Journal of Materials Research and Technology (Jul 2020)
Improved analysis methods to study the behavior of potassium ions in the interlayer of montmorillonite
Abstract
The behavior of potassium chloride (KCl) as a main mud shale inhibitor remains poorly defined in the interlayer of montmorillonite (Mt). In this paper, a new analysis method of transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) was established. The distribution of K+ in the interlayer of Mt and the processes surrounding d-spacing shifts in Mt were investigated through X-ray diffraction and TEM-EDS. The experimental results revealed shoulder peaks in the diffraction patterns at KCl concentrations between 11% and 19%. The distribution of K+ varied in the inner and outer layers of Mt with different KCl concentrations. It could be concluded that the distribution of K+ and the changes in d-spacing of Na are determined by two factors: negative charge sites and concentration difference. When the KCl concentration was below 8%, both factors cause the outer layer of Mt to adsorb more K+ than the inner layer, with all layers exhibiting d-spacings within the 1.50 nm state. At an 8% KCl concentration, all negative charge sites were occupied by K+. As the KCl concentration rose above 8%, the outer layer of Mt adsorbed more K+ than the inner layer due to the concentration difference. With a further increase in the KCl concentration, the d-spacing shifted linearly to 1.30 nm from the outer to the inner layer of Mt. All layers of Mt exhibited a d-spacing of 1.30 nm at KCl concentrations of up to 23%. These results demonstrate the benefits and capabilities of the proposed method in investigating the intercalating mechanisms of Mt.