Electro-enhanced chlorine-mediated ammonium nitrogen removal triggered by an optimized catalytic anode for...

Electrochemical technology has unique superiorities in chlorine-mediated pollutant oxidation, but has limited application in saline wastewater treatment due to inadequate efficiency and high energy consumption. To promote electrochemical oxidation capacity, a novel but low-cost electrode containing TiO₂/Co-WO₃/SiC was prepared and optimized, achieving highly efficient chlorine-mediated ammonium nitrogen oxidation (98.3 ± 2.2% in 120 min, with initial NH₄⁺-N of 10.2 ± 0.5 mg L^-1) in a simple electrochemical system with supplied current density only at 1.00 mA cm^-2. Comparing with unmodified carbon fiber cloth, the catalytic anode achieved 96.0% nitrogen selectivity, enhanced the system current efficiency by 20.6% and reduced the energy consumption by 54.4%, making the treatment of simulated mariculture wastewater both energy-saving (36.5 ± 2.8 kWh kg^-1 NH₄⁺-N) and cost-effective (1.45 US$ m^-3), comparing with previously reported electrochemical processes (54-622 kWh kg^-1 NH₄⁺-N). The nitrogen content (<1 mg L^-1) in the treated wastewater, containing only 0.18 mg L^-1 NH₄⁺-N, meets the discharge standard of mariculture wastewater. The promoted electrochemical oxidation should be attributed to the chloride derived species (HOCl and ClO^-) and related active species (Cl, ClO, OH, etc.). This easily prepared and reusable catalytic electrode is a promising alternative to conventional anode materials in sustainable electrochemical treatment of saline wastewater.