Efficient degradation of carbamazepine by electro-Fenton system without any extra oxidant in the presence of molybdate: The role of slow release of iron ions

Abstract In this study, the removal efficiency of carbamazepine (CBZ) was significantly improved in an electro-Fenton system without any extra oxidant (e.g., O2 or H2O2) in the presence of sodium molybdate (EF-Na2MoO4 system). The slow release of iron ions of EF-Na2MoO4 system greatly reduced the generation of iron sludge and effectively promoted the utilization of iron ions. The pseudo-first-order rate constants (kobs) for CBZ removal by EF-Na2MoO4 process (0.0417 min−1) was much higher than those of sole electrolysis (0.0007 min−1) and EF-Na2SO4 systems (0.0044 min−1). Meanwhile, the total iron concentration in EF-Na2MoO4 process was 4.93 mg/L for 60 min, which was extremely lower than that of EF-Na2SO4 process (271.22 mg/L). Besides, the primary reactive species was proposed to be superoxide radical (O2 −), while hydroxyl radical ( OH) and MoO2(O2)22− acted as the secondary reactive species. Our work elucidated the possible mechanism that the slow release of iron ions promotes pollutants degradation.