Simulation Study On Sodium-montmorillonite Hydration

Montmorillonite is a layered swelling clay mineral that has the ability to uptake and release water and chemical species,and to exchange its structural cations.These properties are benefit in various fields including the study of catalysis,soil mechanics,agronomy,ecology,waste management,drug,borehole stability.Minimize clay swelling is a goal of large amount of interest from the academia to the industry.In order to understand and minimize the swelling of Clay minerals,knowledge on Na-montmorillonite?Na-MMT?structure,physical and chemical characteristics and swelling inhibitors are necessary.This study was based on the investigation of the swelling properties of Na-MMT and the impact of the use of inorganic salts on its stability while swelling.Molecular modeling software Material Studio 5.0 was used to build a crystal model,analyze the hydration process and mechanism of Na-MMT.The simulation results showed that the basal spacing of Na-MMT gradually increased with the increase in the adsorbed water molecules between the interlayer spaces.One,two and three water layers were formed when the amount of water molecules reached 48,72,128.Visual studio software was used to calculate the hydration parameters of the cations present into layer spaces.The results obtained from the dynamics simulation at HTHP have shown that,the effects of the hydration degree,the temperature and pressure are more important on the diffusion of water molecules than the cations,and that,the hydration degree of Na-MMT depends on the type of cations present between the layers.We have also found that,the size,the mass of the cations hydrated affect the diffusion behaviors of the interlayer species,and also that the hydration energy of the interlayer cations does not depend on the hydration degree and the change in temperature and pressure.Through the study of the thermodynamics parameters of Na-MMT after addition of inorganic salts,we observed that,the state of Na-MMT became more stable with the addition of KCl,CaCl₂ and NaCl respectively.This study had a good idea for understanding the impact of the rise of temperature and pressure on the properties of Na-MMT hydrated when inorganic salts were added so that efficient swelling inhibitors may be developed.