Electro-Dialysis-Reduction-Enabled Synergistic Nitrate Enrichment and Conversion for Wastewater Valorization

Nitrate reduction (NO₃^-RR) is appealing for treating nitrate-containing wastewater and recovering nitrogen resources. However, it requires eight electrons and suffers from high energy consumption and low ammonia concentration, limiting its economic and practical feasibility. Producing and enriching ammonia in an electron-economical way is crucial. Herein, we integrate NO₃^-RR and electrodialysis in an electro-dialysis-reduction system. A single current circulation simultaneously drives ion migration for the nitrate concentration (desalination) and electron transfer for the NO₃^-RR, thereby achieving a 26.4% reduction in energy consumption. Moreover, enhanced nitrate removal and improved ammonia selectivity was realized by the synergistic effect between desalination and NO₃^-RR. The formation of *NOH, a crucial intermediate for ammonia generation, was verified by in situ differential electrochemical mass spectrometry. This study demonstrates the dual use of coupled ion migration and electron transfer as different charge carriers to achieve synergistic wastewater treatment and resource recovery, advancing industrial sustainability.