2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 3. Gaune-Escard Intl. Symp. / Molten Salt and Ionic Liquid
| Editors: | Kongoli F, Fehrmann R, Gadzuric S, Gong W, Seddon KR, Malyshev V, Iwata S |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2017 |
| Pages: | 151 pages |
| ISBN: | 978-1-987820-65-2 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Anhydrous Feed Preparation for Molten Salt Electrolysis of Lanthanum Chloride
William Judge1; Georges Kipouros2;1MATERIALS SCIENCE AND ENGINEERING, UNIVERSITY OF TORONTO, Toronto, Canada; 2MATERIALS ENGINEERING, DALHOUSIE UNIVERSITY, Halifax, Canada;
Type of Paper: Regular
Id Paper: 187
Topic: 13
Abstract:
Many of the rare earth metals or their alloys are produced by molten salt electrolysis of their respective chlorides in alkali chloride melts. Perhaps somewhat surprising, one of the most substantial challenges here is the preparation of high-quality anhydrous feed material. Rare earth chlorides are extremely hygroscopic and if dehydration is conducted without sufficient precautions, hydrolysis and formation of hydroxychloride and oxychloride is favoured. The presence of these compounds in the feed material lower the current efficiency, increase the bath viscosity, consume the otherwise inert graphite anodes, and sediment in bottom of the cell, contaminating the metal product. To prevent hydrolysis, a certain partial pressure of hydrogen chloride must be maintained during dehydration, yet without detailed thermodynamic data available for most of the intermediate compounds, its pursuit appears fruitless. The presentation is summarizing an estimation and prediction model for the vapour pressures of rare earth chloride hydrates to determine the thermodynamic conditions for dehydration to proceed without hydrolysis. Thermodynamic data for intermediate hydrates and hydrolytic compounds are deduced from literature data and trends proven in similar systems. Results are presented for the case of lanthanum.
Keywords:
Chloride; Electrolysis; Moltensalt; Neodymium; Thermodynamic;References:
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