2014-Sustainable Industrial Processing Summit
SIPS 2014 Volume 6: Rare Earths & Ionic Liquids
| Editors: | Kongoli F |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2014 |
| Pages: | 432 pages |
| ISBN: | 978-1-987820-08-9 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Achieving inert graphite anode and high efficiency for electrolysis of solid metal oxides and metal sulfides in molten chlorides
Xianbo Jin1; George Chen2;1WUHAN UNIVERSITY, Wuhan, China; 2UNIVERSITY OF NOTTINGHAM, Nottingham, United Kingdom (Great Britain);
Type of Paper: Plenary
Id Paper: 405
Topic: 11
Abstract:
Refractory metals play crucial roles in our materials based modern civilisation. Currently, industrial production of refractory metals, such as Ti, Si, Ta and Zr, is commonly achieved via the pyrometallurgical process that is often carbon and/or energy intensive. Alternatively, refractory metal extraction might be achieved by electrolysis of their solid oxide minerals in molten CaCl2 with high diffusivity for O2- ions which can then transport to, and discharge at the anode. This mechanism would be ideal if coupled with an inert anode to produce the O2 gas. However, similar to electrolysis of Al2O3 dissolved in cryolite based molten fluorides, the carbon anode will still be the best choice to a commercial process of electro-reduction of solid metal oxides, causing CO2 emission, anode replacement, and other problems, such as shuttle reactions due to the high solubility of CO2 in the CaO containing electrolytes. In this presentation, two new strategies will be explained and discussed on changing the anodic reaction on an inert carbon anode in molten chlorides with negligible or low O2- solubility. One is the electrolysis of solid metal sulfides to metal and elemental S in NaCl-KCl melts with graphite serving as an ideal inert anode, promising clean processes for the metallurgies of sulfide minerals such as molybdenite. The other one is the electrolysis of metal oxides in MgCl2 based melts, showing a completely new mechanism in comparison with that in molten CaCl2. Since the O2- ions cannot transport to anode, the anodic reaction will be the discharge of Cl- ions to Cl2 gas with graphite again serving as an inert anode. This strategy has led to significantly higher current efficiency, and lower energy consumption, and the electrolysis of TiO2, ZrO2, Ta2O5 and SiO2 will be described in detail based on both thermodynamic calculation and experimental results.