The nature of extractant directly affects the extraction effect and extraction cost. When selecting extractant, the following factors should be considered:

(1) Large extraction capacity, i.e. large partition coefficient;

(2) Physical properties of extractant:

① Density; ② Moderate interfacial tension; ③ Viscosity;

(3) It has good chemical stability, fire and explosion resistance, low toxicity, low corrosivity, high flash point, low freezing point and low steam pressure, which is convenient for storage and use at room temperature.

(4) The source is wide and the price is cheap.

(5) Easy to regenerate and recover solvent.