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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
I I
L Zn EXTRACTION Fe,Mn SCRUB Zn STRIP NH3 WASH 1-_ J
- (STEP I) - • (STEP 2) - .. (STEP 3) - - .. (STEP 4)
RAFFINATE
I
SCRUB
SOLUTION
1-1
REINJECTION
STRIP
SOLUTION
1
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
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
o
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,J:>.
SCRUB
RAFFINATE SOLUTION
I I
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REINJECTION.
STRIP WASH 00 SOLUTION SOLUTION n=>-
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I
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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
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EXTRACTION I -I SETTLER
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5,358,700
1
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
2
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
3
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
4
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.
15
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
5
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
6
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
7
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:
8
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
30
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
.002
.002
<.03
<.05
<.01
<.05
<.01
<.05
<.001
<.001
<.001
<.001
<.002
Ni <.005
Cu
Mo
y
Al
S
Fe
Mg
Ti
P
Co
Nb
Ni
Rb
Zn
10
56
32
.1
.1
.07
.03
.03
.02
.01
.007
.007
.005
.005
.005
.004
.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
CI
Na
Si
Ba
Pb
Ca
K
Sn
Mn
Cr
Th
As
V
W
Sr
U
Zr
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
9
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
50
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
65
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
.02
.02
.02
.02
.01
.01
<.1
<.005
<.1
<.2
<.04
<.05
<.005
<.005
Cr
V
W
U
Zr
Cu
Mo
Si
y
Al
S
Ti
P
Co
Nb
214
55
36
22
2.4
2.1
.7
.6
.3
.2
.2
.1
.09
.04
.03
2. XRF semi-guantitative assays
gIL
CI
Na
Ca
K
Fe
Mn
Zn
Sr
Ba
Pb
Mg
Rb
Sn
As
Th
100
100
40
15
10
7
5
3.0
1.2
0.9
0.7
0.4
0.2
0.2
0.2
0.2
om
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.
12
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.
15
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
35
5,358,700
2.01 .081
.064
1.88 .012
.18
.028 .004
34.7
.17 .005
.026
some
yes
11
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
25
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
40
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
14
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)
5
25
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.
15
20
5,358,700
80-90
75-85
70-80
Temp.
·C.
2
2
2
O/A ratio
in mixer
2
II
13
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
<0.2
<0.2
Exxall0
<0.1
0.7
3.0
Assay, mgIL
<0.2
18
41
Amine
TABLE 11
Raffinate
Fe scrub solution
Strip solution
16
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
Pb
.120
.117
2.45
<.0005 .021
Ag
<.0005 .028
<.0005 .002
<.0005 .002
.0010
.0007
<.05
gpt
7.07
40.4
3.7
44.3
4.9
15
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)
pH
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.
15
Temp, deg. C.
pH
Scum formed
Assays
55
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
Aq
Scrub,
~
Organic
Aq
Strip
Organic
Aq
S.org
wash
Organic
Aq
Com-
~
Raff.
Scrub
soln
Strip soln
S.org
wash
Strip
solids
(2 runs;
14.7 g)
TABLE II-continued
17
Norpar IS
5,358,700
18
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
41
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
40
45
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
19
5,358,700
20
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
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.
22
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
50
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
21
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
10
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
23
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
24
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.
* * * * *
30
35
40
45
50
55
60
65