XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3369
the representative sample was mixed with 100 mL of the
required acid solution, in an Erlenmeyer flask and placed
in the water bath at the required leaching temperature of
80 °C and shaking speed of 200rev/min. Solution samples
were taken at different time intervals between 1 hour and
24 hours, then filtered using the centrifuge, to obtain solu-
tions for subsequent chemical analysis by the ICP-OES.
The leaching recoveries were computed using the formula
shown in Eq. (1).
The leaching efficiency was calculated using the
formula:
R C M
C V
100
o
m )
)
)=(1)
R =Percentage of recovery, for the metal of interest
Cm =metal ion concentration in leach solution (g/mL)
V =volume of leach solution (L)
Co =metal content of feed (%)
M =mass of ore
Three organic acids, including citric, tartaric, and
oxalic acids were evaluated for their leaching performance
to determine the most effective leaching agent. The varied
parameters were acid type and time, while the acid con-
centration, S/L ratio, and leaching temperature were kept
constant. Under the same conditions as organic acids, sul-
furic acid was used to compare their leaching performance
with the other acids. The acid types and the values used for
constant parameters were chosen as a result of their effec-
tiveness in metal extraction from other research and from
an average of values used in previous research [34, 35]. The
dissolution of the metals Li, Ca, Mg, Al, and Fe will be
studied and the variation in dissolution between sulfuric
acid and the organic acids will be evaluated, as well as the
difference among the organic acids will be evaluated. The
acid with the highest natural selectivity of Li will be consid-
ered best for the leaching of claystone.
RESULTS AND DISCUSSION
Elemental and Mineralogical Studies
The mineralogical characteristics of the claystone were
investigated through XRD analyses. The XRD was used
to identify the principal mineral phases, and the obtained
spectrum underwent additional analysis using the
DIFFRAC.EVA software. The major mineral phases identi-
fied included carbonates, feldspar and plagioclase minerals,
and phyllosilicate clay minerals. The carbonates identified
were calcite, dolomite, illite, hectorite, tainiolite, heden-
bergite, albite, quartz, and feldspar (Figure 2). The most
prevalent peaks with the highest XRD intensity were the
peaks representing dolomite, notably the peak at 2θ =31.1,
indicating the high presence of dolomite in the claystone.
The claystone sample which was pulverized before all
experiments was analyzed to determine the particle size dis-
tribution of the sample. The particle size distribution was
achieved using the particle size analyzer, and the analysis
was done wet, due to the “false” distribution usually given
by dry screening as a result of agglomeration of clay parti-
cles. The graph obtained from the results of the wet particle
size analysis (Figure 3) gave a p80 of 296 µm. This value
indicates that our sample was partially pulverized, owing to
the soft nature of the claystone sample. Therefore energy is
minimized to achieve a considerable surface area for subse-
quent leaching.
The elemental characterization was carried out by an
aqua regia digestion method, followed by ICP-OES analy-
sis. The major elements are shown in Table 1. Because this
was a Li-bearing claystone, about 2000 ppm of Li was
detected in the sample. The findings in Table 1 reveal that
Mg has the highest metal concentration followed by Ca.
This correlates with the XRD results, as we saw the major
peaks representing dolomite. From this information, Mg
is treated as the main impurity in subsequent experiments,
hence any acid that naturally seeks to reduce its value in
the system will be considered valuable and taken into great
consideration.
Figure 1. Experimental set-up of the leaching process, using
the GYROMAX™ 929 water bath
the representative sample was mixed with 100 mL of the
required acid solution, in an Erlenmeyer flask and placed
in the water bath at the required leaching temperature of
80 °C and shaking speed of 200rev/min. Solution samples
were taken at different time intervals between 1 hour and
24 hours, then filtered using the centrifuge, to obtain solu-
tions for subsequent chemical analysis by the ICP-OES.
The leaching recoveries were computed using the formula
shown in Eq. (1).
The leaching efficiency was calculated using the
formula:
R C M
C V
100
o
m )
)
)=(1)
R =Percentage of recovery, for the metal of interest
Cm =metal ion concentration in leach solution (g/mL)
V =volume of leach solution (L)
Co =metal content of feed (%)
M =mass of ore
Three organic acids, including citric, tartaric, and
oxalic acids were evaluated for their leaching performance
to determine the most effective leaching agent. The varied
parameters were acid type and time, while the acid con-
centration, S/L ratio, and leaching temperature were kept
constant. Under the same conditions as organic acids, sul-
furic acid was used to compare their leaching performance
with the other acids. The acid types and the values used for
constant parameters were chosen as a result of their effec-
tiveness in metal extraction from other research and from
an average of values used in previous research [34, 35]. The
dissolution of the metals Li, Ca, Mg, Al, and Fe will be
studied and the variation in dissolution between sulfuric
acid and the organic acids will be evaluated, as well as the
difference among the organic acids will be evaluated. The
acid with the highest natural selectivity of Li will be consid-
ered best for the leaching of claystone.
RESULTS AND DISCUSSION
Elemental and Mineralogical Studies
The mineralogical characteristics of the claystone were
investigated through XRD analyses. The XRD was used
to identify the principal mineral phases, and the obtained
spectrum underwent additional analysis using the
DIFFRAC.EVA software. The major mineral phases identi-
fied included carbonates, feldspar and plagioclase minerals,
and phyllosilicate clay minerals. The carbonates identified
were calcite, dolomite, illite, hectorite, tainiolite, heden-
bergite, albite, quartz, and feldspar (Figure 2). The most
prevalent peaks with the highest XRD intensity were the
peaks representing dolomite, notably the peak at 2θ =31.1,
indicating the high presence of dolomite in the claystone.
The claystone sample which was pulverized before all
experiments was analyzed to determine the particle size dis-
tribution of the sample. The particle size distribution was
achieved using the particle size analyzer, and the analysis
was done wet, due to the “false” distribution usually given
by dry screening as a result of agglomeration of clay parti-
cles. The graph obtained from the results of the wet particle
size analysis (Figure 3) gave a p80 of 296 µm. This value
indicates that our sample was partially pulverized, owing to
the soft nature of the claystone sample. Therefore energy is
minimized to achieve a considerable surface area for subse-
quent leaching.
The elemental characterization was carried out by an
aqua regia digestion method, followed by ICP-OES analy-
sis. The major elements are shown in Table 1. Because this
was a Li-bearing claystone, about 2000 ppm of Li was
detected in the sample. The findings in Table 1 reveal that
Mg has the highest metal concentration followed by Ca.
This correlates with the XRD results, as we saw the major
peaks representing dolomite. From this information, Mg
is treated as the main impurity in subsequent experiments,
hence any acid that naturally seeks to reduce its value in
the system will be considered valuable and taken into great
consideration.
Figure 1. Experimental set-up of the leaching process, using
the GYROMAX™ 929 water bath