Abstract
The synergistic extraction of gallium (III) with a mixed extractant of acidic organophosphorus compounds such as D2EHPA, DIDPA, and EHPNA as a main extractant and 5-chloro-8-hydroxyquinoline as a synergist diluted by toluene or n-heptane was examined at 298-323 K.
By adding 5-chloro-8-hydroxyquinoline to the EHPNA extraction system, a remarkable synergistic effect is observed, and the extractability of gallium from the aqueous to organic phases is increased by about 2300 times. However, in the synergistic extraction system of gallium with the mixed extractant, a precipitate was formed in the aqueous phase or at the aqueous-organic interface because of the low solubility of the metal-complex into the organic phase. To overcome this problem, 1-decanol was added to the extraction system as the modifier. The effect of addition of 1-decanol was quantitatively examined. As a result, variation in the extractability of gallium with addition of 1-decanol can be reasonably interpreted in terms of the decrease in the thermodynamic activity of EHPNA and the decrease in the distribution ability of 5-chloro-8-hydroxyquinoline.
