Mechanisms of Mg2+/Li+ separation regulated by ion dynamics near the entrance of 2D nanochannels under applied electric fields

Abstract

Molecular dynamics simulations were employed to investigate the separation mechanism of Mg2+/Li+ by 2D nanochannels under applied electric fields. The results show that the differences between the Mg2+-Cl− and Li+-Cl− association characteristics both inside nanochannels and near the entrance of nanochannels under an electric field are decisive factors for the selective transport of ions by the 2D nanochannel with a large interlayer spacing, especially near the entrance of the nanochannel. At the entrance, Li+ ions are more susceptible to interaction with Cl− and are relatively slowed under weak electric fields while Mg2+ ions are less affected. The Li+-Cl− association near the entrance of the nanochannel is enhanced by the synergistic effect of the ion migration dynamics inside the nanochannel and in the bulk phase. Due to the ion association characteristics, excellent separation efficiency of Mg2+/Li+ can be obtained under a weaker electric field by the nanochannel with a large spacing.