Uranium extraction from partially neutralised and diluted phosphoric acid using a synergistic organophosphorous solvent mixture

A process is described for the separation of uranium from partially neutralised and diluted phosphoric acid (PNDA) which is generated in fertiliser plants when phosphoric acid is used to scrub ammoniacal vapours from the neutralisation reactors. The separation process is based on solvent extraction using a synergistic mixture of di-2-ethyl hexyl phosphoric acid (DEHPA) with tri-n-alkyl phosphine oxide (TAPO). The effects of process parameters including concentration of DEHPA and TAPO, temperature and degree of neutralisation of acid have been investigated. Laboratory scale and pilot plant scale tests have been carried out. The extraction reaction is found to be exothermic with enthalpy effect of 30 kJ/mol. Tests on stripping of extracted uranium and recovery of uranium have been carried out and results are reported. Analysis of data indicates significant differences in the mechanism of uranium extraction from PNDA and the mechanism reported in literature for extraction of uranium from weak phosphoric acid using a similar solvent mixture.