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Simultaneous recovery of Ni and Co from scrap mobile phone battery by acid leaching process.

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ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING
Asia-Pac. J. Chem. Eng. 2008; 3: 374–379
Published online 9 July 2008 in Wiley InterScience
(www.interscience.wiley.com) DOI:10.1002/apj.158
Research Article
Simultaneous recovery of Ni and Co from scrap mobile
phone battery by acid leaching process
S. Sakultung, K. Pruksathorn and M. Hunsom*
Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
Received 10 October 2007; Revised 11 February 2008; Accepted 14 February 2008
ABSTRACT: This research was carried out to recover some valuable metals from the electrodes of the scrap mobile
phone batteries by using the leaching process in the laboratory. Two types of scrap mobile phone batteries were used
in this study: nickel-metal hydride (Ni–MH) and lithium-ion batteries (Li–ion). Both batteries were first crushed and
their principal components were analyzed. Subsequently leaching was carried out. For simultaneous recovery of both
metals, the preliminary results indicated that H2 SO4 provided better leaching than HNO3 under the same conditions.
The optimum leaching was at an acid concentration of 2.5 M, leaching temperature of 70 ◦ C, solid–liquid ratio of
15 g/l, and leaching time of 60 min. Under these conditions, approximately 95% of nickel (Ni) and 59% of cobalt (Co)
were leached. The presence of a reducing agent such as H2 O2 had very little effect on the leaching efficiency of both
metals. The leaching process of both the metals was a second-order reaction of the metal concentration in the solution.
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
KEYWORDS: scrap mobile phone battery; acid leaching process; Ni–MH and Li-ion batteries
INTRODUCTION
Owing to the development of industry and communication, the demand for cellular or mobile phones has
greatly increased, leading to an increase of scrap batteries. In the last few years, the market for lithium-ion
(Li-ion) and Li-polymer cells has increased from 8.4
to 27.3% while that of nickel–cadmium (Ni–Cd) batteries has decreased from 63.8 to 44.4% and that of
nickel–metal hydride (Ni–MH) remained practically
constant.[1] Currently Li-ion batteries represent approximately 28% of the world market and their consumption
is increasing, particularly in small rechargeable cells
such as used in mobile phones. According to the report
prepared by the Foundation for Anti Air Pollution and
Environmental Protection, the number of mobile phones
will increase rapidly to more than 20 million in 2008
and this increase will release over 10 million scrap batteries during the same period. These scrap batteries are
Li-ion, Ni–MH, Li–polymer, and Ni–Cd, etc. Disposing of these batteries without proper discharging will
lead to serious problems in the future because they usually contain some heavy metals, particularly nickel (Ni),
manganese (Mn), iron (Fe), copper (Cu), cobalt (Co)
and sometimes cadmium (Cd) or mercury (Hg).[2] At
*Correspondence to: M. Hunsom, Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok
10330, Thailand. E-mail: mali.h@chula.ac.th
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
present, sanitary landfills are used for disposal of such
wastes. However, this procedure may generate various
sequent problems in the future such as leakage of heavy
metals into the environment. Therefore, their recovery
and reuse will be the alternative procedure from both
environmental and economic perspectives. Many techniques were introduced to recover and recycle valuable
metals from scrap batteries. All previous works started
with acid leaching technique to dissolve solid metal into
aqueous solution. The best condition for acid leaching
was with 3 M HCl at the high temperature of 95 ◦ C and
3-h leaching time.[3] For Ni–Cd battery, Zhu et al .[4]
used the bioleaching process to remove Ni and Cd.
This showed that acid leaching was most effective at
the residence time of 4 days of the sludge in the bioreactor, which satisfied the requirement of environmental
protection agencies with regard to agricultural use. To
separate Ni from Cd, a combined process of electrodeposition and chemical precipitation was carried out.[5]
In the chemical precipitation process, more than 97%
of Ni element was recovered from the leaching solution by using NaOH. In electrodeposition process, the
appropriate potential for Cd recovery was in the range
of 1100–1120 mV with 70–90% recovery. For Li-ion
battery, 10 M NaOH showed the greatest precipitation
of Co and Ni from the leaching solution.[6,7] To separate Co and Ni, first Co was removed from the aqueous
solution by solvent extraction, after which nickel was
Asia-Pacific Journal of Chemical Engineering
RECOVERY OF NI AND CO FROM MOBILE PHONE BATTERIES
removed as a solid by electrowinning process at a current density of 250 A/m2 with 87% current efficiency
and 2.96 kWh/kg energy consumption.[8] To remove
Ni–Co as alloy, the electrowinning process was carried
out at a current density of 250 A/m2 with pH = 4.3 at
50 ◦ C.[9] The current efficiency was higher than 91%
and good quality alloy was obtained with a composition of Ni (35%)–wCo (40%). The removal of Cd from
scrap Ni–Cd batteries by using electrodeposition was
also carried out galvanostatically.[10] The result showed
that charge efficiency and deposit morphology depended
on the current density, whereas the pore size decreased
with the increase of current density. Salgado et al .[11]
used the liquid–liquid extraction technique to extract
zinc (Zn) and magnesium (Mn) from scrap alkaline batteries in bench scale. The results show that Zn and Mn
are easily separated (pH1/2 ≈ 2.0) using 20% (v/v)
Cyanex 272 in Escaid 110 at 50 ◦ C.
In this work, effects of parameters including types of
acid, leaching time, leaching temperature, acid concentration, and solid–liquid ratio on the Ni and Co leaching
percentages were investigated.
H2O out
Stirrer
Thermometer
Condenser
H2O in
Heater
Figure 1. Schematic diagram of the
experimental set-up.
material were traced by using the atomic absorption
spectroscopy (Avanta ).
RESULTS AND DISCUSSION
Composition of Ni-MH and Li-ion battery
EXPERIMENTS
Two types of scrap mobile phone batteries consisting
of Ni-MH and Li-ion batteries were included in this
study. Both were first opened and classified, based
on appearance, into four categories, namely, electrode,
metal case, plastic case, and other components. The
electrode parts containing valuable metals was used
for further study. It was crushed to a particle size
lower than 2 mm and then dried at 110 ◦ C for 2 h
to eliminate free moisture. The metal components in
the crushed electrodes were subjected to quantitative
analysis by X-ray fluorescence spectroscopy (XRF).
Two metals, Ni and Co in the electrodes of both
batteries, were extracted from the crushed electrode
particles by the acid leaching process. Figure 1 displays
the configuration of the leaching reactor. It consists of
a spherical glass reactor immersed in a water bath. The
temperature of the water bath was maintained constant
at the desired values by an automatic temperature
controller (AT Thermostat, CT52). The homogeneity of
the system was ensured by using a magnetic stirrer
(Model IKA, RW 20 N) with a rotating speed of
100 rpm. The condenser was connected to the top of
the glass reactor to collect the vapor generated in the
system. During the leaching process, the effects of
different parameters including types of acid like H2 SO4
(95%, Carlo Erba) and HNO3 (69%, Carlo Erba), acid
concentration (1–5 M), leaching time (15–120 min),
leaching temperature (30–90 ◦ C), and solid–liquid ratio
(5–40 g/l), on the leaching efficiency were investigated.
The amounts of metal leached from the electrode
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Classification on appearance showed that the main composition of scrap mobile phone batteries can be sorted
into four categories; electrode, metal case, plastic case,
and other components. The Ni-MH battery (Fig. 2(a)),
consisted of 60.96% electrode, 22.81% metal case,
8.10% plastic case, and 7.14% other components. On
the other hand, the Li-ion battery is composed of
50.67% electrode, 32.78% metal case, 9.65% plastic
case, and 5.96% other components (Fig. 2(b)). The
above results show that a Ni-MH battery seems to contain a higher amount of electrode but a lower amount of
metal case than the Li-ion battery. Figure 3 shows the
metal composition in the electrodes of both the batteries.
The Ni-MH battery consisted of 54.20% Ni, 9.15% lanthanum (La), 8.78% Co, 3.27% Cerium (Ce), 2.08% Zn
and 22.52% other metals. The Li-ion battery, contained
55.11% Co, 8.32% Cu, 6.68% Ni, 5.31% aluminum
(Al), 3.67% lithium (Li), and about 20.91% other metals. From this study, it can be seen that scrap mobile
phone batteries contain various kinds of valuable heavy
metals such as nickel, cobalt, and copper. Therefore,
metal recovery from these scrap batteries becomes more
interesting.
Effects of various parameters on the leaching
process
The leaching process was carried out by using mixed
electrodes of both batteries, which contained Ni, Co,
Cu, La, Al, and others, approximately 31.39, 30.53,
Asia-Pac. J. Chem. Eng. 2008; 3: 374–379
DOI: 10.1002/apj
375
376
S. SAKULTUNG, K. PRUKSATHORN AND M. HUNSOM
(a)
Asia-Pacific Journal of Chemical Engineering
(b)
Figure 2. Principal compositions of scrap batteries. Ni-MH (a) and Li-ion batteries (b).
(a)
(b)
Figure 3. Metal compositions in the electrode of scrap mobile phone battery. Ni-MH battery
(a) and Li-ion battery (b).
5.26, 4.70, 2.06, and 26.12%, respectively. Only the
recovery percentage of Co and Ni were traced here.
Effect of types of acid
Two types of acid including H2 SO4 and HNO3 were
employed to leach Ni and Co from scrap mobile phone
batteries at eight different conditions (Table 1) for 2 h
leaching time. The recovery percentage of both Ni
and Co at different operating conditions (showed in
Fig. 4) demonstrated that both types of acid provided
similar recovery percentage for Ni. For Co, at all
operating conditions, however, H2 SO4 provided a better
leaching performance than HNO3 . Furthermore, under
the same conditions, the recovery percentage of Ni
was about two-fold higher than that of Co. This is
because the dissolution constant of H2 SO4 is larger than
that of HNO3 , namely, 1000 and 28, respectively.[12]
Therefore, for simultaneous removal of both metals,
H2 SO4 was selected for further studies.
Effect of acid concentration
The effect of H2 SO4 concentration was explored in
the range of 1–5 M at a leaching temperature of
80 ◦ C, solid–liquid ratio of 10 g/l and leaching time
of 120 min. The results showed that the recovery
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Table 1. Condition of acid leaching process.
Condition
1
2
3
4
5
6
7
8
Temp
(◦ C)
Acid
concentration
(M)
Solid–liquid
ratio
(g/l)
Time
(min)
40
80
40
80
40
80
40
80
1
1
5
5
1
1
5
5
10
10
10
10
40
40
40
40
120
120
120
120
120
120
120
120
percentage of both metals increased with increase of
acid concentration (Fig. 5). It can be explained that
increase in acid concentration led to the increase in the
number of acid molecules getting attached to the metal
molecules. However, an acid concentration greater than
2.5 M had no effect on the leaching efficiencies of both
metals due to the equilibrium limitation of the leaching
process. Results show that the maximum recovery
percentage of Ni was close to 92% when using an acid
concentration of 2.5 M. Similarly, the optimum acid
concentration for leaching Co was found to be 2.5 M
Asia-Pac. J. Chem. Eng. 2008; 3: 374–379
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
RECOVERY OF NI AND CO FROM MOBILE PHONE BATTERIES
80
80
Co recovery (%)
(b) 100
Ni recovery (%)
(a) 100
60
40
20
60
40
20
0
0
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[1]
[2]
[3]
Condition
[4]
[5]
[6]
[7]
[8]
Condition
100
100
80
80
Metal recovery (%)
Metal recovery (%)
Figure 4. Recovery percentage of Ni (a) and Co (b) by using H2 SO4 () and HNO3 .().
60
40
60
40
20
20
0
0
1
2
3
4
H2SO4 concentration (M)
5
Figure 5.
Recovery percentage of Ni
() and Co ( ) as a function of acid
concentration.
°
which provided a maximum recovery of 58%. Hence
the optimum acid concentration to extract both metals
simultaneously was found to be 2.5 M.
Effect of leaching temperature
Figure 6 shows the alteration of recovery percentage of
Ni and Co as a function of leaching temperature in the
range of 30–90 ◦ C by using a concentration of 2.5 M of
H2 SO4 , solid–liquid ratio of 10 g/l and leaching time
of 120 min. The results show that the recovery percentage increases as a function of leaching temperature up
to 70 ◦ C. This is because the high temperature condition can increase the kinetic energy of acid molecules
getting attached to the metal molecules. On the other
hand, further increase of leaching temperature (exceeding 70 ◦ C) cannot achieve a higher recovery percentage.
This is because H2 SO4 dissociates from SO2 at a temperature greater than 80 ◦ C. Hence, to leach both Ni and
Co simultaneously, the optimum temperature was found
to be approximately 70 ◦ C. The recovery percentages of
Ni and Co were 92 and 58%, respectively.
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
30
50
70
Leaching temperature (°C)
90
Figure 6. Recovery percentage of Ni ()
and Co ( ) as a function of leaching
temperature.
°
Effect of solid–liquid ratio
Optimum ratio of crushed scrap electrode to the quantity of acid was determined as a solid–liquid ratio
in the range of 5–40 g/l by using H2 SO4 with a
concentration of 2.5 M at a leaching temperature of
70 ◦ C for120 min. Figure 7 shows that the recovery
percentage of both metals decreased slightly when the
solid–liquid ratio increased from 5 to 15 g/l. Subsequently, they seemed to be constant during such conditions. However, increasing solid–liquid ratio to more
than 15 g/l led to the decrease of recovery percentage.
The optimum solid–liquid ratio for leaching both metals simultaneously was found to be 15 g/l. Under such
conditions, approximately 95.5 and 59.5% of Ni and Co
were recovered, respectively.
Effect of leaching time
The effect of leaching time on the leaching efficiency was carried out in the range of 0–120 min
with 2.5 M H2 SO4 at 70 ◦ C leaching temperature and
15 g/l solid–liquid ratio. The results indicated that the
recovery percentage of both metals increased with the
Asia-Pac. J. Chem. Eng. 2008; 3: 374–379
DOI: 10.1002/apj
377
S. SAKULTUNG, K. PRUKSATHORN AND M. HUNSOM
Asia-Pacific Journal of Chemical Engineering
reducing agent may not be necessary in this system.
100
H2 O2 worked as reducing agent H2 O2 −−→ O2
80
Metal recovery (%)
+ 2H+ + 2e− (1)
60
H2 O2 worked as oxidizing agent H2 O2 + 2H+
+ 2e− −−→ H2 O (2)
40
20
Kinetics of metal leaching process
0
10
15 20 25 30
Solid-liquid ratio (g/l)
35
40
Figure 7. Recovery percentage of Ni ()
and Co ( ) as a function of solid–liquid
ratio.
°
leaching temperature, from 71 to approximately 95%
for Ni, and from 35 to 59% for Co when leaching
time was increased from 5 to 60 min. Subsequently,
they reached their plateau when the leaching time was
greater than 60 min. This may be due to the fact that
leaching equilibrium was obtained at a leaching time
higher than 60 min. Therefore, it can be said that the
optimum leaching time was 60 min leading to a leaching efficiency of approximately 95 and 59% for Ni and
Co, respectively.
Effect of oxidizing agent
Some previous works point out that a reducing agent
such as H2 O2 played an important role in the removal
percentage of Co.[13,14] To increase Co recovery in this
study, various concentrations of H2 O2 were employed.
Figure 8 demonstrates the leaching efficiency of Ni
and Co as a function of reducing concentration in
the range of 0–5 vol% at the leaching temperature of
70 ◦ C, concentration of 2.5 M H2 SO4 and solid–liquid
ratio of 15 g/l. The results indicated that increasing
H2 O2 concentration from 0 to 5 vol% provided slight
increase of the leaching efficiency of Ni from 93 to
approximately 99%. On the other hand, increasing 2
vol% H2 O2 led to the increase of leaching efficiency
of Co by about 10%. The above results indicate that
the presence of a reducing agent affected slightly
the recovery percentage of both metals. When H2 O2
worked as a reducing agent, the O2 , H+ and e− were
produced as in Eqn (1), and the generated electron can
oxidize Co3+ to Co2+ . However, in the very strong
acid condition (pH ≈ 0.56), reduction reaction of H2 O2
to H2 O, as expressed by Eqn (2) occurred instead of
Eqn (1), leading to the absorption of electrons in the
system. Changing of Co3+ to Co2+ occurred slightly,
indicating a small increase of removal percentage.
Therefore, in actual application, the presence of a
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
The kinetics of the metal leaching process was also
investigated in a whole range of leaching times at optimum condition (acid concentration of 2.5 M, leaching
temperature of 70 ◦ C, solid–liquid ratio of 15 g/l). From
the data, it can be seen that the metal concentration in
the bulk liquid solution increased very fast at the beginning, and then slowly reached its plateau after 60 min
(Fig. 9). This phenomenon suggested that the leaching
100
80
Metal recovery (%)
5
60
40
20
0
0
1
2
3
H2O2 (%vol)
4
5
Figure 8. Recovery percentage of Ni () and
Co ( ) as a function of H2 O2 concentration.
°
100
80
Metal recovery (%)
378
60
40
20
Ni
Co
0
0
30
60
Time (min)
90
120
Figure 9. Recovery percentage of Ni ()
and Co ( ) as a function of leaching time at
70 ◦ C (×).
°
Asia-Pac. J. Chem. Eng. 2008; 3: 374–379
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
RECOVERY OF NI AND CO FROM MOBILE PHONE BATTERIES
including Ni-MH and Li-ion batteries. The results
indicate that H2 SO4 was more suitable as a leaching
agent than HNO3 . The optimum leaching condition
was found with an acid concentration of 2.5 M, at
atemperature of 70 ◦ C, solid–liquid ratio of 15 g/l, and
time of 60 min. Under these conditions, approximately
95% of Ni and 59% of Co were leached. The H2 O2 as
a reducing agent had very slight effect on the recovery
percentage of both metals. The leaching of both metals,
which is endothermic, was the second-order reaction of
the metal concentration in the solution.
3000
t/Ct (min-L/mmol)
2500
R2 = 0.9976
2000
1500
R2 = 0.9997
1000
500
0
0
30
60
90
Time (min)
120
150
Acknowledgements
Figure 10. Second-order leaching kinetics of Ni ()
and Co ( ) as a function of time.
°
Authors would like to thank the Department of Mining
& Petroleum Engineering for equipment support.
process can be represented by the second-order rate law
of kinetics as Eqns (3)–(4).[15]
dCt
= k (Cs − Ct )2
(3)
dt
Integration of above equation with the boundary
conditions of t = 0 to t and Ct = 0 to Ct provides
1
t
t
=
+
2
Ct
Cs
kCs
(4)
Figure 10 shows the plot between t/Ct as a function of leaching time of Ni and Co at optimum condition. It was found that the second-order leaching model
and the experimental results agreed well with a coefficient of determination (R 2 ) greater than 0.99. Also,
from the curve, two parameters including saturation
concentration (Cs ) and rate constant (k ) of the leaching process can be determined according to Eqn (4).
The results show that the calculated saturation concentration of Ni (0.0794 mmol/l) was higher than that of
Co (0.0544 mmol/l). In addition, the rate constant of Ni
(2.799 l/mmol min) was higher than that of Co (1.381
l/mmol min). It implies that, under the same conditions,
a greater quantity of Ni can be leached than Co. Also,
the rate of Ni leaching was higher than that of Co,
which agrees with all previous results. The results of the
kinetics investigation confirms that there were two phenomena during the leaching process: initially there was
intense dissolution and scrubbing during which maximum leaching occurred, and consequently, much slower
external diffusion, relating to the soluble remainder,took
place.
CONCLUSION
NOMENCLATURE
Cs
Ct
k
t
saturation concentration of metal (mmol/l)
metal concentration at time t (mmol/l)
second-order leaching rate constant (l/mmol min)
leaching time (min)
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[13] C.K. Lee, K.I. Rhee. J. Power Sources, 2002; 109, 17–21.
[14] P. Zhang, T. Yokoyama, O. Itabashi, M. Suzuki, K. Inoue.
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The leaching process was carried out to extract Ni and
Co simultaneously from scrap mobile phone batteries
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Asia-Pac. J. Chem. Eng. 2008; 3: 374–379
DOI: 10.1002/apj
379
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