Principle of solvent extraction

Solvent extraction is a method to dissolve the effective components in Chinese herbal medicine tissues by selecting solvents with high solubility for active components and low solubility for unnecessary components according to the solubility characteristics of various components in solvents.

When solvent is added to Chinese herbal medicine raw materials, the solvent gradually penetrates into cells through the cell wall due to diffusion and osmosis, dissolving soluble substances, resulting in the concentration difference inside and outside the cells, so the concentrated solution in the cells continues to spread outward.

The solvent continuously enters the drug tissue cells, and so on and so forth for many times until the concentration of solution inside and outside the cells reaches a dynamic balance, the saturated solution is filtered out, and new solvent is continuously added for many times, so that the required components are nearly completely dissolved or mostly dissolved.

Solvent extraction method is also called liquid extraction method, which is called extraction method for short. In the extraction method, the organic phase and the water phase are mixed with each other. After the substances to be separated from the water phase enter the organic phase, the two phases are separated by their different mass densities. The organic phase is generally composed of three substances, namely extractant, diluent and solvent.

Sometimes some regulators are added to the extractant to make the performance of the extractant better. Usually, high molecular organic amine, such as trialkylmethylamine chloride (N263), high carbon alcohol as diluent and sulfonated kerosene as solvent are used to extract non-ferrous metal cyanide complex from cyanide solution. The water phase is wastewater to be treated.