Rare Earth Elements: A Review of Production, Processing ...
Rare Earth Elements: A Review of Production, Processing ...
Rare Earth Elements: A Review of Production, Processing ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
<strong>Rare</strong> <strong>Earth</strong> <strong>Elements</strong> <strong>Review</strong><br />
Section 4 – Resource <strong>Processing</strong><br />
4.1 Bevill Amendment<br />
The 1980 amendment to the Resource Conservation and Recovery Act (RCRA), known as the Bevill<br />
exclusion, was enacted to exclude specific solid wastes from the extraction, beneficiation, and processing<br />
<strong>of</strong> ores and minerals. The EPA established criteria for determining beneficiation and process waste for<br />
each mineral production sector and reported this information in the final rule (54 Fed. Reg. 36592, 36616<br />
codified at 261.4(b)(7)).<br />
The EPA determined the line between beneficiation and processing <strong>of</strong> rare earths for one particular rare<br />
earth operation is when the ore is digested with concentrated acids or caustics (U.S. EPA, 1991).<br />
However, several factors are involved in making Bevill determinations, and <strong>of</strong>ficial assistance should be<br />
sought from the RCRA authorized state or the EPA Regional <strong>of</strong>fice. The basic steps in making Bevill<br />
determinations are the following:<br />
1. Determine whether the material is considered a solid waste under RCRA.<br />
2. Determine whether the facility is using a primary ore or mineral to produce a final or intermediate<br />
product, and also whether less than 50 percent <strong>of</strong> the feedstock on an annual basis are from<br />
secondary sources.<br />
3. Establish whether the material and the operation that generates it are uniquely associated with<br />
mineral production.<br />
4. Determine where in the sequence <strong>of</strong> operations beneficiation ends and mineral processing begins.<br />
5. If the material is a mineral processing waste, determine whether it is one <strong>of</strong> the 20 special wastes<br />
from mineral processing.<br />
This process <strong>of</strong> determination will result in one <strong>of</strong> the three outcomes:<br />
• The material is not a solid waste and therefore not subject to RCRA;<br />
• The material is a solid waste, but is exempt from RCRA Subtitle C because <strong>of</strong> the Mining Waste<br />
Exclusion; or<br />
• The material is a solid waste that is not exempt from RCRA Subtitle C and is subject to regulation<br />
as a hazardous waste if it is listed or characteristic hazardous waste.<br />
The EPA <strong>of</strong>fers online compliance assistance on the Bevill Amendment at the following Internet address:<br />
http://www.epa.gov/oecaerth/assistance/sectors/minerals/processing/bevillquestions.html.<br />
4.2 Beneficiation Processes<br />
As previously described in Section 4.1, the beneficiation process does not alter the chemical composition<br />
<strong>of</strong> the ore; rather, these processes are intended to liberate the mineral ore from the host material. The<br />
crushing and grinding steps enable the exploitation <strong>of</strong> differences in physical properties such as<br />
gravimetric, magnetizability, and surface ionization potential to aid in separation (Aplan, 1988). The<br />
separation processes typically employed are (1) gravity separators, (2) electrical/magnetic separators, and<br />
(3) flotation separators.<br />
Gravity concentration methods separate minerals <strong>of</strong> different specific gravity by exploiting the variance in<br />
their gravity-driven movement through a viscous fluid. For successful separation using this technique,<br />
there must exist a marked density difference between the mineral and the gangue. Examples <strong>of</strong> gravity<br />
separators include (1) jigs; (2) pinched sluices and cones; (3) spirals; (4) shaking tables; (5) pneumatic<br />
tables; (6) duplex concentrators; (7) Mozley laboratory separator; and (8) centrifugal concentrators.<br />
4-4