Micro-Contactor for Extraction and Permeation

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The objective of this project is an experimental and theoretical investigation of different reactive mass transfer test systems in a nondispersive, microstructured counter-current apparatus. There it is possible to perform kinetic experiments with very small sample volumes in order to quantify diffusion and/or reaction limited mass transfer resistances under well-defined constraints (i.e. geometry, hydrodynamics). After construction of the micro-contactor, an evaluation of the hydrodynamic limits and modeling the reactive mass transfer for standardized EFCE test system (zinc/di-(2- ethylhexyl)phosphoric acid) in the previous period was performed. The developed methodology will be validated for the two model substances like germanium, as a valuable metal in hydrometallurgy, and mandelic acid, as chiral test substance in pharmacy. This will be done for reactive extraction and liquid-membrane-permeation (LMP), where reactive mass transfer phenomena are still not fully understood and predictable. The micro-structured dimensions allow an easy implementation of on-line sensors (e.g. confocal Raman-microscopy) for a non-invasive online-analysis of the extraction kinetics. The microchannel can be screened in ¿m range in all three dimensions by an automated mechanical shift unit producing local concentration profiles. Additionally, this method yields quantitative and as well as chemical structure information (in organic, as well as in aqueous systems). Both solutes have diametrical characteristics compared to zinc (increasing impact of reaction and diffusion respectively) and serve as a basis for recovery of other solutes when using this new developed methodological approach. A potential user will be enabled in an early process design stage to judge process operability and technology (LMP or extraction to be used). The results of the continuous tests serve as basis for fast and safe design (microcontactor, non-dispersive operation) and numbering-up allows higher throughputs at minimum risk (e.g. risky high-voltage emulsion splitting with LMP is not necessary).