Note: Descriptions are shown in the official language in which they were submitted.
~ ~ 7 7~ ~1
1 In a liquid membrane process for removing ions
2 from solution which comprises contacting a solutlon contain-
3 ing a first ion with an emulsion, said emulsion comprising
4 an external phase which is immiscible with said solution
and contains a complexing agent, said complexing agent be-
6 ing cap~ble of forming a first complex with said first ion,
7 which is soluble in said external phase and an internal
8 phase, the improvement which comprises providing a second
9 ion, in the internal phase, of the emulsion, said second
ion being capable of converting said first complex to a sec-
ll ond complex by replacing said first ion in said first com-
12 plex, said second complex being also soluble in said ex-
13 ternal phase, whereby the first ion diffuses from said solu-
14 tion into sald internal phase, and said second ion diffuses
from said internal phase into said solution. More particu-
16 larly, the instant invention comprises maintaining ~he con-
17 centration of the second ion, in the solution, at a suffi-
18 ciently low level to allow formation of the first complex, at
19 the interface of the external phase of the emulsion and the
solution, and maintaining the concentration of the second
21 ion, in the internal phase of the emulsion at a concentration
22 sufficiently high to convert said first complex into a sec-
23 ond complex. Preferably, the first ion is a metal ion - for
24 example, copper, or a complex ion, such as HgC14 = comprising
a metal constituent and said second ion is either hydrogen
26 or hydroxyl ion. From the two examples of the preferred
27 embodiment, it is clear that the metal may be in either a
28 cationic or anionic form. The complexing agent is generally
29 an oil-soluble ion-exchange material - for example, an amine
or oxime which is insoluble in the aqueous solution and pre-
~ .
-- 2 --
10~724~
1 ferably also insoluble in the internal phase of the emul-
2 sion. In a preferred embodiment of the instant invention,
3 a relatively high pH, i.e. low-acidity copper solution (a
4 pH of from 1.5 to 3.5) is contacted with an emulsion com-
prising as the externalph ~ a hydroxyoxime dissolved in a
6 hydrocarbon, and as the internal phase an aqueous solution
7 having a high hydrogen ion concentration (that is, a pH of
8 less than 0.5, i.e. an acid concentration of 30 g/l H2SO4 or
9 more) at mild agitation conditions whereby the cupric ions
0 complex with said hydroxyoxime, permeate through the extern-
al phase of the emulsion, and are trapped in the internal
12 phase by the conversion of the copper complex to the hydro-
13 gen complex in the presence of the high acidity.
4 The removal of specific ions or compounds from di-
lute aqueous solution and concentrating them in another aq-
6 ueous phase is desirable in many metallurgical and waste
17 water treating processes. Processes which have been used sr
18 suggested towards this goal, and which impact on the present
19 invention, are the following:
l. Extraction into an organic phase which may
21 contain a complexing or ion exchange agent followed by re-
22 extraction into another aqueous phase having a high concen-
23 tration of another ion of the same polarity.
24 2. Liquid membrane permeation with a membrane
2s which allows permeation of the specific ions or compounds in
26 one form, followed by reaction with a dissolved chemical en-
27 capsulated as an aqueous phase inside the membrane so as to
28 convert the permesting ions or compounds into a nonpermeat-
29 ing species, i.e. by neutralization or precipitationO See
~ for example,U.S. Patent No.3,617,546 and U.S.Patent No.
~ . . .
0 7 7 2 4
1 3,637,488.
2 In a liquld membrane process for removing ions
3 from solution which comprises contacting a solution contain-
4 ing a first ion with an emulsion, said emulsion comprlsing
an external phase which is immiscible with said solution
6 ant contains a complexing agent, said complexing agent being
7 capable of fonming a first complex with said first ion, which
8 is soluble ln said external phase, and an internal phase,
9 the improvement which comprises providing a second lon, in
o the internal phase, of the emulslon, said secont icn being
capable of converting said first complex to a second complex
12 by replacing said first ion in said first complex, said sec-
13 ond complex being also soluble in said external phase, where-
14 by the first ion diffuses from said solution into said in-
ternal phase, and said second ion diffuses from said internal
~ . .
6 phase into said solution. More particularly the instant
17 invention comprises maintaining the concentration of the
18 8econt ion, in the solution, at d sufficiently low level to
19 allow formation of the first complex at the interface of the
external phase of the emulsion and the solution, and maintain-
21 ing the concentration of the second ion, in the internal
22 phase of the emulsion at a concentration, sufficiently high,
23 to convert said first complex into a second complex. The
24 first ion is preferably a metal ion in either a cationic
or anionic form - for example, cupric ion or a complex
26 ion, such as HgC14 , comprising a metal component. Ions may
27 be removed from aqueous solutions and accumulated within
28 water-in-oil em~lsions by means of this processc To remove
29 metal ions, a complexing agent - for example, an oil-soluble
ion-exchange compound, is provided in the external, iOeO
, .~ :
., . ~
07 7 2 4~
1 membrane, phase of the water-~n-oil emulsionO The ion-ex-
2 change compound will be selected to be able to comblne se-
3 lectively with metal ion in a manner functionally related to
4 the presence of a second ion - for exsmple, hydrogen ion, in
the aqueous solution. In the case of cupric ion, the ion-
6 exchange compound may be selected from the group consisting
7 of aromatic and aliphatic hydroxyoximes and quinolines,
8 amines and other nitrogen compounds. In the case of other
9 ions, those skilled in the art will be able to select the
0 ion-exchange compound in accordance with the chemical iden-
11 tity of the ion which iQ to be removed and the principles
12 of the invention disclosed herein~
13 Preferably, for removing copper, ~he ion-exchange
4 compound is a mixture of ~ -hydroxy benzophenone oxime (LIX
65N) and an c~ -hydroxy oxime (LIX 63) which make up the pro-
16 prietary mixture known as LIX 64N marketed by General Mills
17 Chemical Co. Materials of this nature will combine with
.
8 cupric ions at high pHis, that is at pH~ l or higher (or a
19 N-ion concentration of O.l molar) and release the cupric ion
at hydrogen ion concentrations above that value, preferably
21 at 25-200 g/l H2S04
22 Actually, the ion exchange compounds exist in
23 equilibrium with cupric as well as hydrogen ions according
24 to the following equations:
Cu~+a + 2[HA]o ~ ~ ~ [CuA2]o + 2 H a
26 where:
27 Cu+ a - cupric ion in the aqueous phase
28 [HA]o - hydrogen form of the ion exchange resin,
29 in the organic phase,
[CuA2]o = copper form of the ion exchange resin, in
31 the organic phase
~ ~Je ~qark
0 7 72 41
1 H+a = hydrogen ion in the aqueous phase
2 From this equilibrium equation, which, in general,
3 obeys the equilibrium rule
4 equilibrium constant ~ K ~ [CUA2~o [H la
lCU++]a [HA]o2
6 where [ l represents the molar concentrations of the above
7 constituents in their respective phases.
8 From these equations it i9 apparent that the frac-
9 tion of the ion exchange resin which is in the Cu-form is
0 very dependent on the H-ion concentration, the higher the
11 [H+], the less will be ~CuA21o and vice versa.
2 The actual H+-ion concen~ration range over which a
l3 specific ion exchange resin will be effective (i.e. how low
14 does [H+l have to be to get a substantial fraction of the
lS resin into the CuA`2-form, and how high does the [H+l have
16 to go to make most of the CuA2 reconvert to the HA-form,
l7 thus releasing the complexed Cu~+) depends very much on the
8 K of the material or mixture of resins involved. In the case
l9 of LIX 64N and copper, for example, CuA2 formation is favored
at pH above about 1., and its reversion to the HA + Cu++ form
21 is favored when the stripping solution (iOe. internal emul-
22 sion phase) has an acid content of 25-30 g/l H2S04 and higher.
23 Prefer~bly, for effective stripping, H2S04 concentrations
24 should be 100-175 g/l.
With other LIX systems, effective complexing occurs
26 at acid concentrations as high as 30-100 g/l H2S04, while
27 the complex of Cu and the ion-exchange resin will reconvert
28 to the H-form at acid concentrations of 250-300 g/l.
29 It ls important to note that Cu transfer via the
ion-exchange containing oil membrane will take place from a
1C~77Z41
1 region of lower to a region of higher Cu-concentration pro-
2 vided the hydrogen ion concentration differences are in the
3 opposite direction. The precise or optimum levels of Cu and
4 H concentrations w~ll depend on the specific resin used.
The above discussion is exemplary, and it must be
6 appreciated that other metal or metal-containing ions, and
7 second ions other than H-ion, function slmilarly. Other
suitable second ions such as OH-, Cl-, S04', Na+, may be
9 used to drive metallic and metal-containing ions from re-
o gions of low concentration through the liquid membrane into
11 regions of high concentration, provided suitable oil-soluble
2 ion-exchange resins are employed (either cation or anion ex-
13 change type).
14 The external phase of the emulsion will also con-
~ain a solvent for said ion-exchange compound, although an
16 ion-exchange compound which 18 a liquid at the temperature
7 at which the process is carried out may be used neat, and
8 desir-bly a surface active agent to promote stability of the
19 emulsion. Solvents which are useful in the process of the
instant invention must be immiscible with the aqueous solu-
21 tion and capable of dissolving the desired ion-exchange com-
22 pound. Furthermore, the solvent must be such that a stable
23 emulsion may be prepared since the stability of the emulsion
24 is critical to the success of the process of the instant in-
vention. Solvents which are suitable in general for prepar-
26 ing the emul~ions used in the instant process include hydro-
27 carbon liquids, chlorinated hydrocarbons, etc. The ion-ex-
28 change compound, while having a certain amount of surface
29 activity, is generally combined with a surfactant in such
~ emulsion. This surfactant may be selected from those known
~ . . .
:
1077Z41
in the art provided it is stable under the conditions of op-
eration of the instant process. For example, in one of the
most preferred embodiments of the instant invention, the
second ion, which as further explained herein is necessary,
after complexing of the first ion and the ion-exchange
compound at the interface of the aqueous solution and the ex-
ternal phase of the emulsion, to provide decomplexing in the
internal phase of the emulsion, is a hydrogen ion. In this
preferred embodiment, the surfactant must be capable of pro-
viding stable emulsions and also must be stable to highly
acidic environments. In general, the various sbrface-active
agents and solvents which are useful in the process of the
instant invention as well as many of the ion-exchange compounds
are disclosed in U.S. Patent No. 3,779,907.
In this internal phase of the emulsion, the concen-
tration of the second ion is maintained at a level which
promotes decomplexing of the first ion with the ion-exchange :~
compound. For example, in the case of cupric ion and LIX 64N
the complex is formed at conditions of high pH - that is, a
pH of greater than l. This complex, however, is unstable in :
the presence of very low pH's - for example, a pH of less
than 0.5. Using this as an example of the process of the
~instant invention, the pH of the internal phase of the emul-
sion is maintained at less than 0.5, preferably at acid con-
centrations of 100-200 g/l H2S04, whereby, at the interface
_ ~ :
,_ .. . . .. ., .. .. , ____ ._.. _ _ ... ...
.. . . ...
:
.
;:.
1077Z41
of the internal phase and the external phase of the emulsion,
the complex is destroyed leaving cupric ion trapped in the
internal phase of the emulsion.
In the process of the instant invention an emulsion
is formed having all of the necessary characteristics des-
- 8A -
.. .. .
~`,,~ , , ~ '
0~r7~ 41
1 cribed above, i.e. since in general the emulsions are used
2 to treat aqueous solutions, a water-in-oil (that is, an emul-
3 sion wherein the internal phase is aqueous and the external
4 phase is oil) i8 prepared. This emulsion may be prepared
by means known in the art - for example, ~he aqueous phase
6 which m~y be a gulfuric acid solution having an acid con-
7 centration above 100 g/l is added over a period of tLme to
8 an agitated golution compriging an ion-exchange compound such
9 as LrX 64N tissolvet in a hydrocarbon oil - for example, an
o isoparaffin oil having a carbon number range of from C10 to
11 C60, and containing therein a surface-active agent for
12 example, polyamine derivative 2 set forth belowO After the
3 sulfuric acid solution is added, in an amount sufficient to
provide an emulsion, wherein the sulfuric acid solution makes
up approximately 50 weight percent of the total emulsion,
16 agitation i8 tiscontinuet. This stable emulsion may be con-
17 tacted wlth an aqueous solution containing dissolved copper
8 sulfate - for example, from 0.2 to 10 grams of salt per liter.
19 This copper sulfate solution should have a pH of at lea~t 1,
preferably at least 2 to 30 The aqueous solution and the
21 emulsion may be contacted by means known in the art - for
22 example, contacting in one or more extraction mixers or in
23 static mixers followed by settlers may be usedO For the pur-
24 poses of example, however, aqueous solutions and the emul-
2s sion are contacted in a batch operation. The emulsion, being
26 a water-in-oil emulsion, is not miscible with the aqueous
27 solution and thus, depending on the respective specific grav-
28 ity, will either float on the aqueous solution or the aqueou~
29 solution will float on ito Mild agitation is providet in
order to break up the emulsion into droplets which will be
, .. . .
. ., , ~
07 7'~ 41
1 dispersed by said agitation in said aqueous solutionO The
2 volume ratio of the aqueous solution to the emul~ion may vary
3 from 30/1 to 1/1, preferably 15/1 ~o 2/le The individual
4 droplets of the emulsion provide what has been termed a
"liquid membrane" - that is~ the external phase of the emul-
6 sion, i.e. the oil interfaces with the aqueous solutionO At
7 this interface, cupric ion i8 complexed with the ion-exchange
8 compound dissolved in the external phase to form an oilosolu-
9 ble complex. This soluble complex permeates through the ex-
0 ternsl phase to the interface of the internal phase and the
external phase of the emulsionO At this interface, because
12 of the low pH of the internal phase, the complex i8 nct
13 stsble and decomposes yielding the complexing agent and
l4 cupric ionO The cupric ion being ~oluble in the aqueous in-
t~rnal phase but not in the external phase of the emul~ion
16 will be dissolved thereinO The cupric ~on i8 thu~ trapped
l7 in the internal phase of the emNlsion. At the interface of
8 the internal phase and the external phase of the emul~ion,
19 the complexing agent will combine with a hydrogen ion, since
this form i8 favored in the presence of a high hydrogen ion
21 concentrationO The hydrogen ion contai~ing species will then
.
22 permeate back to the in~e~face of the external phase of ~he
23 emulsion and the aqueous solution where it is available for
24 further complexing with cupric ion present in the aqueous
solution. It may be thus seen from this description that
26 the external phase of the emulsion, iOeO the liquid membrane,
27 acts as a one-way transfer means for the cupric ion and a
28 countercurr~nt one-way transfer means for hydrogen ionO
29 Th~s it is possible, by means of the process of the instant
~ invention, to transfer ions ~ fcr example, metal ions such
- 10
, . .
~077Z41
l as copper - from an aqueous solution to the internal phase
2 of the emulsion even though the concentration of ~aid ion is
3 higher in the internal phase than in the aqueous solut~onO
4 This will thus overcome one of the limitations of the prior
art liquid membrane processesO
6 The reason for transfer of the complex through the
7 external phase of the emulsion, iOe. the liquid membrane, ~s
8 due to the concentration difference ln the external phase
9 itself. At the interface of the external phase of the emul-
sion and the aqueous solution there exists a high concentra-
11 tion of the complex of the ion~exchange com~ound and the
12 ion - for example, cupric ion, while at the interface of the
13 external phase of the emulsion and the internal phase where
14 due to high acidity, the complex i8 destroyed, there exists
a low concentration of the cupr~c icn ion-exchange compound
16 complex. At this interface, of course, the concentration of
17 the hydrogen ion combined with the ion-exchange compound will
18 be higher than at the interface of the aqueous solution and
19 the external phase of the emulsion. Due to t~is concentra-
tion difference, what occurs is a permeation of the cupric
21 ion combined with the ion~exchange compound from the aqueous
22 solution to the internal phase of the emulsion while the com-
23 plex of the hydrogen ion in the ion-exch~nge compound perme-
24 ates from the internal phase of the emulsion to the aqueous
solutionO It can thus be seen that the pH of the aq~eous
26 solution will continue to decrease~ due to an influx of hy-
27 drogen ions carried across the membrane from within the emul-
28 sion countercurrent to the copper ions being carried in
29 while the concentration of copper ion in the aqueous solu~
~ tion decreases. Fcr this reason, in this example, the pH of
1077Z41
1 the aqueous solution must be maintained above a certain
2 levelO This can be done by means known ~n the ~rt such as
3 adding a basic solution - for example, sodium hydroxide - to
4 the aqueous solution during the process or providing suffi-
cient basicity initially to promote the permeation of the
6 copper from the aqueous solution into the internal phase of
7 the emulsion. The internal phase of the emulsion, of course,
8 must be maintained at a pH wherein decomplexing occursO This
9 can be done merely by providing sufficient acid concentration
in the initial emulsion to provide a sufficiently low pH over
11 the course of removing the copper ion from the aqueous solu-
12 tion, so that the acid concentration never goes below50-lO0
13 g/l H2S04t
14 The process of the instant invention is specifi~
,.. .
cally applicable to remcval ¢f the metal ion from aqueous
16 waste streams as well as aqueous solutions, such as result
7 from hydrometallurgical operations. The p~rocess of the in~
18 gtant invention i~ especially applicable to the removal of
19 copper from dilute leach liqu~rs9 which are obtained by
treatment of copper containing minerals or mineral residues
21 with dilute aqueous acid, such as sulfuric acid.
22 The resultant leach liquor will contain cupric ion
23 in concentrations which may range from 0025 g/liter up to
24 lO g/liter or higherO This same liquor will~ of course, also
contain other dissolved ions such as iron, aluminum and mag-
26 nesium, as well as any unused acid. It will be necessary to
27 separate and concentrate the copper and tr~nsfer it into a
28 highly acid~c electrolysis solution with a minimum of inter-
2~ fering foreign metallic ions. Pure metallic copper is re~
~ covered from this liq~id by electrolysis.
.
.
' ' ' '' ' . '' ' ' '
0 77~Z41
l In the conventional solvent extraction process, the
2 leach liquor is contacted with a solution of an ion exchange
3 resin or complexing agent, such as LIX 64N in kerosene, in
4 one, but usually several, countercurrent mixer-settler stagea
s The cupric ion i~ thus extracted selectively down to the de-
6 sired low level by means of the organic solvent~ from which
7 it is stripped in a ~ubsequent operation by means of a highly
8 acidic stripping solution, usually the spent electrolyte from
9 the electrolysis operation. Copper concentration in this
lo liquor is 30-60 g/l, while acld may range from 1000200 g/l,
expressed as H2S04. The transfer of Cu from the dilute leach
l2 liquor at 0.25-10 g/l to the concentrated electrolysis solu~
l3 tion, wherein Cu concentr-tion is of the order cf 30-60 g/l,
l4 is made possible by the wide difference in acid aoncentration
15 between the tw~ aqueous solutions, namely about 0.2-0.5 g/l
16 acid in the leach liquor and ioo-200 g/l acid in the stripping ?
l7 801ution.
l8 However, one of the disadvantages of the conven~
l9 tional process is that, slnce the capacity of the organic
20 phase for copper ls relatlvely low (0.5~2 g/l of CUJ approx.)
2l very large quantities of solvent must be circulated, mixed,
22 settled ant stripped9 with a result~nt high inventory cost.
23 Also, the driving force for copper transfer ls rather small
24 between the two phases at any given stage, result~ng in high
2s contacting requlrements (i.e. strong agltatio~ and long mix-
26 ing time).
27 In the process of the lnstant invention, the strip-
28 p~ng solutlon (strongly acidic aqueous electrolyte, for ex-
29 ample) is lncorporated intc the extracting emulsion as the
internal aqueous droplet phase. It may have a copper con-
13 -
:
1077Z41
1 centration from 25-60 g/l and an acid concentration between
2 30 and 200 g/l, preferably between lO0 and 175 g H2S04/l. The
3 external emNlsion phase is a hydrocarbon phase incorporating
4 0.5-20% or more of LIX 64N, preferably 1-10% so as to accom-
plish the desired selective tran~fer of cupric ions from the
6 dilute leach liquar into the internal emulsion droplets.
7 The emulsion formulation may range from 0.3/l to
8 3.0/l wt./wt. oil/aqueous (i.e. external/internal) with a
9 range of 0.5/l - 2/l being preferred.
The emulsion is contacted with the leach liquor
11 in a single mixer-settler stage where the copper is extract-
12 ed out of the aqueous feed by means of the liquid membrane
13 emulsion. Since the "stripping solution" is incorporated in
14 the emulsion, the driving force for good copper removal from
the leach liquor is always present and the need for counter-
16 currency is obviated. Therefore, only a single settling
17 stage i8 required.
8 However, in order to maximize the rate of copper
19 extraction, it is preferable to subdivide the mixing reac-
tor into several co-current stages. This results in a de-
21 creasing copper concentration in the aqueous phase present
22 in the various stages, leading to improved extraction rates
23 compared to a single contacting stage. This is well-known
24 first order reaction technology, and copper extration by
liquid membranes appears to follow first order kinetics
26 reasonably well.
27 In the-instant invention, the ion exchange resin
28 or complexing agent is only used to transfer ions ~rom the
29 solution to the internal phase of the emulsion, thus much
less amounts are necessary than in the prior art solvent ex-
- ' :~. .
~ 0~7~ 41
1 traction processes wherein the ion exchange resin or the
2 complexing agent remains chemically tied (reacted) to the
3 ion. Thus, since the copper concentrat~on in the internal
4 phase of the emulsion can increase by 10-20 g Cu/l between
"fre~h" and "spent" emulsion, and the internal to external
6 ratio in the emul8ion may be 1/1 to 2/1, the copper capac-
7 ity of the emulsion will be 5-13 g/l, or up to 10-fold (or
8 more) of the capacity of the kerosene-LIX System. Also, the
9 copper driving force is always better, so that much smaller
o equipment and lower circulation are possibleO Finally, or-
ll ganic losses in the effluent treated leach liquor can be
l2 lower.
l3 In a typical installation, 57,000 gpm (gallons per
l4 minute) of leach liquor containing 0.5 g/l of Cu as well as
gtl quantities of Fe, Al, Mg ant other ions is treated as pH
l6 of 2.5 with only 4000 gpm of a liquid membrane emulsion in
l7 which the aqueous/oil phases are in the weight ratio of 2/1.
l8 The oil phase contains 5~/O LIX 64N, and the remai~der is a
l9 mixture of Clo-C40 hydrocarbons and a polyamine derivative
(see Example 1 below). The internal aqueous phase contains
21 165 g/l H2S04 and 30 g/l Cu. This copper concentration is
22 allowed to rise to 40 g/l as the copper concentration of the
23 treated leach liquor drops to 10% of the feed value, i.e.
24 0.05 g/l Cu.
The spent emulsion and treated leaçh liquor are
26 separated in a settler and the leach liquor is recycled to
27 the leaching operation. The spent e~ulsion is now processed
28 to recover the copper values concentrated therein.
29 This recovery can be achieved in a number of ways,
some of which are described below.
.,
. .,
~077241
1. Demulsification by treatment with emulsion-
breaking solvents, i.e. a mixture of an oil-soluble and
water-soluble solvent such as cyclohexane and isopropanol.
(See, for example. U.S. Patent 4,001,109 issued 4 January,
1977 of Li, Hucal and Cahn.)
2. Demulsification by physical means including
centrifugation and vigorous agitation with an aqueous phase.
3. Re-extraction of the contained copper from the
internal phase by means of an aqueous solution which is higher
in acid strength than the encapsulated internal aqueous phase.
4. Electrolysis of the emulsion dispersed in a
strongly acidified aqueous phase, which is acting both as
the electrolyte and as the stripping liquor similar to 3
above.
The aqueous internal phase separated out in either 1
or 2 above can be fed directly to electrolysis, where Cu is
removed to the desired level, and H2SO4 will build up to the
required concentration. This regenerates the internal solution
to the required level, at which point it is recombined with
the previously separated oil phase to form fresh emulsion for
recycle to the extraction step.
The emulsions after 3 or 4 above can be recycled
directly to the extraction step.
Other techniques for breaking the liquid membrane
emulsion include heat, passing the emulsion through a high
~_~
,
'
~077Z4~
shear zone in the presence of finely divided coalescing mate-
rial which wets the internal phase preferentially, as well as
the above-mentioned alternates.
The demulsification via centrifugation (see 2
:
- 16A -
.
.. -. . . , . ., . , - .
,. : ,' , . . .:
~077'~4~
above) may be carried out by first centrifuging the spent
2 emulsion to separate out a~ much of the external phase (oll)
3 as possible. The remaining thickened emulsion now has a
4 ratio of ll5 to l/10 or less oil!aqueous (i.e. external/in-
ternal) phase. It is then agitated with excess of a liquid
6 such as one containing the constituents of the internal
7 aqueous phase so that added liquid/emulsion are in a ratio of
8 above 4/l, preferably above 5/l, more preferably above lO/l,
9 in a high shear zone where this thick emulsion will break to
0 a sufficient degree to release a ma30r portion of its con-
1 tained internal aqueous phase. By appropriate recycling
12 through the centrifuge, the incoming emulsion can thus be
13 broken, and the internal phase treated (in the electrolytic
14 cell, for example) and recombined with the previously separ-
ated oil pha~e to form fresh emulsion for leach liquor treat-
16 ing, as previously described.
17 It is to be understood that other methods of demul-
18 sification, isuch as by passage through an intense electrical
19 field or by the addition of appropriate emulsion breaking
chemicals, may be utilized without detracting from the main
21 intent of the instant invention, namely the selective remov-
22 al of ionic spe~ies by means of ion exchange containing liq-~
23 uid membrane emulsions and the concomitant use of a second
24 ion as a "&iver".
In waste treatment processes, such as the removal
26 of trace quantities of metallic contaminants, the process of
27 the present invention can be very effectively utilized. By
28 the use of a selective ion exchange resin dissolved in the
29 external phase (oil), and by the inclusion of a high concen-
tration of driver i~n (H+, OH-, Cl, etc.) in the internal
~07 ~'~ 4~
1 aqueous droplet phase, emulsions can very effectively clean
2 up even small amounts of metallic impurities from dilute
3 effluents and concentrate these metallic materials selec-
4 tively in the internal phase of the emulsion. Concentration
differences of many thousand-fold between the solution and
6 internal aqueous phases can be maintained so that very low
7 levels (parts per billion) of metallic contaminants can be
8 reached in the waste water being treated while the emulsion
9 is being loaded to 8 considerable degree (several percent)
with the contaminant. Since the quantity of emulsion used
11 up often is very small, the emulsion can be burned or other-
12 wise disposed of at less expense than by going through one of
13 the previously described recovery techniquesO
14 Typical waste water contaminants which can be
lS handled by this technique are Hg, Co, Cr and, of course, Cu,
16 to name a few.
17 ExamPle l
8 Three runs were made uslng three different liquid
19 membrane compositions to show the effective removal of Cu++
from aqueous solutions by the process of the instant inven-
21 tion. The data are summarized in the following table.
22 In carrying out each of the three runs, a copper
23 stripping solution compri~ed of 170~/o H2S04 and 2.9% Cu++
24 was first emulsified in a hydrocarbon solvent, containing
dissolved therein a surfactant, said hydrocarbon solvent
26 thus forming the liquid membrane phase according to the pro-
27 cedure described previously. The emulsion was then mixed
28 with an aqueous solution of copper sulfate in a fluted
round-bottom vessel, which has a volume of 1500 cc and an
inside diameter of 4 in. (inches). The mixing was carried
- 18 -
1 07 7'~ ~1
1 out by using a stirrer having two marine~type propellers
2 each with three blades. The distance between the center of
3 the stirrer shaft and the blade tip measured 1 in. One
4 blade was mounted at the end of the stirrer shaft, the other
was 1 in. above the first. Both blades were pitched in the
6 same direction.
7 The mixing was stopped at 2, 5 and 10 minutes total
8 mi~ng time to enable samples to be taken from the feed phase
9 (aqueous solution of Cu++) for Cu analysis and pH measure-
ment. The results show that after 5 min. mixing the percent
11 of Cu removal by the liquid membrane emulsion was excellent -
12 ranging from 94 to 99%.
13 This example demonstrates the transfer of Cu from
14 a solution comprising ~0.05% Cu to a solution comprising
2.9% Cu by weight.
16 The physical properties of the three solvents used
17 in formulating the liquid membrane phase of the emulsion used
18 in the experiments are described below:
19 Flash
20 Carbon % Aro- Sp. Gr. Pt. Kin. Vis.
21 Solvent Number matics at 60F (F) (c.s.)
22 SlOON ~ 35 ~ 9 .865 380 22.6 (100F)
23 S600N ~ 40 ~22 .888 490 132 (100F)
24 Isopar M ~ 20 0.2 .784 170 3.14 (77F)
- 19 -
~77Z41
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- 21 -
~077Z41
1 ExamPle 2
2 A run was made to show the rapid removal of
3 Cd(CN)4-2 from its aqueous solution. The run consisted of
4 three cycles. In each cycle, fresh feed containing Ct(CN)4-2
was used; however, the liquid membrane emulsion used was the
6 same for all three cycles. The purpose of making three cy-
7 cles was to show the reusability of the emulsion.
8 The equipment employed was the same as de~cribed
g in Example 1. The liquid membrane emulsion consisted of an
lo internal phase (Cd(CN)4-2 stripping solution) and a membrane
11 phase. The internal phase was a 3% HN03 in water, and the --
12 membrane phase contained Aliquat 336, the polyamine deriva-
13 tive of Example 1, tributyl phosphate, Isopar~M, and SlOON
14 with their respective concentrations indicated in the follow-
ing table. Aliquat~336 is a product from General Mills. It
16 is an ion exchange compound, a quaternary amine, R3NCH3Cl,
17 where R is a mixture of C8 and C10 carbon chains with the C8
18 predominating. Tributyl phosphate was used here as a co-
19 901vent to help dissolve Aliquat~in SlOON. The aqueous feed
containing Cd(CN)4-2 was made by dissolving CdC12 and NaCN
21 in water.
22 The results summarized in the table show excellent
23 separation of Cd(CN)4-2 from its aqueous solution by the
24 liquid membrane emulsion. The percent of Cd removed after 5
min. mixing in all three cycles ranges from 99.7 to 99.9~.
26 This example demonstrates the transfer of a metal
27 in an anionic form through the liquid membrane into the in-
28 ternal phase.
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- 22 -
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- 23 -
1077Z41
1 ExamPle 3
f~ 2 An emulsion comprising an external phase of 15%
~'J 3 Active LIX 64N, 2X polyamine derivative 2, 83% Isopar~M, and
4 an internal phase of 17.770 CuS04-5H20, 5.7% H2S04 and 76.6%
H20 with an external/internal phase weight rat~o of 2:1 was
6 centrifuged at 4000 rpm for 30 minutes to re ve about 90%
7 of the external phase. The remaining emulsion became a
8 viscous gel. The gel was mixed with an aqueous solution of
9 CuS04 (12.5%) and H2S04 (11.7%) in a Waring blender for 4
minutes at 15,000 rpm. A weight ratio of added liquid to
ll gel of lO:l produced substantial demulsification.
a~e ~a~
- 24 - -
: - -
