协同萃取体系的研究——Ⅱ.DMHMP和HEHEHP协同萃取UO_2(NO_3)_2的机理

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

摘要: 本文研究了甲基膦酸二(1-甲庚)酯(DMHMP)和2-乙基已基膦酸单(2-乙基己基)酯(HEHEHP)协同萃取硝酸钠酰。用斜率法测得协萃络合物的组成为UO_2(NO_3)(HA_2)·DMHMP。在20℃时(离子强度为0.5)协萃反应平衡常数1gβ_(12)=4.95。并求得了热力学函数ΔH、ΔZ和ΔS分别为—2.50×10~4J·mol~(-1)、-2.75×10~4J·mol~(-1)和8.61J·mol~(-1)·K~(-1)。依据锥角堆积模型讨论了协萃反应机理。

Abstract: 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.