Article
Extraction of Lithium from Lepidolite Using Mixed
Grinding with Sodium Sulfide Followed by
Water Leaching
Jaeryeong Lee
Received: 11 October 2015 ; Accepted: 10 November 2015 ; Published: 16 November 2015
Academic Editor: William Skinner
Department of Energy & Resources Engineering, Kangwon National University, Chuncheon,
Kangwon-do 200-701, Korea; [email protected]; Tel.: +82-33-250-6252; Fax: +82-33-252-5550
Abstract: Mixed grinding with Na2 S followed by water leaching was performed to extract Li
from lepidolite. The leachability of Li increases dramatically in the ground mixture, regardless
of the mixing ratio over the range of 1:1 to 3:1, while only 4.53% of Li was extracted in lepidolite
ground without Na2 S. The leachability increased with an increase of the grinding time, and
ultimately, 93% of the Li was leached by water from the ground mixture with a weight ratio of 3:1
(Na2 S:Lepidolite). In the process of the mixed grinding, the Li-contained lepidolite was destructured
crystallographically, and it might have changed to different compounds. This process enables us to
extract Li from lepidolite via a water leaching treatment.
Keywords: lepidolite; sodium sulfide; mixed grinding; lithium; water leaching
1. Introduction
Lithium (Li), the lightest metal in nature, has unique electrochemical properties and the
highest specific heat of the solid elements. Moreover, some lithium compounds possess flat
viscosity/temperature ratios. Due to these fascinating properties, Li and its compounds have
attracted much attention for use in various applications in the ceramics, glass, lubrication,
pharmaceutical industries as well as the battery/fuel cell industry [1,2]. Currently, the main
consumption of Li is in the glass/ceramics manufacturing industry, where Li lowers the melting
point of the glass and ceramics [3,4] and for light weight Li-ion batteries. As the Li-ion batteries
used in future electric and hybrid vehicles will greatly increase the demand for Li, the global Li
market consumption, measured as Li carbonate equivalents, is expected to increase dramatically, from
120,000 in 2011 to 160,000 ton in 2015 [5–7].
The main sources of Li are natural brines and minerals. Natural brines refer to lakes, salars,
oilfield and geothermal brines, which are found principally in Argentina, Bolivia, Chile, China and
the USA. Currently, these brines are the dominant source for worldwide Li-production because of not
only the lower production costs but also the much simpler process compared with the processes for
pegmatitic minerals. Nevertheless, many research studies have been recently conducted regarding Li
extraction from minerals, such as spodumene, zinnwaldite, and lepidolite, because of the persistent
and tremendous growth in demand that is forecasted for Li batteries that will be used to power
both hybrid and fully electric automobiles [8]. Among these minerals, Li extraction processes from
lepidolite (K(Li,Al)3 (Si,Al)4 O10 (F,OH)2 ) have been researched actively because of their wide spread
distribution, the characteristic of being poor in iron, and the additional content of rare metals, such
as rubidium (Rb) and cesium (Cs) [5,9–11]. These processes are composed to two stages: Sulfation
and water leaching. Sulfation is conducted using the sulfuric acid method and the lime method.
However, the extraction of Li by the sulfuric acid method uses a high concentration of acid, and the
Minerals 2015, 5, 737–743; doi:10.3390/min5040521
www.mdpi.com/journal/minerals
Minerals 2015, 5, 737–743
Minerals 2015, 5, page–page
purification procedure is complex. In addition, the lime method uses limestone and requires a large
amount
of (K(Li,Al)
energy. To
accomplish
a higher
Li extraction
of with
over water
90% by
water
leaching
from lepidolite
3(Si,Al)
4O10(F,OH)
2), it must
be heated
steam
for
defluorination
[11–14].
lepidolite
(K(Li,Al)
(F,OH)
it must be of
heated
with water
steam for
defluorination
[11–14]. These
These drawbacks
limit
the2 ),
availability
lepidolite
as a lithium
main
source. To overcome
these
3 (Si,Al)4 O10
drawbacks
the availability
of lepidolite
as a lithium
source. To overcome
these
drawbacks,
drawbacks,limit
our research
group tested
the applicability
of main
mechanochemical
treatment
for Li
extraction
our
group
tested
the applicability
mechanochemical
treatmentThis
for study
Li extraction
from
fromresearch
lepidolite
without
thermal
treatment ofofsulfation
and defluorination.
may provide
lepidolite
without
treatment
of sulfation
and defluorination.
This study may provide
information
for thethermal
use of low
grade lepidolite
as a source
in Li production.
information for the use of low grade lepidolite as a source in Li production.
2. Experimental Section
2. Experimental Section
2.1. Materials
2.1. Materials
The lithium-contained lepidolite was provided by the Boam mine (Uljin, Korea), and it was
upgraded
through crushing and
opticalwas
sorting
treatment.
TheBoam
crushing
was(Uljin,
carried
out by and
jaw crusher
The lithium-contained
lepidolite
provided
by the
mine
Korea),
it was
(BICO Ltd.,
Burbank,
CA, USA)
open
settingtreatment.
at 100 mmThe
of width
andwas
10 mm
of gap.
first
upgraded
through
crushing
and with
optical
sorting
crushing
carried
out The
by jaw
upgraded
lepidolite
was subjected
to grinding
via setting
a rod mill
at 60
rpm
and then
screened
with
crusher
(BICO
Ltd., Burbank,
CA, USA)
with open
at 100
mm
of width
andwas
10 mm
of gap.
Thea
#200upgraded
sieve (aperture
size: was
74 μm)
for a complete
pass.via
Thea material
ground
to 74was
μmscreened
or under
first
lepidolite
subjected
to grinding
rod mill that
at 60was
rpm
and then
was used
this study
as a size:
starting
material,
and its phases
identified
bywas
using
high resolution
with
a #200insieve
(aperture
74 µm)
for a complete
pass. were
The material
that
ground
to 74 µm
X-ray
diffraction
X’pert-Pro
MPD,material,
PANalytical,
Almelo,
using
or
under
was used(HRXRD,
in this study
as a starting
and its
phasesThe
wereNetherland)
identified by
usingCu-Kα
high
radiation (λ
= 1.5406
Å).
resolution
X-ray
diffraction
(HRXRD, X’pert-Pro MPD, PANalytical, Almelo, The Netherland) using
Cu-Kα
= 1.5406
Å). starting material was primarily quartz (SiO2, JCPDs No. 87-2096, Ⓠ),
Asradiation
shown in(λFigure
1, the
As shown in Figure 1, the starting material was primarily quartz (SiO2 , JCPDs No. 87-2096,
muscovite (K(OH,F2)2Al3Si3O10, JCPDs No. 7-0042, Ⓜ), and lepidolite (KLiAl(OH,F)2Al(SiO4)3, JCPDs
Q ), muscovite (K(OH,F2 )2 Al3 Si3 O10 , JCPDs No. 7-0042, M ), and lepidolite (KLiAl(OH,F)2 Al(SiO4 )3 ,
No. 76-0535,
Ⓛ). Moreover,
the chemical
composition,
as as
presented
ininTable
by
JCPDs
No. 76-0535,
L ). Moreover,
the chemical
composition,
presented
Table1,1, was
was analyzed by
X-ray
X-rayfluorescence
fluorescence(XRF,
(XRF,X-ray
X-rayFluorescence,
Fluorescence,S2
S2ranger,
ranger,Bruker,
Bruker,Billerica,
Billerica,MA,
MA,USA),
USA),and
andthe
thelithium
lithium
content
was
measured
by
using
an
Inductively
Coupled
Plasma
spectrometer
(ICP,
OPTIMA
content was measured by using an Inductively Coupled Plasma spectrometer (ICP, OPTIMA 7300DV,
7300DV,
Perkin
Perkin Elmer,
Elmer, Waltham,
Waltham,MA,
MA, USA),
USA), after
after chemical
chemical digestion
digestion treatment.
treatment. Moreover,
Moreover,aatotal
totalmass
massloss
lossof
of
˝ C.
~3.3%
was
measured
by
thermogravimetric
analysis
(TGA)
at
1000
~3.3% was measured by thermogravimetric analysis (TGA) at 1000 °C.
Q Quartz (SiO2)
M Muscovite (K(OH,F2)2Al3Si3O10)
Intensity (a.u.)
Q
L Lepidolite (KLiAl(OH,F)2Al(SiO4)3
M
M
M
L
M
M
Q
10
L
L
20
L
L
L
L
L
LL
L
30
M
L
L
40
M
L
50
L
L
Q L
60
70
L
80
2 / ° (Cu-Kα)
Figure 1.
1. X-ray
X-ray diffraction
diffraction (XRD)
(XRD) pattern
pattern of
of the
the first
firstupgraded
upgradedlepidolite
lepidoliteused
usedin
inthis
thisstudy.
study.
Figure
Table 1. Composition (%) of the first upgraded lepidolite analyzed by X-ray fluorescence (XRF) and
Inductively Coupled Plasma spectrometer (ICP).
Al2O3
28.76
SiO2
55.12
K2O
12.83
CaO
1.04
MnO
738
0.3
2
Fe2O3
0.16
Rb2O
1.46
Cs2O
0.33
Li
1.74
Minerals 2015, 5, 737–743
Table 1. Composition (%) of the first upgraded lepidolite analyzed by X-ray fluorescence (XRF) and
Inductively Coupled Plasma spectrometer (ICP).
Al2 O3
SiO2
K2 O
CaO
MnO
Fe2 O3
Rb2 O
Cs2 O
Li
28.76
55.12
12.83
1.04
0.3
0.16
1.46
0.33
1.74
2.2. Intensive Grinding with Sodium Sulfide (Na2 S)
As a grinding additive for increasing the lithium solubility, sodium sulfide (Na2 S, SS), was used
in this study. SS was prepared from sodium sulfide nonahydrate (Na2 S¨ 9H2 O, 96%), supplied from
Junsei Chemical Co., Ltd. (Tokyo, Japan), which was calcined at 120 ˝ C for 6 h for dehydration. The
mixture of upgraded lepidolite (UL) and SS was used to produce samples of different weight ratios
(UL:SS), ranging from 1:1 to 1:3, and these different mixtures were kept in a desiccator. To grind each
mixture intensively,
a planetary ball mill (Pulverizette-7, Fritsch Gmbh, Idar-Oberstein, Germany)
Minerals 2015, 5, page–page
was used. The mill conditions were as follows: 4 g of each mixture was placed into a zirconia pot
2.2. Intensive Grinding with Sodium Sulfide (Na2S)
(45 cm3 inner volume)
with seven 15-mm diameter zirconia balls and then was subjected to grinding
As a grinding additive for increasing the lithium solubility, sodium sulfide (Na2S, SS), was used
in air at 700 rpminfor
various
periods of time.
this study. SS was prepared from sodium sulfide nonahydrate (Na2S·9H2O, 96%), supplied from
Junsei Chemical Co., Ltd. (Tokyo, Japan), which was calcined at 120 °C for 6 h for dehydration. The
mixture
upgraded
lepidolite
(UL) of
andLepidolite
SS was used and
to produce
samples
of different weight ratios
2.3. Water Leaching
for of
the
Ground
Mixture
Sodium
Sulfide
(UL:SS), ranging from 1:1 to 1:3, and these different mixtures were kept in a desiccator. To grind each
mixture
intensively,
a planetary
ball millwas
(Pulverizette-7,
Fritsch
Gmbh,distilled
Idar-Oberstein,
Germany)
was the following
Subsequently,
the
ground
mixture
leached
with
water
using
used. The mill conditions were as follows: 4 g of each mixture was placed into a zirconia pot (45 cm3
conditions: Room
temperature,
slurry
density
(20
g/L),
stirring
by
magnetic
bar,
leaching time
inner volume) with seven 15-mm diameter zirconia balls and then was subjected to grinding in airand
at
700
rpm
for
various
periods
of
time.
(30 min). To acquire more accurate data for Li leachability, the content of Li was analyzed not only
for the leached solution
but also
theMixture
leached
residue
afterSulfide
chemical digestion. The leachability of
2.3. Water Leaching
for thefor
Ground
of Lepidolite
and Sodium
Li was calculated according
theground
following
Subsequently,tothe
mixture equation:
was leached with distilled water using the following
conditions: Room temperature, slurry density (20 g/L), stirring by magnetic bar, and leaching time
(30 min). To acquire more accurate data for Li leachability,
the content
of Li was analyzed not only
Li content
pAq
ˆ 100 of
Leachability
ofbutLialso
p%q
“ leached residue after chemical digestion. The leachability
for the
leached solution
for the
Li content
Li was calculated according to the following
equation: pAq ` Li content pBq
Li content A
(1)
(1) solution, and Li
LeachabilityofLi
% =from the Li concentration
× 100in the leached
where Li content (A) is the Li mass
calculated
Li content A + Li content B
content (B) represents
the
Li
mass
in
the
leached
residue
after
complete
dissolution.
Figure 2 presents
where Li content (A) is the Li mass calculated from the Li concentration in the leached solution, and
Li
content
(B)
represents
the
Li
mass
in
the
leached
residue
after
complete
dissolution.
Figure
2
the flow sheet of the experimental procedure in this study.
presents the flow sheet of the experimental procedure in this study.
Upgraded Lepidolite
Na2S·9H2O
Milling (Rod mill)
Over
Dehydration
Sieving (#200)
Pass
Mixing
Na2S
Intensive Grinding
Water Leaching
Filtration
Solution
Residue
Chemical Digestion
Li content (A)
Li content (B)
Figure 2. Flow chart summarizing the all the processes used in this study.
Figure 2. Flow chart summarizing the all the processes used in this study.
3
739
Minerals 2015, 5, 737–743
3. Results and Discussion
3.1. The Change of Li-Leachability from Lepidolite
Minerals 2015, 5, page–page
To investigate the effect of additives and grinding on lithium leachability from lepidolite, a series
of experiments
performed. The mixture ratio of (UL:SS) was changed from (1:1) to (1:3), and the
3. Results were
and Discussion
durations of grinding for different samples were over the range of 0 to 12 h. Subsequently, each of the
3.1. The Change of Li-Leachability from Lepidolite
ground mixtures was leached for 30 min with distilled water. To compensate for the inhomogeneity
To investigate
the effectthe
of additives
grinding
lithium leachability
from lepidolite,
a series
of the Li content
in lepidolite,
leachingand
test
of eachoncondition
was replicated,
and the
result was
of experiments were performed. The mixture ratio of (UL:SS) was changed from (1:1) to (1:3), and the
taken as the mean value of three experiments.
durations of grinding for different samples were over the range of 0 to 12 h. Subsequently, each of
The
of leaching
were summarized
Figure
3. As
shown in this
figure,
Li in UL was
the results
ground mixtures
was leached
for 30 min within
distilled
water.
To compensate
for the
inhomogeneity
rarely dissolved
(4.54%)
without
the
additive
SS,
even
if
intensive
grinding
was
performed
for 12 h.
of the Li content in lepidolite, the leaching test of each condition was replicated, and the result was
Meanwhile,
inthe
themean
casevalue
of grinding
with SS, the results confirm the favorable influence of intensive
taken as
of three experiments.
The
results
of leaching
summarized
in Figure 3.ofAs
shown
in this
figure,
in UL was rarely
grinding on
the
leachability
ofwere
Li from
UL. Regardless
the
mixing
ratio,
theLileachability
increases
dissolved
(4.54%)
without of
thethe
additive
SS, even
intensive grinding
was performed
for(SS:UL),
12 h.
dramatically
with
an increase
grinding
time.if Regarding
the mixing
ratio of 1:1
the
Meanwhile, in the case of grinding with SS, the results confirm the favorable influence of intensive
leachability increased steadily to 84.4% as a function of a grinding time of up to 6 h. Subsequently,
grinding on the leachability of Li from UL. Regardless of the mixing ratio, the leachability increases
the leachability decreased slightly to 82%, even though the grinding progressed to 12 h. A similar
dramatically with an increase of the grinding time. Regarding the mixing ratio of 1:1 (SS:UL), the
tendency
for the relationship
between
Li yield
and theofgrinding
be6 verified
in the case of
leachability
increased steadily
to 84.4%
as a function
a grindingtime
time could
of up to
h. Subsequently,
the mixture
at the ratio
of 2:1 (SS:UL).
Leachability
(90.9%)
accomplished
the leachability
decreased
slightly to
82%, even though
thewas
grinding
progressedby
to water
12 h. Aleaching
similar from
tendency
for thefor
relationship
Li yield
and the
time
could grinding
be verifiedtimes.
in the case
of
the mixture
ground
6 h, and itbetween
decreased
slightly
to grinding
90.06% for
longer
Meanwhile,
the
mixture
at
the
ratio
of
2:1
(SS:UL).
Leachability
(90.9%)
was
accomplished
by
water
leaching
from
the leachability from the mixture at the ratio of 3:1 (SS:UL) increased consistently with the grinding
the mixture
ground
for 6 h,
and it decreased
slightly tofor
90.06%
for longer
grinding
times.
Meanwhile, were
time, although
the
gradient
decreased
progressively
further
grinding.
These
leachabilities
the leachability from the mixture at the ratio of 3:1 (SS:UL) increased consistently with the grinding
confirmed to be 83% (from the mixture ground for 3 h), 90.1% (for 6 h), and 93% (for 12 h). In general,
time, although the gradient decreased progressively for further grinding. These leachabilities were
intensive
grinding results in the enhancement of the leaching reaction due to an increased specific
confirmed to be 83% (from the mixture ground for 3 h), 90.1% (for 6 h), and 93% (for 12 h). In general,
surfaceintensive
area, enhanced
surface
and changes
in crystalline
for various
materials,
grinding results
in reactivity
the enhancement
of the leaching
reaction structure
due to an increased
specific
which surface
include
minerals.
this reactivity
study, leaching
of Li
from onlystructure
the ground
UL has
little effect
area,
enhanced In
surface
and changes
in crystalline
for various
materials,
whichleachability
include minerals.
this study,
leaching
of Lithat
from
the ground
has ground
little effect
(maximum
of Li:In4.65%),
which
suggests
anonly
increase
of the UL
finely
particles
Li: 4.65%),the
which
suggests that
of the finely
particles
is and
is not (maximum
the major leachability
factor thatofinfluence
leachability
ofan
Li.increase
To achieve
a Li ground
extraction
of 90%
not the major factor that influence the leachability of Li. To achieve a Li extraction of 90% and above
above from UL, UL needs to be mixed with SS to at least the weight ratio of 2:1 (SS:UL) and with the
from UL, UL needs to be mixed with SS to at least the weight ratio of 2:1 (SS:UL) and with the
subsequent grinding of this mixture is to be ground for 6 h or more.
subsequent grinding of this mixture is to be ground for 6 h or more.
100
Leachability of Li/ %
80
60
1
1
1
40
0
20
0
3
2
2
3
2
3
0
3210
0
2
lepidolite
1
Na2S : lepidolite (1:1wt%)
2
Na2S : lepidolite (2:1wt%)
3
Na2S : lepidolite (3:1wt%)
0
0
4
6
8
10
12
Grinding Milling time / hr
Figure 3. Leachability of Li from the mixture of sodium sulfide (SS) and lepidolite (UL) with a change
Figure 3. Leachability of Li from the mixture of sodium sulfide (SS) and lepidolite (UL) with a change
of the mixing ratio and grinding time.
of the mixing ratio and grinding time.
4
740
Minerals 2015, 5, 737–743
Minerals 2015, 5, page–page
3.2. Structural Changes of the Mixture (SS and UL) via Intensive Grinding
3.2. Structural Changes of the Mixture (SS and UL) via Intensive Grinding
To verify the grinding effect of the mixture (SS and UL) on leaching, X-ray diffraction (XRD)
analysis
wasthe
performed
the of
ground
mixture
3:1 UL)
(SS:UL).
This analysis
focused(XRD)
on the
To verify
grindingon
effect
the mixture
(SSofand
on leaching,
X-ray was
diffraction
structural
of theon
primary
constituents
in of
the3:1
starting
material,
such as quartz,
muscovite
and
analysis
waschange
performed
the ground
mixture
(SS:UL).
This analysis
was focused
on the
at a mass
ratio muscovite
of 1:3, andand
then,
lepidolite.
The upgraded
lepidolite
(UL) was
with Na
structural
change
of the primary
constituents
in mixed
the starting
material,
as quartz,
2 S (SS)such
the mixture
groundlepidolite
intensively
by using
a planetary
ball2Smill
lepidolite.
Thewas
upgraded
(UL)
was mixed
with Na
(SS)for
at various
a mass periods
ratio of of
1:3,time,
andranging
then,
180 to
600ground
min (Figure
4). by using a planetary ball mill for various periods of time, ranging
thefrom
mixture
was
intensively
Astoshown
in (Figure
Figure 4,
from 180
600 min
4). most peaks of UL in the mixture that were ground for only 3 h, such
as As
quartz,
muscovite
and
lepidolite,
all that
of the
peaks
were for
confirmed
sodium
shown
in Figure
4, most
peaksdisappeared,
of UL in the while
mixture
were
ground
only 3 h,for
such
as
sulfidemuscovite
(Na2 S), sodium
sulfate (Na
No. all
70-1909),
and hydrated
sulfide (Na
(H2 O)5 ,
quartz,
and lepidolite,
disappeared,
while
of the peaks
were confirmed
for2 S¨
sodium
2 SO3 , JCPDs
JCPDs
No.
This (Na
result
structure
UL may
be destroyed
sulfide
(Na
2S), 84-0662).
sodium sulfate
2SOimplies
3, JCPDsthat
No. the
70-1909),
and of
hydrated
sulfide
(Na2S·(H2considerably
O)5, JCPDs
by84-0662).
intensiveThis
grinding
with SS.that
Moreover,
SS may
bemay
partially
oxidizedconsiderably
and hydrated
during the
No.
result implies
the structure
of UL
be destroyed
by intensive
grinding
procedure
in atmosphere
condition.
structural
changes during
of lepidolite
in the XRD
patterns
grinding
with
SS. Moreover,
SS may be
partially The
oxidized
and hydrated
the grinding
procedure
hardly analyzed
low content
of lepidolite
and the
comparatively
higher
in were
atmosphere
condition.due
Thetostructural
changes
of lepidolite
in the
XRD patterns
werecontent
hardlyof
sodiumdue
sulfide.
analyzed
to low content of lepidolite and the comparatively higher content of sodium sulfide.
(d)
S
S
H HS
S
H HS
S
H HS
S
S
S
S
S
(c)
S
S
H
S HH S
S
S
(b)
Intensity (a.u.)
S
H
S HH S
S
H S
SH
S
H
S
S
S
S
(a)
Q Quartz (SiO2)
M Muscovite (K(OH,F2)2Al3Si3O10)
L Lepidolite (KLiAl(OH,F)2Al(SiO4)3
S
S Sodium Sulfide (Na2S)
H Sodium sulfide hydrate (Na2S·5H2O)
S Sodium sulfate (Na2SO3)
S
S
M
M
M
10
20
Q
S
M
M
L
L LL L
S
L L
30
40
L
50
60
70
S
80
2 / ° (Cu-Kα)
Figure
4. 4.
XRD
pattern
of of
thethe
mixture
(UL:SS
= 1:3)
with
thethe
change
of of
thethe
grinding
time,
((a)((a)
only
Figure
XRD
pattern
mixture
(UL:SS
= 1:3)
with
change
grinding
time,
only
mixed;
(b)(b)
3 h;
(c)(c)
6 h;
(d)(d)
1212
h).h).
mixed;
3 h;
6 h;
As mentioned above, to detect the structural changes of UL in the mixture that was ground
As mentioned above, to detect the structural changes of UL in the mixture that was ground
intensively using an XRD analyzer, it is necessary to improve the crystal quality. In this study,
intensively using an XRD analyzer, it is necessary to improve the crystal quality. In this study, thermal
thermal treatment for annealing of the ground mixture was performed ˝at 105 °C for 2 h.
treatment for annealing of the ground mixture was performed at 105 C for 2 h.
In Figure 5, the main peaks of muscovite and lepidolite are summarized. As shown in the figure,
all of the main peaks of muscovite and lepidolite disappeared by grinding for only 3 h. Moreover,
none of their peaks can be detected in the ground mixture annealed at 105 °C. This result implies that
muscovite and lepidolite may be changed to entirely
741 different compounds, and not only simply to
the amorphous state.
5
Minerals 2015, 5, 737–743
In Figure 5, the main peaks of muscovite and lepidolite are summarized. As shown in the figure,
all of the main peaks of muscovite and lepidolite disappeared by grinding for only 3 h. Moreover,
none of their peaks can be detected in the ground mixture annealed at 105 ˝ C. This result implies that
muscovite and lepidolite may be changed to entirely different compounds, and not only simply to
the amorphous state.
Minerals 2015, 5, page–page
Figure 5. The change of the main peaks for lepidolite and muscovite in the mixture (UL:SS = 1:3) at
Figure 5. The change of the main peaks for lepidolite and muscovite in the mixture (UL:SS = 1:3) at
various grinding
grinding times
times ((a)
((a) only
only mixed;
mixed; (b)
(b) 33 h;
h; (c)
(c) 66 h;
h; (d)
(d) 12
12 h;
h; (e)
(e) annealed
annealed with
with the
the mixture
mixture ground
ground
various
for 12
12 h).
h).
for
4. Conclusions
4. Conclusions
Due to the need for new processes capable of recovering lithium from low-graded Li-contained
Due to the need for new processes capable of recovering lithium from low-graded Li-contained
minerals, grinding a mixture of UL and SS under atmospheric conditions using a planetary ball mill
minerals, grinding a mixture of UL and SS under atmospheric conditions using a planetary ball mill
was conducted, and subsequently, the Li in the ground mixture was leached by distilled water at
was conducted, and subsequently, the Li in the ground mixture was leached by distilled water at
room temperature. The following conclusions can be made based on the experimental results.
room temperature. The following conclusions can be made based on the experimental results.
In spite of intensive grinding for 12 h, only 4.53% of Li could be leached by distilled water from
In spite of intensive grinding for 12 h, only 4.53% of Li could be leached by distilled water from
the ground UL. Meanwhile, the leachability increased dramatically with an increase of grinding time
the ground UL. Meanwhile, the leachability increased dramatically with an increase of grinding time
for various mixing ratios of SS to UL. Regarding the ground mixtures (SS:UL) of 1:1 and 2:1,
for various mixing ratios of SS to UL. Regarding the ground mixtures (SS:UL) of 1:1 and 2:1, the
the leachability of Li increased consistently until 6 h, and then, it decreased slightly, even though
leachability of Li increased consistently until 6 h, and then, it decreased slightly, even though the
the grinding proceeded to 12 h. However, the leachability of Li in the ground mixture of 3:1 increased
grinding proceeded to 12 h. However, the leachability of Li in the ground mixture of 3:1 increased
consistently with grinding time, and 93% leachability was accomplished ultimately.
consistently with grinding time, and 93% leachability was accomplished ultimately.
As a result of the analysis of the crystallographic data for the ground mixtures, the
As a result of the analysis of the crystallographic data for the ground mixtures, the Li-contained
Li-contained minerals, such as lepidolite and muscovite, were destructured by intensive grinding
minerals, such as lepidolite and muscovite, were destructured by intensive grinding with SS and were
with SS and were changed entirely to different compounds. This process enables us to accomplish
changed entirely to different compounds. This process enables us to accomplish 93% of Li-leachability
93% of Li-leachability using the water leaching treatment.
using the water leaching treatment.
Acknowledgments: This work was supported by the Energy Efficiency & Resources of the Korea Institute of
Acknowledgments:
This work was
by the Energy
& Resources
the Korea Ministry
Institute of
Energy Technology Evaluation
and supported
Planning (KETEP)
grantedEfficiency
funded by
the Korea of
government
of
Energy
Technology
Evaluation
and Planning and
(KETEP)
granted
funded
byfrom
the Korea
government
of
Knowledge
Economy
(No. 2010T100200203),
by 2014
Research
Grant
Kangwon
NationalMinistry
University
Knowledge Economy (No. 2010T100200203), and by 2014 Research Grant from Kangwon National University
(No. 120140369).
(No.
120140369).
Conflicts of
of Interest:
Interest: The
The authors
authors declare
declare no
no conflict
conflict of
ofinterest.
interest.
Conflicts
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