DHDEC MP-TBP/煤油对U(Ⅵ)的萃取

EXTRACTION OF URANIUM(Ⅵ) WITH DHDECMP-TBP/KEROSENE FROM NITRIC ACID SOLUTION

DHDECMP TBP/煤油体系从 1 0mol/LHNO3 UO2 (NO3 ) 2 介质中萃取U (Ⅵ ) ,除了存在TBP和DHDECMP的单独萃取反应外 ,还存在着DHDECMP TBP的协同萃取反应。形成的萃合物分别为UO2 (NO3 ) 2 ·2TBP、UO2 (NO3 ) 2 ·2DHDECMP和UO2 (NO3 ) 2 ·DHDECMP·TBP。实验测定了TBP/煤油、DHDECMP/煤油和DHDECMP TBP/煤油协同萃取反应的ΔG、ΔH、ΔS和平衡常数K。实验结果表明 ,DHDECMP TBP/煤油萃取UO2 + 2 的分配比 ,随DHDECMP、TBP、HNO3 的浓度的增加而升高 ,随水相中常量Gd3 + 浓度的增加或温度升高而降低。H2 C2 O4 能抑制对铀的萃取 ,有效地降低铀的分配比 ,有利于铀的反萃。

The mechanism of extraction of uranium(Ⅵ) with TBP/kerosene, DHDECMP/kerosene and DHDECMP TBP/kerosene from nitric acid solution is studied. The extracted species is found to be UO 2(NO 3) 2·2TBP, UO 2(NO 3) 2·2DHDECMP and UO 2(NO 3) 2·DHDECMP·TBP, respectively. The extracting equilibrium constants K for these systems are directly measured and their thermodynamic functions Δ H , and Δ S are obtained from the dependence of K upon temperature. The distribution ratio of uranium(Ⅵ) increases with the increase in concentration of DHDECMP, TBP or HNO 3, but decreases with the increase in Gd 3+ concentration or temperature. The addition of oxalic acid depresses the extraction of uranium(Ⅵ), probably dues to its complexion and therefore is beneficial to the stripping of the latter.