Lithium recovery from spent Li-ion batteries using coconut shell activated carbon

Lithium recovery from spent Li-ion batteries using coconut shell
activated carbon
Chandra Wahyu Purnomo a,b,⇑
, Endhy Putra Kesuma a
, Indra Perdana a
, Muhammad Aziz c
a
Advanced Material and Sustainable Mineral Processing Research Group, Chemical Engineering Department, Engineering Faculty, Universitas Gadjah Mada, Jl. Grafika no
2, Bulaksumur, Yogyakarta 55281, Indonesia
b
Resource Recovery and Waste Management Center, Agrotechnology Innovation Center PIAT, Gadjah Mada University, Kalitirto, Berbah, Sleman, Yogyakarta 55573, Indonesia
c
Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
a r t i c l e i n f o
Article history:
Received 28 February 2018
Revised 6 August 2018
Accepted 7 August 2018
Keywords:
Column adsorption
Activated carbon
Li-ion recovery
Spent Li-ion battery
a b s t r a c t
Lithium is one of scarce natural resources in the world that need to be preserve. One of the way in pre-
serving the resource is by recovery the rich source of the lithium such as in the spent batteries. It is nec-
essary to develop a recovery method which is efficient and low-cost to be able to recover the lithium in an
economic scale. In this study, low-cost activated carbon (AC) from coconut shell charcoal was prepared
by chemical and physical activation methods and tested for Li removal from Co, Mn, and Ni ions in semi-
continuous columns adsorption experiments. The maximum surface area is 365 m2
/g with the total pore
volume is 0.148 cm3
/g that can be produced by physical activation at 800 °C. In the same activation tem-
perature, activation using KOH has larger ratio of micropore volume than physical activation. Then, the
adsorption capacity and selectivity of metal ions were investigated. A very low adsorption capacity of
AC for Li ions in batch adsorption mode provides an advantage in column applications for separating
Li from other metal ions. The AC sample with chemical activation provided better separation than the
samples with physical activation in the column adsorption method. During a certain period of early
adsorption (lag time), solution collected from the column outlet was found to be rich in Li due to the fast
travel time of this light element, while the other heavier metal ions were mostly retained in the AC bed.
The maximum lag time is 97.3 min with AC by KOH activation at 750 °C.
Ó 2018 Published by Elsevier Ltd.
1. Introduction
The demand for Li-ion batteries significantly increases and
dominates the battery share, especially following the increase of
electric vehicles and electronic products in the market (Meshram
et al., 2015), due to their advantages of high energy density, large
working temperature range, long circle-life, low self-discharging
rate, and high working-voltage (Wang et al., 2016; Jeong et al.,
2015; Aziz et al., 2016). Li-ion batteries are mainly composed of
cathode (Li metal oxide), anode (graphite), electrolyte, separator
(PVDF) and metal casing (Barik et al., 2016). However, as the con-
sequence of this large implementation of Li-ion batteries, huge
amounts of spent Li-ion batteries are generated. On the other hand,
Li is well known as a rare-earth metal having high economic value,
and available mainly in several specific regions, including
Argentina, Bolivia, and Chile. Therefore, the recovery of Li from
the spent batteries has become increasingly important from both
economic and environmental point of views.
Several methods to recover the metal from spent batteries
include metal leaching (Sun and Qiu, 2012; Meshram et al.,
2015), physical separation (Bertuol et al., 2015), mechanochemical
(Tan and Li, 2015), and Co and Li separation (Joulié et al., 2014).
Hydrometallurgy is commonly used to extract metals from spent
batteries (Chen et al., 2015). During the early stage of recovery,
battery electrodes are leached in a strong acid solution, such as
H2SO4 (Meshram et al., 2015), HCL (Guo et al., 2016), succinic (Li
et al., 2015), oxalic (Zeng et al., 2015) and tartaric acids (Nayaka
et al., 2016), to obtain a mixture of metal ions mostly containing
Li, Co, Ni, Mn, and several others, depending on the battery type.
Unfortunately, although these acids lead to relatively good results,
they are corrosive, environmentally polluting, generating liquor
waste, and causing difficult post treatment (Wang et al., 2016;
Pant and Dolker, 2017). In addition, after diluting the metals, the
ion species must be separated and purified by available technolo-
gies such as multistage precipitation, electrodialysis (ED) and
selective adsorption (Tuncuk et al., 2012).
https://doi.org/10.1016/j.wasman.2018.08.017
0956-053X/Ó 2018 Published by Elsevier Ltd.
⇑ Corresponding author at: Chemical Engineering Department, Engineering
Faculty, Universitas Gadjah Mada, Jl. Grafika no 2, Bulaksumur, Yogyakarta 55281,
Indonesia.
E-mail address: chandra.purnomo@ugm.ac.id (C.W. Purnomo).
Waste Management 79 (2018) 454–461
Contents lists available at ScienceDirect
Waste Management
journal homepage: www.elsevier.com/locate/wasman

The conventional precipitation method requires chemicals to
properly adjust the solubility of each component. The method con-
sists of several steps of mixing, heating and filtration and involves
a careful stepwise increase of the pH by the addition of a basic
solution (NaOH or Na2CO3), followed by evaporation and filtration
at every step to precipitate the specific metal ion. Meanwhile, an
ED requires membrane and electric current to separate the ion
mixtures. Thus, the technology is still expensive and prone to
membrane fouling. On the other hand, metal adsorption using acti-
vated carbon (AC) from biomass waste is considered to be an effec-
tive method, especially in acidic environment (Chand et al., 2009).
The recovery of Li ions using various adsorbents has been inves-
tigated mainly for extracting Li from brine (Ooi et al., 2016; Xiao
et al., 2015). The focus of most studies is to produce a novel adsor-
bent whose uptake capacity of Li ions is as high as possible. Some
of the previous efforts have been tested using pure Li solution to
observe the performance of the adsorbents (Jeong et al., 2015;
Zhang et al., 2016). Li is a light element that is quite difficult to
be physically adsorbed, compared to other possible metal ions pre-
sent in brine or spent Li-ion battery leachate solutions. Commonly,
the interaction between Li ion and the adsorbent surface is the
weakest among the other present metal ions. To enhance the
uptake of Li ion from solution, some advanced materials have been
prepared as adsorbents (Xiao et al., 2015; Lemaire et al., 2012).
However, it should be kept in mind that the proposed Li adsorbents
have only been tested in single-ion solutions. Therefore, these
methods may have the drawback of stronger affinity towards other
metals when applied in a multicomponent metal ion solution. If
this is the case, the separation effect of Li from other metals will
not be attained.
In this study, to answer the above-mentioned problems, a novel
column adsorption method to separate Li from other dissolved
metal ions was developed. The success of the separation depends
on the adsorbent, whose adsorption affinity for Li should be greatly
different from that for other metal ions. The adsorption experi-
ments were carried out using a synthetic leaching solution con-
taining Li, Mn, Ni, and Co ions. In addition, a Li-ion battery
electrode leaching solution was also used after understanding the
sorption behavior of the adsorbent in the preliminary batch tests.
In the present work, an AC from the low-cost precursor of coco-
nut shell charcoal was selected as adsorbent. AC is considered as an
effective adsorbent mainly due to its large surface area and good
adsorption capability. Unfortunately, high production cost gener-
ally becomes barrier in its adoption; therefore, a low cost AC is
extremely encouraged. AC from coconut shell charcoal has been
adopted for several separation/adsorption processes, including Ni
(Jeong et al., 2015), phenol (Karri et al., 2017), benzene, toluene
(Mohammed et al., 2015), sulfamethoxazole (Tonucci et al.,
2015), and Pb (Kaccin et al., 2015). However, to the best of authors’
knowledge, there is no study dealing with the effort to utilize this
kind of AC for Li recovery. In this study, the coconut shell charcoal
was activated to enhance its sorption affinity for heavy metal ions
(Co, Mn and Ni), while the affinity remained low for Li ions. Such
modification was achieved by varying the activation method and
temperature to obtain the unique properties of AC. The column
adsorption method using the prepared AC aimed at producing a
Li-rich solution separated from the leachate mixture of a spent
Li-ion battery, which then underwent precipitation to produce
high purity Li2CO3 powder. Meanwhile, the other metal ions
remained on the adsorbent for further recovery or desorption pro-
cesses. Thus, the objective of this study is to develop an efficient
way for lithium ion recovery by an innovative adsorption column
method instead of focusing on the expensive selective adsorbent
preparation.
2. Experiments
2.1. AC preparation
Coconut shell char flakes collected from a local charcoal factory
were crushed and then sieved to obtain 6–8 mesh (large) and 9–14
mesh (small) fractions, which were stored separately. Furthermore,
a portion of the chars was activated by the CO2 physical activation
and KOH chemical activation method. The detail of activation pro-
cedures follows a previous report by Purnomo et al. (2012). Typi-
cally for physical activation, the process used a temperature
variation from 700 to 800 °C in a programmable horizontal tube
furnace with increase rate of 20 °C/min under CO2 gas with a flow-
rate of 2 ml/min. A 35 cm long alumina tube with an external
diameter of 2.5 cm was used as the char holder during the activa-
tion. The char was packed 10 cm long in the middle of the tube
with the aid of ceramic wool. The activated char was then washed
with deionized water to remove small debris created during the
preparation stages that may interfere with the adsorption result,
dried in an oven and eventually stored in a sealed container.
Another portion of the prepared coconut shell charcoal was
chemically activated using 10 wt% KOH. The char that was treated
with the KOH solution was then dried and activated in the same
horizontal tube furnace at two temperatures of 700 and 750 °C.
Nitrogen was flown through the tube at 2 ml/min during tempera-
ture ramp. Once the maximum temperature was reached, the
atmosphere was changed to CO2 (2 ml/min), and the temperature
was kept constant for 1 h. After cooling to ambient temperature,
the ACs were washed and filtered with deionized water until the
filtrate reached a neutral pH. The carbons were then dried in an
oven and stored. The samples with different activation methods
are coded as listed in Table 1.
2.2. AC characterization
The porosity of the prepared carbon samples was analyzed
using a Surface Area Analyzer (NOVA 2000, Quantachrome). The
surface morphology of char samples before and after activation
was observed by SEM (JSM 6510LA, JEOL). For investigating the
Nomenclature
Cout column outlet concentration
Cin initial concentration
t adsorption time
t0:5 breakthrough time
t2
0:5 breakthrough time of the second ion to appear
tlag lag time
Table 1
ACs sample identification.
ID Activation method Activation temp. (°C)
CC NA NA
AC700 Physical 700
AC750 Physical 750
AC800 Physical 800
AC700OH Chemical 700
AC750OH Chemical 750
C.W. Purnomo et al. / Waste Management 79 (2018) 454–461 455

chemical characteristic of the carbon, FTIR (IR-Prestige-21, Shi-
madzu) was used. The determination of pHPZC (point of zero
charge) was carried out following the method of Noh and
Schwarz (1989).
2.3. Spent battery leachate preparation
The adsorption performance of ACs was tested using a real
Li-ion battery electrode leaching solution. The acid solution for
diluting the metal content in spent Li-ion battery electrodes was
prepared using concentrated H2SO4 and H2O2. In a typical prepara-
tion, the separated electrode powder scrapped from the disman-
tled cathode layer of spent Li-ion batteries was calcined at 700 °C
for 4 h for removing the carbon content that may hinder acid
leaching process i.e. re-adsorb the leached metal ion. Calcination
temperature of 700 °C was determined based on the thermo gravi-
metric analysis (TGA) result which revealed that the carbon
removal occurred at 490–630 °C, while the calcination time was
set by visual inspection of the powder color changes from black
to grayish with no further change after 4 h of heating in the
furnace. The acid solution was prepared by mixing 2 M H2SO4 with
2 vol% H2O2 to obtain 250 ml of leaching agent solution. Then, the
solution was added to a triple-necked flask and heated to 60 °C.
Next, 9 g of the calcined cathode powder was poured into the flask
and stirred for 2 h. The leachate was collected after filtering the
mixture. In this study, only Li, Co, Mn and Ni ions were considered
in the adsorption experiments. The prepared leaching solution had
a different concentration of each metal ion, i.e., 2022 ppm Li+
,
2644 ppm Co2+
, 5282 ppm Mn2+
, and 4664 ppm Ni2+
. Before being
used in the adsorption experiments, the leachate was diluted 20
times with deionized water resulting a dilute muti-ionic solution
with pH at around 5.2.
2.4. Column adsorption
The adsorption experiments were normally conducted using
small particle size AC (9–14 mesh), unless otherwise mentioned.
The adsorption equilibrium for each carbon sample after a certain
time was measured by collecting the filtrate of a particular flask
and analyzed using ICP-OES (Optima 8300, Perkin Elmer).
For column adsorption, a glass column with a diameter of 2 cm
was used. The glass column was filled with adsorbent, using the
same weight for each experimental run. The adsorbent was packed
inside the column by manual compacting to a measured height of
approximately 60 cm. The synthetic solution or the real leachate
solution was flown from the top of the column using a pro-
grammable microsyringe with a specific flowrate from 1 to 3 ml/min.
The solution passed through the bed by gravitational flow, and
the liquid product was collected at the bottom of the column for
subsequent analyses. Each adsorption column experiment was
run for 2 h.
The column adsorption breakthrough curve was modeled using
a simple linear equation (Eq. (1)) proposed by Yoon and Nelson
(1984). The column outlet concentration (Cout) is only a function
of the adsorption time (t) with two constants (a and b), which
can be determined by fitting the experimental data. By assuming
that the breakthrough time (t0:5) is the time to reach 50% of the ini-
tial concentration (Cin), a much simpler equation can be obtained
(Eq. (2)). A new definition of lag time (tlag) is also proposed, which
is simply the breakthrough time of the second ion to appear
t2
0:5
À Á
;as represented by Eq. (3). It is important to determine the
lag time because during this time period, the solution rich in the
first ion to appear can be obtained, which is the main goal of this
study. Meanwhile, the ratio of Cout to Cin can be determined using
Eq. (4), which can be fit by the experimental data.
ln
Cout
Cin À Cout
¼ a:t À b ð1Þ
t0:5 ¼
b
a
ð2Þ
tlag ¼ t2
0:5 ¼
b2
a2

ð3Þ
Cout
Cin
¼
eatÀb
1 þ eatÀb
ð4Þ
The collected Li-rich solution at a particular time from the
adsorption column was further treated. A volume of 15 ml of the
Li-rich solution was heated at 90 °C, and then, before all the water
evaporated, a specific volume of Na2CO3 solution was added to pre-
cipitate Li2CO3. The volume and concentration of the added Na2CO3
solution was previously calculated in order to provide a double sto-
ichiometric demand for Li2CO3 precipitation. After separation and
drying, the collected powder was analyzed using EDX (EDX-8000,
Shimadzu).
3. Results and discussion
The AC used in the present study underwent two different acti-
vation methods, which lead to different properties. After prepara-
tion, AC was then used as packing bed in an adsorption column.
The materials characteristics and column performance of the pre-
pared samples will be discussed in the following section.
3.1. Properties of ACs
Table 2 shows the porosity of the prepared AC samples. The
activation can significantly increase the porosity inside the parent
char with the maximum surface area is 365 m2
/g with the highest
treatment temperature (800 °C). In general, a higher activation
temperature creates a larger surface area. Comparing the two dif-
ferent activation procedures, a chemical activation can induce
higher portion of micropores inside the carbon precursor than a
physical activation especially in higher temperature with the high-
est ratio of micropore with total pores of 83.4% for activation using
750 °C with KOH. CO2 gas, as the activating agent, consumes the
carbon on the surface of the carbonaceous precursor and creates
pores of various sizes. Meanwhile, wet impregnation pretreatment
with KOH can penetrate precursor particles more deeply through
the initial available pores, leading to the formation of new micro-
pores during the activation. The ability of KOH in penetrating the
parent carbon has been confirmed in several studies in which
higher concentration and long impregnation time will have greater
impact to porosity development (Alslaibi et al., 2013; Purnomo
et al., 2018). The micropore volume generated from KOH activation
is higher than that generated from CO2 activation at the same acti-
vation temperature, which was also documented elsewhere
(Purnomo et al., 2012).
Meanwhile, from pHZPC measurement, all the activation will
increase the surface basicity of the char. KOH activation will fur-
ther increase the pHZPC than CO2 activation. The high pHZPC mate-
rial tends to create positively charged surface whenever in contact
with a solution at lower pH. Thus indeed, the positively charged AC
surface is not favorable for adsorbing cations. The separation
mechanism then just rely on the physical properties of the carbon
i.e. surface area and pore size.
SEM image of the carbon surface (Fig. 1) shows that the
untreated char (CC) has layered surface with very low number of
pore entrance. The small debris of materials can be seen across
the surface that may hinder the adsorbate transfer from the
456 C.W. Purnomo et al. / Waste Management 79 (2018) 454–461

solution to the carbon cores. By both activation methods, the
numerous pore opening can be observed on the AC surface. The small
loose particles has been removed from the outer surface remaining
a relatively clean surface ready for adsorption. This might be due to
the washing procedure after heat treatment during the activation.
In order to understand the carbon surface chemistry, FTIR spec-
trogram has been collected and presented in Fig. 2. In general, from
the weak transmittance of all peaks, it can be said that the carbon
samples, either untreated or activated, have very few and low con-
centration of functional groups. Only phenyl (O-H) functional
group at 3400 cmÀ1
that can be recognized, while the other com-
mon functional group such as carbonyl (C@O) is missing. KOH acti-
vation will remove phenyl functional group from the surface, as
shown by AC750OH spectra in contrast aromatic double bond
peaks which is slightly enhanced. This peak improvement at about
1500 cmÀ1
can be a sign of aromatization of carbon due to the heat
treatment during activation. Phenyl is acidic in nature, thus by
removal of this group, it can be expected that the surface of the
carbon become more basic that is in line with the pHZPC results
(Table 2). This kind of high pHZPC carbons will only rely on surface
area and porosity when adsorbing the cations. The reduction of
major IR peak intensity after the activation using KOH has also
been reported previously (Alslaibi et al., 2013; Purnomo et al.,
2018).
Meanwhile, the utilization of AC to separate Li ion in the litera-
ture is scarce. Since Li is a light element, separation based on
adsorption from liquid system is not considered to be a feasible
option. Table 3 provides a brief literature review of some previous
studies related to the applications of AC for Li recovery. The
adsorption data show that the uptake capacity of Li is very low
in any AC-based adsorbent, less than 10 mg/g. This information
indicates how difﬁcult it is to recover Li from an aqueous solution
Fig. 2. FTIR spectrogram of selected samples.Fig. 1. SEM image of selected samples.
Table 2
Porosity of AC samples.
ID BET surface area, m2
/g Micropore volume (Vmic), cm3
/g Total volume (Vtot), cm3
/g Ratio Vmic/Vtot, % pHzpc
CC 12 0.004 0.029 13.8 8.4
AC700 181 0.089 0.118 75.4 8.6
AC750 210 0.107 0.146 73.2 8.8
AC800 365 0.117 0.148 79.0 9.0
AC700OH 135 0.070 0.089 78.6 10.0
AC750OH 265 0.116 0.139 83.4 10.1

by adsorption using carbon. The difficulty will increase if other
metal ions are also present in the solution, which causes selectivity
problems. Most ACs have much stronger uptake capacity for other
precious metal ions that may be contained in the electrodes of Li-
ion batteries, such as Co(II) at 405 mg/g (Kyzas et al., 2016), Mn(II)
at 172 mg/g (Omri and Benzina, 2012), and Ni(II) at 16 mg/g (Gao
et al., 2013).
The same prepared adsorbents, i.e. activated carbon from coco-
nut char, have been reported to be used for separating Li ions in
prepared multi-ionic solution using batch method adsorption. In
brief, this report suggests two important findings: the first is the
low adsorption capacity of Li ions and the second was the adsorp-
tion of Co(II) which will be adsorbed more by the AC samples than
Li ions, and the gap between these two ion uptakes is even wider
for AC with KOH activation (Purnomo et al., 2017). In line with
other previous results that the untreated activated carbon has very
weak Li ions adsorption capacity and can be enhanced by chemical
treatments for generating oxygen-functional groups on the carbon
surface (Jeong et al., 2015). Furthermore, in some cases of raw acti-
vated carbon, the sorption of Li ions did not occur due to positively
charged surface creating repulsion of Li ion. Chemical post-
treatment of activated carbon will create functional group on the
surface and the possible reaction mechanism of Li ions adsorption
is proton exchange from the surface acidic groups (carboxylic or
phenolic) with Li ion (Frackowiak, 1998).
FTIR results (Fig. 2) shows low concentration of oxygen func-
tional group on the surface and pHZPC (Table 2) indicates positively
charged surface of the prepared carbons in neutral or acidic solu-
tion. All of these surface chemistry characteristics are unfavorable
for Li ion chemical adsorption and the only mechanism left is phys-
ical adsorption which depends on the surface area of the adsorbent
and also the atomic radius of the adsorbate (cations), called as Van
der Waals attraction. Since the Li ions is the smallest particle, the
attraction with the carbon on the surface is expected to be the low-
est compared with other larger size cations.
In another word, the batch adsorption results indicate that the
adsorbents are not selective towards the mixture ions (Co, Li, and
Mn), all cations will be adsorbed but in different capacities. How-
ever, the difference in uptake capacity among the ions can be uti-
lized for separation in a continuous adsorption system through an
adsorbent column. Species with lower affinity for the adsorption
medium will travel faster through the adsorbent bed than the
other ions, thus allowing for the separation of the different
components.
3.2. Column adsorption experiment
In the column adsorption experiment, AC was packed inside the
column, and the multicomponent ionic solution was flown through
the bed from the top of the column, while the treated solution was
collected at the bottom of the column. Cin in the column feed was
compared with Cout after a certain time. A synthetic leaching solu-
tion was used to obtain preliminary results of the adsorption col-
umn, as shown in Fig. 2.
As shown in Fig. 3(a), the untreated coconut shell char does not
separate the components in the solution. The reason for the lack of
separation could be the very low surface area or adsorption capac-
ity of the untreated coconut shell char. Meanwhile, for the acti-
vated char (AC750), the segregation of the cations is clearly
visible, as shown in Fig. 3(b). The gap of the highest ion concentra-
tion ratio with the other ions is ranged from 70% in the beginning
and about 40% at the end. The ions cannot be excluded completely
since from the beginning all the ions has its initial concentration.
As expected, Li dominates the concentration of the output solution
at the early stage of adsorption. The concentration sequence of
cations from the highest to the lowest follows the atomic mass
order. Species with lower atomic mass travel through the adsor-
bent bed faster, resulting in a higher outlet concentration of those
component, and vice versa.
The acid leaching solution of Li-ion battery electrodes is more
stringent than the synthetic solution, due to the more diverse ion
composition, higher concentration and acidity. The leachate solu-
tion was diluted 20 times before being used, and thus, the concen-
trations of Li(I), Co(II), Mn(II) and Ni(II) were 101.1 ppm, 132.2
ppm, 264.1 ppm, and 233.2 ppm respectively, while the solution
pH was 5.1. Because of these properties, the column adsorption
experiments using a real leaching solution were mostly conducted
at an input flowrate of 1 ml/min, unless otherwise stated. It is
Table 3
Previous literatures data on ACs as metal ion adsorbents.
Carbon precursor Activating/modifying agent Adsorption mechanism Maximum uptake capacity (mg/g) Ref.
Commercial activated charcoal H3PO4 Batch 6.0 Jeong et al. (2015)
KOH 8.7
Activated charcoal NA Batch 2.5 Favin et al. (1988)
Commercial AC nitric acid Column 5.4 Kam et al. (2014)
Commercial AC NA Electrosorption 1.1 Dodbiba et al. (2014)
(b)(a)
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Mn
Co
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Mn
Co
Ni
Fig. 3. Adsorption profiles using a synthetic solution with a flowrate of 2 ml/min: (a) untreated coconut shell char; (b) the activated coconut shell char AC750.

known that using a lower flowrate for a column test will result in
the better segregation of components after passing the adsorbent
bed.
Fig. 4 shows the column adsorption experiment results for
selected AC samples using the leaching solution. It can be seen that
the total separation effect can occur in which Li ion can be sepa-
rated from others in a certain period of time. In other word, there
is a time when the solution coming out from the column free from
ions other than Li. The separation effect of the AC samples with
physical activation follows the porosity of the materials. The sepa-
ration of cations is better for AC with a larger surface area. The lag
time, defined as the time between the first appearance of Li in the
outlet solution and that of another ion (breakthrough curve) in the
solution, increase for larger surface area AC samples. Determining
this lag time is important to obtain a Li-rich solution.
Pure Li can be obtained from the product at the bottom of the
column during the lag time, whose duration varies from 10 min
(AC700) to approximately 60 min (AC750OH). The AC sample with
chemical activation has a longer lag time, which was expected
from the batch adsorption experiment discussed above. However,
during the lag time of AC750OH, the Li-ion concentration is still
low compared with that of the AC samples with physical activa-
tion. Thus, there may be a tradeoff between longer lag time and
higher Li-ion concentration. Thus, the optimum result can be
achieved by adjusting the adsorbent properties and operating con-
ditions, such as the liquid flowrate.
The flowrate is an important variable for shifting the break-
through time, as indicated in Fig. 5. If the flowrate is increased,
the lag time will decrease from about 28 min to less than 6 min,
and then the measured concentration of each component in the
(b)(a)
(d)(c)
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Co
Mn
Ni
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Co
Mn
Ni
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Co
Mn
Ni
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Co
Mn
Ni
Fig. 4. Adsorption breakthrough curves of the activated char samples using a leachate solution at 1 ml/min: (a) AC700; (b) AC750; (c) AC800; (d) AC750OH.
(b)(a)
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Co
Mn
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Co
Mn
Fig. 5. Adsorption breakthrough curves of activated char samples of AC800 using different leachate solutions flowrates: (a) 2 ml/min; (b) 3 ml/min.

column outlet will increase more rapidly. A similar effect can also
be obtained by shortening the length of the carbon bed.
Meanwhile, the grain size of the adsorbent will also affect the
velocity at which the liquid flows through the bed in the column.
Larger grains allow the liquid to move faster through the packed
bed without proper separation, because the larger grain adsorbent
will create larger void spaces for liquid to flow freely. As indicated
in Fig. 6, the lag time significantly decreases when larger adsorbent
particles are used (6–8 mesh). The effect of particle size is detri-
mental for the separation ability of the column. However, if the
lag time is significantly reduced, a Li-rich solution is difficult to
be obtained. Larger particles provide larger voids among the parti-
cles. This causes the treated liquid to be channeled throughout the
bed, resulting in insufficient retention time for separation.
The adsorption breakthrough curves from the experimental
data and simulations are compared, as shown in Fig. 7. In the cal-
culation, data fitting and tlag are sensitive to the values of the con-
stants. The constants (a and b) should be determined carefully at
the steep slope of the breakthrough time region. The R2
value
should be higher than 0.9, otherwise the calculated time lag is
too far from that of the experimental data. The calculated time lags
of all variations are listed in Table 4. In general, lowering the flow-
rate can increase the lag time. Meanwhile, the collected volume of
the Li-rich solution is equal to tlag multiplied by the flowrate; thus,
there may be an optimum flowrate to achieve the highest volume
of Li-rich solution.
The output liquid from the adsorption column during the lag
time was collected and precipitated using Na2CO3, taking advan-
tage of the very low solubility of Li2CO3. The result of the EDX anal-
ysis of the powder is listed in Table 5. It should be noted that Li
cannot be detected using EDX because this equipment can only
detect elements heavier than carbon. This analysis was performed
only for detecting impurities in the powder. As shown in Table 3,
the impurity of the powder is mainly related to the excess addition
of sodium carbonate during precipitation. Moreover, Mn is still
detected even at a very low amount, while Co and Ni are
undetected.
4. Conclusions
AC from low cost coconut shell charcoal is very potential be
used for separating Li from a multicomponent ionic solution using
the column adsorption method. The low Li uptake capacity of the
adsorbent can be utilized to obtain a Li-rich solution using a
semi-continuous packed bed adsorption column. The chemical
activation by KOH can create porosity inside the parent char, which
is suitable for adsorbing other precious metals, leaving most of the
Li ions remaining in the solution. By varying the adsorbent
porosity, liquid flowrate and adsorbent grain size in the adsorption
(b)(a)
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Mn
Co
Ni
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100 120
Cout/Cin
Ɵme, min
Li
Co
Mn
Ni
Fig. 6. Adsorption breakthrough curves of the large particle (6–8 mesh) activated char samples: (a) AC750; (b) AC750OH.
0
0.5
1
0 20 40 60 80 100
Cout/Cin
Ɵme, min
Li-data
Li-equaƟon
Mn-data
Mn-equaƟon
Fig. 7. Simulated breakthrough curve and tlag indication of AC700 using the
leaching solution.
Table 4
Calculated tlag for various column adsorption condition.
ID Inlet flow rate, ml/min Particle size Calculated tlag, min
AC700 1 Small 18.56
AC750 1 Small 29.46
1 Large 7.63
AC800 1 Small 63.27
2 Small 28.83
3 Small 5.08
AC750OH 1 Small 97.13
1 Large 23.41
Table 5
EDX analysis of the precipitated powder.
Element Content, wt%
MnO 0.08
Na2O 53.52
K2O 17.66
SiO2 12.93
SO3 11.48
P2O5 1.12
CuO 0.20
FeO 0.08
MgO 1.02
Al2O3 1.79
SeO3 0.06

column, the separation of Li ion from other metal ions from the
spent battery leaching solution can be maximized. The new terms
of lag time (tlag) was introduced in this study to represent how long
Li-ion rich solution can be obtained by using column adsorbent
before being contaminated with the other ions. The longest lag
time can reach up to 97 min using the process condition in this
study. A packing that can provides longer lag time is considered
better adsorbent in this application.
Acknowledgement
The financial support from Lithium Recovery from Spent Li-ion
Battery Project under LPDP Grant 2015 The Ministry of Finance
Indonesia is greatly appreciated. A sincere gratitude is also
addressed to Dr. Daniele Castello for his precious suggestion during
this manuscript preparation. We also gratefully acknowledge the
funding from USAID through the SHERA program – Centre for
Development of Sustainable Region (CDSR).
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