Solvent extraction of uranium in the presence of chloride

Uranium is commonly extracted from ores by leaching in sulfuric acid. The resultant leach solutions are treated by solvent extraction to purify and concentrate the uranium. Tertiary amines are used extensively for this purpose because of good selectivity towards uranium. The presence of chloride at relatively high levels has a deleterious effect on uranium extraction. In Australia, the issue of chloride is important because of the high salinity bore water frequently used as process water in remote areas. This problem can be exacerbated with recycling of process waters. This paper presents a study on the effect of chloride in the extraction of uranium by amine and alkyl phosphoric acid extractants and discusses the role of amine additives in these systems. It is shown that chloride concentration in the feed has a negative impact on uranium loading with Alamine 336 and this effect was quantified in terms of lower aqueous to solvent operating ratios, decreased uranium loading, increased staging requirement and increased uranium barrens. The extraction characteristics of solvent systems containing a mixture of DEHPA and primary, secondary or tertiary amines were tested with respect to chloride, Mo6+, Zr4+, V5+, Th4+, Al3+, La3+, and Fe3+. (author)