1178 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
In the complex practical flotation of actual ores, it is
the difference in the flotation rates of scheelite, wolframite
and cassiterite, directly leads to the difficulty in achieving
co-enrichment of tungsten and tin[17]. Therefore, research
was conducted on the flotation rates of these minerals at
different pH, and the experimental results are depicted in
Figure 6.
The cumulative flotation recovery rates and variation
trend of these minerals at different pH levels exhibit sig-
nificant differences. For scheelite, the cumulative recovery
rates at each time interval are the highest at pH 9.0, with
the cumulative recovery rate exceeding 80% at 60 second.
The flotation of scheelite at pH 8.5 follows closely, with a
cumulative recovery rate approaching 60% at 60 seconds.
At pH 9.5, while the initial cumulative recovery rate mir-
rors that of pH 8.5 within the first 36 seconds, the sub-
sequent increase in the cumulative recovery rate proceeds
more gradually as the flotation time extends. This indicates
that the flotation of scheelite is suitable within the pH
range of 8.5–9.0, where higher flotation rates and cumula-
tive recovery rates can be attained.
At pH 9.5, the cumulative flotation recovery rates of
wolframite are the highest at each time interval, with the
cumulative recovery rate exceeding 70% at 60 seconds,
showing a rapid growth in the cumulative recovery rate in
the first 60 seconds, followed by a more gradual trend. At
pH 10.0, the flotation rate of wolframite is slightly lower
than at pH 9.5, representing the second highest point, indi-
cating that the flotation of wolframite is suitable within the
pH range of 9.5–10.0. The trend of the flotation rate of
cassiterite concerning pH variation is similar to that of wol-
framite. At pH 9.5, the cumulative flotation recovery rates
of cassiterite are the highest at each time interval, with the
cumulative recovery rate exceeding 50% at 60 seconds and
exhibiting rapid growth in the cumulative recovery rate in
the first 60 seconds, followed by a more gradual trend. At
pH 10.0, the flotation rate of cassiterite is slightly lower
than at pH 9.5, representing the second highest point,
indicating that the flotation of cassiterite also is suitable
within the pH range of 9.5–10.0.
The Molecular Obit Analysis of Mineral Surfaces
Flotation is a technology to regulates the hydrophobicity
of a mineral surface through reagents, so the nature of the
mineral surface and the adsorption of reagents on its surface
are the keys to flotation[18]. Besides, the adsorption con-
figuration of Pb-BHA was investigated through DFT cal-
culation, and the results manifested that the oxygen atom
loses electrons, while the lead ion gains electrons in the
bonding process between the lead ion and the oxygen atom
on the surface of the mineral, as shown in Figure 7 [19].
Therefore, the EHOMO could directly determine the pos-
sibility of Pb-BHA adsorption, and the higher the EHOMO,
the more easily the adsorption occurs[15].
The common cleavage planes of scheelite, wolframite,
and cassiterite are (112), (010), and (100), respectively, as
shown in Figure 8. The EHOMO and ELUMO of scheelite,
wolframite, and cassiterite were calculated to explain their
different flotation behavior. As shown in Table 4, the order
of |EHOMO(minerals)-ELUMO(Pb-BHA)| is scheelite wolfram-
ite cassiterite. Cassiterite and wolframite have higher
reactivity with Pb-BHA than scheelite, but they have lower
flotation rates than scheelite, which should be attributed to
their surface hydration in the pulp. The HOMO-LUMO
gap (ΔE) of mineral surfaces can represent their natural
reactivity, and lower ΔE reflects higher reactivity. Given the
flotation is conducted in the water environment, mineral
surfaces experience hydration before their interaction with
Pb-BHA[20]. The smaller ΔE implies a greater unsatura-
tion of the surfaces of cassiterite and wolframite, as shown
in Table 5, resulting in stronger adsorption of polar water
molecules on their surfaces and the formation of thicker
hydration layers, hindering the adsorption of reagents. As
shown in Figure 9, the Pb-BHA adsorption on wolfram-
ite and cassiterite requires more energy to repel the denser
Figure 6. The flotation rate curves of scheelite(a), wolframite(b), and cassiterite(c) at different pH
In the complex practical flotation of actual ores, it is
the difference in the flotation rates of scheelite, wolframite
and cassiterite, directly leads to the difficulty in achieving
co-enrichment of tungsten and tin[17]. Therefore, research
was conducted on the flotation rates of these minerals at
different pH, and the experimental results are depicted in
Figure 6.
The cumulative flotation recovery rates and variation
trend of these minerals at different pH levels exhibit sig-
nificant differences. For scheelite, the cumulative recovery
rates at each time interval are the highest at pH 9.0, with
the cumulative recovery rate exceeding 80% at 60 second.
The flotation of scheelite at pH 8.5 follows closely, with a
cumulative recovery rate approaching 60% at 60 seconds.
At pH 9.5, while the initial cumulative recovery rate mir-
rors that of pH 8.5 within the first 36 seconds, the sub-
sequent increase in the cumulative recovery rate proceeds
more gradually as the flotation time extends. This indicates
that the flotation of scheelite is suitable within the pH
range of 8.5–9.0, where higher flotation rates and cumula-
tive recovery rates can be attained.
At pH 9.5, the cumulative flotation recovery rates of
wolframite are the highest at each time interval, with the
cumulative recovery rate exceeding 70% at 60 seconds,
showing a rapid growth in the cumulative recovery rate in
the first 60 seconds, followed by a more gradual trend. At
pH 10.0, the flotation rate of wolframite is slightly lower
than at pH 9.5, representing the second highest point, indi-
cating that the flotation of wolframite is suitable within the
pH range of 9.5–10.0. The trend of the flotation rate of
cassiterite concerning pH variation is similar to that of wol-
framite. At pH 9.5, the cumulative flotation recovery rates
of cassiterite are the highest at each time interval, with the
cumulative recovery rate exceeding 50% at 60 seconds and
exhibiting rapid growth in the cumulative recovery rate in
the first 60 seconds, followed by a more gradual trend. At
pH 10.0, the flotation rate of cassiterite is slightly lower
than at pH 9.5, representing the second highest point,
indicating that the flotation of cassiterite also is suitable
within the pH range of 9.5–10.0.
The Molecular Obit Analysis of Mineral Surfaces
Flotation is a technology to regulates the hydrophobicity
of a mineral surface through reagents, so the nature of the
mineral surface and the adsorption of reagents on its surface
are the keys to flotation[18]. Besides, the adsorption con-
figuration of Pb-BHA was investigated through DFT cal-
culation, and the results manifested that the oxygen atom
loses electrons, while the lead ion gains electrons in the
bonding process between the lead ion and the oxygen atom
on the surface of the mineral, as shown in Figure 7 [19].
Therefore, the EHOMO could directly determine the pos-
sibility of Pb-BHA adsorption, and the higher the EHOMO,
the more easily the adsorption occurs[15].
The common cleavage planes of scheelite, wolframite,
and cassiterite are (112), (010), and (100), respectively, as
shown in Figure 8. The EHOMO and ELUMO of scheelite,
wolframite, and cassiterite were calculated to explain their
different flotation behavior. As shown in Table 4, the order
of |EHOMO(minerals)-ELUMO(Pb-BHA)| is scheelite wolfram-
ite cassiterite. Cassiterite and wolframite have higher
reactivity with Pb-BHA than scheelite, but they have lower
flotation rates than scheelite, which should be attributed to
their surface hydration in the pulp. The HOMO-LUMO
gap (ΔE) of mineral surfaces can represent their natural
reactivity, and lower ΔE reflects higher reactivity. Given the
flotation is conducted in the water environment, mineral
surfaces experience hydration before their interaction with
Pb-BHA[20]. The smaller ΔE implies a greater unsatura-
tion of the surfaces of cassiterite and wolframite, as shown
in Table 5, resulting in stronger adsorption of polar water
molecules on their surfaces and the formation of thicker
hydration layers, hindering the adsorption of reagents. As
shown in Figure 9, the Pb-BHA adsorption on wolfram-
ite and cassiterite requires more energy to repel the denser
Figure 6. The flotation rate curves of scheelite(a), wolframite(b), and cassiterite(c) at different pH