Distribution and Speciation of Rare Earth Elements in Clay Deposits via Synchrotron µXRF and µXANES

Conference · Thu Aug 16 04:00:00 EDT 2018

OSTI ID:1814902

Stuckman, Mengling; Lopano, Christina ^[1]; Montross, Scott ^[2]; Verba, Circe ^[1]

---

1. NETL
2. AECOM

Underclay, the layer of stratum beneath a coal bed, are being explored as a potential mining source of rare earth elements (REE). This study utilized micro-X-Ray fluorescence (µXRF) and micro X-Ray near edge structure (µXANES) to characterize the Ce speciation and REE distribution from four underclay samples (total REE content: 250-450 ppm) from clay deposits associated with Central Appalachian coal seams. The following REE binding environments have been identified in our study: (1) micro-scale trace minerals (10-40 µm) with various co-localization pattern with Ca, P, and Al; (2) large-scale light REE (e.g., Ce, La, Sm, and Nd) zones (>200µm) colocalizing with Sr and Ba, whose Ce µXANES displayed a Ce(III) species distinctively different (with shorter post-edge oscillation) from micro-scale Ce hotspots and previously collected Ce(III) references for fly ash study [1], and (3) The heavy REEs (e.g, Gd, Yb) often colocalize with Fe and sometimes with S, P and Y, indicating presence of xenotime or REE-bearing pyrite. Our results indicate the REE mineralization may occur in the presence of Ba, Sr and LREE-rich hydrothermal fluids, highly charged with volatile constituents (e.g., carbon dioxide, fluorine, and phosphorus). The characterization of REE-bearing phases in underclay deposits provides key mineralogical data to develop targeted and more efficient methods for the recovery of REE from domestic geological deposits.

• Research Organization: National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
• Sponsoring Organization: USDOE Office of Fossil Energy (FE)
• OSTI ID: 1814902
• Report Number(s): NA
• Country of Publication: United States
• Language: English