Mechanism research on surface hydration of Fe(II)-doped kaolinite, insights from molecular dynamics simulations

Abstract

To investigate the micro-influence mechanism of Fe(II) doping on the surface hydration of kaolinite, molecular dynamics (MD) simulation method was utilized to simulate the interaction between H2O and Fe(II)-doped kaolinite (referred to as Fe(II)-Kao) surface under different conditions. Results demonstrate that the H2O can be adsorbed on Fe(II)-Kao surfaces, forming a hydration film composed of three H2O layers with a thickness of 8–10 Å. As the thickness of the H2O layer increased on Fe(II)-Kao surfaces, the interfacial effect between H2O and the surface gradually weakened. Furthermore, the interaction between H2O and Fe(II)-Kao (001¯) surface is weaker compared to that on the Fe(II)-Kao (001) surface. Additionally, the presence of Fe(II) doping enhanced the hydration of the kaolinite surface. The micro-influence mechanism of Fe(II) doping on the surface hydration of kaolinite can be attributed to the enhancement of the interface effect between equilibrium cations (such as Na(I)) and the surface, resulting in an increased ion hydration at the kaolinite surface. Overall, Fe(II) doping tends to promote the surface hydration of kaolinite. The elucidated mechanism of how impurity defects affect the surface hydration activity of kaolinite can provide theoretical support for tailings separation and wastewater treatment.