Among more than thirty known tungsten containing minerals, only scheelite (CaWO₄) and wolframite ((Fe, Mn)WO₄) are industrially important [1]. Scheelite is the most abundant mineral of tungsten, but wolframite is used more than scheelite due to easier dissolution in alkaline solutions used in present processing methods [2]. An alternative method based on electrochemical reduction of CaWO₄by direct current applications in molten salt solutions was recently reported [3-5]. In this study, pulse voltage and constant voltage reduction mechanisms were compared and an optimization of reduction kinetics was achieved. Studies have shown that faster reduction rates could be achieved during pulse voltage applications compared to constant voltage applications, when average voltage value of pulse voltage application was the same as its constant counterpart. Furthermore, analysis of charge, energy and theoretical reduction graphs showed that reduction of calcium tungstate occurs at higher potential differences than 2.2 V, between calcium tungstate and graphite.

References:

[1] Brown, T. and Pitfield, P. (2013) ‘Tungsten’, in Gunn/Critical Metals Handbook. Wiley-Blackwell, pp. 385–413.

[2] Tang, D., Xiao, W., Yin, H., Tian, L., Wang, D. and and, L. T. (2012) ‘Dingding Tang’, Journal of The Electrochemical Society, 159(6), p. E139. doi: 10.1149/2.113206jes.

[3] Karakaya, I. and Erdogan, M. (2009)‘Production of Tungsten and Tungsten Alloys from Tungsten Bearing Compounds by Electrochemical Methods’, WIPO PCT application WO 2009/054819A1.

[4] Karakaya, I. and Erdogan, M. (2013) ‘Production of tungsten and tungsten alloys from tungsten bearing compounds by electrochemical methods’, CA 2703400Canadian Intellectual Property Office.

[5] Erdogan, M. and Karakaya, I. (2010) ‘Electrochemical Reduction of Tungsten Compounds to Produce Tungsten Powder’, Metallurgical and Materials Transactions B, 41(4), pp. 798–804. doi: 10.1007/s11663-010-9374-4.