Solvent extraction performance of Pr (III) from chloride acidic solution with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (EHEHPA) by using membrane dispersion micro-extractor

• For the first time, Pr(III) solvent extraction experiments by using membrane dispersion micro-extractor were carried out.
• The dispersed droplets were evaluated by a photo imaging system.
• At optimal conditions, the extraction efficiency can reach almost 100% in 2 s.
• By considering the mass transfer resistance, the mass transfer mechanism was revealed.

In order to recover the rare earth elements from the diluted source, a membrane dispersion micro-extractor was used to extract the Pr (III) in chloride acidic solution. The saponified 2-ethylhexyl phosphoric acid-2-ethylhexyl ester was used as extractant. Firstly, the dispersion of droplets was analyzed by using a photo imaging system. The results showed that Sauter diameter of the droplets increased with the growth of the aqueous acidity due to a high interfacial tension. However, a fixed phase ratio of 1:1 with a total flow rate increasing reduced the droplet diameter significantly. Secondly, the effects of the concentration of the extractant, aqueous pH, and total flow rate on the praseodymium extraction were analyzed. At optimal conditions, the extraction efficiency reached almost 100% in 2 s. Thirdly, by evaluating the mass transfer resistance, the overall mass transfer process was controlled by reaction process as the total flow rate over 80 mL/min and by mass transfer in organic phase as the total flow rate less than 80 mL/min. Finally, by using the membrane dispersion micro-extractor, a 90% stripping efficiency was reached in less than 4 s as acidity of stripping phase was more than 0.5 M.

Membrane dispersion micro-extractor setup. The dispersed phase and the continuous phase are pumped into a membrane micro-dispersive module where the dispersed phase is pressed to pass through the membrane dispersion medium. Many small droplets are formed in the continuous phase. The mixture phase is immersed into a water bath to control the extraction temperature. After phase separation, the concentration of Pr (III) in the raffinate is determined by ICP.Figure optionsDownload as PowerPoint slide