Thermo-osmosis and enhanced ion rejection rate in Janus nanochannels under the external electric field

Abstract

The transport behavior of water molecules in a nanochannel plays an important role in the membrane distillation technology. In practical applications, a hydrophobic membrane associated with a high osmotic pressure is usually employed, which prevents the water molecules from entering into the hydrophobic nanochannel, and leads to a low evaporation rate and high energy consumption. In this paper, a Janus nanochannel model is proposed by applying an external electric field to part of the nanochannel. It is found that the electro-wetting of Janus nanochannels is helpful for the desalination process. The water molecules can easily enter into the nanochannel, which enhances the water evaporation and the thermal osmotic transport process of water molecules in the nanochannels. The freshwater production rate of the system could be significantly increased with a rate of ion rejection higher than 90 %. The study of the desalination process in the nanochannel under the external electric field provides a theoretical basis for regulating water transport in the nanochannel under the electric field to promote seawater desalination.