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Discovering the Importance of ClO in a Coupled Electrochemical System for the Simultaneous Removal of Carbon and Nitrogen from Secondary Coking Wastewater Effluent

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journal contribution
posted on 25.06.2020, 18:19 authored by Wenxiao Zheng, Liuyi Zhu, Sheng Liang, Jinshao Ye, Xin Yang, Zhenchao Lei, Zhang Yan, Yongdong Li, Chaohai Wei, Chunhua Feng
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 HCO3 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 PbO2/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 Cl2•– (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 HCO3 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.