Yankuang ceshi (Jan 2020)
Development of Separating and Purifying Methods for Lithium Isotope Analysis of Bauxite
Abstract
BACKGROUND Bauxite is a product from extreme weathering, an important carrier of lithium. Due to its huge resources, the study on the mechanism and distribution of lithium in bauxite will be beneficial to the prospecting and prediction of bauxite deposits. Efficient and accurate analysis of lithium isotopes is the basis for deep understanding of the lithium enrichment mechanism and distribution driplines in the ores. The bauxite samples are more chemically stable and the sample dissolution process is more complicated. The content of matrix elements such as Al, Na, Ca and K is much higher than that of Li, which makes it difficult to purify Li. OBJECTIVES To establish a method for separating and purifying lithium in bauxite for Li isotope analysis. METHODS On the basis of previous studies, the separation, purification, and measurement scheme of Li in bauxite were investigated by leaching experiment. RESULTS In this scheme, polytetrafluoroethylene exchange column with an inner diameter of 5mm and a column length of 190mm, and AG50W-X12 cation exchange resin were used. 34mL of 0.5mol/L nitric acid was used as the eluent and the final solution was 12mL, resulting in complete purification and recovery of Li in bauxite. At the same time, the method was used to purify the Li in international standard samples, L-SVEC, RGM-2 and GSP-2, and the values of δ7Li were measured by MC-ICP-MS, which were -0.26‰±0.09‰ (2SD, n=3), 3.19‰±0.37‰ (2SD, n=3), -0.78‰±0.22‰ (2SD, n=3). The analytical results were consistent with the previous results obtained by other methods, verifying the reliability of this method. The proposed method was used to purify bauxite standard sample, GBW07182, which yielded δ7Li of 10.16‰±0.21‰ (2SD, n=3). CONCLUSIONS The purification method reduces the amount of eluent used and improves experimental efficiency.
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