Cation Exchange Properties of Tetratitanic Acid with Interlayer Protons and of Titania with Surface Hydroxyl Protons*

Cation exchange properties of tetratitanic acid with interlayer protons were measured and compared to those of titania with surface hydroxyl protons using the Frumkin equation. Tetratitanic acid showed larger ion-exchange capacity and much higher activity than titania. The characteristics of exchangeable protons and intercalated cations are discussed to explain the different ion-exchange properties. The interlayer protons of tetratitanic acid can be regarded as acid functional groups of an oxoacid of Ti, and acid functional groups dissociate much more easily than the surface hydroxyl groups on titania that are formed by hydration. The cations intercalated into tetratitanate are sandwiched between opposing titanate layers with negative charges and are better stabilized than the cations adsorbed on the outer surfaces of titania owing to better neutralization of cationic charges.