Understanding the mechanism of permanganate ion rejection in TpPa-1/Ti3C2T2 composite membranes via molecular dynamic simulation

Abstract

The purification and separation of small molecules can be improved by fabricating different composite membranes, in this work, the TpPa-1/Ti3C2T2 composite membranes with different structural parameters and terminating functional groups were designed for better permanganate (PP) ions separation with non-equilibrium molecular dynamics simulations. The rejection mechanism was explored from molecular level. It is found that water flux is mainly influenced by the offset and interlayer spacing of Ti3C2T2, while the rejection rate of PP ion is affected more by the slit width of MXene. The combination of TpPa-1 and Ti3C2(OH)2 membrane provides a comfortable zone in for PP ion rejection from the viewpoint of thermodynamic. While the other two composite membranes constructed with terminating functional groups (-F, –O) in Ti3C2T2 show different rejection mechanism from that in TpPa-1/Ti3C2(OH)2 composite membrane. The rejection of PP ions mainly caused by the dynamic hindrance caused by water wall formed in the entrance of Ti3C2T2 (T = –F, –O) slits.