Microwave-enhanced catalytic degradation of methylene blue by porous MFe2O4 (M = Mn, Co) nanocomposites: Pathways and mechanisms

Abstract Developing rapid and effective methods to remove dyes from water has gained global concerns. In this study, we prepared porous MnFe 2 O 4 (RMN) and porous CoFe 2 O 4 nanocomposite (RCN) with high BET surface area and pore volume using rice hull, and investigated their catalytic degradation and degradation mechanisms for methylene blue (MB). Under microwave heating, the MB removal by RMN and RCN was accelerated and enhanced significantly due to the selective heating and enhanced catalytic degradation activities. The MB removal fits pseudo-second-order model. The removal rate increases with sample dosage, microwave output power, and initial pH value. The resulting pH value was inclined to neutral after microwave treatment. The dimethylamino including methyl groups in MB molecule are easier and prior to be degraded by ferrite nanoparticles in the nanocomposites during either adsorption or microwave treatments. According to the resulting concentrations of MB, NO 3 − , and SO 4 2− , the maximum MB removal achieved 99.7%, among which more than 46.8% molecules were completely degraded. This study provided essential information on the degradation behavior and mechanism of basic dyes by microwave-enhanced ferrite treatments and also supplied a potential rapid and effective method to remove organic contaminants from aqueous solutions.