Indian Journal of Chemical Technology
Vol. 17, March 2010, pp. 145-149
Dissolution of copper from a primary chalcopyrite ore calcined with and
without Fe2O3 in sulphuric acid solution
Mustafa Gülfen* & Ali Osman Aydın
Department of Chemistry, Faculty of Arts & Sciences, Sakarya University
TR-54187, Esentepe Campus, Sakarya – Turkey
Email: [email protected]
Received 27 May 2009; revised 30 October 2009
Dissolution of copper from a primary chalcopyrite ore supplied from Damar mine area in Murgul-Artvin, Turkey, has
been investigated in sulphuric acid solution after the calcination with and without Fe2O3. The chalcopyrite with and without
Fe2O3 were performed by thermogravimetric (TG) analysis, and the calcined chalcopyrite samples were characterized by
X-ray diffraction (XRD). In the leaching experiments, the effects of calcination temperature, sulphuric acid concentration,
solid/liquid ratio, agitation rate, particle size and dissolution temperature and time on copper dissolution were examined. It
was found that Fe2O3 addition contributed to sulphation during the calcination and then copper dissolution.
Keywords: Chalcopyrite, Iron(III) oxide, Sulphation, Dissolution, Sulphuric acid
Chalcopyrite (CuFeS2), a sulphidic copper mineral, is
the primary sources of copper. The direct production
of copper sulphate from sulphidic copper ores is an
important route to recover copper. The conditions,
however, are dependent on temperature and
sulphatising environment and then dissolution.
Amongst the alternative processes to treat
chalcopyrite, the hydrometallurgical routes without
pretreatment and with pretreatment, such as oxidative
roasting
are
considered
quite
attractive1-7.
Investigation of direct leaching processes involving
different lixiviants such as sulphuric acid, chloride,
nitric acid, ammonical solution and biological systems
have been studied highlighting the major development
in the recent past3. The problem associated with the
iron dissolution in these processes calls for adequate
purification and control methodology before recovery
of the metal by electrowinning. Sulphation roasting is
one of the important pretreatment techniques that may
be adopted to recover copper from the sulphides. The
iron control problem can be obviated to a great extent
by choosing conditions for the sulphation roasting to
produce water soluble copper sulphate and converting
iron to its insoluble oxides. Moreover iron (III) oxide
usage during the roasting contributes the sulphation of
sulphidic copper ore1,3,8-11.
Some researchers have examined the sulphation
roasting of sulphidic copper ores with some additives
so that water-soluble copper sulphate can be
obtained11-18. Prasad et al.11,17 studied the sulphation
of chalcopyrite in presence of some additives such as
Fe2O3, Na2SO4, FeSO4 etc. They showed that these
additives contributed to the sulphation in the roasting
of chalcopyrite concentrate at around 773 K
temperature. They found more sulphation with Fe2O3,
Na2SO4 and FeSO4 than without any addition8,9,11,17.
Neou-Syngiuna and Scordilis18 studied the sulphation
of a Greek complex sulphide concentrate. They
concluded that sulphation roasting can be selective
and SO2 emission can be controlled in the determined
conditions. In addition, they found that water-soluble
sulphate could be obtained from the sulphidic ore18.
The sulphation process of chalcopyrite ore during
roasting is important for a subsequent dissolution.
Since water-soluble sulphate and acid-soluble oxide
compounds of copper can form after the roasting,
copper in the calcined ore can be dissolved easily
from chalcopyrite in dilute acid solutions1.
Hydrometallurgical processes can let the usage of
primary chalcopyrite as raw material. In the present
study, the roasting and sulphation conditions of
primary chalcopyrite with and without Fe2O3, the
optimum conditions for the dissolution of copper from
chalcopyrite in sulphuric acid solution are reported.
Experimental Procedure
The primary chalcopyrite ore supplied from Damar
mine area in Murgul-Artvin, Turkey was used in this
146
INDIAN J. CHEM. TECHNOL., MARCH 2010
study. It was ground and sieved to below 310 µm
particle size. The chalcopyrite ore sample including
chalcopyrite (CuFeS2) and quartz (SiO2) minerals as
major phases was analyzed chemically and the results
are given in Table 1. The chalcopyrite samples
prepared mixed with 10% Fe2O3 and without additive
were calcined for 1 h at the temperatures of 373, 473,
573, 1273 K. The extent of sulphation in the calcined
chalcopyrite sample was examined. The sulphation
ratio (%) was calculated from the conversion of
sulphides to sulphate. The quantity of sulphate formed
during the calcination was determined gravimetrically
with BaCl2 after the dissolution of the calcines in HCl
solution. The converted sulphate in the calcine
can be dissolved in HCl solution, whereas
unconverted sulphides require an oxidizing reagent
(HNO3, H2O2 etc.).
The dissolution experiments were carried out in a
beaker or a flask with reflux system on a magnetic
stirrer. The conditions of experimental parameters
chosen were 373, 473, 573, …, 1273 K for calcination
temperature, 0.0001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 2,
3, 4, 5 M H2SO4 for leaching, 0.01, 0.05, 0.1 0.2, 0.4,
0.6, 0.8, …, 2.0 g/mL for solid/liquid ratio, 0, 100,
200, 700 rpm for agitation rate and 2, 4, 6, 8, 10 and
15 min at 298-373 K for dissolution temperature.
Copper and iron concentrations in the leach
solutions were analyzed by atomic absorption
spectrometer (Shimadzu 6701F AA). The thermal
analysis experiments were carried out in static air
atmosphere using Seteram TG-DTA-92 thermal
analyzer. The heating rate of 10 K per min was
employed in a platinum crucible. The TG curves of
the chalcopyrite with and without Fe2O3 up to
temperature of 1273 K are given in Fig. 1. Moreover
the X-ray diffractrograms (XRD) of calcined samples
were taken from Shimadzu XRD-6000 diffractometer
with Cu source. The identifications of the phases in
the samples were based on ASTM X-ray powder
data file.
ore requires its concentration by flotation. However
the hydrometallurgical routes do not require any
concentration and this is an advantage of cost. In
addition, it may be thought that more effective
sulphate formation occurs from dilute sulphide
minerals in silica matrix. In other words, more
iron(III) oxide per sulfur content can be added into
the ore. So, primary chalcopyrite ore was used in
this study.
Thermal analysis
The thermogravimetric curves of the original
chalcopyrite ore (TG1) and the chalcopyrite sample
mixed with 10% Fe2O3 (TG2) up to the temperature
of 1273 K in air atmosphere are given in Fig. 1. The
thermal analysis results showed that the chalcopyrite
began to decompose above 668 K when it was heated
in air. Weight gain in the chalcopyrite was noted in
the temperature range 668-739 K (TG1 in Fig. 1). On
the other hand, the chalcopyrite mixed with 10%
Fe2O3 showed a different TG curve in the temperature
range 635-973 K (TG2 in Fig. 1). The weight gain
was found as 0.332% for the chalcopyrite at 738 K
Fig. 1—Thermogravimetric curves of the chalcopyrite (TG1) and
the chalcopyrite sample with 10% Fe2O3 (TG2) in air. Sample
weight, 30 mg; Heating rate, 10 K per min.
Results and Discussion
Chemical analysis
The chemical analysis of the primary chalcopyrite
ore is given in Table 1. The ore contains 69.85% SiO2
as major content and 3.35% Cu, 11.15% Fe and
11.67% S as other important contents. Quartz (SiO2),
chalcopyrite (CuFeS2) and dolomite [(CaMgCO3)2]
were determined in the ore sample. In the present
study, the primary chalcopyrite ore, not concentrated,
was used. The pyrometallurgical route of chalcopyrite
Table 1—Chemical analysis of the chalcopyrite ore
Constituents
wt. %
SiO2
Cu
Fe
S
Al2O3
CaO
Moisture
69.85
3.35
11.15
11.67
2.10
0.60
0.20
GÜLFEN & AYDIN: DISSOLUTION OF COPPER FROM CALCINED CHALCOPYRITE ORE
and 1.657% for the chalcopyrite with Fe2O3 at 870 K.
While a weight loss began at 773 K in the
chalcopyrite, a clear weight gain in the sample with
Fe2O3 was noted from 773 to 873 K. Weight loss
(TG1) at 773 K may be due to decomposition of
chalcopyrite mineral. However weight gain of the
chalcopyrite mixed Fe2O3 at 773 K may be due to
reaction between Fe2O3 and SO2 and then copper
sulfate formation. At the temperatures above 973 K,
both the samples showed similar TG curves with
respect to weight change.
Depending on the temperature, chalcopyrite during
roasting in air forms sulfur, sulfur dioxide, copper
sulphate, copper and iron oxides and copper ferrite
(CuFe2O4). These calcined products are important for
subsequent leaching processes and can be dissolved in
different solutions such as sulphates in water, oxides
in acids and sulphides in oxidative solutions (HNO3,
H2O2 etc.). When a chalcopyrite ore is roasted
the more weight gain accounts for more sulphate
formation. When it has weight loss, sulfur dioxide
emission from a chalcopyrite occurs. Fe2O3 addition
resulted in more sulphate formation because
Fe2O3 contributed to the change of SO2 to SO3 as a
catalyst 2, 8,10,13,19-22.
Calcination and sulphation
The chalcopyrite samples with and without Fe2O3
were calcined for 1 h in the temperature range
573-1073 K and sulphate quantities in these calcines
were analyzed by dissolving in hydrochloric acid
solution. However sulphides can not be dissolved in
HCl solution. So the sulphation in the calcined sample
can be found by dissolving with hydrochloric acid
solution. The percentage of the sulphation was
calculated using Eq. (1).
Converted sulfur to sulphate
in the calcined sample
(by dissolving with HC1)
Sulphation (%) =
× 100
Total sulfur content in
the calcined sample
(by dissolving with HC1+HNO3 )
…(1)
Calcination temperatures to examine the sulphation
of the chalcopyrite samples with and without Fe2O3
were chosen as 573-1073 K by applying knowledge
of the thermodynamics of the Cu-Fe-S-O system:
chalcopyrite3,9. The sulphation results are shown in
Fig. 2. It may be seen that more sulphate in the
147
calcined chalcopyrite with and without Fe2O3 formed
at the temperatures of 773, 873 and 973 K than that at
lower and higher temperatures. It was noted that
Fe2O3 addition contributed to increase in the
sulphation of the chalcopyrite, which was also
indicated by thermogravimetric and sulphate analyses
of the calcined chalcopyrite sample. The sulphation in
chalcopyrite will decrease the acid consumption
during the dissolution.
The original chalcopyrite ore and the chalcopyrite
samples calcined at 773, 873 and 973 K were
characterized by X-ray diffraction analysis. XRD
phases in the chalcopyrite samples is given in Table 2.
It may be seen from Table 2 that the all samples
Fig. 2—Sulphation of chalcopyrite samples with and without
additive.
Table 2—XRD phase identification
Calcination Chalcopyrite
temperature
(K)
Chalcopyrite with Fe2O3
Original
Major Phases:
Quartz (SiO2),
Chalcopyrite (CuFeS2)
Minor Phase:
Dolomite
[CaMg(CO3)2]
_
773
Major Phases:
Quartz (SiO2),
Hematite (Fe2O3),
Copper sulphate
(CuSO4)
Major Phases:
Quartz (SiO2),
Hematite (Fe2O3),
Copper sulphate
(CuSO4)
873
Major Phases:
Quartz (SiO2),
Hematite (Fe2O3),
Copper sulphate
(CuSO4)
Major Phases:
Quartz (SiO2),
Hematite (Fe2O3),
Copper sulphate
(CuSO4)
973
Major Phases:
Quartz (SiO2),
Hematite (Fe2O3),
Copper sulphate
(CuSO4)
Major Phases:
Quartz (SiO2),
Hematite (Fe2O3),
Copper sulphate
(CuSO4)
148
INDIAN J. CHEM. TECHNOL., MARCH 2010
include quartz mineral as major phase. While quartz,
chalcopyrite and dolomite were determined in the
original chalcopyrite sample, hematite and copper
sulphate were noted in the calcined samples. Copper
sulphate formed when the chalcopyrite was calcined
at the temperatures of 773 and 873 K. The calcined
chalcopyrite at 973 K had less copper sulphate than
those at 773 and 873 K. That the dissolution of
copper from the samples was the maximum at
873 K was confirmed with copper sulphate
formation8-11, 18, 19, 21-23.
Dissolution of chalcopyrite
The original chalcopyrite and the chalcopyrite
mixed with Fe2O3 were roasted for 1 h at varying
temperature (373, 1273 K) and then calcines were
dissolved in 1 M H2SO4 solution. The results for
copper and iron leaching are given in Fig. 3. It may be
seen from Fig. 3 that iron dissolution was high when
the ore was roasted at 673 and 773 K whereas high
copper dissolutions were observed for the roasting at
773, 873 and 973 K. Because sulphate salts and
oxides such as CuSO4, FeSO4, CuO, FeO and Fe2O3
form between 673-973 K temperatures, high
dissolutions for copper and iron were found at these
temperatures.
The chalcopyrite ore calcined for 1 h at 873 K
temperature was chosen as the optimum calcination
conditions, because of high copper recovery and
low iron dissolution, and these samples were used in
the later studies. At these conditions, copper can be
dissolved selectively. If a direct leaching process
was used, the copper solution would include more
iron content.
Effect of acid concentration (0-5 M H2SO4) was
examined for the dissolution of copper from the
Fig. 3—The dissolutions of copper and iron from the calcined
chalcopyrite (1) and the chalcopyrite calcined with 10%Fe2O3 (2).
Calcined sample, 1 g; H2SO4 (1 M), 100 mL; Contact time,
60 min; Agitation rate, 400 rpm; Temperature, 298 K.
calcine obtained by roasting for 1 h at 873 K. Copper
recovery was around 60% in distilled water and
67-72% in the acid solutions. Iron dissolution
increased at high acid concentrations. The acid
concentration of 0.1 M was found to be optimum with
high copper and low iron dissolution. Acid
consumption may be because of hematite (low iron
dissolution), copper oxy-sulphate (CuO.CuSO4) and
dolomite or calcium oxide.
The leaching tests in 0.1 M H2SO4 were conducted
at different solid/liquid ratios (0.01-2.0 g/mL), using
the sample calcined under the optimum conditions.
The optimum solid/liquid ratio was found to be
1.2 g/mL with 25 g/L copper and 4 g/L iron ions in
the final leach liquor. In other words, copper/iron
ratio changed from 0.3 in the ore to 6.25 in the
leach solution.
Agitation rate (0-700 rpm) on copper dissolution
was also studied and the results given in Fig. 4
showed that it was very effective up to 400 rpm. The
dissolution increased slightly above 400 rpm. The
agitation improved the dissolution, because of better
dispersion of solids in the lixiviant24,25.
The effect of particle size on the dissolution was
examined. While the dissolution of copper with the
samples of the particle size 150 µm or smaller were
between 60-80%, the dissolutions decreased to a low
of 20-30% for the particles above 150 µm size. This
may be attributed to increase in surface area for the
finer size material.
The effect of temperature and time on the
dissolution experiments was studied and the results
are given in Fig. 5 and in Fig. 6 for the calcine
without additive and with Fe2O3 addition,
respectively. The results showed that the copper
dissolutions in the both samples were nearly 50%
within 2 min and the dissolution time was effective.
On the other hand, temperature of leaching was not
Fig. 4—Effect of agitation rate on copper dissolution from sample
calcined for 1 h at 873 K. Solid/liquid ratio, 1.2 g/mL; H2SO4,
0.1 M; Temperature, 298 K; Contact time, 60 min.
GÜLFEN & AYDIN: DISSOLUTION OF COPPER FROM CALCINED CHALCOPYRITE ORE
149
In this process it may be expressed that copper
dissolution is controlled by limit film diffusion.
It was found that Fe2O3 addition before the
calcination also contributed to the copper dissolution.
Thus, Fe2O3 can be added into chalcopyrite ores
before calcination for more copper sulphate formation
and then copper dissolution in dilute H2SO4 solution.
Fig. 5—Effect of temperature on copper dissolution on samples
calcined for 1 h at 873 K. Solid/liquid ratio, 1.2 g/mL; H2SO4,
0.1 M.
Acknowledgement
The authors are thankful to The Black Sea Copper
Mining Co. in Turkey.
References
1
2
3
4
5
6
Fig. 6—Effect of temperature on copper dissolution from the
chalcopyrite sample calcined with 10% Fe2O3 for 1 h at 873 K.
Solid/liquid ratio, 1.2 g/mL; H2SO4, 0.1 M.
that effective. The copper dissolution was 77% at
373 K in 15 min for the calcined chalcopyrite whereas
it was 82% for the calcine mixed with Fe2O3.
Conclusions
Dissolution of copper from a primary chalcopyrite
ore has been examined in sulphuric acid solution after
the calcination with and without Fe2O3. Based on the
foregoing experimental results, the following
conclusions may be drawn.
The calcination of chalcopyrite resulted in weight
gain between 668-739 K without additive and
635-973 K with Fe2O3 addition because of copper
sulphate formation. Fe2O3 addition contributed to
sulphate formation.
To dissolve the copper from the chalcopyrite with
or without Fe2O3 under the optimum conditions,
primary chalcopyrite ore must be ground to smaller
particle sizes than 150 µm and calcined for 1 h at 873
K temperature. Sulphuric acid concentration of 0.1 M
is sufficient, and solid/liquid ratio of up to 1.2 g/mL
can be maintained.
The agitation rate was found to be effective during
the dissolution, while temperature was less effective.
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