Rare Earth Elements: A Review of Production, Processing ...

6. Potential Human Health and Ecological Risks of Production, Processing, and Recycling of
REEs .................................................................................................................................................... 6-1
6.1 Generalized Conceptual Site Model for Environmental Risk from a REE Mine and
Mineral Processing Plant .......................................................................................................... 6-2
6.1.1 Contaminant Release and Transport .......................................................................... 6-6
6.1.2 EPA Studies of Hardrock Mine Environmental Risks ............................................ 6-10
6.2 Pathway and Exposure Scenarios for REE-Recycling ........................................................... 6-14
6.3 Documented Human Health and Ecological Effects from Exposure to REE ......................... 6-15
7. Summary, Key Findings from Literature Review, and Potential Next Steps ...................................... 7-1
7.1 Summary ................................................................................................................................... 7-1
7.2 Key Findings ............................................................................................................................ 7-2
7.3 Suggested Next Steps ............................................................................................................... 7-3
8. References ........................................................................................................................................... 8-1
Appendices
A Selected Chemical Properties of REEs
B Locations of REE-Producing Mines and REE-Containing Mineral Deposits in the U.S.
C Process Flow Diagrams for Extraction and Processing Operations
List of Figures
2-1. Periodic table of the elements showing the division between LREES and HREES
(Schuler et al., 2011). .................................................................................................................... 2-3
2-2. Map showing occurrences of REEs, by rock type (adapted from multiple sources, see
Appendix B). .................................................................................................................................. 2-5
2-3. In-use stocks of selected REEs by specific application or industry (in gigagrams) (Du and
Graedel, 2011). ............................................................................................................................. 2-7
2-4. Global production of rare earth oxides (Du and Graedel, 2011). .................................................. 2-8
3-1. Molycorp Minerals rare earth mine, Mountain Pass, California. .................................................. 3-3
3-2. Typical time frame for a mine project. ....................................................................................... 3-12
3-3. Aerial image of Pea Ridge magnetite mine, Missouri. ............................................................... 3-16
3-4. Conventional hardrock deposit mining process and wastes emissions. ...................................... 3-22
3-5. Conventional placer deposit processing and wastes emissions. .................................................. 3-22
4-1. Conventional placer deposit resource processing and potential wastes emissions. ...................... 4-2
4-2. Conventional hardrock resource processing and potential wastes emissions. .............................. 4-3
4-3. Anticipated Molycorp Mountain Pass mine water reclamation process and potential
waste emissions. .......................................................................................................................... 4-10
5-1. Representative rare earth oxide prices from 2007–2010 (The 2007–2010 figures are
fourth-quarter [Q4] average prices. The 2011 numbers represent spot prices on
February 25). ................................................................................................................................. 5-2
5-2. REE recycling steps and waste emissions..................................................................................... 5-4
5-3. Left: Dismantling table with pneumatic tools used for manual dismantling of hard disks
Right: Components resulting from the process and including REE-containing magnets
(upper right corner) (Schluep et al., 2009). ................................................................................... 5-6
6-1. Generic above-ground hardrock mine conceptual site model and exposure pathways (U.S.
EPA, 2009a). ................................................................................................................................. 6-5
6-2. Sources of potential human exposures resulting from mining operations (U.S. EPA
ORCR, 2010). ............................................................................................................................. 6-11
6-3. Sources of potential exposures of current and future ecological receptors resulting from
mining operations (U.S. EPA OCRC, 2010). ............................................................................. 6-12
6-4. “Low–tech” gold recycling in Bangalore/India (Schluep et al., 2009). ...................................... 6-14
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