Experimental Characterizations and Swelling Studies of Natural and Activated Bentonites with Their Commercial Applications

Abstract

Bentonites contain a large amount of nano-porous and nano-structured montmorillonite, which is the dominant clay mineral determining the swelling properties of bentonites. In this study, bentonites are categorized into three types, namely swelling (Na-montmorillonite), nonswelling-swelling (Ca,Na-montmorillonite), and nonswelling (Ca-montmorillonite). Soda activation with the optimum parameters also increases the swelling properties of bentonites. The instrumental and experimental analyses for specifying bentonite for each application include pH, Methylene Blue (M.B.) test, Cation Exchange Capacity (C.E.C.) measurements; Swell, M.B., sediment, and colloid indices, dry screen analysis (granulometric analysis), XRD (X-ray diffraction), XRF (X-ray fluorescence). pH results showed higher values for swelling bentonites (group 3) and these values increased after soda activation. The values of C.E.C., M.B. test, and indices are normally higher for group 3 than for group 2 (nonswelling-swelling type). These values were directly related with the amount of clay minerals (montmorillonites) in dry screen analysis. Finally, swelling and non-swelling effects on bentonite particles play an important role in their applications. Swelling bentonites like ES3 are good for applications such as barriers, drilling mud, and plethorapy. Group 2 (nonswelling-swelling) such as S2, G1, and GH1 are good bentonites for use as a filtering agent in juice industries due to being lower voluminous material than that of production with group 3. For pharmaceutical applications, in addition to the swelling index, sediment and colloid indices must be considered.