糖析基三液相体系萃取分离铂钯铑的选择性机理研究

The addition of sugar in the acetonitrile - water mixture induces two-phase formation. A stable sugaring-out based three-liquid-phase system appears by adding organic solution into the two phase system of acetonitrile - water mixtures. Sugaring-out based three-liquid-phase has the advantages of higher selectivity, lower required agent concentration for phase separation and wider use scope in extraction and separation of platinum (Pt(IV)), palladium (Pd(II)), rhodium (Rh(III)). The selectivity mechanism of sugaring-out based three-liquid-phase in extraction of Pt(IV), Pd(II) and Rh(III) is still largely not clear. The project is to study the closely relationship between phase-forming process of sugaring-out based three-liquid-phase and partition behavior of Pt(IV), Pd(II) and Rh(III), using a variety of spectroscopic methods to detect the phase structure changes with the variation of extraction reaction conditions, to study the reason that the change in partition behaviors of metal ions caused by the changes in phase structure, to clarify the s selectively partition mechanism of metal ions along with the phase-forming process. It can provide the theoretical basis for controlling the target metal ions partition behaviors in sugaring-out based three-liquid-phase.

糖分子的析相作用可导致乙腈水溶液形成双水相体系，在此基础上加入一个有机上相，可构成糖析基三液相体系。糖析基三液相体系在萃取分离铂、钯、铑离子时具有分离选择性高，所需析相剂浓度低及适用范围宽的优势。但是对于糖析基三液相体系萃取分离铂、钯、铑的选择性分离机制并不清楚。本课题拟通过考察铂、钯、铑离子在三液相间的分配行为与萃取体系成相过程之间的紧密关系，采用多种分子光谱学手段检测萃取条件变化时糖析基三液相体系成相过程中相结构的变化，研究相结构变化导致铂、钯、铑分配行为变化的原因，阐明金属离子伴随糖析基三液相体系成相过程完成选择性分配的微观机制，为调控目标金属离子在糖析基三液相间的选择性分配提供重要的理论依据。

糖析基三液相体系在处理复杂多金属体系时具有分离选择性高、所需成相剂浓度低及适用范围宽的优势，本项目着重研究该体系具备以上优势的成因。通过该研究，首先确立了一种高效的糖析基三液相从多组分复杂体系中萃取目标金属离子的方法，研究考察了成相糖种类与浓度，酸度，初始水溶液与已经溶液体积比、温度等因素对铂钯铑在三相间选择性分配的影响，发现双糖的析相能力要优于单糖，增大糖浓度有利于乙腈相体积的增大，从而提高铂在该相的萃取率，低温会降低形成稳定三相所需要的糖的浓度。糖析诱导的三相体系除了构成稳定三相时使用的糖浓度较低外，在针对高酸体系中目标产物的分离方面，具有明显的优势。本研究从分子层次解释糖析基三液相萃取这一新型萃取技术在萃取复杂多金属离子体系中具有高分离选择性的微观机制及萃取机理。采用红外、界面张力等表征手段对糖析萃取分离选择性的机理进行了详细研究。多种表征结果综合表明：萃取行为发生在宏观相形成之前，微观萃取行为伴随着微观聚集体的形成而发生，宏观相的生成只是萃取完成的结果。