Coupling Nitrate-Saturated Resin Regeneration with Electrochemical Ammonium Production

Nitrate (NO₃^-) persistence in water poses severe ecological and health risks. Electrochemical reduction of nitrate to ammonia (ENRA) offers a promising route for simultaneous nitrate remediation and ammonia (NH₃) production. Nevertheless, its real-world application is hindered by cathode fouling, energy inefficiency, and poor performance in complex water matrices. Nitrate-selective anion exchange resins (NAERs) effectively separate and enrich nitrate from complex water, which may mitigate inorganic scaling and boost energy efficiency of ENRA, yet require chemical regeneration with substantial reagent consumption. To address these issues, we developed a hybrid innovative extraction-electrocatalysis-recovery-system (EERS) that integrates ENRA with NAERs. In simulated wastewater, EERS maintained a stable nitrate desorption efficiency of 76.5 ± 1.3% over three cycles, markedly outperforming chemical regeneration, which declined from 73.5 to 56.2%. In real nitrate-polluted groundwater, EERS achieved ∼9.5-fold nitrate enrichment and a NO₃^- removal efficiency of 86-100% over three cycles. Moreover, EERS yielded >900 mg L^-1 ammonia over each cycle. Notably, the integrated system minimizes reagent consumption by enabling continuous desorbent regeneration and electrochemical conversion, substantially reducing chemical demand and on-site storage requirements. Lastly, we confirmed the structural integrity of the resin and the Cu₂O@CF electrode, validating EERS's robustness in complex aqueous environments. These results demonstrate a scalable and sustainable platform for decentralized nitrate remediation with ammonia production in real water systems.