Note: Descriptions are shown in the official language in which they were submitted.
METHOD OF EXTRACTING LITHIUM, METHOD OF PREPARING
LITHIUM CARBONATE AND METHOD OF PREPARING LITHIUM
HYDROXIDE
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit of Korean Patent Application No.10-2022-
00043946, filed on April 8, 2022 and Korean Patent Application No.10-2022-
0088189,
filed on July 18, 2022 in the Korean Intellectual Property Office, the entire
disclosures
of which are incorporated herein by reference.
BACKGROUND
1. Field of the Invention
The present invention relates to a method of extracting lithium, a method of
preparing lithium carbonate using the same and a method of preparing lithium
hydroxide using the same.
2. Discussion of Related Art
Lithium (Li) is an essential raw material used in various industries. Lithium
secondary batteries have been widely applied as power sources of IT devices
such as
mobile phones and laptop computers, power sources of power tools, and power
sources
of electric vehicles. Recently, as automobiles using lithium secondary
batteries as a
power source are in the spotlight, the global market demand for lithium is
also rapidly
increasing. Accordingly, there is an urgent need to develop a technique for
efficiently
extracting lithium from lithium resources.
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Date Regue/Date Received 2022-10-17
Examples of lithium resources that are present in nature include seawater,
minerals, and brine. Although seawater contains about 0.17 mg/L of lithium, it
is
known that the concentration is so low that it is uneconomical to extract
lithium from
seawater and use it industrially. Several years ago, a technique for
selectively
adsorbing lithium from seawater using a manganese-based adsorbent and then
desorbing the same by an acid washing method was developed, but it failed to
be
commercialized due to low efficiency and low economic feasibility.
Examples of lithium minerals include spodumene, petalite, and lepidolite, and
they contain about 1 to 1.5 wt% of lithium. However, to extract lithium, many
processes such as pulverization, production of concentrate by flotation, high-
temperature calcining, grinding, acid leaching, removal of impurities, lithium
extraction, refining, lithium concentration, precipitation, and the like are
required, so
there are problems such as a high capital expenditure for production
facilities and
environmental pollution caused by generation of a large amount of acidic
sludge.
Due to the above problems, currently, the extraction of lithium from brine
present in a salt lake is most preferred. Generally, brine contains lithium as
well as
various chemical elements such as magnesium (Mg), calcium (Ca), strontium
(Sr),
aluminum (Al), silicon (Si), boron (B), sodium (Na), potassium (K), chlorine
(Cl),
sulfur (S), and the like. The method first developed to extract lithium from
brine is a
method of extracting a dissolved lithium in the form of lithium carbonate
(Li2CO3).
Since the concentration of lithium contained in brine is as low as 0.5 to 1.5
g/L, it is
essential to concentrate the lithium by water evaporation from brine in solar
pond to
precipitate the dissolved lithium in the form of lithium carbonate having a
high
solubility of 13 g/L. Therefore, in the current solar evaporation process,
lithium is
concentrated from 0.5 to 1.5 g/L up to high concentration of 60 g/L. However,
this
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Date Regue/Date Received 2022-10-17
process takes a long time of about 18 months. Furthermore, most of lithium is
precipitated together with other elements and thus lost during the
concentration
process, so the efficiency of the process is very low.
In order to overcome the above problem, a method precipitating the dissolved
lithium in the form of lithium phosphate (Li3PO4) with very low solubility of
0.39 g/L
without high concentration of lithium was developed (Korean Registered Patent
No.
10-1353342). The dissolved lithium can be easily precipitated in the form of
Li3PO4
even in low concentration due to its very low solubility. Thus, the high
concentration
process of lithium by solar evaporation is not necessary in this method. This
makes it
possible to prevent the co-precipitation of lithium with other elements,
resulting in
serious Li-loss. In order to precipitate lithium in the form of Li3PO4, a
phosphorus (P)
source material is added to brine and allowed to react with lithium, but the
added
phosphorus preferentially reacts with impurities, such as magnesium, calcium,
strontium, and the like, present in brine to produce magnesium phosphate,
calcium
phosphate, strontium phosphate, and the like, so lithium phosphate is not
produced and
precipitated. Therefore, to extract lithium in the form of lithium phosphate
from
brine, impurities such as calcium, magnesium, strontium, and the like need to
be
removed before the addition of a phosphorus (P) source material (Korean
Registered
Patent No. 10-1126286 and Korean Registered Patent No. 10-1405488).
An alkali such as sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH)2)
is commonly added for removal of magnesium(Mg) from brine. The larger amount
of
magnesium presents, the more alkali is required. This means that cost for the
Mg
removal rises as the Mg content in brine increases. In addition to this, the
larger
amount of Mg presents, the more magnesium hydroxide (Mg(OH)2) sludge is
generated. This causes the separation of lithium brine from the sludge to be
extremely
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Date Regue/Date Received 2022-10-17
difficult. Accordingly, the brines including large amount of Mg have been
being
uselessly abandoned.
Meanwhile, calcium (Ca) is removed by adding a salt such as sodium
carbonate (Na2CO3) or sodium sulfate (Na2SO4). The larger amount of calcium
presents, the more salt is required. This means that cost for the Ca removal
rises as the
Ca content in brine increases. Furthermore, the larger amount of Ca presents,
the more
calcium carbonate (CaCO3) or calcium sulfate (CaSO4.2H20) sludge is generated.
This causes the separation of lithium brine from the sludge to be difficult.
Accordingly, the brines including large amount of Ca have also been being
uselessly
abandoned as with the Mg-rich brine.
For these reasons, lithium is produced only from a very few brines having the
low impurity content. Therefore, to meet the rapidly increasing demand for
lithium,
there is an urgent need to develop a technique capable of economically and
efficiently
extracting lithium even from brine having the high impurity content.
There has been a series of effort to extract lithium in the form of Li3PO4,
which
is a poorly soluble compound having a very low solubility in water of 0.39
g/L, from
brine. However, Li3PO4 is not used as a raw material for manufacturing a
positive
electrode material for a lithium secondary battery. Therefore, lithium
phosphate
needs to be converted into lithium hydroxide (Li011.1120) or lithium carbonate
(Li2CO3) to be used as raw material of the positive electrode material. In
order to
convert lithium phosphate into lithium hydroxide or lithium carbonate, a
process of
dissolving lithium phosphate is essential, and a strong acid is generally
used. When
lithium phosphate is dissolved into a strongly acidic solution, phosphorus
present in
lithium phosphate is dissolved into a lithium phosphate solution. Therefore, a
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Date Regue/Date Received 2022-10-17
process of removing phosphorus using a phosphorus anion remover is essential.
This
complicates the process of converting Li3PO4 into Li01-1.1-120 and Li2CO3 and
causes
lithium loss, so there is a problem in that efficiency of the process is
reduced.
SUMMARY OF THE INVENTION
The present invention is directed to provide a method of extracting lithium
from a lithium solution by an economical, efficient, and simple method.
The present invention is also directed to provide a method of preparing
lithium
carbonate or lithium hydroxide from a lithium solution by an economical,
efficient,
and simple method.
One aspect of the present invention provides a method of extracting lithium.
The method of extracting lithium includes adding a phosphorus source
material to a first solution containing a lithium cation (Lit) and an alkaline
earth metal
cations to produce a lithium precipitate including magnesium, calcium, and
phosphorus, wherein the total concentration of the alkaline earth metal
cations in the
first solution is 100,000 mg/L or more.
The lithium precipitate may have a lithium dissolution rate of 25% or more,
calculated according to the following Equation 2:
[Equation 21
Lithium dissolution rate = A/B x 100
(in Equation 2, B = Total concentration of lithium cation contained in the
lithium precipitate (units: mg/L),
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Date Regue/Date Received 2022-10-17
A = Total concentration of lithium cation in filtrate obtained by stirring the
lithium precipitate in 90 C water in an amount of 15 times the weight of the
lithium
precipitate for 60 hours and filtering the slurry(units: mg/L)).
The alkaline earth metal cations may be a magnesium cation (Mg'), a calcium
cation (Ca2+), and a strontium cation (Sr2+).
The first solution may further contain an alkali metal cations.
The alkali metal cations may be one or more of a sodium cation (Nat) and a
potassium cation (lc).
The first solution may further contain cations or anions derived from one or
more of iron, manganese, cobalt, silicon, aluminum, boron, chlorine, and
sulfur.
The first solution may be derived from any one of brine, underground hot
water, seawater, a mineral, and a waste battery.
The concentration of the lithium cation in the first solution may be 70 mg/L
or more.
The lithium precipitate may further contain one or more of sodium, potassium,
chlorine, and sulfur.
The phosphorus source material may be one or more selected from phosphorus,
phosphoric acid, a phosphate, a hydrogen-phosphate and a phosphorus-containing
solution.
The total concentration of the lithium cation (Lit) and the alkaline earth
metal
cations in the first solution may be 100,100 mg/L or more.
The total concentration of the lithium cation, the alkaline earth metal
cations,
and the alkali metal cations in the first solution may exceed 100,000 mg/L.
The method may further include adding 80 C to 100 C water in an amount
of 5 to 20 times the weight of the lithium precipitate to the lithium
precipitate, stirring
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Date Regue/Date Received 2022-10-17
the slurry of the lithium precipitate for 12 hours to 60 hours and then
filtering the slurry
to obtain a second solution, wherein the second solution may contain the
lithium cation
The concentration of the lithium cation in the second solution may be 200
mg/L or more.
The method may further include adding 0.1wt% to 5wt% diluted hydrochloric
acid in an amount of 5 to 20 times the weight of the lithium precipitate to
the lithium
precipitate at room-temperature, stirring the slurry of the lithium
precipitate for 1 hour
to 5 hours and then and then filtering the slurry to obtain a third solution,
wherein the
third solution may contain the lithium cation.
The concentration of the lithium cation in the third solution may be 200 mg/L
or more.
The method may further include preparing lithium hydroxide or lithium
carbonate from the second solution.
Another aspect of the present invention provides a method of preparing
lithium carbonate.
The method of preparing lithium carbonate includes using the lithium
precipitate of the lithium extraction method of the present invention.
Still another aspect of the present invention provides a method of preparing
lithium hydroxide.
The method of preparing lithium hydroxide includes using the lithium
precipitate of the lithium extraction method of the present invention.
The present invention provides a method of extracting lithium from a lithium
solution by an economical, efficient, and simple method.
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Date Regue/Date Received 2022-10-17
The present invention provides a method of preparing lithium hydroxide or
lithium carbonate from a lithium solution by an economical, efficient, and
simple
method.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present invention
will become more apparent to those of ordinary skill in the art by describing
exemplary
embodiments thereof in detail with reference to the accompanying drawings, in
which:
FIG. 1 shows the concentration of lithium cations remaining in the first
solution and the lithium extraction rate according to a reaction time after a
phosphorus
source material is added to a first solution containing the impurities and
lithium cations;
FIG. 2A shows a first solution containing the impurities and a lithium cation;
FIG. 2B shows the slurry obtained after a phosphorus source material is added
to the
first solution of FIG. 2A and allowed to react; and FIG. 2C shows the
appearance of
the lithium precipitate including magnesium, calcium, strontium, and
phosphorus,
which is separated from the slurry obtained after a phosphorus source material
is added
to the first solution and allowed to react;
FIG. 3 shows X-ray diffraction patterns for lithium phosphate (Li3PO4); and
FIG. 4 shows lithium dissolution rates according to a stirring time when each
of lithium phosphate and the lithium precipitate including magnesium, calcium,
strontium, and phosphorus is added to 90 C water and then stirred for 12
hours to 60
hours.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
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Date Regue/Date Received 2022-10-17
Hereinafter, embodiments of the present invention will be described in detail.
However, the embodiments are provided as examples, and the present invention
is not
limited thereto and will be defined only by the scope of the claims to be
described
below.
As used herein, the concentration of various cations and anions may be
measured by atomic emission spectroscopy, for example, inductively coupled
plasma
atomic emission spectroscopy (ICP-AES).
As used herein, "impurities" refer to one or more of cations and anions other
than a lithium cation (Lit) in a first solution.
As used herein, a "first solution" is a lithium feed solution used to extract
lithium and refers to one or more of solutions directly or indirectly derived
from brine,
underground hot water, seawater, a mineral and a waste battery.
As used herein, "room temperature" is not particularly limited and refers to
an
ambient temperature at which the task is performed, for example, a temperature
ranging from 0 C to 50 C.
In the present invention, adding a phosphorus source material to a first
solution
containing various impurities to produce a lithium precipitate including
magnesium,
calcium, strontium, and phosphorus without removal of the impurities is
included. The
present invention, extracting lithium directly without removal of the
impurities,
enables the economical and efficient extraction of lithium from lithium-
bearing
solutions.
As described below, the lithium precipitate is a material completely different
from poorly soluble lithium phosphate (Li3PO4) having very low solubility of
0.39 g/L
in water. The lithium precipitate has quite different chemical composition
from that of
Li3PO4. Lithium phosphate (Li3PO4) has 17.98wt% of Li and 26.75wt% of P. The
value
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Date Regue/Date Received 2022-10-17
of Li versus P ratio (Li/P) in Li3PO4 is 0.67 of 17.98/26.75. Contrary to
this, the lithium
precipitate has 3.7wt% of Li and 10.4wt% of P. The value of Li versus P ratio
(Li/P)
in the lithium precipitate is 0.36 of 3.7/10.4. The chemical composition of
the lithium
precipitate will be described below in further detail.
It also shows completely different behavior of dissolution in water from that
of poorly soluble lithium phosphate (Li3PO4) when it was stirred in 90 C
water for 12
hours to 60 hours. That is, the lithium precipitate has a substantially high
lithium
dissolution rate as compared to poorly soluble lithium phosphate. This
characteristics
of the present invention enables the economical and efficient production of
lithium
hydroxide and lithium carbonate. The lithium dissolution rate will be
described
below in further detail.
In addition, according to the present invention, since a precipitate having a
high lithium dissolution rate and minimized phosphorus elution is produced,
lithium
carbonate or lithium hydroxide can be prepared by an economical, efficient,
and simple
method as compared to a process of preparing lithium hydroxide or lithium
carbonate
from poorly soluble lithium phosphate.
Lithium is used in the form of lithium carbonate or lithium hydroxide.
Accordingly, a process of converting lithium phosphate into lithium hydroxide
or
lithium carbonate is required. Lithium phosphate is generally dissolved into a
strong
acid in the conversion process. The dissolved phosphorous is essentially
removed by
a precipitating agent. However, as the present invention blocks or minimizes
the
dissolution of phosphorus from the lithium precipitate, lithium carbonate or
lithium
hydroxide can be prepared by an economical, efficient, and simple method
without
using the above-described precipitating agent of the dissolved phosphorous.
Date Regue/Date Received 2022-10-17
The present invention provides a method of preparing lithium hydroxide,
which includes using the lithium precipitate of the lithium extraction method
according
to the present invention.
The present invention provides a method of preparing lithium carbonate,
which includes using the lithium precipitate of the lithium extraction method
according
to the present invention.
Hereinafter, the present invention will be described in further detail with
reference to embodiments.
(1) The method of extracting lithium according to the present invention
includes adding a phosphorus source material to a first solution containing a
lithium
cation (Lit) and an alkaline earth metal cations to produce the lithium
precipitate
containing magnesium, calcium, strontium, and phosphorus, wherein the total
concentration of the alkaline earth metal cations in the first solution is
100,000 mg/L
or more.
The concentration of the lithium cation (Lit) in the first solution may be 70
mg/L or more, preferably 100 mg/L or more, and more preferably 150 mg/L or
more.
In an embodiment, the concentration of the lithium cation (Lit) in the first
solution
may be 3,000 mg/L or less, 700 mg/L or less, or 500 mg/L or less, for example
70
mg/L, 80 mg/L, 90 mg/L, 100 mg/L, 110 mg/L, 120 mg/L, 130 mg/L, 140 mg/L, 150
mg/L, 160 mg/L, 170 mg/L, 180 mg/L, 190 mg/L, 200 mg/L, 250 mg/L, 300 mg/L,
350 mg/L, 400 mg/L, 450 mg/L, 500 mg/L, 550 mg/L, 600 mg/L, 650 mg/L, 700
mg/L,
900 mg/L, 1,000 mg/L, 1,500 mg/L, 2,000 mg/L, 2,500 mg/L, 3,000 mg/L.
The total concentration of the alkaline earth metal cations in the first
solution
is 100,000 mg/L or more. However, though total concentration of the alkaline
earth
metal cation in the first solution is 80,000 mg/L or more, the method of
extracting
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Date Regue/Date Received 2022-10-17
lithium according to the present invention, the method of preparing lithium
carbonate
according to the present invention, or the method of preparing lithium
hydroxide
according to the present invention may also be used, depending the type or the
condition of the first solution. Within the above-described range, the lithium
precipitate having a substantially high lithium dissolution rate compared to
that of
lithium phosphate can be easily provided. From chemical composition of the
lithium
precipitate, it is thought that the impurities, such as the alkaline earth
metal cations and
the like, existing in the first solution are utilized as a medium for
generation of the
lithium precipitate and that the lithium cation dissolved in the first
solution is extracted
in the form of the lithium precipitate including alkaline earth metal cations
and
phosphorous.
Preferably, the total concentration of the alkaline earth metal cations in the
first solution may be 100,000 mg/L to 180,000 mg/L, and most preferably,
120,000
mg/L to 180,000 mg/L, for example 100,000 mg/L, 110,000 mg/L, 120,000 mg/L,
130,000 mg/L, 140,000 mg/L, 150,000 mg/L, 160,000 mg/L, 170,000 mg/L, 180,000
mg/L. Within the above-described range, the lithium precipitate
having a
substantially high lithium dissolution rate compared to lithium phosphate can
be easily
provided. In an embodiment, the total concentration of the magnesium cation
(Mg2+),
calcium cation (Ca2+), and strontium cation (Sr2+) in the first solution may
be 100,000
mg/L to 180,000 mg/L, and preferably, 120,000 mg/L to 180,000 mg/L, for
example
100,000 mg/L, 110,000 mg/L, 120,000 mg/L, 130,000 mg/L, 140,000 mg/L, 150,000
mg/L, 160,000 mg/L, 170,000 mg/L, 180,000 mg/L.
In an embodiment, the total concentration of the lithium cation (Lit) and the
alkaline earth metal cation in the first solution may be 100,100 mg/L or more
and
300,000 mg/L or less. Within the above-described range, a precipitate having a
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Date Regue/Date Received 2022-10-17
substantially high lithium dissolution rate compared to lithium phosphate can
be easily
provided. Preferably, the total concentration of the lithium cation (Li+) and
the
alkaline earth metal cation in the first solution may be 100,100 mg/L to
250,000 mg/L,
and most preferably, 100,100 mg/L to 200,000 mg/L, for example 100,100 mg/L,
110,000 mg/L, 120,000 mg/L, 130,000 mg/L, 140,000 mg/L, 150,000 mg/L, 160,000
mg/L, 170,000 mg/L, 180,000 mg/L, 190,000 mg/L, 200,000 mg/L, 210,000 mg/L,
220,000 mg/L, 230,000 mg/L, 240,000 mg/L, 250,000 mg/L, 260,000 mg/L, 270,000
mg/L, 280,000 mg/L, 290,000 mg/L, 300,000 mg/L.
In an embodiment, the total concentration of the lithium cation (Lit), the
magnesium cation (Mg2+), the calcium cation (Ca2+), and the strontium cation
(Sr2+)
in the first solution may be 100,100 mg/L or more and 300,000 mg/L or less,
more
preferably 100,100 mg/L to 250,000 mg/L, and most preferably 100,100 mg/L to
200,000 mg/L, for example 100,100 mg/L, 110,000 mg/L, 120,000 mg/L, 130,000
mg/L, 140,000 mg/L, 150,000 mg/L, 160,000 mg/L, 170,000 mg/L, 180,000 mg/L,
190,000 mg/L, 200,000 mg/L, 210,000 mg/L, 220,000 mg/L, 230,000 mg/L, 240,000
mg/L, 250,000 mg/L, 260,000 mg/L, 270,000 mg/L, 280,000 mg/L, 290,000 mg/L,
300,000 mg/L. Within the above-described range, the lithium precipitate having
a
substantially high lithium dissolution rate compared to lithium phosphate can
be easily
provided.
The alkaline earth metal cations in the first solution may be one or more of a
beryllium cation (Be2+), a magnesium cation (Mg2+), a calcium cation (Ca2+), a
strontium cation (Sr2+), a barium cation (Ba2+), and a radium cation (Ra2+).
In an
embodiment, the alkaline earth metal cations in the first solution may be a
magnesium
cation (Mg'), a calcium cation (Ca'), and a strontium cation (Se). The method
of
extracting lithium according to the present invention may be well applied when
all of
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Date Regue/Date Received 2022-10-17
a magnesium cation (Mg'), a calcium cation (Ca'), and a strontium cation (Se)
are
included as the alkaline earth metal cations.
The first solution may further contain an alkali metal cations. The alkali
metal cations may be an alkali metal cations other than lithium and may be,
for
example, one or more of a sodium cation (Nat), a potassium cation (IC), a
rubidium
cation (Rb+), a cesium cation (Cs), and a francium cation (Fr). In an
embodiment,
the alkali metal cation may be one or more of a sodium cation (Nat) and a
potassium
cation (I(+). The method of extracting lithium according to the present
invention may
be well applied when both a sodium cation (Nat) and a potassium cation (IC')
are
included.
In an embodiment, the total concentration of the alkali metal cation in the
first
solution may be 20,000 mg/L or more, for example, 20,000 mg/L to 50,000 mg/L
or
20,000 mg/L to 40,000 mg/L, for example 20,000 mg/L, 21,000 mg/L, 22,000 mg/L,
23,000 mg/L, 24,000 mg/L, 25,000 mg/L, 26,000 mg/L, 27,000 mg/L, 28,000 mg/L,
29,000 mg/L, 30,000 mg/L, 31,000 mg/L, 32,000 mg/L, 33,000 mg/L, 34,000 mg/L,
35,000 mg/L, 36,000 mg/L, 37,000 mg/L, 38,000 mg/L, 39,000 mg/L, 40,000 mg/L,
41,000 mg/L, 42,000 mg/L, 43,000 mg/L, 44,000 mg/L, 45,000 mg/L, 46,000 mg/L,
47,000 mg/L, 48,000 mg/L, 49,000 mg/L, 50,000 mg/L.
The first solution may further contain cations or anions derived from one or
more of iron, manganese, cobalt, boron, silicon, aluminum, chlorine, and
sulfur. In
an embodiment, the first solution may include a sulfur-derived anion. The
method of
extracting lithium according to the present invention may be well applied when
a
sulfur-derived anion is included.
The total concentration of the lithium cation, alkaline earth metal cations,
and
alkali metal cations in the first solution may exceed 100,000 mg/L. Within the
above-
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Date Regue/Date Received 2022-10-17
described range, a precipitate having a substantially high lithium dissolution
rate
compared to lithium phosphate can be easily provided. Preferably, the total
concentration of the lithium cation (Lit), alkaline earth metal cations, and
alkali metal
cations in the first solution may be 150,000 mg/L to 300,000 mg/L, more
preferably
150,000 mg/L to 250,000 mg/L, and most preferably 150,000 mg/L to 200,000
mg/L,
for example 110,000 mg/L, 120,000 mg/L, 130,000 mg/L, 140,000 mg/L, 150,000
mg/L, 160,000 mg/L, 170,000 mg/L, 180,000 mg/L, 190,000 mg/L, 200,000 mg/L,
210,000 mg/L, 220,000 mg/L, 230,000 mg/L, 240,000 mg/L, 250,000 mg/L, 260,000
mg/L, 270,000 mg/L, 280,000 mg/L, 290,000 mg/L, 300,000 mg/L. In an
embodiment, the total concentration of the lithium cation (Lit), magnesium
cation
(Mg'), calcium cation (Ca'), strontium cation (Sr), sodium cation (Nat), and
potassium cation (I(+) may be 150,000 mg/L or more, preferably 150,000 mg/L to
300,000 mg/L, more preferably 150,000 mg/L to 250,000 mg/L, and most
preferably
150,000 mg/L to 200,000 mg/L, for example 150,000 mg/L, 160,000 mg/L, 170,000
mg/L, 180,000 mg/L, 190,000 mg/L, 200,000 mg/L, 210,000 mg/L, 220,000 mg/L,
230,000 mg/L, 240,000 mg/L, 250,000 mg/L, 260,000 mg/L, 270,000 mg/L, 280,000
mg/L, 290,000 mg/L, 300,000 mg/L.
The phosphorus source material may be one or more selected from phosphorus,
phosphoric acid, a phosphate, a hydrogen-phosphate and a phosphorus-containing
solution. Specific examples of the phosphate include potassium phosphate,
sodium
phosphate, ammonium phosphate (specifically, the ammonium phosphate may be
(NR4)3PO4, wherein R may independently be hydrogen, deuterium, or a
substituted or
unsubstituted Cl to C10 alkyl group), and the like. More specifically, the
phosphate
may be monopotassium phosphate, dipotassium phosphate, tripotassium phosphate,
monosodium phosphate, disodium phosphate, trisodium phosphate, aluminum
Date Regue/Date Received 2022-10-17
phosphate, zinc phosphate, ammonium polyphosphate, sodium hexametaphosphate,
monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, or the like.
The phosphorus source material may be included in an amount of 1 mole to 4
moles based on 1 mole of the lithium cation in the first solution. Within the
above-
described range, the effect of the present invention can be easily
implemented.
The production of the lithium precipitate may be performed by adding a
phosphorus source material to a first solution and performing stirring at room
temperature for 1 hour to 24 hours. As a result, the lithium precipitate
containing
lithium, magnesium, calcium, strontium, and phosphorus may be easily produced,
and
a lithium extraction rate may be high. In this case, "room temperature" does
not
mean a particular temperature and means a temperature without the addition of
external energy. Therefore, room temperature may vary depending on a place and
time. For example, room temperature may be 20 C to 30 C. Preferably, a
stirring
time may be 1 hour to 12 hours. Within the above-described ranges, a lithium
extraction rate can be substantially high.
In an embodiment, this step may be performed so that a lithium extraction rate
of the following Equation 1 is 70% or more, for example, 70% to 100%.
[Equation 11
Lithium extraction rate = A/B x 100
(in Equation 1,
A = Concentration of lithium cation in first solution ¨ Concentration of
lithium
cation in filtrate obtained in the production of the lithium precipitate
(units: mg/L),
B = Concentration of lithium cation in first solution (units: mg/L))
Referring to FIG. 2A to FIG. 2C, a first solution is a transparent solution.
On
the other hand, a first solution obtained after a phosphorus source material
is added to
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Date Regue/Date Received 2022-10-17
the first transparent solution and allowed to react is a white opaque slurry.
Then, the
opaque slurry may be filtered to produce the lithium precipitate as a white
solid.
The lithium precipitate may be separated from the slurry by a typical method
such as filtration from the first solution.
The lithium precipitate contains lithium, magnesium, calcium, strontium, and
phosphorus. In an embodiment, the lithium precipitate may further contain one
or
more of sodium, potassium, chlorine, and sulfur.
(2) The method of extracting lithium according to the present invention may
further include adding 80 C to 100 C water in an amount of 5 to 20 times the
weight
of the lithium precipitate to the lithium precipitate, stirring the slurry for
12 hours to
60 hours and then filtering the slurry to obtain a second solution, wherein
the second
solution may contain the lithium cation (Lit). Within the above-described
water
content, water temperature, stirring time ranges, the dissolution of the
lithium cation
from the lithium precipitate can be facilitated. Preferably, this step may be
performed
by adding 85 C to 95 C water in an amount of 7 to 18 times the weight of the
lithium
precipitate to the lithium precipitate, stirring the slurry for 12 hours to 60
hours and
then filtering the slurry.
The concentration of the lithium cation in the second solution may be 200
mg/L or more, for example 500 mg/L or more, 1000 mg/L or more, 10000 mg/L or
less, 5000 mg/L or less, or 3000 mg/L or less, for example 500 mg/L, 600 mg/L,
700
mg/L, 800 mg/L, 900 mg/L, 1000 mg/L, 2000 mg/L, 3000 mg/L, 4000 mg/L, 5000
mg/L, 6000 mg/L, 7000 mg/L, 8000 mg/L, 9000 mg/L, 10000 mg/L.
This step may allow subsequent preparation of lithium carbonate or lithium
hydroxide to be facilitated by selectively dissolving a lithium cation from
the lithium
17
Date Regue/Date Received 2022-10-17
precipitate. This is because the dissolution rate of a lithium cation from the
lithium
precipitate is high.
In an embodiment, the lithium precipitate may have a lithium dissolution rate
of 25% or more, for example, 50% or more, 60% or more, 60% to 100%, when
stirred
in 90 C water in an amount of 15 times the weight of the precipitate for 12
hours to
60 hours. Within the above-described range, lithium hydroxide or lithium
carbonate
can be easily prepared from the lithium precipitate. The lithium dissolution
rate may
be calculated according to the following Equation 2:
[Equation 21
Lithium dissolution rate = A/B x 100
(in Equation 2, B = Total concentration of lithium cation contained in the
lithium precipitate (units: mg/L),
A = Total concentration of lithium cation in filtrate obtained by stirring the
lithium precipitate in 90 C water in an amount of 15 times the weight of the
lithium
precipitate for 60 hours and filtering the slurry(units: mg/L)).
In an embodiment, the lithium precipitate may have a phosphorus dissolution
rate of less than 0.2% when stirred in 90 C water in an amount of 15 times
the weight
of the lithium precipitate for 12 hours to 60 hours. Within the above-
described range,
when lithium carbonate is prepared using the lithium precipitate solution, the
use of a
phosphorus anion precipitating agent may not be required to remove a
phosphorus
anion. The phosphorus dissolution rate may be calculated according to the
following
Equation 3:
[Equation 31
Phosphorus dissolution rate = A/B x 100
(in Equation 3,
18
Date Regue/Date Received 2022-10-17
B = Total concentration of phosphorus anion contained in the lithium
precipitate (units: mg/L),
A= Total concentration of phosphorus anion in filtrate obtained by stirring
the
lithium precipitate in 90 C water in an amount of 15 times the weight of the
lithium
precipitate for 60 hours and filtering the slurry (units: mg/L)).
Although B in Equation 2 is not particularly limited, B may be calculated from
the total concentration of the lithium cation in a solution obtained by
completely
dissolving the lithium precipitate in a room-temperature aqueous hydrochloric
acid
solution (the concentration of hydrochloric acid in the aqueous hydrochloric
acid
solution is 9wt% to 15wt%) in an amount of 15 times the weight of the lithium
precipitate.
Although B in Equation 3 is not particularly limited, B may be calculated from
the total concentration of the phosphorus anion in a solution obtained by
completely
dissolving the lithium precipitate in a room-temperature aqueous hydrochloric
acid
solution (the concentration of hydrochloric acid in the aqueous hydrochloric
acid
solution is 9wt% to 15wt%) in an amount of 15 times the weight of the
precipitate.
In an embodiment, the lithium precipitate may have a lithium dissolution rate
of 90% or more, for example, 98% to 100%, when stirred in 90 C water in an
amount
of 15 times the weight of the lithium precipitate for 36 hours to 60 hours.
Within the
above-described range, lithium hydroxide or lithium carbonate can be easily
prepared
from the lithium precipitate.
(3) The method of extracting lithium according to the present invention may
further include adding room-temperature 0.1wt% to 5wt% diluted hydrochloric
acid,
for example diluted hydrochloric acid aqueous solution in an amount of 5 to 20
times
the weight of the lithium precipitate to the lithium precipitate, stirring the
slurry for 1
19
Date Regue/Date Received 2022-10-17
hour to 5 hours and then filtering the slurry to obtain a third solution,
wherein the third
solution may contain the lithium cation. The concentration of the lithium
cation in
the third solution may be 200 mg/L or more. Lithium hydroxide or lithium
carbonate
may be prepared from the third solution.
(4) The method of preparing lithium carbonate according to the present
invention includes using the lithium precipitate of the lithium extraction
method
according to the present invention.
The method of preparing lithium carbonate according to the present invention
may include: obtaining the lithium precipitate of the lithium extraction
method
according to the present invention (step 1); adding 80 C to 100 C water in
an amount
of 5 to 20 times the weight of the lithium precipitate to the lithium
precipitate,
stirring the slurry for 12 hours to 60 hours and then filtering the slurry to
obtain a
second solution containing a lithium cation (Lit) (step 2); and carbonating
the second
solution to prepare lithium carbonate (step 3).
Step 1 and step 2 are the substantially same as described above. Therefore,
hereinafter, only step 3 will be described.
Step 3 is a step of carbonating the second solution to prepare lithium
carbonate.
The carbonation may be performed by adding a carbonate to the second solution
or by
using carbonating gas. The carbonate may be sodium carbonate (Na2CO3). The
preparation of lithium carbonate using a carbonate or carbonating gas may be
performed by a typical method known in the art.
In an embodiment, the method of preparing lithium carbonate according to the
present invention may not include using an acid or acid aqueous solution.
Date Regue/Date Received 2022-10-17
(5) The method of preparing lithium hydroxide according to the present
invention includes using the lithium precipitate of the lithium extraction
method
according to the present invention.
The method of preparing lithium carbonate according to the present invention
may include: obtaining the lithium precipitate of the lithium extraction
method
according to the present invention (step 1); adding 80 C to 100 C water in
an amount
of 5 to 20 times the weight of the lithium precipitate to the lithium
precipitate, stirring
the slurry for 12 hours to 60 hours and then filtering the slurry to obtain a
second
solution containing a lithium cation (Lit) (step 2); and adding a precipitator
precipitating phosphate anion to the second solution to prepare lithium
hydroxide (step
3).
Step 1 and step 2 are the substantially same as described above. Therefore,
hereinafter, only step 3 will be described.
Step 3 is a step of adding a precipitator precipitating phosphate anion to the
second solution to prepare lithium hydroxide. The precipitator may be an oxide
or
hydroxide of alkaline earth metals including Ca, Sr, Ba, Ra, Be or Mg, such as
calcium
hydroxide.
Hereinafter, examples of the present invention will be described in detail
with
reference to the accompanying drawing. However, the following examples are
merely presented to exemplify the present invention, and the present invention
is not
limited thereto.
[Example 1]
As shown in the following Table 1, a brine-derived lithium solution containing
impurities was prepared as a first solution.
21
Date Regue/Date Received 2022-10-17
[Table 1]
Chemical
Li+ mg2+ Ca2+ Sr+ Na+ K+ S
components
Content (mg/L) 346 21,770 128,571 2,275 7,482 16,730
16
Na3PO4 was added in an amount of 2 moles based on 1 mole of a lithium cation
in the first solution to the first solution and allowed to react while
stirring at room
temperature for 1 hour to 24 hours. After the reaction was completed, the
resulting
solution was filtered to separate the lithium precipitate in the form a solid
cake, and a
filtrate was collected. The lithium, magnesium, calcium, and strontium
concentrations of the filtrate were measured using an atomic emission
spectrometer
(ICP-AES), and results thereof are shown in Table 2.
[Table 21
Concentration of chemical components of filtrate (mg/L) Lithium
Reaction time
extraction rate
(111.) Li + mg2+ Ca2+ se+ (0,0)
1 284 21,135 124,246 2,270 17.9
2 228 21,105 123,573 2,267 34.1
3 197 20,968 122,385 2,250 43.1
4 169 20,960 122,676 2,252 51.2
6 131 20,939 119,452 2,225 62.1
8 111 20,859 119,499 2,224 67.9
10 105 20,881 113,667 2,228 69.7
12 94 20,810 112,150 2,218 72.8
24 67 20,725 106,300 2,199 80.6
In Table 2, a lithium extraction rate was calculated by the formula
(Concentration of lithium cation in first solution-Concentration of lithium
cation in
filtrate) x100/(Concentration of lithium cation in first solution).
22
Date Regue/Date Received 2022-10-17
As shown in Table 2, it can be confirmed that, after 24 hours of reaction, 279
mg/L corresponding to about 81% of 346 mg/L of lithium cation dissolved in the
first
solution was precipitated as the lithium precipitate, and thus only 67 mg/L
remained
in the reaction filtrate. From this result, it can be seen that lithium
cations are
successfully extracted from the first solution containing a large amount of
impurities.
A change in the concentration of lithium dissolved in the first solution and
the
lithium extraction rate according to a reaction time, which are shown in Table
2, is
graphically shown in FIG. 1. Referring to FIG. 1, it can be confirmed that a
lithium
cation concentration in the filtrate (left Y-axis) was gradually decreased
according to
a reaction time (X-axis), and accordingly, the lithium extraction rate was
gradually
increased.
The precipitate was dried at 105 C for 24 hours, the chemical composition of
the resulting lithium precipitate were measured by ICP-AES, and the weight
percentage of each component in lithium precipitate is shown in Table 3.
[Table 31
Chemical components Li + mg2+ Ca2+ Sr2+
Content (wt%) 3.7 2.69 12.24 0.28 10.4
As shown in Table 3, it can be clearly seen that lithium can be successfully
extracted by producing a lithium precipitate using impurities as a medium in
the first
solution.
[Example 2]
The lithium precipitate shown in Table 3 was mixed with 90 C water in an
amount of 15 times the weight of the lithium precipitate, stirred for 12 hours
to 60
hours, and then filtered to obtain a filtrate as a second solution. The
chemical
23
Date Regue/Date Received 2022-10-17
composition of the second solution was analyzed by ICP-AES, and results
thereof are
shown in Table 4.
For identifying the concentrations of lithium and phosphorous upon a
complete dissolution of the lithium precipitate shown in Table 3, the lithium
precipitate
shown in Table 3 was mixed with 9wt% hydrochloric acid aqueous solution of 15
times
the weight of the lithium precipitate and stirred. The concentrations of
lithium and
phosphorous of the aqueous solution were measured to be 1,879 mg/L and 5,897
mg/L,
respectively through ICP-AES analysis. From this result, it was confirmed
that, when
the lithium precipitate was completely dissolved in 90 C water in an amount
of 15
times the weight of the lithium precipitate, the concentrations of lithium and
phosphorous were 1,879 mg/L and 5,897 mg/L, respectively. These values of
concentration were compared with those of the second solutions, stirred for 12
hours
to 60 hours. From these comparisons, the dissolution rates of lithium and
phosphorus
were calculated according to Equation 2.
As shown in Table 4, it was confirmed that, when the precipitate was mixed
with 90 C water in an amount of 15 times the weight of the precipitate and
then stirred
for 60 hours, 98.2% of lithium contained in the lithium precipitate, that is,
almost all
of lithium in it, was dissolved. In other, it was confirmed that, unlike when
the
lithium precipitate was mixed with hydrochloric acid and stirred, when the
lithium
precipitate was mixed with 90 C water in an amount of 15 times the weight of
the
lithium precipitate and then stirred for 60 hours, phosphorus contained in the
lithium
precipitate was hardly dissolved. From these results, it can be seen that,
when lithium
carbonate is prepared using the lithium precipitate solution, the use of a
phosphorus
anion precipitating agent is not required to remove a phosphorus anion. Also,
it can
be easily seen that, when the lithium precipitate is dissolved using a weak
acid diluted
24
Date Regue/Date Received 2022-10-17
using a large amount of water, lithium can be dissolved without dissolution of
phosphorus even at room temperature.
[Table 4]
Concentration of chemical components dissolved into second
Stirring solution (mg/L) Lithium Phosphorus
time
dissolution dissolution
(hl") rate (%) rate (%)
Li Mg2F Ca2+ 5r2+ pn-
12 1,103 1,517 586 16 9 58.7 0.15
24 1,262 1,503 478 12 8 67.2 0.14
32 1,437 1,516 425 11 9 76.5 0.15
48 1,582 1,619 422 11 10 84.2 0.17
60 1,846 1,796 444 11 11 98.2 0.19
[Comparative Example]
As shown in the X-ray diffraction analysis result of FIG. 3, single-phase
lithium phosphate (Li3PO4) was prepared. Lithium phosphate is a poorly soluble
compound having a solubility of 0.39 g/L. Lithium phosphate was mixed with
water
in an amount of 15 times the weight of the lithium phosphate to prepare an
aqueous
lithium phosphate solution, and the aqueous solution was stirred at 90 C for
12 hours
to 60 hours and then filtered. The chemical compositions of the obtained
filtrates
were analyzed by ICP-AES, and results thereof are shown in Table 5.
For identifying the concentration of lithium upon a complete dissolution of
lithium phosphate, lithium phosphate was mixed with 9wt% hydrochloric acid
aqueous
solution of 15 times the weight of lithium phosphate and stirred. The lithium
concentration of the aqueous solution was measured to be 9,739 mg/L through
ICP-
Date Regue/Date Received 2022-10-17
AES analysis. From this result, it was confirmed that, when lithium phosphate
was
completely dissolved in 90 C water in an amount of 15 times the weight of
lithium
phosphate, the concentration of lithium was 9,739 mg/L.
These values of concentration were compared with those of the second
solutions, stirred for 12 hours to 60 hours. From these comparisons, the
dissolution
rate of lithium were calculated according to Equation 2. Results thereof are
shown in
Table 5 and FIG. 4.
[Table 5]
Concentration of chemical components dissolved into aqueous Lithium
Stirring solution including Li3PO4 (mg/L)
dissolution rate
time (hr)
Li+ mg2+ Ca2+ Sr2+ (%)
12 22 0 0 0 0.2
24 22 0 0 0 0.2
36 22 0 0 0 0.2
48 22 0 0 0 0.2
60 23 0 0 0 0.2
As described above, lithium phosphate is a typical poorly soluble material
having a solubility of 0.39 g/L in water. As shown in Table 5, even when
lithium
phosphate is stirred in water for 60 hours, it has a very low lithium
dissolution rate of
0.2%. This is significantly different from that the lithium precipitate has a
high
dissolution rate of 98.2% under similar condition. These experimental results
clearly
show that the lithium precipitate of the present invention is a material
having
physicochemical properties completely different from those of poorly soluble
lithium
phosphate(Li3PO4). Therefore, from Example 2 and Comparative Example, it is
shown that the lithium precipitate extracted from a lithium solution according
to the
26
Date Regue/Date Received 2022-10-17
present invention is not a generally known poorly soluble lithium phosphate
having a
solubility of 0.39 g/L. Also, it is obvious that the lithium dissolution
behavior of the
lithium precipitate and lithium phosphate in aqueous solutions are
significantly
different as shown in Table 5 and FIG. 4.
The present invention is not limited to the embodiments described herein and
may be embodied in other forms, and it will be understood by those skilled in
the art
to which the invention pertains that the present invention can be implemented
in other
specific forms without changing the technical spirit or essential features of
the present
invention. Therefore, it should be understood that the embodiments described
above
are only exemplary in all aspects and not limiting.
27
Date Regue/Date Received 2022-10-17
