Liquid–liquid extraction for efficient synthesis and separation by utilizing micro spaces

Enhancement of mass transfer between two phases and improvement of extraction efficiency are expected if features of micro spaces are adopted for a liquid–liquid two-phase process. In this work, three extraction operations, contact flow in a Y-shaped microchannel, segmented flow and emulsification, have been investigated. Extraction using segmented flow is dependent on mass transfer by molecular diffusion and its rate is enhanced by the internal circulation flow generated inside slugs. The extraction rate can be controlled precisely by adjusting operational parameters such as the flow rate and the flow rate ratio. Liquid–liquid two-phase separation can be achieved instantly. Thus, continuous operation of a process involving liquid–liquid extraction and then two-phase separation is expected to be possible. For extraction based on emulsification, rapid extraction is made possible owing to significant increase in the interfacial area. Though extraction itself is rapid, liquid–liquid separation may take a long time because coalescence of stable emulsions requires time. It is suitable for systems strongly requiring only rapid extraction. Advanced reaction–separation systems can be developed by combining the extraction operations, making full use of the characteristics of segmented flow or emulsification and the reaction.