Nanoscale Water-salt Permeation And Wetting Simulation Study Of Clay Minerals

Earth and rock dams occupy an important position in China’s water conservancy projects.They are widely distributed and numerous in China,serving important functions such as flood control,power generation,shipping,irrigation,and reduction of droughts and floods.Among the many safety accidents of earth and rock dams,those caused by pipe surges and seepage account for a relatively large proportion,and clay minerals mainly assume the role of seepage control in the safe operation of earth and rock dams,so this paper discusses the phenomenon of clay minerals in different water environments.Clay minerals affect the service life of earth and rock dams to a certain extent.The macroscopic experimental studies on the water retention capacity and hydrophobicity of clay minerals have been relatively exhaustive,and less research has been conducted under their microscopic perspective,but they have been gaining more and more attention in the past decade and have become a popular angle in clay research.Previously,the single contact surface of a single clay has been explored,but the comparison between different contact surfaces of multiple clay minerals is seldom mentioned,and the saturated and unsaturated pore channels of clay mineral nanogels,which are closer to reality,have been studied.In this paper,a microscopic perspective is chosen to investigate the properties and reactions between water molecules and ions in clay minerals,based on molecular dynamics theory,to explore the wetting of water droplets on substrates with different contact surfaces of clay minerals;to explore the effects of water molecules and ions on the clay in the presence of saturated transport in the nanogel pores of clay minerals and persistence;to explore the process of sodium chloride solution intrusion into the pore channels of clay mineral nanogels under unsaturated condition and to compare the similarities and differences of the intrusion process under different pore sizes.For the above study,the main research process and conclusions are as follows:For the wetting models of different interfaces of different clays,illite,kaolinite and chlorite,were selected for different interfaces.By analyzing the water molecule density distribution and contact angle variation in the wetting model simulation,it was found that all three clays exhibited hydrophilicity.Chlorite is more hydrophilic than illite is stronger than kaolinite.The different contact surfaces of the same clay have slightly different water attraction effects.For the transport phenomena of water and ions within the pore channels of saturated clay mineral gels,the analysis of hydrogen and oxygen atoms in water molecules,ion density distribution,and radial distribution functions reveals that water has a multi-peak distribution within the channels,indicating a layered stacking structure of water molecules.The high peak values presented on different clay surfaces also prove that the material is hydrophilic.In addition,anions and cations tend to form easily on the surface of clay minerals and form ionic bonds.The effect of ions varies from interface to interface.In addition,the data collection and analysis of the mean square displacement revealed that the water molecules possess higher mean square displacement values,indicating that the water molecules are more active in the saturated channels,which also confirms that the anions and cations are more susceptible to Coulomb forces to adsorb on the channel surfaces to slow down their movement rates.For the phenomenon of water and ion transport in the gel pores of unsaturated clay minerals,by comparing the changes of water molecule strength during the intrusion of three clays,it is found that there is a greater chlorite intrusion rate than illite intrusion rate than kaolinite intrusion rate between the nano-gel pore channels of three clay minerals,which is also proportional to the order of the strength of hydrophilicity of the three clay minerals to the wetting experiment.During the transport of water molecules and ions in the pore channels of the clay nanogels,the front interface surfaces of the three clays showed a meniscus shape,and the overall intrusion process showed a parabolic shape,which is also in good agreement with the classical LW equation theory.In addition,through the analysis for the mean square displacement,it can be observed that there is a gap between the transport efficiency of water molecules and sodium and chloride ions,and the overall offset rate of water molecules is slightly faster than that of sodium and chloride ions,which indicates that the clay mineral surface has a certain adsorption effect on the anion and yang in water during the process of erosion.In the study of clay minerals with different pore sizes,it was found that the smaller the pore size,the lower the transport efficiency of sodium chloride solution within the pore channel,and the ions tend to form aggregated clusters at the entrance of the pore channel,thus hindering the water transport efficiency,and this conclusion is also consistent with the macroscopic experiments.These laws are beneficial to further reveal the wetting of clay mineral materials and the process of water and ion infiltration and erosion,and develop more properties of them.