Fluidized ZnO@BCFPs Particle Electrodes for Efficient Degradation and Detoxification of Metronidazole in 3D Electro-Peroxone Process

A novel material of self-shaped ZnO-embedded biomass carbon foam pellets (ZnO@BCFPs) was successfully synthesized and used as fluidized particle electrodes in three-dimensional (3D) electro-peroxone systems for metronidazole degradation. Compared with 3D and 2D + O3 systems, the energy consumption was greatly reduced and the removal efficiencies of metronidazole were improved in the 3D + O3 system. The degradation rate constants increased from 0.0369 min−1 and 0.0337 min−1 to 0.0553 min−1, respectively. The removal efficiencies of metronidazole and total organic carbon reached 100% and 50.5% within 60 min under optimal conditions. It indicated that adding ZnO@BCFPs particle electrodes was beneficial to simultaneous adsorption and degradation of metronidazole due to improving mass transfer of metronidazole and forming numerous tiny electrolytic cells. In addition, the process of metronidazole degradation in 3D electro-peroxone systems involved hydroxyethyl cleavage, hydroxylation, nitro-reduction, N-denitrification and ring-opening. The active species of ·OH and ·O2− played an important role. Furthermore, the acute toxicity LD50 and the bioconcentration factor of intermediate products decreased with the increasing reaction time.