Enhancing selective NH₄⁺ recovery from wastewater using modified zeolite-based flow electrode capacitive deionization

Area of Science:

• Environmental Chemistry
• Materials Science
• Electrochemistry

Background:

• Flow-electrode capacitive deionization (FCDI) is promising for water treatment but faces challenges with electrode selectivity and cost.
• Ammonium (NH₄⁺) removal from wastewater is crucial for environmental protection and resource recovery.

Purpose of the Study:

• To develop a low-cost, selective electrode material for ammonium recovery using FCDI.
• To evaluate the performance of modified zeolite electrodes in FCDI for ammonium removal from wastewater.
• To demonstrate a sustainable strategy for wastewater resource recovery.

Main Methods:

• Synthesized a novel ammonium adsorption electrode by modifying zeolite with ethylenediaminetetraacetic acid disodium salt (EDTA-2Na).
• Prepared flow electrodes using a mixture of EDTA-zeolite and carbon black.
• Investigated the FCDI process for ammonium recovery from food waste fermentation supernatant, analyzing ion exchange and transmembrane selectivity.
• Separated the ammonium-rich modified zeolite for potential use as fertilizer.

Main Results:

• The EDTA-zeolite flow electrode demonstrated high selectivity and adsorption capacity for NH₄⁺.
• Achieved a transmembrane selectivity of 3.46 for NH₄⁺ over Na⁺.
• Under optimal conditions, 99.15% NH₄⁺ removal from fermentation supernatant and 95.92% NH₄⁺ storage in EDTA-zeolite were achieved.
• Demonstrated efficient separation of NH₄⁺-rich zeolite via gravitational settling.

Conclusions:

• The developed low-cost modified zeolite electrode is effective for selective ammonium recovery using FCDI.
• The FCDI system offers a sustainable and efficient approach for wastewater resource recovery, converting waste into valuable fertilizer.
• This technology addresses limitations of conventional FCDI in wastewater treatment applications.