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液—液—液三相萃取分离铂钯铑的选择性机理
Alternative TitleSelectivity Mechanism in Three-Liquid-Phase Extraction and Separation of Pt(IV), Pd(II) and Rh(III)
张超
Subtype博士
Thesis Advisor刘会洲
2013-05-01
Degree Grantor中国科学院研究生院
Degree Discipline化学工艺
Keyword液-液-液三相体系   pt   pd   rh   盐析   糖析   萃取选择性
Abstract本论文针对含铂钯铑的盐酸浸出液中PtCl62-,PdCl42-和RhCl63-的萃取分离,提出一种由乙腈-盐-水双水相与非极性有机相组成的新型液-液-液三相体系。详细考察了铂钯铑三液相选择性分配的各种影响因素,采用多种表征手段研究了相结构变化导致铂钯铑三相选择性分配的微观机理,建立了三相萃取分离的热力学数学模型,为实现铂钯铑三相萃取选择性调控奠定了理论基础。 研究取得的主要结果如下: (1)考察了影响Pt(IV)/Pd(II)/Rh(III)在S201-乙腈-NaCl-H2O体系中选择性分配的因素。溶质的选择性分配与三液相成相行为密切相关。成相盐的种类与浓度是影响形成稳定三液相的重要因素,增大成相盐的浓度有利于下相中更多的乙腈分子脱水导致乙腈中相体积增大,从而引起中相中Pt(IV)的萃取率上升。使用碳链较长的烷烃作为稀释剂有利于提高Pt(IV)在乙腈相的萃取率。增大初始加入的乙腈溶液的体积同样有助于更多的Pt(IV)从水相转移进入乙腈相。盐的加入导致乙腈水混合溶液发生相分裂是由于盐的加入会去竞争与乙腈分子结合的水分子,从而造成乙腈分子与水分子之间的氢键打破。Pt(IV)伴随乙腈分子与水分子的脱离而离开水相,完成萃取分离过程。 (2)针对盐析诱导的三相体系的构成需要较高成相盐浓度的问题,构建了糖析诱导的三液相体系,考察了成相糖种类与浓度,酸度,初始水溶液与乙腈溶液体积比,温度等因素对Pt(IV)/Pd(II)/Rh(III)在三相间选择性分配的因素。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Pt(IV)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。 (3)针对以上两种三相体系都需要加入额外的成相剂的问题,构建了一种仅仅依靠溶液极性不同,不需要加入成相剂就可以形成的稳定的三相体系,其体系组成为S201-[C4mim][PF6]-H2O,并完成了Pt(IV)/Pd(II)/Rh(III)三种金属离子一步萃取分离的目标。酸度是影响该萃取体系萃取效率的关键因素,高酸度下由于[C4mim][PF6]容易发生降解,从而导致[C4mim][PF6]相Pt(IV)萃取率的下降。提高盐浓度有助于Pt(IV)向[C4mim][PF6]转移,盐析效应导致PtCl62-在乙腈相的萃取率上升。提高IL与初始水溶液的体积比有助于提高PtCl62-的萃取率。离子液体相的Pt(IV)可通过与高浓度的HNO3溶液接触完成反萃。Pt(IV)被纯[C4mim][PF6]萃取的机制最可能为PtCl62-和PF6?之间的阴离子交换机制。 (4)采用紫外、小角X射线散射,红外、拉曼、界面和频光谱、界面张力、核磁等多种表征手段对三相萃取分离选择性的微观机制进行了详细研究。紫外研究结果表明目标金属离子的物化性质、物种形态会影响其分配行为;小角数据表明盐的加入导致乙腈水溶液中出现微观聚集体;红外拉曼数据证实了乙腈分子与Pt(IV)之间的相互作用;界面和频光谱和界面张力表征显示随着盐的加入,乙腈分子在气/液界面的吸附加剧,目标金属离子的加入会削弱气/液界面吸附的乙腈分子,说明吸附的乙腈分子受到了指向溶液内部的力。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。 (5)建立了溶质分配行为与乙腈在两相间质量分数差之间的数学模型,Pt(IV)/Pd(II)的分配系数与乙腈质量分数差之间符合Diamond-Hsu模型三次拟合方程,Rh(III)的分配行为符合Diamond-Hsu模型一次拟合方程,说明溶质与相组分之间不同的相互作用力是造成Pt(IV)/Pd(II)与Rh(III)在乙腈盐双水相间选择性分配的主要原因。以乙腈在两相间的质量分数差为纽带,建立了溶质分配行为与界面张力之间的数学模型。按照构建数学模型计算得到的溶质分配行为参数与实验值比较吻合。最后初步对三相萃取热力学模型进行了探讨。
Other AbstractThe extraction and separation of PtCl62-,PdCl42- and RhCl63- from their hydrochloric acid leach solution with a novel three-liquid-phase system (TLPS) constructed by acetonitrile-NaCl aqueous two phase system and non-polar organic phase was systematically studied in the dissertation. The paramenters that effect the three liquid phase extraction and separation of PtCl62-,PdCl42- and RhCl63- were investigated in detail and the influence of phase structure change on selective distribution were also studied through a variety of characterization means. The model of the three-liquid-phase extraction separation selectivity was established, which provided a theoretical basis for the realization of the solute distribution regulation. The main research contents include: (1) The paramenters that influenced Pt(IV)/Pd(II)/Rh(III) in S201-acetonitrile- selective distribution were investigated. The partitioning behaviors of metal inos in three phases were closely related to the phase forming behavior of TLPES. The type of phase-forming components and their concentrations are the important factors influenced the stability of the formation of three-liquid-phase. Increase in phase-forming concentration resulted in the volume of ACN-phase increased, which resulted in the Pt(IV) mass fraction in ACN-phase increased. Using long carbon chain alkane as diluent and increasing the adding acetonitrile solution were benifet to the transfer of Pt(IV) from aqueous phase to ACN-phase. The addition of NaCl broke the hydrogen bonds between water molecule and acetonitrile, which was the reason of phase separation in acetonitrile aqueous solution.
Pages164
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8281
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
张超. 液—液—液三相萃取分离铂钯铑的选择性机理[D]. 中国科学院研究生院,2013.
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