Enhanced salt removal in flow-electrode capacitive deionization using PEDOT:PSS as an electron mediator

Area of Science:

• Water treatment technologies
• Materials science
• Electrochemistry

Background:

• Capacitive deionization (CDI) is a sustainable desalination method.
• Flowable electrode CDI (FCDI) offers continuous operation but suffers from poor electrical conductivity between particles.
• Activated carbon (AC) is a common material for FCDI electrodes.

Purpose of the Study:

• To improve the salt removal performance of FCDI by addressing the limited electrical conductivity of flowable electrodes.
• To investigate the role of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as an electron mediator in AC-based FCDI systems.

Main Methods:

• Incorporation of PEDOT:PSS into aqueous AC slurry electrodes to form electrical bridges.
• Optimization of PEDOT:PSS doping strategy to maximize electron mediation.
• Evaluation of salt removal efficiency and average salt removal rate (ASRR) in the modified FCDI system.

Main Results:

• The addition of PEDOT:PSS significantly enhanced interparticle electrical connectivity in the flowable electrodes.
• Salt removal efficiency increased from 18.05% (pristine AC) to 61.57%, a 3.4-fold improvement.
• The average salt removal rate (ASRR) increased by 3.6 times, with maintained high energy efficiency.

Conclusions:

• PEDOT:PSS effectively acts as an electron mediator, overcoming the conductivity limitations of AC in FCDI.
• This approach offers a simple, scalable, and highly effective strategy for enhancing FCDI performance.
• The findings present a novel application of conducting polymers for advanced water desalination.