Efficient degradation of trimethoprim by catalytic ozonation coupled with Mn/FeOx-functionalized ceramic membrane: Synergic catalytic effect and enhanced anti-fouling performance

Abstract

In this study, the flat microfiltration ceramic membrane (CM) was modified by wet impregnation method (Mn-Fe-CM) to catalyze ozone (O3) for the oxidative degradation of trimethoprim (TMP). The conventional characterization test showed that the Mn-Fe binary oxides (Mn/FeOx) with the crystal structure of FeMnO3 were successfully loaded on the membrane and the catalytic performance of Mn-Fe-CM for O3 was apparently enhanced as compared to CM. Consequently, compared with O3 oxidation alone, the degradation and mineralization efficiencies of TMP in the O3/Mn-Fe-CM system were both improved and 98.6% of TMP could be removed within 10 min. The degradation efficiency of TMP decreased with the increasing pH and the addition of Cl-、HCO3–、PO43-, while humic acid (HA) exhibited negative effect on the TMP removal. Radical scavenger experiment and electron paramagnetic resonance (EPR) analysis confirmed that direct oxidation by O3 played an important role in the degradation of TMP, while hydroxyl radical (·OH) and 1O2 also participated. Fe(II) could act as an intermediate to transfer electrons and accelerate the transformation of Mn(III) to Mn(II) and Mn(IV) to Mn(III) during the ozonation process, which definitely strengthened the synergic catalytic effect of Mn-Fe-CM. The proposed degradation mechanism of TMP mainly contained hydroxylation, carbonylation, demethoxylation and deamination. Due to the strong catalytic ozonation performance for organic pollutants degradation, the O3/Mn-Fe-CM system revealed better anti-membrane fouling ability, strong cyclic usage performance and high applicability for the actual surface water treatment.