A simulation of methane hydrate formation in nickel chloride solution

Heavy metal is a potential threat to human, and hydrate-based method was one potential method proposed for heavy metal removal. In order to get a better understanding of the mechanism for heavy metal removal by hydrate-based method, simulation of methane (CH4) hydrate formation in nickel chloride (NiCl2) solution was conducted from molecular level by using Gromacs-2020.3 software. From the simulation results, CH4 hydrate formed in NiCl2 solution can be judged from the increasing of four-body structural order parameters (F4) and the decreasing of total energy. Hydrate or interfacial hydrate rather than ice was the main solid structure via CHILL + Algorithm analysis. All nickel chloride was repelled out of CH4 hydrate during 2000 ns of simulation, which corresponded with the salt-removing effect. The simulation results also indicated that chloride ion accelerated the nucleation of CH4 hydrate no matter the cation was Na+ or Ni2+. Finally, CH4 hydrate with both Structure I (sI) and Structure II (sII) were formed in NiCl2 solution in 2000 ns of simulation, and sI type hydrate was the main CH4 hydrate structure in NiCl2 solution.

Automated summary

Heavy metal is a potential threat to human, and hydrate-based method was one possible approach for its removal. Molecular simulation using Gromacs-2020.3 software was conducted to investigate the mechanism of heavy metal removal by hydrate-based method. The simulation results showed that CH4 hydrate formed in NiCl2 solution, and the main solid structure was hydrate or interfacial hydrate. All nickel chloride was repelled out of CH4 hydrate during the simulation, indicating the salt-removing effect. Furthermore, the simulation results revealed that chloride ion promoted the nucleation of CH4 hydrate regardless of the cation being Na+ or Ni2+. In addition, both Structure I (sI) and Structure II (sII) CH4 hydrates were formed in NiCl2 solution, with sI type hydrate being the predominant structure.