Modeling potentiometric titration behavior of glauconite

Modeling description and spectroscopic evidence of surface acid–base properties of natural illites

“…As indicated by Lu and Smith (1996), the titration behavior of complex minerals may not be simply represented by an oxide mixture with compositional equivalence. In fact, surface complexation model parameters acquired during a particular fitting procedure are not necessarily unique.…”

“…Some papers have shown that dissolution of solid substrate, as well as the subsequent surface complexation or precipitation, exerted an effect upon the surface acid-base behaviors of clay minerals, especially on the quantitative evaluation of proton consumption using the back titration data (Lu and Smith, 1996). Consequently, the critical interactions between soluble aluminum species and silicic acid, originated from substrate dissolution, should not be neglected.…”

A Comparative Study of Surface Acid–Base Characteristics of Natural Illites from Different Origins

“…(1) Proton reactions in the acidimetric supernatant of illite suspensions can be successfully described by those of Al 3ϩ and Si(OH) 4 in aqueous solution, together with the complex formation of hydroxyaluminosilicate (HAS) species. Since a significant release of illite structural elements occurs during the potentiometric titration, it is more reasonable to regard the acidimetric supernatant as the system blank when evaluating the surface site concentration (H S ).…”

“…System blank. The corresponding acidity constants of Al 3ϩ and Si(OH) 4 in aqueous solution (41) are summarized in Table 2. In this study, the proton reactions in the illite suspension supernatants were described by those of Si(OH) 4 and Al 3ϩ in aqueous solution, similar to the previous paper (20), since natural illite is mainly composed of hydrous aluminosilicate.…”

“…In order to formulate these reactions, a set of parameters were imported into the stoichiometric matrix, including the acidity constants of Al 3ϩ and Si(OH) 4 in aqueous solution and the ICP-OES measurements of TOT(Si) and TOT(Al) in the acidimetric supernatant, as well as the relevant reactions of Al-Si complex formation, occurring in aqueous solution and at the illite surface sites. Then, two surface proton-reaction models were established to obtain the surface acidity constants, optimization being accomplished by tuning the corresponding parameters in the least-squares program FITEQL, including the electrical capacitance (C), until the best fit was achieved.…”