U.S. patent application number 14/401467 was filed with the patent office on 2015-05-14 for method for recovering a metal from solution, system for recovering a metal from solution, and system for recovering lithium from salt water.
This patent application is currently assigned to SNU R&DB FOUNDATION. The applicant listed for this patent is SNU R&DB FOUNDATION. Invention is credited to Choon-Soo Kim, Jaw-Han Lee, Je-Yong Yoon.
Application Number | 20150129433 14/401467 |
Document ID | / |
Family ID | 49583919 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150129433 |
Kind Code |
A1 |
Yoon; Je-Yong ; et
al. |
May 14, 2015 |
METHOD FOR RECOVERING A METAL FROM SOLUTION, SYSTEM FOR RECOVERING
A METAL FROM SOLUTION, AND SYSTEM FOR RECOVERING LITHIUM FROM SALT
WATER
Abstract
In a method for recovering a metal from a solution, a first
electrode that includes a metal for recovery and a second electrode
that includes a metal different from the metal for recovery are
prepared. The first electrode and the second electrode are immersed
in a first solution that includes a metal ion for recovery. The
metal ion for recovery in the first solution is combined with the
first electrode. The first electrode and the second electrode are
charged while immersing the first and second electrodes in a second
solution different from the first solution so that the metal ion
for recovery is separated from the first electrode. The metal for
recovery is recovered from the second solution.
Inventors: |
Yoon; Je-Yong; (Seoul,
KR) ; Lee; Jaw-Han; (Seoul, KR) ; Kim;
Choon-Soo; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SNU R&DB FOUNDATION |
Seoul |
|
KR |
|
|
Assignee: |
SNU R&DB FOUNDATION
Seoul
KR
|
Family ID: |
49583919 |
Appl. No.: |
14/401467 |
Filed: |
January 17, 2013 |
PCT Filed: |
January 17, 2013 |
PCT NO: |
PCT/KR2013/000353 |
371 Date: |
November 14, 2014 |
Current U.S.
Class: |
205/771 ;
204/242 |
Current CPC
Class: |
C25C 7/02 20130101; C25C
1/02 20130101; C25C 1/22 20130101; C22B 26/12 20130101 |
Class at
Publication: |
205/771 ;
204/242 |
International
Class: |
C25C 1/22 20060101
C25C001/22; C25C 7/02 20060101 C25C007/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2012 |
KR |
10-2012-0051834 |
Claims
1. A method for recovering a metal from a solution, comprising:
preparing a first electrode that includes a metal for recovery and
a second electrode that includes a metal different from the metal
for recovery; immersing the first electrode and the second
electrode in a first solution that includes a metal ion for
recovery; combining the metal ion for recovery in the first
solution with the first electrode; charging the first electrode and
the second electrode while immersing the first and second
electrodes in a second solution different from the first solution
so that the metal ion for recovery is separated from the first
electrode; and recovering the metal for recovery from the second
solution.
2. The method of claim 1, wherein combining the metal ion for
recovery in the first solution with the first electrode includes:
electrically connecting the first electrode and the second
electrode which are positively and negatively charged,
respectively, to induce a discharge.
3. The method of claim 1, wherein the metal for recovery includes
lithium, the first electrode includes a lithium manganese oxide,
and the second electrode includes at least one selected from the
group consisting of silver, zinc, copper and mercury.
4. A system for recovering a metal from solution, comprising: a
first electrode including a first metal, the first electrode being
discharged in a first solution that includes a first metal ion to
be combined with the first metal ion and being charged in a second
solution different from the first solution to release the first
metal ion; a second electrode including a second metal different
from the first metal, the second electrode being discharged in the
first solution to be combined with a first anion of the first
solution and being charged in the second solution to release the
first anion; and a power source for charging the first and second
electrodes.
5. The system of claim 4, wherein the first electrode includes a
lithium manganese oxide, and the second electrode includes at least
one selected from the group consisting of silver, zinc, copper and
mercury.
6. The system of claim 5, wherein the first electrode includes
LiMn.sub.2O.sub.4 having a spinel phase.
7. The system of claim 5, wherein the first electrode further
includes a carbon electrode, and the lithium manganese oxide is
coated on a surface of the carbon electrode.
8. The system of claim 4, further comprising a battery capable of
repeating charge and discharge processes, wherein an electric
energy generated when the first and second electrodes are
discharged is stored in the battery, and the battery is connected
to the power source to provide the stored electric energy.
9. A system for recovering lithium from a salt water, comprising: a
first electrode including a lithium manganese oxide, the first
electrode being discharged in a salt water that includes a lithium
ion and a chlorine ion to be combined with the lithium ion and
being charged in a charging solution different from the salt water
to release the lithium ion; a second electrode including silver,
the second electrode being discharged in the salt water to be
combined with the chlorine ion and being charged in the charging
solution to release the chlorine ion; a power source for charging
the first and second electrodes; and a battery capable of repeating
charge and discharge processes, the battery storing an electric
energy generated when the first electrode is discharged and being
connected to the power source to provide the stored electric
energy.
10. The system of claim 9, wherein the first electrode includes
LiMn.sub.2O.sub.4 having a spinel phase.
Description
BACKGROUND
[0001] 1. Field
[0002] Example embodiments of the present invention relate to
methods and systems for recovering a metal. More particularly,
example embodiments of the present invention relate to methods for
recovering a metal from solution, systems for recovering a metal
from solution, and systems for recovering lithium from salt
water.
[0003] 2. Description of the Related Art
[0004] Lithium (Li) is widely utilized in various industries such
as glasses, ceramics, alloys, lubricating oils, pharmaceutics, etc.
Particularly, a lithium secondary battery has been recently
highlighted and developed for a power supply of a hybrid vehicle
and an electric vehicle. A demand for the lithium secondary battery
is expected to surge up to about 100 times a demand in a compact
battery market for, e.g., a cell phone, a laptop computer, etc.
[0005] Further, a demand for lithium may be increased drastically
as global environmental restrictions are becoming strengthened, and
an application of lithium may be expanded to various industries of
21.sup.st century including electronic, chemical and energy
industries as well as the hybrid and electric vehicles
industry.
[0006] A source of lithium may include a mineral, a brine or a sea
water. The mineral may include spodumene, petalite and lepidolite
which contain a relatively large amount of lithium in a range of
about 1% to about 1.5%. However, an extraction of lithium from the
mineral may require many complex processes such as a floatation, an
annealing, a grinding, an acid mixing, an extraction, a
purification, an concentration, a precipitation, etc., and thus
large cost and energy may be spent during the processes. Further,
an environmental pollution may be caused by an acid used in the
extraction of lithium.
[0007] When lithium is recovered from the sea water, a recovery
device including an adsorbent may be introduced into the sea water
so that lithium may be selectively adsorbed, and then lithium may
be recovered by an acid treatment. However, a concentration of
lithium in the sea water is as small as about 0.17 ppm, and thus
the recovery from the sea water may be limited from an economical
aspect.
[0008] Considering the above problems, lithium is mainly recovered
from the brine. For example, a salt lake is used as a crude source
of lithium, and other salts including Mg, Ca, B, Na or K co-exist
therein together with lithium.
[0009] A concentration of lithium in the brine may range from about
0.3 g/L to about 1.5 g/L, and lithium in the brine may be extracted
as a form of lithium carbonate. A solubility of lithium carbonate
may be about 13 g/L. Even though lithium in the brine is assumed to
be completely converted into lithium carbonate, a concentration of
lithium carbonate in the brine may range from about 1.59 g/L to
about 7.95 g/L which is smaller than the solubility of lithium
carbonate. Thus, precipitated lithium carbonate may be re-dissolved
thereby to reduce a recovery ratio of lithium.
[0010] Accordingly, a conventional method for recovering lithium in
the brine as the form of lithium carbonate includes pumping the
brine from a natural salt lake and storing in an evaporation pond,
naturally vaporizing the brine for a long period more than a year
to concentrate lithium as great as several ten times, and removing
impurities such as Mg, Ca or B by a precipitation so that lithium
may be recovered at an amount greater than the solubility of
lithium carbonate.
[0011] However, the conventional method requires much time for the
vaporization and the concentration of the brine to reduce an
overall productivity. Further, lithium may be precipitated together
with the impurities during the vaporization and the concentration
steps to cause a loss of lithium, and the method is limited in a
rainy season.
SUMMARY
[0012] Example embodiments of the present invention provide a
method for efficiently recovering various metals from a
solution.
[0013] Example embodiments of the present invention provide a
system for recovering various metals from a solution.
[0014] Example embodiments of the present invention provide a
system for recovering various metals such as lithium from a salt
water.
[0015] According to an aspect of the present inventive concepts,
there is provided a method for recovering a metal from a solution.
In the method, a first electrode that includes a metal for recovery
and a second electrode that includes a metal different from the
metal for recovery are prepared. The first electrode and the second
electrode are immersed in a first solution that includes a metal
ion for recovery. The metal ion for recovery in the first solution
is combined with the first electrode. The first electrode and the
second electrode are charged while immersing the first and second
electrodes in a second solution different from the first solution
so that the metal ion for recovery is separated from the first
electrode. The metal for recovery is recovered from the second
solution.
[0016] In example embodiments, in combining the metal ion for
recovery in the first solution with the first electrode, the first
electrode and the second electrode which are positively and
negatively charged, respectively, may be electrically connected to
induce a discharge.
[0017] In example embodiments, the metal for recovery may include
lithium, the first electrode may include a lithium manganese oxide,
and the second electrode may include silver, zinc, copper and/or
mercury.
[0018] According to an aspect of the present inventive concepts,
there is provided a system for recovering a metal from a solution.
The system includes a first electrode including a first metal, a
second electrode including a second metal different from the first
metal, and a power source for charging the first and second
electrodes. The first electrode is discharged in a first solution
that includes a first metal ion to be combined with the first metal
ion and is charged in a second solution different from the first
solution to release the first metal ion. The second electrode is
discharged in the first solution to be combined with a first anion
of the first solution and is charged in the second solution to
release the first anion.
[0019] In example embodiments, the first electrode may include a
lithium manganese oxide, and the second electrode may include
silver, zinc, copper and/or mercury.
[0020] In example embodiments, the first electrode may include
LiMn.sub.2O.sub.4 having a spinel phase.
[0021] In example embodiments, the first electrode may further
include a carbon electrode, and the lithium manganese oxide may be
coated on a surface of the carbon electrode.
[0022] In example embodiments, the system may further include a
battery capable of repeating charge and discharge processes. An
electric energy generated when the first and second electrodes are
discharged may be stored in the battery, and the battery may be
connected to the power source to provide the stored electric
energy.
[0023] According to an aspect of the present inventive concepts,
there is provided a system for recovering lithium from a salt
water. The system includes a first electrode including a lithium
manganese oxide, a second electrode including silver, a power
source for charging the first and second electrodes, and a battery
capable of repeating charge and discharge processes. The first
electrode is discharged in a salt water that includes a lithium ion
and a chlorine ion to be combined with the lithium ion and is
charged in a charging solution different from the salt water to
release the lithium ion. The second electrode is discharged in the
salt water to be combined with the chlorine ion and is charged in
the charging solution to release the chlorine ion. The battery
stores an electric energy generated when the first electrode is
discharged and is connected to the power source to provide the
stored electric energy.
[0024] In example embodiments, the first electrode may include
LiMn.sub.2O.sub.4 having a spinel phase.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Example embodiments will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings.
[0026] FIG. 1 is a flow chart illustrating a method for recovering
a metal from a solution in accordance with example embodiments;
[0027] FIGS. 2 and 3 are schematic views illustrating a system for
recovering a metal from a solution in accordance with example
embodiments;
[0028] FIG. 4 is a graph showing concentration changes of a lithium
ion and a sodium ion present in a discharging solution while
repeating charge and discharge processes in a lithium recovery
process of Example 1;
[0029] FIG. 5 is a graph showing concentration changes of a lithium
ion, a calcium ion, a potassium ion, a magnesium ion and a sodium
ion present in a discharging solution while repeating charge and
discharge processes in a lithium recovery process of Example 2;
and
[0030] FIG. 6 is a graph showing a concentration change of a
lithium ion present in a charging solution while repeating charge
and discharge processes in a lithium recovery process of Example
2.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0031] Various exemplary embodiments will be described more fully,
in which some exemplary embodiments are shown. The present
inventive concept may, however, be embodied in many different forms
and should not be construed as limited to the exemplary embodiments
set forth herein. Rather, these exemplary embodiments are provided
so that this description will be thorough and complete, and will
fully convey the scope of the present inventive concept to those
skilled in the art.
[0032] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting of the present inventive concept. As used herein, the
singular forms "a," "an" and "the" are intended to include the
plural forms as well, unless the context clearly indicates
otherwise. It will be further understood that the terms "comprises"
and/or "comprising," when used in this specification, specify the
presence of stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements,
components, and/or groups thereof.
[0033] Example embodiments are described herein with reference to
cross-sectional illustrations that are schematic illustrations of
idealized example embodiments (and intermediate structures). As
such, variations from the shapes of the illustrations as a result,
for example, of manufacturing techniques and/or tolerances, are to
be expected. Thus, example embodiments should not be construed as
limited to the particular shapes of regions illustrated herein but
are to include deviations in shapes that result, for example, from
manufacturing. For example, an implanted region illustrated as a
rectangle will, typically, have rounded or curved features and/or a
gradient of implant concentration at its edges rather than a binary
change from implanted to non-implanted region. Likewise, a buried
region formed by implantation may result in some implantation in
the region between the buried region and the surface through which
the implantation takes place. Thus, the regions illustrated in the
figures are schematic in nature and their shapes are not intended
to illustrate the actual shape of a region of a device and are not
intended to limit the scope of the present inventive concept.
[0034] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
inventive concept belongs. It will be further understood that
terms, such as those defined in commonly used dictionaries, should
be interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
Methods for Recovering a Metal from a Solution
[0035] FIG. 1 is a flow chart illustrating a method for recovering
a metal from a solution in accordance with example embodiments.
[0036] Referring to FIG. 1, in step S10, a first electrode and a
second electrode may be immersed in a first solution containing a
metal ion for recovery, and the metal ion in the first solution may
be combined with the first electrode. In example embodiments, the
first electrode and the second electrode may be positively and
negatively charged, respectively, and the first and second
electrodes may be electrically connected to cause a discharge so
that the metal ion for recovery in the first solution may be
combined with the first electrode.
[0037] Preferably, before electrically connecting the first and
second electrodes, the first electrode may be positively charged
and the second electrode may be negatively charged.
[0038] A metal for recovery may not be specifically limited,
however, may include, e.g., lithium, sodium, potassium, magnesium,
calcium, strontium, manganese, etc.
[0039] The first solution may be obtained, e.g., a sea water or a
highly concentrated brine (or a salt water). The first solution may
further include other metal ions and anions in addition to the
metal ion for recovery. For example, if the metal for recovery is
lithium, the first solution may include cations of lithium, sodium,
potassium, magnesium, calcium, strontium, manganese, etc., and a
chlorine anion (Cl.sup.-).
[0040] The first electrode may include the metal for recovery. For
example, if the metal for recovery is lithium, the first electrode
may also include lithium. Preferably, the first electrode may have
a selectivity for the metal for recovery. For example, if the metal
for recovery is lithium, the first electrode may include a lithium
manganese oxide (LMO). Specifically, the LMO may include
LiMn.sub.2O.sub.4, LiMnO.sub.6, etc., and these may be used alone
or in a combination thereof. The selectivity for a lithium ion of
the LMO may vary according to a phase of the LMO. Preferably, the
LMO may have a spinel phase.
[0041] Preferably, the second electrode may include a metal
different from the metal for recovery. Further, the metal of the
second electrode may have an ionization tendency greater than that
of the metal for recovery. Thus, when the first and second
electrodes are electrically connected to each other, the first
electrode may serve as an anode (positive electrode) and the second
electrode may serve as a cathode (negative electrode). Preferably,
the metal of the second electrode may be selected in consideration
of the ionization tendency of the metal for recovery, for example,
may include silver, zinc, copper, mercury, etc. The second
electrode may preferably include the metal that may be combined
with and separated from an anion reversibly and repeatedly in
charge and discharge processes. Thus, silver may be used as the
metal of the second electrode in consideration of the reversibility
and an environmental aspect.
[0042] When the first and second electrodes are electrically
connected to each other, the discharge may occur. In the discharge,
electrons may be moved from the first electrode to the second
electrode. The metal ion for recovery in the first solution may
accept the electron to be combined with the first electrode, and
the metal of the second electrode may lose the electron to be
combined with an anion in the first solution. In an embodiment, the
first electrode may include LiMn.sub.2O.sub.4, the second electrode
may include silver, and the first solution may include the lithium
cation and the chlorine anion. In this case, a reaction represented
by Chemical Equation 1 may occur in the first electrode, and a
reaction represented by Chemical Equation 2 may occur in the second
electrode.
[Chemical Equation 1]
Li.sub.i-xMn.sub.2O.sub.4+xLi++xe.sup.-.fwdarw.LiMn.sub.2O.sub.4
[Chemical Equation 2]
xAg+xCl.sup.-.fwdarw.xAgCl+xe.sup.-
[0043] As indicated in the above equations, the lithium ion in the
first solution may be combined with the LMO of the first electrode,
and the chlorine ion in the first solution may be combined with
silver of the second electrode to generate silver chloride. As a
result, concentrations of the lithium and chlorine ions in the
first solution may be reduced.
[0044] In example embodiments, the LMO included in the first
electrode may have the selectivity for lithium, and thus lithium
may be selectively separated from the first solution containing the
different metal ions.
[0045] In example embodiments, the positively charged first
electrode and the negatively charged second electrode may be
electrically connected to each other for discharging the first and
second electrodes. However, alternatively, a power source may be
connected to the first and second electrodes, the first electrode
may be negatively charged (electrons may be provided), and the
second electrode may be positively charged so that the lithium ion
in the first solution may be combined with the first electrode.
[0046] Subsequently, in step S20, the first and second electrodes
may be immersed in a second solution different from the first
solution and may be charged so that the metal ion for recovery may
be separated from the first electrode. The second solution may be
an aqueous solution including suitable electrolytes.
[0047] In a case that the first electrode includes
LiMn.sub.2O.sub.4 and the second electrode includes silver
chloride, the first and second electrodes may be charged such that
the first electrode may be positively charged and the second
electrode may be negatively charged to cause a reaction represented
by Chemical Equation 3 in the first electrode and a reaction
represented by Chemical Equation 4 in the second electrode.
[Chemical Equation 3]
LiMn.sub.2O.sub.4.fwdarw.Li.sub.i-xMn.sub.2O.sub.4+xLi++xe.sup.-
[Chemical Equation 4]
xAgCl+xe.sup.-.fwdarw.xAg+xCl.sup.-
[0048] As a result, the LMO of the first electrode may lose the
lithium ion, and silver chloride of the second electrode may lose
the chlorine ion to be reduced into silver. Accordingly, the second
solution may include the lithium cation and the chlorine anion.
[0049] Subsequently, in step S30, the metal for recovery may be
recovered from the second solution. Various conventional methods
may be implemented for recovering the metal.
[0050] For example, when the second solution includes the lithium
cation and the chlorine anion, the second solution may be heated to
obtain a solid-state lithium chloride. Lithium chloride may be
non-toxic and chemically stable, and thus easily stored and
managed. Additionally, lithium chloride may be directly used as an
electrolyte of a lithium secondary battery.
[0051] In other examples, the second solution including the lithium
cation and the chlorine anion may be treated by an electrolysis to
collect lithium.
[0052] Before recovering the metal, the discharge process in the
first solution and the charge process in the second solution
described above may be repeated so that a concentration of the
metal for recovery in the second solution may be increased. The
first electrode may be positively charged and the second electrode
may be negatively charged by the charge process in the second
solution. The first and second electrodes may be taken out from the
second solution, and immersed and electrically connected to each
other again in the first solution so that the lithium ion in the
first solution may be combined again with the first electrode by
the discharge process. If the concentration of the metal for
recovery in the second direction becomes increased, a recovery
efficiency of the metal may be improved.
[0053] According to example embodiments of the present invention, a
metal may be efficiently recovered from a solution. Specifically,
highly concentrated lithium may be obtained in a short time
compared to conventional methods using vaporization/concentration
of brine and adsorption from a sea water. Further, the method in
accordance with example embodiments may include simple processes
and may be relatively free from an environmental pollution.
Additionally, an electric energy generated from the discharge
process may be stored and reused to minimize an energy
consumption.
[0054] The method in accordance with example embodiments may be
used for recovering a metal from a sea water or a highly
concentrated brine, and may be also used for recovering a metal
from an industrial wastewater.
[0055] Hereinafter, a system for implementing the method for
recovering a metal from a solution, and a system for recovering
lithium from a brine are described in detail with reference to
accompanying drawings.
Systems for Recovering a Metal from a Solution and Systems for
Recovering Lithium from a Brine
[0056] A system for recovering a metal from a solution according to
example embodiments may comprise a first electrode including a
first metal and a second electrode including a second metal
different from the first metal. The first and second electrodes may
be electrically connected to each other. The first electrode may be
discharged in a first solution including a first metal ion to be
combined with the first metal ion, and may be charged in a second
solution different from the first solution to release the first
metal ion. The second electrode may be discharged in the first
solution to be combined with a first anion of the first solution,
and may be charged in the second solution to release the first
anion. The system may include a power source for charging the first
and second electrodes.
[0057] FIGS. 2 and 3 are schematic views illustrating a system for
recovering a metal from a solution in accordance with example
embodiments.
[0058] Referring to FIG. 2, a first solution 30 may be accommodated
in a first bath 40. A first electrode 10 and a second electrode 20
may be immersed in the first solution 30. For example, the first
electrode 10 and the second electrode 20 may be partially immersed
in the first solution 30 such that upper portions thereof may be
exposed from the first solution 30. In some embodiments, the first
and second electrodes 10 and 20 may be entirely immersed in the
first solution 30.
[0059] The first solution 30 may include a metal ion for recovery.
In example embodiments, a metal for recovery may be lithium. The
first solution 30 may be a sea water or a highly concentrated brine
(or salt water), and may further include sodium, potassium,
magnesium, calcium, strontium, manganese, etc., in addition to
lithium. The first solution 30 may also include an anion. If the
first solution 30 is the sea water or the highly concentrated
brine, the first solution may mainly include a chlorine anion
(Cl.sup.-).
[0060] The first electrode 10 may include the metal for recovery.
For example, if the metal for recovery is lithium, the first
electrode 10 may also include lithium. Preferably, the first
electrode 10 may have a selectivity for the metal for recovery. For
example, if the metal for recovery is lithium, the first electrode
10 may include a lithium manganese oxide (LMO). Specifically, the
LMO may include LiMn.sub.2O.sub.4, LiMnO.sub.6, etc., and these may
be used alone or in a combination thereof The selectivity for a
lithium ion of the LMO may vary according to a phase of the LMO.
Preferably, the LMO may have a spinel phase.
[0061] The LMO may have a relatively low conductivity. Thus, the
first electrode 10 may further include an additional material
having a relatively strong conductivity. For example, the first
electrode 10 may include a carbon electrode containing graphite,
carbon nanotube, graphene, etc., and the LMO may be at least
partially coated on a surface of the carbon electrode. A wire for
electrically connecting the first electrode 10 and the second
electrode 20 may be connected to the carbon electrode.
[0062] Specifically, the first electrode 10 may include a mixture
of powders of the LMO and graphite, and the mixture may be at least
partially coated on the surface of the carbon electrode. For
example, a positive electrode material composition including the
LMO, the powder of graphite, a binding agent and a solvent may be
coated on the carbon electrode, and dried to obtain the first
electrode 10. For example, the binding agent may include
polyvinyliden fluoride (PVDF), polyvinyl alcohol (PVA),
polyurethane (PU), etc. These may be used alone or in a combination
thereof. For example, the solvent may include an alcohol such as
methanol, ethanol, propanol, butanol, etc. These may be used alone
or in a combination thereof.
[0063] The second electrode 20 may include a metal different from
the metal for recovery. Further, the metal of the second electrode
20 may have an ionization tendency greater than that of the metal
for recovery. Thus, when the first and second electrodes 10 and 20
are electrically connected to each other, the first electrode 10
and the second electrode 20 may serve as an anode and a cathode,
respectively. Preferably, the metal of the second electrode 20 may
include silver, zinc, copper, mercury, etc. In example embodiments,
the second electrode 20 may include silver.
[0064] The first and second electrodes 10 and 20 may be
electrically connected to each other through the wire for a
discharge process. Preferably, before electrically connecting the
first and second electrodes 10 and 20, the first electrode 10 may
be positively charged, and the second electrode 20 may be
negatively charged to result in the discharge process of the first
and second electrodes 10 and 20.
[0065] In example embodiments, the first electrode 10 may include
LiMn.sub.2O.sub.4, the second electrode 20 may include silver, and
the first solution 30 may include the lithium cation and the
chlorine anion. Therefore, when the first and second electrodes 10
and 20 are electrically connected to each other, the lithium cation
of the first solution 30 may be combined with the LMO of the first
electrode 10, and the chlorine anion of the first solution 30 may
be combined with silver of the second electrode 20 to generate
silver chloride. As a result, concentrations of the lithium and
chorine ions may be reduced in the first solution 30.
[0066] The first and second electrodes 10 and 20 may be connected
to a battery 50. An electric energy generated from the discharge
process may be stored in the battery 50. The battery 50 may be also
used as a power source in a charge process described below. The
battery 50 may include any conventional battery capable of
repeating charge and discharge processes of an electric energy. For
example, a lead storage battery, a mercury battery, a lithium ion
battery, a lithium polymer battery, etc., may be used as the
battery 50.
[0067] Referring to FIG. 3, the first and second electrodes 10 and
20 after the discharge process may be immersed in a second solution
60 accommodated in a second bath 70.
[0068] When the first and second electrodes 10 and 20 are
positively and negatively charged, respectively, by charging the
first and second electrodes 10 and 20, the LMO of the first
electrode 10 may lose the lithium ion and silver chloride of the
second electrode 20 may lose the chlorine ion to be reduced into
silver. Accordingly, the second solution 60 may include the lithium
cation and the chlorine anion.
[0069] The first and second electrodes 10 and 20 may be connected
to a suitable power source for charging the first and second
electrode 10 and 20. The power source may be connected to the
battery 50, and the electric energy stored in the battery may be
utilized so that an energy efficiency may be improved.
[0070] By repeating the charge and discharge processes illustrated
in FIGS. 2 and 3, a highly concentrated lithium ion may be
achieved, and lithium may be recovered as a form of, e.g., a
lithium salt from the lithium ion solution.
[0071] In example embodiments, the first and second bath 40 and 70
may be separated from each other. However, the discharge process
may be performed in the first solution, and then the first solution
may be replaced with the second solution to perform the charge
process continuously in a single container.
[0072] According to example embodiments, highly concentrated
lithium may be obtained in a short time compared to conventional
methods using vaporization/concentration of brine and adsorption
from a sea water. Further, the method or the system in accordance
with example embodiments may include simple processes and may be
relatively free from an environmental pollution. Additionally, an
electric energy generated from the discharge process may be stored
and reused to minimize an energy consumption.
[0073] Hereinafter, a method for recovering a metal from a
solution, a system for implementing the method, and a system for
recovering lithium from a brine are described in detail with
reference to specific Examples.
EXAMPLE 1
[0074] A silver electrode of 3.times.3 cm.sup.2, and a graphite
electrode of the same size were prepared. A powder of
LiMn.sub.2O.sub.4, Super-P (manufactured by Timcal, Swiss) as a
graphite powder, and PVDF as a binder resin were mixed in a mixing
ratio of about 80:10:8 to form a mixture. The mixture was dispersed
in ethanol, coated on the graphite electrode and dried to prepare
an electrode for lithium recovery.
[0075] The electrode for lithium recovery and the silver electrode
were immersed with a distance of about 1 cm therebetween in a
charging solution of about 90 ml including lithium chloride of
about 25 mM. A power source was connected to the electrodes to
provide a charging voltage of about 1.2 V for about 20 minutes.
Accordingly, the electrode for lithium recovery was positively
charged, and the silver electrode was negatively charged.
[0076] Subsequently, the electrode for lithium recovery and the
silver electrode were immersed in a discharging solution of about
90 ml including lithium chloride of about 25 mM and sodium chloride
of about 25 mM. The electrode for lithium recovery and the silver
electrode were connected through a wire to be discharged for about
30 minutes.
[0077] The charge and discharge processes were repeatedly performed
three times. On completion of each cycle (including one charge
process and one discharge process), a sample of about 1 ml was
extracted from the discharging solution, and concentration changes
of lithium and sodium ions were measured using a ion-chromatography
apparatus, DX-120 (manufactured by DIONEX). The results are shown
in FIG. 4.
EXAMPLE 2
[0078] A silver electrode of 3.times.3 cm.sup.2, and a graphite
electrode of the same size were prepared. A powder of
LiMn.sub.2O.sub.4, Super-P (manufactured by Timcal, Swiss) as a
graphite powder, and PVDF (weight average molecular
weight:.about.534,000, glass transition temperature: -38.degree.
C., density at 25.degree. C.: 1.74 g/ml, manufactured by Sigma
Aldrich, USA) as a binder resin were mixed in a mixing ratio of
about 80:10:8 to form a mixture. The mixture was dispersed in
ethanol, coated on the graphite electrode and dried to prepare an
electrode for lithium recovery.
[0079] The electrode for lithium recovery and the silver electrode
were immersed with a distance of about 1 cm therebetween in a
charging solution of about 80 ml including lithium chloride of
about 30 mM. A power source was connected to the electrodes to
provide a charging voltage of about 1.2 V for about 20 minutes.
Accordingly, the electrode for lithium recovery was positively
charged, and the silver electrode was negatively charged.
[0080] Subsequently, the electrode for lithium recovery and the
silver electrode were immersed in a discharging solution of about
80 ml including lithium chloride of about 30 mM, sodium chloride of
about 30 mM, potassium chloride of about 30 mM and magnesium
chloride of about 30 mM. The electrode for lithium recovery and the
silver electrode were connected through a wire to be discharged for
about 40 minutes.
[0081] The charge and discharge processes were repeatedly performed
four times. On completion of each cycle (including one charge
process and one discharge process), a sample of about 1 ml was
extracted from the discharging solution, and concentration changes
of lithium, potassium, calcium, magnesium and sodium ions were
measured using a ion-chromatography apparatus, DX-120 (manufactured
by DIONEX). The same amount of a sample was extracted from the
charging solution, and a concentration change of a lithium ion was
measured. The results are shown in FIGS. 5 and 6.
[0082] FIG. 4 is a graph showing concentration changes of the
lithium ion and the sodium ion present in the discharging solution
while repeating the charge and discharge processes in Example 1.
FIG. 5 is a graph showing concentration changes of the lithium ion,
the calcium ion, the potassium ion, the magnesium ion and the
sodium ion present in the discharging solution while repeating the
charge and discharge processes in Example 2. FIG. 6 is a graph
showing a concentration change of the lithium ion present in the
charging solution while repeating the charge and discharge
processes in Example 2.
[0083] Referring to FIG. 4, the concentration of the lithium ion
was continuously decreased while repeating the charge and discharge
processes in Example 1, however, the concentration of the sodium
ion was substantially maintained without a reduction. Therefore, it
can be acknowledged that the lithium ion may be selectively
recovered from a mixture with the sodium ion using the method and
the system for recovering a metal from a solution according to
example embodiments.
[0084] Referring to FIG. 5, the concentration of the lithium ion
was continuously decreased while repeating the charge and discharge
processes in Example 2, however, the concentrations of the calcium
ion, the potassium ion and the sodium ion were substantially
maintained without a reduction. The concentration of the magnesium
ion was decreased in a first cycle, and then substantially
maintained without a reduction in the subsequent cycles. Referring
to FIG. 6, the concentration of the lithium ion was continuously
increased in the charging solution while repeating the charge and
discharge processes. Therefore, it can be acknowledged that the
lithium ion may be selectively recovered from a mixture with the
sodium ion, the potassium ion, the calcium ion and the magnesium
ion using the method and the system for recovering a metal from a
solution according to example embodiments.
[0085] The sodium and magnesium ions are significantly present in
the sea water and the highly concentrated brine which may be
sources of lithium. Particularly, magnesium may have a solubility
similar to that of lithium, and thus may not be easily separated by
a vaporization method. The presence of these ions may be a main
factor reducing an efficiency in a lithium recovery process.
Therefore, the method and the system for recovering a metal from a
solution according to example embodiments may be implemented to
efficiently recover lithium from the sea water and the highly
concentrated brine.
[0086] The foregoing is illustrative of example embodiments and is
not to be construed as limiting thereof. Although a few example
embodiments have been described, those skilled in the art will
readily appreciate that many modifications are possible in the
example embodiments without materially departing from the novel
teachings and advantages of the present inventive concept.
Accordingly, all such modifications are intended to be included
within the scope of the present inventive concept as defined in the
claims. Therefore, it is to be understood that the foregoing is
illustrative of various example embodiments and is not to be
construed as limited to the specific example embodiments disclosed,
and that modifications to the disclosed example embodiments, as
well as other example embodiments, are intended to be included
within the scope of the appended claims.
* * * * *