The interaction between bentonite and water vapor [thesis]

Michel Heuser, Helge Stanjek, Ralf Diedel
The influence of water vapor on bentonites or smectites, respectively, is of interest in many different fields of applied mineralogy like nuclear waste sealing or casting in foundry industry. The water vapor affects the smectite surface and perhaps its structure, which leads probably to achange of its properties in a mostly unfavorable way. Therefore, the influence of hot water vapor (200 ℃) on the physico-chemical, mineralogical, and electrokinetic parameters and properties of smectite-group
more » ... nerals has been studied. After the steam treatment, turbidity measurements, methylene blue sorption, water adsorption, and cation exchange capacity were measured on both untreated and treated samples. Mineralogical changes were checked by X-ray diffraction (XRD), X-ray photon spectroscopy (XPS) was done on O, Al, and Si, respectively. Only few parameters showed differences between vapor-treated and raw samples. The measurement of sedimentation volumes (SV) resulted in a decreased SV after the treatment. As shown by XRD and XPS, the crystalline structure of smectite remained unaffected by the steam treatment. Equivalent sphere diameters (ESD) were not systematically affected by the steam treatment. Differences in cation exchange capacity (CEC) between unprocessed and treated samples were observed, but only for smectites with monovalent interlayer cations. From the variety of different measurements and its results, the conclusion is that due to thesteam treatment the charge properties at or near the particle surface of smectite change. While most of physico-chemical and mineralogical properties remained unaffected by watervapor, electrokinetic, rheological, and surface properties react due to exposure of smectite to hotwater vapor. The first physico-chemical and mineralogical experiments suggested that monovalent smectitesoffered changes after steaming, whereas the divalent smectites remained unaffected. This statement is partially true in terms of the experiments of this work. As well the magnitude of the dynamic mobility and isoconductiv [...]
doi:10.18154/rwth-2018-222396 fatcat:q74pfwyi7jge3gqb3hwm3x57ba