The ever-growing demands with the limited supply of clean water have led to tremendous stress in households and industries. Electrochemical water desalination has turned out to be one of the most efficient ways to provide clean water. Owing to the advancement of electrochemical-desalination mechanisms and materials, great success has been achieved in desalination worldwide. Redox-flow battery desalination (FBD), an emerging electrochemical technology based on redox reactions and charge transfer, has recently been established for high-salinity desalination. In this study, a four-channel FBD system was developed for continuous desalination with the use of redox reactions of ferri-/ferrocyanide couples. To enhance the average removal rate (ASRR), carbon fibers from electrospinning with smooth morphology were prepared as electrodes. The experimental results indicated that the carbonization temperature could be a dominant parameter affecting the characteristics of the electrode, including conductivity and specific surface area. With increasing the carbonization temperature from 700°C to 900°C, the ASRR for 0.1 M NaCl solution desalination can be enhanced from 64.4 μg/min-cm<sup>2</sup> to 97.5 μg/min-cm<sup>2</sup> under 0.4 V, respectively. The energy consumption was 42.81 kJ/mol (0.01 kWh/mol), which was significantly lower than that of electrodialysis (171.25 kJ/mol) and capacitive deionization (118.37 kJ/mol). The low energy consumption can be attributed to the rapid rate of electron transfer between the ferri-/ferrocyanide redox couple and at the electrode–electrolyte interface. Therefore, with the advantages of high average removal rate and low energy consumption, the FBD system with the use of electrospun carbon fiber electrodes could be considered a promising route for water reuse.

Redox-flow battery desalination using carbonized electrospun nanofibers for highly efficient water reuse

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