Theoretical investigation of the removal of nitrate ions from contaminated aqueous solution using functionalized silicon carbide nanosheets

The removal of NO3- contaminants from the aqueous solutions using one-layered silicon carbide nanosheets (SiCNS) membrane was investigated by molecular dynamics (MD) simulations. Due to the honeycomb structure of SiCNS membrane, it can be used for water treatment with the high water permeability and high nitrate ion rejection. First, a pore was embedded on the surface of the nano-structured SiCNS membrane. Then, it was functionalized by four chemical atoms including hydrogen, fluorine, oxygen and nitrogen, leading to H-SiCNS, F-SiCNS, O-SiCNS, and N-SiCNS systems, respectively. After doing MD simulations under the applied hydrostatic pressure, the potential of the mean force (PMF) of the water molecule and NO3- ion was calculated. The hired techniques, MD and PMF, confirmed the results of each other, proving that water molecules with the low PMF could permeate easily through these functionalized pores. At the same time, nitrate ions were trapped behind the functionalized pores of the membrane due to the high energy level required for their passage. However, at high pressures, some NO3- ions were able to pass across the large pores (H-SiCNS, F-SiCNS). In addition, in this work, the effects of increasing ion concentration and system temperature on the separation process were explored.