In this study, we focused on the presentation of clay minerals, their conditions of formation and their different categories. We also reported the importance of purification in removing impurities and the responses induced by heat treatment of these minerals. Techniques used to detect clay minerals are also exposed. On the other hand, the mineralogical, physicochemical and thermal properties have a direct impact on the field of use of these minerals. These properties differ from one mineral to another, depending on the structure and chemical composition. Moreover, the remarkable properties of smectites make these minerals the most preferred for the industry and also in the environmental field. Due to their brilliant firing properties, illites are suitable for the construction industry. Moreover, the purification by acids (acetic acid and HCl) allows the removal of most associated minerals, and thus a secure access to the clays' characteristics and a very strong sensitization even to the small variation. Finally, the ethylene glycol (EG) swelling test only affects the basal distance of smectites, increasing this distance to 17 Å, but heating to 500°C destroys kaolinite, and closes the basal distance of smectites and vermiculites to 10 Å. Illites and chlorites show no response to these two treatments (EG, heating to 500°C).
Adsorption of polymers is a phenomenon of great importance in a number of areas of our daily life. However, understanding this phenomenon is essential. This work focuses on the theoretical study of the polyethylene glycol (PEG) adsorption phenomenon on thenatural clay-layer surface. Clay is considered as a matrix. Different adsorption regimes have been presented. The expressions of the surface coverage ratio as a function of the volume fraction of monomer for each regime were calculated. A strong adsorption was noted for the first two regimes (dilute surface, and bidimensional semi-dilute surface) confirmed by the exponential term. When the surface becomes saturated, we are in the plateau regime for which the adsorption varies logarithmically, due to the occupation of most of the sites available on the clay-layer surface. Finally, we presented the variation of the volume fraction as a function of 𝑧(axis perpendicular to the surface), we have shown that a layer of polyethylene glycol (PEG) adsorbed on a natural clay-layer surface is composed of three zones (proximal, central and distal) with different volume fractions.
The intercalation of polyethylene glycol (PEG) chains, in the inter-layer environment of the clay from Meknes, was performed using the direct intercalation method in the presence of water as a solvent. X-ray diffraction (XRD) technique was applied to follow the evolution of interlayer distances as a function of PEG bulk volume fraction. The XRD data assert the formation of an intercalated structure through the displacement of the peaks, which characterize the clay minerals towards the small and large angles. The evolution of the d001-spacing for the three classes of clays was similar. Indeed, as φ increases, the d001 variation is marked by two depletion phenomena due to the magnitude of the gyration radius compared to the inter-layer distance of the clay minerals. The plateau regime, characterized by the weak insertion of the chains, appears after each depletion/expansion cycle, which reveals a succession of the depletion-adsorption-plateau phenomenon. Based on the results of the XRD method, we proposed a model for the insertion of PEG chains in monolayer and bilayer forms into the interlayer environment of clay minerals. Finally, the scaling theory reveals a good agreement with the experimental findings and perfectly illustrates the succession of three regimes: dilute, bidimensional semi-dilute, and plateau.
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