Ion separation using a Y-junction carbon nanotube

Abstract

Using molecular dynamics simulations, we show that a Y-junction carbon nanotube can be used toseparate K+ and Cl− ions from a KCl solution. The Y-junction nanotube is formed by connecting two smallercarbon nanotube branches of sizes (5, 5) and (6, 6) to a larger (8, 8) carbon nanotube. Whileuncharged (5, 5) and (6, 6) carbon nanotubes show close to zero occupancy ofK+ and Cl− ions, we show that a negatively charged (5, 5) carbon nanotubeand a positively charged (6, 6) carbon nanotube can be selective toK+ and Cl− ions, respectively. By performing molecular dynamics simulations on the entire systemcomprising the Y-junction carbon nanotube, the KCl solution chamber, the push plate and thereceiving chamber, we show that as the electrolyte moves through the (8, 8) carbon nanotube theK+ andthe Cl− ions can be selectively transported through the (5, 5) and the (6, 6) carbon nanotube,respectively. The formation of ion pairs can affect the separation efficiency and we discussthe conditions under which perfect separation can be obtained.