SOLVENT-EXTRACTION OF TITANIUM(IV) FROM NITRIC-ACID SOLUTION BY DI(2-ETHYLHEXYL)PHOSPHORIC ACID

The extraction equilibrium of Ti(IV) was studied between aqueous nitric acid solutions (0.1-6M) and n-heptane solutions of di(2-ethylhexyl)phosphoric acid. The kinetics of the extraction and stripping reaction was also examined in a dispersion system using a stirred vessel. With increasing the acid concentration, the distribution ratio of Ti(IV) decreases and goes through a minimum. It was shown that the extraction of Ti(IV) from low acidic media in the concentration range 0.1-2M is a cation exchange reaction. For the higher acid solutions, the equilibrium distribution increases with the concentration of nitrate as well as nitric acid. This suggests that the extraction takes place by solvation reaction at high acidities. Furthermore, rate equations of the Ti(IV) extraction were obtained for the forward and backward reactions of the cation exchange. It was shown that a good agreement exists between the extraction constants from the equilibrium data and the two rate equations.