Mechanism for enhancing biodegradability of antibiotic pharmacy wastewater by in-situ generation of H2O2 and radicals over MnOx/nano-G/2-EAQ/AC cathode

To improve the oxidation efficiency of cathode in the electrochemical advanced oxidation processes (EAOPs), the manganese oxide/nano-graphite (MnOx/nano-G) was synthesized via a liquid-phase precipitation method. Structure and property of MnOx/nano-G calcined at different temperatures (350, 450 and 550 degrees C) were investigated. Results showed that nano-G ashing and MnOx agglomeration were happened at 550 degrees C. MnOx/nano-G calcined at 450 degrees C was proved to have the highest efficiency for phenol degradation. The valences of Mn in the MnOx/nano-G (450 degrees C) were + 3 (Mn2O3) and + 4 (MnO2). Activity of the prepared MnOx/nano-G/2-ethylanthraquinone/activated carbon (MnOx/nano-G/2-EAQ/AC) cathode was investigated through evaluating H2O2 and (OH)-O-center dot yields, phenol degradation with scavengers, and impedances. 2-EAQ and MnOx could promote the two-electron reduction of O-2 (H2O2) and the generation of (OH)-O-center dot radicals, respectively. After 6 h electrolysis, the biodegradability (BOD5/COD) of antibiotic pharmacy wastewater was improved from 0.01 to 0.31, indicating that MnOx/nano-G/2-EAQ/ AC cathode had promise for further application. (C) 2016 Elsevier Ltd. All rights reserved.