United States Patent [19]
Peters
[11]
[45]
4,071,357
Jan. 31, 1978
[54] PROCESS FOR RECOVERING ZINC FROM
STEEL-MAKING FLUE DUST
Attorney, Agent, or Firm-Sheridan, Ross, Fields &
McIntosh
803,472
1,706,143
1,780,323
1,879,834
2,144,299
3,849,121
A method for recovering a substantially impurity-free
zinc oxide product from steel-making flue dust or a
similar material which comprises leaching the flue dust
with concentrated ammonia and carbon dioxide to dissolve
zinc and unwanted impurities, cementing the
leach filtrate with zinc to remove copper, cadmium, and
lead impurities, conducting a steam distillation on the
cementation mtrate to precipitate basic zinc carbonate,
remove the ammonia and carbon dioxide, and iron impurities,
and filtering to provide a residue of essentially
basic zinc carbonate, sulfur, and chromium. This residue
is then washed to remove soluble sulfates, dried,
and calcined at high temperatures to break down the
basic zinc carbonate into zinc oxide, water washed to
remove chromium and the residue of the water wash
dried to produce the desired impurity-free zinc oxide
product. The two water washes may be combined into
one step performed after the calcining step to remove
both sulfur and chromium in one wash step.
[75] Inventor: Mark A. Peters, Arvada, Colo.
[73] Assignee: Hazen Research, Inc., Denver, Colo.
[21] Appl. No.: 725,929
[22] Filed: Sept. 23, 1976
[51] Int. Cl.2 C22B 19/24
[52] U.S. Cl 75/103; 75/109;
75/117; 75/120; 75/121; 423/105;423/622
[58] Field of Search 423/105, 622; 75/103,
75/109, 120
[56] References Cited
U.S. PATENT DOCUMENTS
10/1905 Cunnington 75/120 X
3/1929 Corbould 75/120 X
11/1930 Waring 75/120 X
9/1932 Waring et aI 75/120 X
1/1939 Sessions et aI 75/120 X
11/1974 Burrows 75/103
[57] ABSTRACT
Primary Examiner-G. Ozaki 5 Claims, 1 Drawing Figure
SOLIDS FEED
NH3/C02'
LIQUOR FEED
TAILS
DISTILLATION
FILTRATE
eASIC 2;INC
CARBONATE
STEAM
METAL
IMPURITIES
~;;,;,;;,;;....
ZnO
~
TZnO
PRODUCT
u.s. Patent
SOLIDS FEED-------,
NH3/C02
LIQUOR FEED
LEACH
Jan. 31, 1978
TAILS
CEMENTATION
4,071,357
STEAM
DISTI LLATION
i=ILTRATE
STEAM
DISTI LLATION
lIQ. METAL
11-----1
SOLID IMPURITIES
BASIC ZINC
CARBONATE
~
WASH TO
REMOVE SULFATE
CALCINE
6000 C
ZINC
PRODUCT
FILTRATION
OF INITIAL
PRECIPITATE
TO REMOVE Fe
H
2
0} Cr RECYCLE ~ rBLEED REMOVAL Cr
H2,O L1Q./
WASH ~OLlD
t
ZnO
ZnO
PRODUCT
4,071,357
BRIEF DESCRIPTION OF THE DRAWING
The single drawing is a flow sheet illustrating the
preferred embodiment of the invention.
DESCRIPTION OF THE PREFERRED
EMBODIMENT
The preferred embodiment of the invention is illustrated
by the flow sheet (FIG. 1). Flue dust contains
large amounts of zinc and iron, and smaller percentages
of copper, lead, sodium, chromium, nickel, manganese,
cadmium and other impurities. Although the dust is fine
grained, some clumping occurs when the dust is wetted
after being removed from the dust collection system,
and these clumps can be broken down to approximately
-10 mesh for the best results. This dust is then fed to a
leach at room temperature with ammonia and carbon
dioxide at high concentration. The duration ofthe leach
should be long enough to solubilize a substantial portion
SUMMARY OF THE INVENTION
The invention lies in a process for recovering a substantially
pure zinc product from steel-making flue dust
or other comparable waste materials containing impurities,
and especially copper, lead, cadmium, iron, sulfur
and chromium impurities. This objective is accomplished
by leaching the flue dust with concentrated
ammonia and carbon dioxide to solubilize a major portion
of the zinc in the dust and form a zinc-ammoniacarbonate
complex. The product of this leach is then
filtered and the solids, which contain zinc ferrite, can
either be discarded or processed further with acetic acid
to recover some of the zinc from the zinc ferrite in the
residue, as is well known in the art. The leach filtrate is
then cemented at room temperature with zinc to replace
impurities in the complex, such as lead, copper and
cadmium with zinc metal.
The cementation filtrate, by this point high in soluble
zinc content, is distilled with steam to remove ammonia
and carbon dioxide, and precipitate basic zinc carbonate.
It has been found that if approximately one percent
of the initial precipitate is removed, substantially all of
the iron in the cementation filtrate will be "scavenged"
by the precipitate and removed. The final steam distillation
product is then filtered and the filtrate discarded
from the process, resulting in a residue containing primarily
basic zinc carbonate with sulfur and chromium
impurities.
The residue is dried at approximately 1250 C, and
then washed to solubilize sulfur compounds in the basic
zinc carbonate. The basic zinc carbonate is then calcined
at a temperature high enough to break it down
into zinc oxide and carbon dioxide. A water wash of the
product of this calcining solubilizes chromium compounds,
resulting in a zinc oxide product after a final
drying at approximately 1250 C which is substantially
free of impurities. The two water wash steps may be
combined into a single step performed after calcining
the basic zinc oxide in order to remove both sulfur and
chromium impurities in a single step.
2
mium would still be left in the basic zinc carbonate
product of the steam distillation step.
It is obvious, then, from the above information and
from the state of the prior art that a method is needed
5 for separating and purifying zinc from steel-making flue
dust which can economically remove all of the metallic
impurities commonly found in flue dust, as well as result
in a substantially pure zinc product.
PROCESS FOR RECOVERING ZINC FROM
STEEL·MAKING FLUE DUST
BACKGROUND OF THE INVENTION
The invention lies in the field of treating waste materials
to recover zinc and other metal values.
Because of the nature of the operation of electric steel
furnaces, large amounts of scrap material can be fed into
the steel-making process, which was previously impos- 10
sible, and this is responsible for the large amount of zinc
contained in the flue dust from these furnaces. Due to
the high proportion of zinc in the dust, it is especially
desirable to further refine or treat the dust to remove
zinc values from this dust for sale. Naturally, if this dust 15
can be recovered in a simple and relatively inexpensive
manner, the commercial value of the zinc obtained
would help defray the cost of making steel, and some
gain could be recovered from formerly "waste" mate-
~ W
As is well known in the art, inherent in the process
for making steel by use of electric steel furnaces with
submerged arcs is the liberation of zinc, iron, and other
metal values as flue dust. This "flue dust" is usually
relatively high in zinc and iron, and also contains small 25
amounts of copper, cadmium, lead, sulfur, chromium
and other metals. Therefore, it is a primary purpose of
this invention to recover metal values from this steelmaking
flue dust, and particularly zinc values, and additionally
to provide a means for the separation and re- 30
covery of other materials in the dust should this be
desirable.
U.S. Pat. No. 2,805,918 to Van Hare, et aI., discloses
a method for leaching zinc-copper mixtures with an
ammoniacal-ammonium carbonate liquor to solubilize 35
the zinc and copper for subsequent separation. Although
this patent teaches a method for removing zinc
and copper from solution, this process would not be
satisfactory for use with flue dust as the initial feed
material, since flue dust does not contain only zinc and 40
copper values, but a multitude of other metallic values
which must also be removed to provide an essentially
pure zinc product. The method disclosed in the patent
for removal ofzinc is precipitation of the zinc by heating;
however, with amounts oHead, nickel, sulfur, chro- 45
mium, cadmium, and some iron in solution, these values
would also be precipitated by heat with a resultant
residue of little value because of its impurity. H. M.
Lawrence, in Bull. Am. Zinc. Inst., 10, No. 5-6, 107-18
(1927), discloses a process for first leaching a zinc ore 50
with an ammonium carbonate leach, and then cementation
with zinc to replace some impurities on the metal
sites of the complex with zinc and precipitate impurities;
however, Lawrence also was not working with
flue dust, which usually contains amounts of iron, chro- 55
mium and sulfur high enough to render a final product
treated by this method hopelessly impure.
"Transactions AIME," Journal of Metals (Vol. 180,
January 1950), p. 85, discloses a method for steam distilling
a pregnant nickel carbonate liquor to remove 60
impurities, including iron, and produce a basic nickel
carbonate product, and this procedure, coupled with
the product of Lawrence's cementation step, would be
a considerable development were nickel and zinc equivalent
metals. Obviously, however, one skilled in the art 65
would not equate nickel and zinc in most instances; and
even if these references were combined and used· to
treat flue dust, substantial amounts of sulfur and chro4,071,357
3
of the zinc in the solids feed. Copper, lead, sulfur, cadmium,
chromium, iron and other metal impurities will
also be solubilized. It has been found that at least several
hours of leaching is necessary to solubilize the zinc,
although this time is highly dependent on the mesh size 5
of the initial feed and other factors. The zinc, as well as
the other metals, forms a complex like a zinc-ammoniacarbonate
complex with the formula Zn(NH))7jCO).
The leach liquor is then filtered to remove the insoluble
matter, which has been found to contain predomi- 10
nately zinc ferrite. Some of the zinc can be recovered
from the residue by leaching with acetic acid. The leach
filtrate from the ammonium carbonate leach is then
passed to the cementation step. This step is conducted in
accordance with the disclosure of the H. M. Lawrence 15
article (supra). Here, zinc is introduced into the filtrate,
which is held at room temperature for several hours
throughout the cementation process.
Although the mesh size of the zinc cementation feed
is not of major consequence, large chunks of zinc have 20
been found to lengthen the time needed for satisfactory
cementation, and a - 20 mesh zinc was found to be the
preferred size of the zinc fed into the cementation step.
The zinc which is introduced into the filtrate replaces
metal impurities like copper, cadmium and lead on the 25
ammonium carbonate complex metal sites, and forces
these metal impurities out of solution as a precipitate.
The cementation product is then filtered and the solids
discarded from the process or further processed to recover
other metal values. At this point, the cementation 30
filtrate contains a high proportionate amount of zinc
and has been purified of virtually all impurities except
sulfur, chromium iron and manganese.
The filtrate is then fed to the steam distillation, or
"steam stripping" step, and water introduced as steam. 35
The introduction of steam to the system gradually increases
the temperature of the solution from room temperature
to approximately 800 _900 C. This steam distillation
drives off ammonia and carbon dioxide, which
can then be recycled to the original leach feed. It has 40
been found that if the steam distillation solution is filtered
immediately after the stripping process is begun,
when approximately one percent of the total precipitate
has settled out of solution, this precipitate will contain
essentially all of the iron impurities in the solution. This 45
residue can then be discarded and the steam stripping
continued until all of the zinc in solution has been precipitated
as basic zinc carbonate. The residue could be
further processed to recover additional metal values.
The steam distillation product is then filtered to sepa- 50
rate the liquid filtrate from the solid residue composed
of basic zinc carbonate and sulfur, chromium, and possible
impurities. The residue is dried and washed to remove
the water-soluble sulfur compounds. At this
point, the basic zinc carbonate residue still contains 55
chromium as an impurity. Substantially all of the other
impurities have been removed.
Thus, the only obstacle to obtaining a substantially
impurity-free zinc product is the chromium still a part
of the residue. It has been discovered that either water 60
washing before calcining or calcining not followed by
water washing will not remove chromium from the
basic zinc carbonate (see examples I and 2). The exact
temperature of the required calcine to break down the
basic zinc carbonate is unknown; however, a calcine at 65
temperatures of from approximately 2000 C up to the
sintering point of zinc oxide (approximately 11000 C),
succeeds in breaking down the basic zinc carbonate into
4
zinc oxide and, if followed by a water washing the
chromium will be removed to leave a high purity, high
grade zinc oxide product. This product can then be
dried and sold. In the drawing, it is indicated that chromium
may be bled off from the wash water to permit
recycling of the water. If water is recycled to the wash
without this bleed, it will become saturated with chromium
which will inhibit the removal of chromium.
The water wash to remove soluble sulfur compounds
may be performed before the calcine, or combined with
the post-calcine wash to remove chromium, and both of
these impurities removed simultaneously.
The following examples and tables are supportive of
the process disclosed above, and illustrate the efficiency
and completeness of the removal of impurities from the
zinc in the flue dust. However, these examples are not
to be construed as limiting the invention to the conditions
used therein. It is, obviously, well within the spirit,
scope and intent of this invention to vary temperatures
or processing times slightly, or to use this process in
connection with various other purification steps well
known in the art, or to apply this process to material
other than steel-making flue dust which has the same
basic components.
EXAMPLE I
A - 10 mesh, 106 lb. sample of steel-making flue dust
was leached at room temperature for 4 hours with
106 liters of 87 gil ammonia and 85 gil carbon
dioxide. An analysis of the solids feed by weight
percent, as well as the results of further treatment
of this dust, is contained in Table I below. An analysis
of the residue obtained from this leaching
shows a 54.7% extraction of zinc from the solids
feed, a 6.7% removal of iron, a 4.7% lead extraction,
43.4% cadmium removal,· and smaller percentages
of other impurities removed. This residue
was then discarded.
The filtrate from the leach was passed to cementation
at room temperature for 2 hours, with the addition of
2.84 gil -20 mesh Zn° dust (five times stoichiometric),
with the results again displayed in Table I. Of note is the
high efficiency of copper, lead, cadmium, and iron removal
by this step. This residue was also discarded,
with the filtrate being steam distilled and the initial
precipitate, which contained virtually all of the iron
impurities in the feed solution, being discarded. Table I
shows an analysis of the filtrate of this initial filtration
step. This steam stripping was then run to completion.
The sample was then split into two equal portions, with
Sample I left untreated further. Sample I from this
example was used as the feed material for Example 2.
Sample 2 was then calcined at 6000 C and analyzed as
shown in the last line of Table I. This final product was
then used as the feed material for Example 3.
It can be seen from this example that efficient removal
of most of the impurities contained in the initial
flue dust feed has been effected by the process of the
invention. However, the final product of this run, even
after the 6000 C calcine, still contained amounts of chromium
and sulfur large enough to keep the product from
being saleable. Also of importance is the weight percentageof
zinc in the final zinc oxide product, 73.2%,
while a pure zinc oxide product will contain 80.3 zinc.
The product of this process, without further treatment,
would beoflittle commercial value because of its impurity.
4,071,357
5 6
TABLE I
Recovery of ZnO from Steel Furnace Flue Dust
Unit Process an'ci
Data Description Zn Pb Cu Cd Fe Mn Cr NL S
NH, + CO, Leaching
Solids, Feed, Wt, % 22.7 4.41 0.27 0.095 28.1 3.38 0.146 0.76
Residue, WI. % 12.8 5.42 0.27 0.07 34.0 4.11
% Removed 54.7 4.7 23.0 43;4 6.7 6.1
Zn Cementation
Feed Leach Liquor, gil 53.8 0.58 0.22 0.20 0.082 0.014 0.20
Product Filtrate,gIl 54.9 0.005 <0.001 0.010 0.047 0.013 0.18
% Removal 99.1 >99.5 45.0 42.8 :::0
Steam Stripping .
Feed Liquor, gil 54.9 0.005 <0.001 0.010 0.047 0.013 0.18
Filtrate After Initial
Filtration, gil 52.6 0.005 0.001 0.02 0.004 0.01 0.11
Primary Filtrate Plus
Wash, gil '4.3 0.002 <0.001 <0.001 <0.001 <0.001 0.02
Dry Residue at 125' C and
Divide into Samples No. I
and No.2
Sample No. I, WI. % 52.6 0.09 0.63
Sample No. 2 After
Calcining at 600' C
without Wash, WI. % 73.2 0.009 <0.001 0.DI8 :::0.09 0.016 0.12 0.001 0.83
EXAMPLE 2
Sample No, 1from Example 1 was washed four times
for this example, with the results depicted in Table II 25
below. Virtually all of the sulfur in the sample was
removed by the washes, thus demonstrating the effectiveness
of the water wash to remove sulfur as soluble
by the results shown by these tables and examples, and
any omission of either of these steps, or a reversal in the
order thereof, produces an unusable, impure product.
As can be seen from Table III, the purity of the zinc
oxide product from this example was superlative; 80.2
weight percent zinc of a possible 80.3 weight percent
was obtained.
TABLE III
Sample
Description
Water Wash of Sample No.2 (After 600' C Calcine)
WtlVo!. Analyses
glml Cr S Zn Fe Pb Mn
Feed, Sample No. 2
from Table I
1st Filtrate
2nd Filtrate
3rd Filtrate
4th Filtate
Product, ZnO
After Drying
20.0g
68 ml
105 ml
93 ml
160 ml
.12 %
.316 gil
.054 gil
.008 gil
.0008 gil
.007 %
.83% 73.2% :::.09 .009% .016%
.03% 80.2% .071% .007% .010%
sulfate after the steam distillation step; however, in this
example as well as in Example 1, the zinc purity is not
commercially acceptable due to chromium contamination
of the product.
TABLE II
It is seen from the Description of the Preferred Embodiment
above, from the examples, and from the tables
and flow sheet illustrating the process of the invention,
that a new and useful invention has been made for puri-
Water Wash of Sample No. I
Sample WtlVo!. Analyses
Description glml Cr S Zn Fe Pb Mn
Feed, Sample No. I
from Table I 20.0g 0.09 % 0.63% 52.6%
1st Filtrate 52 ml 0.005 gil
2nd Filtrate 75 ml 0.002 gil
3rd Filtrate 81 ml 0.001 gil
4th Filtrate 157 ml 0.0002 gil
Product, Basic
Zinc Carbonate
After Drying 0.096 % 0.06% 59.6%
EXAMPLE 3
Sample No.2 from Example 1was water washed four
times for this example, just as in Example 2. The analy- 60
ses of the filtrates are shown in Table 3 below. However,
as noted in the description of Example I, this feed
material was first calcined to 600° C before washing.
The results of this wash show an excellent removal of
impurities, including chromium (which was reduced to 65
0.007 weight percent of the final product). It is the
calcining at high temperature, followed by water washing,
which removes chromium, as clearly demonstrated
fying the zinc contained in steel-making flue dust, or
other similar material, and that this invention fulfills all
of the conditions and objectives hereinabove set forth as
a desirable and commercially feasible means for recovering
zinc from flue dust.
What is claimed is:
1. A process for recovering metal values from a steelmaking
flue dust containing zinc, iron, lead, copper,
chromium and cadmium as impurities comprising:
a. leaching the feed material with ammonia and carbon
dioxide in high concentration and filtering to
• • • • •
15
8
2. The process of claim 1 in which in step (d) the
initial filtration step is performed when approximately
one percent of the total precipitate has been formed.
3. The process of claim 1 in which the zinc carbonate
5 precipitate of step (d) is washed with water to remove
sulfate before calcining.
4. In the process for recovering zinc from metal impurities
with which it is associated by dissolving the
zinc and metal impurities in ammonium carbonate fol-
IO lowed by precipitating the zinc as zinc carbonate by
steam distillation, the improvement which comprises
immediately filtering the steam distillation slurry after
steam distillation has begun to scavenge out the iron
content of the slurry.
5. In the process of producing zinc oxide from zinc
carbonate by calcination, the improvement for producing
a chromium-free zinc oxide which comprises calcining
the zinc carbonate at a temperature between 200·
C-llOO· C and washing the formed zinc oxide product
20 in water.
4,071,357
7
produce a leach residue and a filtrate containing
zinc values and the impurities;
b. cementing the leach filtrate from step (a) with zinc
to remove lead, copper and cadmium and performing
a liquid/solids separation on the resulting
slurry;
c. steam distilling the cementation filtrate from step
(b) to precipitate basic zinc carbonate;
d. performing an initial liquid/solids separation on the
steam distillation slurry of step (c) immediately
after steam distillation has begun to scavenge out
the iron content of the slurry and then continuing
the steam distillation until all of the zinc has precip"
itated as zinc carbonate;
e. calcining the zinc carbonate precipitate of step (d)
at a temperature between 200· C-llOO· C to convert
the zinc carbonate to zinc oxide; and
f. washing the zinc oxide product of step (e) in water
to remove sulfate and chromium converted to the
soluble form by the calcination of step (e).
25
30
35
40
45
50
55
60
65
<9l�fn<�� style='margin-bottom:0in;margin-bottom:.0001pt;line-height: normal;mso-pagination:none;mso-layout-grid-align:none;text-autospace:none'>for combustion during the conversion step.· 30
43. The process of claim 42 in which sufficient fuel is
added to the charge to provide additional heat upon
combustion in the process to raise the temperature of
the charge to at least about 1100· F.
44. The process of claim 42 in which the fuel is car- 35
bon.
45. The process of claim 44 in which the carbon is
added in an amount from about 3 to 5 weight percent of
the iron carbide charge.
46. A process of making steel from iron carbide in the 40
basic oxygen furnace which comprises adding pig iron
10
to the iron carbide charge and controlling the temperature
of the charge by the addition of iron carbide.
47. The process of claim 46 in which the pig iron is
added in an amount up to about 40 weight percent ofthe
charge and the temperature controlling iron carbide is
added in an·amount up to about 60 weight percent ofthe
iron carbide-pig iron charge. .
48. A process for concentrating non-magnetic low
grade iron ores ·which comprises converting the iron
oxide in the ores to iron carbide and separating the iron
carbide and gangue by subjecting the treated ores to
magnetic separation.
- 49. The process of claim 48 in which the iron oxides
are converted to iron carbide in one step in a fluidized
bed with a mixture of hydrogen bearing gas and a carbon
containing material which provides carbon for the
iron carbide.
50•. The process of claim 49 in which hydrogen is
present in an amount of over 60 percent by volume of
carbon monoxide in the fluidized bed.
51. A process for the direct production of steel from
iron oxides which comprises:
a. converting the iron in the oxides to iron carbide;
and
b. converting an iron in the iron carbide directly to
steel in an electric furnace.
52. A process for the direct production of steel from
iron oxides which comprises:
a. reducing the oxides and converting the iron to iron
carbide in one step in a fluidized bed with a mixture
of a hydrogen bearing gas and a carbon containing
material which provides carbon for the iron carbide,
the hydrogen being present in an amount exceeding
50% of the CO present; and
b. adding the iron carbide to the electric furnace and
processing it to steel in an electric furnace.
53. The process of claim 52 in which steps (a) and (b)
are performed in conjunction and the iron carbide produced
in step (a) is added directly to the electric furnace
without substantial heat loss.
* * * * '"
45
50
55
60
65
le='�b~p-i��font-family:"Times New Roman","serif";mso-fareast-font-family: HiddenHorzOCR'>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