3390 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
temperature was reached. Thereafter, the flasks were
removed from the incubator and 2 g of solids were added
to each flask. The time instance that the solids were added
signified the start of the test (i.e., t =0 hours). For the tests
performed with hydrogen peroxide, 1 vol% hydrogen per-
oxide was added immediately after solids addition. The
flasks were then placed back in the incubator and shaking
set to the desired speed of 100 rpm. 2 mL samples were
taken at predetermined time intervals and filtered immedi-
ately, using 0.45 µm syringe filters, to prevent further leach-
ing from taking place. Where applicable, 1 vol% hydrogen
peroxide was added to the leach solution after each sample
was taken. Tests were performed for a total of 7 hours.
Leaching optimisation tests were performed in a jack-
eted glass reaction vessel, with a maximum working volume
of 1.5 L. Agitation was provided by an overhead stirrer,
fitted with a Teflon anchor impeller. A hotplate and PT
1000 temperature sensor provided feedback control and
maintained the solution temperature within 2°C of the set-
point temperature. Where necessary, cooling was achieved
by circulating water at ±15°C through the vessel jacket. To
prevent vapour losses, particularly at elevated temperatures,
a condenser was fitted to the lid of the vessel. The lid of the
vessel contained a sampling port, which was also used for
loading of the acid at the desired temperature. The required
volume of solids and water was added to the reaction vessel.
The lid was fastened to the vessel, stirrer set to the desired
agitation speed (350 – 500 rpm) and the heating process
initiated. Once the desired temperature had been reached,
the required amount of acid was added to the reaction ves-
sel. This time instance signified the start of the test. 2 mL
samples were taken at predetermined time intervals and
filtered immediately using 0.45 µm syringe filters. Tests
were performed for a total of 6 hours. At the end of each
test, solids were separated from the pregnant leach solution
via centrifugation. The solids were washed with water, air
dried, and kept for XRD analysis.
All solution samples were analysed using inductively
coupled plasma optical emission spectrometry (ICP-OES)
to determine the concentration of metals. The mass of metal
in solution at a given time was expressed as a percentage of
the total mass of that metal contained in the feed material.
RESULTS AND DISCUSSION
Screening Tests
The extent of lithium dissolution after 7 hours, for each of
the seven acid types investigated, is shown in Figure 2. Of
the organic acids that were evaluated, organic acid A yielded
the highest percentage lithium dissolution. At 25°C, in the
absence of hydrogen peroxide, 77% and 83% dissolution
was achieved after 7 hours, for organic acid A and sulphuric
acid, respectively. With an increase in temperature from
25°C to 60°C, lithium dissolution increased significantly
for both organic acid B and organic acid C. At 60°C, in the
absence of hydrogen peroxide, 63%, 72%, 80% and 86%
lithium dissolution was achieved after 7 hours for organic
acid C, organic acid B, organic acid A and sulphuric acid,
respectively. The addition of hydrogen peroxide had no sig-
nificant effect on lithium dissolution using organic acid A
and organic acid B. The role of hydrogen peroxide in the
dissolution of lithium using sulphuric acid and organic acid
C is not clear.
The leaching efficiencies appear to be closely related
to the acidity of the different acids: the highest lithium
0
10
20
30
40
50
60
70
80
90
100
Acid type
25°
60°
Figure 2. Percentage lithium dissolution after 7 hours at an acid concentration of 1 M and 2% solids
Li
dissolug415on(%)
temperature was reached. Thereafter, the flasks were
removed from the incubator and 2 g of solids were added
to each flask. The time instance that the solids were added
signified the start of the test (i.e., t =0 hours). For the tests
performed with hydrogen peroxide, 1 vol% hydrogen per-
oxide was added immediately after solids addition. The
flasks were then placed back in the incubator and shaking
set to the desired speed of 100 rpm. 2 mL samples were
taken at predetermined time intervals and filtered immedi-
ately, using 0.45 µm syringe filters, to prevent further leach-
ing from taking place. Where applicable, 1 vol% hydrogen
peroxide was added to the leach solution after each sample
was taken. Tests were performed for a total of 7 hours.
Leaching optimisation tests were performed in a jack-
eted glass reaction vessel, with a maximum working volume
of 1.5 L. Agitation was provided by an overhead stirrer,
fitted with a Teflon anchor impeller. A hotplate and PT
1000 temperature sensor provided feedback control and
maintained the solution temperature within 2°C of the set-
point temperature. Where necessary, cooling was achieved
by circulating water at ±15°C through the vessel jacket. To
prevent vapour losses, particularly at elevated temperatures,
a condenser was fitted to the lid of the vessel. The lid of the
vessel contained a sampling port, which was also used for
loading of the acid at the desired temperature. The required
volume of solids and water was added to the reaction vessel.
The lid was fastened to the vessel, stirrer set to the desired
agitation speed (350 – 500 rpm) and the heating process
initiated. Once the desired temperature had been reached,
the required amount of acid was added to the reaction ves-
sel. This time instance signified the start of the test. 2 mL
samples were taken at predetermined time intervals and
filtered immediately using 0.45 µm syringe filters. Tests
were performed for a total of 6 hours. At the end of each
test, solids were separated from the pregnant leach solution
via centrifugation. The solids were washed with water, air
dried, and kept for XRD analysis.
All solution samples were analysed using inductively
coupled plasma optical emission spectrometry (ICP-OES)
to determine the concentration of metals. The mass of metal
in solution at a given time was expressed as a percentage of
the total mass of that metal contained in the feed material.
RESULTS AND DISCUSSION
Screening Tests
The extent of lithium dissolution after 7 hours, for each of
the seven acid types investigated, is shown in Figure 2. Of
the organic acids that were evaluated, organic acid A yielded
the highest percentage lithium dissolution. At 25°C, in the
absence of hydrogen peroxide, 77% and 83% dissolution
was achieved after 7 hours, for organic acid A and sulphuric
acid, respectively. With an increase in temperature from
25°C to 60°C, lithium dissolution increased significantly
for both organic acid B and organic acid C. At 60°C, in the
absence of hydrogen peroxide, 63%, 72%, 80% and 86%
lithium dissolution was achieved after 7 hours for organic
acid C, organic acid B, organic acid A and sulphuric acid,
respectively. The addition of hydrogen peroxide had no sig-
nificant effect on lithium dissolution using organic acid A
and organic acid B. The role of hydrogen peroxide in the
dissolution of lithium using sulphuric acid and organic acid
C is not clear.
The leaching efficiencies appear to be closely related
to the acidity of the different acids: the highest lithium
0
10
20
30
40
50
60
70
80
90
100
Acid type
25°
60°
Figure 2. Percentage lithium dissolution after 7 hours at an acid concentration of 1 M and 2% solids
Li
dissolug415on(%)