Intensification of solvent extraction in an additively manufactured microfluidic separator

Abstract

Solvent extraction is an integral chemical and biochemical separation process that is drastically intensified in microfluidic systems. A novel high-throughput micro-separator was additively manufactured for the intensification of liquid–liquid separation. The micro-posts array within the flow plate generated a capillary pressure gradient on the non-wetting organic phase, enabling continuous, membrane-free, and density-independent phase separation. The device was integrated with an upstream micromixer for aqueous isobutanol extraction, allowing equilibrium extraction levels within 0.25 s. By capitalizing on the high depth-to-width aspect ratio of binder jetting, hydraulic pressure drops were substantially reduced, avoiding a detrimental effect on separation observed in current micro-separators. This novel architecture also enabled the rare ability to separate both “slug flow” and the highly effective but challenging “dispersed droplet flow”. Near-complete separation of the aqueous and organic phases was attained at flow rates up to 15 ml/min, under interfacial tensions of 48.9 and 10.9 mN/m, and aqueous:organic inlet flow ratios of 1:1 and 2:1. Separation performance deteriorated at 20 ml/min due to an increase of velocity gradients near the outlets, leading the wetting aqueous phase to exit from the organic outlet. Owing to its simplicity, manufacturing merits, and robust separation performance, this device addresses key requirements for achieving industrial-level throughputs using a “scale-up via number-up” approach.