Evaluation of overpotentials on graphite and liquid Bi–Mg electrodes by current interruption
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Our group proposes a new titanium smelting process via Bi–Ti alloy. This process is comprised of reduction of TiCl4 by Bi–Mg liquid alloy, separation of Ti from Bi by distillation, and Mg electrolysis. In this study, the Mg electrolysis with Bi–Mg liquid alloy cathode was investigated. We firstly measured the IR-corrected polarization curves on graphite and Bi–Mg liquid alloys by the current interruption method. The results indicated that the Bi–Mg alloy cathode can reduce the electricity consumption of the Mg electrolysis. In addition, from the relaxation curves on graphite and Bi–Mg alloys, the concentration overpotential on the Bi–Mg alloy is mainly due to mass transfer of Mg from the electrode/molten salt interface to the liquid alloy bulk. At current densities higher than 300 mA cm−2, Mg-rich solid phases such as Bi2Mg3 and/or pure solid Mg are assumed to be deposited on the Bi–Mg liquid alloy cathode. Finally, we estimated the electricity consumption of the Mg electrolysis in the new smelting process based on the measured overpotentials, assuming that Bi–Mg liquid alloy cathode is stirred sufficiently and a low current density, 275 mA cm−2, is applied. Under these conditions, the total electricity consumption of the Mg electrolysis in the new process will be lower than that in the Kroll process when the anode–cathode distance is smaller than 8 cm.
KeywordsMolten salt Overpotentials Magnesium electrolysis Bi–Mg alloy
This work was supported by Advanced Low Carbon Technology Research and Development Program, Japan Science and Technology Agency, JST ALCA (Grant No. JPMJAL1006). Bi metal was supplied by Kamioka Mining & Smelting Co., Ltd.
- 4.Crowley G (2003) How to extract low-cost titanium. Adv Mater Process 161:25–27Google Scholar
- 13.Tomonari T (2001) Chitan Kogyo to Sono Tenbo. The Japan Titanium Society, JapanGoogle Scholar
- 27.Bard AJ (1976) Encyclopedia of electrochemistry of the elements, vol 10. Marcel Dekker Inc, New YorkGoogle Scholar
- 29.The Electrochemical Society of Japan (2000) Denki Kagaku Binran, 5th edn. Maruzen Publishing Co., Ltd, TokyoGoogle Scholar
- 37.Chase NW Jr (1998) NIST-JANAF, thermochemical tables, 4th edn. ACS and AIP, Washington, D. C.Google Scholar