Separation of Uranium from the Leaching Solutions

Ion exchange and extraction with organic solvents have proved effective in separating uranium from the leaching solutions. Combinations of the ion exchange proce.ss with solvent extraction are also known. This is normally preceded by separation of the leaching solution from solids by multistage filtration or countercurrent decantation followed by clarification e.g. over a bed of sand. 

Separation by ion exchange Strongly basic or weakly basic ion exchange resins are used to separate selectively the uranium from the weakly acidic or alkaline solutions from the leaching step. The uranium is eluted from the ion exchange resins with nitrate or chloride solutions as anionic (carbonato- or sulfato-) complexes. 

Separation by solvent extraction Uranium can be extracted from aqueous solutions using extraction agents into the solvent phase, from which it can be stripped. The extraction agents used are phosphorus compounds such as di-(2-ethylhexyl)-phosphate, tri-n-butyl-phosphate and tri-n-octylphosphine oxide as well as primary, secondary and tertiary amines in salt form or as quaternary ammonium salts. The extraction agents are diluted with inert hydrocarbons, preferably kerosene, to concentrations of 4 to 10% by volume. The solubility of the amine salts, particularly the hydrogen sulfates, chlorides and nitrates is increased by adding long chain alcohols (e.g. isodecanol). 

The extraction processes, which are mainly carried out in mixer-settler plants, are preferably carried out with acidic leaching solutions. For the different processes. see the marginal notes. 

Stripping of the uranium compounds from the organic phase with aqueous salt solutions 

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