Pysicochemical Phenomena Involved in the Recovery of Uranium from Phosphate by BiDiBOPP/di-n-HMOPO and Development of New Cationic Extractants

This paper studied the recovery of uranium (VI) from 5.3 M phosphoric acid by bis(1,3-dibutoxypropan-2-yl) phosphoric acid (BiDiBOPP)/di-n-hexyl octyl metoxy phosphine oxide (di-n-HMOPO) and 5 analogs of BiDiBOPP mixed with tri-n-octylphosphine oxide (TOPO) diluted in Isane IP 185. First, this paper shows that the experimental and calculated distribution coefficients of uranium (VI) as a function of the concentration of BiDiBOPP and di-n-HMOPO match by using a thermodynamic model previously developed and validated on the bis(2-ethylhexyl) phosphoric acid (D2EHPA)-TOPO system. In this model the formation of complexes between the cationic extractant (HL) and the solvatant extractant (S) such as (HL)2, (HL)2S, (HL)2S2 and (HL)5S and the recovery of uranium (VI) as UO2(HL)2L2S, UO2L2S and UO2(HL)2L2 were taken into account where L refers to the deprotonated form of the cationic extractant HL. Secondly, the investigation of the extraction of uranium (VI) by the BiDiBOPP analogs mixed with TOPO in Isane IP 185 showed that the presence of oxygen atoms in the two aliphatic chains of BiDiBOPP and the increase of the hydrophobicity of these chains influence strongly the extraction properties.