Formation mechanism of micro emulsion on aluminum and lanthanum extraction in P507-HCl system

P507 solvent extraction is the main method to separate and purify the rare earth products. The emulsification may be caused by the impurities in process of extracting rare earths, and these result in huge economic loss and decrease the quality of rare earth products. In recent researches, the extractant was prone to emulsification, and aluminum content of rare earth products also increased, while aluminum concentration of feed was higher. Pointing to this problem, the structural change of saponification P507 extracting aluminum and lanthanum was investigated by infrared spectroscopy, and the results showed that Al ions exchanged with H of P-O-H to become P-O-Al. Because aluminum held the characteristic of hydrophilic after extracted in the form of hydroxyl polymer ions and this provided conditions for the formation of micro emulsion. The organic phase and aqueous phase were investigated by polarizing microscope after aluminum was extracted. The results showed that the organic phase was clear when the extraction capacity of Al was less than 5 g/L. If the extraction capacity of Al exceeded 5 g/L, it formed W/O of ME (micro emulsion), leading to form emulsion of the organic phase. When Al concentration of feed was less than 1 g/L, the aqueous phase would form O/W of ME. If aluminum was extracted by saponification P507 firstly, then the the organic phase loading aluminum extracted rare earth continually, the organic and aqueous phase formed emulsification easily.