Solvent extraction of La(III) with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (EHEHPA) by membrane dispersion micro-extractor

The conventional rare earth solvent extraction equipments have many problems such as long mixing time, low processing capacity, large factory area occupation, high energy consumption and so on. In order to solve the problems, many types of equipments were brought out. In this work, studies were carried out on the La(III) extraction process with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (EHEHPA) by membrane dispersion micro-extractor. Equilibrium studies showed that the initial aqueous pH value 4.15 with the saponification rate 40% was the optimal operation condition. The effects of membrane dispersion micro-extractor operational conditions such as dispersion mode, bulk flow rate and organic phase flow rate on the extraction efficiency were studied. The results showed that when the organic solution was the dispersed phase, the extraction efficiency was higher than that of others. Increasing bulk flow ratio could enhance the extraction efficiency greatly. When the ratio of organic phase flow rate to that of aqueous phase was 80:80, the extraction efficiency was over 95%. The effect of stripping phase acidity on the La(III) recovery was studied. The results showed that when the stripping phase pH was 2.0, organic phase flow rate to stripping phase flow rate was 20:80; the recovery efficiency of La(III) can reach 82%.