Efficient degradation of sulfamethoxazole by ascorbic acid modified Mn3O4 via peroxymonosulfate activation
A new ascorbic acid modified Mn3O4(AA-MO)was fabricated by a hydrothermal-ultrasonic method.The sample's physical and chemical properties were characteristiced by XRD,FTIR,SEM,TEM and XPS.AA-MO was utilized to activate peroxymonosulfate(PMS)for sulfamethoxazole(SMX)degradation.The results depicted that the SMX degradation efficiency was firstly increased and then decreased in the pH range of 2.0～10.0,and the AA-MO/PMS system exhibited the best catalytic performance in the neutral environment.The increase of PMS concentration and catalyst dosage could both significantly promote the degradation of SMX.Compared with MO,AA-MO displayed a more stable catalytic performance after 3 cycles through reusability experiments.SO4·-was the main active species in the SMX degradation process by scavenging experiments.The electron transfer reactions between AA-MO and PMS could generate free radicals to remove SMX,and the oxidation resistance of AA could maintain the high catalytic performance of MO.Six possible degradation intermediates were identified by HPLC-MS/MS.In the three proposed degradation pathways,SMX was degraded by ring opening,S-N bond breaking,hydroxylation and oxidation.The toxicity threshold of SMX was calculated by ECOSAR model and ecotoxicity analysis was performed,while the toxicity of products P2,P5 and P7 should be concemed.
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