Note: Descriptions are shown in the official language in which they were submitted.
1- 43-21-6146A
SOLVENT EXTRACTION OF COBALT USING
HYDROXAMIC ACIDS
BACKGROUND OF THE INVENTION
The present invention relates to hydro-
metallury. More particularly, it relates to the
extraction of cobalt metal values from aqueous solu-
tions by solvent extraction techniques employing
certain N-alkylalkanohydroxamic acids as extractants.
Further, it relates cobalt complexes of such alkano-
hydroxamic acids and organic solutions thereof.
Solvent extraction hydrometallurgy isemployed in industrial operations to recover valuable
metals. The key to implementing this t~chnology has
been the availability of suitable metal extractants.
Metal extractants, hereinafter extractants, are
organic ~oluble compounds that form organic soluble
complexes with metals which allow the transfer of the
metal values from an aqueous solution to an organic
phase containing the extractant in contact with the
aqueous solution, i.e., extraction, which can be
represented generally as follows:
Maq + E ~ ~ME (1)
Maq = metal in aqueous phase (A)
E = extractant in organic phase (B)
ME = metal complex in organic phase (B)
U~lwanted nonmetallic and, depending upon the
extractant and conditions employed, metallic
impurities are left behind in the aqueous phase (A)
which is discarded or further processed for recycle.
The metal in the organic phase ~B) is then recovered
by an aqueous stripping solution phase (C~ as follows:
ME ~ SS ~ MSS + E (2)
SS = aqueous stripping solution phase (C)
MSS= metal in stripping solution phase (C)
~,.:., ,
~2~65~
-2- 43-21-6146A
The method by which stripping is done
depends upon the nature of the extraction and the
metal involved. By the stripping process (2) the
extractant is regenerated and recycled repeatedly in
the extraction process. The metal, now concentrated
and purified in the aqueous stripping solution phase
(C) can be recovered by conventional methods.
Such solvent extraction processes for recov-
ering metal values are known. See, for example,
Kirk-Othmer, Encyclopedia of Chemical Technology,
Third Edition, Vol. 6 pp. 850-851, Vol. 9. pp.
713-714. U.S.P. 3,224,873 issued December 21, 1965 to
R. R. Swanson discloses a solvent extraction process
employing certain oxime extractants for the recovery
of copper. U.S.P. 3,276,863 issued October 4, 1966 to
J. L. Drobnick et al discloses the separation of
nickel and cobalt values using certain oxime
extractants. U.S.P. 3,821,351 issued June 28, 1974 to
M. F~ Lucid discloses certain N-substituted hydroxamic
acids useful as extractants for the recovery of
copper, molybdenum, uranium, iron and vanadium. More
recently, effurts have been directed to the extraction
of cobalt. For example, U.S.P. 4,196,076 issued April
1, 1980 to A. Fujimoto et al discloses a method of
extracting and separating cobalt from nickel using
monoesters of phosphonic acid. U.S.P. 4,210,625
issued July 1, 1980 to D. S. Flett discloses a method
for the separation of cobalt from nickel using an
ester of phosphoric acid by solvent extraction.
U.S.P. 4,348,367 issued September 7, 1982 to W. A.
Rickelton et al discloses a method of extracting
cobalt (II~ from its aqueous solution using an organic
soluble phosphinic acid.
Cobalt is a highly valued metal and aqueous
solutions containing cobalt metal values are obtained
from processes employed in the hydrometallurgy of
' '
~2~5~
-3- 43-21-6146A
ores, the recovery of cobalt and other metals from
spent catalysts and the reclaiming of cobalt and other
metals ~rom metal scrap. Cobalt occurs in ores that
bear nickel, magnesium, copper, lead and zinc.
It is known that cobalt metal values in
solution commonly exists as either Co(II) or Co(III)
and that these two oxidation states have widely
different chemistries when complexed by a ligand.
Ligands can be characterized as monodentate which are
capable of forming only one bond with the central
metal ion and as bidentate which coordinates through
two bonds from different par-ts of -the molecule or
anion. Co(II) can be converted to Co(III) in the
presence of air (oxygen source) depending on the type
of ligand used as a metal extractant. Further, it is
known that under oxidizing conditions, presence of
air, normally Co~II) converts to Co(III) when
complexed with a bidentate ligand or chelating agent,
i.e., one that bonds to metal ion throuyh at least two
atoms thereby, forming a chelate ring complex and that
the Co(III) chelate ormed is usually irreversible
i.e., not readily strippable~
In view of the formation of the ~o(III) com-
plexes under aerobic conditions with chelating agents,
; 25 such agents have not been employed in the solvent
extraction of metals from aqueous solutions containing
i cobalt. Examples of chelating agents known to form
irreversible cobalt (III) complexes in the presence of
air include the chelating metal extractants used in
hydrometallurgy such as the phenolic oximes, available
under the tradenames LIX, General Mills, Inc. ACORGA
P5000 series, ICI Corporation and SME-529, Shell
Chemical, and other known chelating agents, such as
ethylenediamine, acetylacetone, oxalic acid,
8-hydroxyquinoline, ethylenediaminetetracetic acid,
nitrilotriacetic acid and the like. Accordingly,
....
J~
~4~ 43-21-6146A
since monodentate extractants do not form irreversible
Co (III~ complexes such extractants, for example,
derivatives of phosphoric, phosphonic and phosphinic
acids, have been developed for the recovery of cobalt
in solvent hydrometallurgy.
In view of the much greater activity of che-
lating agents, such agents are more desirable than
monodentate extracts in solvent extraction
hydrometallurgy. It has now been discovered that
certain N-alkylalkanohydroxamic acid chelating agents
reversibly extract cobalt in the presence of air or
other oxidizing conditions. This unexpected activity
of this class of chelating agents provides an
efficient process for extracting cobalt from aqueous
solutions containi~g cobalt by solvent extraction.
Further, this invention provides an
effective means to recover cobalt and other valuable
metals such as nickel from aqueous feed solutions
containing cobalt and nickel metal values.
~0 These and other advantages of the present
invention will become apparent from the following
description.
SUMMARY OF THE INVENTION
The present invention provides a process for
extracting co~alt from cobalt bearing aqueous
solutions which comprises contacting said aqueous
solution with a hydrocarbon solvent comprising at
least 2~ by weight of N-alkylalkanohydroxamic acid
having a-t least about 8 carbon atoms to extract the
cobalt from the aqueous solution; separating the
hydrocarbon solvent cobalt loaded organic phase and
recovering the cobalt loaded organic phase.
Further, this invention provides a process
of extracting cobalt and other metals selected from
the group consisting of nickel, zinc, lead, copper and
~ . ,~.
~5~
-5- 43-21-6146A
magnesium from aqueous solution containing cobalt and
said other metals which comprises contacting said
aqueous solution with a hydrocarbon solvent comprising
at least 2% by weight of an N-alkylalkanohydroxamic
acid having at least about 8 carbon atoms to extract
the metals from the aqueous solution; separating the
hydrocarbon solvent metal loaded organic phase and
recovering the metal loaded organic phase.
The present invention also provides
processes, as described above, with the additional
steps of contacting the recovered metal loaded organic
solution with an aqueous stripping solution to recover
the metals from the organic phase; separating the
aqueous phase containing the water soluble metal
salts; and recovering the stripped organic phase for
subsequent reuse in the extraction of another aqueous
cobalt-bearing feed solution.
Also, the present invention provides a new
class of complexes comprising cobalt and
N-alkylalkanohydroxamic acid having at least about 8
carbon atoms and a solubility in a hydrocarbon solvent
of at least 2% by weight.
DETAILED DESCRIPTION OF_THE INVENTIOM
The N~alkylalkanohydroxamic acids can be
employed in accordance with this invention in liquid-
liguid extraction processes using columns or mixer-
settlers such as the reciprocating-plate extraction
column, pulse columns or columns employing rotating
impellers and the like.
The N-alkylalkanohydroxamic acid extractant
in accordance with this invention are of the type
R1C(O)N(OH)R2 where R1 and R2 are each linear,
branched or cyclo aliphatic groups. The useful
N-alkylalkanohydroxamic acids have a total of at
least about 8 carbon atoms, preferably not more than
about 30 carbon atoms, and a solubility of at least 2
... .
5~
-6- 43-21-6146~
by weight in a hydrocarbon solvent and substantially
complete insolubility in water (<300 ppm). Aromatic
groups and halogens can be present in Rl and R2
provided they do not alter signigicantly the
solubility of the extractant in nonpolar solvents and
do not interfere with the chelating ability of the
extractant.
It has been discovered that this class of
N-alkylalkanohydroxamic acids, which are chelating
extractants, reversibly extract cobalt (II) under
aerobic conditions. In addition, even if the cobalt
is oxidized to the cobalt (III) hydroxamate complex,
it still can be easily stripped. This unexpeçted
- reversibility provides a process using these chelating
extractants for the recovery and purification of
cobalt values and other metal values from aqueous
streams which also contain cobalt. This is very
desirable since chelating extractants are much more
selective than monodentate extractants. It opens up a
much wider operating pH range and removes the need for
complicated monodentate/bidentate synergisitc
mixtures. Also, it allows cobalt metal values to be
more selectively extracted away from gangue minerals,
such as Ca2 ion, which would normally co~extract in
monodentate extraction systems. Aqueous streams that
contain other metal values, such as nickel, zinc,
lead, copper and/or magnesium along with cobalt can be
processed by these N-alkylalkanohydroxamic chelating
extractants since the contained cobal~ will not
irreversibly complex the extractant.
In addition to the above described hydrox-
amic compounds the organic phase of the extractant
comprises a liquid hydrocarbon solvent. Such solvent
must be substantially water immiscible so as to be
~Z5~
-7- 43-21-6146A
separable from the aqueous solutions originally con-
taining the cobalt values. Suitable solvents include
aliphatic and aromatic hydrocarbons such as kerosene,
hexane, toluene, methylene chloride, chloroform,
carbon tetrachloride, xylene, naphtha, cyclohexane,
Chevron Ion Exchange solvent, Solvesso 100 and the
like. Kerosene and other distillates are preferred.
Generally, the hydroxamic compounds will be present in
the organic pha~e in an amount of at least about 2% by
weight. Preferably, the N-alkyl alkanohydroxamic
compound will be present in the amount of 2 to 25%,
more preferably about 5 to 20%, by weight based on the
total organic phase. Viscosity and/or solubility
serves to fix the upper limit of the content of said
hydroxamic compound which will depend upon the
structure of the compound employed. Normally, an
amount of about 15% by weight is employed although
amounts as high as 60% can be functional
The organic phase may also contain modifiers
which can be a long chain aliphatic alcohol, such as
isodecanol or phosphate esters, such as tributylphos-
phate. Modifiers serve to prevent third phase
formation, aid in phase disengagement and/or increase
extractant solubility in the hydrocarbon solvent. If
a modifier is used, it can be used in amounts of about
O.5% to 50%, or greater, by volume of the hydrocarbon
solvent, preferably about 5%.
In carrying out the process of this
invention the cobalt bearing agueous solution is
contacted batchwise or continuously with the
extractant solvent comprising at least 2% by weight of
the N-alkylalkanohydroxamic acid. The agueous feed
solution bearing cobalt can be adjusted to provide an
equilibrium pH in an appropriate range depending upon
the particular hydroxamic acid extractant employed.
For example, an equilibrium pH of at least 5 can be
,, .
-8- 43-21-6146A
employed for N-methyloctanohydroxamic acid extractant
and a pH of at least 7 can be employed for
N-isopropyldecanohydroxamic acid. More particularly,
an equilibrium pH in the range of 7 to 11 is
advantageous employing the N-alkylalkanohydroxamic
acid extractants to ~xtract cobalt. Preferably the
equilibrium pH for cobalt bearing acidic feed streams
is adjusted to a pH in the range of 7 to 8. The
volume ratio of the aqueous phase to the organic phase
should be selected to most effectively remove the
cobalt from the agueous phase. Aqueous phase to
organic phase volume ratios of from 1:20 to 20:1 are
believed to be effective, although other ratios may
prove effective depending upon the specific charac-
teristics of the solvent extractant and the cobaltbearing aqueous solution employed. Phase contact can
be achieved using, for example, mixer-settlers. In
the mixer, one phase is dispersed within the other by
stirring or some other suitable means of agitation;
The extractant forms a complex with the cobalt within
the organic phase of the two-phase liquid mixture.
The dispersion then flows to the settler where phase
disengagement occurs under quiescent conditions.
Generally, extraction can be carried out at
temperatures in the range of 0C to 80C or more,
preferably in the range 15 to 60C.
It may be desirable to scrub the cobalt-
loaded organic phase to remove co-extracted metal ions
to achieve the desired purity depending on the parti-
cular cobalt bearing aqueous feed solution employed.This is achieved by washing the cobalt loaded solvent
with water or an a~ueous solution of a cobalt salt.
The cobalt values extracted from the aqueous
feed solution into the organic phase can be stripped
from the loaded organic phase by contacting it with
about 0.05 -10 parts by volume, preferably about 0.5 -
-9- 43-21-6146A
2.0 parts by volume, of an aqueous solution at 0 -
80C, preferably about 15 - 60C. The aqueous
solution used for stripping the loaded organic phase
can be a solution of a mineral acid or ammonia.
Suitable mineral acids include sulfuric, hydrochloric,
hydrofluoric, nitric and the like. The preferred
mineral acid solution is sulfuric acid containing
about 1-300 grams of sulfuric acid per liter,
preferably about 30-100 grams per liter. Suitable
aqueous ammonia solutions are solutions containing
50-300 grams ammonia per liter, preferably about
100-200 grams per liter. Phase contact with the
stripping solution can be achieved with
mixer-settlers, or other suitable devices. In this
manner the cobalt is recovered fro~ the organic phase
into the stripping solution as a cobalt salt. The
cobalt-bearing stripping solution can be treated by
conventional means to recover cobalt metal, for
example, by hydrogen reduction.
The stripped cobalt-free solvent extractant
is recycled to the extraction circuit for treatment of
additional aqueous feed solutions bearing cobalt.
In carrying out the present process with
aqueous feed solutions containing cobalt and other
valuable metals such as nickel, advantage can be taken
of the unique property of some of the present
extractants to form strippable Co (III~ complexes
under oxidizing conditions. In this manner the
selected extractant will form the cobalt (III) complex
along with the other valuable metal co~plex in the
extraction process which enhances preferential
stripping of o~ne metal over the other in view of the
different stripping characteristics of this cobalt
complex and the other metal complex under the selected
stripping condition. This provides a means of
-10- 43-21-6146
obtaining very pure cobalt with a minimu~
number of extraction stripping cycles.
The present invention also relates to the
cobalt complexes of the N-alkylalkanohydroxamic acids
and to the organic solvent solutions thereof.
The term cobalt complex of the N-alkylalkanohydroxamic
acid is meant to include compositions of the N-alkyl-
alkanohydroxamic acid having at least about 8 carbon
atoms combined with significant amounts of cobalt in
either the Co (II~ or Co(III) ionic states. Said
solutions thereof comprise the hydrocarbon solvent and
at least 2% by weight of the cobalt complex of the
N-alkylalkanohydroxamic acid. In addition to using
these cobalt complexes in the above described
processes for recovering cobalt from aqueous leach
solutions, these complexes can be used as a source of
very pure cobalt for various applications such as the
preparation of cobalt catalysts and cobalt supplements
for ruminant animals. These cobalt complexes when
isolated from the solvent are colored materials in the
form of a solid, semi solid, or oily liquid. For
e~ample, the N-isopropyldecanohydroxamic acid cobalt
complex is a dark green oil, the N-methyldecano-
hydroxamic acid cobalt(III) complex is a dark purplish
brown solid and the N-methyldecanohydroxamic acid
acid cobalt(II) complex is a rose colored solid. For
convenience o recovery, these complexes were prepared
by contacting the hydroxamic extractant in a volatile
organic solvent such as methanol, ethanol, petroleum
ethex and the like with a cobalt source, such as
CoSO4~7H20, to form the complex and isolating the non-
volatile complex by removing the solvent through evap-
oration. For example, the N-methyldecanohydroxamic
,
, ,
~2~.,5~
~ 43-21-614~A
complex was prepared by dissolving 4.02 grams of the
hydroxamic acid in 300 ml of methanol in a 500 ml
flask fitted with a stirrer. With stirring, 2.81
grams of CoSO4~7H20 were added along with 1.68 grams
of NaHCO3 to neutralize the hydrogen ions produced
when the hydroxamic acid complexes the cobalt. The
mixture was stirred about 20 hours, filtered and the
methanol was removed from the filtrate by
roto-evaporation at 40C and drying in a vacuum oven,
12 hours at 30C, 24 hours at 22C, to provide a rose
colored solid product represented by the formula
00
i"
[Co(CgHlgCNCH3)2(CH30H)2]~4H20 Elemental analysis:
Found: Co 9.84; C 48.20; H. 9.01; N 4.88
Calculated: Co 9.89; C 48.39; H 10.15; N 4.iO
The solvent of crystallization can be removed by more
vigorous drying conditions.
Methods of preparing the N-alkylalkano-
hydroxamic acids are known. Such compounds can be
prepared by the reaction of a N-alkylhydroxyamine with
a carboxylic acid chloride. For example, N-hexyl-
decanohydroxamic acid is prepared by the dropwise
addition of a solution containing 0.064 moles of
decanoyl chloride in about 250 ml of methylene
chloride to a stirred 2 liter reaction flask charged
with 0.064 moles of N-hexylhydroxylamine and 700 ml of
methylene chloride maintained at about -25C with a
dry ice bath. ~fter all the decanoyl chloride is
added, 0.04 moles of triethylamine in about 250 ml of
methylene chloride is added to remove the HCl by-
product. The reaction mixture is quenched with 10 ml
of glacial acetic acid and is washed with five 500 ml
portions of water. The organic reaction mixture is
dried with calcium sulfate and the methylene chloride
solvent is removed by rotary evaporation leaving an
oily liquid which is allowed to solidify at -20C is
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~5~
-12- 43-21-6146A
recrystallized in ethyl acetate and dried to provide
N-hexyldecanohydroxamic acid having a melting point of
37C.
This invention is further illustrated by,
but not limited to, the following examples wherein all
percentages and parts are by weight unless otherwise
indicated.
ExAMæLE 1
This example demonstrates the type of cobalt
complexes formed using representative N-alkylalkano-
hydroxamic acids. A hydrocarbon solution of the
N-alkylalkanohydroxamic extractant, about 0.05 - 0.08
molar concentration, was prepared usin~ a mixture of
95% kerosen~ and 5% isodecanol (by volume) as the
hydrocarbon solvent for each extractant except for the
less soluble N-(1-nonyldecyl) cyclohexanohydroxamic
acid for which a 50/50 kerosene/isodecanol mixture (by
volume) was used. The N-hexylpentanohydroxamic acid
extractant solution was prepared at 1.75 molar
concentration. An aqueous cobalt (II~ nitrate
solution was prepared containing 0.1941 g/1 (0.003294
M) cobalt (II). Two ml of the aqueous solution were
contacted with 2 ml of the organic solution of the
extractant by shaking in a test tube. The pH of the
mixture was increased to pH 8.5 by adding 3 ml of 0.1
M NaHC03 solution in increments with vigorous
agitation after each addition. The agueous phase was
then analyzed for remaining un~xtracted cobalt (II).
In each case over 98% of the cobalt was e~tracted.
The type of cobalt compleges prepared are shown in
Table A.
i
~ ~5~52
-13- 43-21-6146A
TABLE A
EXTRACTANT COBALT COMPLEX
N-ALKYLALKANO- Co-OXIDA-
HYDROXAMIC ACID HA/Co* TION STATE
N-methyloctanohydro-
amic acid 2/1 + 2
N-methyl-2-ethylhexano-
hydroxamic acid 3/1 ~ 2/1** + 3 -~ +2**
N-methyldecanohydrox-
amic acid 2/1 ~ 2
N-methylneotridecano
hydroxamic acid 3/1 -~ 2/1 + 3 -~ +2
N-methylhexadecanohydrox
amic acid 2/1 + 2
N-hexyldecanohydrox-
: amic acid 2/1 + 3
N-hexylpentanohydrox-
amic acid 2/1 + 3
N cyclohexyldecanohydrox-
amic acid 3/1 + 3
N-isopropyldecanohydrox-
~mic acid 2/1 -3 3/1 + 3
:~ N~ nonyldecyl)cyclo-
hexanohydroxamic acid 3/1 + 3
*HA/Co is the ratio of hydroxamate anions to Co
cations, the 2/1 Co(II) complex is pink, the 2/1 Co
(III) complex is yellow-brown and the 3/1 Co (III)
complex is green.
**Converts on standing as indicated by the symbol-~.
The following examples demonstrate the
extraction of co~alt from a cobalt bearing aqueous
solution and the readily reversible extraction/
stripping properties of the cobalt complex formed
using the N-alkylalkanohydroxamic acid extractants.
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-14- 43-21-6146
EXAMPLE 2
Ten ml of aqueous 1.94 g/1 Co were added to
20 ml water in a 125 ml flask. The pH was 5.03. To
this solution was added 10 ml of 10% by weight
N-methyloctanohydroxamic acid in kerosene. With
mixing, 0.170 ml of 2.5 N NaOH was added to bring
the pH to 7.12. During NaOH addition, the organic
phase turns pink and the aqueous phase loses its pink
color which is indicative of the cobalt being extracted
from the aqueous solution into the organic phase by
N-methyloctanohydroxamic acid. Analysis of the organic
phase showed that 98% of the cobalt had been extracted.
Over a 17 minute period the organic phase took on the
green color of oxidized cobalt, Co(III). Analysis of
the organic phase indicated that all of the cohalt
remained in the organic phase. The pH of the aqueous
phase was 7.23. Adding 1.0 N H2SO4 the pH was lowered
to 3.76, and the phases were mixed. Analysis showed
that 96% of the cobalt returned to the aqueous phase
from the organic phase within a few minutes. This
illustrates that the cobalt can be stripped rapidly
from the organic phase even though it is present as
the normally inert Co(III) species. The effect of the
presence of an oxidizing agent on the reversibility of
the Co(III) species was demonstrated by adjusting the
pH to 5.83 with 2.5 N NaOH and adding ten drops of 30%
H202 with stirring. The green Co(III) complex formed
immediately in the organic phase. The pH of the
aqueous phase was lowered to 3.5 using 1 N H2SO4 with
mixing and sample analysis showed tha~ about 55% of
the cobalt was quickly stripped from the organic phase
and 83% had stripped after a few minutes illustrating
that cobalt is readily stripped in the presence of a
strong oxidizing agent.
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-15- 43-21-6146A
EXAMPLE 3
An aqueous solution was prepared by mixing
10 ml of an aqueous solution containing 1.94 g/1
cobalt with 25 ml water containing 0.35 g KNO3. An
organic solution was prepared by mixing 1.44 g
N-isopropyldecanohydroxamic acid with 25 ml of
kerosene containing 5.0 vol. % isodecanol. The
aqueous and organic solutions were blended and the pH
was increased to 7.92 by slowly adding 1.0 M KOH. The
organic phase turned green and remained so on standing
for wee~s illustrating that the Co (III~ complex
formation can be permanent. Two 1 ml portions of the
cobalt loaded organic phase were taken. One portion
was stripped with 5 ml of 120 g/l ammonia solution
(NH3/~H4=2) 11.5 pH and the other was stripped with 5
; ml of dilute sulfuric acid,1 pH. In each case the
cobalt stripped completely over a period of hours
demonstrating that even after standing for weeks, the
Co(III) can be stripped from the organic phase with
stripping solutions having a wide pH range.
EXAMPLE 4
The strippability of representative N-alkyl-
alkanohydroxamic acids were compared using the follow~
ing procedure. Organic solutions of the HA/Co complPx
as prepared in Example 1 were isolated. The organic
phase was stripped by blending 2 ml of the organic
phase with 2 ml of 0.01 N H2SO4 (pH 2.1) and shaking
on a shaker bath at ambient temperature for 10
minutes. The aqueous strip solutions were then
analyzed for cobalt. The stripping results using
these conditions are set forth in Table B.
.. . .
~Z56~i~
-16- 43-21-6146 A
TABLE B
HYDROXAM I C AC I D % COBALT
RUN SOLUTION STRIPPhD
a. N-methyldecanohydroxamic acid 77
b. N-isopropyldecanohydroxamic acid 56
c. N-cyclohexyldecanohydroxamic acid 44
d. N-(l-nonyldecyl) cyclohexanohydroxamic0*
e. N-hexyldecanonhydroxamic acid 90
f. N-hexylpentanohydroxamic acid 80**
g. N-methylneotridecanohydroxamic acid 63
h. N-methyl-2-ethylhexanohydroxamic acid 47
* 12% stripped using 3 N H2SO4
** Extractant 1.75 molar concentration
The following examples demonstrate the
15 ability of N-alkylalkanohydroxamic acids to extract
cobalt and release, by stripping, the cobalt in the
presence of other metals.
EX~MPLE S
An a~ueous solution was prepared by mixing
10 ml of water with 10 ml of an agueous solution of
1. 94 g/l Co and 10 ml of an aqueous solution of 2.14
g/l Ni. The pH of the solution was 5.5. An organic
solution was prepared by adding 4.0 g of
N-methyldecanohydroxamic acid with 36.0 g of a 95%
kerosene/5% isodecanol (V/V) mixture. The aqueous
solution and the organic solution were blended at
25C. The pH of the aqueous phase dropped to about
4.5 after blending and the pE was adjusted slowly with
2.5 N NaOH to 7.77. The organic phase took on the
green color of the Co(III) complex. To accelerate
oxidation of the cobalt air was passed through the
mixture for 15 minutes using a gas dispersion tube.
Th~ phases were allowed to separate and analysis indi-
cated that 99.1% of each of the cobalt and nickel had
been extracted. The organic phase was isolated and 25
microliters of 30% H202 were added to complete the
~2~ i2
-17- 43-21-6146A
oxidation of cobalt. The organic phase was stripped
by blending with seven 10 ml portions of a pH 2 buffer
solution of 0.lM KC1/HCl within about 6 minutes.
Analysis showed that 22.6% of the cobalt and 72.3% of
the nickel remained in the organic phase demonstrating
that the Co(III) stripped faster than the nickel at
the mild stripping condition of pH 2.
The organic phase was then stripped by
blending with 10 ml of 300 g/1 H2SO4 (pH about 0)
overnight. The green color of Co(III) depleted very
rapidly upon contact with this stripping solution.
Analysis showed that 99.6% of the total cob~lt had
been stripped. Also 99.7% of the total nickel was
stripped showing utility for recovering nickel in the
presence of cobalt which strips more rapi~ly than the
nickel.
EXAMPLE 6
An organic solution and an aqueous solution
were prepared in the same manner as Example 5. Ten
molar NaOH was added slowly over a 20 minute period to
adjust the pH to 7.23. Analysis showed that 99.1% of
the cobalt and 99.2% of the nickel had been extracted
into the organic phase. To the organic phase was
added 0.10 ml of 30% H202 and the solution was mixed
thoroughly for one minute. The solution took on the
dark green color of Co(III~. About 25 ml of an
aqueous solution containing 160 g/l NH3 with NH3/NH4 =
2 (pH 11.5) was added and the phase mixed for about 20
seconds. The phases were allowed to separate.
Analysis showed that 90% of the cobalt and 83% of the
nickel had been stripped from the organic e~tractant
phase. This demonstrates that cobalt is easily
stripped even in the presence of a strong oxidant at
high pH and that nickel can be simultaneously
recovered.
~$~
-18- 43-2l-6l46A
EXAMPLE 7
N-isopropyldecanohydroxamic acid was
di~solved in kerosene containing 5~ by volume
isodecanol as modifier to provide a concentration of
0.07312 M (16.77 g/1). Twenty ml of this organic
solution were contacted with 22 ml of an aqueous
solution containing 0.1765 g/1 ~0.002995 M) of cobalt
and 0.1943 g/1 (0.003309 M) of nickel as their nitrate
salts. The agitated mixture was held at 50C and the
pH was adjusted slowly to 10.3 with 1.0 M potassium
hydroxide fully extracting the cobalt and the organic
phase became darker green. After sitting overnight at
ambient temperature, the two phases were isolated and
the organic phase was stripped by mixing vigorously
with 20 ml O.OlN sulfuric acid (pH 2.1) for 5 minutes.
The aqueous strip solution was analyzed for both
cobalt and nickel; it contained 0.11 g/1 of cobalt and
0.16 g/1 of nickel. Thus, 67% of the cobalt and 88%
of the nickel had been stripped. The organic phase
was isolated from the strip solution and washed 3
times with 20 ml of water in a separatory funnel to
remove any entrained nickel. A 3 ml ali~uot was
removed and the oryanic phase was blended with 20 ml
of 0.01 N sulfuric acid stripping solution (pH 2.1)
for 30 minu-tes at ambien~ temperatures. The aqueous
strip solution was analyzed for cobalt and nickel
which were found to be present in concentrations of
0.028 g/1 cobalt and less than 2 x 10 6 g/1 nickel.
The purity of the cobalt is greater than 99.99% which
is better than analytical reagent grade cobalt. The
yield of the pure cobalt was about 18%. Thus, cobalt
can be separated from nickel and obtained in better
than 99.99% purity by preferentially stripping the
nickel from the cobalt and recovering high purity
cobalt. To ~uantify the degree to which the cobalt
had been separated from the nickel by the second
~2~5~i5~
-lg- 43-21-6146A
stri~ping process a separation factor defined as
~Colf/[Ni]f
[Co]i/[Ni]i where the subscripts i and f denote the
initial and final aqueous concentrations,
respectively, was determined. The separation factor
for this example was 15,420.
EXAMPLE 8
The procedure in Example 7 was repeated with
the following modifications. The initial aqueous
solution volume was 20 ml. The cobalt and nickel con-
centrations were 0.1941 g/1 and 0.2137 g/1
rPspectively. Concentrated ammonium hydroxide was
used to adjust the pH to 10. The organic phase was
isolated and stripped with 23.2 ml of 0.01 N sulfuric
acid (pH 2.1) for 5 minutes during which air was
bubbled through the mixture. After the 5 minute
strip, the organic phase was isolated and scrubbed 3
times with 10 ml of 20.751 g/l cobalt (II~ agueous
solution containing about 0.03 g/1 nickel. The
scrubbed organic phase was then stripped at pH 1.2
for 30 ~inutes with 20 ml of 0.1 N H2SO4. Analysis of
the initial 5 minute strip showed 0.075 g/1 of cobalt
and 0.137 g/1 of nickel or only about 45% of the
cobalt was stripped. The concentrations of cobalt and
nickel in the final strip solution were 0.197 g/1
cobalt and 0.00017 g/l nickel. SomP of the cobalt was
gained from scrubbing with the concentrated cobalt
solution. The yield of cobalt from the initial
aqueous solution is about 55%. The separation factor
is 1276 and the percent purity of cobalt is 99.91%.
EXAMPLE 9
; An aqueous solution was prepared by mixing
10 ml of water with 10 ml of 1.94 g/1 cobalt and 10 ml
of 2.14 g/1 nickel. This a~ueous solution was con-
tacted with 4Q ml of an organic solu~ion of 95%
kero~ene 5% isodecanol (V/V) containing 10% by weight
~5~
-20- 43-21-6146A
N-methyldecanohydroxamic acid. The mixture was
agitated and the pH was adjusted to 7.77 by the addi-
tion of 2.5 N NaOH dropwise over a 30 minute period.
About 99% of the nickel and the cobalt were extracted
into the organic phase. The organic phase was iso-
lated and stripped by blending with Fisher brand pH Z
buffer (0.05 M KC1/HC1) solution and agitated for
about 6 minutes. The phases were allowed to separate
and upon analysis the organic phase contained 23% of
the cobalt and 72% of the nickel illustrating
preferential recovery of cobalt in the presence of
nickel.
The N-alkyl alkanohydxoxamic acid extrac-
tants can be employed to separate cobalt from metals
other than nickel.
The procedures set forth in the above
Examples for separating cobalt from aqueous solutions
also containing nickel are also applicable for the
separation of cobalt from other metals such as copper,
zinc, lead or magnesium.
In view of the foregoing description one
skilled in the art of extractive hydromettalurgy
techniques can by routine evaluation select the proper
N-alkylalkanohydroxamic acid extra~tant and stripping
procedures -to recover cobalt from various aqueous feed
streams bearing cobalt.
Although the invention has been described in
texms of speci~ied embodiments which are set forth in
considerable detail, it should be understood that this
is by way of illustration only and that the invention
is not necessarily limited thereto since alternative
embodiments and operating techniques will become
apparent to those skilled in the art in view of the
disclosure. Accordingly, modifications are contem-
plated which can be made without departing from thespirit of the described invention.
