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Inorganic constituents in real wastewater, such as halides and carbonates/bicarbonates, may have negative effects on the performance of electrochemical systems because of their capability of quenching HO • . However, we discovered that the presence of Cl − and HCO 3 − in an electrochemical system is conducive to the formation of ClO • , which plays an important role in promoting the simultaneous elimination of biorefractory organics and nitrogen in secondary coking wastewater effluent. The 6-h operation of the coupled electrochemical system (an undivided electrolytic cell with a PbO 2 /Ti anode and a Cu/Zn cathode) at a current density of 37.5 mA cm −2 allowed the removal of 87.8% of chemical oxygen demand (COD) and 86.5% of total nitrogen. The electron paramagnetic resonance results suggested the formation of ClO • in the system, and the probe experiments confirmed the predominance of ClO • , whose steady-state concentrations (8.08 × 10 −13 M) were 16.4, 26.5, and 1609.5 times those of Cl 2•− (4.92 × 10 −14 M), HO • (3.05 × 10 −14 M), and Cl • (5.02 × 10 −16 M), respectively. The rate constant of COD removal and the Faradaic efficiency of anodic oxidation obtained with Cl − and HCO 3 − was linearly proportional to the natural logarithm of the ClO • concentration, and the specific energy consumption was inversely correlated to it, demonstrating the crucial role of ClO • in pollutant removal.

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