The hydration effect of singly charged ions on the electrosurface properties of titanium dioxide aqueous suspensions

Abstract The effect of ordering/disordering degree of water molecules in the vicinity of singly charged cations (Li+, Na+, K+, Rb+, Cs+) and anions (F-, Cl-, Br-, I-) on the electrosurface properties of aqueous suspensions of rutile-type titanium dioxide is discussed. The influence of mentioned ions presence on the position of the isoelectric point, which is one of the integral estimates of the suspensions electrosurface properties was examined. It was accepted that displacement of the isoelectric point is caused by different binding of cations and anions to the titanium dioxide surface. The magnitude of this displacement estimates the relative binding of cations and anions to the surface, which depends on the ordering/disordering degree of water molecules. The dependences were found to have a maximum and a minimum in the case of cations and anions, respectively. The extreme values were determined when the water molecules structure in the vicinity of ions was undisturbed and corresponded to the structure of bulk water. The results obtained are relevant for highly dispersed systems, for which it is important to maintain a stable electrolyte balance and to avoid a significant redistribution of ions between their bulk and surface parts.