Formation of the Kaolin Structure Treated by Pressure

To form the technological properties of clays, various methods of their activation have been developed, the essence of which is that when processing clays, their structure (defectiveness) changes, which forms the energy potential of clay particles, and the latter is realized in the form of "specified" physicochemical properties of clays. In this regard, the effect of stress pressure on the change in the defectiveness of structural elements of kaolin was studied. Experimental studies showed that the pressure value P = 150 MPa was the boundary value at which different conditions for the formation of defectiveness of structural elements of kaolin were observed. High pressure has a multidirectional effect on the defectiveness formation of the kaolin structural elements: a package, a mineral, a colloid and an aggregate. In a package of kaolinite mineral, the defectiveness increases with increasing pressure. Defects are formed due to the removal of Al, Fe, Mg, Si ions from the octahedral and tetrahedral sheets. Al ions are the most sensitive to pressure. The removal of ions entails deformation of the packet and the formation of "hole" energy centers. Pressure up to 0–150 MPa has a greater effect on the formation of defectiveness (calculated correlation coefficient rс = 0.86) than in the range 150–800 MPa (rс = 0.82). In the kaolinite mineral at pressures up to 150 MPa, a decrease in defectiveness is observed due to the ordering of the structure under pressure (rс = 0.67). At pressures above 150 MPa, an increase in the defectiveness of the kaolinite mineral (rс = –0.72) is observed due to the destruction of hydrogen bonds between the packets, which entails the sliding and rotation of the structural packets among themselves. In a colloid (particle), with an increase in pressure to 150 MPa, the structural defect decreases due to an increase in the colloid density (rс = 0.67). In the pressure range of 150–800 MPa, it is rather difficult to reveal the effect of pressure on the formation of defectiveness (rс = 0.37). In the aggregate, with an increase in pressure to 150 MPa, the defectiveness of the structure increases due to crushing of particles, sliding and displacement of particles among themselves (rс = 0.95). In the pressure range of 150–800 MPa, it is rather difficult to reveal the influence of pressure on the formation of defectiveness (rс = 0.58), although the tendency increases with increasing pressure, the defectiveness of the aggregate remains.