Thermal diffusion of ionic species in charged nanochannels

Diffusion of ions due to temperature gradients (known as thermal diffusion) in charged nanochannels is of interest in several engineering fields, including energy recovery and environmental protection. This paper presents a fundamental investigation of the thermal diffusion of sodium chloride in charged silica nanochannels performed by molecular dynamics (MD). The results reveal the effects of nanoconfinement and surface charges on the sign and magnitude of the Soret coefficient. It is shown that the sign and magnitude of the Soret coefficient are controlled by the structural modifications of the interfacial solutions. These modifications include the ionic solvation and hydrogen bond structure induced by the nanoconfinement and surface charges. The results show that both nanoconfinement and surface charges can make the solutions more thermophilic. Furthermore, the thermal diffusion of solutions in boundary layers is significantly different from that of solutions in bulk fluid, contributing to the overall difference between the thermal diffusivity of pore fluid and that associated with bulk fluid. The findings provide further understanding of thermal diffusion in nano-porous systems. The proposed MD simulation methodology is applicable to a wider category of coupled heat and mass transfer problems in nanoscale spaces.

Automated summary

This paper investigates the thermal diffusion of sodium chloride in charged silica nanochannels using molecular dynamics simulation. The results show that the nanoconfinement and surface charges affect the sign and magnitude of the Soret coefficient, with both factors making the solutions more thermophilic. Additionally, the thermal diffusion in boundary layers is different from that in bulk fluid, contributing to the overall difference in thermal diffusivity. These findings provide a better understanding of thermal diffusion in nano-porous systems and have implications for coupled heat and mass transfer problems in nanoscale spaces.