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

Abstract

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.