叔胺N235-PtCl_6^(2-)-HCl萃取体系第三相中“超浓盐酸”的生成及其微乳结构

Formation of super-concentrated hydrochloric acid in the third phase in tertiary amine N235-PtCl_6^(2-)-HCl system and its influences on the Pt microemulsion extraction

采用分子谱学及同步辐射X射线小角散射(SAXS)等表征手段,研究了三烷基叔胺(N235)萃取PtCl62-体系中第三相的形成及溶液微观聚集态结构的变化对PtCl62-萃取行为的影响.实验结果表明:萃铂有机相中第三相的形成与萃入有机相的酸和水含量的变化导致溶液结构发生变化有关;与含铂高酸度盐酸水溶液平衡后,第三相微乳水团中形成H+/H2O摩尔比远大于37wt%常规饱和浓盐酸的"超浓盐酸";"超浓盐酸"微观介质内H+和Cl-的大量聚集增浓对Pt离子的络合配位状态产生影响,H+参与了Pt离子配位状态的转变;第三相"超浓盐酸"形成后,使得微乳水团中大量存在的H+有可能参与调控水团中各种HmPtCl6z+复合络离子配位状态的相对含量,被H+活化的叔胺(R3NH+)与Pt离子的各种配位状态的匹配程度最终决定了铂在第三相中的萃取行为.

Formation of the third-phase in tertiary amine （N235） -PtC16^2- -HCl system, the microscopic phase structural evolution of platinum-loaded organic phases before and after the occurrence of the third-phase are investigated. The third-phase is characterized by various spectroscopic techniques, and the small angle X-ray scattering （SAXS） experiments demonstrate the appearance of nano-aggregates, i.e. water-in-oil reversed micelles, in the third phase. The experimental results indicate that, （1） formation of the third phases is related to the aggregation behaviors of nano-reversed micelles in which a super-concentrated hydrochloric acid formed with the H＋ to H20 molar ratios being much higher than that of the conventional 37 wt% saturated hydrochloric acid; （2） occurrence of the super-concentrated HCl results in a great amount ofH＋ and Cl^- ions enriched and confined within the nano-water pools of W/O reversed micelles in third phase. Therefore, the coordination behaviors of platinum complex ions in that super-concentrated hydrochloric acid are very different from its corresponding behaviors in bulk aqueous solutions. It is possible that H^＋ ions participate in the formation of such complexes as HmPtC16^z＋ in the super-concentrated hydro-chloric acid; （3） the relative contents of various HmPtCI6^z＋ complexes are different corresponding to the H^＋ ion concentrations in confined nano-water pools. The association ability of the acidified tertiary amine N235 molecules （R3NH^＋） with various HmPtC16^z＋ complexes plays an important role in affecting the platinum extraction behaviors.