2002 Volume 70 Issue 7 Pages 530-535
Tetratitanic acid, H2Ti4O9·H2O, has a layer structure composed of the TiO6 octahedra sheets containing two protons and one water molecule per tetratitanate unit. The protons are exchanged with cations in bulk solution, and the amount of alkali metal ions incorporated into the interlayer was measured as a function of pH. With increasing pH, the amount increased, but the effect of pH on the extent of incorporation was far smaller than that expected from the mass action law. This behavior was modeled with the Frumkin equation where suppressive interactions between adsorbed ions owing to either electrostatic repulsion or steric hindrance are taken into account. The measured data were fitted with the model equation and the ion adsorption abilities of tetratitanic acid, adsorption affinities of sodium and potassium ions, and suppressive interaction properties of adsorbed ions were evaluated with model parameters. The molecular form of the exchanging protons and the mechanism of exchange with cations are discussed.