Recovery of Tungsten from a Sulfuric-Phosphoric Acid Leaching Solution by Solvent Extraction with 2-Octanol

A new generation tungsten hydrometallurgical technology was successfully applied in China and, in 2018, won China's national technology invention award. This article focuses on the research concerning this new technology; specifically, this article focuses on a method for reducing ammonia consumption. First, the effect of the concentrations of H2SO4 and H3PO4 on scheelite digestion and tungsten extraction were studied. Under the optimum conditions, over 99.9% of the tungsten was leached out, and over 93.2% of the tungsten in the leached solution was extracted by 30% 2-octanol. Furthermore, in this process, water was explored as a stripping agent. Under the optimum conditions, the water strip liquor contained 352 g/L WO3 and 3.68 g/L P. Finally, the phosphorus impurity in the strip liquor was thoroughly removed by an ammonium-magnesium salt precipitation method. The dose of the ammonia was 1.3-1.5 times the theoretical amount, which is half the dose of the traditional method.