Performance And Mechanism Of The Oxidation Of Oxcarbazepine And Diuron By KHSO₅ Catalyzed With Ferrite

In this study,two catalysts(NiFe2O4 and EGCG-Fe3O4)were prepared using hydrothermal method and hydrothermal-ultrasound method,respectively.Various techniques,such as XRD,SEM,TEM,FTIR,and zeta potential,were used to characterize the as-prepared catalysts.Bench experiments were performed to investigate the effects of catalyst dosage,oxidant dosage,initial concentration of target contaminants,initial solution pH,co-existed anions and humic acid.Besides,the recycled use of catalysts and the degradation mechanisms of contaminants in ferrite/PMS system were also evaluated.The characterization results demonstrated that NiFe2O4 prepared by hydrothermal method belongs to spherical spinel ferrite with high purity.The particles have relatively good magnetic property with a saturation magnetization of 68.9 emu/g.The isoelectric point of the as-prepared NiFe2O4 is located at pH = 7.64.On the other hand,EGCG-Fe3O4 prepared by hydrothermal-ultrasound method also appears regularly spherical.TEM,FTIR,and XRD results indicated that EGCG was coated on the surface of Fe3O4,and the isoelectric point of EGCG-Fe3O4 is located at pH = 1.48.Sequences of bench experiments were conducted to investigate the performance of the two as-prepared catalysts.The results indicated that the dosages of oxidant and catalysts exhibit positive correlation with the removal of target contaminants,whilst the removal rate increases with the decrease of initial concentration of contaminants.The optimal initial pH of the system is determined by the isoelectric point of the catalysts,so the optimal pH were observed at 7.64 and 1.48 for NiFe2O4 and EGCG-Fe3O4,respectively.To evaluate the catalytic performance of these two catalysts in actual waters,humic acid and anion ions were added to simulate the actual water.The results showed that the presence of both humic acid and anion ions inhibited the removal rate of contaminants by ferrite/PMS system.The inhibition rate increases along with the concentration of humic acid,and the degree of inhibition of different anions abiding from strong to weak by the following order:Cl->PO43->CO32-.The preliminary mechanisms of ferrite/PMS system were also determined.Hydroxyl radical and sulfate radical were identified to be responsible for contaminants degradation and sulfate radical made the predominant contribution in this study.EGCG-Fe3O4/PMS system showed a more complicated catalytic mechanism,so XPS was used to characterize EGCG-Fe3O4 before and after reaction.Besides,HPLC/MS/MS was used to determine the primary intermediates of the two contaminants,and possible pathways were proposed.Three intermediates of OXC(C15H12N2O3,C15H10N2O3,C15H10N2O4)and six intermediates of diuron(C7H9ClN2O,C7H9ClN2O2,C7H7ClN2O2,C7H9Cl2N2O2,C7H9ClN2O,C7H7Cl2N2O2)were detected.Overall,compared to other common catalysts,the as-prepared catalysts in this study(NiFe2O4 and EGCG-Fe3O4),not only present higher catalytic efficiency for target contaminants,but can be easily separate to reuse with external magnetic.Therefore,the as-prepared catalysts are deemed as potential alternatives in water treatment.