SURFACE-ACIDITY OF PILLARED TAENIOLITES IN TERMS OF THEIR PROTON AFFINITY DISTRIBUTIONS

Potentiometric titration data obtained for taeniolite samples pillared with hydroxyaluminum and hydroxyaluminum-zirconium polycations are an alyzed using a stable numerical method for the solution of the adsorpt ion integral equation. The samples studied were gradually heated befor e the experiment to impose changes in their acidic character. The acid ic properties of modified minerals are characterized by their pK spect ra. The relationship between these properties and the coordination and the chemical structure of cations in the pillaring species and the ch anges in the mineral layers due to heat treatment are discussed. The r esults obtained are also compared with the pK distributions for pure c ompounds used as pillars heated to the same temperatures as the pillar ed minerals. It is shown that heat treatment enhances the acidity of t he pillared taeniolites which may be the results of the rearrangement of pillars (dehydroxylation) and possible protonic attack on SiO4 tetr ahedra in the layers. The approach used enables one to assess both qua litatively and quantitatively the number and strength of acidic sites present on the surface of pillared taeniolites.