Microwave-induced catalytic oxidation of malachite green under magnetic Cu-ferrites: New insight into the degradation mechanism and pathway

Increasing attention has been paid to magnetic ferrites due to their high catalytic activity toward environmental contaminants. However, there is little information related to the generation of active species by magnetic ferrites under microwave (MW) irradiation. In this study, MW-induced catalytic oxidation for malachite green (MG) was performed over CuFe2O4 prepared by co-precipitation method. MW irradiation could greatly enhance the activity of CuFe2O4 for MG degradation. Several scavengers were used to identify the types of active species participated in the degradation process, and to evaluate the roles of them. The holes, O-center dot(2)- and (OH)-O-center dot contribute to about 43%, 31% and 26% of degradation efficiency for MG, respectively. The possible mechanism was elucidated and degradation pathway was deduced. The enhancement of MW-induced catalytic performance could be mainly attributed to a unique MW-induced holes activation process, while both (OH)-O-center dot and O-center dot(2)- also participate in the catalytic oxidation of MG. The intermediates and products were studied by HPLC, FTIR and ion chromatography (IC) to provide a comprehensively evaluation of degradation, indicating that no intermediates and secondary pollution. These findings provided a new insight into the catalysis of ferrites under MW for the degradation of MG and possibly other relevant environmental contaminants. (C) 2014 Elsevier B.V. All rights reserved.