27 Claims, No Drawings
4,290,866 9/1981 Bolton et al. 204/119
OTHER PUBLICATIONS
Giganov et aI., "Chem~ Abstracts", vol. 70, 1969,
#23535n.
Greenberg, "Chem. Abstracts", vol. 66, 1967, #67990d.
Primary Examiner-Herbert T. Carter
Improvement in electrowinning manganese dioxide, or
zinc in which the relative concentration of manganese
or zinc ions to impurities is enhanced by selectively
extracting manganese. or zinc ions from a bleed taken
from the electrowinning feed stream with an organic
extractant, while rejecting impurities, stripping the
loaded organics with spent electrolyte, and recycling
loaded strip to the electrowinning feed. Stripped organic
may be regenerated with an alkaline agent such as
calcium oxide or magnesium oxide prior to recycle, and
pH may be controlled during extraction by the same
means.
United States Patent [19]
Reynolds et ale
[54] MANGANESE AND ZINC SOLVENT
EXTRACTION PROCESS
[75] Inventors: James E. Reynolds, Golden; Nicholas
J. Lombardo, Boulder, both of Colo.
[73] Assignee: Hazen Research Incorporated,
Go1den,Colo.
[21] Appl. No.: 336,502
[22] Filed: Dec. 31, 1981
[51] Int. Cl.3 COlG 9/00; C01G 45/00
[52] U.S. Cl. 423/49; 423/99;
204/105 M; 204/114
[58] Field of Search 423/49, 99; 204/114,
204/105 M
[56] References Cited
U.S. PATENT DOCUMENTS
3,399,055 8/1968 Ruthy 75/119
3,479,378 11/1969 Orlandini et al. 423/49
3,996,334 12/1976 Hartman et al. .
4,272,492 6/1981 Jensen 423/24
4,279,870 7/1981 Nathansohn 423/54
[57]
[11]
[45]
ABSTRACT
4,423,012
Dec. 27, 1983
SUMMARY OF THE INVENTION
The concentration of manganese and/or zinc is enhanced,
while impurities are removed from aqueous
solutions by means of solvent extraction with an organic
extractant such as di-ethylhexyl phosphoric acid
(DEHPA). Two or three stages of extraction selectively
load the desired metals at a carefully controlled
pH, leaving a barren raffinate containing unwanted
soluble impurities such as alkali metals and alkaline
earths. The extractant is stripped withan acidic aqueous
solution, and when the feed solution is a bleed stream
from an electrowinning circuit, it has been found that
spent electrolyte, still containing a significant concentration
of the desired metal, may be effectively used to
accomplish this step.
The extractant, returned to the hydrogen form by
means of the stripping, may be recycled and contacted
with fresh feed. As the desired metal loads onto the
2
Accordingly, the objects of this invention are to enhance
the concentration of the desired metals, manganese
or zinc, with respect to impurities while reducing
the relative concentrations of the undesirable impurities
5 in electrowinning solution feeds; and to provide a mechanism
for removing water from balanced hydrometallurgical
processes with electrowinning circuits.
Prior Art Statement
Methods for removing a number of metals from aqueous
solution by solvent extraction are known to the art.
U.S. Pat. No. 4,272,492, issued June 9, 1981 to Jensen,
for "Selective Extraction And Recovery Of Copper"
discloses a method for recovering copper from an acidic
chloride solution with a solvent extraction agent, which
requires stripping the extractant with an aqueous solution,
re-extracting copper with a hydrogen ion exchange
extractant, and restripping with an aqueous
acidic solution. U.S. Pat. No. 4,279,870, issued July 21,
20 1981 to Natansohn, et al., for "Liquid-Liquid Extraction
Process For The Recovery Of Tungsten From Low
Level Sources," discloses a process for extracting tungsten
from an aqueous solution by means of an organic
extractant comprising a chelating agent, an organic
transfer agent and an inert organic solvent. Chemical
Abstracts, Volume 66, 1967, at 67995j, discloses a process
for solvent extraction of indium using bis (2-ethylhexyl)
phosphate and mono-2-ethylhexyl phosphate.
Chemical Abstracts, Volume 70, 1969, at 23535n, discloses
a process for indium extraction from sulfate solution
using bis (2-ethylhexyl) H phosphate and kerosine,
pretreating the solution with metallic iron to reduce
ferric concentration. Depending on the metals to be
separated, and the type of feed solutions involved, reagents,
parameters, and processing steps for solvent extraction
processes vary widely. None of the foregoing
prior art deals with the separation of manganese and/or
zinc from electrolytes with the express purpose of removing
impurities.
U.S. Pat. No. 4,290,866, issued Sept. 22, 1981, to
Bolton, et al. discloses a process for removing manganese
from an electrowinning solution containing zinc
and manganese comprising oxidizing the manganese to
manganese dioxide with ozone, and removing manganese
dioxide from the solution.
U.S. Pat. No. 3,399,055 to Ritcey, et al. on Aug. 27,
1968, describes a solvent extraction process for the
separation of cobalt from nickel in a sulfate solution
using DEHPA at a carefully controlled pH.
4,423,012
1
DESCRIPTION
MANGANESE AND ZINC SOLVENT
EXTRACfION PROCESS
1. Technical Field
The process of the present invention relates to the
recovery of manganese and zinc ions from aqueous
sources by liquid-liquid solvent extraction. More partic- 10
ularly it is concerned with a method for increasing the
relative concentration ofdesired metal ions with respect
to impurities in electrowinning feed solutions.
2. Background Art
Manganese and zinc are commonly recovered from 15
their ores by leaching the ores with sulfuric acid, followed
by liquid/solid separation and an electrowinning
step. A common problem to all circuits, in varying
degrees and importance, is the build-up of soluble impurities
not removed by conventional purification procedures
such as sulfiding to precipitate heavy metal sulfides,
and oxyhydrolysis or pH adjustment to remove
iron. For example, potassium build-up in electrolytic
manganese dioxide processing is harmful to the battery
quality of the manganese dioxide product; and, magne- 25
sium build-up in manganese and zinc electrowinning
circuits is a common problem because most commercial
ores and concentrates contain dolomite and clay minerals.
Another soluble impurity is chloride ion. It is harmful
in a number of ways, e.g., corrosion of lead alloy 30
anodes and pitting of cathode deposits. Chloride can
enter the electrolytic circuit as an impurity in the ore
feed as in rhodochrosite manganese ores, or with water
makeup.
Zinc electrowinning is accompanied by some deposi- 35
tion of unwanted manganese dioxide on the anode.
These deposits slough off and build up as sludge in the
cell tanks and increase cell voltage. Manganese cannot
be removed by sulfiding, so it builds to high levels in the
circulating electrolyte. 40
Fluoride ion is harmful in zinc electrodeposition
using aluminum cathode sheets. A small purge or bleed
of the circuit can prevent a large number of cycles of
concentration of fluoride ion from exceeding about 2
ppm where its effect becomes evident by sticking of 45
zinc deposits to the cathode.
Most electrowinning circuits are saturated with calcium
sulfate at 2 to 3 grams per liter. Gypsum (CaS04.
2HzO) is deposited on cold surfaces such as tank walls,
pipelines, etc. Anhydrite (CaS04) grows as a tenacious 50
scale on hot surfaces (due to inverse solubility) such as
steam heated exchangers, and on all surfaces in manganese
dioxide cells operated at 90° C. to 95° C. because
the electrolyte changes its composition due to evaporation
and electrolytic production of sulfuric acid. These 55
complications can be avoided by a small purge of electrolyte
and replacement with calcium-free solution so as
to unsaturate the solution with respect to calcium.
Another problem, common to most hydrometallurgical
processes is water balance, Le., careful control of 60
water added to closed loop circuits. Water enters the
process at a number of points, including direct steam
injection for solution heating; however, normal evaporative
losses and moisture removed in leach tailings
often do not keep pace with water addition. Thus, an 65
alternate method to remove water, other than energyintensive
evaporation, is an advantage of a purification
process for purging water as well as soluble impurities.
4
Optionally, about 5 volume percent isodecanol may be
added to prevent formation of a third phase.
Preferably, the organic to aqueous ratio in the extraction
tank is between about 0.5 and 4 to 1, and more
5 preferably between about 1 to I and 2 to 1.
The pH of the mixture in the extraction tank is carefully
monitored, and a neutralizing agent is added as
necessary to control the pH to between about 1 and
about 5. When the pH drops below about 1, overall
extraction of manganese is inhibited. Preferably the pH
is maintained at between about 2.5 and about 5.0 to
maximize loading of the manganese on the extractant,
and more preferably between about 3.5 and about 4.3 to
minimize the number of extraction stages necessary and
prevent phase separation problems which may occur
above pH about 4.3. Manganese can be separated from
magnesium and potassium over a wide pH range; however,
the above considerations dictate a pH between
about 2.5 and about 5.0 Calcium extraction is at its highest
(about 60 percent) at a pH of around 2.0, and drops
gradually down to about 30 percent at pH 5.0. Suitable
neutralizing agents are known to the art, and may be
selected based on economics and ultimate disposition of
the barren raffinate. Some preferred neutralizing agents
include calcium oxide, magnesium oxide, ammonia, and
sodium hydroxide. Preferably calcium oxide or magnesium
oxide is added to the first extraction stage; optionally
sodium hydroxide may be used to control pH in the
30 subsequent stages to improve pH control.
A temperature during the extraction stages of between
about 20° C. and about 40° C. is preferred. When
calcium oxide is used as the neutralizing agent, heating
up to 40° C. during extraction helps to minimize emulsion
formation.
A mixing time for each stage of about 3 minutes is
preferred.
The extraction is conducted in counter-current
stages, with fresh aqueous fee~ being,introduced into a
first vessel and cycled successlVely through each vessel
to the last, while fresh extraction agent is introduced
into the last vessel and cycled successively backwards
through each vessel to the first, loaded extractant being
withdrawn from the first vessel for stripping, and barren
aqueous solution being withdrawn from the last
vessel. The number of stages depends on the desired
extraction percentage, and it has been found that up to
98.2 weight percent manganese can be extracted in
three stages, with good rejection of magnesium, e.g.,
down to 1.3 weight percent extraction, and good rejection
of calcium, chloride, potassium, and sodium, e.g.,
down to less than 0.5 weight percent extraction each.
Following the last extraction stage, the raffinate may
be processed as desired for recovery of magnesium
sulfate, if substantial quantities of magnesium are present
therein. The raffinate may then be sent to provide
makeup water to the organic regeneration step as hereinafter
described.
The organics are scrubbed with water at a pH of less
than about 1, preferably with an acid content of about 5
to about 50 gil, at an organic to aqueous ratio of between
about 1 to 1 and 4 to 1, and preferably about 3 to
1, using a mixing time of about 2 minutes, and at ambient
temperature, heating up to about 40° C. when necessary
to minimize emulsions. The flow rate through the scrub
mixer can be somewhat faster than through the extractors.
The scrub removes less than about 0.5 weight
percent manganese, and minimal amounts of other im-
4,423,012
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS
[HDEHP]org+[NaOH]aq->[NaDEHP.H20 ]org
3
organic extractant, hydrogen ion is released, and a neutralizing
reagent such as magnesium oxide, calcium
oxide, ammonia, or sodium hydroxide, is supplied in
necessary quantities to the extraction mixtures to control
the pH according to the reaction (for NaOH):
Optionally, or in addition to neutralization in the mixers,
prior to being recycled to contact fresh feed, the 10
stripped extractant may be regenerated, as necessary,
with an alkaline agent, preferably with calcium oxide or
mangesium oxide to replace hydrogen on the extractant
with a cation which will not disrupt the pH of the system
upon loading. 15
When calcium oxide is used as the regeneration reagent,
the process includes provision for removal of
gypsum which precipitates during extraction when
fresh extractant enters the system and the calcium form
of DEHPA exchanges with manganese or zinc cations
and combines with sulfate in the aqueous phase to form 20
crystalline CaS04. 2H20. A settler generally removes
the excess gypsum. When magnesium oxide is used as
the regeneration reagent, a high-strength MgS04 raffinate
is produced, and MgS04 may be recovered by
conventional evaporation/crystallization to produce a 25
high-purity epsom salt (MgS04. 7H20).
A water scrub following the extraction stages is
sometimes desirable in order to remove any impurities
contained in the entrained aqueous component.
In a preferred embodiment of the invention, a bleed
stream taken from an electrowinning circuit for recovery
of manganese dioxide is treated to enhance the con- 35
centration of manganese, and reduce the concentration
of impurities therein, such as calcium, magnesium, chloride,
potassium, and sodium.
A typical feed solution for the electrowinning of
manganese dioxide contains between 40 and 60 gil man- 40
ganese, between 5 and 30 gil magnesium, between 0.5
and 1 gil calcium, between 0.1 and 2 gil chloride, between
0.5 and 2 gil potassium, and between 1 and 3 gil
sodium.
The process of this invention effectively extracts and 45
returns to the circuit up to about 98 weight percent of
the manganese, while returning to the circuit as little as
1.8 weight percent of the magnesium originally present,
and 0.4 weight percent of the sodium originally present,
and essentially eliminating chloride and potassium, 50
while reducing calcium by one-half. The loaded aqueous
solution resulting from this process is suitable for
cycling back. into the electrowinning cell to enhance
overall manganese dioxide recovery.
Typically, the bleed stream is at a pH of between 55
about 4.5 and 6.5, and preferrably about 5.5, and will be
at a temperature of between about 30° and 55° C.
The bleed stream enters a first extraction mixer-settler
tank where it is contacted with an organic extractant.
The preferred extractant is di-ethylehexyl phos- 60
phoric acid (DEHPA) in a low-aromatic diluent such as
Escaid 200. Escaid 200 is a proprietary trademark of
EXXON Company, P.O. Box 20224, Dallas, Tex.,
75220, and consists of normal paraffin hydrocarbons.
Preferably, DEHPA is present in the extractant at 65
between about 10 and 50 volume percent, and preferably
between about 20 and 30 volume percent, and the
balance of the extractant is compised of Escaid 200.
4,423,012
Example 2
Aqueous Extraction Stages (Mn)
The aqueous solutions of Tests 1 and 2 of Example 1
were contacted with organic extractant with a composition
as described in Example 1 in a number of stages,
reusing the aqueous solutions, but supplying fresh extractant
for each stage, under the conditions described
in Example 1. Results are set forth in Table 2.
TABLE 1
Stage No. 2 4
Test 1 pH 4.07 4.14 4.05 4.06 4.07
Aqueous = Organic
21.4 gil Mn MgO (gil) 7.3 1.0 0 0 0
2.61 gil Mg Mn (gil) 6.51 10.4 10.6 10.3 13.0
Aqueous
Mn (gil) 1.88 9.65 20.9 22.2 22.4
Test 2 pH 4.3 4.2 4.4 4.5
Aqueous = Organic
53.2 gil Mn MgO (gil) 10.3 0 0 0
26.1 gil Mg Mn (gil) 13.9 16.9 19.9 20.6
Aqueous
Mn (gil) 11.5 44.3 45.5 50.0
EXAMPLES
Example 1
Organic Extraction Stages (Mn)
Aqueous solutions containing manganese and magnesium
as set forth in Table 1 were contacted with an
extractant composed of 80 percent Escaid 200 and 20
percent DEHPA by volume, conditioned with 150
grams per liter H2S04, in a number of stages, reusing
the organic, but supplying fresh aqueous solutions for
each stage, at an organic to aqueous ratio of 3 to 1, a
temperature of 20° C., a contact time of 5 minutes per
stage and a pH as shown in Table 1. Results are set forth
in Table 1.
50
6
cent, calcium down to 0.1 weight percent, and fluoride
down to about 27.5 weight percent, with complete rejection
of chloride ion. The aqueous scrub removes less
than 0.1 weight percent of the zinc present in the organ-
5 ics, but may remove up to 27.6 weight percent of the
fluoride present. The strip solution preferably contains
between about 30 and about 60 grams per liter zinc, and
most preferably about 50 grams per liter zinc, and about
1 120 grams per liter sulfuric acid. Up to about 80 weight
o percent of the zinc originally present in the feed is recovered
in the strip solution for recycle to the electrowinning
circuit, while manganese is rejected down to
about 1.6 weight percent originally present in the feed,
15 magnesium down to less than 0.1 weight percent originally
present in the feed, calcium down to about 0.1
weight percent originally present in the feed, while
chloride is essentially eliminated. Fluoride is reduced
down to about 5 weight percent originally present in
20 the feed. .
From the foregoing it can be seen that manganese and
zinc can be effectively separated from a number of
impurities, and the process can be used to increase the
efficiency of manganese dioxide and zinc electrowinning
circuits both by enhancing recovery of manganese
or zinc metals and by re{1ucing problems associated
with typical impurities in the circuits.
5
purities, although it may remove about 33 weight percent
chloride ion. Scrub water may be recycled and
re-used for scrubbing. Scrub aqueous may also be cycled
back to the first extraction stage.
The scrubbed organic is then stripped, preferably
with spent electrolyte from the electrowinning circuit.
This spent electrolyte may contain up to about 150
grams per liter manganese, and preferably contains
between about 25 and 50 grams per liter manganese.
The spent electrolyte also typically contains between
about 20 and 50 grams per liter sulfuric acid.
The strip solution is adjusted as necessary to a pH of
less than about 1.0. The strip is conducted at ambient
temperatures and at an organic to aqueous ratio of between
about 0.5 and 2.5 to 1, and peferably about 2 to 1.
Preferred mixing time is between about 1 and about 5
minutes, and preferably about 2 minutes.
The strip removes up to 99.2 weight percent of the
manganese present in the organics.
The loaded strip is recycled to the electrowinning
circuit, and the barren organics are sent to organic regeneration
where they are contacted with an alkaline
reagent such as a slurry of magnesium oxide or calcium
oxide. Preferably the slurry is comprised of between
about 150 and about 250 grams per liter and more pref- 25
erably about 200 grams per liter magnesium oxide in
recycled raffinate.·1[ calcium oxide is used, the slurry
preferably contains about 150 grams per liter calcium
oxide.
The mixing time for organic regeneration is prefera- 30
bly between about 5 and 10 minutes, at ambient temperatures.
When calcium oxide is used as the regeneration
reagent, it is preferably also used in the [mal extractant
stage for pH adjustment, and any calcium sulfate precipitated
is removed by means of settlers. When magne- 35
sium oxide is used as the organic regeneration reagent,
magnesium sulfate, which remains soluble, is carried off
in the raffinate and recovered prior to recycle of the
raffinate by means known to the art such as crystallization.
The regenerated organics are cycled directly to 40
the final extraction stage.
The foregoing process is also suitable for enhancing
the concentration of zinc with respect to other impurities,
including manganese, in zinc electrowinning circuits.
Typical zinc electrowinning feed solutions may 45
contain between about 100 and about 150 gil zinc, and
preferably about 120 gil zinc, and may include manganese
in concentrations of up to about 10 gil. Fluorine
may be present as an impurity in concentrations of up to
about 20 ppm.
The preferred extractant is DEHPA, in a 50-50 mixture
with a diluent such as Escaid 200. Zinc is also
effectively extracted with extractants comprising down
to about 30 percent DEHPA and about 70 percent diluent.
The preferred organics to acqueous to ratio is be- 55
tween about 3 to 1 and about 4 to 1, and preferably
about 3.5 to 1. Ambient temperature may be used. Preferably
the mixers are heated to between about 30° C.
and about 40° C. to break emulsions; and, when calcuim
oxide is used for organic regeneration and pH control, 60
heating to about 40° C. during the extraction and scrub
stages is preferred.
The preferred pH for efficient zinc extraction is between
about 2 and 2.5, and preferably about 2.3.
Zinc may be extracted in three stages up to 99.9 65
weight percent ofthe zinc originally present in the feed,
with manganese rejected down to about 1.6 weight
percent, magnesium down to less than 0.1 weight perAqueous
Extraction Stages (Zn)
The aqueous solution of Example 3 was contacted
10 with the organic extractant of Example 3 in two stages,
reusing the aqueous solution, but supplying fresh extractant
for each stage, under the conditions described
in Example 3. Results are set forth in Table 4.
4,423,012
7
TABLE 2
Stage No. I 2
Test I pH 4.07 4.10
Aqueous = Organic
21.4 gil Mn MgO (gil) 7.3 7.0
2.61 gil Mg Mn (gil) 6.51 0.60
Aqueous
Mn (gil) 1.88 0.103
Test 2 pH 4.3 4.1
Aqueous = Organic
53.2 gil Mn MgO (gil) 10.3 7.3
26.1 gil Mg Mn (gil) 13.9 3.3
Aqueous
Mn (gil) 11.5 1.52
3 4
4.04 4.10
7.3 7.3
0.04 0.005
0.006 0.002
4.2 4.1
9.3 8.7
0.5 0.02
0.080 0.009
5
Stage No.
Aqueous
Zn (gil)
Example 4
8
TABLE 3-continued
1 2
0.085 1.41 41.5
4
80.0
15
Example 3
Organic Extraction Stages (Zn)
An aqueous solution containing 127 grams per liter
zinc, 3.07 grams per liter manganese, and 8.34 grams per 20
liter magnesium was contacted with an extractant composed
of 50 percent Escaid 200 by volume and 50 percent
DEHPA conditioned with 150 grams per liter
H2S04 in four stages, reusing the organic, but supplying
fresh aqueous solution for each stage, at an organic to 25
aqueous ratio of4 to 1 a pH of 2.1 to 2.2 maintained with
150 grams per liter MgO, at a temperature of 20· C. for
a contact time of 5 minutes per stage. Results are set
forth in Table 3.
TABLE 3
30
Stage No. 2 3 4
Organic
MgO (gil) 9.4 21.1 11.8 0.1
Zn (gil) 0.33 23.5 44.9 56.7 35
TABLE 4
Stage No. 2
Organic
MgO (gil) 9.4 6.9
Zn (gil) 0.33 .01
Aqueous
Zn (gil) 0.085 0.045
Example 5
Extraction and Strip Results
Aqueous solutions containing manganese in Tests 1-5
and zinc in Tests 6-8 as set forth in Table 5 were extracted
with a DEHPA organic extractant of a composition
set forth in Table 5 under the indicated conditions.
The loaded organics were scrubbed with a water
scrub at pH 4 prior to stripping. Results are set forth in
Table 5 in terms of percent of feed components extracted.
The pH adjustment reagent set forth in the
table was added to the last extraction stage, arid pH
adjustment in earlier stages was accomplished with
sodium hydroxide.
TABLE 5a
PARAMETERS
Extractant
Test No.
1
2
34
5
6
7
8
Zn
127
127
133
Mn
43.6
41.3
53.6
53.6
54.0
3.07
3.07
2.97
Aqueous Feed (gil)
MgCa C1 K
14.4 .599 .059 .009
14.4 .599 .059 .009
3.1 .733 .134 .645
3.1 .733 .134 .645
15.4 .586 .072 .244
8.34 .505 0.15
8.34 .505 0.15
5.47 .880 .112
TABLE 5b
Na
.068
.068
.620
.620
F
.003
.003
<.001
Escaid
DEHPA 200
30% 70%
30% 70%
30% 70%
30% 70%
30% ,,7,0%
40% "60%
40% 60%
30% 70%
PARAMETERS
pH Control
O/A T No. of Reagent Strip (gil)
Test No. Phase ratio rC.) Stages (gil organic) Zn Mn H2SO4
Extraction 3/1 30-40 3 MgO-23.4 33 50
Strip 2.411 20-25 2 H2S04-pH < I
2 Extraction 3.6/1 30-40 3 MgO-9.3 33 50
Strip 2.7/1 20-25 2 H2S04-pH < I
3 Extraction 3,.3/1 30-40 3 MgO-12.3 36 30
Strip 2.6/1 20-25 2 H2S04-pH < I
4 Extraction 3/1 20 2 MgO-13 36 30
Strip 2.6/1 20 1 H2S04-pH < I
Extraction 3.2/1 35-40 2 NaOH-pH4* 34.6 50
Strip 6/1 35-40 1 H2S04-pH < 1
6 Extraction 3.5/1 30-40 3 MgO-20.7 50.5 120
Strip 1.3/1 20 2 H2S04-pH < 1
7 Extraction 3.6/1 30-40 3 Ca(OH)2-12.6* 50.5 120
Strip 1.5/1 30-40 2 H2S04-pH < I
8 Extraction 4/1 35-40 3 NaOH-pH2* 50.5 120
9
TABLE 5b-continued
4,423,012
10
O/A T
Test No. Phase ratio ('C.)
PARAMETERS
pH Control
No. of Reagent
Stages (gil organic)
Strip (g/!)
Strip 1.5/1 35-40
*Ca(0H)2 used for organic regeneration
TABLE 5c
RESULTS
Extraction (% of Feed)
Test No. Product Zn Mn Mg Ca CI K Na F
Loaded Organic 93.9 2.9 100 12.3 0 14.0
Loaded Strip 67.3 2.9 148 12.3 0 14.0
2 Loaded Organic 98.2 2.5 89.6 27.1 0 0.4
Loaded Strip 64.4 7.0 50.7 . 27.1 0 0.4
3 Loaded Organic 99.7 1.8 49.3 0 0.7 0.4
Loaded Strip 65.1 1.8 49.3 0 0.7 0.4
4 Loaded Organic 95.7 6.3 0.4 12.1 1.4 1.5
Loaded Strip 63.9 6.3 51.1 12.1 1.4 1.5
5 Loaded Organic 98.0 16.0 15.3 1.6
Loaded Strip 60.7 16.0 15.3 1.6
6 Loaded Organic 99.4 3.4 <0.1 0.9 1.8 39.8
Loaded Strip 5\.3 3.4 <0.1 5.7 28:5
7 Loaded Organic 94.8 1.6 0.1 0.1 0 2.75
Loaded Strip 49.0 1.6 0.1 0 0
Loaded Organic 99.9 7.3 0.6 0.8 10.7
Loaded Strip 79.6 7.3 0.6 0.8 10.7
What is claimed:
1. In a process for recovering a desired component 30
selected from the group consisting of manganese and
zinc by electrowinning the desired component from an
aqueous solution containing impurities selected from
the group consisting of magnesium when said desired
component is zinc and potassium, when said desired 3S
component is manganese, the improvement comprising
substantially reducing the amount of at least one of the
aforesaid impurities in the electrowinning feed solution
and substantially increasing the amount of metal ions of
the desired component therein by: 40
a. mixing an aqueous bleed stream from said electrowinning
feed solution with a solvent extraction
agent comprising diethylhexylphosporic acid as an
organic extraction agent and an organic solvent
therefore to form mixture having a pH of from 45
about 1 to about 5 and an organic to aqueous ratio
of from about 0.5 to about 4 to selectively extract
desired metal ions;
b. separating the aqueous and organic portions of the
mixture of step (a); 50
c. stripping the loaded organic extractant of step (b)
with a dilute acidic solution;
d. recycling the loaded strip solution of step (c) to
said electrowinning process.
2. The process of claim 1 in which the strip solution 55
of step (c) is spent electrowinning solution from the
process.
3. The process of claim 1 in which the pH of the
mixture of step (a) is adjusted with a pH-adjusting reagent
to between about I and about 5. 60
4. The process of claim 3 in which the pH adjusting
reagent is at least one reagent selected from the group
consisting of calcium oxide, magnesium oxide, sodium
hydroxide, and ammonia.
5. The process of claim 1 or claim 3 in which the 65
stripped organic extractant is regenerated with a reagent
selected from the group consisting of calcium
oxide and magnesium oxide.
6. The process of claim 5 in which the selected regeneration
reagentisalso used as the pH-adjusting reagent
iii step (a). .
7. The process of claim 6 in which magnesium oxide
is the pH-adjusting reagent, and a magnesium salt is
recovered from the aqueous raffinate of step (b).
8.. The process of claim 1 or claim 2 in which the
desired metal ions are manganese ions, and the impurities
to be reduced also include potassium and sodium
ions.
9. The process oCclaim 4in which the pH is maintained
between about 2.5 and about 4.3.
10. The process of claim 1 or claim 2 in which the
desired metal ions are zinc ions, and the impurities also
to be reduced include manganese, calcium, and fluoride
ions.
11. The process of claim 5 in which the pH is maintained
at less than about 2.5.
12. The process of claim 1 or claim 2 in which the
organic to aqueous ratio of the mixture of step (a) is
between about 3.0 and about 4.0.
13. The process of claim 1 in which the pH of the
strip solution of step (c) is maintained at less than about
1.
14. The process of claim 1 in which the extraction is
carried out continuously in more than one extraction
vessel, with a counter-current flow of aqueous and
organic phases, fresh aqueous feed being introduced to
the first vessel and cycled successively through each
vessel to the last vessel, while fresh extraction agent is
introduced into the last vessel and cycled successively
backward through each vessel to the first vessel, loaded
extractant being withdrawn from the first vessel for
stripping, and barren aqueous solution being withdrawn
from the last vessel.
15. The process of claim 14 in which the number of
extraction stages is 3..
16. A process for substantially separating manganese
ions from potassium and, if present other impurities
selected from the group consisting of magnesium, chIo4,423,012
12
22. A process for substantially separating zinc ions
from magnesium and, if present, other impurities selected
from the group consisting of manganese, calcium,
chloride, and fluoride ions in an aqueous zinc
solution containing such impurities; which comprises:
a. mixing the solution with a solvent extraction agent
comprising diethylhexylphosphoric acid as an organic
extraction agent and an organic solvent
therefor to form a mixture having a pH of about 1
to about 5 and an organic to aqueous ratio of from
about 0.5 to about 4 to selectively extract zinc ions;
b. adjusting the pH of the mixture of step (a) with a
pH-adjusting reagent so as to maintain the pH of
.the mixture below about 2.5;
15 c. separating the aqueous and organic portions of the
mixture of step (b);
d. stripping the loaded organic extractant of step (c)
with an aqueous acidic solution to remove zinc
, therefrom.
23. The process of claim 22 in which the aqueous zinc
solution is a bleed from a zinc electrowiIining circuit,
and the strip solution of step (d) is spent electrowinning
solution; and the loaded strip solution resulting from
step (d) is recycled to the electrowinning process.
24. The process of claim 21 or claim 22 in which the
solvent extraction agent comprises a mixture of
. DEHPA and an organic diluent therefor, and the organic
to aqueous ratio of the mixture is between about
3.0 and 4.0.
25. The process of claim 22 or claim 23 in which the
stripped organic extractant is regenerated with a reagent
selected from the group consisting of calcium
oxide and magnesium oxide.
26. The process of claim 22 or claim 23 in which the
pH of the strip solution of step (d) is maintained at less
than about 1.
27. The process of claim 22 or claim 23 in which the
extraction is carried out in three counter-current stages.
* * * * *
11
ride and sodium ions, in an aqueous manganese solution
containing such impurities, which comprises:
a. mixing the solution with a solvent extraction agent
comprising diethylhexylphophoric acid as an organic
extraction agent and an organic solvent 5
therefor to form a mixture having a pH from about
I to about 5 and an organic to aqueous ratio of from
about 0.5 to about 4 to selectively extract manganese
ions; 10
b. adjusting the pH of the mixture of step (a) with II
pH-adjusting reagent so as to maintain the pH of
the mixture between about 2.5 and about 4.3;
c. separating the aqueous and organic portions of the
mixture of step (b);
d. stripping the loaded organic extractant of step (c)
with an aqueous acidic solution to remove managanese
therefrom.
17. The process of claim 16 in which the aqueous
manganese solution is a bleed from an electrowinning 20
circuit for manganese dioxide, and the strip solution of
step (d) is spent electrowinning solution; and the loaded
strip solution resulting from step (d) is recycled to the
electrowinning process.
18. The process of claim 16 or claim 17 in which the 25
solvent extraction agent comprises a mixture of
DEHPA and an organic diluent therefor, and the organic
to aqueous ratio of the mixture of step (a) is between
about 3.0 and 4.0. 30
19. The process of claim 16 or claim 17 in which th~
stripped organic extractant is regenerated with a reagent
•selected from the group consisting of calcium
oxide and magnesium oxide.
20. The process of claim 16 or claim 17 in which the 35
pH of the strip solution of step (d) is maintained at less
than about 1. .
21. The process of claim 16 or claim 17 in which the
extraction is carried out in three counter-current stages.
40
45
50
55
60
65