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

点击翻译按钮获取中文摘要

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.