Nitrate pollution from industrial wastewater poses a major challenge for water environment management, with conventional biological denitrification technologies struggling with inefficiency—particularly in high-salinity conditions. While electrochemical reduction shows promise for converting nitrates into valuable resources, it has long been hampered by high energy use and low product yields. Bridging efficient wastewater purification with resource recovery has remained a bottleneck in environmental engineering.

To tackle this issue, a research team led by Prof. QU Jiuhui from the Research Center for Eco-Environmental Sciences of the Chinese Academy of Sciences has developed a novel solution: the electrodialysis-reduction (EDN) coupled water purification system. By integrating electrodialysis and electrochemical reduction, the EDN system efficiently converts nitrate pollutants in wastewater into high-value ammonia—all while desalinating water and enabling recovery.

The progress lies in a design that a single electric current drives both salt ion enrichment and nitrate reduction. Under a direct-current electric field, nitrate ions migrate selectively through an anion exchange membrane, concentrating efficiently. These concentrated nitrates then undergo an eight-electron reduction at the cathode, specifically transforming into ammonia—a high-value product.

In addition, the EDN system can suppress unwanted byproducts like nitrites. Through optimized membrane stack design and operational tweaks, the team achieved an ammonia selectivity of 71.6%. This system also minimizes the energy losses commonly associated with electrode reactions in traditional electrodialysis setups, thanks to a novel separation strategy.

In performance tests, the system surpassed traditional stepwise treatments by consuming 26.4% less energy—with energy use for ammonia production matching industrial synthesis processes. In real-world industrial wastewater trials, it hit 98.6% desalination efficiency and 82.6% nitrate conversion. Even after 10 consecutive cycles, it retained 97% desalination efficiency and 70% ammonia selectivity, proving its stability and reusability.

By merging wastewater treatment with resource recovery, the EDN system paves the way for near-zero discharge of industrial effluents.

Funded by initiatives like the CAS International Partnership Program, the research was recently published in Environmental Science & Technology.