Continuous solvent extraction operations for the separation of W and Mo in high concentrations from ammonium solutions with acidified N1923

Abstract

To separate tungsten and molybdenum from the ammonium solution containing 31.2 g/L WO3 and 32.5 g/L Mo, the continuous operations of solvent extraction were carried out using acidified primary amine extractant of N1923 in mixer-settlers. Thermodynamic analysis of the WMoH2O system showed that W(VI) could be selectively extracted over Mo (VI) by primary amine since WO42− was preferentially transformed to polymeric ions as the pH decrease. The results of 58 h continuous operations indicated that the solvent extraction process could be used effectively to separate W(VI) from ammonium molybdate solutions. The raffinate contained only 6.0–7.0 mg/L WO3 with a mass ratio of WO3/Mo less than 3.45–4.99×10−4, which can be used to produce ammonium molybdate with MSA-0 grade of Chinese National Standards. Compared with traditional methods on separation of W and Mo, the new process exhibited obvious advantages of low cost, high separation factor of W/Mo, environmental friendliness, which is expected to make good economic and social benefits.