Search

Your search keyword '"Liu Yongsheng"' showing total 28 results
Start Over Author "Liu Yongsheng" Journal chemical geology
28 results on '"Liu Yongsheng"'

28. Rapid bulk rock decomposition by ammonium fluoride (NH4F) in open vessels at an elevated digestion temperature.

Author

Hu, Zhaochu, Zhang, Wen, Liu, Yongsheng, Chen, Haihong, Gaschnig, Richard M., Zong, Keqing, Li, Ming, Gao, Shan, and Hu, Shenghong

Subjects
*CHEMICAL decomposition, *AMMONIUM fluoride, *HYDROFLUORIC acid, *ZIRCON, *BOILING-points, *GEOLOGY
Abstract

Complete dissolution is essential for achieving accurate analytical results for geological samples. Hydrofluoric acid is the most effective mineral acid for breaking up strong Si–O bonds to form SiF6 −2 ions in acidic solution. However, HF is rather inefficient in the open-vessel acid digestion of refractory minerals such as zircon due to its low boiling point (boiling point of 38.3% HF=112°C). In this study, a decomposition technique using the solid compound NH4F in an open vessel (Savillex Teflon vial) has been investigated for the multi-element analysis of various rock reference materials. The higher boiling point (260°C) of NH4F allows for an elevated digestion temperature in open vessels, which enables the decomposition of refractory phases. Using this method, Zr was completely recovered from the granodiorite GSP-2 reference material in 1–1.5h at 250°C, which is ~12 times faster than using conventional closed-vessel acid digestion at 190°C (high-pressure PTFE digestion bomb). There is a positive correlation between the test sample mass and the amount of NH4F required for complete recovery of Zr, Hf, Nb, Ta, and heavy rare earth elements in GSP-2, which is due to the resistance of zircon (which is a major reservoir for heavy rare earth elements) to decomposition at lower reagent to sample ratios. The recommended proportion of NH4F, relative to the amount of sample powder required for complete element recovery, is 6:1. Unlike in NH4F-assisted high-pressure acid digestion, our results clearly indicate that adding HNO3 severely inhibited the digestion capabilities of NH4F for refractory minerals such as zircon in open vessels. The most outstanding advantage of the new method is that the digestion can be performed in a conventional Savillex Teflon vial instead of a high-pressure PTFE digestion bomb. Moreover, NH4F−open-vessel acid digestion is not hampered by the formation of insoluble fluorides, which represents another important advantage of this new sample decomposition method. Similar to HF and HNO3, ultra-pure NH4F can be produced using a conventional PFA sub-boiling purification system, and it does not induce new interference species in ICP-MS analysis. Additionally, this reagent is removed by taking the sample to dryness, which is important to keep the total dissolved solid of the final solution presented to the instrument low. NH4F has many of the same safety handling requirements of HF, especially when being heated to dryness to remove the Si as SiF4, and excess reagent as HF, so safety issues are still a concern. The developed NH4F−open-vessel acid digestion method has been successfully applied to the digestion of a series of international geological reference materials. This simple, effective, and comparatively safe dissolution method shows great potential for the digestion of geological samples. [ABSTRACT FROM AUTHOR]

Published
2013
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results