Primary Examiner-Herbert T. Carter
Attorney, Agent, or Firm-Darby & Darby
Beamish, "Tantala", vol. 14, 1967.
Faye et aI., "Anal. Chern.", vol. 35, 1963, pp. 985-988.
3,960,549 6/1976 MacGregor 75/101 BE
3,979,207 9/1976 MacGregor 75/101 BE
FOREIGN PATENT DOCUMENTS
2,457622 6/1975 Fed. Rep. of Germany 423/22
OTHER PUBLICATIONS
United States Patent [19]
Baltz et al.
[54] PROCESS FOR THE SEPARATION OF
PLATINUM GROUP METALS
[75] Inventors: John Baltz, Lakewood; Enzo
Coltrinari, Arvada, both of Colo.
[73] Assignee: PGP Industries Inc., Santa Fe
Springs, Calif.
[ *] Notice: The portion of the term of this patent
subsequent to Mar. 15, 1994, has been
disclaimed.
[21] Appl. No.: 750,738
[22] Filed: Dec. 15, 1976 [57]
[11]
[45]
ABSTRACT
4,107,261
* Aug. 15, 1978
Related U.S. Application Data
[63] Continuation of Ser. No. 629,879, Nov. 7, 1975, Pat.
No. 4,012,481.
[51] Int. CI.2 COIG 55/00
[52] U.S. CI. 423/22; 75/101 BE;
423/658.5
[58] Field of Search 423/22, 658.5;
75/101 BE
[56] References Cited
U.S. PATENT DOCUMENTS
3,787,554 1/1974 Ziegler 423/22
3,823,220 7/1974 Donauna 423/22
Disclosed herein is a process for the separation and
recovery of Rhodium values from aqueous mineral acid
solutions also containing Iridium and/or Ruthenium
which comprises contacting the metal bearing aqueous
solution with a water immiscible organic solvent containing
an organically substituted quaternary amine salt
to extract Iridium and Ruthenium into the solvent phase
leaving Rhodium in the aqueous raffinate. The loaded
organic phase is stripped of Iridium and Ruthenium in
two sequential steps by contacting it first with an alkaline
solution then redissolving the resulting precipitate
in an acidified reducing solution.
6 Claims, No Drawings
2
aqueous raffinate phase. After phase separation, Iridium
and Ruthenium are simultaneously stripped and recovered
from the loaded organic by sequential contact with
predetermined stoichiometric quantities of an alkaline
5 solution and an acidified reducing solution.
It is accordingly an object of the present invention to
provide a highly selective process for separating Rhodium
from aqueous solutions containing Iridium, Rhodium
and Ruthenium.
Another aspect of the invention is a method for separating
Rhodium from an aqueous solution also containing
Ruthenium and Iridium by extracting the Iridium
and Ruthenium into an organic phase containing a substituted
quaternary ammonium compound.
A further aspect of the present invention involves the
method of stripping and recovering the Iridium and
Ruthenium complex from the loaded amine organic
phase by sequential treatment with predetermined stoichiometric
quantities of an alkaline solution and an
acidified reductant stripping solution.
These and other aspects of the present invention are
more completely explained in the following specification
and examples.
According to the present invention, cationic Rhodium
is separatedJrom an aqueous mineral acid solution
containing cationic salts of Rhodium as well as Iridium
and Ruthenium in their anionic oxidized state by solvent
extraction with an organically substituted quaternary
ammonium salt. Contacting the aqueous solution with a
solvent containing the quaternary amine leads the Iridium
and Ruthenium values to form a complex with the
amine that is preferentially soluble in the solvent phase,
leaving Rhodium in the aqueous raffinate. As used in
the present invention, the term "raffinate" refers to an
aqueous solution (or phase) after solvent extraction, i.e.,
a solution that has been depleted of all or part of its
valuable metal content by transfer to an organic phase.
The Rhodium, which must be present in the mineral
acid solution in its cationic state, is not extracted into
the amine solvent, and is won from the aqueous raffinate
by conventional processes such as copper cementation.
The Iridium-Ruthenium loaded organic amine phase is
treated with at least the stoichiometric quantity of an
aqueous solution of an alkaline reagent required to
breakup the amine complex formed between Iridium
and Ruthenium and produce a precipitate which is the
alkaline salt form of the extracted metal values. The
resulting alkaline/solvent mixture is then contacted
with an acidified reducing agent to solubilize the Iridium
and Ruthenium precipitates into an aqueous acidic
solution from which they may readily be isolated by
known methods.
The aqueous phase from which Iridium and Ruthenium
are extracted in the present invention is ordinarily
a mineral acid leach solution of the type normally resulting
from the fusion and leaching of Platinum metal
ore concentrates. The invention will be further described
by reference to separation and recovery of Rhodium,
Iridium and Ruthenium from hydrochloric acid
solutions such as generally occur in Platinum group
metal recovery. However, the invention is not limited
as such and may be operated to separate metals from
solutions of other mineral acids which are used in the
recovery or assay of Platinum group metal values, provided
the acid does not attack or degrade the organic
extractant and will afford the formation of organic soluble
complexes of the desired metals with the quaternary
amine extractant. In aqueous chloride solutions, the
4,107,261
1
PROCESS FOR THE SEPARATION OF PLATINUM
GROUP METALS
This is a continuation of application Ser. No. 629,879,
filed Nov. 7, 1975, now U.S. Pat. No. 4,012,481.
This invention relates to a method for separating
dissolved metal salts from aqueous mineral acid solutions
and more specifically to a scheme for separating
Rhodium from Iridium and/or Ruthenium by solvent
extraction with an organically substituted quaternary 10
ammonium salt and recovering the Iridium and Ruthenium
values from the loaded organic. Still more specifically,
the invention relates to a method for the organic
solvent extraction of Iridium and/or Ruthenium from
aqueous chloride solutions containing Rhodium, Irid- 15
ium and Ruthenium and recovery of the isolated Iridium
and Ruthenium values from the loaded organic
phase.
The separation of Rhodium from Iridium has long
been considered a difficult aspect of Platinum group 20
metal separation. The traditional methods for separating
Rhodium-Iridium-Ruthenium from one another are
well known in the art, but involve long and tedious
processing operations.
More recently, somewhat faster methods have been 25
evolved for separating Iridium-Rhodium-Ruthenium
from aqueous solution by ion exchange. There are,
however, several drawbacks and disadvantages involved
in such processes. Ruthenium may be reduced
on ion exchange resins and the IrC16-2 ion is difficult 30
to elute. Also, the nature of the Rhodium-containing
species is very sensitive to solution conditions on the
resin column and may change when the metal bearing
solution is on the column to prevent the separation.
Tertipis et al describe the solvent extraction of Irid- 35
ium from hydrochloric acid solutions containing Rhodium
through the use of tributyl phosphate in Analytical
Chemistry 33 (1961), No. 12, pages 1650 through
1652. However, this technique is undesirable since it
involves reaction conditions which significantly restrict 40
its general usefulness.
The problem of successfully separating Rhodium
from Iridium by solvent extraction with tributyl phosphate
is further complicated when the pregnant aqueous
solution in which the metals are dissolved also contains 45
Ruthenium. In such instances substantial difficulty is
encountered in obtaining a pure Rhodium product as
the Ruthenium contaminates both the Iridium and Rhodium
thereby frustrating the isolation of a pure form of
either metal. 50
It has now been unexpectedly discovered that Rhodium
values can be quickly and easily separated from
aqueous mineral acid solutions containing Rhodium,
Iridium and Ruthenium by solvent extraction with an
organic solvent containing an organically substituted 55
quatern~ry ammonium compound. It has also been
found that the Iridium-Ruthenium values extracted into
the amine solvent can be stripped and recovered as a
mixture of Iridium and Ruthenium salts by sequentially
contacting the loaded organic with an aqueous alkaline 60
solution and an acidified reducing agent. In operation, a
water immiscible organic solvent containing an organically
substituted quaternary ammonium salt is brought
into contact with the aqueous mineral acid solution and
forms a complex with Iridium and Ruthenium which 65
are present in the solution in their anionic states. The
complex is extracted into the solvent phase leaving
Rhodium (present in the acid solution as a cation) in the
3
4,107,261
4
[><J
wherein RI> R2, and R3 are hydrocarbon chains having
eight to ten carbon atoms, with eight carbon atoms
prevailing. Also useful as the amine solvent extractant
are Adogen 468 methyltri-n-alkylammonium chloride
(average CIO), and Adogen 464 methyltri-n-alkylammonium
chloride (Cs - CIO) (both made by Ashland
Chemical Co.). The organically substituted quaternary
amines which may be used in the present invention must
be sufficiently soluble in at least one of the solvents
referred to below, or mixtures of them to make at least
a 1% solution. Finally, the ammonium compound
should provide for ready phase disengagement following
extraction. The preferred organic extractant in the
present invention is Aliquat-336. Prior to use in the
extraction the amine extractant is usually conditioned to
the form of the acid solution to be contacted. Thus in
the preferred embodiment in which Iridium and Ruthenium
are extracted from hydrochloric acid solution, the
extractant is conditioned to chloride form by treatment
with NaCI in IN HCl.
The major constituent of the extraction liquid is a
water immiscible carrier solvent in which the organic
amine extractant is dissolved to form the organic phase.
Conventional organic solvents including, for example,
aliphatic hydrocarbons such as petroleum derived
liquid hydrocarbons, either straight chain or branched,
kerosene, fuel oil, etc., are useful in the invention. Various
aromatic solvents or chlorinated aliphatic solvents
may also be employed such as benzene, toluene, xylene,
carbon tetrachloride and perchloroethylene. The organic
solvents must be substantially water immiscible
and capable of dissolving the organically substituted
amine extractant. In addition, the solvent should be
inert and not interfere with the extraction of Iridium
and Ruthenium metal values from acid solution by the
organically substituted amine. Kerosene available as
AMSCO 175 is preferably employed because of its
ready availability and as a matter of economy.
The organically substituted quaternary amine component
of the organic extractant mixture must have a solubility
of at least about 1% by weight in the hydrocarbon
solvent of the organic phase which must be insoluble in
water.
A phase modifier is also admixed with the carrier
solvent and extractant to prevent the formation of a
55 third phase in stripping the pregnant organic. Water
insoluble straight or branched chain aliphatic alcohols
containing at least 6 carbon atoms are generally used as
phase modifiers. Examples of suitable phase modifiers
include isodecanol, 2-ethyl hexanol and tridecanol. Iso-
60 decanol is preferred for use in the present invention.
The organic mixtures of the present invention will
usually contain from about 5 to 15 volume percent of
the organic amine extractant, between about 85 and 95
volume percent of the carrier solvent, and from about 1
65 to about 5 volume percent of the phase modifier. Although
the preceding criteria are generally applicable,
the invention is not limited to operation within these
boundaries. Since only a limited amount of the active
[>(]
soluble Rhodium-Iridium-Ruthenium compounds are
generally present as complex chloro salts or in a form of
their corresponding hydrochloric acid complexes. Typically,
such leach solutions result from crude ore pro- 5
cessing operations and range between 0.1 to about 5
normal HCI and up to about 250 grams per liter
CL-and in some instances higher. In addition to the
Platinum group metals, the solutions may contain other
base metal impurities such as lead, copper, bismuth, 10
nickel, aluminum, silica, silver, and barium.
It has been discovered that in order to achieve an
effective separation of Iridium and Ruthenium from
Rhodium in the preferred hydrochloric acid solutions, 15
it is necessary to have Rhodium present in the form of
a cationic chloro complex of Rhodium and for the Iridium
and Ruthenium to exist as oxidized Iridium and
Ruthenium chloro complexes respectively. This is im- 20
portant as the oxidized Iridium and Ruthenium chloro
complexes behave as an anion toward the organic extraction
mixture and are extracted, whereas the Rhodium
chloro complex behaves as a cation and is not
extractable with the organically substituted quaternary 25
amine extraction agent. The foregoing differences in
ionic condition are maintained throughout the extraction
so that the organic phase containing the amine
complexing agent does not become fouled with Rho- 30
dium chloro complexes which would behave as anionic
species and be extracted. The aqueous acid solutions
from which the aforementioned metals are extracted are
preferably substantially free of gold, iron, Platinum, and
Palladium which are removed beforehand by conven- 35
tional techniques well known in the art.
The extraction liquid used to separate Iridium and/or
Ruthenium from Rhodium consists of three constituents:
an organic extractant, a water immiscible carrier 40
solvent and a phase modifier.
In the present invention an aqueous mineral acid
solution containing, for example, Iridium, Rhodium and
Ruthenium dissolved in a hydrochloric acid solution is 45
contacted with a water immiscible organic solvent containing
a quaternary ammonium compound capable of
forming complexes with Iridium and Ruthenium that
are preferentially soluble in the resultant organic phase.
The quaternary ammonium compounds capable of per- 50
forming these functions have the following basic structure:
wherein RI, R2, R3 and R4 are straight or branched
aliphatic alkyl or aromatic hydrocarbon groups. Generally
at least one of R1, R2, R3 and R4 are fatty alkyl
groups. Aliquat 336, methyl tricaprylyl ammonium
chloride, manufactured by General Mills, is an effective
extractant and has the following cation:
4,107,261
5
extracting ingredient is present in the solvent phase, it
can only hold a limited amount of any given metallic
element at saturation. Once the concentration of metal
in the solvent has reached the saturation level, no additional
metal will go into the solvent regardless of its 5
concentration in the aqueous phase. The quantity of
metal which a given solvent extractant will hold is
termed "the maximum loading" and governs the total
quantity of solvent required to do a given amount of
extraction. Based upon the maximum loading character- 10
istics of the particular extractant, the metal-bearing
characteristics of the leach liquor that is to be extracted
and the number of extraction stages to be employed, the
concentration of extractant and phase modifier in the
solvent may be adjusted, or the Organic/Aqueous 15
(0/A) ratio for any particular extractant concentration
may be varied to achieve a desired loading. In one effective
version of the extraction process the organic liquid
mixture used to extract Iridium and Ruthenium from an
aqueous hydrochloric acid solution comprises 10 vol- 20
ume percent Aliquat-336, 87 volume percent kerosene
and 3 volume percent isodecanol. As a measure of economy,
it is preferred to employ the lowest organic/aqueous
ratio that will provide efficient separation of the
desired metal values from a given aqueous mineral acid 25
solution.
The liquid-liquid extraction may be carried out by
continuous countercurrent or batch processing procedures.
Typical apparatus for use in the present invention 30
could include (without limitation thereto) a multiple
stage countercurrent mixer-settler system in which the
barren organic solvent and a pregnant aqueous stream
are mixed together for a predetermined time period
following which they are permitted to separate in a 35
settling reservoir. The solvent and aqueous then flow in
opposite directions to the next stage of contact.
Briefly summarizing the separation and recovery
process operation, fresh metal bearing aqueous mineral
acid solution is contacted and admixed with the organi- 40
cally substituted quaternary amine solvent for a predetermined
time period under oxidizing conditions. The
iridium and ruthenium anions in the aqueous solution
form a complex with the amine and are extracted into
the solvent phase. The admixture is permitted to settle 45
into distinct organic and aqueous phases which are
isolated from one another. Iridium and ruthenium are
simultaneously stripped from the metal loaded organic
phase by sequential treatment with at least the stoichiometric
quantity of alkaline solution which will neutral- 50
ize the acid salt ofthe amine followed by treatment with
an acidic reducing solution. Rhodium is won from the
aqueous raffinate by known methods (e.g., cementation
with copper powder). Iridium and ruthenium may also
be isolated from the stripping solution using conven- 55
tional techniques known to the art.
An important aspect ofthe present invention involves
conditioning (oxidizing) the metal bearing acid solution
to an emf or redox potential as measured by means of a
platinum-calomel electrode ofbetween about - 500 and 60
-1000 millivolts (otimally about -900 mv) prior to the
organic extracting operation in order to maintain high
extraction efficiencies and promote the production of
rhodium solutions essentially barren of iridium and
ruthenium. It should be noted that while the extraction 65
process will operate at emf values less than -500 mv,
extraction efficiencies become correspondingly lower.
The conditioning treatment is continued through the
6
extraction to insure that the aqueous phase is maintained
in the oxidized state. The conditioning operation can be
accomplished by the addition of sodium hypochlorite
(NaOCI) solution at a controlled rate to the aqueous
acid solution to be extracted to maintain the solution in
an oxidized condition (indicated by obtaining an emf
reading between - 500 and - 1000 millivolts, and preferably
about -900 mv). Alternatively, chlorine gas
(CI2) or other oxidants (e.g., peroxide) can be employed
to accomplish the same results as sodium hypochlorite.
The iridium-ruthenium extraction and stripping operations
are preferably carried out at about 25° C although
satisfactory performance has been achieved at
temperatures in the range 20° C - 40° C and up to 50° C
and higher. At temperatures below about 20° C the
phase disengagement is slow, while operation above 40°
C is hazardous due to the danger of fire.
Alkaline stripping reagents for use in the present
invention must be water soluble compounds which will
convert the extracted metal values contained in the
organic solvent into reaction products that are readily
soluble when contacted with the acidic reduction solution.
Stripping efficiency (Le., the ability to remove a
large quantity of metal salt per unit volume of strippant)
is also an important criteria for selection of an alkaline
stripping agent. Suitable alkaline agents include water
soluble alkali and alkaline earth carbonates, bicarbonates
and hydroxides, e.g., sodium and potassium hydroxide,
carbonate or bicarbonate, although sodium
hydroxide is preferably employed. The amount of alkaline
strippant required is at least the quantity which will
neutralize the acid salt (usually the chloride) form of the
quaternary amine organic and desirably includes in
excess of the stoichiometric amount (preferably about
50-100%) of the alkaline agent to insure efficient stripping
within the shortest possible contact times. By contacting
the loaded organic solvent with the alkaline
stripping solution, the organic soluble Iridium and Ruthenium
organic amine complexes are converted to
metal salts and chloride form of the amine.
Although metallic values can be recovered from the
loaded organic using only the acidified reducing strip
solution and without a prior contact with an alkaline
reagent, it has been unexpectedly discovered that a
consistently higher percentage of the Iridium and Ruthenium
metals present in the organic solvent were
stripped using sequential treatment with alkaline solution
and an acidic reducing agent.
The acidified reductant stripping agents are selected
based upon their capacity to contribute additional stripping
action to the alkaline treated loaded amine organic
as well as for their ability to maintain a reducing environment
in the strip solution. The latter criteria is most
important to prevent inadvertent reextraction of the
Platinum group metal values from the strip solution.
Also, the strippant should not contribute any foreign
metals to the organic which might cause eventual fouling
or a reduction in loading capacity. Satisfactory
reductant stripping agents include acidic solutions of
hydrazine salts, hydroxylamine salts, S02' and conventional
organic reducing agents (Le., organic acids such
as oxalic). The reductant stripping solutions are acidified
to between about 0.5-2.5 N (preferably 2.0 N) to
solubilize the Iridium and Ruthenium alkaline salts. One
suitable reducing solution is hydrazine dihydrochloride
(N2H4.2HCI) acidified to 2.0 N HCl.
The quantity of acidified reducing agent utilized is at
least the stoichiometric amount based upon the alkaline
4,107,261
7
strippant previously added, and desirably includes in
excess of the stoichiometric amount (preferably about
100-150% to insure complete dissolution of the precipitated
Iridium and Ruthenium values in the aqueous
phase. Additionally, some further stripping action is
realized during the contact period with the acidified
reducing strip solution. Although suggested concentrations
of strippant solutions have been described herein,
those skilled in the art will recognize that these may be
8
tion and then extracted 4 times in succession with fresh
solvent in a like manner described above. The extraction
organic in both of the above examples contained 10
volume % Aliquat-336, 3 volume % isodecanol, and 87
5 volume % kerosene (AMSCO 175) and was conditioned
to the chloride form of the organic by contacting
with a solution of 100 gil NaCI in I normal HCI followed
by washing using a solution 20 gil NaCI adjusted
to pH 1.5 with HCl.
Table I
Rh-Ir-Ru Extraction by Aliquat-336 at Various Solution EMF's
-Assay g/ITest
Contact Aqueous Feed Aqueous Raffinate Loaded Organic % Extracted
No. No. EMF, mv Rh Ir Ru Rh Ir Ru Rh Ir Ru Rh Ir Ru
-520 4.6 1.25 4.5
I 4.3 0.43 1.8 0.06 0.30 1.4
2 4.1 0.34 1.3 0.08 0.05 0.23
3 3.9 0.31 1.1 0.09 0.03 0.09
4 3.7 0.27 0.8 0.09 0.03 0.08 20 78 82
2 -900 4.6 1.25 4.5
I 4.4 0.02 0.7 0.04 0.54 2.0
2 4.1 0.03 0.1 0.07 0.02 0.27
3 3.9 0.03 0.02 0.08 0.01 0.04
4 3.8 0.03 0.008 0.06 <0.01 0.009 17 97 99
varied depending upon the organic volumes to be
treated, stripping efficiency of a particular strippant, to 25
adjust the quantity and concentration of strip to yield
strip solutions containing significant quantities of dissolved
Iridium and Ruthenium values and to avoid
dilution and handling of weak andlor large volumes of
solution. 30
The time required for stripping contact will vary
from one loaded organic to another depending upon the
particular solvent system, the quantity of Iridium and
Ruthenium sought to be stripped and the temperature at
which the stripping operation is conducted. In most 35
instances strip contact times of between 1 and 10 minutes
can be utilized to provide satisfactory results.
The invention is further illustrated by the following
examples.
The examples present in Table 1 were performed to 40
illustrate the method of effecting a more complete separation
of Rhodium from Iridium and Ruthenium by
maintaining a high oxidation state of the aqueous feed
liquor. It should be noted, however, that the present
invention is not limited to operation strictly according 45
to the instant example.
In Test No. 1 a predetermined amount of IridiumRhodium-
Ruthenium aqueous acid solution analyzing
4.6 gil Rhodium, 1.25 gil Iridium and 4.5 gil Ruthenium,
265 gil Cl-at 1 normal HCI and having a mea- 50
sured emf of - 520 millivolts was contacted 4 times in
succession with fresh organic extractant at an organic to
aqueous ratio of 2 to 1. Each contact was for a period of
2 minutes. Following each contact the phases were
separated and the amount of Iridium and Ruthenium
It will be seen from the above results that maintenance
of a high oxidation state during extraction results
in a more complete separation of Iridium-Ruthenium
from Rhodium and produces a lower lridium/Ruthenium
raffinate for recovery of Rhodium by cementation.
The examples presented in Table 2 were performed
to show the increase in stripping efficiency when using
the combination alkaline plus acidified reducing solution
strip treatment. For both examples in Table 2 a
10% by volume Aliquat-336 solution in kerosene containing
3% by volume isodecanol was loaded with Iridium
and Ruthenium by contacting with an acidic
Rhodium-Iridium-Ruthenium chloride solution oxidized
to emf -900 mv by addition of 50 gil NaOCI
solution. A 100 ml portion of the loaded organic was
agitated for 10 minutes with 50 gil NzH4.2HCI in 2 N
HCI at an organic to aqueous ratio of 2 to 1 at room
temperature. The percentage of Iridium and Ruthenium
stripped was determined by analysis of the separated
phases. A second 100 ml portion of the same loaded
solvent was agitated with 8 ml of 200 gil NaOH (2X
stoichiometric based on the normality of the prepared
amine organic) for 5 minutes at room temperature. Following
the caustic reaction period, 42 ml of 50 gil
NzH4.2HCI in 2 N HCI was added (2.1 X stoichiometric
based on the amount of caustic solution added) and the
mixture stirred for an additional 10 minutes at room
temperature. The final stripped volumes so obtained
had an organic to aqueous ratio of 2/1. As in the first
test, the percentage of Iridium and Ruthenium stripped
was determined by analysis of the separated phases.
Table 2
% of Iridium-Ruthenium Stripped
Organic Assay gil Assay gil
Loaded Stripped Strip Solution % Stripped
Rh Ir Ru Rh Ir Ru Rh Ir Ru Rh Ir Ru
0.030 0.32 0.59 0.020 0.18 0.49 0.020 0.28 0.21 33 44 17
0.030 0.32 0.59 0.008 0.04 0.08 0.044 0.56 0.97 73 88 86
Test
No. Strippant
N2l!{. mCI
in 2N HCl
2 NaOH plus
N2l!{. mCI
in 2N HCl
extracted determined by analysis. In Test No. 2 the
identical Rhodium-Iridium-Ruthenium solution was
adjusted to emf - 900 millivolts by gaseous Clz oxida-
It can be seen from the above table that the alkaline
plus acidified reductant strip system significantly in4,107,261
wherein Rl> R2, R3 and R4 are hydrocarbon groups,
said compound being sufficiently soluble in said
solvent to make a 1% solution and capable of forming
complexes with Iridium and Ruthenium that
are preferentially soluble in said solvent and
whereby said contacting results in the formation of
an organic extract phase and an aqueous raffinate
phase,
separating said extract phase from said aqueous raffinate
phase,
contacting said organic extract phase with a sufficient
quantity of an aqueous alkaline stripping agent to
neutralize the organic extract phase, said contact
resulting in the formation of an aqueous phase
loaded with said Iridium and Ruthenium and a
stripped organic phase, and thereafter
contacting said stripped organic phase and said
loaded aqueous phase with a solution consisting of
an acidified reducing agent which is at least the
stoichiometric equivalent of said alkaline agent,
and maintaining said Rhodium in the form of a
cationic complex and said Iridium and Ruthenium
in their anionic states during said extraction procedure.
3. The process of claim 2 wherein said alkaline stripping
agent is a water-soluble member selected from the
group consisting of the carbonates, bicarbonates and
hydroxides of alkali and alkaline earth metals.
4. The process of claim 2 wherein said reducing agent
is selected from the group consisting of acidified solutions
of hydrazine salts, hydroxyl amine salts, reduced
metallic salts, S02, and organic dicarboxylic acids.
5. The process of claim 2 wherein at least one of R1,
R2, R3 and R4 is a fatty alkyl group.
6. The process of claim 5 which comprises conducting
said contacting operation at a temperature between
about 20° C and 40° C.
* * * * *
10
maintaining said Rhodium in the form of a cationic
complex and maintaining said Iridium in an anionic
state throughout said extraction procedure.
2. A process for the separation and selective recovery
5 of Rhodium, Ruthenium and Iridium values from an
aqueous acidic medium which comprises contacting the
medium with an organic extraction reagent comprising
a water immiscible solvent having dissolved therein an
organically substituted quaternary ammonium compound
having the structure
30
wherein R!, R2, R3and R4 are hydrocarbon groups for
a predetermined time period to form an organic 35
extract phase and an aqueous raffinate phase,
said quaternary ammonium compound being sufficiently
soluble in said solvent to make a I% solution,
separating said extract phase from said aqueous 40
phase,
contacting said separated extract phase with at
least the stoichiometric amount of aqueous sodium
hydroxide solution required to neutralize
the chloride form of said amine and form a me- 45
tallic hydroxide precipitate, contacting said alkaline
treated solvent with at least a stoichiometric
amount based on the stoichiometric value of said
alkaline solution of an acidified aqueous reducing
agent, said contact resulting in the formation 50
of a loaded aqueous phase and a stripped organic
phase,
separating said loaded aqueous phase and said
stripped organic phase, and recovering Iridium 55
from said loaded aqueous phase,
9
creases the percentage recovery of Iridium and Ruthenium
from the loaded solvent. The beneficial result
obtained from the two-step stripping system is the production
of good barren organic for recycle back to the
extraction stages of the Rhodium separation circuit.
From the foregoing it will be seen that the present
invention combines a rapid technique for separation of
Iridium and/or Ruthenium from Rhodium with an efficient
extraction and stripping system. The separation
and recovery procedure are quite specific and will func- 10
tion in solutions containing widely varying quantities of
the respective metals. The economy and speed of operation
of the present process make it ideal for incorporation
as part of a continuous processing system for sepa- 15
ration of Rhodium essentially free of Iridium and/or
Ruthenium from aqueous acid solutions of such metals.
What is claimed is:
1. A continuous process for the separation and recovery
of Rhodium and Iridium dissolved in aqueous chlo- 20
ride solutions which comprises:
contacting said aqueous chloride solution with an
organic solvent containing an organically substituted
quaternary ammonium halide having the
following structure: 25
60
65