On the Operation of a Cascade of Mixing and Settling Extractors in the Modes of Chromatography and in Free Liquid Membranes

The following new possibilities are considered for the arrangement of extraction and separation processes in a cascade of mixing and settlement extractors: the use of the cascade as a chromatographic device for carrying out extraction and chromatographic separation processes on industrial scales; and the use of the principle of separation with a free liquid membrane. In contrast to the traditional countercurrent extraction process, the extractor cascade stages in the chromatography mode are connected only along the flow of the aqueous phase, and the organic phase is retained in the device by its complete recirculation between the settler and mixer in each stage of the cascade. In this case, the aqueous phase is fractionated into the organic phase. If the cascade is operated in the membrane extraction mode, then a liquid membrane that contains the extractant circulates between the extraction and re-extraction stages in each stage of the cascade separation process. A method for fractional liquid-membrane extraction is proposed. The operation of the extractors is adjusted by optimization in such a way that the entrainment of the organic phase is minimized and a stable hydrodynamic regime is established. The distribution function of the time of residence of the aqueous phase flow in the cascade is studied using the method of tracer pulse injection. The study confirms the possibility of operation of a cascade of mixing and settling extractors in the chromatography and liquid-membrane extraction modes.