Fast extraction of rare earth mixtures by membrane dispersion micro-extractors

Abstract

Many extraction systems in practical industry or analytical science need to be completed at a high phase ratio (>20:1). However, operation at high phase ratio brings some issues such as long mass transfer distance, high mass transfer resistance and low specific surface area, which leads to the low extraction efficiency or long residence time. In this paper, gas-liquid-liquid (G/L/L) micro-dispersion technology is used to enhance the mass transfer and extraction of mixed rare earth elements (REEs). The results of liquid-liquid (L/L) system show that the extraction efficiency decreases as the phase ratio increases, further reflecting the challenge of extraction at high phase ratio. Subsequently, the gas phase is introduced to intensify the mass transfer. The results show that the overall mass transfer coefficient after gas introduction can be up to 8 times as high as that of the non-gas introduction, which demonstrates that introducing the gas phase greatly promotes the mass transfer and reduces the competing reaction between different REEs, achieving the enrichment and recovery of rare earth ions successfully. In addition, the extraction of medium and heavy REEs mixtures are also intensified by this method, which proves the universality and versatility of this technique.