Solvent extraction of uranium from saline leach liquors using DEHPA/Alamine 336 mixed reagent

The presence of chloride in sulphuric acid leach liquors has a negative impact on the solvent extraction process for the recovery of uranium using tertiary amine reagents, such as Alamine 336. This can increase operating costs, and limit the use of saline water as plant process water. This study is based on the use of a mixed solvent containing DEHPA (di-2-ethylhexylphosphoric acid) and Alamine 336, and examines the performance of this system for uranium recovery from an overall process perspective. It investigates the impact of chloride, sulphate and acidity on uranium extraction and discusses the selectivity of the mixed reagent for uranium over iron (III) in the context of loading and selective scrubbing. The study also presents results of sulphuric acid (5–8 M H2SO4) and alkali (1 M Na2CO3) stripping of uranium, and the need for addition of phase modifiers such as TBP (tributylphosphate), DBBP (dibutyl-butyl phosphonate) and TOPO (trioctyl phosphine oxide), to prevent third phase formation.

► Mixed DEHPA/Alamine 336 reagent for uranium extraction from saline sources.
► Improved selectivity for uranium over iron (III) when compared with DEHPA.
► Solvent can be stripped with sodium carbonate or strong sulphuric acid.