2016-Sustainable Industrial Processing Summit
SIPS 2016 Volume 3: Oye Intl. Symp. / Ionic Liquid and Aluminum
| Editors: | Kongoli F, Feng N, Polyakov P, Gaune-Escard M |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2016 |
| Pages: | 180 pages |
| ISBN: | 978-1-987820-40-9 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Structural characterization of NaF-AlF3-CaF2 melts in refined aluminum electrolysis by high temperature Raman spectroscopy
Xianwei Hu1; Jingjing Liu1; Gaowei Li1; Bingliang Gao2; Zhongning Shi1; Jiangyu Yu1; Zhaowen Wang1;1NORTHEASTERN UNIVERSITY, Shenyang, China; 2, Shenyang, China;
Type of Paper: Regular
Id Paper: 131
Topic: 37
Abstract:
Three-layer liquid electrolytic purifying is the main method for producing refined aluminum and the NaF-AlF3-CaF2-BaF2 system is widely used as the electrolyte in that process. In this paper, Raman spectra of NaF-AlF3 with the composition of practical aluminum refining electrolyte are recorded and the melts structure was investigated, firstly, with the help of the quantum chemical calculation. On that basis, the effect of CaF2 addition to the ionic structure of NaF-AlF3 was then studied. The results have indicated that AlF4- tetrahedron and entities containing two or more AlF4- tetrahedron connected by ¡°bridge fluoride¡± were in NaF-AlF3 binary melts. CaF2 was added as a fluoride donor, when the ratio between NaF and AlF3(CR) and the content of CaF2/BaF2 are relatively low, the only kind of Al-F complex in the melts is AlF4- tetrahedron and the net or chain structure containing two or more AlF4- tetrahedrons connected by ¡°bridge fluoride¡±. With the increasing CR and content of CaF2, AlF52- appears in the melts and when continuing to increase CR and content of CaF2, AlF63- will appear. The temperature has little effect on the relative content of the complexes. The relationship between molar percent of the three complexes and CR has been obtained. At last, a dissolved model of CaF2 in NaF-AlF3 was discussed.