Regularities of zero charge formation on the surface of clay particles exposed to pressure

Abstract

Relevance. Caused by the need to study the effect of high pressure on the change in pH value of the point of zero charge of clay minerals. The point of zero charge is one of the most important characteristics of a diluent. The magnitude of the charge is largely controlled by the pH values of a pore solution. As it is known, clays of different genesis have excellent physical and chemical properties, which directly affects the value of the zero charge point. Aim. To identify the patterns of formation of the zero charge point of clay particles exposed to pressure. Objects. Kaolin clay of the Nizhne-Uvelsky deposit of the Chelyabinsk region and bentonite clay of the Zyryanovsky deposit of the Kurgan region. Methods. potentiometric titration, determination of the point of zero charge was carried out using the construction of potentiometric titration curves. Microsoft Excel, SigmaPlot, Statistica software was used. Results. When processing clays by pressure, there is a decrease in the content of aluminum ions (Al3+) in the packages of kaolinite and montmorillonite, the transition of Al3+ ions into the diffuse layer of the clay particle, where aluminum ions bind hydroxyl ions, while the released hydrogen ions increase the acidity of the suspension. Activation by pressure of kaolin and bentonite clays has a multidirectional effect on the change in the ion-exchange capacity of clays and, as a result, on the pH of the point of zero charge on the surface of clay particles. The authors developed statistical models that allow predicting the pH of the zero charge point from clay activation pressure data. Knowledge of the characteristics of the charge on the surface of clay particles makes it possible to explain the mechanism of sorption and other processes.