INVESTIGATION OF SYNERGISTIC EXTRACTION SYSTEM II.SYNERGISTIC EXTRACTION OF URANIUM NITRATE BY DMHMP AND HEHEHP

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, △H,△Z, and △S of synergistic extraction are evaluated to be -2.5×104J.mol-1 ,-2.75×104J. mol-1 and 8.61 J.mol-1.K-1 . The extraction mechanism of uranium nitrate arc discussed. A possible structure of the synergistic extracting complex is proposed based on a cone-angle model.