U.S. patent application number 09/265279 was filed with the patent office on 2001-05-24 for recovery of nickel and cobalt from ore.
This patent application is currently assigned to William P.C. Duyvesteyn. Invention is credited to DUYVESTEYN, WILLEM P. C., HANSON, JAMES S., NEUDORF, DAVID A., WEENINK, ERIK M..
Application Number | 20010001650 09/265279 |
Document ID | / |
Family ID | 23009806 |
Filed Date | 2001-05-24 |
United States Patent
Application |
20010001650 |
Kind Code |
A1 |
DUYVESTEYN, WILLEM P. C. ;
et al. |
May 24, 2001 |
RECOVERY OF NICKEL AND COBALT FROM ORE
Abstract
A process is provided for the selective recovery from an impure
solution of pure nickel and cobalt solutions, suitable for
electrolysis of the respective metals. The impure solution may be
that obtained from acid leaching of nickel/cobalt bearing laterite
or oxide ore. The impure solution is contacted with a solid ion
exchange resin to selectively extract nickel and cobalt, while
rejecting at least one element of the group manganese, magnesium,
calcium, iron(II), and chromium(III). The ion exchange resin
contains bis-picolyl amine as the primary chelating group. The
impure solution has sufficiently low levels of chromium(VI) and
copper to allow repeated use of the ion exchange resin. The
metal-bearing resin is washed and then stripped with an acid
solution. This solution is then contacted with a water-immiscible
organic phase for the selective extraction of cobalt, leaving
nickel in the raffinate as a substantially pure nickel solution.
The loaded organic phase is stripped with another acid solution to
produce a substantially pure cobalt solution. The extractant
contains an organic phosphinic acid as the active group for
extraction. Nickel and cobalt can be recovered in essentially pure
form from the respective pure nickel and cobalt solutions by a
variety of conventional techniques, for example by
electrowinning.
Inventors: |
DUYVESTEYN, WILLEM P. C.;
(RENO, NV) ; NEUDORF, DAVID A.; (RENO, NV)
; WEENINK, ERIK M.; (SPARKS, NV) ; HANSON, JAMES
S.; (RENO, NV) |
Correspondence
Address: |
G PETER NICHOLS
BRINKS HOFER GILSON & LIONE
NBC TOWER SUITE 3600
P O BOX 10395
CHICAGO
IL
60610
|
Assignee: |
William P.C. Duyvesteyn
|
Family ID: |
23009806 |
Appl. No.: |
09/265279 |
Filed: |
March 9, 1999 |
Current U.S.
Class: |
423/139 ;
423/24 |
Current CPC
Class: |
C22B 15/0093 20130101;
C22B 23/065 20130101; C22B 3/3842 20210501; Y02P 10/20 20151101;
C22B 23/043 20130101; C22B 23/0484 20130101; C22B 3/42
20130101 |
Class at
Publication: |
423/139 ;
423/24 |
International
Class: |
C22B 023/00 |
Claims
What is claimed is:
1. A hydrometallurgical process for the recovery of nickel and
cobalt comprising the steps of a. providing an aqueous feed
solution containing nickel, cobalt, and at least one impurity
selected from the group consisting of manganese, magnesium,
calcium, aluminum, iron(II), and chromium(III) ions; b. contacting
the feed solution with a solid ion exchange resin to form a nickel
and cobalt-loaded resin and an ion exchange raffinate, containing
at least one impurity; c. eluting the nickel and cobalt from the
resin to form an eluate containing a soluble nickel salt and a
soluble cobalt salt; d. contacting the eluate with a
water-immiscible organic phase containing an extractant to load
cobalt onto the extractant to form a cobalt-containing organic
phase and a nickel-containing raffinate; e. separating the
cobalt-containing organic phase from the nickel-containing
raffinate; and, f. eluting the cobalt-containing organic phase with
a mineral acid or other eluant to produce a cobalt-containing
aqueous solution.
2. The process of claim 1 wherein the feed solution originates from
mineral acid leaching of a laterite or oxide ore wherein the ore
contains cobalt and nickel and wherein the mineral acid is selected
from the group consisting of sulfuric acid, hydrochloric acid,
nitric acid, and mixtures thereof.
3. The process of claim 1 wherein the feed solution originates from
sulfuric acid pressure leaching of a laterite or oxide ore wherein
the ore contains, cobalt and nickel.
4. The process of claim 1 wherein the feed solution originates from
atmospheric leaching of a laterite or oxide ore wherein the ore
contains cobalt and nickel.
5. The process of claim 1 wherein the feed solution originates from
bioxidation of sulfide or mixed oxide/sulfide ore or concentrate
which contains at least one of cobalt and nickel.
6. The process of claim 1 wherein the feed solution includes copper
ions and wherein the process includes the additional step of
removing copper ions from the feed solution prior to contacting
with the ion exchange resin.
7. The process of claim 6 wherein the copper ions are removed from
the feed solution by contacting the feed solution with an ion
exchange resin selective to the removal of copper.
8. The process of claim 6 wherein the copper ions are precipitated
from the feed solution by adding a sulfide-containing compound to
the feed solution.
9. The process of claim 1 wherein the feed solution contains
chromium (VI) ions and the process includes the additional step of
removing chromium (VI) ions from the feed solution by reducing with
a reductant prior to contacting the feed solution with the ion
exchange resin.
10. The process of claim 9 wherein the reductant is selected from
the group consisting of SO.sub.2, H.sub.2SO.sub.3,
Na.sub.2SO.sub.3, H.sub.2S, iron(II), iron(0) and mixtures
thereof.
11. The process of claim 1 wherein the nickel and cobalt are eluted
from the nickel and cobalt loaded ion exchange resin with an acid
selected from the group consisting of sulfuric, hydrochloric and
nitric.
12. The process of claim 1 wherein the ion exchange resin contains
a chelating group selected from the group consisting of
2-picolylamine, bis-(2-picolyl)amine, N-methyl-2-picoylamine,
N-(2-hydroxyethyl)-2-pocoly- lamine, and
N-(2-hydroxypropyl)-2-picoylamine, and mixtures thereof.
13. The process of claim 1 wherein the extractant is an organic
phosphinic acid.
14. The process of claim 13 wherein the extractant is
bis(2,4,4-trimethylpentyl) phosphinic acid.
15. The process of claim 1 including the additional step of
electrowinning the cobalt-containing aqueous solution to recover
cobalt.
16. The process of claim 15 wherein a spent electrolyte is produced
and is used to strip the cobalt from the cobalt-containing organic
phase.
17. The process of claim 1 including the additional step of
electrowinning the nickel-containing raffinate to recover
nickel.
18. The process of claim 17 wherein a spent electrolyte is produced
and is used to elute the absorbed nickel and cobalt form the ion
exchange resin.
19. The process of claim 1 further comprising the steps of
providing the resin with a series of columns and passing the feed
solution serially through these columns.
20. The process of claim 1 wherein the ion exchange raffinate is
contacted with at least a second ion exchange resin to form at
least a second nickel and cobalt-loaded resin and at least a second
raffinate.
21. The process of claim 20 including the additional steps of
eluting the nickel and cobalt from the at least second ion exchange
resin to form at least a second eluate containing a soluble nickel
salt and a soluble cobalt salt and combining the eluate and at
least the second eluate prior to contacting with the
water-immiscible organic phase.
22. The process of claim 1 wherein a pH of the eluate prior to
contacting with the water-immiscible organic phase is maintained at
a level between about 5 and about 5.5 by the addition of a base
selected from the group consisting of sodium hydroxide, ammonium
hydroxide, sodium carbonate, and mixtures thereof, or a mixture of
basic nickel/cobalt carbonate, nickel/cobalt hydroxide, and
mixtures thereof.
23. The process of claim 1 including the additional step of
contacting the cobalt-containing loaded organic phase with a strong
cobalt solution to remove co-loaded nickel.
24. A hydrometallurgical process for the recovery of nickel and
cobalt comprising the steps of a. providing an aqueous feed
solution containing nickel, cobalt, and at least one impurity
selected from the group consisting of manganese, magnesium calcium,
aluminum, iron(II), chromium(VI) and copper ions; b. removing any
copper ions from the aqueous feed solution; c. contacting the feed
solution with a solid ion exchange resin to form a nickel and
cobalt-loaded resin and an ion exchange raffinate, containing at
least one impurity; d. eluting the nickel and cobalt from the resin
to form an eluate containing a soluble nickel salt and a soluble
cobalt salt; e. contacting the eluate with a water-immiscible
organic phase containing an extractant to load cobalt onto the
extractant to form a cobalt-containing organic phase and a
nickel-containing raffinate; f. separating the cobalt-containing
organic phase from the nickel-containing raffinate; and, g. eluting
the cobalt-containing organic phase with a mineral acid or other
eluant to produce a cobalt-containing aqueous solution.
25. The process of claim 24 further comprising the step of reducing
the chromium(VI) to chromium(III).
Description
[0001] The present invention relates to the hydrometallurgical
processing of nickeliferous ores and, in particular, to the
recovery of pure nickel and cobalt solutions by a combination of
solid-liquid and liquid-liquid extraction from leach solutions such
as those derived from the acid leaching of nickeliferous ores.
BACKGROUND OF THE INVENTION
[0002] Pure nickel metal can be recovered by electrolysis of
aqueous solutions of nickel salts, such as nickel chloride and/or
nickel sulfate. In order to produce pure nickel metal, of at least
99.8% purity, it is necessary to keep most transition metal
impurities, e.g., copper, iron, manganese, and cobalt, at extremely
low levels in the nickel electrolyte. In addition, other
impurities, e.g., chromium, iron, aluminum and calcium, can cause
significant deterioration of the physical properties of the nickel
metal cathodes, rendering a nickel electrowinning process
impractical. Thus, in commercial practice, it is usually necessary
to use extremely pure nickel electrolyte. Other nickel processes,
e.g. hydrogen reduction of nickel solution to form nickel powder,
also require pure solutions.
[0003] Cobalt occurs in association with nickel in most of its
ores, both laterite or oxide ores, and sulfide ores. The so-called
limonitic ores (high iron oxide and hydroxide content, low
magnesium silicates content) in particular often contain cobalt at
.gtoreq.{fraction (1/20)}.sup.th the nickel concentration. In
certain ores, the cobalt content can even exceed the nickel
content, which makes these ores more amenable to cobalt recover
only. This will still require the removal of nickel for the
production of pure cobalt metal. Table 1 shows typical compositions
for various sulfide and oxide ores and concentrates:
1TABLE 1 Typical composition for various sulfide and oxide ores and
concentrates Sample Ni (%) Co (%) Fe (%) Mg (%) Sulfide ore A 0.5
0.02 5 25 Sulfide ore B 1.4 0.1 35 Sulfide concentrate A 9 0.3 17
Sulfide concentrate C 3 0.1 14 15 Sulfide concentrate D 10 0.2 25 8
Sulfide concentrate E 12 0.3 30 6 Limonite 1 1.6-1.9 0.15-0.2 15-18
Limonite 2 1.4 0.3 43 1 Limonite 3 0.9 0.05 29 4 Limonite 4 0.7
0.02 35 0.4 Saprolite 5 2.5-2.9 0.05-0.1 14-15 12-18 Saprolite 6
2.0 0.07 21 11 Saprolite 7 2.4 0.06-0.09 13-16 15 Limonite, typical
0.8-1.8 0.05-0.2 30-50 0-10 Saprolite, typical 1.8-3.5 0.01-0.05
10-30 10-25 Oxide ore 1 0.02-0.1 0.3-1.0 2-5
[0004] Production of nickel that meets the London Metal Exchange
contract specifications (Class I nickel), requires that the cobalt
content of the nickel be less than 0.15%. This corresponds to a
nickel to cobalt ratio of about 665, which is at least 33 times
larger than the ratio in the limonitic ore. Successful nickel
processing therefore requires an effective nickel/cobalt separation
step. Unfortunately, the chemical similarity of nickel and cobalt
makes their separation difficult.
[0005] Similarly, the production of high purity cobalt faces the
same problems as the production of high purity nickel. Therefore,
there is a continuing need for a process to produce both high
purity nickel and high purity cobalt.
[0006] One commercial process for recovery of nickel and cobalt
from limonite ores is described in M. E. Chalkley and I. L. Toirac,
"The acid pressure leach process for nickel and cobalt laterite.
Part I: Review of operation at Moa" in Hydrometallurgy and Refining
of Nickel and Cobalt, edited by W. C. Cooper and I Mihaylov,
Proceedings of 27th Annual Hydrometallurgical Meeting, The
Metallurgical Society of CIM, Canada, 1997, pp. 341-353. In this
process, sulfuric acid pressure leaching (SAPL) is used to
solubilize nickel and cobalt as sulfate salts, while precipitating
most of the contained iron as hematite. Other impurities, such as
copper, manganese, magnesium, calcium, chromium, and aluminum,
partially or completely dissolve. Thereafter, the nickel and cobalt
must be separated from all of these impurities prior to recovery of
the pure forms of nickel and cobalt. The first step in this
purification process involves precipitation of the nickel and
cobalt (plus copper and zinc impurities) as a mixed sulfide phase
by the addition of hydrogen sulfide gas under pressure and at a
slightly elevated temperature (about 120.degree. C.). This step is
reasonably effective for separating nickel and cobalt from
manganese, magnesium, calcium, chromium, aluminum, and iron,
because the latter elements do not precipitate to any great extent.
The purified, solid (Ni, Co)S is separated from the barren solution
by settling and filtration. Unfortunately, the mixed sulfide needs
to be redissolved and further purified prior to separation of the
nickel and cobalt, and recovery of the pure metals. The
redissolution and further purification is generally accomplished by
releaching the mixed sulfide with water or aqueous solution of
ammonia and ammonium sulfate and air or oxygen, under pressure and,
in the case of water leaching, at elevated temperature (about
180-200.degree. C.). Thus, in this method, the production of a
relatively pure nickel-cobalt solution from the ore requires three
successive pressure metallurgy and solid/liquid separation steps
that add to the complexity of the process. Moreover, the process
uses hydrogen sulfide gas, a highly toxic and expensive compound,
under pressure.
[0007] Because of the disadvantages of sulfide precipitation, it
has been proposed to directly recover nickel and cobalt as separate
pure solutions from leach liquor.
[0008] One route is by using extractants developed by Cytec Ltd.,
as for example described in U.S. Pat. No. 5,378,262 and 5,447,552.
These Cytec extractants are organic phosphinic and thiophosphinic
compounds and have high cobalt and nickel separation coefficients
in sulfate systems, ranging from 5 for alkylated monothiophosphinic
to >2500 for alkylated phosphinic acid. The separation
coefficient (S) compares the distribution of the two metals between
the aqueous and organic phase and is defined as:
S=D.sub.A/D.sub.B
[0009] where D.sub.A and D.sub.B are the distribution coefficients
of the two metals at equilibrium. The distribution coefficient in
turn is defined as:
D=[Concentration of metal in organic phase] / [Concentration of
metal in the aqueous phase]
[0010] One phosphinic compound is Cyanex 272,
bis(2,4,4-trimethylpentyl)ph- osphinic acid. The extraction
characteristics of Cyanex 272 as a function of solution pH are
shown in Table 2 and FIG. 3. The pH.sub.50 value in Table 2
represents the pH at which 50% of the metal is extracted from the
aqueous into the organic phase at an organic to aqueous phase ratio
of 1:1.
2TABLE 2 Comparison for metal extraction (0.001 M sulfate) from
different Cyanex extractants (at 0.1 M in xylene) Extractant
pH.sub.50, pH.sub.50, pH.sub.50, pH.sub.50, pH.sub.50, pH.sub.50,
Co.sup.2+ Ni.sup.2+ Mn.sup.2+ Cu.sup.2+ Zn.sup.2+ Fe.sup.3+ Cyanex
272 5.2 7.05 3.5 4.6 3.0 1.6 Cyanex 302 4.0 5.8 4.8 <-1 1.8 1.0
Cyanex 301 0.85 1.55 N/A <-1 -0.4 0 Obtained from K. C. Sole, J.
B. Hiskey, "Solvent extraction characteristics of thiosubstituted
organophosphinic acid extractants", Hydrometallurgy, 30, pp. 345-65
(1992) and Cytec Product Information
[0011] FIG. 3 (which is derived from product information available
from Cytec) shows the metal extraction as a function of solution pH
for various metal sulfate solutions. The distance between the
curves for any two metals increases as the separation coefficient
increases. Thus, nickel and cobalt can be easily separated from
each other with Cyanex 272, by extracting cobalt at a pH of about
5.5. At this pH, nickel extraction is negligible and cobalt
extraction is more or less complete. Unfortunately, a substantial
amount of copper and manganese is also extracted at this pH. Since
manganese is always present in laterite leach liquors, the cobalt
strip liquor would be contaminated if the leach liquor were treated
directly by solvent extraction with Cyanex 272. Magnesium and
calcium may also cause problems in the solvent extraction process,
if present in the feed solution, because these elements are
extracted at pH values close to that at which cobalt is extracted
(see FIG. 3).
[0012] The compound bis (2,4,4-trimethylpentyl) monothiophosphinic
acid, commercially known as Cyanex 302, avoids the above problem,
because manganese is extracted at higher pH values than cobalt, as
shown in Table 2. Cyanex 302, however, may be unstable in the
presence of certain impurities (such as iron) and its consumption
would be uneconomically high to be practical for direct treatment
of laterite leach liquors.
[0013] The compound bis (2,4,4-trimethylpentyl) dithiophosphinic
acid, commercially known as Cyanex 301, also avoids the manganese
problem, but this compound extracts some impurities, e.g. copper
and ferric iron, almost irreversibly, resulting in poisoning of the
extractant. Copper is almost always present in laterite leach
liquors and can be removed by other means prior to treatment with
Cyanex 301. Nevertheless, if there were an upset in the copper
removal process, the subsequent Cyanex 301 processing circuit could
be irreversibly contaminated with copper.
[0014] Another proposed process for extracting nickel and cobalt
from limonite ores uses the above-described sulfuric acid pressure
leaching process (SAPL), followed by solvent extraction with Cyanex
301. This process is described in U.S. Pat. No. 5,378,262 and
5,447,552. In this process, hexavalent chromium, ferric iron and
copper are first removed. The solution is then contacted with a
water-immiscible organic phase containing an organic soluble
dithiophosphinic acid to recover and separate nickel and/or cobalt.
This patent has one important disadvantage, the extractant will not
allow repeated use in the presence of iron. For example, U.S. Pat.
No. 5,759,512 reports that small concentrations (20-50 mg/l) of
ferric iron Fe(III) present in the aqueous feed caused significant
oxidation of this extractant. Because the nickel in nickeliferous
oxide ores is partially contained in iron oxides, the presence of
small amounts of iron in the acid leach solution is inevitable even
after precipitation of the ferric iron.
[0015] Another route for the recovery of metals from solution is
through ion exchange (IX), which has been applied, for example, in
the extraction of uranium. This technique is very useful for the
recovery of ionic compounds into a purified and more concentrated
eluate solution. One advantage of ion exchange is the ability to
operate in the presence of solids, which can be flushed out of the
resin with properly designed back wash steps. This is contrary to
solvent extraction, where any suspended solids, such as fine clays
or colloidal silica typically present in leach liquors, will cause
`crud` formation. Crud may impair the organic/aqueous phase
separation, leading to high organic losses and increased
entrainment of organic in the aqueous phase and aqueous in the
organic phase. This entrainment may cause operating problems in the
downstream recovery processes and increased reagent consumption.
Other advantages of ion exchange are the ease of handling solid
resin beads and the chemical stability of resins at elevated
temperatures. In solvent extraction, evaporation and flammability
of the organic may limit the operating temperature to typically
less than 50.degree. C. Many ion exchange resins can easily handle
higher temperatures up to normal solution boiling points, which
enhances the resin kinetics and metals separation. The ability to
operate at higher temperature also allows immediate treatment of
the process solutions, as most leach solutions have temperatures
over 50.degree. C. For example, in the case of laterite pressure
leaching, the pregnant leach liquor is produced at a temperature
close to the normal boiling point of the solution. Thus expensive
cooling steps are not required and greater thermal efficiency is
possible.
[0016] It is, therefore, the object of the present invention to
provide an economical process to recover substantially pure nickel
and cobalt solutions from leach solutions by selective extraction
with organic extractants, without degradation that would limit the
repeated use of the organic extractant.
SUMMARY OF THE INVENTION
[0017] The present invention provides a process for the selective
recovery of pure nickel and cobalt solutions, suitable for
electrolysis or other final recovery steps, from a feed solution.
Preferably, the feed solution is obtained from sulfuric acid
leaching of nickel and cobalt bearing laterite or oxide ore. The
laterite ore may include the saprolite and/or limonite.
[0018] In general, the process includes the steps of providing an
aqueous feed solution containing nickel, cobalt, and at least one
element selected from the group consisting of manganese, magnesium,
calcium, iron(II), and chromium(III), contacting the feed solution
with a solid ion exchange resin to form a nickel and cobalt-loaded
resin and an ion exchange raffinate, eluting the nickel and cobalt
from the resin to form an eluate containing a soluble nickel salt
and a soluble cobalt salt, contacting the eluate with a
water-immiscible organic phase containing an extractant to load
cobalt onto the extractant to form a cobalt-containing organic
phase and a nickel-containing raffinate, and separating the
cobalt-containing organic phase from the nickel-containing
raffinate.
[0019] Each of the separated cobalt-containing organic phase and
nickel-containing raffinate can be further treated to form a
solution suitable for electrowinning or other process to recover
substantially pure nickel and cobalt products. The nickel resulting
from the electrowinning step meets the London Metal Exchange
contract specification and therefore, contains less than 0.15% by
weight of cobalt. Similarly, the cobalt resulting from the
electrowinning typically contains less than 0.1% by weight of
nickel.
[0020] By using ion exchange for the primary metals (nickel and
cobalt) recovery, many disadvantages of solvent extraction are
overcome. These include crud formation due to the presence of
solids, extra purification steps for the removal of organics from
the product stream, possible degradation of the organic
thiophosphinic acids, and the ability to operate at elevated
temperatures.
[0021] In one embodiment, any copper and chromium(VI) are removed
from the feed solution prior to contact with the ion exchange
resin. In another preferred embodiment, the raffinate from the ion
exchange resin is contacted with at least a second ion exchange
resin.
[0022] It is noted that, unless otherwise stated, all percentages
given in this specification and the appended claims refer to
percentages by weight.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a flow sheet for the process of the present
invention.
[0024] FIG. 2 is a flow sheet showing one embodiment of the process
of the present invention.
[0025] FIG. 3 is a graph of percentage of extraction of an element
using Cyanex 272 in a sulfate solution at varying pHs.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Turning now to FIG. 1, a flow sheet for the process of the
present invention is shown. In general, a feed solution 1 is
contacted with an ion exchange resin in ion exchanger 10 to
selectively load nickel and cobalt and to form a nickel and
cobalt-loaded resin and a raffinate 2 that contains most of the
impurities present in the feed solution. A strip solution 3
contacts the nickel and cobalt-loaded resin to elute the nickel and
cobalt from the resin and to form an ion exchange eluate solution 4
that contains a soluble nickel salt and a soluble cobalt salt,
substantially purified of most of the impurity elements present in
the feed solution. The eluate is then subjected to liquid/liquid
extraction 20 by contacting the eluate 4 with an organic phase that
contains an extractant to load cobalt onto the extractant to form a
cobalt-containing organic phase and a nickel-containing raffinate.
Thereafter, the cobalt-containing organic phase is separated from
the nickel-containing raffinate (pure nickel solution) 6. A strip
solution 5 contacts the cobalt-containing organic phase to recover
a pure cobalt solution 7. Both the pure nickel solution and the
pure cobalt solution may be subjected to further processes such as
electrowinning to recover pure nickel and cobalt, respectively.
[0027] In the present process, the feed solution contains nickel
and cobalt, as well as other elements such as aluminum, chromium,
manganese, magnesium, calcium, iron, copper, and zinc. Preferably,
the feed solution is derived from an ore that contains nickel and
cobalt. This can be accomplished, for example, by leaching either
oxide or sulfide ores with mineral acids or bio-leaching of sulfide
ore. In addition, the feed solution may be derived from any of the
processes described in PCOT publication WO 97/04139, the relevant
portions of which are incorporated herein by reference. The mineral
acid may be selected from the group consisting of sulfuric acid,
hydrochloric acid, nitric acid, and mixtures thereof. The ore may
be any laterite (oxide) or sulfide ore and the laterite ore may
include the saprolite and limonite. Such ores generally contain
about 0.5% to about 3% nickel and about 0.005% to about 0.5%
cobalt.
[0028] The feed solution may be further treated after the acid
leaching such as by neutralizing with a base (e.g., limestone) as
is known and conventional in the art.
[0029] The feed solution is contacted with a solid ion exchange
resin to selectively extract nickel and cobalt, while rejecting
manganese, magnesium, calcium, iron(II), and chromium(III), if
present in the feed solution. The ion exchange resin is preferably
a chelating resin that selectively absorbs nickel and cobalt. The
simplified chemical reaction for the ion exchange is as
follows:
2HR+M.sup.2+.fwdarw.MR.sub.2+2H.sup.+
[0030] In this equation, the underlined species represent the resin
and M represents any metal, preferably Ni.sup.2+or Co.sup.2+.
[0031] Suitable chelating ion exchange resins include those derived
from aminopyridine compounds such as the 2-picolylamines described
in U.S. Pat. No. 4,098,867 and 5,141,965, the relevant portions of
each are incorporated herein by reference. A preferred chelating
resin contains a functional group selected from the group
consisting of 2-picolylamine, bis-(2-picolyl)amine,
N-methyl-2-picoylamine, N-(2-hydroxyethyl)-2-pocoly- lamine, and
N-(2-hydroxypropyl)-2-picoylamine, and mixtures thereof. Suitable
resins include Rohm and Haas IR 904, Amberlite XE 318, Dow
XFS-43084, Dow XFS-4195, and Dow XFS-4196. The Dow XFS-4196
contains N-(2-hydroxyethyl)-2-picolylamine and the XFS-43084
contains N-(2-hydroxypropyl)-2-picolylamine. A preferred chelating
resin is Dow XFS-4195, manufactured by The Dow Chemical Company. It
contains bis-(2-picolyl)amine as the primary chelating group.
[0032] The distribution coefficients for a variety of elements
using XFS 4195 are shown in Table 3 (the values are obtained from
K. C. Jones and R. R. Grinstead, "Properties and hydrometallurgical
applications of two new chelating ion exchange resins", Chemistry
and Industry, Aug. 6, 1977, pp. 637-41).
3TABLE 3 Absorption constants for XFS 4195 in sulfate solution at
pH = 2 Cu Ni Fe.sup.3+ Cd Zn Co Fe.sup.2+ Ca Mg Al Mn 700 190 80 70
60 30 3 <2 <1 <1 <1
[0033] Nickel and cobalt can be extracted at relatively low pH
(1-4), leaving all of the above-mentioned impurities in the
raffinate solution. If necessary or desirable, the pH of the feed
solution may be adjusted to provide for optimum selective loading
of the nickel and cobalt onto the resin. Generally, the pH of the
feed solution is between about 1.0 and about 5.0, preferably
between about 2 and about 3.
[0034] It is also sometimes desirable to adjust the temperature of
the feed solution prior to contact with the ion exchange resin to
improve the kinetics of selective nickel and cobalt ion exchange.
Generally, the temperature of the feed solution is between about
20.degree.C. and about 95.degree.C., preferably between about
60.degree.C. and about 70.degree.C.
[0035] The ion exchange process may include, but is not limited to,
a single fixed bed of resin, two or more fixed beds in parallel or
in series, or a plurality of resin columns that move
countercurrently to the flow of the feed solution. For example, an
ISEP continuous contactor manufactured by Advanced Separation
Technologies, Inc. of Lakeland, Fla. or a Recoflo ion exchange
system made by Eco-Tec of Pickering, Ontario, Canada may be
used.
[0036] It is to be understood that any arrangement of ion exchange
resin suitable to selectively absorb substantially all the nickel
and cobalt in the feed solution can be used. The term
"substantially all" means that greater than 90% of the nickel and
cobalt in the feed solution is absorbed.
[0037] In a preferred embodiment, the ion exchange resin is
provided in two steps in series. As shown in FIG. 2, the feed
solution is passed through two ion exchange steps such that the
raffinate of the first stage, after neutralization, forms the feed
of the second stage. By using two stages, the absorption of nickel
and cobalt onto the resin is enhanced, resulting in substantially
complete removal of nickel and cobalt from the feed solution. It is
understood that more than two steps could be used for complete
nickel and cobalt removal from the feed solution.
[0038] In the preferred embodiment shown in FIG. 2, the feed
solution 101 is contacted with a first ion exchanger 110, which
absorbs most of the nickel and only a small portion of the cobalt.
This is because the resin is selective for nickel over cobalt while
the low pH generated by the replacement of the H.sup.+ions on the
resin with the nickel prevents cobalt from loading.
[0039] The raffinate 102 from the first ion exchange step contains
a small portion of the original nickel from the feed solution but
most of the cobalt from the feed solution. The ion exchange
raffinate 102 is treated with a base 111, such as limestone, in a
neutralization process 112 to neutralize the acid generated by the
first ion exchange step. Of course, it is to be understood that the
acid may be completely or only partially neutralized. The degree of
neutralization is generally determined based on the absorption
constant(s) of the material(s) sought to be removed at a particular
pH.
[0040] Generally, the pH is adjusted to provide a neutralized
raffinate pH of about 2.0 to about 4, preferably from about 3 to
about 3.5.
[0041] If necessary, the neutralized raffinate is subjected to a
solid-liquid separation 114 to form a neutralized raffinate
solution 115 (a feed solution to the second ion exchanger). The
neutralized raffinate is then subjected to a second ion exchange
step 116 to recover virtually all of the remaining cobalt and
nickel.
[0042] To allow repeated use of the ion exchange resin, the feed
solution desirably has low levels of chromium(VI) and copper
because the chelating resins containing the 2-picolylamines as
functional groups have a high affinity for copper and for
chromium(VI) (but do not load or absorb chromium(III)). These
elements can be removed by well-known techniques, such as chemical
reduction or ion exchange. For example, the copper and chromium(VI)
may be removed by a metal cementation step using iron, zinc or even
nickel to reduce chromium(VI) to chromium(III) and to cement
copper. Therefore, the process of the present invention
contemplates the additional step of removing copper and/or chromium
prior to contacting the feed solution with the ion exchange
resin.
[0043] In a preferred embodiment of the invention, copper is
removed from the feed solution prior to contact with the ion
exchange resin. It is also recognized that if the copper
concentration is very low, this removal step may not be required.
Copper removal can be carried out with a number of ion exchange
resins or by selective sulfide precipitation at low pH, or by any
other method apparent to those skilled in the art. For example, the
copper can be precipitated from the feed solution by adding to the
feed solution a sulfide-containing compound selected from the group
consisting of H.sub.2S, NaHS, and mixtures thereof.
[0044] It has also been found convenient to use a resin with
iminodiacetate functionality, for example, the resin IRC 718
manufactured by Rohm and Haas. This resin extracts copper in
preference to nickel and cobalt as shown in Table 4 (the values are
obtained from W. H. Waitz, Jr., "Ion exchange in heavy metals
removal and recovery", Amber-hi-lites #162, Rohm and Haas Company,
Philadelphia, Pa., Fall 1979)
4TABLE 4 Absorption constants for IRC-718 relative to calcium at pH
= 4 Hg Cu Pb Ni Zn Cd Co Fe.sup.2+ Mn Ca 2800 2300 1200 57 17 15
6.7 4.0 1.2 1.0
[0045] In another preferred embodiment of the invention,
chromium(VI) is removed from the feed solution prior to contact
with the ion exchange resin. It is also recognized that if the
chromium(VI) concentration is very low, this removal step may not
be required. The chromium(VI) can be removed by a variety of
techniques. For example, chromium(VI) can be converted to
chromium(II) by reduction, for example, with gaseous sulfur
dioxide.
[0046] Zinc may also be present in the feed solution and the ion
exchange resin will extract the zinc with the cobalt. Because the
zinc is generally carried with the cobalt, it does not unduly
contaminate the resulting nickel solution. If, however, it is
desired to produce cobalt substantially free of zinc, it can be
removed from the ion exchange eluate by solvent extraction or ion
exchange, in any manner understood by those skilled in the art. For
example, solvent extraction using di-2, ethyl hexyl phosphoric acid
can be used. The cobalt can then be extracted from the resulting
pure solution using Cyanex 272.
[0047] To recover the nickel and cobalt from the nickel and cobalt
loaded resin, it is eluted with a strip solution 3 (103) to form an
ion exchange eluate solution 4 (104a, 104b, 104) containing a
soluble nickel salt and a soluble cobalt salt. Before eluting the
nickel and cobalt, the resin may be washed with water to remove
entrained raffinate solution. Where more than one ion exchanger is
used, the eluate from each (104a, 104b) may be combined (104)
before the solvent extraction process 20 (120).
[0048] The strip solution may be any protonated material that will
selectively replace the nickel and cobalt with H.sup.+ions. The
strip solution 3 (103), therefore, may be a mineral acid selected
from the group consisting of sulfuric acid, hydrochloric acid,
nitric acid, or other suitable acid. The choice of suitable acid
depends on the subsequent nickel-cobalt separation process. Because
the present invention contemplates the use of solvent extraction to
separate the nickel from the cobalt, the choice of mineral acid
will, in large part, be dictated by the choice of extractant. For
example, where the extractant exhibits favorable nickel-cobalt
separation coefficients in a chloride solution, the selected
mineral acid will be hydrochloric acid. Preferably, sulfuric acid
is used because the preferred extractant, Cyanex 272, exhibits
large nickel-cobalt separation coefficients in the sulfate
system.
[0049] In a preferred embodiment of the invention, shown in FIG. 2,
the stripping solution includes at least a portion of spent
electrolyte 131 from a subsequent nickel electrowinning step. If
feasible, the spent electrolyte can form all or a portion of the
stripping solution 131 (3). The electrowinning reaction generates
one mole of sulfuric acid for each mole of nickel electrowon. Each
mole of acid so generated can theoretically strip one mole of
nickel and cobalt from the loaded ion exchange resin. Thus, the ion
exchange process can operate in a closed circuit with the
electrowinning step, allowing the spent electrolyte to contain a
high concentration of nickel. This nickel is recycled to the ion
exchange step and not lost.
[0050] As shown in FIG. 2, the ion exchange eluate is treated with
a base 105 in a neutralization process 108 and subsequently, if
necessary, separated in a solid-liquid separation 109 to leave an
ion exchange eluate suitable for separation of the cobalt from the
nickel.
[0051] The neutralized ion exchange eluate 4 (104) is contacted
with a water-immiscible organic phase containing an extractant for
the selective extraction of cobalt, leaving nickel in the raffinate
6 (106) as a substantially pure nickel solution.
[0052] One method for the separation of cobalt from nickel in
chloride solutions is by solvent extraction with tri-butyl
phosphate (TBP) and tri-iso-octyl amine (TIOA). Impurities such as
iron, copper and manganese, however, need to be removed prior to
cobalt extraction. Another method is by solvent extraction with
Cyanex 301, such as described in U.S. Pat. No. 5,378,262 and
5,447,552.
[0053] If the ion exchange resin is stripped with sulfuric acid,
the extractant for the cobalt and nickel separation can be selected
from phosphoric, phosphinic and thiophosphinic compounds.
Preferably, the extractant is selected from the group consisting of
bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272), bis
(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302), and
bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex 301). More
preferably, the extractant is bis(2,4,4-trimethylpentyl) phosphinic
acid (Cyanex 272).
[0054] The pH may be controlled at about 5 to 5.5 by addition of a
base, such as NaOH solution, during the extraction to neutralize
free acid liberated by cobalt extraction.
[0055] Virtually all of the cobalt can be extracted in this manner.
The term "virtually all" means that greater than 99%, preferably
greater than 99.8% of the cobalt can be extracted. A small portion
of the nickel is also extracted, but this can be "scrubbed" off the
loaded organic by contact with a strong cobalt solution, such as
the product strip liquor.
[0056] Interference by manganese, magnesium, and calcium, as well
as other trace impurities is virtually eliminated because of the
excellent purification against these impurities afforded by the
previous ion exchange process.
[0057] As shown in FIG. 1, the extraction process 20 (120)
separates the nickel and cobalt into a resulting pure nickel
solution 6 (106) and a cobalt-containing organic phase. The nickel
containing raffinate may be further processed such as by
electrowinning.
[0058] The cobalt-loaded organic solution is stripped with a strip
solution 5 to recover substantially pure cobalt solution. The strip
solution may be a mineral acid and can be selected from the group
consisting of sulfuric acid and hydrochloric acid. The resulting
pure cobalt solution 7 (107) can be further processed such as by
electrowinning.
[0059] In a preferred embodiment of the above solvent extraction
process, best seen in FIG. 2, the cobalt-loaded organic solution is
stripped with spent electrolyte 141 from a subsequent cobalt
electrowinning step 140. This spent electrolyte contains one mole
of sulfuric acid for each mole of cobalt electrowon. This is the
quantity of sulfuric acid required by the organic stripping
reaction, thus allowing the electrowinning circuit to operate in
closed circuit with the cobalt solvent extraction circuit.
[0060] As also shown in FIG. 2, the resulting pure nickel solution
106 is further processed by electrowinning 130. The spent
electrolyte 131, with some concentrated sulfuric acid added as
make-up, is used as the ion exchange strip solution 131.
[0061] The following examples illustrate, but do not limit, the
present invention. Unless otherwise indicated, all parts and
percentages are by weight.
EXAMPLE 1
[0062] This example illustrates the problem of contacting the feed
solution (resulting from acid leach) with an organic phase
containing the extractant, Cyanex 272. Typically, after sulfuric
acid pressure leaching and limestone neutralization for ferric iron
removal, a laterite leach solution would contain metal sulfates, as
5-8 g/l Ni, 3-20 g/l Mg, 1-4 g/l Mn, 0.5-2.0 g/l Co and 0.2-4.0 g/l
Al. FIG. 3 shows that co-loading of Mn and Co will occur, because
the Mn and Co extraction curves are very close to each other.
Because of the high Mn to Co ratio (3:1) in laterite leach liquor,
Mn will load in preference to cobalt. Therefore, Cyanex 272 is not
suitable for the direct treatment of the laterite leach liquor
(feed solution) to separate cobalt from other impurities in the
leach liquor.
EXAMPLE 2
[0063] This example shows the co-loading of impurities with cobalt
in an organic phase containing the extractant, Cyanex 272. Using an
acid leach liquor, iron was oxidized with hydrogen peroxide,
neutralized to pH of 5.8 to precipitate all iron, and filtered
prior to the experiment. The feed solution was mixed for 5 minutes
with different volumes of 15% v/v Cyanex 302 in kerosene (Philips
Orfom SX12) in a baffled beaker at a total volume of 120 ml. The
phases were allowed to separate after mixing and then an aqueous
sample was taken. The experiment was done at room temperature,
controlling the pH by the addition of 0.5N NaOH to obtain a final
pH of 5.0. The composition of the feed solution and raffinate is
shown in Table 5.
5TABLE 5 Aqueous concentration for Cyanex 272 shake-out test Co/
O:A Ca Co Mg Ni Fe Mn Zn Ni Solution ratio g/l g/l g/l g/l g/l g/l
g/l sep. Feed 0.60 7.45 0.17 9.23 0.001 0.086 0.400 n.a. Raf- 1
0.55 1.67 0.16 9.08 <.001 0.006 <.001 210 finate 5 0.21 0.11
0.06 8.45 <.001 <.001 0.001 723 10 0.09 0.04 0.03 7.88 0.002
<.001 <.001 1081
[0064] The experiment shows a good separation between cobalt and
nickel, but a poor separation between manganese and cobalt. It also
shows the co-loading of other impurities, such as calcium and
magnesium, with the cobalt. This shows that Cyanex 272 is not
suitable for the direct treatment of the laterite leach liquor to
separate cobalt from other impurities in solution.
EXAMPLE 3
[0065] This example illustrates the degradation of thiophosphinic
acid in the presence of iron sulfate. An aqueous cobalt/iron
sulfate solution was mixed for 5 minutes with an equal volume of
10% v/v Cyanex 302 in kerosene (Philips Orfom SX12) in a baffled
beaker. The phases were allowed to separate and then the organic
was contacted with a fresh aliquot of the feed solution. The
experiment was done at room temperature, maintaining the pH at 3.5
by the addition of 0.9N NaOH. This was repeated eight times, so
that the organic was contacted nine times with the same
concentration feed solution. The composition of the feed solution
and raffinate is shown in Table 6.
6TABLE 6 Aqueous concentration for Cyanex 302 shake-out test Co Fe
Fe.sup.2+ Solution Contact g/l g/l g/l Feed 2.25 4.22 3.89
Raffinate 1 1.98 3.82 3.85 2 1.83 3.75 3.64 3 1.66 3.73 3.61 4 1.47
3.49 3.48 5 1.32 3.28 3.24 6 1.16 3.06 3.00 7 1.15 2.57 2.54 8 1.06
2.17 2.28 9 0.95 1.88 1.89
[0066] The data show how the iron content gradually decreased to
3.06 g/l after six contacts. In the next three contacts, there was
substantial precipitate formation, while decreasing the iron
content to 1.88 g/l. The precipitate, thoroughly washed to remove
any entrained organic, was analyzed to find elemental sulfur and
phosphorous, indicating the chemical degradation of the
extractant.
EXAMPLE 4
[0067] This example illustrates the instability of
monothiophosphinic acid and the conversion to dithiophosphinic acid
in the presence of iron sulfate in continuous multi-stage
counter-current solvent extraction operation. An aqueous sulfate
solution containing, 0.74 g/l iron(II), 0.08 g/l iron(III), 3.65
g/l nickel(II), 0.38 g/l cobalt(II), 1.65 magnesium(II) and 1.54
g/l manganese(II), and having a pH of 5.0 at a temperature of
23.degree.C., was contacted in a counter-current fashion in two
consecutive extraction stages at a flow-rate of 78 ml/min with a 10
vol % solution of Cyanex 302 extractant in kerosene (Philips Orfom
SX12). The organic flow rate was 33 ml/min, which gives an A/O
ratio of 2.4. Sodium hydroxide at 0.2 N was added to maintain the
pH at 4.5. The loaded organic solution was contacted in a
counter-current fashion in two consecutive scrubbing stages with a
bleed stream from the cobalt eluate. The cobalt eluate flow rate
was 1.5 ml/min with an aqueous recycle of 15 ml/min, to maintain an
A/O ratio of 0.5. The scrubbed organic was contacted in a
counter-current fashion in three consecutive stripping stages. The
strip solution contained 22.5 g/l cobalt(II), 0.03 g/l iron(II),
0.04 g/l nickel(II), and 10 g/l sulfuric acid and was fed to the
stripping stages at a flow-rate of 12 ml/min. After five hours, the
continuous operation was stopped because of the formation of crud
and poor metal loading. The composite eluate contained 27.8 g/l
cobalt(II), 0.16 g/l iron(III), 2.85 g/l manganese(II), and 0.22
g/l nickel(II) at pH of 3.23. Elemental sulfur crystals were
recovered from the organic storage container and the
mixers/settlers. Chemical analysis by the manufacturer showed that
over 90% of the original extractant, Cyanex 302, had converted to
Cyanex 272. This would explain the manganese loading, because
Cyanex 272 has greater affinity for manganese than cobalt.
EXAMPLE 5
[0068] This example illustrates the scavenging of copper with a
chelating resin. As shown in Table 3, copper has higher affinity to
XFS 4195 than nickel and cobalt. After SAPL leaching, there is
copper in the leachate, though typically less than 100 mg/l. To
prevent loading of this trace amount of copper on the XFS 4195 and
contamination of the ion exchange eluate with copper, an ion
exchange scavenging step for copper is used ahead of Ni and Co ion
exchange. SAPL leachate was passed through a 200 ml IRC718 column
at 60-70.degree. C. at a flow rate of 12-30 bed volumes (BV) per
hour. The feed and raffinate composition is shown in Table 7.
7TABLE 7 Results for single column tests for copper scavenging with
IRC718 pH Cu (mg/l) SAPL Leachate 1 Feed solution 1.9 106 Raffinate
(45 BV) n.a. 0.8 SAPL Leachate 2 Feed solution 1.5 45 Raffinate (10
BV) n.a. 0.0
EXAMPLE 6
[0069] This example describes the results from single column XFS
4195 extraction of nickel and cobalt with rejection of manganese,
magnesium, calcium, aluminum, chromium, and iron(II). A synthetic
laterite leach solution was prepared. The composition of this
solution is typical for sulfuric acid pressure leaching, followed
by limestone neutralization for iron removal and scavenging of
copper with the ion exchange resin IRC718. In this experiment, the
nickel and some cobalt were extracted from solution in preference
to other impurities, especially manganese. A single column with 200
ml XFS 4195 resin (1 Bed Volume) was used at ambient temperature,
passing the feed solution at 15 BV/hr. A total of 2.4 liters (12
Bed Volumes) of feed solution were passed through the column. A 100
g/l sulfuric acid solution was used for stripping at 6 BV/hr. A
total of 1.6 liters (8 Bed Volumes) of sulfuric acid solution were
used to strip the column. After collection of each bed volume, a
small liquid sample was taken. At the end, all individual samples
were combined for the overall raffinate or eluate bulk sample.
After loading and stripping, the resin was washed with DI water.
Table 8 shows the composition of feed solution, raffinate and
eluate for this single-column test. The selectivity of the resin
for nickel and cobalt over chromium(III), aluminum, magnesium and
manganese(II) is clearly demonstrated.
8TABLE 8 Concentration profile for single-column test Bed Al Co Cr
Fe Mg Mn Ni Solution Volume mg/l mg/l mg/l Mg/l mg/l Mg/l mg/l Feed
253 585 114 6 5087 1742 6532 Al Co Cr Fe Mg Mn Ni Raffinate 1 0 0 0
0 11 3 16 2 23 0 11 0 1893 555 0 3 245 0 57 0 4771 1672 0 4 274 0
97 1 5108 1840 0 5 281 40 120 9 5034 1789 1 6 285 777 130 7 5141
1841 6 7 273 1010 114 4 5038 1801 32 8 272 839 111 4 5013 1752 177
9 266 728 108 3 4943 1730 406 10 259 733 114 4 5132 1779 1000 11
274 721 112 4 5128 1798 1940 12 268 723 113 4 5164 1820 3318 Al Co
Cr Fe Mg Mn Ni Overall Raffinate 227 464 91 3 4365 1532 575 Al Co
Cr Fe Mg Mn Ni Eluate 1 0 10 2 0 1 0 142 2 0 34 2 0 0 0 5802 3 0 65
3 4 0 0 26850 4 0 14 1 0 0 0 15260 5 0 0 0 0 0 0 3460 6 0 0 0 0 0 0
1192 7 0 0 0 0 0 0 429 8 0 0 0 0 0 0 214 Al Co Cr Fe Mg Mn Ni
Overall Eluate 0 15 1 1 0 0 6669
EXAMPLE 7
[0070] This example describes the continuous processing of
neutralized laterite leach solution for the recovery and
electrolytic production of cobalt and nickel. In continuous pilot
plant operation, limonitic laterite was pressure leached with
sulfuric acid at a throughput of 1.1 tpd, at 270.degree.C. and 0.27
ton of sulfuric acid per ton of ore, yielding about 93% nickel
extraction. The autoclave discharge leach solution was neutralized
with limestone, followed by liquid/solid separation in a six-stage
CCD circuit. Sodium metabisulfite was added to reduce hexavalent
chromium to Cr(III). The solution was subsequently passed through
an ion exchange fixed bed circuit with IRC 718 resin for copper
removal. This solution was used for the extraction of nickel and
cobalt in two ion exchange steps in a continuous pilot plant
operation for ten days. The average composition of the feed
solution and raffinate for the first ion exchange step with XFS
4195 is tabulated below:
9TABLE 9 Average feed and raffinate composition for Ni IX in mg/l
Al Ca Co Cr Cu Fe Mg Mn Ni Si Feed 1214 577 514 140 2.6 41 2949
1955 5085 90 Raf- 1021 419 362 116 0.0 19 2364 1513 940 71
finate
[0071] The raffinate from the nickel ion exchange step was
neutralized with limestone to a pH of 3.5 and the resulting gypsum
residue was removed by filtration. The filtrate solution was
subsequently passed through a second ion exchange stage with XFS
4195 to recover cobalt and remaining nickel, while rejecting the
major impurities. The composition of the feed (neutralized nickel
ion exchange raffinate) and final raffinate for the second ion
exchange step with XFS 4195 is tabulated below:
10TABLE 10 Average feed and raffinate composition for Co IX in mg/l
Al Ca Co Cr Cu Fe Mg Mn Ni Si Feed 996 495 359 110 19 13 2392 1466
975 78 Raf- 785 411 7 82 0 11 1906 1149 0 61 finate
[0072] The nickel and cobalt recoveries calculated from the
composition of the final raffinate were 100% and 97.5%,
respectively. Nickel electrolyte was used to strip the loaded resin
from the first ion exchanger. A dilute sulfuric acid solution was
used to strip the loaded resin from the second ion exchanger. The
compositions are tabulated below:
11TABLE 11 Average feed and eluate composition for Ni and Co IX in
mg/l Al Ca Co Cr Cu Fe Mg Mn Ni Si Ni strip feed (Ni electrolyte)
0.8 249 1.9 15 3.0 28 32 0.4 46604 48 Ni IX eluate (first
exchanger) 42 240 231 52 52 64 30 0.6 60540 47 Co IX eluate (second
exchanger) 12 3 1096 26 54 1 4 7 4138 7
[0073] Both eluate streams were combined and neutralized with soda
ash to a pH of about 5.5. The resulting residue with hydrolyzed
impurities was removed by filtration, prior to feeding to the
solvent extraction circuit. The solvent extraction (SX) circuit was
operated at 40.degree.C. with 10% Cyanex 272 in Philips Orfom SX11.
Sodium hydroxide at 0.5 N was used for neutralization in the
extraction stages. The composition of the neutralized ion exchange
eluate (SX feed) and SX raffinate is tabulated below:
12TABLE 12 Average Co SX feed and raffinate composition in mg/l Al
Ca Co Cr Cu Fe Mg Mn Ni Feed 1.6 281 2570 3.9 1.0 11.0 53 12 69500
Raffinate 0.0 273 2.5 0.0 0.1 2.0 35 0.1 65580
[0074] After the SX with Cyanex 272, a very pure nickel sulfate
raffinate was produced, suitable for the production of Class I
electrolytic nickel. The loaded organic was stripped with
acid-fortified cobalt anolyte to obtain a substantially pure cobalt
solution.
13TABLE 13 Average Co SX strip feed and eluate composition in mg/l
Al Ca Co Cr Cu Fe Mg Mn Ni Strip feed 7.0 94 40543 35 1.0 240 49 73
846 Eluate 10.8 93 72182 49 4.1 120 48 79 1073
[0075] Although the present invention has been described in
conjunction with preferred embodiments and examples, it is to be
understood that modifications and variations may be made without
departing from the spirit and scope of the invention. Such
modifications and variations are considered to be within the scope
of the invention and following claims.
* * * * *