Molecular Insights into the Influence of Major Marine Ions on Carbon Dioxide Hydrate Growth

Effective management of gas hydrate formation and decomposition is essential for the development and utilization of gas hydrate and related technologies, which requires a detailed interpretation of the physical and chemical processes and mechanisms involved. However, the molecular-level details of gas hydrate formation in a saline solution are still unclear. Here, by taking advantage of molecular simulations in studying microscopic mechanisms, we examined the effect of major marine ions on the growth of CO2 hydrate at various temperatures and 5 MPa. Our results indicate that all salt ions can inhibit the formation of gas hydrate; however, the entry of ions into the hydrate phase and their inhibitory effect on hydrate growth exhibit variability. Although certain ions can enter the hydrate phase due to their hydration structure similarity to that of the hydrate structure, the impact of ions on hydrate growth is not directly related to the ion concentration in the hydrate phase. Indeed, it depends on the strength and structure of the hydration shell of ions, that is, the hydration free energy of ions and the hydration structure. Moreover, simulations conducted at varied temperatures indicate that the ion’s inhibitory effect on hydrate growth increases slightly with increasing temperature. This study advances our understanding of the processes involved in gas hydrate formation in saline water, which is useful for developing and applying gas hydrate technology, specifically for seawater desalination and seafloor carbon sequestration through hydrates.