The solvent extraction of alkali metal tetraphenylborates

Abstract

The extraction of sodium and small amounts of potassium, rubidium and cesium from aqueous solutions containing sodium tetraphenylborate (TPB), sodium perchlorate and perchloric acid has been studied for nitromethane, nitroethane, nitrobenzene, methyl isobutyl ketone and tributyl phosphate. Nitromethane gives the highest distribution ratio (org/aq) for the perchlorates, and nitrobenzene gives the highest distribution ratio and separation factor for the tetraphenylborates. Most distribution data could be explained by assuming that the tetraphenylborates were fully dissociated in both phases. The equilibrium constants and distribution ratios increase in the order sodium<potassium<rubidium<cesium. The distribution ratio of small amounts of the heavy alkali metal ions will thus not be appreciably influenced by the concentration of sodium tetraphenylborate, but will decrease on the addition of sodium chloride or perchlorate. The effect of perchloric acid can be explained by irreversible acid hydrolysis of the tetraphenylborate ion.