Novel MnO2/reduced graphene oxide micromotors for the highly efficient removal of tetrabromobisphenol A in aqueous solution

Tetrabromobisphenol A (TBBPA), an emerging contaminant, has been identified as an endocrine disrupter with potential health risk. This study reports that reduced graphene oxide (rGO)-based self-propelled micromotors were developed with manganese oxide (MnO2) nanoparticles for efficient TBBPA removal from water. The prepared micromotors were characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Besides the enhanced localized mixing effect due to self-motion, the outstanding adsorption and catalytic oxidation performance were ascribed to the synergistic effect of MnO2 and rGO during the removal process of TBBPA. The effects of pH, H2O2 concentration, initial TBBPA concentration, the amount and length of the micromotors, and the solvent on the removal efficiency were further studied. After systematic optimization of the treatment conditions, the composite MnO2/rGO micromotors achieved more than 90% removal of TBBPA within 60 min at an initial concentration of 100 mg L-1. The micromotors showed efficient removal performance for TBBPA within four consecutive runs, indicating their good stability and reusability. The progressive degradation pathways of TBBPA were proposed based on the analysis of the degradation products identified by GC/MS. It is suggested that the decomposition pathways of TBBPA with the MnO2/rGO micromotors involve debromination, substitution and cleavage reactions. The results offer a novel approach for the removal of TBBPA from aqueous solutions in environmental applications.