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

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.