Relation between physico-chemical characteristics of a bentonite and its adsorptive capacity

Abstract

Bentonites are clays essentially used for musts and wines protein haze prevention. For the « Methode Champenoise », they also serve as a riddling adjuvant to facilitate yeasts elimination. Physico-chemical characteristics of various types of bentonites are studied in parallel to their adsoiption properties. Na/Ca exchangeable ratio is contained between 0.5 and 3.7. Swelling indexes measured in wine or in drinking water (r = 0.96) are not related to the Na/Ca ratio. On the other hand, a good correlation exists between the specifie adsorption surface (measured with methylene blue test), the BSA or the wines proteins adsorption capacity and the Na/Ca ratio. Otherwise, all of the three tests provide more or less identical informations. For Champagne base wine, the adsorption phenomenon follows the LANGMUIR's equation. Additionnaly, it is shown that the maximum adsorbable protein content by unit of adsorbing material increases with the Na/Ca ratio. All enologic products analysed by X-rays contain montmorillonite with variable percentage. Some products contain an important proportion ofkaolinite or illite. However, there is no correlation between mineral compositions and adsorption capacities ofthe studied bentonites.