4,423,012 Manganese and zinc solvent extraction process

Patent Number/Link:

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

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

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.

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

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.

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.

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

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

Stage No.

Aqueous

Zn (gil)

Example 4

TABLE 3-continued

1 2

0.085 1.41 41.5

80.0

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

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.

127

133

43.6

41.3

53.6

54.0

3.07

2.97

Aqueous Feed (gil)

MgCa C1 K

14.4 .599 .059 .009

3.1 .733 .134 .645

15.4 .586 .072 .244

8.34 .505 0.15

5.47 .880 .112

TABLE 5b

.068

.620

.003

<.001

Escaid

DEHPA 200

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

TABLE 5b-continued

4,423,012

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

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

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.

* * * * *

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.