XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 203
process offers an effective and economically viable solution
to remediate legacy mine sites, addressing the prohibitive
costs typically associated with remote location remediation.
Currently, 85% of homes on the Navajo Nation are
contaminated with uranium, causing significantly higher
rates of cancer and kidney failure (Calvert, 2021). The only
commercially available solution to reduce the radiation lev-
els is to haul all material from the contaminated sites to a
disposal facility or bury and place a cap on all the material
onsite. However, HPSA has shown great potential in reme-
diation for AUMs, allowing for on-site decontamination
of soils and waste piles. In 2022, the U.S. Environmental
Protection Agency (EPA), in coordination with the Navajo
Nation and Tetra Tech, funded a HPSA uranium treatabil-
ity study for three different remediation sites. The results of
the study validated HPSA as a viable option to treat AUMs
(Tetra Tech, Disa Technologies, 2023). Furthermore, HPSA
was further validated for uranium and vanadium processing
by Idaho National Laboratory in a study treating uranium
waste rock (Williams, 2022).
Uranium Remediation—Case 1
In a 2022 study, a HPSA Batch Unit was used to process
mixtures of waste mixed in (1) ore, (2) coarse to fine grain
sand, and (3) sandy clay soil. Samples were taken from
three different sites with varying concentrations of con-
tamination deemed high, medium, and low and cleaned
with a HPSA system. For each case, the host mineral quartz
(Mohs hardness of 7) was used to liberate natural uranium-
bearing minerals, such as carnotite (Mohs hardness of 2).
The objective of HPSA processing was to separate the
radionuclides and metals into a small volume of the fine
size fractions 53 µm (–270 US mesh), so the bulk volume
of material remaining in the coarse particle size fractions
were “clean enough” to remain onsite. Characterization of
the minerals pre and post HPSA for one of the feedstocks
are shown in Figure 7. The automated scanning electron
microscope mineral and chemical identification technique
used for Mineral Liberation Analysis (MLA) indicated
fracturing detachment of carnotite from +149 µm (+100
US mesh) quartz particles during HPSA, which were cap-
tured in the –53 µm (–270 US mesh) samples. The effect of
HPSA processing is clearly shown in Figure 8 where 93% of
the total uranium concentrated into 15% of the total mass,
specifically in the –53 µm (–270 US mesh) size fraction. The
remaining 85% of the mass had low enough uranium lev-
els to remain safely onsite. Furthermore, HPSA processing
reduced leachable metals and radionuclides in the treated
coarse fraction +53 µm (+270 US mesh) by approximately
96%, negating the need for a soil cover to protect surface
water and groundwater (Tetra Tech, Disa Technologies,
2023) (United States Environmental Protection Agency,
2023). The studies show the promise in HPSA as a meth-
odology to prevent harm to indigenous communities while
providing a 50–80% more economical disposal solution.
Figure 7. Automated Mineralogy particle maps for pre and feed and post HPSA samples for uranium remediation study
process offers an effective and economically viable solution
to remediate legacy mine sites, addressing the prohibitive
costs typically associated with remote location remediation.
Currently, 85% of homes on the Navajo Nation are
contaminated with uranium, causing significantly higher
rates of cancer and kidney failure (Calvert, 2021). The only
commercially available solution to reduce the radiation lev-
els is to haul all material from the contaminated sites to a
disposal facility or bury and place a cap on all the material
onsite. However, HPSA has shown great potential in reme-
diation for AUMs, allowing for on-site decontamination
of soils and waste piles. In 2022, the U.S. Environmental
Protection Agency (EPA), in coordination with the Navajo
Nation and Tetra Tech, funded a HPSA uranium treatabil-
ity study for three different remediation sites. The results of
the study validated HPSA as a viable option to treat AUMs
(Tetra Tech, Disa Technologies, 2023). Furthermore, HPSA
was further validated for uranium and vanadium processing
by Idaho National Laboratory in a study treating uranium
waste rock (Williams, 2022).
Uranium Remediation—Case 1
In a 2022 study, a HPSA Batch Unit was used to process
mixtures of waste mixed in (1) ore, (2) coarse to fine grain
sand, and (3) sandy clay soil. Samples were taken from
three different sites with varying concentrations of con-
tamination deemed high, medium, and low and cleaned
with a HPSA system. For each case, the host mineral quartz
(Mohs hardness of 7) was used to liberate natural uranium-
bearing minerals, such as carnotite (Mohs hardness of 2).
The objective of HPSA processing was to separate the
radionuclides and metals into a small volume of the fine
size fractions 53 µm (–270 US mesh), so the bulk volume
of material remaining in the coarse particle size fractions
were “clean enough” to remain onsite. Characterization of
the minerals pre and post HPSA for one of the feedstocks
are shown in Figure 7. The automated scanning electron
microscope mineral and chemical identification technique
used for Mineral Liberation Analysis (MLA) indicated
fracturing detachment of carnotite from +149 µm (+100
US mesh) quartz particles during HPSA, which were cap-
tured in the –53 µm (–270 US mesh) samples. The effect of
HPSA processing is clearly shown in Figure 8 where 93% of
the total uranium concentrated into 15% of the total mass,
specifically in the –53 µm (–270 US mesh) size fraction. The
remaining 85% of the mass had low enough uranium lev-
els to remain safely onsite. Furthermore, HPSA processing
reduced leachable metals and radionuclides in the treated
coarse fraction +53 µm (+270 US mesh) by approximately
96%, negating the need for a soil cover to protect surface
water and groundwater (Tetra Tech, Disa Technologies,
2023) (United States Environmental Protection Agency,
2023). The studies show the promise in HPSA as a meth-
odology to prevent harm to indigenous communities while
providing a 50–80% more economical disposal solution.
Figure 7. Automated Mineralogy particle maps for pre and feed and post HPSA samples for uranium remediation study
