:
[0007] (a) passing the PLS (16) through an ion exchange bed (zone
A) to load uranium onto the ion exchange resin and produce an
untreated barren solution (18) which is depleted of uranium, and
(b) passing an eluant solution (20) through the uranium loaded ion
exchange bed(s) (zone B) to strip uranium from the ion exchange
resin and produce an eluate (22). The eluate (22) may be then
treated to precipitate out uranium (24) leaving a residual eluate
solution (26) that may be optionally reused. The method may include
additional process zones as is well known in the art, e.g. rinsing,
washing, scrubbing, etc. Processed uranium ore may be stored in a
lixiviation tank (27) from which PLS is drawn. PLS and eluant may
be maintained in tanks (16'), (20'), respectively. The tanks are in
selective fluid communication with the ion exchange beds (12, 14).
Fluid flow may be controlled by a plurality of values and a control
panel (not shown) as the beds (12, 14) cycle through the individual
process zones (A and B). CIX equipment for performing the subject
method is available from PuriTech (e.g. IONEX.TM.), Ionex
Separations and Calgon Carbon (e.g. ISEP.TM.) and is also described
in U.S. Pat. No. 7,594,951. Suitable ion exchange resins include
AMBERSEP.TM. 400 strong base anion exchange resin available from
The Dow Chemical Company. This resin includes a
styrene-divinylbenzene copolymer (gel) matrix with functional
quaternary ammonium groups. The resin may be initially provided in
various ionic forms, e.g. sulfate, carbonate, hydroxyl and
chloride.
[0008] In order to reduce the concentration of competing anions
(e.g. chloride) present in the PLS (16), at least a portion of the
PLS is be treated with a membrane (28) to produce: i) a leach
permeate solution (30) at least partially depleted of uranium and
carbonate and ii) a leach concentrate solution (30') having a
relatively higher concentration of uranium and carbonate and that
is at least partially depleted in monovalent anions (e.g. chloride)
as compared with the untreated PLS (16). The leach permeate
solution (30) may be disposed or reused. For example, the leach
permeate solution (30) may be subject to further membrane treatment
(not shown), e.g. with a reverse osmosis membrane (e.g. FILMTEC.TM.
XLE-440). The concentrate solution resulting from such a reverse
osmosis treatment includes most of the remaining ionic species
(e.g. chloride, sulfate) and can be disposed;
[0009] whereas the permeate solution can be recycled and used in
the lixiviation tank (27) to replace evaporative loss, used to make
fresh bicarbonate solution added to the lixiviation tank (27), or
used to dilute the PLS (16) or leach concentrate solution
(30').
[0010] The leach concentrate solution (30') (and optional blended
PLS (16)) is passed through an ion exchange bed (12) to load
uranium onto the strong base anion resin and produce an untreated
barren solution (18) depleted of uranium. The untreated barren
solution (18) may be disposed of, recycled back to the lixiviation
tank (27), or in a preferred embodiment, subject to further
treatment with a membrane (31). For example, all or a portion of
the untreated barren solution (18) may be treated with a membrane
(31) to produce: i) a barren permeate solution (32) at least
partially depleted of carbonate (and other anions optionally
including sulphate and chloride) and ii) a barren concentrate
solution (32') having a relatively higher concentration of
carbonate. The barren permeate solution (32) may be optionally
recycled to (i.e. combined with) the PLS (16) or leach concentrate
solution (30') for use in the loading phase of the process. The
barren concentrate solution (32') may be optionally disposed (34)
or recycled, e.g. all or a portion may be recycled to the
lixiviation tank (27). In a preferred embodiment, the barren
concentrate solution (32') is subject to further membrane treatment
(not shown), e.g. with a reverse osmosis membrane with the
resulting permeate being used in the lixiviation tank (27) to
replace evaporative loss, used to make fresh bicarbonate solution
added to the lixiviation tank (27), or used to dilute the PLS (16)
or leach concentrate solution (30'). The eluant solution (20)
passes through the uranium loaded ion exchange bed(s) (zone B) to
strip uranium from the ion exchange resin and produce an eluate
(22). The eluate (22) may be then treated to precipitate out
uranium (24) leaving a residual eluate solution (26). By way of
example, the eluate may be neutralized with sulfuric acid and
uranium can be precipitated with hydrogen peroxide. In this
example, the resulting residual eluate solution (26) includes
sodium sulfate along with carbonate/bicarbonate. This residual
eluate solution (26) may then be disposed of, recycled to the
lixiviation tank (27) or preferably subject to further membrane
treatment. For example, at least a portion of the residual eluate
solution (26) may be treated with a membrane (38) to produce: i) a
residual eluate permeate solution (40) at least partially depleted
of bicarbonate (and uranium) and ii) a residual eluate concentrate
solution (42) having a relatively higher concentration of
bicarbonate (and uranium) than the residual eluate solution (26).
The residual eluate concentrate solution (42) can be recycled
directly to the lixiviation tank (27) the PLS (16) or the leach
concentrate solution (30'). The residual eluate permeate solution
(40) may be disposed, or further treated with membranes (not
shown). For example, the residual eluate permeate solution (40) may
be further treated with a reverse osmosis membrane (e.g.
FILMTEC.TM. XLE-440 or FILMTEC.TM. BW30 XFR-400/34i or
FILMTEC.TM.XFRLE-400/34i available from The Dow Chemical Company.
This treatment creates a second permeate solution that is depleted
of almost all ions (e.g. over 98% rejection of chloride) and a
second concentrate solution including most of the ions and salts
that were present in the residual eluate permeate solution (40).
This second permeate solution can be recycled to the lixiviation
tank (27), used to prepare fresh bicarbonate solution for addition
to the lixiviation tank (27) or for diluting the PLS (16) or leach
concentrate solution (30'). The second concentrate solution can be
disposed.
[0011] Different membranes may be used depending upon the degree of
ion separation desired. Applicable membranes (28, 31 and 38)
include nanofiltration and reverse osmosis elements such as
FILMTEC.TM. NF90 and NF 270, FILMTEC.TM. XLE-440 or FILMTEC.TM.
BW30 XFR-400/34i or FILMTEC.TM. XFRLE-400/34i available from The
Dow Chemical Company.
[0012] Many embodiments of the invention have been described and in
some instances certain embodiments, selections, ranges,
constituents, or other features have been characterized as being
"preferred." Characterizations of "preferred" features should in no
way be interpreted as deeming such features as being required,
essential or critical to the invention. Stated ranges include end
points. The entire subject matter of each of the aforementioned
patent documents is incorporated herein by reference.
* * * * *