Non-thermal production of tungsten from scheelite

Abstract

A mixture of scheelite and magnesium was mechanically milled for 100 h in an inert atmosphere. The resultant powder was examined using thermal analysis, isothermal annealing, and X-ray diffraction to determine the effect of milling on the reduction of scheelite. Differential thermal analysis showed that the magnesium was completely consumed during the milling process. It was found that elemental tungsten was formed during the milling stage and the unwanted phases, MgO and CaO, were readily removed by leaching in acid, leaving a fine powder which was ∼99%W. The major impurities were iron and chromium which were present as a result of abrasion of the mill and balls.