对二异丁基甲酮( DIBK)和TBP从HSCN介质中协同萃取锆铪的性能及热力学进行研究,采用对数函数外推法求得DIBK-TBP体系萃取反应的热力学平衡常数分别为log( K12,Zr)=4.73和log(K12,Hf)=-5.09,锫铪与SCN-形成配合物Zr(SCN)3+和Hf(SCN)3+的稳定性常数分别为1 x109.86和1×10-0.80,而铪的分配比在硫氰酸盐存在时要大于锆的分配比,说明过渡金属离子锆和铪在硫氰酸盐存在时与一般金属离子与配位体形成的配合物的稳定性常数愈大,金属离子的分配比愈大的规律相矛盾,并计算出萃取反应的焓变分别为△Hzr =-11.43 kJ·mol-1和△HHf=-7.80kJ·mol-1,说明对锆铪的萃取反应为放热反应,升高温度不利于萃取反应的进行,常温下自由能变分别为△GZr =-26.54 kJ·mol-1和△GHf =28.57 kJ·mol-1,熵变分别为△Szr =51.54 J·(K·mol)-1和△SHf=-124.07 J·(K·mol)-1,说明铪离子比锫离子更易与SCN-形成配位键,从而生成中性分子Hf(SCN)4与有机相发生溶剂化作用而进入有机相中.
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