Recyclable magnetic Fe3O4@C for methylene blue removal under microwave-induced reaction system

The reclamation and removal of organic pollutants are difficult issues of world concern. In this study, a microwave-induced reaction system (MIRS) is applied to synthesize the multifunctional composite of Fe3O4@C, which is employed to adsorb, separate and catalytic oxide the typical organic dye of methylene blue (MB). SEM, TEM, VSM, XPS, pHpzc, and N2 adsorption performances are carried out to characterize the Fe3O4@C. Results show that the Fe3O4@C mainly consists of activated Fe-O-C microspheres, which possess plentiful mesopore and macropore structures on surfaces. Batch adsorption experiments were carried out by varying key reaction conditions to optimize these. The maximum adsorption capacity of MB onto the Fe3O4@C was 305.0 mg g-1 in 120 min, at pH 10, and at a temperature of 323 K. MIRS was also assisted to regenerate the spent Fe3O4@C which presented good regeneration efficiency by sustaining 16 regeneration cycles without any oxidizing agent. SEM images and FTIR spectrum verified that MB would translate into greater or smaller-sized carbon microspheres. What's more, the adsorption of MB onto both initial and the 16th regenerated Fe3O4@C obeyed the Langmuir isotherm model and followed the pseudo-second-order adsorption kinetics, indicating the adsorptive stability after regeneration. In this study, the Fe3O4@C combined with MIRS may be one innovative strategy for organic pollutants' complete removal in the future.