Excellent defluorination performance in defective CoNiO₂ based asymmetric flow capacitive deionization system

Area of Science:

• Environmental Science
• Materials Science
• Electrochemistry

Background:

• Industrial fluorine-containing wastewater poses significant environmental and health risks.
• Traditional fluoride removal methods often have limitations such as secondary pollution or high costs.
• Flow electrode capacitive deionization (FCDI) shows promise but struggles with mismatched ion adsorption and energy efficiency.

Purpose of the Study:

• To develop an improved asymmetric FCDI system for efficient fluoride (F-) removal from wastewater.
• To address the limitations of conventional FCDI, including mismatched ion adsorption and energy consumption.
• To investigate the use of defective metallic rock salts as advanced electrode materials.

Main Methods:

• Fabrication of asymmetric FCDI electrodes using defective metallic rock salts (CoNiO2) with carbon black (CB) as anodic material and Prussian blue derivatives (CoHCC) as cathodic electrode.
• Performance evaluation of the CoNiO2/CB electrode for fluoride adsorption capacity, energy consumption, and stability.
• Utilizing experimental characterizations and computational modeling to understand the defluorination mechanism.

Main Results:

• The CoNiO2/CB electrode demonstrated high F- adsorption capacity (13.78 mg/g) and low energy consumption (5.39 J/mg) at 1.2 V for 1000 mg/L NaF solution.
• Improved F- removal (approaching 95%) and adsorption capacity (19 mg/g) were achieved at 1.6 V with 500 mg/L NaF.
• The electrode exhibited excellent stability in treating fluoridated wastewater.

Conclusions:

• Defective metallic rock salts (CoNiO2/CB) are effective anodic materials for asymmetric FCDI, significantly enhancing fluoride removal.
• The enhanced defluorination performance is attributed to F- intercalation in oxygen defects within the CoNiO2 structure.
• This study presents a promising defective strategy for improving defluorination in wastewater treatment using asymmetric FCDI.