Performance of fluorine removal using flow electrode capacitive deionization (FCDI): validation and optimization

Area of Science:

• Environmental Science
• Electrochemistry
• Materials Science

Background:

• Photovoltaic (PV) wastewater contains fluoride, posing environmental challenges.
• Electrochemical methods offer potential for efficient wastewater treatment.
• Capacitive deionization (CDI) is a promising technology for ion removal.

Purpose of the Study:

• To demonstrate the efficacy of a flow-electrode capacitive deionization (FCDI) system for electrochemical defluorination of PV wastewater.
• To systematically optimize operational parameters for enhanced FCDI performance.
• To analyze factors influencing fluoride removal efficiency and energy consumption.

Main Methods:

• Symmetrical FCDI system design.
• Systematic investigation and optimization of applied voltage, electrode content, flow rate, and electrolyte concentration.
• Analysis of fluoride removal efficiency and energy consumption under various conditions.
• Evaluation of performance in mixed-ion wastewater with nitrate competition.

Main Results:

• Optimal applied voltage of 1.2 V achieved 92.9% fluoride removal efficiency.
• Electrode content of 0.75 wt% yielded 98.3% removal efficiency, with higher content increasing energy consumption.
• Optimized flow rate of 45 mL/min resulted in 98.6% removal efficiency and reduced energy use.
• 1 g/L electrolyte addition enhanced performance, achieving 92.9% removal efficiency.
• Competitive adsorption with nitrate ions reduced fluoride removal efficiency from 96.2% to 87.3% at doubled nitrate concentration.

Conclusions:

• The FCDI system demonstrates high efficiency for electrochemical defluorination of PV wastewater.
• Optimized operational parameters significantly enhance fluoride removal and reduce energy consumption.
• The FCDI system exhibits robust performance even in complex matrices with competing ions, offering a sustainable treatment approach.