Synthesis of silica/extractant hybrid membranes by sol-gel methods and the highly selective active-transport of precious metals.

合成了4种贵金属选择性萃取剂，并将其应用于二氧化硅/萃取剂杂化膜分离体系。这些萃取剂是含有硫脲基团和硫醚或苯胺基团和硫醚或苯胺基团和氨基或硫醚基团和酸性基团或肟基和酸性基团的萃取剂。首先，用这些萃取剂考察了银(I)、钯(II)、金(III)、铂(IV)等贵金属对铜(II)、镍(II)、钴(II)、镉(II)、铅(II)、锌(II)和铁(III)等贱金属的选择性。萃取剂对贵金属具有较高的选择性。用这些萃取剂提取的贵金属在盐酸、硫脲水溶液、硫脲和盐酸的混合溶液中表现出良好的反萃效果。因此，这些萃取剂适用于在膜两侧进行萃取和反萃的膜分离系统。以烷氧基硅烷衍生物或聚硅氧烷为膜材料，以所合成的萃取剂为原料，采用多种制备方法制备了二氧化硅/萃取剂杂化膜。用上述反萃剂考察了贵金属在膜上的吸附和解吸行为。使用含有肟型萃取剂的杂化膜可以有效地实现铜(II)的主动迁移。该杂化膜也能够实现钯(II)的主动转运，但需要较长的时间才能实现。利用杂化膜分离回收贵金属时，膜的组成、原料、萃取剂和反萃剂的种类等诸多问题亟待解决。

Four kinds of selective extractants for precious metals were synthesized to apply these extractants to the separation system using silica/extractant hybrid membranes. These extractants are ones containing a thiourea group and a thioether or an aniline group and a thioether or an aniline and an amido group or a thioether and an acidic group or an oxime group and an acidic group. First, the selectivity for precious metals such as silver (I), palladium (II), gold (III), platinum (IV) over base metals such as copper (II), nickel (II), cobalt (II), cadmium (II), lead (II), zinc (II), and iron (III) was examined using these extractants. The extractants showed the high selectivity for precious metals. The precious metals extracted with these extractants exhibited the good stripping with hydrochloric acid, aqueous thiourea solutions, and the mixture solutions of thiourea and hydrochloric acid. Thus, these extractants were found to be suitable for the membrane separation system that carries out extraction and stripping on the both sides of the membrane. The silica/extaractant hybrid membranes were prepared by some preparation methods with alkoxysilane derivatives or polysiloxisane as a membrane material and the extractants synthesized in this study. The adsorption and desorption of precious metals on the membrane were examined using the stripping reagents mentioned above. The active transport of copper (II) was able to realize effectively using the hybrid membrane containing the oxime-type extractant. We also was able to realize the active-transport of palladium (II) with this hybrid membrane, but we needed much time for the active-transport. We have many problems, the composition and starting materials of the membrane, and the kinds of extractants and stripping reagents, to solve for separation and recovery of precious metals using the hybrid membrane.