滴定量热法研究UO_2(TTA)_2和Th(TTA)_4与N503协萃机理

STUDIES ON THE SYNERGISTIC EFFECT OF THE REACTION OF UO_2(TTA)_2, Th(TTA)_4 WITH N503 IN TOLUENE BY TITRATION CALORIMETRY

由于近代量热技术的成功,为协同萃取机理的研究提供了新的手段。它以金属的一元(或二元)配合物为底液,以第二(或第三)配体为滴定剂,用滴定量热方法直接测定在298K时二元(或三元)协萃反应过程中吸收或释放的热量。根据滴定量热曲线,确定配体与金属配合物,究竟是生成一级二元协萃配合物,例如,UO_2(TTA)_2·N503和Th(TTA)_4·N503,还是生成二级二元协萃配合物,例如Nd(TTA)_3·TOPO和Nd(TTA)_3·(TOPO)_2。

The thermodynamics of the reaction between UO2(TTA)2 and Th(TTA)4 with N,N-dimethylheptyl-acetamide (N503) in 'dry' and 'wet' toluene solution at 298.15 K has been studied by titration calorimetry. The heat of the reaotion is determined by TRONAC Model 1250 automatic isoperibol calorimeter. The data points and figures of titration curve are recorded by the computer automatically.From the experimental data, the addition of N503(L) to a toluene solution of UO4(TTA)2 and Th(TTA)4 will form one binary synergic adducts MA L and MA4L respectively according to the equilibriawhere β1 is the equilibrium constant and △H1 is the corresponding enthalpy change. An iterative technique of least-square analysis is used to calculate β, and △H , minimizing the error square sum by a computer program provided by M.Caceci then improved by Yang Hua.The calculated equilibrium constants and the thermodynamic function, including the entropy and free energy changes calculated simultaneously are summarized in Table 1, with uncertainties expressed as mean deviations.