Extraction and separation of rare earth metals by a microreactor

In order to apply a microreactor to liquid-liquid extraction, the extraction of three rare earth metals (yttrium, europium and lanthanum) with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) as the extractant dissolved in toluene was performed on a microreactor, which has two inlets and an outlet. The microreactor was fabricated on a silicon wafer (20mm x 40mm) by photolithography and wet etching methods. It was observed that two phases successfully flowed while keeping an aqueous-organic interface in a microchannel (92μm in depth and 300-434μm in width) at volumetric flow rates from 5.6 × 10^-10 to 2.8 × 10^-9 m³/s. The extraction and back-extraction rates were measured under various concentrations of chemical species. In the microchannel, the metal transfer between the two phases accompanied with interfacial chemical reaction was confirmed to proceed satisfactorily in a short time (residence time = 0.7 sec).