Heterogeneous catalytic degradation of 2,4-dinitrotoluene by the combined persulfate and hydrogen peroxide activated by the as-synthesized Fe-Mn binary oxides

Abstract

Fe-Mn binary oxides (FMBOs) with different molar ratios of Fe and Mn (1:1–8:1) synthesized in a redox-precipitation method were investigated for the activation of a combination of persulfate (PS) and hydrogen peroxide (HP) for the degradation of 2,4-dinitrotoluene (2,4-DNT). X-ray diffraction and field-emission scanning electron microscopy were used to demonstrate FMBOs with different molar ratios exhibited no significant influence on crystallinity and morphology. The degradation efficiency and kinetics of 2,4-DNT in the FMBOs/PS/HP system were investigated. The results showed that F4.5M1BO exhibited better effectively heterogeneous catalytic activity in the activation of the combined PS and HP. The effects of initial HP and PS concentrations, F4.5M1BO dose, initial pH, and coexisting anions on the degradation efficiency and kinetics of 2,4-DNT were comprehensively investigated. A possible activation mechanism in the F4.5M1BO/PS/HP system was proposed based on electron paramagnetic resonance, radical scavenger tests, X-ray photoelectron spectroscopy, and Fourier transformation infrared spectroscopy. The results showed that Fe(II), Mn(II), and Mn(III) ( is representative of the element in solid form) are active sites on the surface of F4.5M1BO that effectively activated the combined PS and HP to generate the dominant SO4− and HO. Furthermore, the proportions of lattice oxygen, surface adsorbed species, and adsorbed molecular water activated of the combined PS and HP. The strong synergistic interaction reaction among Fe(III), Mn(III), Mn(IV), and HP could be deduced and confirmed. These findings provide new insight into the potential of F4.5M1BO as a heterogeneous catalyst in the activation of the combined PS and HP for improving the degradation of refractory organic pollutants.