Investigation of synergistic extraction system: Pt.2

In the synergistic extraction of uranium nitrate with binary system of di-(1-methyl heptyl) methyl phosphate (DMHMP) and 2-ethyl hexyl 2-ethyl hexyl phosphonic acid (HEHEHP), there are three kinds of equilibria. The equilibrium constants of DMHMP, HEHEHP and binary synergistic extraction are determined to be lgβ10 = 3.64 (DMHMP), lgβ20 = 3.62 (HEHEHP), lgβ12 = 4.95 (DMHMP-HEHEHP). By determining the effect of temperature on the distribution ratio, ΔH, ΔZ, and ΔS of synergistic extraction are evaluated to be -2.5 X 104 J·mol-1, -2.75 x 104 J·mol-1 and 8.61 J·mol-1·K-1. The extraction mechanism of uranium nitrate are discussed. A possible structure of the synergistic extracting complex is proposed based on a cone-angle model