XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3331
100 to 4000 g/t leads to an increase in lithium concen-
trate from 1.0 to 1.45%. However, the recovery rate ini-
tially increases from 15.1% to 20.5% as the starch dosage
is increased from 100 to 1000 g/t, but then declines as the
starch dosage is further increased. A maximum recovery
rate of 25.0% is achieved with an increase in starch dosage
from 2000 g/t to 4000 g/t. Flotation recovery and grade of
lithium increased with the increases in dextrin concentra-
tion. The highest recovery of 52.5% and lithium grade of
1.20% were reached when dextrin concentration increased
from 100 to 4000 g/t. These results indicated that dextrin
presented an excellent selective depression effect on spodu-
mene compared to starch.
Zeta Potential
The zeta potential of spodumene is significantly influenced
by the pH of the flotation slurry. The charge at the min-
eral surface is formed when the mineral enters a solution
and depending on the conditions of the solution, the sur-
face of the mineral gains a charge neutralising the charge
of the solution (Filippov et al., 2019). The zeta potential
of low-grade spodumene ore in the presence of NaOL
(1000 g/t), DAA (1000 g/t) and mixed NaOL/DAA (ratio
of 1:5, 1000 g/t) with the increase of pH from 4 to 12 are
shown in Figure 11. In reverse flotation, the zeta potential
becomes increasingly negative at higher pH levels up to pH
10 in the presence of DAA and a mixture of NaOL/DAA.
This is similar to the flotation recovery and grade results
seen at different pH levels in Figure 7. In fact, the optimum
flotation recovery and lithium grade were obtained at pH
10 in the presence of NaOL/DAA, when spodumene is
highly negatively charged. At this pH, the spodumene sur-
face is capable of the maximum number of interactions with
the positively charged sites. With DAA, the zeta potential
at pH 4 is positively charged and rises with pH, indicat-
ing DAA’s stronger electronegativity (Wang et al., 2014).
In a mixed NaOL/DAA environment, the zeta potential
also decreases, suggesting that an optimal mix can thin the
adsorbed layer on minerals, aiding in reverse flotation desil-
ication. This mixture likely enhances flotation efficiency
by combining NaOL’s negative charge with DAA’s posi-
tive charge, resulting in a longer hydrophobic carbon chain
(Bian et al., 2023). However, further clarification is needed
on how NaOL’s adsorption on specific minerals directly
relates to zeta potential trends and the detailed interaction
mechanism between NaOL and DAA in the mixture.
XRD Measurement
An XRD analysis was carried out to identify the main
mineralogical phases present for the flotation concentrate
generated in the presence of dextrin (4000 g/t) added to
the mixture of NaOL/DAA (ratio of 1:5, 1000g/t, pH 10),
which achieved the highest lithium recovery and grade.
The gangue minerals such as feldspar, quartz and mus-
covite remain at high concentrations and have not been
completely separated. Meanwhile, the mass fraction of
spodumene in the concentrate increased slightly. The addi-
tion of dextrin appears to modify the surface properties of
spodumene, making it more hydrophilic and less prone
to being recovered in the froth, which explains the slight
increase in spodumene concentration. The slight increase
in spodumene concentration, despite overall depression,
is consistent with similar studies that have observed chal-
lenges in achieving high-grade spodumene concentrates
from ores with lower lithium content (Sousa et al., 2000,
Dessemond et al., 2019, Bian et al., 2023). These studies
have noted that high-grade spodumene concentrates could
only be obtained from ores with higher lithium content
after multiple cleaning stages. XRD patterns of feed sam-
ple and flotation products (concentrate and tailing) were
shown in Figure 12.
CONCLUSION
In this study, the DMS and flotation behavior of mixed
collector composed of NaOL and DAA to recover lithium
from low-grade spodumene ore have been investigated.
Pre-concentration using DMS processed the 1000/+850
-40
-30
-20
-10
0
10
20
4 6 8 10 12
pH
NaOL DAA NaOL/DAA
Figure 11. Zeta potential measurement results of flotation
concentration as a function of pH
Zeta
potential
(mv)
100 to 4000 g/t leads to an increase in lithium concen-
trate from 1.0 to 1.45%. However, the recovery rate ini-
tially increases from 15.1% to 20.5% as the starch dosage
is increased from 100 to 1000 g/t, but then declines as the
starch dosage is further increased. A maximum recovery
rate of 25.0% is achieved with an increase in starch dosage
from 2000 g/t to 4000 g/t. Flotation recovery and grade of
lithium increased with the increases in dextrin concentra-
tion. The highest recovery of 52.5% and lithium grade of
1.20% were reached when dextrin concentration increased
from 100 to 4000 g/t. These results indicated that dextrin
presented an excellent selective depression effect on spodu-
mene compared to starch.
Zeta Potential
The zeta potential of spodumene is significantly influenced
by the pH of the flotation slurry. The charge at the min-
eral surface is formed when the mineral enters a solution
and depending on the conditions of the solution, the sur-
face of the mineral gains a charge neutralising the charge
of the solution (Filippov et al., 2019). The zeta potential
of low-grade spodumene ore in the presence of NaOL
(1000 g/t), DAA (1000 g/t) and mixed NaOL/DAA (ratio
of 1:5, 1000 g/t) with the increase of pH from 4 to 12 are
shown in Figure 11. In reverse flotation, the zeta potential
becomes increasingly negative at higher pH levels up to pH
10 in the presence of DAA and a mixture of NaOL/DAA.
This is similar to the flotation recovery and grade results
seen at different pH levels in Figure 7. In fact, the optimum
flotation recovery and lithium grade were obtained at pH
10 in the presence of NaOL/DAA, when spodumene is
highly negatively charged. At this pH, the spodumene sur-
face is capable of the maximum number of interactions with
the positively charged sites. With DAA, the zeta potential
at pH 4 is positively charged and rises with pH, indicat-
ing DAA’s stronger electronegativity (Wang et al., 2014).
In a mixed NaOL/DAA environment, the zeta potential
also decreases, suggesting that an optimal mix can thin the
adsorbed layer on minerals, aiding in reverse flotation desil-
ication. This mixture likely enhances flotation efficiency
by combining NaOL’s negative charge with DAA’s posi-
tive charge, resulting in a longer hydrophobic carbon chain
(Bian et al., 2023). However, further clarification is needed
on how NaOL’s adsorption on specific minerals directly
relates to zeta potential trends and the detailed interaction
mechanism between NaOL and DAA in the mixture.
XRD Measurement
An XRD analysis was carried out to identify the main
mineralogical phases present for the flotation concentrate
generated in the presence of dextrin (4000 g/t) added to
the mixture of NaOL/DAA (ratio of 1:5, 1000g/t, pH 10),
which achieved the highest lithium recovery and grade.
The gangue minerals such as feldspar, quartz and mus-
covite remain at high concentrations and have not been
completely separated. Meanwhile, the mass fraction of
spodumene in the concentrate increased slightly. The addi-
tion of dextrin appears to modify the surface properties of
spodumene, making it more hydrophilic and less prone
to being recovered in the froth, which explains the slight
increase in spodumene concentration. The slight increase
in spodumene concentration, despite overall depression,
is consistent with similar studies that have observed chal-
lenges in achieving high-grade spodumene concentrates
from ores with lower lithium content (Sousa et al., 2000,
Dessemond et al., 2019, Bian et al., 2023). These studies
have noted that high-grade spodumene concentrates could
only be obtained from ores with higher lithium content
after multiple cleaning stages. XRD patterns of feed sam-
ple and flotation products (concentrate and tailing) were
shown in Figure 12.
CONCLUSION
In this study, the DMS and flotation behavior of mixed
collector composed of NaOL and DAA to recover lithium
from low-grade spodumene ore have been investigated.
Pre-concentration using DMS processed the 1000/+850
-40
-30
-20
-10
0
10
20
4 6 8 10 12
pH
NaOL DAA NaOL/DAA
Figure 11. Zeta potential measurement results of flotation
concentration as a function of pH
Zeta
potential
(mv)