5,358,700 Method of extracting zinc from brines

Patent Number/Link:

111111111111111111111111111111111111111111111111111111111111111111111111111

United States Patent [19]

Brown et ale

[11]

[45]

USOO5358700A

Patent Number:

Date of Patent:

5,358,700

Oct. 25, 1994

[54] METHOD OF EXTRACTING ZINC FROM

BRINES

[75] Inventors: Patrick M. Brown, Exton, Pa.; Jerry

Dobson, Tucson, Ariz.; Enzo L.

Coltrinari, Golden, Colo.; Eugenio

Iasillo, Tucson, Ariz.

[73] Assignee: Cyprus Power Company, Englewood,

Colo.

[57] ABSTRACT

The present invention provides a novel method of extracting

zinc from geothermal brines and synthetic

brines which can be performed in a continuous, in-line

process.

E. D. Nogueira et ai, Chloride Electrometall. Proc.

Symp., pp. 59-76 (1982).

E. D. Nogueira et ai, Chemistry and Industry, 2:63-67

(1980).

R. W. Bartlett et ai, Transactions, 3:39-42 (1979).

A. Maimoni, Geothermics, 11(4):239-258 (1982).

F. L. Moor et al, Plat. Surf. Finish., (Aug. 1976).

C. MacDonald, "Solvent Extraction Studies Using

High Molecular Weight Amines Progress Report",

Texas Southern University, Houston (Jul. 1975).

C. MacDonald, "Removal of Toxic Metals from Metal

Finishing Waste Water by Solvent Extraction" Texas

Southern University, Houston U7816 (Feb. 1978).

L. Schultze and D. Bauer, "Recovering Zinc-Lead

Sulfide from a Geothermal Brine," Rep. Invest., U.S.

Dept. Interior, Bureau Mines, RI 8922, 14 pp. (1985).

E. P. Farley et al, Gov. Rep. Announce. Index (U.S.),

81 (23):4897 (1981).

C. E. Berthold et ai, Gov. Rep. Announce. Index (U.S.),

75(16):64 (1975).

Primary Examiner-Melvyn J. Andrews

Attorney, Agent, or Firm-Howson and Howson

15 Claims, 2 Drawing Sheets

Appl. No.: 957,502

Filed: Oct. 5, 1992

Int. Cl.5 C22B 3/26

U.S. Cl 423/100; 423/DIG. 19

Field of Search 423/100, DIG. 19;

75/712

[56]

[21]

[22]

[51]

[52]

[58]

References Cited

U.S. PATENT DOCUMENTS

3,923,976 1211976 Vega et al. 423/99

4,602,820 7/1986 Hard.

4,624,704 11/1986 Byeseda 423/DIG. 19

4,710,367 12/1987 Wong et aI 423/DIG. 19

OTHER PUBLICATIONS

E. D. Nogueira et al, Complex Sulphide Ores, Pap.

Conf., pp. 227-233 (1980).

E. D. Nogueira et ai, Engineering and Mining Journal,

180(10):92-94 (1979).

GEOTHERMAL

BRINE

pH2

CaCIZ, NoCI CaCI2 WATER

SOLUTION NH3 CaCI2

HCI TO pH 3.0 SOLUTION SOLUTION

r- 10RGANI~ •

I I

L Zn EXTRACTION Fe,Mn SCRUB Zn STRIP NH3 WASH 1-_ J

- (STEP I) - • (STEP 2) - .. (STEP 3) - - .. (STEP 4)

RAFFINATE

SCRUB

SOLUTION

1-1

REINJECTION

STRIP

SOLUTION

ZINC

CONCENTRATE

WASH

SOLUTION

GEOTHERMAL

BRINE

pH2

CoCI2, NoCI CoCI2 WATER

SOLUTION NH3 CoCI2

HCI TO pH 3.0 I SOLUTION SOLUTION

~ lORGANI~ •

I I

t.. Zn EXTRACTION _ Fe,Mn SCRUB _ Zn STRIP _ NH3 WASH _ J

(STEP I) (STEP 2) (STEP 3) (STEP 4)

•

00 •

Io'd a('D a

til

Io-ol

1.0

,J:>.

SCRUB

RAFFINATE SOLUTION

I I

REINJECTION.

STRIP WASH 00 SOLUTION SOLUTION n=>-

.n.>...

Io-ol

0......

I I

ZINC

CONCENTRATE

FIG. I ..U. 1

..Q. C

"" 00

HCI ACIDIFY

FIG. 2

I RECYCLED ORGANIC .-----------FROM OTHER SX

STAGES

1st STAGE I -/ I

_ CONCENTRATED

BRINE I SETTLER ORGANIC TO

-, EXTRACTION SCRUB STAGE

AQUEOUS BRINE

~ORGANIC PHASE

2nd ·STAGE

EXTRACTION I -I SETTLER

AQUEOUS WASTE

L: •

•

~ie-l'-

~(Jl

Ioool

00 =(

-.U. I

-.Q. C

-:I oo

5,358,700

METHOD OF EXTRACITNG ZINC FROM BRINES

FIELD OF THE INVENTION

This invention relates generally to the field of metal 5

extraction, and more specifically to methods of extracting

metals from brines.

BACKGROUND OF THE INVENTION

Over the past twenty years, many attempts have been 10

made and described in both patent and scientific literature

to successfully extract zinc in an efficient and costeffective

manner from geothermal brines, which contain

various mixtures of metals and minerals. Among

prior art methods was a process first performed approx- 15

imately twenty years ago involving the addition of lime

to precipitate metals from the brine and subsequently

separating the metals. Selective sulfide precipitation

was also attempted [R. W. Bartlett et al, "Sulfide Precipitation

of Heavy Metals from High Salinity Geother- 20

mal Brine," Geothermal Resource Council, Transactions,

3:39-42 (1979)]. A variety of more sophisticated processes

were developed, e.g., electrowinning, which

involves the water stripping of a R2NH2+<+ extractant

followed by reextraction using di-2-ethylhexyl-phos- 25

phoric acid (D-2-EHPA) with a catholyte strip, resulting

in the formation ofzinc sulfate [E. D. Nogueira et al,

Engineering and Mining Journal, 180(10):92-94 (1979) ].

As one example of reportedly unsuccessful prior art,

Byeseda, U. S. Pat. No. 4,624,704 refers to a method for 30

selectively recovering zinc from metal-containing

brines, which employs the steps of contacting brine

with an organic agent to form a zinc amine, and transferring

a large amount of the zinc to the organic phase,

where it is then contacted with an aqueous strippant 35

solution. While the patent reports that the zinc and zinc

amine complex are transferred to an aqueous zinc chloride

solution, from which zinc may be recovered by

electrowinning, the present inventors have tried this

method and found it produces only very low concentra- 40

tions of zinc in the aqueous phase and long contact and

settling times of 5 and 15 minutes, respectively. The

concentration and time restraints limit the volume of

brines which can be handled by the conventional extracting

equipment and thus, the amount of zinc which 45

can be produced. The low zinc concentration and Claccumulation

in the strippant which precludes heavy

recycle renders a technically-feasible process incapable

of practical use. This method is not only not used anywhere

in the world to remove zinc from brine, but the 50

assignee of the patent has completely withdrawn from

the applicable business.

Another zinc extraction process was disclosed in A.

Maimoni, Geothermics, 11(4):239-258 (1982) involving a

cementation process using iron as a reducing agent for 55

cementation. In the practice of this process, a silica

sludge accumulates in the equipment and requires periodic

removal. It should further be noted that this process

was never commercially developed.

Other prior art methods for removing zinc from 60

brines includes, among others, U. S. Pat. No. 3,923,976;

E. D. Nogueira et aI, Complex Sulphide Ores, Pap. Con!,

p. 227-233 (1980); E. D. Nogueria et al, Chemistry and

Industry, Z:63-67 (1980); F. L. Moor et al, Plat. Surf

Finish., (August 1976); C. MacDonald, "Solvent Ex- 65

traction Studies Using High Molecular Weight Amines

Progress Report", Texas Southern University, Houston

(July 1975); and C. MacDonald, "Removal of Toxic

Metals from Metal Finishing Waste Water By Solvent

Extraction", Texas Southern University, Houston

U7816 (February 1978). Prior to the present invention,

a vast resource of this mineral has been untapped because

none of the above-referenced publications are

capable of providing a successful process for extracting

zinc from brines, which process is able to overcome

both scientific and economic obstacles [see, e.g., E. D.

Nogueira et aI, "Design Features and Operating Experience

of The Quimigal Zincex Plant," Chloride Electrometall.,

Proc. Symp., 59-76 (1982)].

There thus remains a need in the art for a method for

extracting zinc from geothermal brines which is both

technically and practically feasible, and which permits

zinc to be extracted efficiently and quickly from available

sources.

SUMMARY OF THE INVENTION

The present invention provides an improved economically

advantageous method of recovering metals, particularly

zinc, from brines. Under the inventors' designed

operating conditions, this process is kinetically

much quicker than the processes known in the art, and

produces a concentrated aqueous zinc strip liquor and

thus can be performed continuously and in an in-line

system, rather than by batch, because of the high final

zinc concentration and decreased contact time needed

between the organic extractant and the· brine.

In one aspect, the present invention provides a process

which permits the extraction of Zn from a natural

or synthetic brine which contains salts ofsodium, potassium

and calcium chlorides, as well as a number ofother

elements including manganese, iron, lead, silver, magnesium,

strontium and lithium. The ability to rapidly and

selectively extract zinc in the presence of many metals

so that greater than 90% recovery is obtained is a significant

advantage of the method of the invention.

This process comprises several steps, such as, providing

Zn in an organic extractant at a concentration of

between about 1 to 4 gIL. This step requires that substantially

all Fe and Mn be removed from the organic,

and then the Zn stripped therefrom using an ammoniacal

salt solution to generate a 10 to 50 gIL Zn concentrate.

In one embodiment, after substantially all silica is

removed, the brine is then run through a circuit or cycle

which is made up of the following steps, some of which

may be performed more than once during a single cycle:

(1) contacting the brine with a selected organic, e.g.,

a quaternary amine, to extract Zn therefrom; and

thereafter separating the loaded organic from the

aqueous brine raffmate;

(2) scrubbing the loaded organic with a dilute brine

solution or acidified brine, which removes the coextracted

Fe and Mn from the loaded organic; and

(3) stripping the Zn from the scrubbed organic with

an ammoniacal CaCh solution to produce a concentrated

and purified Zn strip solution with a Zn

concentration of at least 10 giL.

Application of conventional techniques to the concentrated

Zn strip solution may result in recovery of the

zinc.

In yet another embodiment, the process of the invention

is also used to extract Zn from synthetic brines

which may contain either Fe or Mn, such as certain

waste stream brines. In this embodiment, the extraction

5,358,700

process described herein is modified by removing the

scrubbing step when Fe and Mn are not present.

Other aspects and advantages of the present invention

are described further in the following detailed description

of the preferred embodiments thereof.

BRIEF DESCRIPTION OF THE INVENTION

brine was tapped. Without its removal, the costly wells

are quickly plugged.

Generally an economically desirable amount of

pooled, silica-free brine is employed in the following Zn

5 removal steps. This amount of brine will vary with the

Zn concentration in the brine, but may be on the order

of about 5000 to about 20,000 gpm.

B. Continuous Zinc Recovery from Brines

Most preferably as described above, the starting material

for the zinc extraction cycle is pooled flashed

brine which is substantially free of colloidal silica at a

temperature of about 70° C.-110° C. and a pressure of

about 1 atm.

The continuous method of the present invention for

zinc recovery from brines is referred to herein as the

solvent extractions (SX) circuit. It consists of a circuit

or cycle made up of some or all of the following steps.

In practice, the circuit design utilizes a 2-stage countercurrent

extraction, 2-stage counter-current scrub, and

single strip and wash stages. When metal ions which are

prone to oxidation and precipitation are used a closed

system from which 02 is excluded is preferred.

DETAILED DESCRIPTION OF THE

INVENTION

FIG. 1 is a block diagram illustrating a Zinc Solvent

Extractions Circuit.

FIG. 2 is a block diagram illustrating an optional two 10

stage counter current Zinc Extraction step useful in step

1 of the overall Circuit of FIG. 1.

The present invention provides an improved method

of extracting zinc (Zn) selectively from a geothermal or

synthetic brine which may contain other metal ions

including, without limitation, manganese, iron, lead,

silver, magnesium, manganese, strontium, calcium, so- 20

dium, potassium and lithium. The continuous flow process

of this invention enables the zinc to be ultimately

recovered via conventional electrowinning techniques.

When applied to a natural brine, this process can result

in approximately 90% Zn recovery in the strip solution. 25 Step One: Zinc Extraction with Amine

Ordinarily, a geothermal brine, e.g., from the Salton

A. Preparation of the Geothermal Brine Sea area enters Step 1 of the zinc extraction cycle con-

High temperature, naturally occurring geothermal taining approximately 200 to 800 ppm Zn, and preferabrine,

of which many sources exist in the world, nor- bly 250-800 ppm Zn.

mally contain significant quantities of silica when they 30 The first step of the process involves contacting the

are recovered from the earth. As the brines rise to the aqueous brine with an organic to extract zinc therefrom.

surface and the pressure decreases, carbon dioxide and Preferably the ratio of aqueous brine to organic (AIO

hydrogen sulfide are dispelled from the brine. This in ratio) for this step ranges from about 2:1 to about 6:1.

turn reduces the acidity of these brines. Various geo- More desirably, the AIO ratio is from 3.0:1 to 4.5:1, and

thermal brines are characterized by different tempera- 35 is preferably about 4: 1.

ture, pressure and mineral content conditions. In one The preferred organic used for Zn extraction is a

example of a brine which was subjected to the methods mixture of an extractant, a modifier and a diluent. The

of this invention, a geothermal brine capable of produc- organic extractant used must be stable; resistant to deging

steam at ground level is characterized by the follow- radation upon prolonged exposure to hot concentrated

ing conditions: it is between about 230°-260° C. at a 40 brine and strip liquor, and virtually water insoluble in

pressure of between 450-700 pounds per square inch both the hot brine and strip liquors. The preferred ex-

(psi). tractant is a quaternary amine; however, other suitable

In addition, steam can be withdrawn from the brines zinc extractants include solvating extractants, which are

for the purpose of energy generation resulting in sub- useful at 2-3 Molar brines, such as tributyl phosphate

stantial reductions in temperature from 230° C. to about 45 (TBP, with aliphatic diluent), di-2-ethylhexylphos-

70°_110° C. by flashing of the steam in one or more phoric acid [D-2-EHPA or DEHP(H)], which is good

steps or heat exchange with pure water. This process of at low molarity chlorides, versatic and napthenic acid.

removal of acid gases and cooling of the brine during Quaternary amine extractants are advantageous over

removal from the geothermal wells causes silica present prior art extractants because they are resistant to oxidain

the brine to precipitate. 50 tion and very stable at high temperatures and are selec-

Where the brine to be subjected to the process of this tive for Zn. In addition, they allow rapid kinetics of the

invention is geothermal, the first step of the process of exchange reaction at high temperatures. In a preferred

this invention involves removing the insoluble amor- embodiment, the quaternary amine contains at least

phous silica precipitate from the brine. The silica solids three long-chain alkyl groups, each having a carbon

which have precipitated in the brines as a result of cool- 55 chain length of between 6 to 12 carbon atoms. One

ing and loss of acid gases are desirably removed from example is Aliquat 336, containing a Cg alkyl group

the brines prior to the solvent extraction process. Their [H3C(CH2)SCHCH3], a tricapryl methyl ammonium

removal can be achieved through careful and efficient chloride reagent supplied by Henkel Corp. Note that

liquid-solid separation techniques. this quaternary amine has three capryl alkyl chains and

The resulting pooled brine, which is now substan- 60 one methyl group on the amine. Aliquat 336 is a strong

tially free of colloidal silica, is used as the starting mate- extractant for Zn and ferric iron from brine solutions

rial for the zinc removal process. The term "substan- and has a lesser affmity for extraction ferrous iron and

tially free of colloidal silica" is defined as containing manganese. The long chain alkyl groups are necessary

residual amounts of silica of less than 10 ppm. More to render the quaternary amine soluble in the organic

preferably, the silica content remaining in the pooled 65 phase and insoluble in the aqueous phase. Quaternary

brine is in the range of between about 1 to about 10 ppm amines with 1 or 2 long chain alkyl groups may also be

Si02. The brine, removed of silica, can optionally be useful. Other desirable quaternary amines include other

reintroduced into the well from which the geothermal similar low cost, naturally derived products.

5,358,700

In the organic, the amine extractant is preferably

mixed with a modifier in a diluent. A selected modifier

is preferably a long-chain alkyl (6 C to 20 C) alcohol,

such as Exxal 10, an isodecyl alcohol supplied by

Exxon. The modifier increases the solubility of the Zn- 5

amine complex in the diluent. A diluent is preferably a

low-vapor pressure, low-viscosity mineral oil, in which

the amine and modifier are soluble and which is stable at

the elevated temperatures of the geothermal brine. As

used in connection with the characterization of the 10

diluent herein, 'low' means being sufficiently low to

prevent significant losses through vaporization while

operating at temperatures ofbetween about 70°-120' C.

The diluent may also be mixed with the amine extractant.

Diluents may be selected from high boiling, long 15

carbon chain paraffinic hydrocarbons. A preferred diluent

is Norpar 15 [Exxon].

Currently, the most preferred organic composition is

10 vol % Aliquat 336 plus 10 vol % Exxal 10 diluted in

Norpar 15. One of skill in the art may select another 20

appropriate alternative organic which has the requisite

properties, depending upon the characteristics of the

brine, operating conditions and value of recovered

product.

Zinc (Zn+2) in the brine exists as an anionic Zn chlo- 25

ride complex (ZnC4-2). When the aqueous brine is

mixed with the organic in this step (see FIGS. 1 and 2),

the anionic zinc chloride complex is strongly extracted

from the brine aqueous phase into the organic phase by

the quaternary amine. This reaction is represented by 30

the following formula: .

wherein

R represents alkyl groups and (R4N)Cl is the chloride 35

salt of the quaternary amine.

Besides Zn, the amine also extracts Fe+3 strongly and

Fe+2, Mn, and Pb less strongly from brine solutions

into the organic phase. This is particularly true if any

oxidation has occurred and the iron and manganese are 40

in higher oxidation states, as the ferrous or manganous

ions are not strongly complexed or extracted. Optionally,

when the process is performed and the potential

for oxygen intrusion occurs, Fe powder, wool, or S02

may be added to the brine in order to cause reduction of 45

ferric iron to ferrous iron and decrease co-extraction

with Zn. Typically, when iron or manganese are coextracted,

they precipitate during the subsequent ammonia

stripping process, if not removed.

After this Zn extraction step, the organic (now 50

loaded with the Zn) is separated from the aqueous brine

raffmate. The raffmate may be reinjected into the original

geothermal well from which it was obtained. The

loaded organic may proceed in the SX circuit onto Step

Two below, or it may be optionally recycled through 55

the extraction step at least one more time (see FIG. 2).

FIG. 2 illustrates an optional 2-stage counter current

Zn extraction step in which brine initially enters the

First stage Zn extraction where it is contacted with the

organic. The aqueous and organic phases are separated 60

in the first settler, from which the organic phase, concentrated

with Zn, goes onto the scrub step 2 and the

aqueous brine containing minor amounts of Zn enters

the second stage extraction. In the second stage extractor,

this aqueous phase is contacted with organic recy- 65

eled from later SX steps and containing substantially no

Zn. The organic is recycled after stripping and washing

to remove most of the ammonia. The organic, low in

ammonia, may be acidified before Zn extraction. The

chloride form ofthe amine is the most effective form for

extraction. If its pH were high, the organic would cause

some of the amphoteric elements, e.g., Fe and Mn, to

precipitate. Thus, immediately prior to recycling for

additional Zn extraction, this stripped organic may be

acidified, e.g., by a water and then acid wash to a pH of

about 3, to convert the amine back to its chloride form.

This recycled organic strongly strips the remaining Zn

from the brine. The brine then is sent as aqueous waste

back for reinjection into the well. The organic phase,

containing the small amount of extracted Zn is then

used as the organic in the first stage extraction. This

process may be recycled as often as desired.

When the Zn extraction of Step One is complete a

desired number of times, the loaded organic, separated

from the raffinate proceeds to Step Three of the process.

The kinetic advantage of this extraction step contributes

significantly to the overall process and permits

extraction of as low as about 0.2 g Zn per liter of brine.

Generally, the time during which the brine is contacted

with the organic extractant preferably ranges from

about 5 to about 25 seconds. As one example of the

performance of this step, Zn recoveries have ranged

from between 60-87% in IS-second contact time at

90°_95° C. using impeller mixing in a single step process.

With in-line mixing and a 9 second contact time,

68% Zn extraction has been obtained. Tests on actual

brines has shown greater than 90% extraction in 15

seconds or less with a two stage counter current extraction.

The advantages to the process created by these

rapid kinetics was not previously recognized by the art.

Step Two: Coextracting Fe and Mn

When oxidation and extraction of Fe and Mn occurs

in Step One, it may be necessary to wash or "scrub" the

organic phase loaded with Zn and co-extracted iron and

manganese with a dilute acidified brine solution in order

to remove the co-extracted Fe and Mn from the Znloaded

organic phase. The dilute brine solution may

contain a sufficient salt concentration to prevent an

emulsion from forming. Preferably this step occurs at a

pH of about 2-4.

The impurities are scrubbed from the Zn-Ioaded organic

with the dilute brine solution. At low CI concentrations,

the impurities chloride complexes are stripped

from the organic, whereas the Zn complex is not. S02

may be injected in the scrub stage to reduce any Fe+3

extracted to Fe+2 which is more easily scrubbed from

the organic.

A preferred scrub solution is made up of about 6 grn

per liter NaCl and 2 grn per liter CaCh, adjusted to a pH

of about 2 with a suitable acid, such as 0.27N HCI. For

example, for a 50 liter dilute brine solution, the components

are 50 liters water, 300 g NaCI, and 132 g CaCh

flake (CaCh·2H20) which is then pH adjusted.

Thereafter the organic phase can be washed with an

acidified salt solution or, e.g., HCl and water, until it

achieves a desired iron and manganese level. One of

skill in the art may prepare washing solutions with acids

and salts in various proportions with water without

resort to undue experimentation.

Following this step, a preferred level of each of Fe

and Mn is reached in the organic phase, e.g., about 20

ppm or less. The scrub solution may also be reinjected

5,358,700

back into the well or recycled back into the circuit at an

appropriate place.

Step Three.: Stripping Zn from Organic

According to another step of the process of this in- 5

vention, the Zn is stripped from the scrubbed organic

with an ammoniacal salt solution to produce a concentrated

and purified Zn strip solution. Stripping is accomplished

by adding a suitable strip solution to the

above-described extracted and scrubbed organic phase. 10

Zinc is stripped from the organic phaSe by contacting it

with an ammoniacal salt solution to ultimately form the

cationic Zn tetraamine complex Zn(NH3)4+z.

The strip solution is desirably made up of ammonia

and a selected salt. While CaCh is the presently pre- 15

ferred salt, any other alkali 'or alkaline earth chloride

which does not form a precipitate in the system may be

substituted for CaCh, for example, NaCI, NH4CI or

KCl. The presence of a salt in the strip solution increases

the solubility of the Zn(NH3)4z+ complex in the 20

strip solution and breaks up any emulsions which might

otherwise form.

Preferably the amount of ammonia used in the strip

solution is between about 1.5N to about 3N NH3 (or

NH40H) with 3N NH3 being presently preferred. The 25

high ammonia content ofthe strip solution permits good

stripping because of the following complex formations:

handle large volumes of brine, e.g. 20,000 gallons per

minute, by concentrating the zinc to volumes which

conventional equipment can handle. Advantageously,

the method can produce a concentration in the range of

between 10-50 giL of Zn. In contrast, prior methods

using water or salt stripping produced only 2-4 giL.

Thus, this method provides a method of recovering zinc

without the need for making substantial hard rock mining

a part of the zinc recovery process.

The zinc recovery method according to this invention

employs steps for recovering zinc from other natural

or synthetic brines, such as those recovered from

waste streams. For example, blast furnace dusts contain

significant quantities of zinc, from which zinc could be

recovered after dissolution. Adaptation of the process

of the present invention for removing zinc from synthetic

brines offers similar advantages over the processes

known to the art. However, because synthetic

brines tend not to contain metals, such as lead, iron and

manganese, fewer scrubbing steps are required. In some

cases, no scrubbing will be required at all. Therefore,

this second method is performed utilizing the steps

described above, but may omit the scrubbing Step 2

from this process.

The following examples illustrate the preferred methods

of the invention. These examples are illustrative

only and do not limit the scope of the invention.

Currently, the preferred strip solution is made up of

55 gIL NH3 and 50 gIL CaCho For a 20 liter solution,

the components are 15.7 liters water, 1.32 kg calcium 35

chloride flake (CaCh·2HzO), and 3.9 kg ammonium

hydroxide (26 degree Baume). The reaction and stripping

is preferably performed in less than one minute.

The result of the above step is a pregnant or Zn-containing

strip solution (aqueous phase) "loaded" withZn, 40

containing approximately 10-50 gIL Zn, according to

performance of the process in the laboratory. This pregnant

strip solution is removed by separation from the

organic phase. The concentrated strip solution may

then be treated by conventional techniques to permit 45

recovery of the zinc therefrom.

Step Four: NH3 Wash

An optional step of the SX circuit involves the use of

the stripped organic layer resulting from the previous 50

Step 3. The stripped organic layer may be washed or

reacted once more with a neutral CaCh or NH4CI solution

to remove NH3 from the organic layer. A preferred

wash solution contains 50 giL CaCho For a 20 liter

solution, 20 liters of water is mixed with 1.32 kg calcium 55

chloride flake.

The resulting CaCh or NH4CI solution (aqueous

phase) which contains NH3 is then recycled back to the

Zn strip step (Step 3) for reuse. The free NH3 recovered

is treated with more NH3IHZO and also recycled to the 60

strip step in the circuit. The organic layer is then optionally

acidified with HCl to a pH ofabout 3 to convert the

quaternary amine to the neutral, chloride, form, maximizing

the effectiveness of the quaternary amine extractability.

This washed organic layer is also recycled 65

back to Step 1, the Zn extraction for reuse in the circuit.

This Zn recovered in the strip solution demonstrates

that this method can permit conventional equipment to

(R.4N)2ZnC4+4Nl40H->Zn(NH3).:jC12+Z(R4N)Cl+

4H20

EXAMPLE 1

Zinc SX Circuit

This example describes a prototype solvent extraction

circuit of the present invention. This SX circuit is

graphically depicted in FIGS. 1 and 2. The circuit design

utilized 2-stage counter-current extraction (FIG.

2), 2-stage counter-current scrub, and single strip and

wash stages. Each stage employed a double-walled

glass mixer and settler. The mixers and settlers were

capped and nitrogen sparged. Recycle from each settler

to mixer was controlled by a pinch off valve and monitored

by a rotameter. Individual stages were connected

by glass tubing.

The outer chamber of each mixer and settler was used

as a control jacket. Steam was applied to every vessel

except the strip mixer. The strip mixer jacket was piped

with water required for cooling.

The entire apparatus was mounted on a vertically

positioned fiberglass grate inside a 30 ft by 8 ft trailer. A

solution containment tray was placed beneath the entire

apparatus for safety. The brine line was insulated! inch

stainless steel pipe and the flow rate was regulated by

adjusting a needle valve. Plant water was used to flush

the line after each test series.

Reagents for the scrub, strip and wash stages were

mixed in 20 or 50 liter plastic containers and administered

by diaphragm metering pumps. The organic feed

was pumped by gear pump from a metal insulated surge

tank.

With reference to FIGS. 1 and 2, the cycle operates

as follows. A side stream of brine was fed into the first

extraction mixer (Zn EXTRACTION) where it contacted

the immiscible organic phase. The emulsion advanced

from the mixer to a settler where the phases

were separated. The loaded organic phase containing

the extracted zinc was then transferred to a scrub section

(Fe, Mn SCRUB). The brine continued to the second

extraction mixer where it was contacted with the

recycled organic. The emulsion then advanced from the

.002

<.03

<.05

<.01

<.05

<.01

<.05

<.001

<.002

Ni <.005

.07

.03

.02

.01

.007

.005

.004

.003

TABLE I-continued

3. XRF semi-quantitative assay of

crystallized salts present in bottom of drum.

% %

Analysis of Geothermal Brine Sample HRI 44786

Zn SX Data Summary

Extraction Scrub Strip Acid'n

No. stages 2 1

F1owrate, mllmin

Organic 110-130 110-130 110-130 110-130

Feed aqueous 400-450 12-15 7-9 0.3-0.5

Mixer 0/A ratio 0.26 2 2 2

Contact time, min 0.15-.3 1 3 1

Temperature, ·C. 90-95 75-85 60-80 70-80

5,358,700

EXAMPLE 2

Analysis of Geothermal Brine Sample HRI 44786

mixer to a settler where the phases were separated. The

raffmate solution was discharged into a raffinate holding

tank (RAFFINATE).

The loaded organic from the first extraction stage

advanced to the first scrub mixer where it was first 5

contacted with the scrub solution (sodium chloride and

calcium chloride solution at a neutral pH). The scrub

solution strips the undesired metals from the organic.

The emulsion then moved from the mixer to a settler

where the phases were separated. The organic phase 10

was sent to the second scrub mixer where the fmal

cleansing of the organic occurs. The second scrub stage

emulsion then moved from the mixer to a settler where

the phases were again separated and the organic was

advanced to the strip stage. 15

The scrubbed organic was advanced from the second

scrub settler to the mixer where it was contacted with a

solution of 55 giL ammonia and 50 giL CaCh (Zn

STRIP). The ammonia solution stripped the zinc from

the organic phase into the aqueous phase. The emulsion 20

then advanced to a strip settler where the phases were

disengaged. The organic moved on to the wash stage

(NH3 WASH), while the zinc laden strip solution was

discharged from the circuit into a storage tank (Strip 25 A. First Test Series

Solutionlzinc concentrate). The conditions for these tests were as follows: The

The barren organic from the strip stage advanced to brine feed contained 0.71 gIL Zn, 2.7 gIL Fe, 2.1 giL

the wash mixer where it was contacted with the wash Mn; pH 2.5-3. The organic contained 10 vol % Aliquat

solution (55 gpl calcium chloride).'The wash solution 336+ 10 vol % Exxal 10 in Norpar 15. The scrub soluremoved

any entrained ammonia from the organic 30 tion contained 5 gIL NaCl+3 gIL CaCh, pH 2 (HCl).

phase. The emulsion then moved from the mixer to a The strip solution contained 54 gIL NH3 + 50 gIL

separater. The stripped organic phase advanced to the CaCho Acidification was performed using 3N HCl feed

surge tank for recycle to zinc extraction. Prior to ex- solution, and 100 gIL NaCl!NH4Cl solution recycle

traction of Zn, the recycled organic was treated with solution. The other conditions for the first set of four

acid to lower its pH to 3.0. 35 continuous SX runs and the assay results are summarized

in Tables 2 through 4 below.

TABLE 2

________T_AB_L_E 1________ 45

Continuous SX Panel Runs

An SX panel, consisting of one extraction, two

scrubs, one strip, and one acidification stage, was assem- 40

bled for the continuous Zn SX runs using Aliquat 336

and actual geothermal brine. The analysis ofthe brine is

shown in Table 1.

HRI-44786 2.5 1.244 .719 2.82 2.00 .136

Sample No. pH Sp. gr Zn Fe Mn Pb

Sample Description Some salt crystals and minor amount of

tan-colored precipitate present in bottom

of drums.

1. Quantitative assays

Assay, gIL

TABLE 3

Run No. 5 6 7b 8

N2 blanket extract'n extract'n extract'n extract'n

only only acid'n acid'n

CI S02add'n scrub 1 + 2 scrub 1 scrub I scrub 1

218 and acid'n only only only

30 cc/min 30 cc/min 10 cc/min 10 cc/min

55 Extract'n impeller impeller impeller in-cline

mixer

Mix contact 16 sec 15 sec 15 sec 9 sec

time

60 TABLE 4

Zn SX Assay Data Summary

Run 5 6

Assay, gIL pH Zn Fe pH Zn Fe

Extraction,

Organic 1.88 .53 1.96 .54

Rafi"mate 2.5 .14 2.7 .23

% extracted 86.7 67.6

Scrub 1,

gIL

.02

.01

<.1

<.005

<.1

<.2

<.04

<.05

<.005

214

2.4

2.1

.09

.04

.03

2. XRF semi-guantitative assays

gIL

100

3.0

1.2

0.9

0.7

0.4

0.2

0.02

0.080 pCi

0.810 pCi

O.064pCi

0.064 pCi

Trace Elements (PPM)

Major Elements (percent)

The effect of in-line mixing time on Zn extraction, a

comparison of Zn extraction in one stage versus two

countercurrent stages, and the effect of organic Zn

loading on Zn extraction were screened in these runs.

The SX circuit was the same as used in previous runs

except that the impeller-stirred mixer in the extraction

stage was replaced by an in-line mixer. For the one

stage extraction tests, the in-line mixer consisted of four

1.5 -cm diameterX 122 cm glass tubes filled with fiveor

six-millimeter glass beads and connected in series.

For the two countercurrent stage tests, two of the tubes

were used per stage with a settler between the first and

second stage.

The conditions of this test were as follows. The brine

feed assayed in gIL: 0.53 Zn, 1.25 Fe, and 1.34 Mn at a

pH 3-3.5. The organic contained 10 vol % Aliquat

336+ 10 vol % Exxal 10 in Norpar 15, recycled from

previous runs. The scrub solutions were: I) 5 giL

NaCL +3 gIL CaCh, acidified to pH 2 with HCl and

2) raffinate diluted 1/40 with H20 and acidified to pH 2

with HCI. The strip solution was 55 gIL NH3+50 gIL

CaCI2. The stripped organic wash solutions were I) 3N

HCl feed solution, 100 gIL NaCl/NH4Cl recycle solution,

and 2) 50 giL CaCho

Other conditions are summarized in Table 6 below.

TABLE 5

Geothermal Brine composition

Average concentrations for production brines, injection

brines may be 10-20 percent higher, balance is water.

sq ftfgpm 0 +A in the scrub, strip, and acidification

stages.

In the last run (Run 8), no significant scum was

formed in the extraction, scrub, and acidification stages.

5 Some minor amount of precipitation (probably CaS03)

occurred in stripping.

B. Second Test Series

Five Zn SX runs using in-line mixing in extraction

10 were performed. A second geothermal brine sample

was used in these tests and assayed (in gil) 0.53 Zn, 1.25

Fe, 1.34 Mn, 0.12 Pb, 0.0010 Ag, and pH 3 to 3.5. Other

information on the content of the brine is provided in

Table 5.

Chloride 13.5 Lead

Sodium 6 Rubidium

Calcium 3 Magnesium

Potassium 1.5 Arsenic

~M~in~o~r-=E~le~m~e~n:l::ts:,--",:(~P.EP.:!MI:.I.) __,Cesium

Carbon Dioxide 2000 Hydrogen Sulfide

Iron (Ferrous) 1000 Copper

Manganese 930 Methane

Strontium 430 Cadmium

30 Ammonia 420 Antimony

Lithium 410 Aluminum

Zinc 370 Silver

Boron 330 Chromium

Silicon 250 Tin

Barium 130 Selenium

Nickel

Bismuth

Beryllium

Radionuclides

Radium 226

Radon 222

Lead 210

Radium 228

Thorium 228

5,358,700

2.01 .081

.064

1.88 .012

.18

.028 .004

34.7

.17 .005

.026

some

yes

1.84 .058

.5 .038 .7

7b 8

pH Zn Fe pH Zn Fe 20

2.07 .51 2.0 .5

2.5 .19 3.2 .23

73.2 68

2.09 .048

.9 .062 (5.5) 1.3 .052

1.86 .01

.7 .16 .8

1.29 .004

8.3 35.3

1.33 .cm

2.0 .03

yes

heavy

1.97 .009-

1.0 .22 1.4 .15

0.21 .007

10.6 26.8 9.7 26.2

.15 .005

.7 .006 6.7 .006

trace trace

yes slight

1.3 .87

4.1 3.1

TABLE 4-continued

Zn SX Assay Data Summary

Run

Assay, giL

Organic

Aqueous

Scrub 2,

Organic

Aqueous

Strip,

Organic

Aqueous

Acid'n,

Organic

Aqueous

Scum in extract'n

Ppt in stripping

Reagent addition

gHCl per L

organic

g NH3 per L

organic

Extraction,

Organic

Rafrmate

% extracted

Scrub 1,

Organic

Aqueous

Scrub 2,

Organic

Aqueous

Strip,

Organic

Aqueous

Acid'n,

Organic

Aqueous

Scum in extract'n

Ppt in stripping

Reagent addition

g HCIIL organic

g NH31L organic

These data show 68 to 87% Zn extraction in 15 second

contact time at 90° to 95° C. using impeller mixing.

With in-line mixing and nine-second contact time, 68%

Zn extraction was obtained- Iron and Mn co-extraction

were 0.4 to 0.55 gIL. Only trace amounts ofCu and Pb 45

were co-extracted. The organic loadings were (in gil)

1.9 to 2.1 Zn, 0.5 Fe, and 0.35 Mn.

The loaded organic was scrubbed in two countercurrent

stages with 5 gil NaCl+3 gil CaCh, pH 2 (HCl)

solution plus some S02 injected into the mixer(s) at 75° 50

to 85° C. Greater than 98 and 99% of the Fe and Mn,

respectively, were scrubbed. Less than 1% of the Zn

was scrubbed from the organic. The scrubbed organic

assayed (in gil) 1.9 to 2.0 Zn, 0.01 Fe, <0.003 Mn, 0.007

Pb, and 0,001 Cu. 55

Contacting the scrubbed organic with 54 gil NH3

plus 50 gil CaCh for three minutes at 65° to 75° C.

stripped 98 + % of the Zn. The strip solution assayed

(in gil) 27 to 35 Zn, about 44 NH3, 0,007 Cu, and

<0.002 Fe, Mn, and Pb. 60

In the acidification stage, the stripped organic was

neutralized with HCl before recycling. HCl required

for neutralization ranged from 0,897 to 1.3 grams 100%

HCl per liter organic or about 0.4 to 0.7 pounds 100%

HCl per pound Zn. An estimated 50% of the acid re- 65

quired was due to the aqueous entrained in the organic.

Phase separation rates were rapid, less than 0.21 sq

ft/gpm O+A inthe extraction stage, and less than 0.7

TABLE 8

Stripped

Organic

Extraction Scrub Strip Wash

Run time, min. 345

No. stages 2 2 I I

Org. vo!., L 33.0 33.0 33.0 33.0

Feed Aq vol, L 147 3.0 2.32 3.13

HCI vol, L .655

Flowrate, mlImin

Organic 96 96 96 96

Aq feed 426 8.7 6.72 9.07

Aq recycle 0 39 41 39

Total 522 143 143 143

Mixer vol, ml 216 140 450 140

Settler vol, m1 1000 1000 1000 1000

diam., cm 6.1 6.1 6.1 6.1

area, sqft .031 .031 .031 .031

mix time, min .41 1.0 3.1 1.0

Settling

Time, min (0 + A) 1.9 7.0 7.0 7.0

Rate, sqft/gpm .23 .83 .83 .83

(0 + A)

3. Stripping

Greater than 99% Zn stripping was achieved at 75° to

80° C. with 55 gil NH3+50 gil CaCh solution.

The strip solution boiled at 85° C.

Pregnant strip solution assays were 27 to 28 gil Zn

and 40 to 45 gil NH3 (ratio NH3/Zn= 1.6).

NH3 addition averaged 1.8 pounds NH3 per pound Zn

extracted (Runs lOa, lOb, 11).

Residual Fe left in the scrubbed organic reported in

the strip solution as a rust-colored gelatinous precipitate

which did not filter well. About 0.05 grams

dry precipitate solids were formed per liter feed

brine. Run 10+11 precipitate assayed 12% Zn,

22% Fe, 7.1% Ca, 2.5% Pb, and <0.05 ozlton Ag.

The precipitate contained 1.2% of the total Zn fed

to Sx.

4. HCl Consumption

HCl required to neutralize the stripped organic decreased

from 0.4 to 0.09 pound HCl per pound Zn

extracted when the stripped organic was washed

with neutral 50 gil CaChsolution before recycle to

extraction (Run lOa versus Run 11). In Run 11,

HCl was added to the brine feed to maintain the

raffmate at pH 3.0 to 3.4.

5. SX Run 11

The best overall results were obtained in Run 11.

Conditions and results for this run are given in

Tables 8-10 respectively.

The SX circuit of the present invention was per-

30 formed under the following conditions reported below

and in Table 8. For the in-line mixer, each stage consisted

of two 1.5 cm diameter X 122 cm glass tubes filled

with 5 or 6 rom glass beads, steam jacketed. Total void

space was 216 cc per stage. 01A flow was an upflow

35 through the in-line mixer. The feed solutions included

the organic: 10 vol % Aliquat 336 and 10 vol % Exxal

10 in Norpar 15. The feed brine (sample 45235) was

treated with 25 g Fe/150 L brine, and kept under nitro-

40 gen. Brine was passed through a filter containing Fe

powder, then hot through a column ofFe wool. The pH

adjustment was made with about 10 gIL HCI added to

the brine to maintain a raffmate pH of 3.0-3.4. The

scrub solution was raffinate diluted with water, adjusted

to pH 2 with HCl. The strip solution was 55 gIL NH3

and 50 gIL CaCho The Stripped organic wash solution

was 50 gIL CaCI2. S02 was added by sparging 10-15

cc/minute gaseous S02 into scrub 1 mixer.

5,358,700

80-90

75-85

70-80

Temp.

·C.

O/A ratio

in mixer

TABLE 6

No. of

Stages

Scrub

Strip

S. organic wash

The test results are summarized in Table 7 below.

TABLE 7

These test results show the following:

1. Zn Extraction 45

With one extraction stage, Zn extractions in 25- and

50-second contact time were the same (an average

of 83.5%) with an organic loading of 1.7 gil Zn

(Run 9a). Increasing the organic loading, to 1.9 gil

Zn, decreased Zn extraction to approximately 79% so

(Run 9b) .

With two countercurrent stages and 25-second

contact per stage, Zn extraction increased to about

95% with organic loadings of 2.3 gil Zn (Runs lOa

and 11). Increasing the organic loading, to 2.7 gil 55

Zn, decreased Zn extraction to 84% (Run lOb).

2. Fe Extraction and Scrub

Fe loadings on the organics ranged from 0.18 to 0.28

gil. Scrubbing with 5 gil NaCl + 3 gil CaCh (pH

2) solution appears to be more effective in remov- 60

ing Fe from the loaded organic (98 %, Run 9a)

than diluted, pH 2 raffinate (81%, Run lOa). About

0.5% of the extracted Zn reported in the spent

scrub solution (Run 11). S02 appears to be helpful

in scrubbing, in that less Fe precipitation occurred 65

when S02 was used. There was no precipitation

when the spent scrub solution from Run 11 was

added to the extraction raffinate.

Run 9a 9b lOa lOb II

Extract'n I 2 2 2

stages

Flowrate,

mlImin

Organic 108 87 91 65 96

Brine 404 427 433 438 426

Scrub 10 II 11 9 9

feed, aq

Strip 6.4 6.5 6.7 6.2 6.7

feed aq

Wash 0.75 0.66 0.80 0.62 9.0

feed aq

Scrub sol'n NaC!. dil dil dil dil

CaCI2 raff raff raff raff

S02to yes no yes yes yes

scrub

S. organic acidic acidic acidic acidic neutral

wash sol'n NaCI NaCl NaCI NaCI CaCI2

Strip temp. 80-85 80 80 75 75

degC.

Extract'n 25-50 25-50 25/stage \ 26/stage 25/stage

time, sec

Raffmate, .0845 .115 .030 .088 .022

glLZn

Zn extracted 83.5 79 94 84 96

L. organic,

glLZn 1.66 1.89 2.31 2.67 2.31

gIL Fe 0.265 0.2 0.21 0.19 0.26

Scrubbed org. 0.006 0.013 0.039 0.037 0.046

gIL Fe

Fe scrubbed 98 94 81 81 82

HCI added, 0.51 0.44 0.42 0.39 0.09

glgZn

NH3 added, 2.1 2-l 1.7 2.0 1.7

glgZn

Norpar 15

<0.2

Exxall0

<0.1

0.7

3.0

Assay, mgIL

<0.2

Amine

TABLE 11

Raffinate

Fe scrub solution

Strip solution

are steam jacketed. The total void space is 216 cc per

stage upflow through the in-line mixer. Run time was

about 345 minutes.

The scrub solution was made up of raffinate from a

5 previous run diluted 1/40 with H20, and the pH adjusted

to 2 with HCl. The strip solution was 55 giL

NH3 and 50 giL CaCho The strip organic wash solution

was 50 gIL CaCho Between 10-15 cc/min. of gaseous

S02 was sparged into the scrub 1 mixer.

10 The feed brine from a continuous panel SX test was

assayed and found to contain 1 mg/L Ag and less than

0.5 mg/L Ag (reported in the strip solution). This corresponds

to a Ag/Zn ratio= <0.0005/29. A trace amount

of Pb (2 mg/L Pb) was found in the Zn strip solution.

Most of the Pb (extracted and entrained) appears to

have been scrubbed from the organic and precipitated

with the Fe during stripping.

The following data are ofparticular interest. The zinc

20 extracted in two countercurrent stages was 95.6%; feed

and raffinate assays were 0.50 and 0.022 gil Zn, respectively.

The loaded organic assayed 2.31 gil Zn and 0.26

gil Fe. After two countercurrent scrub stages with

diluted pH 2 raffinate, the scrubbed organic assayed

25 2.29 gil Zn and 0,046 gil Fe. Eighty-two percent of the

Fe and 0.5% of the Zn were scrubbed from the organic.

About 0.4 liter S02 per liter organic was injected into

the first scrub mixer to maintain reducing conditions

during the scrub. In one stripping stage with 55 gil

30 NH3 plus 50 CaC12 solution at 75° C., 99+% Zn stripping

was achieved producing a pregnant strip containing

(in gil) 28.5 Zn, 40.4 NH3 (total), 0,002 Pb, <0.0005

Ag, and pH 9.9. NH3 added in stripping was 3.8 grams

100% NH3, per liter organic or 1.65 grams per gram Zn

35 stripped.

The residual Fe in the scrubbed organic formed a

gelatinous Fe hydrate precipitate in the strip solution.

This precipitate did not cause any apparent phase separation

problem. Washing the stripped organic with 50

40 gil CaCh solution removed the entrained NH3 from the

organic. The amount of HCI added to the feed brine to

maintain pH 3 in extraction was 0.20 grams 100% HCI

per liter organic or 0.087 grams 100% HCl per gram Zn

extracted. The feed brine assayed 1 mg/L Ag and less

45 than 0.5 mglL Ag reported in the strip solution. A trace

amount of lead (2 mglL Pb) was reported in the strip

solution. Most of the Pb appears to have been scrubbed

from the organic and the rest precipitated with the

residual Fe during stripping. The Fe precipitate assayed

50 2.5% Pb, equivalent to about 5 mg/L Pb in the scrubbed

organic.

6. Organic Stability

Infrared scans of Run 8 and 11 organics and fresh

organic were the same, indicating that no significant

change in chemical composition occurred in

about ten organic cycles.

7. Organic Solubility

Soluble amine, Exxal 10, and Norpar 15 were determined

by the freon extraction-chromatographic

method in the aqueous samples from Run 11 as

shown in Table 11.

5,358,700

.120

.117

2.45

<.0005 .021

<.0005 .028

<.0005 .002

.0010

.0007

<.05

gpt

7.07

40.4

3.7

44.3

4.9

TABLE 9

Stripped

Organic

Extraction Scrub Strip Wash

86-96 79-88 75 70

3.0-3.4 1.9 9.9 9.9

slight slight

TABLE 8-continued

Zn Fe Mn

.500 1.36 (1.34)

3.2

.76 .54

3.1 .022 1.28

2.31 .26

2.6 .18

2.32 .052

1.8 .089 3.81

2.29 .046

1.9 .25 .32

.015 .023

9.9 28.5

.003 .004

9.9 .41

3.2 .025

1.4 .13

10.0 29.4

8.8 .57

12.0 22.3

The following reagent addition occurred before assays

were performed for the amounts of minerals and

reagents at various stages (reported in Table 9 below):

HCl in pH adjustment: 19.8 ml 0.27N HCl/L organic or

0.20 g 100% HCliL organic; NH3 in stripping: 70.3 ml

55 giL NH3/L organic or 3.8 g 100% NH31L organic.

Temp, deg. C.

Scum formed

Assays

The amount of zinc recovered at each stage is reported

in Table 10 below.

TABLE 10

Amount Zn Assay gZn Zn Dis!. %

Feed brine 147 L .500 gIL 73.5

Strip soln 2.32L 29.4 gIL 68.2 93.2

Raffmate 147 L .025 gIL 3.7 5.0

Scrub soln 3.00L .13 gIL .4 .5

Strip ppt 7.4 g 12% _.9_ 1.2

73.2 100

Each stage consisted of two 1.5 cm diameter glass

tubes (122 cm) filled with 5 or 6 mm glass beads which

Brine

feed

Profile

samples,

end of

Extr'n,

barren

Organic

Raff.

Extr'n

Organic

Raff.

Scrub,

ll&..L

Organic

Scrub,

Organic

Strip

Organic

S.org

wash

Organic

Com-

Raff.

Scrub

soln

Strip soln

S.org

wash

Strip

solids

(2 runs;

14.7 g)

TABLE II-continued

Norpar IS

5,358,700

Both Fe and Mn are partially co-extracted with Zn

from untreated geothermal brine by Aliquat 336. Pretreating

the brine with NaHS and Zn or Fe powder to

make certain all the Fe was reduced to Fe+2 did not

3.7 <0.2 5 significantly decrease Fe extraction.

ExxallO

Assay, mgIL

Amine

Organic wash solution

Sample

TABLE 13

Test 2 3 4

Scrub soln

HCI, gIL 3.7 .37 .37 .22

NaCl, gIL 0 100 0 5.0

CaCI2, gIL 0 40 0 2.0

Phase break OK OK emulsion OK

Organic clear clear formed clear

Aqueous clear clear sit. cldy

Scum no no no

Assays, gIL

S. organic, Fe .17 .37 .05

Zn 1.76 2.01 1.80

Mn <0.3

S. soln, Fe .27 .030 .5

Zn .39 .029 .2

Mn .3

% scrubbed, Fe 56 11 82

Zn 16 I 8

Mn >88

Dist. coefficient

KAIO, Fe 1.6 .1 10

Zn .22 .01 .11

Mn >10

Separation factor 6 90

Fe/Zn

gIL

Zn .73

Fe, total 2.59

Fe+3 <.01

Mn .24 25

Pb .13

Si 224

CI 0.04

EXAMPLE 3

Removal of Fe and Mn from Geothermal Brines by

Scrubbing

Shakeout tests using actual geothermal brine samples

showed Fe and Mn are co-extracted with Zn. Various

methods of minimizing their extraction were tested.

A. Zn Extraction

A zinc extraction was performed using a geothermal

brine (GTB) sample containing the following elements,

at pH 4.3:

An organic containing 10% vIv Aliquat 336 and 10% 30

vlv ExxaiiO in Norpar IS which had been conditioned

through one extraction, strip and scrub cycle was assayed.

This GTB was contacted with the organic in a resin

kettle (RK) or a sealed bottle (Btl) under N2at a temper- 35

ature of 88°_92° C. The AIO ratio was 3.3-3.5/1. The

results of these tests are shown in Table 12 and illustrate

that Zn powder reduced Fe in the organic phase.

TABLE 12

Test 2 3 4 5

GTB pretreatment none NaBS Zn Zn Fe

with powder coarse powder

Contacted in RK RK Btl Btl Btl

Time, min. 2 3 2 0.5 0.5

Organic, gIL Zn 2.14 1.95 2.33 2.80 2.07

Fe 0.49 0.51 0.56 0.25 0.40

Mn 0.27 0.17

Raffmate, gIL Zn 0.11

pH 3.0 4.0 2.8 3.5 3.6

B. Fe and Mn Scrub From Organic

Fe and Mn scrub tests using dilute HCI, NaCl, and

CaCh solutions are summarized in Tables 13 and 14

10 below. A dilute chloride solution containing (in gil) 5

NaCl, 2 CaCh, and 0.2 HCI selectively scrubbed Fe and

Mn from Zn-Ioaded Aliquat 336 organic.

The feed organic was made up of 10% vIv Aliquat

336 and 10% vlv Exxal 10 in Norpar IS, and was con-

15 tacted with geothermal brine. An X-ray fluorescence

assay revealed a composition of 2.02 giL Zn, 0.42 giL

Fe, and 0.27 giL Mn. The scrub solutions were prepared

from reagent grade NaCI, eaCh and HCl.

Contact was made in sealed 8 oz. bottles for 5 min. at a

20 temperature of between 85°-89° C. The 01A ratio was

------------------- 1.211.

These results illustrate that without salt concentrations

or reasonable amounts of acid, emulsification occurs.

TABLE 14

Fe and Mn Scrubbing with Dilute Acidified NaCI + CaCI2 Solution

Organic

Scrub soln

Contact Time

O/A ratio

Temperature

Method

10 vol % Aliquat 336 + 10 vol % Exxal 10 in Norpar 15. Loaded by

contacting with Geothermal brine to (in gIL) 2.09 Zn,

.72 Fe, .37 Mn

5.0 gIL NaCI + 2.0 gIL CaCI2, pH 2.0W/HCI

2 min

2/1

85-90· C.

Scrub soln contacted three times with fresh portions of loaded

organic.

Dist. Coeff.

Assay, gIL Kala- Sep'n Factor

Contact Sample Fe Mn Zn Fe Mn Zn Fe/Zn MnlZn

Loaded .72 .37 2.09

organic

Scrub soln 1.03 .82 .15 5.15 410 .077 67 5330

Scrubbed

organic .20 .002 1.95

2 Scrub soln 1.97 1.98 .12 7.04 990 .057 124 17408

5,358,700

TABLE 14-continued

Fe and Mn Scrubbing with Dilute Acidified NaCI + CaCl2 Solution

Scrubbed

organic .28 .002 2. II

3 Scrub soln 2.83 2.86 .12 9.76 953 .057 170 16604

Scrubbed

organic .29 .003 2.09

Sodium Chloride

10 ation. Settling times were set at 15 minutes. The aqueous

to organic ratios varied according to the objective

of the test. The reagents used for extraction, stripping

and regeneration were: Adogen-464 (10 percent by

volume), sodium sulfate, and sodium chloride, each at

15 10 percent weight solution.

In order to evaluate the extraction kinetics for extraction,

agitated solvent extraction tests were conducted at

2 and 5 minutes contact time. Zinc recovered was calculated

by difference between the feed and raffinate solu-

20 tions.

Most of the solvent extraction experiments were performed

using a quaternary ammonium compound as the

extractant, (Adogen 464). Only one other extractant

was tested, a secondary amine, Amberlite LA-2 made

by Rohm & Haas. The test conditions were similar to

those used with the Adogen 464 extractant with the

appropriate amounts of modifier (10 volume percent)

and diluent (80 volume percent).

In some cases the stripped organic had to be regenerated

with a sodium chloride or hydrochloric acid solution

to avoid transfer to sulfate or hydroxide ions into

the extraction stage.

An important aspect for extraction of zinc with a

quaternary ammonium compound was the evaluation of

35 various reagents for stripping. A list of the stripping

agents tested is provided below:

TABLE 15

Zinc Solvent Extraction Summary of Results

Test No. A/O Ratio %Zinc Extraction

EXAMPLE 4

Varying the Aqueous to Organic Ratio

A series of solvent extractions were conducted at

several power plants to optimize the Zn extraction step

of the SX circuit of this invention. An exemplary analysis

of the aqueous to organic ratio (Ala) by volume

percent for Zn extraction at one plant is shown in Table

15 below.

I 3.3 94.0

2 3.7 93.8

3 3.5 93.6

4 3.7 89.3 5 2.5 NA* 25

6 3.7 NA*

7 5.9 65.9

8 4.5 84.2

9 2.6 94.6

10 3.89 90.2

30 • Note: Not Available

Other power plants showed similar relationships between

Ala ratios and % Zn extraction.

EXAMPLES

Zn Strip Assay From Aliquat 336 with NH4CI

The following example illustrates that the methods of

the prior art, e.g., extraction with N14CI and acid does Stripping Solution Regenerating Solution

not successfully strip Zn from the brine. 40 -1-."':":'S-od"::i~um-S-u-Ifa-t-e-(I-O-%-W-T)-----S-o'::;di-um-c-hl-o;;;'n-'d-e-(-IO-o/<-o-

The feed organic was made up of 10% vlv Aliquat WT)

336 ad 10% vlv ExxallO in Norpar 15,2.16 giL Zn. A 2. Ammonium Chloride/Ammonia Hydrochloric Acid

strip solution of varying amounts of N14CI in O.IN HCI (105M) (5% WT)

was used. Contact was made in a balled beaker at a 3. Distilled Water

4. Concentrated Hydrochloric

temperature of 800 _850 C. for five minutes. The alA 45 Acid

ratio was 2/1. The test results are illustrated in Table 16 5. Hydrochloric Acid (18% wT)

below. 6. Sodium Sulfate/Ammonia

Strip soln Zn %Zn

Test glLNl4CI Sample pH gIL stripped 50

Feed organic 2.16

50 S. organic 2.06

S. soln 1.9 .054 1.2

2 250 S. organic 1.92

S. soln 1.4 .14 3.2 55 3 400 S. organic 1.90

S. soln 1.9 .24 5.6

TABLE 16

EXAMPLE 6

NazS4 Strip is not Desirable

Tests were conducted to determine if an Na2S04 Zn

strip solution would be preferable to the ammoniacal

CaCh solution used in this invention.

These experiments included 3 stages ofextraction and

the same number of stages for stripping and regeneration

(locked cycle). All the contact times were maintained

at 5 minutes for extraction, stripping and regener-

The solvent extraction experiments conducted to

evaluate the performance of the reagents for stripping,

were designed to increase the zinc concentrations in the

strip solution. In order to accomplish an increase in zinc

concentration in the strip solution, the organic was

contacted with fresh brine at a volume phase ratio of4.1

parts of aqueous to 1 part of organic in three different

stages. Each extraction stage was followed by locked

cycle stripping at a volume phase ratio of 1.25 parts of

strip solution to 1 part of organic. The regeneration

stage (when necessary) was conducted at a volume

60 phase ratio of 2.5 parts of regeneration solution to I part

of organic.

Extraction of zinc was conducted under strong agitation

and temperatures of approximately 80 degrees Celsius

for contact times ranging from 1 to 5 minutes. Strip-

65 ping and regeneration stages were conducted at ambient

temperature with contact times ranging from 1 to 5

minutes. The settling times allowed for phase separation

ranged from 3 to 15 minutes.

decreased in locked cycle stripping. After 3 cycles of

extraction, stripping and regeneration, organic residual

loadings as high as 2.9 gram per liter zinc were observed

following stripping stage. Maximum stripping liquor

5 loads of only 3.2 gpl were in equilibrium with the organic

phase. The zinc recoveries observed in the tests

conducted were in the 60 to 70 percent range with an

organic that had been through at least one cycle of

extraction, stripping and regeneration. Higher extractions

were achieved in the fIrst cycle when barren organic

was used. Stripping with ammonium chloride/

ammonia formed emulsions and phase disengagement

was slow. These emulsions were caused mainly by precipitation

of iron hydroxides. EmulsifIcation may not

occur if iron is not co-extracted with zinc.

Ammonium chloride/ammonia 105M solution proved

to be effective as a stripping reagent at full strength.

The effIciency in stripping decreases with chloride and

zinc transfer. Titration of the organic after ammonium

chloride-ammonia strip indicated that the organic contained

up to 4.4 gram per liter hydroxyl ion. This base

would have to be neutralized prior to sending the organic

to extraction or regeneration stages. If organic is

not regenerated after ammonia strip, 'precipitation of

iron will occur during the extraction stage.

Stripping with concentrated hydrochloric acid

caused third phase formation. In order to avoid third

phase, 18 percent weight hydrochloric acid was used.

At this concentration, the reagent is no longer effective

as a stripping agent. A washing stage (with NaCI) was

needed to strip the acid loaded onto the organic prior to

subsequent zinc extraction.

Stripping with water was effective only at a volume

35 phase ratio of 10 to 20 parts of organic to I part of

aqueous. The zinc concentration of the strip solution at

both 10 and 20 organic to aqueous ratios, after 1 cycle

was 2.1 gram per liter zinc. Good phase separation was

obtained only at low aqueous to organic ratios but an

40 increase in zinc concentration was not obtained. The

lower loading results may be skewed by the kinetics of

Zn+2 transfer being limited at such low aqueous ratios.

There were no indications of sulfate transport into the

raffmate after zinc extraction. The brine fed into the

45 system as well as the products obtained from the solvent

extraction circuit all showed concentrations of less than

0.005 gram per liter sulfate. However, chloride transfer

to the sodium sulfate salt makes its use not economically

feasible.

Numerous modifIcations and variations of the present

invention are included in the above-identifIed specifIcation

and are expected to be obvious to one of skill in the

art. Such modifIcations and alterations to the compositions

and processes of the present invention are believed

to be encompassed in the scope of the claims appended

hereto.

What is claimed is:

1. A method of extracting zinc from an aqueous brine

containing a mixture of salts and other elements includ-

60 ing Zn, Fe, and Mn comprising the steps of (1) contacting

the aqueous brine with a selected organic extractant

to remove Zn from the brine, producing an organic

extractant loaded with Zn; (2) scrubbing the loaded

organic extractant with a dilute acidifIed brine to remove

co-extracted Fe and Mn from the loaded organic

extractant, producing a scrubbed organic extractant

containing Zn; and (3) stripping the Zn from the scrubbed

organic extractant with a solution of ammonia and

5,358,700

6.524

Percent Zn

Stripped

Regeneration

2.5/1

5 minutes

15 minutes

3.16

0.50

3.08

2.28

10.72

N/A

2.5/1

5 minutes

15 minutes

TABLE 17

3/1

5 minutes

15 minutes

Solvent Extraction Stage

Extraction Stripping

Summary of Results Stripping Reagents Evaluation

Strip Solution

Zn Analyses

(gramlliter)

Stripping

Reagent

Sodium sulfate

(10% WT)

1.5 M NH4CI

1.5 M NH3

Hydrochloric

Acid (37% WT)

Hydrochloric

Acid (18% WT)

Water

(Distilled)

1.5 M Na2S04

1.5 M NH3

The following parameters were specifIc for each

extraction, stripping, and regeneration stage:

Conditions

A/O Ratio:

Contact Time

Settling Time

IStripping efficiency drops due to chloride transfer.

2Hydroxyl is loaded during stripping.

lThird phase occurred.

4Not effective.

SFormed emulsions at 0/A ratios of 5 or lower.

6A metal balance was not conducted in this test.

The main objective was to build-up the zinc concentration in the strip solution.

The results tabulated above indicate that none of the

reagents tested was particularly effective for stripping

zinc. The maximum zinc concentration achieved was 55

approximately 3 grams per liter. A higher strip liquor

concentration was achieved with a sodium sulfate/ammonia

solution of 10.7 gram per liter zinc but the effIciency

of stripping was low; Le., multistage contacts

would be required.

Transfer of chloride into the strip solution lowered

the effIciency for stripping in most cases. A low effIciency

in stripping affected significantly the zinc extraction

effIciency by lowering the capacity of the extractant.

Maximum loading for the organic was determined 65

to be approximately 4.8 gram per liter zinc at brine

levels of about 700 ppm Zn+2• The effIciency in the

extraction stage decreased as the strip effIciency also

The temperature was maintained at 85 to 90 degrees

Celsium during extraction. The pH of the reduced brine

was adjusted to 3.5 to 4.0. The extractant contained 10

volume percent of a quaternary ammonium compound,

10 volume percent of decyl alcohol as modifIer and 80 15

volume percent of diluent Norpar 15 made by Exxon.

The reagents used for stripping and regeneration were

10 percent solutions by weight of sodium sulfate and

sodium chloride respectively.

Regeneration of the organic is deemed necessary to 20

prevent sulfate transport into the brine. In this experiment,

zinc extractions were fairly high at approximately

84 to 87 percent.

In an attempt to build-up the strip solution zinc concentration,

the aqueous to organic ratio was changed to 25

1.25 to 1 for stripping. Each extraction cycle was followed

by locked cycle stripping and regeneration. A

total of 3 cycles per test were conducted in each experiment

for strip reagent evaluation. The following Table

17 summariz~s the results obtained in the stripping rea- 30

gents evaluatIon.

5,358,700

a suitable salt to produce a concentrated and purified

aqueous Zn strip solution having a Zn concentration of

at least 10 giL.

2. The method according to claim 1 wherein said 5

brine is a geothermal or synthetic brine.

3. The method according to claim 1 which occurs in

a closed system from which oxygen is excluded.

4. The method according to claim 1 wherein the 10

organic comprises a quaternary amine.

5. The method according to claim 4 wherein the

quaternary amine contains a long-chain alkyl group.

6. The method according to claim 5 wherein said 15

amine contains at least three said long-chain alkyl

groups and one methyl group.

7. The method according to claim 4 wherein the

organic extractant further comprises a modifier and a 20

diluent.

8. The method according to claim 7 wherein the

modifier is a long-chain alkyl alcohol and the diluent is

a low-vapor pressure, low-viscosity mineral oil. 25

9. The method according to claim 1 wherein the

organic extractant is contacted with the brine for less

than I minute.

10. The method according to claim 1 wherein the

ratio of the aqueous brine to the organic extractant is

about 4:1.

11. The method according to claim 1 wherein the

brine is at a temperature of between about 50° to about

1100 C. and atmospheric pressure when contacted with

the organic.

12. The method according to claim 1 wherein one or

more of the steps is repeated.

13. The method according to claim 1 wherein the

scrubbing step further comprises the step of contacting

the organic extractant with a scrub solution at a pH of

between about 2 to 5, said scrub solution containing a

non-precipitating salt selected from the group consisting

of NaCI, KCI, CaCh and N14Cl.

14. The method according to claim 1 wherein the

suitable salt is a non-precipitating salt selected from the

group consisting of NaCI, KCI, CaCh and N14Cl.

15. The method according to claim 1 wherein said

purified Zn strip solution contains a Zn concentration of

greater than about 10 giL.

* * * * *