The performance of a C2N membrane for heavy metal ions removal from water under external electric field

• The atomic-level simulation increases the understanding of electric field effects on ion separation. • Electrodialysis is an emerging method for heavy metal removal. • The monolayer C 2 N membrane possesses high ion permeability due to its high pore density. • The C 2 N nanosheet possesses excellent ion selectivity under a low electric field due to the distinct dehydration capabilities. • Existence of nitrogen atoms in the pristine nanosheets structure causes the selective permeation of ions. • The nature of the C 2 N intrinsic structure and existence of the nitrogen at pore edges allows the interaction behaviours of the different ions. Using molecular dynamic simulations, the performance of carbon nitride (C 2 N) was studied for the separation of Cu 2+ and Hg 2+ as heavy metal ions from water. The high porosity of the single layer C 2 N nanosheet in comparison with other similar carbon-based membranes and the existence of nitrogen atoms at the edge of the pores increase the efficiency of C 2 N for water purification. The separation of heavy metal ions through the nanosheet is performed by applying an external voltage across the membrane. Investigation of the ions permeation through the membrane demonstrates that the permeability of the Cu 2+ ions through the C 2 N is about 2.5 times higher than that of Hg 2+ . The results of radial pair distribution function analysis illustrate that the energy barrier for ions passage is due to the hydration shell of the cations. Also, the density of the cations and water molecules, and the hydrogen bonds between water molecules in the whole system are analysed for the study of the performance of C 2 N nanosheet for ion separation and these results demonstrate that this membrane has the selectivity performance for heavy metal removal and higher permeability of the cations than that of other carbon-based membrane because of high porosity.