Adaptation of a Rare Earth Element Pre-concentration Method for Water Enriched in Al, Ca, Fe, and Mg

• Published in: Mine water and the environment Vol. 36; no. 3; pp. 363 - 370
• Main Authors: Grawunder, Anja, Gärtner, Sven, Merten, Dirk
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-09-2017; Springer Nature B.V
• Subjects: Adaptation; Aluminum; Chemical elements; Chlorides; Detection; Detection limits; Dilution; Earth; Earth and Environmental Science; Earth Sciences; Ecotoxicology; Geology; Hydrogeology; Industrial Pollution Prevention; Interactions; Ionic strength; Iron; Magnesium; Mineral Resources; Minerals; Neodymium; pH effects; Rare earth elements; Strength; Sulfates; Technical Article; Total dissolved solids; Water; Water Quality/Water Pollution; Water resources; Competing elements; REE; Mine drainage; ICP-MS
• ISSN: 1025-9112; 1616-1068
• DOI: 10.1007/s10230-016-0418-0

The use of rare earth elements (REE) as process indicators in water-rock interactions can be hampered by the fact that samples with high concentrations of total dissolved solids require dilution before ICP-MS analysis, which can lower REE concentrations close to or below detection limits. A pre-concentration method originally developed for chloride-dominated water with very low REE concentrations was tested for and adapted to sulfate-rich water from a mining-affected area with a pH of 6 and high concentrations of Ca, Fe, Mg, and sometimes Al. The adapted approach proved easy to implement in the field and produced very good recoveries and reliable REE patterns. Two factors, sample volume and ionic strength, were tested. Pre-concentration with high sample volumes (1000 mL) resulted in poor recoveries (1.8 ± 0.3 % for La up to 17.8 ± 0.6 % for Yb). When the sample volume was reduced to 25 mL, much better recoveries were achieved. Reducing the ionic strength by diluting the sample 1:100 or 1:1000 resulted in comparable recoveries than the approach with reduced sample volume, indicating that sample volume was more important than ionic strength. Among the tested competing elements, high concentrations of Ca, Fe, and Mg resulted in loss of light REE (La-Nd), while Al was found to reduce the recovery of all REE. Also for water with high concentrations of Ca and Fe and very low REE concentrations (ppt-range), especially La results should be considered with care after pre-concentration, and be neglected in REE patterns if necessary.