1284 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
88.5% -90.5% when the stoichiometric ratio of H2SO4
to CaO increased from 1.85 to 3.26. After that it rose as
the ratio increases and reached 95.33% at the applied high-
est ratio of 4.60. The sulfuric acid demand in the leaching
was much higher than the theoretical value to decompose
phosphates, which was mainly due to the high content of
impurities in the flotation concentrate.
It should be noted that the downstream REE extrac-
tion from the leachate and production of mixed REE oxide
are presented in separate papers to be published in the near
future.
CONCLUSIONS
The research results in this paper indicate that the REEs
and phosphates in the amine flotation tails could be con-
centrated and leached through the process of separation
and leaching. Gravitation separation by shaking table con-
centrated the REEs and P2O5 in the tails from about 202
ppm and 3% to 657 ppm and 8%, respectively, with a con-
centrate yield of 12.51%, achieving REEs recovery of about
41%, and P2O5 recovery of 33%. After ground, the shak-
ing table concentrate could be further upgraded through
flotation to produce a concentrate containing 1151 ppm of
REEs and 14.90% of P2O5 at REE recovery of 85.91% and
P2O5 recovery of 89.81%. Leaching tests demonstrated the
REEs and phosphorus in the flotation concentrate could be
recovered through a process of concentrated sulfuric acid
pyrolysis – water leaching, resulting in recoveries of about
85% for REE and 93% for P2O5.
However, there are still some challenges to the process-
ing approach employed in this research. One is that the
REE minerals and apatite are finely disseminated in the
amine flotation tails, with some interlocked with gangue
minerals, which led to the low recoveries of 40.73% for
REEs and 33.15% for P2O5 in shaking table separation,
and low grades of the valuables in flotation concentrate.
Both the REEs content of 1150.82 ppm and P2O5 con-
tent of 14.90% in the flotation concentrate can not meet
the requirements of current industry practice. Since the
amine flotation tails contains more than 90% (by weight)
of gangue minerals (calculated based on the P2O5 content
of 3.02%), it is not economically feasible to grind the entire
tails before removal of the majority of gangue mineral due
to high energy consumption.
The other issue is high sulfuric acid addition required
in the roasting-leaching process. All the acid additions in
the range we tested (1.85 to 4.60 of stoichiometric ratio
of H2SO4 to CaO) were much higher than the theoreti-
cal demand for decomposing phosphates, but only when
the stoichiometric ratio was above 3.26, did the leaching
efficiencies of REEs and P2O5 reached their high levels.
This phenomenon can be attributed to the high contents
of impurities such as calcite, dolomite and some Fe-bearing
minerals which consumed some acid. On the other hand,
the REEs minerals needed high concentration of sulfuric
acid for its decomposition during roasting.
ACKNOWLEDGMENTS
This research is part of a major project of the Critical
Materials Innovation (CMI) Hub (formerly Critical
Materials Institute), under subcontract number SC-14-392
funded by the US Department of Energy, Office of Energy
Efficiency and Renewable Energy, Advanced Materials &
Manufacturing Technologies Office. The guidance and
leadership provided by Bruce Moyer, CMI focus area lead,
and David DePaoli, CMI project lead, are highly appreci-
ated. Substantial matching fund is provided by the Florida
Industrial and Phosphate Research Institute, Florida
Polytechnic University. The Mosaic Co. is particularly
acknowledged for their technical input, large in-kind sup-
port, and sample collection efforts. We want to express our
gratitude to the following Mosaic employees and former
employees for their help: Nicole Christiansen, Paul Kucera,
Marcos Ortiz, Chris Dennis, Glen Oswald, Chaucer
Hwang, Cameron Weed, and Gary Whitt.
REFERENCES
Becker, P., 1983. Phosphates and Phosphoric Acid: Raw
Materials, Technology, and Economics of the Wet Process.
Marcel Dekker, New York.
Claude, L.W., Henry, M. J.R., 1953. Method for deter-
mination of small amounts of rare earths and thorium
in phosphate rocks. Analytical Chemistry, Vol. 25(3),
pp. 432–435.
Giesekke, E.W., 1985. Florida phosphate rock. In: Weiss,
N.L. (Ed.), SME Mineral Processing Handbook. SME,
pp. 1–18. (Section 21).
Grosz, A. E., Meier, A. L., Clardy, B. F., Howard, J. M.,
1995. Rare earth elements in the Cason Shale of Northern
Arkansas: a geochemical reconnaissance, Arkansas
Geological Commission.
Hassan, E and Bogan, M., 1994. Characterization of
Future Florida Phosphate Resource. FIPR Publication
02-082-105.
Kanazawa, Y., Kamitani, M., 2006. Rare earth miner-
als and resources in the world. Journal of Alloys and
Compounds, Vol. 408, pp. 1339–1343.
Jasinski S M, 2017. Mineral Commodity Summaries 2017,
Phosphate Rock, US Geological Survey, Department
of the Interior, pp. 124–125.
88.5% -90.5% when the stoichiometric ratio of H2SO4
to CaO increased from 1.85 to 3.26. After that it rose as
the ratio increases and reached 95.33% at the applied high-
est ratio of 4.60. The sulfuric acid demand in the leaching
was much higher than the theoretical value to decompose
phosphates, which was mainly due to the high content of
impurities in the flotation concentrate.
It should be noted that the downstream REE extrac-
tion from the leachate and production of mixed REE oxide
are presented in separate papers to be published in the near
future.
CONCLUSIONS
The research results in this paper indicate that the REEs
and phosphates in the amine flotation tails could be con-
centrated and leached through the process of separation
and leaching. Gravitation separation by shaking table con-
centrated the REEs and P2O5 in the tails from about 202
ppm and 3% to 657 ppm and 8%, respectively, with a con-
centrate yield of 12.51%, achieving REEs recovery of about
41%, and P2O5 recovery of 33%. After ground, the shak-
ing table concentrate could be further upgraded through
flotation to produce a concentrate containing 1151 ppm of
REEs and 14.90% of P2O5 at REE recovery of 85.91% and
P2O5 recovery of 89.81%. Leaching tests demonstrated the
REEs and phosphorus in the flotation concentrate could be
recovered through a process of concentrated sulfuric acid
pyrolysis – water leaching, resulting in recoveries of about
85% for REE and 93% for P2O5.
However, there are still some challenges to the process-
ing approach employed in this research. One is that the
REE minerals and apatite are finely disseminated in the
amine flotation tails, with some interlocked with gangue
minerals, which led to the low recoveries of 40.73% for
REEs and 33.15% for P2O5 in shaking table separation,
and low grades of the valuables in flotation concentrate.
Both the REEs content of 1150.82 ppm and P2O5 con-
tent of 14.90% in the flotation concentrate can not meet
the requirements of current industry practice. Since the
amine flotation tails contains more than 90% (by weight)
of gangue minerals (calculated based on the P2O5 content
of 3.02%), it is not economically feasible to grind the entire
tails before removal of the majority of gangue mineral due
to high energy consumption.
The other issue is high sulfuric acid addition required
in the roasting-leaching process. All the acid additions in
the range we tested (1.85 to 4.60 of stoichiometric ratio
of H2SO4 to CaO) were much higher than the theoreti-
cal demand for decomposing phosphates, but only when
the stoichiometric ratio was above 3.26, did the leaching
efficiencies of REEs and P2O5 reached their high levels.
This phenomenon can be attributed to the high contents
of impurities such as calcite, dolomite and some Fe-bearing
minerals which consumed some acid. On the other hand,
the REEs minerals needed high concentration of sulfuric
acid for its decomposition during roasting.
ACKNOWLEDGMENTS
This research is part of a major project of the Critical
Materials Innovation (CMI) Hub (formerly Critical
Materials Institute), under subcontract number SC-14-392
funded by the US Department of Energy, Office of Energy
Efficiency and Renewable Energy, Advanced Materials &
Manufacturing Technologies Office. The guidance and
leadership provided by Bruce Moyer, CMI focus area lead,
and David DePaoli, CMI project lead, are highly appreci-
ated. Substantial matching fund is provided by the Florida
Industrial and Phosphate Research Institute, Florida
Polytechnic University. The Mosaic Co. is particularly
acknowledged for their technical input, large in-kind sup-
port, and sample collection efforts. We want to express our
gratitude to the following Mosaic employees and former
employees for their help: Nicole Christiansen, Paul Kucera,
Marcos Ortiz, Chris Dennis, Glen Oswald, Chaucer
Hwang, Cameron Weed, and Gary Whitt.
REFERENCES
Becker, P., 1983. Phosphates and Phosphoric Acid: Raw
Materials, Technology, and Economics of the Wet Process.
Marcel Dekker, New York.
Claude, L.W., Henry, M. J.R., 1953. Method for deter-
mination of small amounts of rare earths and thorium
in phosphate rocks. Analytical Chemistry, Vol. 25(3),
pp. 432–435.
Giesekke, E.W., 1985. Florida phosphate rock. In: Weiss,
N.L. (Ed.), SME Mineral Processing Handbook. SME,
pp. 1–18. (Section 21).
Grosz, A. E., Meier, A. L., Clardy, B. F., Howard, J. M.,
1995. Rare earth elements in the Cason Shale of Northern
Arkansas: a geochemical reconnaissance, Arkansas
Geological Commission.
Hassan, E and Bogan, M., 1994. Characterization of
Future Florida Phosphate Resource. FIPR Publication
02-082-105.
Kanazawa, Y., Kamitani, M., 2006. Rare earth miner-
als and resources in the world. Journal of Alloys and
Compounds, Vol. 408, pp. 1339–1343.
Jasinski S M, 2017. Mineral Commodity Summaries 2017,
Phosphate Rock, US Geological Survey, Department
of the Interior, pp. 124–125.