Acid-base properties of a river sediment: applicability of potentiometric titrations

The application of potentiometric titrations to the study of the acid-base properties of a river sediment was investigated. A set of alkalimetric titrations were performed on suspensions containing different sediment-solution ratios and EMF measurements were elaborated by a suitable computer program. After the optimisation of the titration procedure, it was possible to refine conditional acid constants. For the considered sediment it was possible to calculate three protonation constants. Comparing calculated pKa with those reported in literature for the characterisation of humic and fulvic material of various origins and for inorganic hydrous oxides, it appears that calculated values are in the range indicated for the assignment of the constants to organic and inorganic titratable groups that can be present on the surface of a natural sediment.