Heterogeneous activation of peroxymonosulfate by magnetic hybrid CuFe2O4@N-rGO for excellent sulfamethoxazole degradation: Interaction of CuFe2O4 with N-rGO and synergistic catalytic mechanism.

ABSTRACT

In order to address the low catalytic performance of magnetic CuFe2O4 caused by the agglomeration, low conductivity and potential metal ion leaching risk, N-doped reduced graphene oxide (N-rGO) with high charge density and rich active sites was employed as support to synthesize CuFe2O4@N-rGO (CuFe@NG), which was used for peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX). Results showed that the CuFe@NG/PMS system exhibited excellent degradation rate and mineralization efficiency on SMX in 60 min, which exceeded 93.15% and 31.96%, respectively. Besides, its degradation rate constants was 1.68 times higher than that of the CuFe2O4/PMS system. The enhanced performance could be mainly ascribed to the efficient synergistic activation of PMS by two components I. the successful dispersion of CuFe2O4 on N-rGO and the interaction between them exposed more Fe3+-O2- and Cu2+-O2- active sites via decreasing size and aggregation of CuFe2O4 particles; II. the supported N-rGO supplied extra CO, C-OH and C-NC active groups, resulting in a large number of π electrons; III. the pyrrole N formed by further doping of N could activate the π electrons and reduce the energy barrier of electron transfer. The abundant active groups and sites and excellent electron transfer ability co-accelerate the production of active species. Specifically, surface-bound radical (•OH, SO4•-) and singlet oxygen 1O2 played a dominant role according to ESR and quenching tests. Furthermore, M-O-C binding site between two components enhanced catalyst stability and reduced metal leaching, leading to its availability on reusability in the 5 cyclic experiments. Lastly, CuFe@NG/PMS system also possessed a strong application ability in actual aquatic environment for SMX treatment.