Photocatalytic activation of peroxymonosulfate by TiO2 anchored on cupper ferrite (TiO2@CuFe2O4) into 2,4-D degradation: Process feasibility, mechanism and pathway.

A thorough study of photo-oxidation efficiency of TiO2@CuFe2O4 dissociating peroxymonosulfate (PMS) is reported in detail. The origin of high catalytic activity was discussed as evidence by numerous controlled trials and several operational parameters. Based on quenching tests, possible mechanism and pathway of degradation were proposed. 2,4-dichlorophenoxyacetic acid (2,4-D) degradation in TiO2@CuFe2O4/UV/PMS system could abide pseudo-first-order kinetics. Moreover, reaction rate constant (Kobs) showed a linear increasing trend as PMS and catalyst concentrations increased. Over 97.2% of 2,4-D (20 mg/L) was degraded within 60 min at 0.3 mM PMS and 0.1 g/L TiO2@CuFe2O4. However, the water matrix species inhibited 2,4-D degradation to different amounts and the inhibiting effect was as follows: HCO3- > NO3-  > Cl- > SO42-. As-prepared catalyst showed a high ability of PMS activation, compared to other studied oxidants. Particularly, sulfate radicals were accounted for 2,4-D degradation in the catalytic oxidation reaction. TiO2@CuFe2O4 catalyst displayed the excellent recyclability and durability. Identification of intermediates and end-products brought about the conclusion that enhanced degradation involving dechlorination, dehydrogenation, hydroxylation, and ring cleavage, through SO4-, OH, O2- and holes attack during TiO2@CuFe2O4/PMS photocatalysis of 2,4-D. As conclusion, integration of TiO2, CuFe2O4 and UV light to efficient activation of PMS can be proposed as a successful and promising method to wastewater treatment effectively, because of the cogeneration of different reactive oxidizing species, simple and easy recovery of catalyst and good catalytic activity.