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Extraction of copper from copper bearing biotite by
ultrasonic-assisted leaching
Bao-qiang Yu1), Jue Kou1), Chun-bao Sun1), Yi Xing2)
Corresponding authors: Jue Kou; Yi Xing.
E-mail: [email protected] ; [email protected] .
1) School of Civil and Resource Engineering, University of Science and Technology Beijing,
Beijing 100083, China
2) School of Energy and Environmental Engineering, University of Science and Technology
Beijing, Beijing 100083, China
Abstract
Copper bearing biotite is a typical refractory copper mineral on the surface of
Zambian copper belt. Aiming to treat this kind of copper oxide ore with a more
effective method, ultrasonic-assisted acid leaching was conducted in this paper.
Compared with regular acid leaching, ultrasound could reduce leaching time from 120
min to 40 min, and sulfuric acid concentration could be reduced from 0.5 mol·L-1 to
0.3 mol·L-1. Besides, leaching temperature could be reduced from 75℃ to 45℃ at
same copper leaching rate of 78%. Mechanism analysis indicates that ultrasonic wave
can cause delamination of copper bearing biotite and increase the specific surface area
from 0.55 m2·g-1 to 1.67 m2·g-1. The results indicate that copper extraction from
copper bearing biotite by ultrasonic-assisted acid leaching is more effective than
regular acid leaching. This study proposes a promising method for recycling valuable
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International Journal of Minerals, Metallurgy and Materials https://doi.org/10.1007/s12613-020-2132-y
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metals from phyllosilicate minerals.
Keywords: Ultrasonic wave; Copper extraction; Delamination; Copper bearing
biotite
1. Introduction
Zambian copperbelt is a typical sedimentary copperbelt, accounting for
approximately 46% of the production and reserves of copper resource in central
African [1-3]. Copper minerals underground in this copperbelt are mainly bornite and
chalcopyrite, which can be easily recovered only by flotation [4]. However, for
surface copper oxide ore, copper is mainly present in biotite [5]. It has been reported
that copper in biotite mainly exists in the state of isomorphism by replacing
magnesium or iron and it is difficult to be extracted by acid leaching at atmospheric
temperature [6-7]. Many local hydrometallurgy plants utilize thermal treatment and
acid leaching to treat this copper bearing biotite mineral, but the recovery is not
satisfactory, and mostly less than 70%. Besides, the power consumption is rather high
during thermal treatment. So it is necessary to make full use of this kind of copper
resource with an alternative, more effective and economical method.
In recent years, the utilization of ultrasonic wave in ore leaching is gaining more
and more attention [8-9]. It is commonly recognized that cavitation generated by
ultrasonic wave plays a key role in leaching process [10-11]. The extremely high local
pressure and temperature generated by cavitation contributes to promoting the
generation of cracks on the surface of ore particles, accelerating mass transfer and
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diffusion, reducing the viscosity and surface tension of solution, etc [12], which is in
favor of increasing leaching efficiency and reducing leaching time. Many researchers
have used ultrasonic-assisted leaching to recover valuable metals from refractory ore,
smelt slag, spent batteries, circuit board, etc [13-20]. Rao et al. [21] studied
ultrasound-assisted ammonia leaching of copper oxide ore and found that there was a
20% increase in copper leaching rate by ultrasound-assisted leaching than normal
ammonia leaching. Besides, leaching time and ammonia consumption decreased. Fu
et al. [22] utilized ultrasonic-assisted chlorination-oxidation method to treat refractory
gold ores, and found that sulfide minerals could be decomposed and gold recovery
increased significantly with the assistance of ultrasonic wave radiation. Zhang et al.
[23] found that the extraction of Sb and Pb from antimony-rich and lead-rich
oxidizing slag was obviously improved with the assistance of ultrasound and the
leaching time was reduced from 45 min to 15 min at same leaching rate of Sb.
It’s reported that sonication of phyllosilicate minerals like mica could cause severe
delamination and reduce the plate diameter in lateral dimension, and also yield
nanometric flakes that retain the original structure [24]. So it is likely to achieve
higher copper leaching rate when copper bearing biotite was treated by ultrasound. In
order to effectively make full use of this kind of copper resource, this paper utilized
ultrasonic assisted leaching to recover copper from biotite. The results of
ultrasonic-assisted leaching and normal acid leaching were compared. The effects of
ultrasound on copper leaching rate, leaching temperature, sulfuric acid concentration,
and leaching time were systematically investigated. What’s more, the mechanism of
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ultrasonic-assisted leaching was explained as well. This study proposes a promising
method for recycling valuable metals from phyllosilicate minerals.
2. Experimental
2.1. Materials
Copper bearing biotite sample utilized in the study was from a local plant in
Luanshya, Zambia. The sample was firstly air-dried, and then directly used for
leaching. The particle size distribution of raw sample (Fig.1), measured by laser
particle size analyzer (LS-POP(9), China), shows that it is mainly distributed in the
range of 0.03 mm to 0.15 mm. The chemical composition of the sample (Table 1) was
analyzed by XRF (XRF-1800, Japan) and ICP-OES (iCAP 7400, America). It shows
that copper grade of the sample is 2.51%, which is higher than the average grade of
normal copper oxide ore. Mineral composition of raw sample was determined by
XRD (Ultima-IV, Japan). XRD pattern of raw sample (Fig.2) indicates that biotite and
quartz are the main minerals in the sample. Analysis by BGRIMM Process
Mineralogy Analyzer (BPMA V1.0,China) (Fig.3) shows that besides biotite and
quartz, raw sample contains very small part of feldspar and phlogopite. The EDS
(energy dispersive spectroscopy) pattern of biotite Fig.3 (c) indicates that copper
might be finely wrapped in biotite or present in the form of isomorphism. Sulfuric
acid utilized in leaching tests was analytical grade and purchased from Sinopharm
Chemical Reagent Co.,Ltd, China. The water used in all the tests is distilled water
unless otherwise specified.
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1 10 100 10000
2
4
6
8
10
12
Wei
ght p
erce
nt /
wt%
Particle size / μm
Fig.1. Particle size distribution of raw sample
Table 1. Chemical composition of copper bearing biotite sample
Element Cu Fe S P Mn TiO2 K2O
Content / wt% 2.51 6.68 0.12 0.098 0.37 0.972 7.72
Element Na2O CaO MgO Al2O3 SiO2 NiO Zn
Content / wt% 0.107 0.44 16.46 12.66 51.60 0.012 0.01
0 10 20 30 40 50 60 70 80 900
2000
4000
6000
8000
68.460.154.950.2
39.534.2
26.6
20.9
8.8
∆ ∆∆
∆ Biotite
□
□□□
□ □ Quarz∆
Inte
nsity
/ a.
u.
2θ / °
Fig.2. XRD pattern of copper bearing biotite sample
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Biotite Quartz Feldspar Phlogopite
0 1 2 3 4 5 6 7 8 9 100
100
200
300
400
500
600
700
Fe
Fe
AlO
Cu
Mg
Cu
KK
Si
Cou
nts /
cps
Energy / kevFig.3. BPMA images of raw sample: (a) Mineral phase image (b) SEM image; (c) EDS pattern of biotite
2.2. Experiment procedure
Leaching tests were conducted in conical flask (250 mL) which was equipped with
an agitator, and the flask could be heated by a thermostat control ultrasonic generator
(KQ-300E, China), as shown in Fig.4. The frequency of ultrasonic wave is 20.21 kHz,
and the temperature of water bath ranges from 25℃ to 100℃. Firstly,the water bath
was heated to set temperature. Thereafter 40 g copper bearing biotite and a certain
volume of sulfuric acid solution were added into the flask for agitating and leaching.
The stirring speed of the agitator was controlled at 400 rpm, at which speed biotite
particles could be uniformly dispersed in sulfuric acid solution. When leaching tests
were finished, the residue was filtered in Buchner funnel (100 mm) and washed with
+1
(a) (b)
(c)
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distilled water for three times. After that the residue was dried in an oven, followed by
weighing, copper content analysis by ICP-OES iCAP 7400. Copper leaching rate was
calculated by using Equation (1):
(1)%100)1(11
22
m
mR
where R represents Cu leaching rate, β1 (wt%) and m1 (g) are the copper grade and
mass of the sample before leaching, β2 (wt%) and m2 (g) are the copper grade and
mass of leaching residue.
Fig.4. Schematic of leaching apparatus
3. Results and discussions
In order to investigate the effect of ultrasound on leaching time, solid/liquid ratio,
sulfuric acid concentration and temperature, ultrasonic-assisted and regular acid
leaching tests were conducted and compared.
3.1. The effect of leaching time on leaching
Leaching time tests with and without ultrasound were carried out at 0.5 mol·L-1
sulfuric acid, temperature of 25℃ and solid/liquid ratio of 1:4. Leaching time ranges
from 0 to 150 min. The results shown in Fig.5 indicated that 60% of copper could be
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extracted in 40 min for ultrasound-assisted acid leaching, and after then there was no
significant increase in copper leaching rate. While for regular acid leaching the
maximum copper leaching rate was only 20%, meanwhile the leaching time was 120
min, much longer than that of ultrasonic-assisted acid leaching. It suggested that
ultrasound could significantly increase copper leaching rate and shorten the reaction
time. It might because cavitation phenomenon which caused by ultrasonic wave can
enlarge the specific surface area of copper bearing biotite particles [24]. Meanwhile
extremely high local pressure and temperature generated by cavitation contributed to
accelerating mass transfer and diffusion, as described by Chang et al. [25].
0 20 40 60 80 100 120 140 1600
20
40
60
80
100
Cop
per l
each
ing
rate
/ w
t%
Leaching time / min
Regular acid leaching Ultrasound-assisted acid leaching
Fig.5. Effect of leaching time on Cu leaching rate
3.2. The effect of solid/liquid ratio on leaching
To investigate the influence of solid/liquid ratio on leaching, ultrasonic-assisted and
regular acid leaching experiments with solid/liquid ratio of 1:1, 1:2, 1:3, 1:4, 1:5, 1:6
(namely the volume of sulfuric acid solution was 40 ml, 80 ml, 120 ml, 160 ml, 200
ml, 240 ml) were conducted at sulfuric acid concentration 0.5 mol·L-1, temperature 25℃
and leaching time 120 min, during which the mass of raw sample for each test was 40
g. The results are shown in Fig.6. For ultrasonic-assisted acid leaching, the change of
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solid/liquid ratio almost had no influence on copper leaching rate. There was a slight
decrease of copper leaching rate when solid/liquid ratio was 1:1, and then remained
constant at 60% with the solid/liquid ratio decreasing from 1:2 to 1:6. While for
regular acid leaching, copper leaching rate slowly increased with the solid/liquid ratio
decreasing, and remained unchanged when solid/liquid ratio was lower than 1:4. It
means that leaching at higher solid/liquid ratio could be carried out with the aid of
ultrasound, which was in favor of improving the throughput of industrial production.
It’s probably because the shock wave and micro jet of cavitation bubbles generated by
ultrasonic wave can increase the kinetic energy of mineral particles and sulfuric acid
solution, and further cause more effective contact between mineral particles and
sulfuric acid, which is impossible to occur during regular acid leaching [16].
1:1 1:2 1:3 1:4 1:5 1:60
20
40
60
80
100
Cop
per l
each
ing
rate
/ w
t%
Solid-liquid ratio (S/L)
Regular acid leaching Ultrasound-assisted acid leaching
Fig.6. Effect of solid/liquid ratio on Cu leaching rate
3.3. The effect of acid concentration on leaching
The effect of acid concentration on leaching was studied at solid/liquid ratio of 1:4,
temperature of 25℃ and leaching time of 120 min. The results (Fig.7) indicated that
the highest copper extraction rate could be obtained when sulfuric acid concentration
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was 0.3 mol·L-1 with the assistance of ultrasound, and there was no significant
increase in copper leaching rate with the sulfuric acid concentration increasing. For
regular acid leaching, copper leaching rate gradually increased when the
concentration of sulfuric acid increased from 0.1 to 0.5 mol·L-1, and then remained
constant. It suggests that ultrasonic-assisted leaching can be conducted at a lower
sulfuric acid concentration, which is helpful to reduce acid consumption.
0.1 0.2 0.3 0.4 0.5 0.60
20
40
60
80
100
Cop
per l
each
ing
rate
/ w
t%
Sulfuric acid concentration / (mol·L-1)
Regular acid leaching Ultrasound-assisted acid leaching
Fig.7 Effect of sulfuric acid concentration on Cu leaching rate
3.4. The effect of temperature on leaching
In order to investigate the influence of temperature on leaching, leaching tests at
different temperature with and without ultrasound were carried out at 0.5 mol·L-1
sulfuric acid, solid/liquid ratio of 1:4, and leaching time of 120 min. The results are
illustrated in Fig.8. It shows that temperature has more pronounced influence on
regular acid leaching than on ultrasonic-assisted acid leaching. For ultrasonic-assisted
acid leaching, copper leaching rate slowly increases with the temperature increasing.
While for regular acid leaching, there is a fast increase in copper leaching rate when
temperature increases from 25℃ to 65℃, and the highest copper leaching rate 78%
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can be achieved at 75℃. To obtain same copper leaching rate of 78%, the temperature
required for ultrasonic-assisted leaching is only 45℃, much lower than that of regular
acid leaching. Copper leaching rate of ultrasound-assisted acid leaching is higher than
that of regular acid leaching at the same temperature, and the gap is more obvious in
low temperature range. Meanwhile, the temperature necessary for ultrasound-assisted
acid leaching is lower than that for regular acid leaching at same copper leaching rate.
It means that ultrasonic wave is in favor of reducing leaching temperature, which is
beneficial for saving energy.
20 30 40 50 60 70 80 900
20
40
60
80
100
Cop
per l
each
ing
rate
/ w
t%
Temperature / ℃
Regular acid leaching Ultrasound-assisted acid leaching
Fig.8. Effect of temperature on Cu leaching rate
3.5. The mechanism of ultrasonic-assisted leaching
The above experiments indicate that ultrasound is in favor of improving copper
extraction from copper-bearing biotite in low temperature. In order to better illustrate
the mechanism of ultrasonic-assisted acid leaching, particle size distribution of raw
sample, leaching residue with and without ultrasound were analyzed by using laser
particle size analyzer (LS-POP). The results shown in Fig.9 indicate that the particle
size (D90) of raw sample, residue of regular and ultrasound-assisted acid leaching are
203 μm, 221 μm, 161 μm respectively. The cumulative percent of particles less than
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37 μm of raw sample and regular acid leaching residue are 1.2% and 0.9%
respectively, while the value of ultrasonic-assisted acid leaching residue is 19.8%.
Particle size distribution of regular acid leaching residue almost has no change
comparing to that of raw sample. While for residue of ultrasonic-assisted acid
leaching, the particle size distribution curve moves to left, which means the average
particle size is getting smaller, approximately 20% decrease in size. It manifests that
ultrasound energy can decrease the particle size of biotite.
In addition, to further analyze the function of ultrasound on copper-bearing biotite,
the specific surface area of raw sample, leaching residue with and without ultrasound
was measured by BET method [26], and was determined as 0.59 m2·g-1, 1.67 m2·g-1
and 0.55 m2·g-1 respectively. The results indicate that the specific surface area of
copper bearing biotite sample nearly has no change after regular acid leaching.
However, the specific surface area of the sample after ultrasonic-assisted leaching is
almost three times that of raw sample. It means that ultrasound energy can increase
the specific surface area of copper bearing biotite to a large extent, which is very
favorable to the contact and reaction between particles and sulfuric acid solution.
Considering that the degree of reduction in particle size was not pronounced as the
increase in specific surface area after ultrasonic-assisted acid leaching, it was
probably because that copper bearing biotite was mainly delaminated other than
broken up in lateral dimension by ultrasonic wave, as described by Pérez-Rodríguez
et al. [21]. The average diameter-thickness ratio of regular acid leaching and
ultrasonic-assisted acid leaching residue was measured to be 5.32 and 27.45
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respectively, which means that ultrasonic cavitation can break up copper bearing
biotite into much thinner pieces through its dissociation and cleavage crack. The
delamination of copper bearing biotite by ultrasonic wave can be illustrated in Fig.10.
0 100 200 300 400 500
0
20
40
60
80
100C
umul
ativ
e pe
rcen
t / w
t%
Particle size / μm
Raw sample Regular acid leaching Ultrasound-assisted acid leaching
Fig.9. Particle size of raw sample and residue with and without ultrasound
Fig.10. Delamination of copper bearing biotite after sonication
3.6. Energy consumption calculation
In order to compare the cost of ultrasound-assisted acid leaching and regular acid
leaching, the key factor energy consumption was calculated and compared based on
operating power of equipment and test results. The results shown in Table 2
demonstrate that, at same copper leaching rate of 78%, the energy consumption of
ultrasound-assisted acid leaching is 0.6 kWh, which is much lower than that of regular
acid leaching (1.6 kWh). Considering that ultrasound can also help to reduce acid
consumption, the cost of ultrasound-assisted acid leaching should be lower, which
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means that ultrasound-assisted acid leaching is more economical than regular acid
leaching.
Table 2. Energy consumption calculation of ultrasound-assisted and regular acid leaching
Ultrasound-assisted acid leaching Regular acid leaching
Copper leaching rate / wt% 78 78
Leaching temperature / ℃ 45 75
Heating power / W 600 800
Ultrasonic power / W 300 -
Leaching time / min 40 120
Total energy consumption / kWh 0.6 1.6
4. Conclusions
Extraction of copper from copper bearing biotite by ultrasonic-assisted acid
leaching was conducted, and the effect of parameters on experiments was investigated
as well. Compared to regular acid leaching, ultrasonic-assisted acid leaching could
reduce leaching time and the consumption of sulfuric acid. What’s more, at same
copper leaching rate, the leaching could be carried out at higher solid/liquid ratio and
lower temperature, which was very helpful for saving energy. More important, copper
leaching rate was obviously improved by ultrasonic-assisted acid leaching at low
temperature. The mechanism analysis indicates that ultrasonic wave treatment can
cause delamination of biotite and increase the specific surface area to a large extent.
The results of energy consumption calculation demonstrate that ultrasound-assisted
acid leaching is more energy-saving and economical than regular acid leaching. This
study indicates that the recovery of copper from copper bearing biotite by
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ultrasonic-assisted acid leaching is more effective and economical than regular acid
leaching. This research proposes a promising method for recovering valuable metals
that exist in phyllosilicate minerals.
Acknowledgements
The financial support from National Natural Science Foundation of China
(No.51574018) for this work is gratefully acknowledged. The authors are also grateful
for copper bearing biotite sample collection and delivery by China Nonferrous Metal
Mining (Group) Co., Ltd.
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