Solubility of ammonium metal fluorides in aqueous ethanol mixtures - implications for scandium recovery by
Edward Michael Peters1, Michael Svärd2, Kerstin Forsberg2
1MEAB Chemie Technik GmbH Dennewartstraße 25 52068 Aachen Germany.
Abstract:
The recovery of scandium from waste streams of other mining and metallurgical processing industries is gaining research interest due to the scarcity of scandium-containing ores. Hydrometallurgical techniques such as leaching, solvent extraction and crystallization amongst others have been successfully applied to recover scandium salts from such waste streams. Scandium can be recovered as (NH4)3ScF6 by antisolvent crystallization from NH4F strip liquors obtained after solvent extraction. The coextraction of metal impurities such as Fe, Al, Zr and Ti causes contamination of the final solid product. The extent of coprecipitation of ammonium metal fluorides depends on their initial concentration in the strip liquor and their solubility in the NH4F-antisolvent mixtures. Here, the solubility of ammonium metal fluorides of Sc, Zr, Fe, Al and Ti is reported separately in 3 mol L-1 NH4F-ethanol mixtures at 25 °C as well as in a system containing all five solid phases. The solubility of (NH4)3ZrF7 is slightly higher than that of (NH4)3ScF6, while the solubilities of (NH4)3FeF6 and (NH4)3AlF6 are significantly lower in comparison to (NH4)3ScF6. The solubility of (NH4)2TiF6 is 1-2 orders of magnitude higher than those of other ammonium metal fluorides. When a mixture of ammonium metal fluoride salts is dissolved in the same 3 mol L-1 NH4F-ethanol mixture as for the individual salts, the resultant solubility of the ammonium metal fluorides of Sc, Zr and Fe decreases significantly, while the resultant solubility of ammonium aluminum hexafluoride increases. This is likely due to changes in solution speciation with increased NH4F concentration and ionic strength.
More Related Videos
07:45Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes
Published on: August 16, 2018
07:47Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles
Published on: November 27, 2015
Related Concept Videos
Reduction of Alkynes to trans-Alkenes: Sodium in Liquid Ammonia
When dissolved in liquid ammonia, an alkali metal,...
Precipitation of Ions
The equation that describes the equilibrium between solid calcium carbonate and its solvated ions is:
Extraction: Advanced Methods
Qualitative Analysis
For instance, group IV...
Washing, Drying, and Ignition of Precipitates
Formation of Complex Ions
