1. Field of the Invention
The present invention relates to a liquid-liquid extraction system for separation and purification of a solute.
2. Background Art
Liquid-liquid extraction is a method of separating and purifying a solute, with which a solute dissolved in one of a continuous phase and a dispersion phase that are mutually immiscible liquids is caused to migrate to the other phase. The liquid-liquid extraction involves, for the purpose of increasing the interfacial area between the continuous phase and the dispersion phase and thus improving the extraction efficiency, the three following steps: emulsification to produce droplets of the dispersion phase in the continuous phase, extraction to cause a solute dissolved in one of the two phases to migrate to the other phase, and separation to aggregate the droplets and separate the two phases of the continuous phase and the dispersion phase. In the currently used method (hereinafter referred to as a batch method), such three steps are performed using a separatory funnel. In the emulsification, liquids are shaken by hand, and in the extraction and separation, the emulsion is allowed to stand still.
Meanwhile, there is also known an emulsification/separation technique using ultrasonic irradiation, which is used for liquid-liquid extraction.
Liquid-liquid extraction using ultrasonic irradiation involves the use of two ultrasonic oscillation sources with different oscillation frequencies for use in emulsification and separation (hereinafter also referred to as an emulsification ultrasonic oscillation source and a separation ultrasonic oscillation source, respectively), two water tanks, below which the two ultrasonic oscillation sources are disposed, respectively, and a container adapted to contain a solution.
In the emulsification using ultrasonic irradiation, droplets of the dispersion phase, which have been produced by irradiating the continuous phase and the dispersion phase in the container with ultrasonic waves, are reduced in size by means of cavitation bubbles that have also been produced by the ultrasonic irradiation (for example, see Reference 1: JP Published Patent Application No. 04-293537 A (1992)).
Meanwhile, in the separation using ultrasonic irradiation, an aggregate of droplets, which have been produced on the nodes and antinodes of ultrasonic waves by irradiating the emulsion with ultrasonic waves, are separated into the two phases of the continuous phase and the dispersion phase by the difference in specific gravity upon termination of the ultrasonic irradiation (for example, see Reference 2: JP Published Patent Application No. 08-010509 A (1996) and Reference 3: JP Published Patent Application No. 2007-136271 A).