Abstract:

The recovery of scandium(Sc) is difficult due to its low content in resources and large amount of other metals associated with. To solve this problem, the extraction, separation and stripping of Sc by three extractants:trialkyl phosphine oxides(Cyanex 923), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester(P507) and naphthenic acid, were compared in this article. The Cyanex 923 can efficiently extract Sc from a highly acidic solution. The P507 and naphthenic acid have high extraction efficiency of Sc in low acidic solution. The best acidity for the separation between Sc and zirconium(Zr), Sc and titanium(Ti) by Cyanex 923 is 1 mol/L. The separation ratios of Sc/Zr and Sc/Ti are 5.6 and 10.6, respectively. The largest separation ratios of Sc/Zr and Sc/Ti by P507 are 21 and 59.7, respectively, at an acidity of 2 mol/L. Though the P507 has a higher separation ratio, the loaded Sc on P507 is hard to be stripped by acid. Only the Sc loaded on Cyanex 923 can be efficiently stripped when the acidity of stripping acid is 0.4 mol/L. Taking account of both separation and stripping, the Cyanex 923 is more suitable to separate and recover Sc from the leaching liquor of secondary resources.

Key words: scandium, extraction, trialkyl phosphine oxides, ethylhexyl phosphonic acid mono-ethylhexyl ester, naphthenic acid