REE IN AMD-IMPACTED SEDIMENT IN PENNSYLVANIA’S ANTHRACITE REGION

Rare-earth elements (REEs), which include Sc, Y, and the lanthanide series elements, are essential raw materials for modern technologies such as cell phones, batteries, computers, and renewable energy systems. All but one REE have been identified by the USGS as critical to the U.S. economy and national security. Concerns about export bans, depletion of U.S. supplies, and high tariffs on imported REEs have driven the search for additional domestic sources.

Previous studies indicate that REE concentrations are elevated in some coal deposits, coal-adjacent rock strata, and in acid mine drainage (AMD) precipitate associated with coal mines and coal waste. AMD treatment sites and AMD-impacted streams in Pennsylvania’s anthracite coal region have been studied for nearly 20 years by faculty and students at Commonwealth University – Bloomsburg (formerly Bloomsburg University). This study began by testing the utility of using pXRF on filtrate on archived glass fiber filters as a screening tool to identify AMD-impacted areas with elevated REE concentrations. No REEs were detected on archived filters from studies of AMD treatment sites, AMD-impacted streams, or high-filtrate groundwater samples. Our next step was to analyze yellow boy precipitate from discharges from several different mine pools across the middle anthracite fields. A Niton XL3t GOLDD pXRF was used to determine concentrations of Y, Sc, La, Ce, Pr, and Nd in dried, crushed samples of AMD precipitate. Where detected, concentrations of REEs varied as follows: Y (3-13 ppm), La (107-366 ppm), Ce (117-433 ppm), Pr (157-631), and Nd (248- 927 ppm). No Sc was detected. Total (detected) REE concentrations range from 122 to 2339 ppm, or 0.012% to 0.2% (dry weight).

Mine drainage chemistry varied among these sites. REEs were detected in those sites with higher dissolved iron and manganese, including two AMD treatment sites (Scarlift 15 and Pine Forest), two mine drainage seeps (Ashland geyser and Kulpmont), and two AMD-impacted streams (Big Mine Run and N Branch Shamokin Creek). No REEs were detected in precipitate samples collected from the Oneida 3 AMD treatment site, whose discharge is high in dissolved aluminum but low in dissolved iron and manganese.