XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1347
of deep eutectic solvents for ores obtained from different
domains of the deposit and mine wastes, such as float tails
and acid-crack leach tails.
MATERIALS AND METHODS
This study made two different DES: choline chloride
(ChCl) +urea and ChCl +Ethylene Glycol (EG). These
solutions are termed reline and ethaline, respectively. These
solvents can be prepared using several methods, and the
heating and stirring method proposed by (Farooq, Abbasi,
and Anderson 2020) was followed to prepare the solvents.
Experiments were carried out with feed samples of different
grades and mineralogy to test the employability of the pre-
pared solvents. The samples were obtained from a currently
operating REE processing plant. The samples include sub-
economical ores, flotation tailings, and acid-crack leach
tailings. The ores and flotation tailings consist of mona-
zite, florencite, goethite, and apatite. The acid crack and
leach residues comprise iron phosphates with several REE-
bearing phases. The samples were either crushed or ground,
depending on their nature. This was done to ensure surface
liberation and homogeneity. The composition of the sam-
ples is mentioned in the results section.
A conical flask fitted with a rubber stopper was placed
on a heating mantle for leaching experiments. To ensure
thorough mixing and prevent settling, the mixture was
stirred using a magnetic stirrer at 250 rpm, and a 1:10
solid-to-liquid ratio was maintained. The solution samples
were taken at 1, 6, 24, and 48 hours. The obtained solu-
tions were diluted with 2% HNO3 in a 1:20 ratio. The con-
centration of the elements in the diluted solution was then
determined using an inductively coupled plasma-optical
emission spectroscopy (ICP-OES).
RESULTS &DISCUSSION
Feed Characterisation
The different feeds were ground in stages, and aqua regia
digestion was done to find the elemental composition of
the different feedstocks. The composition of the different
feeds is given in Table 1. The total rare earth element is
abbreviated to TREE for ease.
In ore A, the rare earths are hosted as low-grade mona-
zite ore. In the case of ore B, the rare earth elements are
found in sub-micron particles of the florencite matrix, mak-
ing them refractory to the conventional process. The other
gangue minerals include goethite and apatite. Float and
leach tails are the products generated from the conventional
processing route. The float tails include apatite, florencite,
and goethite. In the case of leach tails, iron phosphates are
the major constituent. The rare earth elements are hosted in
unreacted monazite (phosphates) and sulphates.
The ground feeds were subjected to laser sizing. The
results obtained are presented in Table 2, and it is apparent
that the feed samples are relatively fine.
DES Properties and Leach Behaviour
Reline
A mixture of choline chloride (ChCl) and urea at a 1:2
molar ratio is called reline. Studies have reported differ-
ent measured values for the eutectic transformation tem-
perature, such as 12°C and 50°C. However, it was observed
that the first solid appeared when the temperature dropped
below 35°C. The prepared solvent was highly viscous, and
the studies reported a viscosity of 750 cP at 25°C and
129 cP at 40°C (Zhang et al. 2012). Therefore, experiments
were carried out at 80°C to avoid the hydrodynamics issue.
Experiments were planned to run for 48 hours, and
leach samples were planned to be taken at 1, 6, 24, and 48
hours. However, when the samples were taken after the 1st
hour, it was hard to achieve solid-liquid separation because
of the high viscosity of the sample. Different attempts like
centrifuging and vacuum filtration were tried but did not
achieve good separation. Further test work is to be done
to ensure solid-liquid separation, and then the liquid is to
Table 2. Particle size distribution of the samples
Feed Samples Ore A Ore B
Float
Tails
ACL
Tails
p
80 (µm) 56.9 30.6 34.9 25.3
Table 1. Elemental composition of the samples
Elemental
Composition, %Al Ca Ce Fe La Mn Nd P Pr Th T-REE
Ore A 1.75 0.37 3.24 35.80 1.58 2.66 1.67 2.41 0.39 0.22 6.94
Ore B 2.68 0.22 3.21 26.51 1.68 0.53 1.59 2.21 0.39 0.24 6.87
Float Tails 1.73 0.30 2.17 33.83 0.96 2.84 1.02 1.22 0.22 0.14 4.39
ACL Tails 2.42 1.63 1.23 20.70 0.61 0.21 0.74 8.16 0.18 0.20 2.79
of deep eutectic solvents for ores obtained from different
domains of the deposit and mine wastes, such as float tails
and acid-crack leach tails.
MATERIALS AND METHODS
This study made two different DES: choline chloride
(ChCl) +urea and ChCl +Ethylene Glycol (EG). These
solutions are termed reline and ethaline, respectively. These
solvents can be prepared using several methods, and the
heating and stirring method proposed by (Farooq, Abbasi,
and Anderson 2020) was followed to prepare the solvents.
Experiments were carried out with feed samples of different
grades and mineralogy to test the employability of the pre-
pared solvents. The samples were obtained from a currently
operating REE processing plant. The samples include sub-
economical ores, flotation tailings, and acid-crack leach
tailings. The ores and flotation tailings consist of mona-
zite, florencite, goethite, and apatite. The acid crack and
leach residues comprise iron phosphates with several REE-
bearing phases. The samples were either crushed or ground,
depending on their nature. This was done to ensure surface
liberation and homogeneity. The composition of the sam-
ples is mentioned in the results section.
A conical flask fitted with a rubber stopper was placed
on a heating mantle for leaching experiments. To ensure
thorough mixing and prevent settling, the mixture was
stirred using a magnetic stirrer at 250 rpm, and a 1:10
solid-to-liquid ratio was maintained. The solution samples
were taken at 1, 6, 24, and 48 hours. The obtained solu-
tions were diluted with 2% HNO3 in a 1:20 ratio. The con-
centration of the elements in the diluted solution was then
determined using an inductively coupled plasma-optical
emission spectroscopy (ICP-OES).
RESULTS &DISCUSSION
Feed Characterisation
The different feeds were ground in stages, and aqua regia
digestion was done to find the elemental composition of
the different feedstocks. The composition of the different
feeds is given in Table 1. The total rare earth element is
abbreviated to TREE for ease.
In ore A, the rare earths are hosted as low-grade mona-
zite ore. In the case of ore B, the rare earth elements are
found in sub-micron particles of the florencite matrix, mak-
ing them refractory to the conventional process. The other
gangue minerals include goethite and apatite. Float and
leach tails are the products generated from the conventional
processing route. The float tails include apatite, florencite,
and goethite. In the case of leach tails, iron phosphates are
the major constituent. The rare earth elements are hosted in
unreacted monazite (phosphates) and sulphates.
The ground feeds were subjected to laser sizing. The
results obtained are presented in Table 2, and it is apparent
that the feed samples are relatively fine.
DES Properties and Leach Behaviour
Reline
A mixture of choline chloride (ChCl) and urea at a 1:2
molar ratio is called reline. Studies have reported differ-
ent measured values for the eutectic transformation tem-
perature, such as 12°C and 50°C. However, it was observed
that the first solid appeared when the temperature dropped
below 35°C. The prepared solvent was highly viscous, and
the studies reported a viscosity of 750 cP at 25°C and
129 cP at 40°C (Zhang et al. 2012). Therefore, experiments
were carried out at 80°C to avoid the hydrodynamics issue.
Experiments were planned to run for 48 hours, and
leach samples were planned to be taken at 1, 6, 24, and 48
hours. However, when the samples were taken after the 1st
hour, it was hard to achieve solid-liquid separation because
of the high viscosity of the sample. Different attempts like
centrifuging and vacuum filtration were tried but did not
achieve good separation. Further test work is to be done
to ensure solid-liquid separation, and then the liquid is to
Table 2. Particle size distribution of the samples
Feed Samples Ore A Ore B
Float
Tails
ACL
Tails
p
80 (µm) 56.9 30.6 34.9 25.3
Table 1. Elemental composition of the samples
Elemental
Composition, %Al Ca Ce Fe La Mn Nd P Pr Th T-REE
Ore A 1.75 0.37 3.24 35.80 1.58 2.66 1.67 2.41 0.39 0.22 6.94
Ore B 2.68 0.22 3.21 26.51 1.68 0.53 1.59 2.21 0.39 0.24 6.87
Float Tails 1.73 0.30 2.17 33.83 0.96 2.84 1.02 1.22 0.22 0.14 4.39
ACL Tails 2.42 1.63 1.23 20.70 0.61 0.21 0.74 8.16 0.18 0.20 2.79