Speaker
Description
Since the acceptance of the 5MV AMS ASTER (CEREGE, Aix en Provence), the national laboratory LN2C is routinely measuring 10Be and 26Al for the scientific community. Previously based on a solvent extraction using EDTA and CCl4, we moved in 2008 due to the end of CCl4 production and to change for a safer chemistry, to a separation by ion exchange chromatography using anionic and cationic resins. But prior to this step, the sample purification quality is for one of the most important steps. The purification is a time-consuming and costly process. It is important that each step is carried out with the utmost care, using the most appropriate purification techniques that must be the most environmentally friendly.
In this study, we will present how to get a pure quartz and we will focus on two persistent minerals: feldspars and muscovite. These latter minerals may persist after acid etching and yield to a significant reduction in the target emissivity in the AMS source. To define the limit beyond which the presence of these minerals mixed with quartz has an impact on sample preparation and AMS measurements, we prepared mixtures of geological samples by adding different proportion of feldspars, or/and micas with pure quartz. ICP-OES analyses were carried out to determine variations in aluminum concentration related to the proportion of feldspars or micas as well as a multi-element analyses to track B, Be, Al, Ti, Ca, Na, K, Mg, Fe, along the different steps of Be and Al extraction processes. Targets for AMS measurements were then prepared to define what are the critical values for which the quality of AMS measurement is impacted.
To eliminate feldspars, we tested an effective, fast, and environmentally friendly method based on magnetite addition combined with a magnetic separation (Lacumin and Quercioli, 1993). For micas, we tested other techniques: flotation, heavy liquor, sieving and high-current magnetic separation.
References
[1] Silke Merchel, Andreas Gärtner, Sabrina Beutner, Bodo Bookhagenc , Amelié Chabilan, Attempts to understand potential deficiencies in chemical procedures for AMS: Cleaning and dissolving quartz for 10Be and 26Al analysis. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Volume 455 (2019), p. 293-299
[2] Lacumin and Quercioli, A new technique for quantitative separation of quartz from feldspars. European Journal of Mineralogy Volume 5 Number 4 (1993), p. 677 - 678
| Student Submission | No |
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