ORAL

SESSION: MoltenTueAM-R3	Gaune-Escard International Symposium on Sustainable Molten Salt and Ionic Liquid Processing (5th Intl. Symp. on Sustainable Molten Salt and Ionic Liquid Processing)
Tue Oct, 24 2017	Room: Peninsula 1
Session Chairs: Rasmus Fehrmann; Georges Kipouros; Session Monitor: TBA

11:30: [MoltenTueAM02]
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;
Paper Id: 187 [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.