Flow-electrode capacitive deionization with highly enhanced salt removal performance utilizing high-aspect ratio...

Area of Science:

• Materials Science
• Electrochemistry
• Environmental Engineering

Background:

• Flow-electrode capacitive deionization (FCDI) offers continuous desalination without a discharge step, unlike fixed-electrode systems.
• Poor conductivity of flow electrode slurries limits FCDI performance, despite potential benefits of higher carbon loading for salt removal.
• Increased slurry viscosity hinders the loading of active materials, posing a challenge for enhancing desalination capacity.

Purpose of the Study:

• To enhance the salt removal performance of activated carbon (AC)-based flow electrodes in FCDI systems.
• To investigate the effect of functionalized carbon nanotubes (FCNTs) on the conductivity and desalination efficiency of AC slurries.
• To determine the optimal FCNT characteristics for improving FCDI performance.

Main Methods:

• Introduction of functionalized carbon nanotubes (FCNTs) into activated carbon (AC) based flow electrodes.
• Electrochemical analysis to confirm the formation of a conductive percolation network.
• Measurement of salt removal rate at a saline water concentration of 35.0 g/L and applied potential of 1.2 V.

Main Results:

• A four-fold increase in salt removal rate was achieved by adding 0.25 wt% FCNT to 5 wt% AC, reaching 5.72 mmol/m²s.
• The addition of FCNTs created conductive bridges between AC particles, significantly improving slurry conductivity.
• High aspect ratio FCNTs demonstrated superior performance in enhancing salt removal compared to low aspect ratio FCNTs.

Conclusions:

• Functionalized carbon nanotubes effectively enhance the conductivity of AC-based flow electrodes for FCDI.
• The incorporation of FCNTs leads to a substantial improvement in salt removal capacity, setting a new literature record.
• This advancement holds significant promise for the development of highly efficient and practical desalination systems.