XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 661
RESULTS AND DISCUSSION
The main rare earth elements bearing minerals in the ore are
monazite and florencite as shown from the mineralogical
analysis given in Figure 1. In the flotation of monazite and
other rare earth bearing minerals, fatty acid-based collec-
tors are commonly used (Abaka-Wood et al., 2017a Jung
et al., 2022 Jung et al., 2024). Thus, in this study a fatty
acid-based collector, namely, tall oil, was used to as a collec-
tor for rare earth flotation. In addition, Figure 1 indicates
that goethite was found to be the primary gangue mineral
in the ore. Thus, a sodium silicate depressant was used to
suppress the co-flotation of goethite (Abaka-Wood et al.,
2017b Qi, 1993).
REO Recovery in Various Water Compositions
The effect of water quality on rare earth oxide flotation was
investigated by comparing recovery and grades after flota-
tion in various water systems. The flotation performance of
REO in tap water, bore water, nanofiltration purified water,
and a 50:50 v/v NF and bore water mixture are shown in
Figure 3. In each case higher recoveries are recorded for the
first stage of flotation (rougher/scavenger) and higher grades
are obtained in the second cleaner stage. It can be seen from
Figure 3 that water quality has significant impact on flota-
tion performance. The flotation recovery and REO grade
drops considerably when bore water used in comparison
with NF or tap water. This decrease in flotation perfor-
mance with bore water can be attributed to the higher Ca2+
and Mg2+ ions concentration present in bore water.
Effect of Major Ions of REO Flotation
To better understand the effects of ions on REO flotation,
the major cations present in the bore water (i.e., Na+, K+,
Mg2+ and Ca2+ from Table 2) were individually studied. In
order to determine the effect of each main cations in the
bore water, separate solutions of various concentrations of
CaCl2, MgCl2, NaCl and KCl were prepared and used to
make up the pulp. Figures 4–7 depict the comparisons of
flotation recovery and grade of REO for various water com-
positions. It can be seen that the addition of Mg2+ and Ca2+
has significant impact on flotation of REO. The presence of
500 ppm Ca2+ and Mg2+ ions led to very low REO grade
in the concentrate.
The introduction of cations such as Ca2+ and Mg2+
from impure water during rare earth flotation can lead to
the formation of hydrophilic hydroxide species which will
inhibit collector molecule adsorption (Zhang et al., 2017).
In addition, these ions can result in the reduction in fatty
acid collector concentration in the flotation pulp due to the
formation of insoluble compounds such as Ca(RCOO)2 or
Mg(RCOO)2 (Jung et al., 2024). The presence of Ca2+ may
activate the flotation of gangue silicates and hydroxides at
Figure 3. Flotation recovery and grade of rare earth oxides in various water types
RESULTS AND DISCUSSION
The main rare earth elements bearing minerals in the ore are
monazite and florencite as shown from the mineralogical
analysis given in Figure 1. In the flotation of monazite and
other rare earth bearing minerals, fatty acid-based collec-
tors are commonly used (Abaka-Wood et al., 2017a Jung
et al., 2022 Jung et al., 2024). Thus, in this study a fatty
acid-based collector, namely, tall oil, was used to as a collec-
tor for rare earth flotation. In addition, Figure 1 indicates
that goethite was found to be the primary gangue mineral
in the ore. Thus, a sodium silicate depressant was used to
suppress the co-flotation of goethite (Abaka-Wood et al.,
2017b Qi, 1993).
REO Recovery in Various Water Compositions
The effect of water quality on rare earth oxide flotation was
investigated by comparing recovery and grades after flota-
tion in various water systems. The flotation performance of
REO in tap water, bore water, nanofiltration purified water,
and a 50:50 v/v NF and bore water mixture are shown in
Figure 3. In each case higher recoveries are recorded for the
first stage of flotation (rougher/scavenger) and higher grades
are obtained in the second cleaner stage. It can be seen from
Figure 3 that water quality has significant impact on flota-
tion performance. The flotation recovery and REO grade
drops considerably when bore water used in comparison
with NF or tap water. This decrease in flotation perfor-
mance with bore water can be attributed to the higher Ca2+
and Mg2+ ions concentration present in bore water.
Effect of Major Ions of REO Flotation
To better understand the effects of ions on REO flotation,
the major cations present in the bore water (i.e., Na+, K+,
Mg2+ and Ca2+ from Table 2) were individually studied. In
order to determine the effect of each main cations in the
bore water, separate solutions of various concentrations of
CaCl2, MgCl2, NaCl and KCl were prepared and used to
make up the pulp. Figures 4–7 depict the comparisons of
flotation recovery and grade of REO for various water com-
positions. It can be seen that the addition of Mg2+ and Ca2+
has significant impact on flotation of REO. The presence of
500 ppm Ca2+ and Mg2+ ions led to very low REO grade
in the concentrate.
The introduction of cations such as Ca2+ and Mg2+
from impure water during rare earth flotation can lead to
the formation of hydrophilic hydroxide species which will
inhibit collector molecule adsorption (Zhang et al., 2017).
In addition, these ions can result in the reduction in fatty
acid collector concentration in the flotation pulp due to the
formation of insoluble compounds such as Ca(RCOO)2 or
Mg(RCOO)2 (Jung et al., 2024). The presence of Ca2+ may
activate the flotation of gangue silicates and hydroxides at
Figure 3. Flotation recovery and grade of rare earth oxides in various water types