Synthese von Alkyl-oxalat und -oxamat basierten Ionischen Flüssigkeiten als Extraktoren für die Separation von Seltenerdmetallen
Im Rahmen dieser Arbeit konnte die Syntheseroute zu drei völlig neuartigen Anionen-Klassen im Bereich der Ionischen Flüssigkeiten (ILs) etabliert werden. Ausgehend von Oxalylchlorid gelang in drei Stufen die Darstellung von Alkyl-oxalat, -oxamat und Dialkyl-oxamat basierten ILs. Das Ziel, hydrophobe...
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Table of Contents: In this thesis, the syntheses of three new coordinating anion-classes for Ionic Liquids (ILs) were realized. Starting with Oxalyl chloride the Alkyl-oxalate, -oxamate and Dialkyl-oxamate based ILs are synthesized in high yields and purity within three steps. The primary goal, namely the development of hydrophobic ILs as extractors for liquid-liquid extraction, was accomplished. The obtained Di(2-ethylhexyl)-oxamate based ILs are insoluble in water and stable against hydrolysis at acidic conditions. All three IL-anion-classes were successfully tested in the process of REE separation. Especially C8mim di(2-ethylhexyl)-oxamate is a high selective and efficient extractor, compared to the literature. Important for an industrial process was the establishment of Toluene as organic phase. The influences of the parameters on the selectivity and efficiency of the extraction were analyzed by systematic experiments. With the optimization of the relevant parameters, like the pH-value, the temperature, and the initial concentrations of each compound, a highly selective and efficient liquid-liquid extraction for a REE-separation was developed. Selective Scrubbing was successfully tested applying the same pH-value as used for the extraction step. In addition to the extraction, the conditions for an almost quantitative back-extraction by EDTA saponified by (2 ethylhexyl)imidazole were investigated. The basis for the development of a counter-stream liquid-liquid extraction for an industrial REE-separation was set with these results. Future experiments have to show whether C8mim di(2 ethylhexyl)-oxamate is applicable to multiple extraction cycles at constant levels of selectivity and efficiency. These experiments have to include repeated extractions without exchanging the organic layer. Furthermore, the long term stability of the respective IL and its extraction behavior with respect to selectivity and efficiency should be further analyzed. Regarding the application to industrial processes, the increasing selectivity by Scrubbing in between two extraction steps observed in our experiments should be investigated more deeply. Beyond the REE separation, Dialkyl oxamate based ILs are suitable for the REE recovery in an Urban mining process. Another potential application for this IL class is the separation of 5f- and 4f-metals. The nuclear waste management is one of the greatest challenges in separation processes in the future and might reduce the amount of nuclear waste.