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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: koujue@ustb.edu.cn; xingyi@ustb.edu.cn.

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

2

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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