Liquid-liquid extraction process

Liquid-liquid extraction, also known as solvent extraction, is one of the important unit operations for separating liquid mixtures. In the liquid mixture to be separated, a kind of insoluble or partially miscible liquid rate extractor is added to form a two-phase system of liquid phase - extraction phase. The distribution difference of each component in the mixed liquid in the two phases is used to make some components more smoothly from the liquid phase of the liquid phase into the extraction phase, so as to achieve the operation of mixed liquid separation called liquid-liquid extraction.

In the extraction process, the solvent added is called the extraction agent. The component to be separated in the mixture is called economy. The extraction agent should have a large solubility of the solute, or the mouth and the solute to form a "extract" to achieve phase transfer. Other components of the liquid mixture should be immiscible or partially miscible with the extractant.

Usually, the extraction process is carried out at room temperature, and the extraction result is that the extraction agent extracts the solute into the extraction phase, and the liquid phase of the mixed liquid that separates the solute becomes the raffinate phase. The extraction phase is a mixture that needs to be separated by distillation or reverse extraction, etc., to obtain a solute containing product and extractant, and the extractant is used for recycling. This residual phase usually contains a small amount of base extractant, which needs to be recovered by an appropriate separation method.

When the liquid mixture is separated by the ratio method, the solute in the mixture can be either volatile substances, such as various organic substances, or non-volatile substances, such as inorganic salts. The extraction process itself has the advantages of normal temperature operation, no phase change and high separation factor can be obtained by choosing appropriate solvent, and in many cases it also shows technical and economic advantages.