United States Patent [19]
Baltz et at
[11]
[45]
4,041,126
Aug. 9, 1977
[54] SEPARATION AND SELECfIVE RECOVERY
OF PLATINUM AND PALLADIUM BY
SOLVENT EXTRACTION
[75] Inventors: John Baltz, Lakewood; Enzo
Coltrinari, Arvada, both of Colo.
[73] Assignee: PGP Industries, Inc., Santa Fe
Springs, Calif.
OTHER PUBLICATIONS
Borbat et aI., "Chemical Absts.," vol. 65, 1966, No.
11423(c).
Dalgikh et aI., "Chemical Absts.," vol. 65, 1966, No.
11423(e).
Neikova et aI., "Chemical Absts.," vol. 80, 1974, No.
11087e.
Shulman et aI., "Cheniical Absts.," vol. 77, 1972, No.
80034s.
[21] Appl. No.: 642,146 Primary Examiner-Herbert T. Carter
Attorney, Agent, or Firm-Darby & Darby
[22] Filed: Dec. 18, 1975
[57] ABSTRACf
[56] References Cited
U.S. PATENT DOCUMENTS
FOREIGN PATENT DOCUMENTS
1,057,078 5/1959 Germany 423/22
142,768 1111961 U.S.S.R 423/22
[51] Int. CJ.2 C01G 55/00
[52] U.S. CI. 423/22; 75/101 BE;
423/658.5; 423/DIG. 14
[58] Field of Search 423/22, 658.5, 659 C;
75/101 BE
3,437,431
3,558,288
3,666,446
3,812,232
3,960,549
3,979,207
3,985,552
4/1969
111971
5/1972
5/1974
6/1976
9/1976
10/1976
Platz et al. 423/22
Burrows 75/101 BE
Cook et al. 75/101 BE
Bauer et al. 423/22
MacGregor 75/101 BE
MacGregor 423/22
Edwards 75/101 BE
A process for the separation and selective recovery of
platinum and palladium values from an acidic aqueous
medium which comprises contacting the medium with a
mixed organic extraction reagent comprising a water
immiscible organic solvent having dissolved therein an
organically substituted secondary amine compound
capable of forming complexes of platinum and palladium
that are preferentially soluble in the organic solvent
and whereby the contacting results in creation of
an organic extract phase and an aqueous raffinate phase.
After phase separation, palladium is selectively recovered
by contacting the organic phase with an aqueous
solution of an acidified reducing agent. Platinum is
separately recovered by contacting the organic phase
with an aqueous alkaline solution. The process may be
employed as a method for concentrating solutions of
platinum or palladium.
14 Claims, No Drawings
1
4,041,126
2
wherein R1and R2 are hydrocarbons and R( is a straight
or branched fatty alkyl group (Cg through C30); and R2
10 is alkyl, aryl or fatty alkyl (Cg through C30), and R1plus
R2 contain between 18 and 35 carbon atoms. The term
aliphatic includes branched chain radicals and alkyl or
aryl substituted radicals. The term aryl includes alkyl
substituted aryl radicius. The organically substituted
ammonium compounds useful as extractants in the present
invention form complexes with each of the desired
metals (i.e., platinum and palladium) which complexes
are soluble in at least one of the organic solvents set
forth below, permit ready disengagement of the raffinate
and extract phases after the extraction, and have a
solubility of at least I% by weight in the hydrocarbon
solvent of the organic phase. Additionally, the substituted
ammonium wmpound must be insoluble in water.
Amberlite LA-I, N-dodecenyltrialkylmethylamine
(made by Rohm & Haas Co.) is an effective extractant
preferred for use in the invention. Other secondary
amines which are suitable for use as extractants in the
present invention include di(2-propyl-4-methylpentyl)amine,
di-N-decylamine, dilauryl amine, bis(l-isobutyl-
3,5-di-methylhexyl)-amine, N-benzyl heptadecylamine,
N-benzyl-I-(3-ethylpentyl)-4-ethyloctylamine, Nlauryltrialkylmethylamine,
di-tridecylamine ("tridecyl"
equals mixture of 13 carbon alkyls from tetrapropylene),
N-benzyl-(l-N-nonyl-N-decyl) amine, N-benzyl(
l-N-undecyllauryl) amine, di(l-N-heptyl-N-octyl)
amine, N-(nonyl-N~decyl) lauryl amine, N-(l-Nundecyllauryllauryl
amine, and di(I-N-nonyl-N-decyl)
amine.
The major constituent of the extraction organic phase
is a water immiscible carrier solvent in which the organically
substituted secondary 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
chain, kerosene, and fuel oil are useful as the carrier
solvent in the present invention. A wide variety of aromatic
solvents and chlorinated aliphatic solvents may
also be employed including, for example, benzene, toluene,
xylene, carbon tetrachloride, perchloroethylene.
The organic carrier solvent must be substantially water
immiscible and capable of dissolving the organically
substituted secondary amine extractant. Moreover, the
solvent should not interfere with the extraction of the
desired platinum and/or palladium metal values from
acid solution by the organically substituted amine. The
secondary amine constituent of the organic extractant
mixture must have a solubility of at least about 1% by
weight in the hydrocarbon solvent ofthe organic phase.
Kerosene, available as AMSCO 175 from the Amt!ri~an
Mineral Spirits Co., is the preferred solvent.
A phase modifier is usually admixed with the carrier
solvent and the extractant to increase the solubility of
platinum and palladium and help prevent the formation
of a third phase during extraction and when platinum
and palladium are stripped from the metal laden organic
extract phase. Water insoluble straight or branched
chain aliphatic alcohols containing at least 6 carbon
SEPARATION AND SELECfIVE RECOVERY OF
PLATINUM AND PALLADIUM BY SOLVENT
EXTRACfION
This invention pertains to a process for the separation 5
and selective recovery of platinum and palladium frQm
aqueous acidic solutions. More specifically, the invention
pertains to the separation and selective recovery of
platinum and palladium from aqueous hydrochloric
acid solutions.
The conventional procedures for separation of platinum
and palladium values from aqueous leach liquors
resulting from ore concentration are tedious and require
expensive apparatus. Since these techniques often call
for the stepwise treatment of each batch of pregnant 15
liquor in sequence, they are generally unsuitable for
operation on a continuous flow basis. A further drawback
of the aforementioned procedures is that they
frequently require lengthy treatment periods to separate
and recover platinum and palladium values from the 20
acidic solutions in which they are dissolved along with
other platinum group metals such as rhodium, iridium
and ruthenium. This tends to increase the already high
cost of these metals.
While the use of tertiary and quaternary amine ex- 25
tractants to win platinum and palladium values from
solution is discussed in S. African Pat. No. 72/0308, a
fairly lengthy and complex technique is required to strip
the extracted metal values.
It is accordingly an object of the present invention to 30
provide a process for the selective recovery of platinum
and palladium from an aqueous acidic medium by
means of a simple liquid-liquid extraction process.
A further object of the present invention is a process
for the separation of platinum and palladium from an 35
aqueous hydrochloric acid solution by coextracting the
metals into a mixed organic phase containing an organically
substituted secondary amine compound and selectively
recovering platinum and palladium from the organic
phase. 40
Another object of the present invention is provision
of a process for increasing the concentration of platinum
or palladium in aqueous solutions.
Further objects and advantages of the present invention
will be understood with reference to the following 45
description of the process.
According to the present invention, platinum and
palladium are selectively recovered from an aqueous
acidic medium in which they are dissolved by contacting
the aqueous medium with a mixed organic extrac- 50
tion reagent. The mixed organic reagent comprises a
water immiscible organic solvent in which is dissolved
an organically substituted secondary amine compound
having a solubility of at least 1% by weight in the organic
solvent and capable of forming a complex with 55
platinum and palladium that is preferentially soluble in
the organic solvent. The contacting step results in the
formation of an aqueous raffinate phase and an organic
extract phase containing the complexed metals. Following
phase disengagement the aqueous and organic 60
phases are segregated or separated from one another.
Palladium is recovered by contacting the organic phase
with an aqueous solution containing an acidified reducing
agent. Platinum recovery is effected by contacting
the organic phase with an aqueous alkaline solution. 65
The secondary amine compounds capable of functioning
as the extractant in the present invention have
the general formula:
4,041,126
4
extraction stages to be employed, either the concentration
of extractant and phase modifier in the solvent may
be adjusted or the organic/aqueous (0/A) ratio for any
particular extraction concentr~tion may be varied to
achieve a desired level of metal loading. In one effective
version ofthe platinum/palladium extraction process of
the instant invention, the organic phase used to extract
platinum and palladium from the preferred pH I aqueous
hydrochloric acid solution comprises 10 volume
percent (%) Amberlite LA-I, 3 volume percent (%)
isodecanol and 87 volume percent (%) kerosene. As a
measure of economy, it is normally preferred to employ
the lowest organic/aqueous ratio that will provide efficient
separation for platinum and palladium values from
an aqueous chloride solution. However, the most efficient
organic to aqueous ratio for the extraction of platinum
and palladium can be arrived at in accordance with
procedures well known in the art.
The liquid-liquid extraction may be carried out by
continuous counter-current, or batch processing procedures.
As is well known in the liquid-liquid extraction
art, greater separation may be achieved with multi-stage
extraction processes. Typical apparatus' for use in a
multi-stage embodiment of the present invention could
include, without necessarily being limited thereto, a
multiple stage counter-current 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 settling reservoir. The solvent and aqueous
phase then flow in opposite directions to the next stage
of contact.
Following extraction and separation of the organic
extract phase and the aqueous raffinate, platinum and
palladium may be selectively stripped by sequentially
contacting the organic extract phase with an aqueous
solution of an alkaline reagent (to strip platinum) and an
aqueous acidified reducing reagent (to strip palladium).
The preceding values need not be stripped from the
loaded organic phase in any particular sequence, except
in those instances described below where a chelating
agent is used in conjunction with the alkaline stripping
solution, in which case palladium is desirably stripped
first.
The alkaline stripping reagent used in the present
invention must be a water soluble compound which will
convert the extracted values in the organic solvent into
reaction products which are readily soluble in aqueous
solution. Stripping efficiency (i.e., the ability to remove
a large quantity of metal salts per unit volume of strippant)
is an important criteria for selection of an alkaline
stripping agent. Suitable alkaline stripping reagents
include water soluble alkali and alkaline earth metal
carbonates, bicarbonates and hydroxides, e.g., sodium
and potassium hydroxide, carbonate or picarbonate,
although sodium bicarbonate (NaHC03) is preferably
employed as the alkaline stripping reagent in most instances.
The quantity of alkaline strippant required is at
least the amount which will neutralize the acid salt
(usually the chloride) form of the secondary amine
organic and desirably includes in excess of the stoichiometric
amount (preferably about 50%) of the alkaline
reagent in order to assure efficient stripping within the
shortest possible contact times. The aqueous alkaline
stripping solutions used in the invention are fairly
strong and usually contain between about 5 and 100
grams per liter (g/l) of the alkaline stripping reagent
3
atoms in the hydrocarbon chain may generally be used
as phase modifiers. Examples of suitable phase modifiers
include isodecanol which is preferred, 2-ethyl hexanol
and tridecanol.
The aqueous phase from which platinum and palla- 5
dium are extracted in the instant invention is ordinarily
an aqueous mineral acid leach solution of the type normally
resulting from the fusion and leaching of platinum
metal ore concentrates. For purposes of illustration the
invention will be further described by reference to sepa- 10
ration and recovery of platinum and palladium from
aqueous hydrochloric acid solutions since these are
most commonly employed in the processing and recovery
of platinum group metals. In aqueous acid chloride
solutions, the soluble platinum and palladium com- 15
pounds are generally present as complex chloro salts.
Typically, such leach solutions range between about 0.1
to about 5 N HCl and up to about 250 grams per liter
Cl- and higher. In addition to the platinum group
metals (i.e., platinum, palladium, rhodium, ruthenium 20
and iridium), the solutions may contain other base metal
impurities such as lead, copper, bismuth, nickel, aluminum,
silver, silica and barium. The aqueous acid solutions
from which platinum and palladium are to be
extracted should preferably be substantially free of gold 25
and iron. Since these metals are frequently found in
association with platinum and palladium they may be
removed from solutions beforehand by conventional
techniques well known in the art. To promote optimum
separation of platinum and palladium during the extrac- 30
tion operation, the aqueous solution should preferably
contain less than about 0.5 grams per liter of gold or
iron.
It has been discovered that platinum and/or palladium
can be effectively extracted from the foregoing 35
aqueous hydrochloric acid solution in a conventional
liquid-liquid extraction process employing the secondary
amine organic extractant mixtures outlined above.
In order to prevent simultaneous extraction of rhodium
and iridium which are often present along with plati- 4{)
num and palladium, the aqueous leach liquors are reduced
to an emfofbetween about -425 mv.* and about
-650 mv., and preferably about -525 mv. prior to
contacting the extraction organic. This is usually accomplished
by the addition of a water soluble reducing 45
agent, as for example, hydroquinone. In addition to
preventing the extraction of rhodium and irridium,
maintenance of the aqueous chloride solution in the
reduced condition has been found to provide increased
loading of the organic phase with platinum and palla- 50
dium. In most instances the platinum and palladium
extraction is carried out under acid conditions in which
the pregnant leach solution is approximately pH I, although
the extraction will proceed satisfactorily with
solutions up to about 2 N HCl or higher. Under the 55
preceding conditions, platinum and palladium will ordinarily
exist as anions.
• all measurements made with standard platinum saturated-calomel
electrodes
Generally the organic extraction phase of the present
invention will contain from about I to about 25 volume 60
percent (%) of the secondary amine extractant, and
from about 0.05 to about 15 volume percent (%) of the
phase modifier diluted in carrier solvent. While the
preceding criteria are generally applicable, the invention
is not limited to operation within these boundaries. 65
Based upon the maximum metal loading characteristics
of a particular solvent, the metal bearing characteristics
of the leach liquor to be extracted and the number of
4,041,126
EXAMPLE I
This example illustrates that an organically substituted
secondary amine may be used to selectively extract
platinum and palladium from aqueous hydrochloric
acid solutions also containing iron, iridium, ruthenium
and rhodium.
An aqueous hydrochloric acid solution analyzing (in
grams per liter) (g/l) platinum 0.40, palladium 3.30,
iridium 1.10, rhodium 3.80, ruthenium 4.1 and iron 0.002
and having a measured emf of - 525 millivolts was
contacted and mixed with an extraction organic at an
organic to aqueous (0/A) ratio of 1.5 to 1 for two
minutes at 25° C to form an organic extract phase and an
aqueous raffinate phase. Following phase disengagement,
the aqueous and organic phases were separated
and analyzed. The extraction organic utilized in this
example contained 10 volume percent (%) AmberliteLA-
I, 3 volume percent (%) isodecanol and 87 volume
percent (%) kerosene (as AMSCO 175) and was conditioned
to the chloride form of the organic by two
contacts with a solution of 200 g/I NaCI in IN HCI at
an 0/A ratio of 2 to 1, followed by washing with a
solution of 20 grams per liter NaCI adjusted to pH 1.5
with HCI. The results of the extraction are summarized
in the following table.
TABLE I
6
organic volumes to be treated, metal stripping efficiency
of a particular strippant, to adjust the quantity
and concentration of strip to yield solutions containing
significant quantities of dissolved metal values and to
5 avoid the handling of weak and/or large volumes of
solution. The latter criteria is important because a significant
advantage of the instant process lies in its use as
a means of producing highly concentrated aqueous
solutions of either platinum or palladium from aqueous
leach liquors in which the metals are present at substantially
lower concentrations.
The stripping contact time required for a given strippant
solution will vary from one loaded organic to
another depending upon the particular solvent system,
the quantity of platinum or palladium sought to be
stripped from the organic extract phase and the temperature
at which the stripping operation is conducted. In
most instances stripping contact times of between 1 and
10 minutes will strip on the order of about 90% or more
of the respective metals from the loaded organic phase.
The invention is further illustrated in the following
examples:
5
and fall within the range of about 0.5 N to about 2.5 N.
By contacting the loaded organic solvent with the alkaline
stripping agent, the organic soluble, aqueous insoluble
platinum amine complexes are converted to aqueous
soluble/organic insoluble platinum salts.
A common problem encountered in stripping platinum
from loaded organic solvents containing platinum
group metals is the formation of an insoluble scum believed
to consist primarily of base metal impurities and
result in poor phase separation. To solubilize the emul- 10
sion-forming scum, an amino carboxylic acid chelating
agent (e.g., ethylenediaminetetraacetic acid (EDTA),
or diethylenetriaminepentaacetic acid) is added to the
strip solution, usually in the form of its sodium salt,
prior to contact with the metal laden organic extract 15
phase. The disodium salt of ethylenediaminetetaacetic
acid (i.e., NaEDTA) is the preferred chelating agent for
use in the instant process. The quantity of chelating
agent required to solubilize the scums will vary depending
upon the composition of a particular liquor, but will 20
generally be equal to at least about 10% by weight of
the alkaline reagent in the aqueous stripping solution.
While addition of the chelating agent reduces the scum
formation to trace levels and eliminates the physical
problem of phase separation, analysis of the aqueous 25
platinum strip solution revealed a corresponding increase
in the quantity of palladium stripped along with
platinum thereby reducing the platinum/palladium
ratio in the strip solution. As an example, a loaded organic
extract phase having a platinum/palladium ratio 30
of 0.3 and stripped with an aqueous NaHC03 solution
yielded an aqueous strip solution containing platinum
and palladium in the ratio of 450/1 platinum/palladium.
However, when the same solution ofNaHC03was used
as the strippant in conjunction with a solution of sodium 35
EDTA, the aqueous strip solution from the same loaded
organic phase had a platinum/palladium ratio of 11/1.
Hence, the use of a chelating agent (e.g., NaEDTA) in
the stripping solution was found to increase the amount
of palladium accompanying platinum into the aqueous 40
strip solution. Accordingly, palladium is preferably
stripped first from the loaded organic to a low level
with an acidified reductant solution followed by platinum
stripping using alkaline-NaEDTA solution.
Palladium is stripped from the loaded organic using a 45
water soluble reducing agent in an acidified aqueos
solution. An important criteria in selecting a suitable
reductant reagent is that is should not contribute any
Product
Aqueous feed
Raffinate
Loaded Organic
Amount Assay, gil Grams
inml. Pt Pd Ir Rh Ru Fe Pt Pd
1050 0.40 3.30 1.10 3.80 4.10 0.002 0.42 3.5
1050 0.04 1.00 1.10 3.78 4.05 0.002 0.04 1.1
1575 0.24 1.58 0.02 0.003 0.05 0.004 0.38 2.5
foreign metals to the organic which might eventually
cause fouling or a reduction in loading capacity. Satisfactory
reductant stripping agents for use in the present
invention include acidified solutions of hydrazine salts,
hydroxylamine salts, and conventional organic reduc- 60
ing agents, i.e., thiourea. The reductant stripping solutions
are acidified to between 0.1 to about 3 N HCI and
are preferably employed as 0.5 N solutions. The preferred
reducing solution is 50 g/l hydrazine dihydrochloride
(N2lL.2HCI) acidified to 0.5 N HCI. AI- 65
though suggested concentrations of strippant solutions
have been described herein, those skilled in the art will
appreciate that these may be varied depending upon the
It will be seen from the above Table that platinum and
palladium were selectively extracted from an aqueous
hydrochloric acid solution containing iridium, rhodium,
ruthenium and iron by an organically substituted secondary
amine. The minute quantities of iridium, rhodium,
ruthenium andiron which are extracted along with
platinum and palladium are relatively insignificant.
EXAMPLE II
The tests in this Example illustrate that a variety of
alkaline reagents at different concentrations may be
EXAMPLE III
8
Test No.5. In all instances it was possible to obtain strip
solutions in which platinum was at a relatively high
concentration with respect to palladium as compared to
the original aqueous solutions from which they were
separated. .
4,041,126
7
used to selectively strip platinum from an organic extraction
solvent loaded with platinum and palladium.
A ten percent (%) by volume Amberlite-LA-I solution
in kerosene (AMSCO 175) containing 3% by volume
isodecanol (and conditioned to chloride form as in 5
Example I) was loaded with platinum and palladium by
contacting with an aqueous hydrochloric acid solution
assaying (in gil) gold 0.007, platinum 2.86, palladium The extraction and selective stripping tests in Exam-
8.40, iridium 0.031, rhodium 0.038 and ruthenium 1.13. pIe III were performed to illustrate that the sequence of
The loaded organic assayed in (gil) platinum 1.12 and 10 stripping platinum and palladium from a loaded seconpalladium
3.55. Predetermined quantities of the loaded dary amine organic is not important and either metal
organic were treated with solutions of NaZC03, NaH- may be stripped first through the process of the present
C03 and NaOH in separatory funnels at room tempera- invention.
ture (plus or minus 25° C) at an 01A ratio of 2 to 1. The To carry out Example III a 10% by volume solution
contact times and alkaline concentration of the stripping 15 of Amberlite LA-I in 3 volume percent (%) isodecanol
solution were varied as noted in Table II. Following and 87 volume percent (%) kerosene (AMSCO 175)
each contact period, the phases were separated, filtered was loaded with platinum and palladium in a single
and assayed for platinum distribution. Results of the contact with a hydrochloric acid solution assaying (in
respective assays are indicated in Tables II and IIA gil) gold 0.004, platinum 2.90, palladium 8.20, iridium
below. 20 0.024, ruthenium 1.13 and rhodium 0.036. Prior to the
TABLE II
Loaded organic: 1.12 gil Pt + 3.55 gil Pd
Stripping: 0/A = 211
Contact Assays 1/ % UK"
(concen-
Test Strip Volumes Taken, ml Time Temp Strip Org.,gll Strip Soln, g/I Stripped tration) Ratio Pt/Pd
O/A
No. Solution Organic Aqueous min °C Pd Pd Pt Pd Pt Pd Pt Pd in Strip
I 50 gil Na2C03 30 IS 5 ±25 0.03 . 3.30 2.19 0.49 97 7< I 7 4.5/1
2 50 gil NaOH 30 IS 5 ±25 0.03 2.80 2.06 0.91 97 21< I 3 2/1
3 11 gil Naif03 30 IS IS ±25 1.17 3.45 0.007 0.002< 1< I> 100> 100
4 50 gil Na C03 30 IS IS ±25 0.18 3.52 1.80 0.004 84< 1< 1> 100 450/1
5 50 gil NaHC03 50 25 15 ±40 0.25 3.52 1.80 0.038 78 1< 1 93 47/1
6 50 gil NaHC03 + 30 15 15 ±25 0.20 3.45 1.91 0.17 82 3< 1 20 11/1
5 gil NaEDTA2/
7 75 gil NaHCO; + 50 25 IS ±25 0.21 3.40 1.87 0.18 81 4< 19 10/1
5 gil EDTA3
50 gil NaHC03 + 50 25 15 ±25 0.28 3.44 1.76 0.17 75 3< 20 10/1
5 gil EDTA
IIAll assays were on filtered products and do not include losses, if any, in scum products.
21NaEOTA = (Ethylenedinitrilo), tetra-acetic acid disodium salt.
'lEOTA = (Ethylenedinitrilo), tetra-acetic acid.
_=- TABLE IIA 40
Test
No.
extraction of emf of the aqueous solution was reduced
Physical Observations to _ 525 millivolts by the addition of hydroquinone.
Scum suspended thru aqueous. Poor phase The extraction organic was preconditioned to chloride
separation.
2 Scum suspended thru aqueous. Poor phase form by two contacts at an 01A ratio of 2 to 1 with 100
3 ~~:~al~~queous, poor phase separation. 45 grams per liter NaCI in IN HCI followed by washing
4 ( Scum suspended in aqueous, settles in with 20 grams per liter NaCI adjusted to pH 1.5 with
( aqueous, clear organic. Same problem, HCI. The extraction was carried out by allowing the
5 ( both tests.
6 Trace scum, no phase separation problem. aqueous solution to contact the organic for three min-
7 Clear organic + aqueous phases, no scums. utes at 24°C and at an 01A ratio of 2 to 1. Following
__8__C_l_e_ar_o_r_ga_n_ic_+_a...;q_ue_o_us_p_h_a_se_s,_n_o_s_cu_m_s_. 50 the contact period the phases were separated and the
loaded organic phase scrubbed by contacting with pH 1
HCL for three minutes at 24° C at an 01A ratio of 2 to
1. The phases were again separated and the scrubbed
platinum and palladium loaded organic was analyzed,
and assayed (in gil) platinum 1.06, palladium 3.52, iridium
0.002, ruthenium 0.002 and rhodium less than 0.001.
The loaded organic solution was then divided into three
approximately equal portions (labeled organic 1, 2 and
3) which were each contacted once with an aqueous
strip solution containing 50 gil NaHC03 for a period of
5 minutes at 25° C. After contacting the first loaded
organic portion, the phases were separated and sufficient
NaHC03 added to the aqueous phase to restore it
to 50 grams per liter NaHC03, and the restored solution
used to contact the second and third portions of loaded
organic in sequence. All contacts were carried out at an
01A ratio of 2 to 1 and the phases separated and analyzed
after each contact. The platinum pregnant aque-
The results of the tests illustrated in Table II indicate
that a variety of alkaline reagents can be used to selectively
strip platinum from an amine organic loaded with
platinum and palladium. The poor stripping action of 55
Test No.3 is attributable to use of a weak alkaline solution
(11 gil). The insoluble scums formed in Tests Nos.
1 through 5 resulted in poor phase separation. The
emulsion forming scum was solubilized by addition of a
chelating agent [NaEDTA (ethylene dinitrillo)tetraa- 60
cetic acid disodium salt] to the alkaline stripping solution
prior to contact with the loaded organic. As indicated
in the results of Tests Nos. 6 through 8, this entirely
eliminated the scum formation in most instances
or reduced it to trace levels and also alleviated the 65
physical problem of phase separation. A 50 gil solution
of NaHC03 provided optimum selective stripping of
platinum from palladium as illustrated in the results of
10
4,041,126
9
ous strip solution was then acidified to pH 1 with l2N TABLE IV-continued
HC!. Analyses of the scrubbed-loaded organic, each Amount Assay,gll
stripped organic portion and the acidified platinum .:.P.:'ro:::d~u::::ct~_...,---__...,---~m,;;-I O;-:/;;-A_-----;:;-:P:;rt~_,,-:Pdm_
pregnant strip solution were carried out and the results Ramnate 850 1.0 0.70 1.70
found to be as follows: 5 Loaded Organic 850 1.04 2.60
TABLE III
Amount Assay, gil Grams
Product ml O/A Au Pt Pd Ir Ru Rh Pt Pd
Scrubbed organic 1400 0.005 1.06 3.52 0.002 0.002 <0.001 1.48 4.9
Stripped organic I 440 2.0 0.05 3.52 0.02 1.5
Stripped organic 2 470 ! 0.06 3.52 0.03 1.6
Stripped organic 3 490 0.09 3.52 0.04 1.7
Pt pregnant strip 232 0.002 6.00 0.004< 0.001 0.001 <0.001 1.39< 0.001
(acidified) 1.48 4.8
Pt Pd
% stripped 94 0.03
Ratio Pt/Pd in pregnant strip = 1000/1
Amount Assay,gll Grams % Stripped
Product ml Pt Pd Pt Pd Pt Pd
Scrubbed
orlianic
stnpped 700 1.04 2.60 0.728 1.82
Combined
Pd/organic 700 1.00 0.56 0.700 0.39 <I 78
Pd pregnant
strip 200 0.10 6.90 0.020 1.38
0.720 1.77
The scrubbed loaded organic (assaying in gil) platinum
1.04 and palladium 2.60 was then subdivided into
two separate portions. The first portion was conJa~ted
with a 50 gil aqueous solution of N2lL.2 HCl.acldified
to 0.5N with HCL for 3 minutes at an 01A ratio of 2 to
1. Following phase separation the aqueous raffinate
phase was used to contact the second portion of scrubbed
organic (at an 01A ratio 1.5 to 1) for 3 minutes at
25°C. The palladium pregnant aqueous raffinate was
separated from the organic extract phase which was
then combined with the previously stripped first organic
portion. As in the initial ~est, th~ percentages and
amounts of platinum and palladIUm strIpped were determined
by analysis of the respective separated phases as
indicated in the following table:
TABLE IVA
Product
Aqueous
EXAMPLE IV
This test was conducted to illustrate that platinum The combined palladium stripped organic was then
and palladium may be stripped from a loaded secondary contacted with pH 1 HCl at an 01A ratio of 2 to 1 for
amine organic in the order (1) palladium, (2) platinum. 50 3 minutes at 25° C to scrub the organic phase. Follow-
An organic extraction solution was prepared and ing phase separation, the scrubbed organic phase was
preconditioned to chloride form as in Example III and analyzed and found to assay (in gil) platinum 1.00, and
used to contact an aqueous hydrochloric acid solution palladium 0.56. The scurbbed organic phase was .t~en
assaying (in gil) gold less than 0.001, platinum 1.70, contacted with a 50 gil solution of NaHC03contammg
pallaadium 4.59, iridium 0.025, ruthenium 1.10, and 55 5 gil EDTA which was prepared ~y adjusting an
rhodium 0.036. The emf of the aqueous solution was EDTA suspension in water to l?H 8 With NaOH s?lureduced
to - 525 millivolts by the addition of dry hy- tion to dissolve the EDTA, addmg NaHC03 and ddut.
droquinone prior to contacting the extraction o~ganic. ing with water to final volume. The organ~c was di-
A single organic/aqueous contact was then carned out vided into two equal aliquots. The first ahquot was
for three minutes at 25° C at an 01A ratio of 1/1. Fol- 60 contacted with the alkaline stripping solution for 10
lowing phase separation the organic extract phase was minutes at 25° C. Following phase separation, 5.1 grams
scrubbed by contacting pH 1 HCl for three minutes at of NaHC03 was dissolved in the aqueous phase to rean
organic to aqueous ratio of2 to 1. Analysis of each of store the alkaline solution.to 50 gil NaHC03
• The rethe
respective phases gave the following results. stored strippant solution was then used to contact the
TABLE IV 65 second aliquot for 10 minutes at 25° C. Both of the -------...,---A-m.:.o.:.u=nt=-=--:.---A-::s~Sa~y:-,g/::-;;--1 --- preceding contacts were carried out at an organic. to
ml O/A Pt Pd aqueous ratio of 2 to 1. No scum was observed dUrIng
850 1.70 4.59 the first contact and only trace scums were apparent at
Table III indicates that 94% of the platinum was Aqueous Scrub 412 2.0 0.009 0.02
stripped from the loaded organic while. less tha~ 0.03% 20 :::S::::cr~ub::::b::e=-d-=:O:.:.rg~a::n:::ic~_---.:8:..:2_5 1_.04 2_.6_O _
of the palladium was removed. The ratio of platmum to
palladium in the pregnant strip solution ~as gre~ter
than 1,000 to 1. Platinum stripped orgamc portions
(Nos. 1, 2 and 3) were combined and assayed (in. gil)
platinum 0.070 and palladium 3.48: The platmum 25
stripped organic was then scrubbed with IN HCl for 3
minutes at 25° C at an 01A ratio of 2 to 1. After phase
separation, the scrubbed organic phase was analy.zed
and found to assay (in gil) platinum 0.070 and palladIUm
3.50. The scrubbed organic was then contacted three 30
times in succession with a fresh solution of 50 gil
N2lL.2HCl in 0.5N HCl at an organic aqueous ratio of
2 to 1 for a period of 5 minutes, the phases being sep~.
rated after each contact. The separated aqueous strIp
solutions were combined and an analysis ofthe.aqueous 35
strip solution revealed that 75% of the palladIUm present
in the scrubbed organic and less than 2% of the
platinum had been stripped into the aqueous solution by
the acidic strip treatment.
The results of this test indicate. that an or~anicallr 40
substituted secondary amine orgamc loaded with platinum
and palladium may be selectively stripped from a
loaded secondary amine organic ina stripping sequence
in which platinum is first removed followed by pallailium.
~
4,041,126
50
55
12
separating said organic extract phase from said aqueous
raffinate phase,
contacting said organic extract phase with an acidified
aqueous solution of a. water soluble reducing
agent to form an aqueous phase loaded with palladium
and a platinum containing organic extract
phase,
separating said platinum containing organic phase
from said palladium containing aqueous phase,
contacting said platinum containing organic extract
phase with at least the stoichiometric quantity of an
aqueous alkaline stripping agent required for neutralization
of said extract phase, said contact resulting
in the formation of an queous phase loaded with
platinum and a stripped organic phase.
2. The process of claim 1 wherein R1 is a fatty alkyl
group.
3. The process of claim! wherein said aqueous acidic
medium is hydrochloric acid.
4. The process according to claim 3 wherein said
alkaline solution contains between about 5 and 100
grams per liter of an alkaline reagent.
5. The process of claim 4 wherein said alkaline reagent
is a water soluble member selected from the
group consisting of the carbonates, bicarbonates and
hydroxides of alkali and alkaline earth elements.
6. The process of claim 5 wherein a metal chelating
agent is added to said aqueous alkaline solution prior to
contacting said organic extract phase.
7. The process of claim 6 wherein said metal chelating
agent is an amino carboxylic acid compound:
8. The process of claim 1 wherein said reducing agent
is selected from the group consisting of acidified solutions
of hydrazine salts, hydroxylamine salts, and thiourea.
9. The process of claim 8 wherein said acidified reducing
agent is hydrazine dihydrochloride.
10. The process of claim 9 wherein said acidified
reducing solution is adjusted to between 0.1 and 3.0 N
HCI.
11. The process of claim 3 wherein said aqueous solution
is extracted in plurality of times by contacting the
aqueous raffinate phase and subsequent raffinates with
said organic extractant.
12. A continuous process for the selective separation
and recovery of platinum and palladium dissolved in an
aqueous chloride solution which comprises:
reducing said solution to an emf between about -425
mvand -650 mv,
contacting said aqueous chloride solution with a
mixed extraction reagent comprising a water immiscible
organic solvent having dissolved therein an
organically substituted secondary amine compound
of the general formula:
11
the interface of the second stripping contact. After
phase separation following the second stripping
contact, the stripped organic phases were combined and
the platinum pregnant strip solution was adjusted to pH
1 by addition of 12N HCI to stabilize the solution. As 5
in the preceding test, the percentage of platinum and
palladium stripped was determined by analysis of the
separated phases as indicated below:
Amount Assay, gil Grams % Stripped
Product ml Pt Pd Pt Pd Pt Pd
Pd stripped
organic
(scrubbed) 600 1.00 0.56 0.60 0.336
Pt stripped 15
organic 600 0.15 0.55 0.09 0.330 85 <2
Pt pregnant
strip 151 3.20 0.071 0.48 0.011
0.57 0.341
TABLEIVB
-----------::-----=,.------:c--::c-:--.,--10
The tabulated data indicate that the initial stripping 20
operation resulted in the strip of 78% of the palladium
and less than 1% of the platinum from the loaded organic.
The Palladium containing aqueous strip solution
had a palladium/platinum ratio of 69/1. The platinum 25
stripped organic contained 0.15 gil platinum and 0.55
gil platinum (85% and less than 2% stripped, respectively)
and the aqueous platinum containing strip solution
had a platinum/palladium ratio of 46/1. Compared
to the starting feed liquor of the process, the Pd/Pt ratio 30
was increased from 2.7/1 to 6911 and the Pt/Pd ratio
was increased from 0.4/1 to 46/1. Overall recovery
from the loaded organic was 85% for platinum and 79%
for palladium.
The platinum and palladium values may be won from 35
the respective aqueous stripping solutions using techniques
well known in the art (e.g., precipitation of ammonium
chloroplatinate with NILCI to recover platinum,
or precipitation of dichlorodiaminopalladium by
sequential addition of ammonium hydroxide and hydro- 40
chloric acid solutions to recover palladium).
What is claimed is:
1. A process for the separation and selective recovery
of platinum and palladium values from an aqueous
acidic medium which comprises: 45
contacting the medium with a mixed organic extraction
reagent comprising a water immiscible solvent
having dissolved therein an organically substituted
secondary amine compound of the general formula:
wherein R1 and Rz are hydrocarbon groups and R1 +
Rzcontain between 18 and 35 carbon atoms, said com-
65 pound having a solubility of at least 1% in said solvent
and being capable of forming complexes of platinum
and palladium that are preferentially soluble in the organic
solvent and whereby the contacting results in the
wherein R1 and Rz are hydrocarbon groups and R1 +
Rzcontain between 18 and 35 carbon atoms, said compound
being sufficiently soluble in said solvent to make 60
a 1% solution and capable of forming complexes with
platinum and palladium 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,
maintaining said medium at an emf of between about
-425 and -650 millivolts during said contacting
operation,
4,041,126
13
creation of an organic extract phase and an aqueous
raffinate phase,
separating said organic extract phase from said aqueous
raffinate phase,
contacting said organic extract phase with an aqueous 5
solution containing at least the stoichiometric quantity
of sodium bicarbonate required for neutralization
of said organic phase and the disodium salt of
ethylenediaminetetraacetic acid to form a stripped 10
organic extract phase and an aqueous platinum
containing strip solution,
contacting said stripped organic extract phase with an
aqueous solution containing from about 5 to about
100 grams per liter of hydrazine dihydrochloride to 15
remove palladium from said stripped organic extract
phase, and
contacting a fresh platinum and palladium containing
aqueous chloride solution with said platinum and
palladium stripped organic extract phase. 20
13. A continuous process for the separation and selective
recovery of platinum dissolved in aqueous chloride
solutions with palladium which comprises:
reducing said aqeuous chloride solution to an emf
between about -425 mv and -650 mv, 25
contacting said aqueous chloride solution for a predetermined
time period with an organic solvent containing
at least 1% by weight of an organically
substituted secondary amine compound of the general
formula 30
35
wherein R1 and Rz are hydrocarbon groups and R1 +
Rzcontain between 18 and 35 carbon atoms, said compound
having a solubility of at least 1% in said solvent 40
and being capable of forming complexes of platinum
and palladium that are preferentially soluble in the organic
solvent and whereby the contacting results in the
creation of an organic extract phase and an aqueous 45
raffinate phase,
isolating said extract phase from said raffinate phase,
14
contacting said extract phase with at least the stoichiometric
quantity of an aqueous alkaline solution
required to neutralize the chloride form of said
amine to selectively separate said platinum values
from said palladium values in said organic extract
phase. and form a platinum stripped organic extract
phase and an aqueous platinum containing strip
solution, and
isolating said aqueous solution from said platinum
extract phase.
14. A continuous process for the separation and selective
recovery of palladium dissolved in aqueous chloride
solutions with platinum which comprises:
reducing said solution to an emf between about -425
mvand -650 mv,
contacting said aqueous chloride solution for a predetermined
time period with an organic solvent containing
at least 1% by weight of an organically
substituted secondary amine compound of the general
formula:
wherein R1 and Rz are hydrocarbon groups and R1 +
Rzcontain between 18 and 35 carbon atoms, said compound
capable of forming complexes of platinum and
palladium that are preferentially soluble in the organic
xolvent and whereby said contacting results in the creation
of an organic extract phase and an aqueous raffinate
phase, •
separating said organic extract phase from said aqueous
raffinate phase,
contacting said organic extract phase with an aqueous
solution containing a reducing agent acidified to
between about 0.1 to about 3.0 N-HCl to strip
palladium values from said organic extract phase,
said contact resulting in the formation of a palladium
loaded aqueous phase and a stripped organic
phase containing said platinum,
separating said loaded aqeuous phase and said
stripped organic phase, and recovering palladium
from said loaded aqueous phase.
* * * * *
50
55
60
65
no<ĩet0�(D�e:none'>point of elemental sulfur.
* * * * *
14
ture between about 500 C and the melting point of
sulfur to convert substantially all of the sulfide
sulfur to elemental sulfur in solid form and to effect
conversion of the metal compounds to metal chlorides,
and recovering metal from the chlorides.
22. The process of claim 21 in which chlorination is
performed at a temperature between about 800 C and
the melting point of sulfur.
23. The process of claim 2] in which the minerals
10 contain silver.
24. The process of claim 23 in which the silver containing
mineral is tetrahedrite.
25. The process of claim 21 in which sulfur chlorides
formed during dry chlorination are reacted with the
15 metal sulfides to form metal chlorides and elemental
sulfur.
26. The process of claim 25 in which the process is
performed by introducing the metal sulfides and dry
chlorine gas countercurrently into the reaction zone
20 and an inert sweep gas is introduced into the reaction
zone to bring sulfur chlorides formed during the dry
chlorination into contact with metal sulfides entering
the reaction zone.
4,011,146
13
lead, silver recovered from the leach solution by cementation,
the leach solution after removal of lead and
silver therefrom recycled to the sodium chloride leaching
step, the improvement comprising preventing the
build-up of zinc in the leach solution in the leaching 5
step by removing a bleed stream from the lead and
silver depleted leach solution, removing zinc from the
bleed stream and recycling the bleed stream to the
leaching solution in the leaching step.
19. The process of claim 18 including subjecting the
bleed stream to electrolysis after removal of zinc therefrom
to produce chlorine gas and recycling the chlorine
gas to the dry chlorination step.
20. The process of claim 19 in which the zinc is removed
by precipitating it as zinc carbonate by the addition
of sodium carbonate, the sodium hydroxide produced
in the electrolyis is carbonated to sodium carbonate
and the sodium carbonate recycled to the zinc
precipitation step.
21. The process of recovering metal values from
minerals of the polymorphic series of complex metal
sulfides tetrahedrite-tennantite comprising:
a. subjecting the minerals to dry chlorination with
chlorine gas in the absence of oxygen at a tempera-
25
30
35
40
45
50
55
60
65