Design Guideline for Passive Microextractors: From Cocurrent Flow to Countercurrent Flow

Passive countercurrent microextractors with high throughputs have potentially broad applications in industrial-scale solvent extraction and hazardous waste disposal. To date, no design guideline has been available for developing such microextractors based on passive cocurrent microextractors. In this study, an oscillating feedback microextractor was chosen as an example system to provide a clear roadmap for bridging the gap between passive co- and countercurrent microextractors and achieving high-throughput countercurrent microextraction. Four steps were necessary, namely, (1) determination of the countercurrent flow arrangement strategy, (2) selection and modification of a primary passive cocurrent microextractor, (3) establishment of a passive single-unit countercurrent microextractor, and (4) parallelization of the passive single-unit countercurrent microextractor with the aim of achieving high throughput. The development from a passive cocurrent microextractor to a passive and high-throughput countercurrent microextractor was demonstrated using the oscillating feedback microextractor.