Upgrading the peroxi-coagulation treatment of complex water matrices using a magnetically assembled mZVI/DSA anode: Insights into the importance of ClO radical

Abstract

electrochemical technologies for water treatment have flourished over the last decades. However, it is still challenging to treat the actual complex water effluents by a single electrochemical process, often requiring coupling of technologies. In this study, an upgraded peroxi-coagulation (PC) process with a magnetically assembled mZVI/DSA anode has been devised for the first time. COD, NH3-N and total phosphorous were simultaneously and effectively removed from livestock wastewater. The advantages, influence of key parameters and evolution of electrogenerated species were systematically investigated to fully understand this novel PC process. The fluorescent substances in livestock wastewater could also be almost removed under optimal conditions (300 mA, 0.2 g ZVI particles and pH 6.8). The interaction between ¿OH and active chlorine yielded ClO¿ with a high steady-state concentration of 6.85 × 10􀀀 13 M, which did not cause COD removal but accelerated the oxidation of NH3-N. The Mulliken population suggested that ¿OH and NH3-N had similar electron-donor behavior, whereas ClO¿ acted as an electron-withdrawing species. Besides, although the energy barrier for the reaction between ¿OH and NH3-N (17.0 kcal/mol) was lower than that with ClO¿ (18.8 kcal/mol), considering the tunneling in the H abstraction reaction, the Skodje-Truhlar method adopted for calculations evidenced a 17-fold faster NH3-N oxidation rate with ClO¿. In summary, this work describes an advantageous single electrochemical process for the effective treatment of a complex water matrix.