Experimental study of fluorite solubility in acidic solutions as a method for boron fluoride complexes studying

Tarnopolskaia, M.E.; Bychkov, A. Yu.; Shvarov, Yu. V.; Popova, Yu. A.

doi:10.1134/s0016702917020069

Cited by 3 publications

(1 citation statement)

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“…Moreover, the presence of a substantial amount of excess F − in the digested solution can lead to the formation of calcium fluoride (CaF 2 ) precipitates, which co-precipitate some REEs [8]. The solubility of CaF 2 increases with decreasing pH due to an elevated concentration of H 3 BO 3 , attributed to the formation of the BF 3 OH − complex [9]. Furthermore, the HF digestion method has been observed to promote the formation of aluminum fluoride (AlF 3 ), which co-precipitates REEs, leading to lower recovery rates and reduced accuracy [10].…”

Section: Introductionmentioning

confidence: 99%

Tetrafluoroboric Acid Digestion for Accurate Determination of Rare Earth Elements in Coal and Fly Ash by ICP-MS Analysis

Li,

WoldeGabriel,

Marina

2024

Minerals

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Coal and coal-related fly ash often contain rare earth elements (REEs) that have the potential to be utilized as valuable mineral resources. Accurately determining the REE content in coal and fly ash is crucial for resource evaluation. The conventional approach involves using hydrofluoric acid (HF) to dissolve silicates and release REEs, which, however, prolongs the digestion process due to the additional step of complexing fluoride ions (F−) with boric acid (H3BO3). Determining the correct amount of H3BO3 for neutralization can be challenging, and in some instances, the binding of fluoride ions with certain lanthanides (Lns) hampers the accurate determination of all 14 naturally occurring rare earth elements in a single digestion batch by inductively coupled plasma mass spectrometry (ICP-MS). In this study, we present an alternative method that achieves the accurate determination of all 14 naturally occurring REEs using tetrafluoroboric acid (HBF4) followed by ICP-MS analysis. This approach eliminates the need for an F− complexing step. We tested this method on certified REE reference materials, including NIST 1632e (coal) and NIST 1633c (fly ash), as well as the REE geological reference material USGS AGV-1 (andesite). Our results demonstrated excellent recovery rates (relative standard deviation, RSD < ±10%), with a correlation coefficient (r2) exceeding 0.99. Using this method, we investigated the concentrations of all 14 REEs in coal and fly ash samples collected from various locations in the southwestern USA. This improved digestion technique streamlines the analysis process and enhances the accuracy of REE determination, facilitating a more comprehensive evaluation of REE-rich coal and fly ash deposits for resource exploration.

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Section: Introductionmentioning

confidence: 99%