电导法测定298.15K时硫酸氧钒离子对解离常数

为优化钒电池电解液配比和设置合理的充放电制度,需弄清自由钒离子活度和离子对的解离常数及其热力学性质.研究了电导法测定在298.15 K时水溶液中VOSO4.3.53H2O(s)的电导率,利用Origin数据拟合求出极限摩尔电导;采用改进的Ostwald稀释定律和改进的Davies方程求解活度系数,进而求得溶液的真实离子强度;采用Fuoss方法求解硫酸氧钒离子对的解离常数.经过数据处理得到298.15 K时硫酸氧钒极限摩尔电导率Λ0为203.2520325 S.dm2.mol-1,硫酸氧钒离子对的解离常数Kd为0.001 961 62,为电池性能有关的热力学性质提供了基础数据.

Determination of the Vanadyl Sulfate Ion-Pair Dissociation Constant at 298.15 K Using Electric Conductivity

To optimize electrolyte ratio of the vanadium redox flow battery and set a reasonable charge and discharge system,the free vanadium ion activity,ion-pair dissociation constant and other thermodynamic properties should be clarified.The conductivity of the VOSO4·3.53H2O(s)in aqueous solution was determined using the electric conductivity method at 298.15 K.The limiting molar conductance was obtained using the Origin data fitting and then the activity coefficient was solved with the improved Ostwald dilution law and the Davies equation,so as to obtain the true solution ionic strength.The vanadyl sulfate ion-pair dissociation constant was calculated through the Fuoss method.The vanadyl sulfate limiting molar conductance Λ0 is 203.252 032 5 S·dm2·mol-1 and the vanadyl sulfate ion-pair dissociation constant Kd is 0.001 961 62,which may provide a basic data for the battery thermodynamic properties.