XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1281
with gangue. Without grinding to liberate them they could
hardly be efficiently separated.
Flotation
The shaking table concentrate was ground first using a ball
mill to enhance the liberations of REEs-bearing minerals
and apatite, and then it was beneficiated through flotation.
Sodium carbonate was used as adjustor for pulp pH, sodium
silicate as depressant for gangue, and sodium oleate as col-
lector for REE and phosphate minerals. The concentration
of flotation pulp was 30% wt%, operating conditions were
optimized through a series of tests, and the results of these
tests are shown in Figure 1, 2, 3, and 4. Based on these
results the appropriate operating conditions were deter-
mined as grinding fineness 52.70 wt% of particles with size
below 200 mesh (0.074 mm) in grinding product, pulp pH
9.5, depressant addition 0.55 kg/t tails feed, collector addi-
tion 1.2 kg/t tails feed. After that a roughing flotation test
was carried out under these optimized conditions and the
results are shown in Table 5.
The results in Table 5 indicate that the shaking table
concentrate can be further upgraded through flotation after
grinding. But the P2O5 content in this flotation concentrate
was only 14.90%, much lower than 28% in the current
“Crago” flotation concentrate for phosphoric acid produc-
tion. And it was found during the tests that the grade of
flotation concentrate could hardly be further improved,
especially for P2O5 content, even if the grinding fineness
was increased to above 52.70 wt% of particles with size
below 200 mesh, which can be attributed to the dissemina-
tion of most valuable minerals as micro-fine particles in the
amine flotation sample. Contents of main chemical com-
ponents and REEs in the concentrate are listed in Table 6.
Leaching
The leaching method of CSAP – WL as mentioned above is
a common process to decompose REE minerals including
monazite. The influence of sulfuric acid addition on leach-
ing efficiencies of REEs and phosphorus was tested, and the
results are shown in Figure 5.
Figure 5. Change of leaching efficiency with sulfuric
acid addition
As shown in Figure 5, the leaching efficiency of
REEs increased first with the rise of stoichiometric ratio
of H2SO4 to CaO. When the ratio increased to 3.61, the
REEs leaching efficiency reached 85.54%, and then leveled
off. However, the P2O5 leaching efficiency showed a dif-
ferent variation trend. It changed within a narrow range of
Table 4. Results of shaking table separation
Product Yield, %REEs Content, ppm P2O5 Content, %
Recovery, %
REEs P2O5
Concentrate 12.51 657.39 8.00 40.73 33.12
Tailings 87.49 136.77 2.31 59.27 66.88
Calculated feed 100.00 201.90 3.02 100.00 100.00
Table 5. Results of flotation
Product Yield, %REEs content, ppm P2O5 Content, %
Recovery, %
REEs P2O5
Concentrate 49.23 1105.82 14.90 85.91 89.81
Tailings 50.77 192.84 1.64 14.09 10.19
Calculated feed 100.00 664.46 8.17 100.00 100.00
Table 6. Main chemical components and rare earths in flotation concentrate
Component P2O5 CaO Fe2O3 MgO Al2O3
Content, %14.90 20.26 2.25 0.16 0.75
Element Sc Y La Ce Pr Nd
Content, ppm 8.82 243.06 175.48 336.82 20.83 267.05
Element Sm Eu Gd Tb Dy Ho
Content, ppm 0.00 6.44 31.88 4.29 18.16 4.22
Element Er Tm Yb Lu Total REEs
Content, ppm 16.31 2.64 12.55 2.29 1150.82
with gangue. Without grinding to liberate them they could
hardly be efficiently separated.
Flotation
The shaking table concentrate was ground first using a ball
mill to enhance the liberations of REEs-bearing minerals
and apatite, and then it was beneficiated through flotation.
Sodium carbonate was used as adjustor for pulp pH, sodium
silicate as depressant for gangue, and sodium oleate as col-
lector for REE and phosphate minerals. The concentration
of flotation pulp was 30% wt%, operating conditions were
optimized through a series of tests, and the results of these
tests are shown in Figure 1, 2, 3, and 4. Based on these
results the appropriate operating conditions were deter-
mined as grinding fineness 52.70 wt% of particles with size
below 200 mesh (0.074 mm) in grinding product, pulp pH
9.5, depressant addition 0.55 kg/t tails feed, collector addi-
tion 1.2 kg/t tails feed. After that a roughing flotation test
was carried out under these optimized conditions and the
results are shown in Table 5.
The results in Table 5 indicate that the shaking table
concentrate can be further upgraded through flotation after
grinding. But the P2O5 content in this flotation concentrate
was only 14.90%, much lower than 28% in the current
“Crago” flotation concentrate for phosphoric acid produc-
tion. And it was found during the tests that the grade of
flotation concentrate could hardly be further improved,
especially for P2O5 content, even if the grinding fineness
was increased to above 52.70 wt% of particles with size
below 200 mesh, which can be attributed to the dissemina-
tion of most valuable minerals as micro-fine particles in the
amine flotation sample. Contents of main chemical com-
ponents and REEs in the concentrate are listed in Table 6.
Leaching
The leaching method of CSAP – WL as mentioned above is
a common process to decompose REE minerals including
monazite. The influence of sulfuric acid addition on leach-
ing efficiencies of REEs and phosphorus was tested, and the
results are shown in Figure 5.
Figure 5. Change of leaching efficiency with sulfuric
acid addition
As shown in Figure 5, the leaching efficiency of
REEs increased first with the rise of stoichiometric ratio
of H2SO4 to CaO. When the ratio increased to 3.61, the
REEs leaching efficiency reached 85.54%, and then leveled
off. However, the P2O5 leaching efficiency showed a dif-
ferent variation trend. It changed within a narrow range of
Table 4. Results of shaking table separation
Product Yield, %REEs Content, ppm P2O5 Content, %
Recovery, %
REEs P2O5
Concentrate 12.51 657.39 8.00 40.73 33.12
Tailings 87.49 136.77 2.31 59.27 66.88
Calculated feed 100.00 201.90 3.02 100.00 100.00
Table 5. Results of flotation
Product Yield, %REEs content, ppm P2O5 Content, %
Recovery, %
REEs P2O5
Concentrate 49.23 1105.82 14.90 85.91 89.81
Tailings 50.77 192.84 1.64 14.09 10.19
Calculated feed 100.00 664.46 8.17 100.00 100.00
Table 6. Main chemical components and rare earths in flotation concentrate
Component P2O5 CaO Fe2O3 MgO Al2O3
Content, %14.90 20.26 2.25 0.16 0.75
Element Sc Y La Ce Pr Nd
Content, ppm 8.82 243.06 175.48 336.82 20.83 267.05
Element Sm Eu Gd Tb Dy Ho
Content, ppm 0.00 6.44 31.88 4.29 18.16 4.22
Element Er Tm Yb Lu Total REEs
Content, ppm 16.31 2.64 12.55 2.29 1150.82