Magnetic nanoscale MnFe2O4 as heterogeneous Fenton-like catalyst for rhodamine B degradation: efficiency, kinetics and process optimization

Due to the coupled transformations between metal ions with variable valence states, manganese ferrite (MnFe2O4) is regarded as an efficient catalyst in a heterogeneous Fenton-like system for the degradation of organic contaminants. In this work, the magnetic nanoscale MnFe2O4 was synthesized via a simple hydrothermal method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). Results on the degradation tests indicated a high catalytic ability of MnFe2O4 nanocrystals to activate hydrogen dioxide (H2O2) to degrade active dye rhodamine B (RhB). Moreover, the RhB degradation process in the MnFe2O4-H2O2 Fenton-like system followed a Behnajady-Modirshahla-Ghanbery (BMG) kinetic model. The catalytic conditions, including catalyst dosage, RhB concentration, H2O2 dosage, solution pH and reaction temperature, had essential effects on RhB degradation efficiency and BMG kinetic parameters. The process optimization of RhB degradation was designed by central composite design (CCD) under response surface methodology (RSM). A mathematic model of the quadratic polynomial was established for the fitting analysis of RhB degradation, which was significant and reliable by the analysis of variance (ANOVA). Based on the programmed prediction, the optimum parameters for RhB degradation in the MnFe2O4-H2O2 system were determined as 2 of solution pH, 19.6 mmol center dot L-1 of H2O2 dosage, 2.0 g center dot L-1 of catalyst dosage and 180 min of reaction time. Under these optimum conditions, the predicted and experimental values of RhB degradation efficiency were 99.42% and 98.17%, respectively.