Enhanced desalination performance in carbon nanotubes by terahertz electric fields

Abstract

Attaining a high cut-off rate for salt solutions while ensuring significant water flux across membranes is crucial in the desalination process. Herein, we demonstrate by molecular dynamics (MD) simulations that the desalination performance in carbon nanotubes (CNTs) can be greatly improved by applying a terahertz electric field. At a specific field frequency, with increasing the field strength, the fluxes of Cl⁻, Na⁺ and water collectively exhibit a decreasing trend; however, the ion rejection demonstrates a significant increase, reaching up to 100% within the simulation time. Moreover, for a given field strength, the fluxes of Cl⁻, Na⁺, and water display a minimum behavior as the field frequency increases, leading to the maximum behavior of ion rejection (up to 100%). This suggests a frequency optimization for the desalination performance, where the best ion rejection occurs in a frequency range of 10 ∼ 20 THz. Consequently, the utilization of lateral terahertz electric field holds great promise in desalination, providing valuable insights for designing desalination membranes with low energy consumption and high freshwater production efficiency.