Photo-Fenton degradation of ammonia via a manganese-iron double-active component catalyst of graphene-manganese ferrite under visible light

Graphene-manganese ferrite (rG-MnFe2O4) was developed to degrade NH3. It was characterized by X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results using rG-MnFe2O4 as a heterogeneous photo-Fenton catalyst showed a degradation of 92.0% was achieved through visible light irradiation of 50.0 mg L-1 NH3-N solution at pH 10.5 in the presence of 1.0 mmol/L H2O2 for 10 h. The product for the degradation of NH3 was identified as N-2 but not NO2- or NO3-. The degradation of ammonia follows the pseudo first order reaction law, the average apparent reaction rate constant is obtained to be 0.0396 min(-1) under white light irradiation. XPS measurements showed that Mn(III) and Fe(II) are formed during photo-Fenton degradation of NH3, which suggests that Mn and Fe simultaneously participate in the photocatalytic cycle. Thus, rG-MnFe2O4 is a double-effect photo-Fenton catalyst. The double-active catalytic mechanism was explored. (C) 2015 Elsevier B.V. All rights reserved.