Abstract
Bio-inspired ion diodes constructed by asymmetric charged (bipolar) nanochannels have shown outstanding performance in ion transport control which are promising candidates for the development of high-performance water desalination systems. However, understanding of seawater desalination by ionic diode nanochannels is still very limited. This paper uses a numerical model coupling Poisson-Nernest-Planck and Navier-Stokes equations to systematically investigate the desalination behavior of bipolar ion diodes. The effects of nanochannel structure including channel length, diameter, charge polarity, properties of working fluids, and external pressure on the ion rejection efficiency are investigated. The results show that under optimal conditions, the bipolar channel can produce better ion rejection compared to the unipolar channel due to its excellent ion transport control performance, a bipolar ion diode-based desalination system can produce 20 % higher ion rejection rates compared to that of a unipolar channel system. In particular, an external voltage applied to the system is able to further enhance the ion rejection performance of the bipolar channel by more than 27 % compared to that of the case without applied voltage. This work systematically reveals the working mechanism of enhancing water desalination performance by bio-inspired ion diodes and provides a new route for the development of high-efficiency desalination plants.
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