Recent development of mixed metal oxide anodes for electrochemical oxidation of organic pollutants in water

Mixed metal oxides (MMOs) have been extensively employed for heterogeneous catalysis. In recent years, MMOs have received an intensive interest as anode materials for electrochemical treatment of wastewaters which contain recalcitrant organics. This review article gives an overview of the classification of MMO anodes systems, synthesis methods, characterization techniques, and recent advance of removing or alleviating various recalcitrant organic pollutants using MMO anodes, highlighting areas of consensus and currently unresolved issues. Practical issues pertinent to modification to the catalytic activities of MMO anodes are discussed, including nano- and microstructured deposits, doping and polymer composites. Electrogenerated reactive oxygen species (ROS) with MMO anodes and their determination by various techniques have also been reviewed. In addition, this article discusses several important factors which could affect the electrochemical oxidation of recalcitrant organics with MMO anodes, and critically identifies the shortcomings in current research including discrepant results and ambiguous conclusions. Finally, the challenges and possible improvement of MMO anodes for their future application are also proposed. (C) 2014 Elsevier B.V. All rights reserved.