Catalytic degradation of carbamazepine by metal organic frameworks (MOFs) derived magnetic catalyst Fe@PC in an electro-Fenton coupled membrane filtration system: Performance, pathway, and mechanism

The treatment of pharmaceutical and personal care products (abbreviated as PPCPs) have the problems of high energy consumption and low efficiency. Herein, an electro-Fenton (EF) coupled membrane filtration system was constructed to cost-efficiently degrade micromolecular carbamazepine (CBZ, a kind of PPCPs) from aquatic environment. Aqueous solution containing CBZ and the mixture of humic acid (HA, a kind of dissolved organic matters, with the molecular weight bigger than 400) was firstly filtered by polyvinylidene fluoride (PVDF)/carbon fiber cloth composite cathode membrane, which rejected HA while let CBZ pass through the membrane. The CBZ was then participated in the following EF process and decomposed with high efficiency. In the EF process, Fe-based metal–organic frameworks (Fe-MOFs) derived magnetic nanoconfinement catalyst, with iron nanoparticle as core and porous carbon (PC) as shell (abbreviated as magnetic Fe@PC), was prepared and applied to the EF process. The results indicated the rejection rates of the cathode membrane towards HA and CBZ were 69.91% and 3.35%, respectively, indicating most of the HA was rejected in the filtering process. In the EF process, the magnetic Fe@PC exhibited excellent catalytic degradation performance towards CBZ, with a total removal rate of 98.34%. Among which, the contributions of different processes including adsorption, electrodegradation and EF degradation were 0.90%, 4.97%, and 89.08%, respectively. Quenching test indicated both OH radical and O2– radical played crucial roles during the degradation process, which were generated by the in-situ decomposition of H2O2 in the coexistence of the magnetic Fe@PC. Based on the degradation intermediates of CBZ, four probable degradation pathways were proposed, and the most accessible pathway was also verified by theoretical calculations. The eco-toxicity assessment results showed most of the intermediate products were in lower toxicity than CBZ. Besides CBZ, the system also exhibited excellent degradation performance towards various kinds of PPCPs. This work indicated the EF coupled cathode membrane system is one of the efficient technologies in the removal of PPCPs in complex water environment.