Effect of Both the Phase Composition and Modification Methods on Structural-Adsorption Parameters of Dispersed Silicas

Abstract

Tripoli from two Ukrainian deposits was studied in its natural and modified forms. The investigation of natural and modified tripoli involves the identification of their phase compositions through X-ray diffraction and the analysis of their water vapor adsorption-desorption isotherms. The obtained results are evidence of changes in the structural-adsorption parameters of tripoli as a result of modification. Their treatment in boiling water or acid causes apparent alterations of contents of the main phases and sizes of their crystallites, whereas their calcination causes not only the dehydroxylation of surfaces and the agglomeration of phases, but even phase transformation in the case of carbonate tripoli. After analyzing water vapor adsorption-desorption isotherms of natural and modified tripolis, some correlations between their adsorption parameters, phase compositions, main phase contents and crystallite sizes have been found.