Surface acidity of pyrophyllite and talc

TLDR: For example, this article showed that water molecules previously adsorbed on the surface of pyrophyllite and talc decreased both the strength and amount of acid sites, although the degrees of the decrease were smaller.

Abstract: Pyrophyllite and talc were shown to have acid sites on their surface, and the strength and amount of the acidity were much higher for pyrophyllite than talc. The strength and amount of the acidity of both minerals were not affected by the exchangeable cation species. Water molecules previously adsorbed on the surface of the minerals lowered both the strength and amount of the acid sites, although the degrees of the decrease were smaller than the case of montmorillonite. When the water was introduced after the adsorption of indicators, the water molecules did not affect voth the strength the amount of the acidity