Extraction of Tungsten from Tungsten Fine Mud by Caustic Soda Autoclaving

Tungsten fine mud is a type of tailings containing minerals such as quartz and potassium feldspar as well as a small amount of tungsten. In this article, tungsten fine mud was decomposed by caustic soda autoclaving. The results showed that at a temperature of 160 °C, caustic soda concentration of 100 g/L, treatment time of 2 h, liquid/solid ratio of 2.5:1 mL/g, and rotation rate of 400 rpm, the residue contained 0.28% WO₃, and the leaching efficiency of WO₃ was 94.97%. The optimal caustic leaching residue was subjected to SEM–EDS analysis, and the tungsten is mainly present as CaWO₄ and FeWO₄, is distributed in silicate particles, and is difficult to leach. Then, the effect of the number of cycles of autoclaving on tungsten leaching from tungsten fine mud was studied. The caustic concentration of the caustic leaching solution was always maintained at 100 g/L. After 12 cycles, the WO₃ concentration in the caustic leaching solution increased from 15.88 to 120.15 g/L. The leaching efficiency of WO₃ remained at 91% during the cycling process, and the caustic mass consumption in a single cycle was approximately 22%.