Separation of tungsten and molybdenum with solvent extraction using functionalized ionic liquid tricaprylmethylammonium bis(2,4,4-trimethylpentyl) phosphinate
23 May 2020
Revised: 19 August 2020
Accepted: 25 August 2020
Available online: 27 August 2020
Abstract: Functionalized ionic liquids (FILs) as extractants were employed for the separation of tungsten and molybdenum from a sulfate solution for the first time. The effects of initial pH, extractant concentration, metal concentrations in the feed, etc., were investigated in detail. The results showed that tricaprylmethylammonium bis(2,4,4-trimethylpentyl)phosphinate ([A336][Cyanex272]) could selectively extract W over Mo at an initial pH of 5.5, and the best separation factor βW/Mo of 25.61 was obtained for a solution with low metal concentrations (WO3: 2.49 g/L, Mo: 1.04 g/L). The [A336][Cyanex272] system works well for solutions of different W/Mo molar ratios and different concentrations of metal ions in the feed. The chemical reaction between [A336][Cyanex272] and W followed the ion association mechanism, which was further proven by the FTIR spectra of loaded [A336][Cyanex272] and free extractant. The stripping experiments indicated that 95.48% W and 100.00% Mo were stripped by a 0.20 mol/L sodium hydroxide solution. Finally, selective extraction of W from Mo was obtained for two synthetic solutions of different high metal concentrations, and the separation factor βW/Mo reached 23.24 and 17.59, respectively. The results suggested the feasibility of [A336][Cyanex272] as an extractant for the separation of tungsten and molybdenum.