Comparison of Titration Methods Used in Characterization of Bentonite

Abstract

Titration of bentonite, or clay materials in general, can be carried out in two ways, namely by semi-continuous method and batch method. This study compares these two methods, and, in addition, presents the results of two different evaluation and regression procedures used for fitting of experimental titration curves and for calculation of corresponding parameters. Bentonites B75 and S65, and montmorillonite SAz-1, were chosen for this study. Regarding the semi-continuous method, the technique developed by Wanner et al. was used. As for the batch method, two-week contact time for selected solid/liquid ratio 1 g per 250 ml was used on the base of preliminary experiments. The evaluation of result obtained using the batch method with back titration correction gave more relevant data, on the other hand, with the use of this method is connected a risk of solid phase dissolution. The chemical equilibrium model (i.e. non-electrostatic), incorporated into codes (I) PHREEQC + UCODE_2005, and (II) PDNLRG.fm (code package STAMB) + software FAMULUS, was used to the evaluation of the titration curves. The codes mentioned give only slightly different resulting values in the case of batch method.