Enhanced Selective Electrosorption of Nitrate from Wastewater by Controllably Doping Nitrogen into Porous Carbon with...

The biological NO₃^- removal process might be accompanied by high CO₂ emissions and operation costs. Capacitive deionization (CDI) has been widely studied as a very efficient method to purify water. Here, a porous carbon material with a tunable nitrogen configuration was developed. Characterization and density functional theory calculation show that nitrogenous functional groups have a higher NO₃^- binding energy than Cl^-, SO₄^2-, and H₂PO₄^-. In addition, the selectivity of NO₃^- is improved after the introduction of micropores by using the pore template. The NO₃^- ion removal and selectivity of MN-C-12 are 4.57 and 3.46-5.42 times that of activated carbon (AC), respectively. The high NO₃^- selectivity and electrosorption properties of MN-C-12 (the highest N content and micropore area) are due to the synergistic effect of the affinity of nitrogen functional groups to NO₃^- and microporous ion screening. A CDI unit for the removal of nitrogen from municipal wastewater was constructed and applied to treat wastewater meeting higher discharge standards of A (N: 15 mg L^-1) and B (N: 20 mg L^-1) ((GB18918-2002), China). This work provides new insights into enhanced carbon materials for the selective electrosorption of wastewater by CDI technology.