Abstract:

Different charged functional groups including ―COO^- and ―NH₃⁺ were added to the interior and entrance of (15, 15) armchair carbon nanotubes (CNTs) with a diameter larger than 2 nm to construct membranes that imitated the structure of the protein aquaporin-4.The potential of mean force, conductance, and density distributions of ions in the CNTs were calculated.The results showed that under 200 MPa, CNTs modified with oppositely charged groups in their interior and at their entrance could greatly improve salt desalination on the basis of high water flux.When five pairs of ―COO^- and ―NH₃⁺ functional groups were added to the interior of a CNT or four pairs of ―COO^- and ―NH₃⁺ functional groups were added to the interior of a CNT with another pair at the entrance, 100% Cl^- rejection and 88% Na⁺ rejection were achieved.The lowest water conductivity of the functionalized CNTs was 4.6 times that of (8, 8) unfunctionalized CNTs, and even slightly lower than that of unfunctionalized (15, 15) CNTs.

Key words: Molecular dynamics simulation, Biomimetic modification, Reverse osmosis membrane, Diameter larger than 2 nm, Carbon nanotube, Desalination