Extraction and separation of W and rare earth from H2SO4-H3PO4 mixed acid leaching liquor of scheelite by primary amine N1923

Abstract

Tungsten and rare earth (La) in scheelite can be leached effectively using H2SO4-H3PO4 mixed acid leaching liquor, which contains W, La, and high concentrations of sulfuric and phosphoric acids. It is important to recover W and La from the leaching liquor to efficiently use scheelite. In this study, N1923 extraction and a two-step stripping process were developed to efficiently extract and separate W and La from the leaching liquor. First, W and La were directly extracted using N1923 from the leaching liquor (100 g/L sulfuric acid and phosphoric acid). Under the optimal conditions of N1923 (30% v/v), isooctanol (10% v/v), sulfonated kerosene (60% v/v, O/A (organic/aqueous ratio) 1:1, temperature 25 °C, and contact time 10 min), 99.9% W, and 96.5% La were extracted. High concentrations of sulfuric acid and phosphoric acid were not beneficial for this extraction process. Next, La was separated from the loaded organic phase by stripping using an HCl solution. Under the optimum conditions (HCl 2.5 mol/L, stripping time 20 min, O/A 1:1, and 40 °C) 89.7% La and almost no W were stripped after single-stage stripping. After three cross-current stripping stages, the total La and WO3 stripping reached 99.0% and approximately 0.1%, respectively. La was successfully separated from W. Finally, the remaining W was stripped using an ammonia solution. The amount of WO3 stripped exceeded 99% under the optimum ammonia concentration of 4.0 mol/L, stripping temperature of 40 °C, stripping time of 10 min, and organic/aqueous ratio of 1:1. W and La were extracted and separated efficiently from the H2SO4-H3PO4 mixed acid leaching liquor by N1923 and two-step stripping, respectively.