Novel Fe/N co-doping biochar based electro-Fenton catalytic membrane enabling enhanced tetracycline removal and self-cleaning performance

Designing a highly-active electro-Fenton (EF) catalytic membrane without the additional chemicals and iron sludge formation was a challenge for antibiotics treatment. In this study, we constructed Fe/N co-doping biochar (Fe-g-C3N4/biochar) based ultrafiltration membranes for degradation of tetracycline (a common antibiotic) and membrane fouling control under electro-assistance. The results showed that membranes presented high electro-Fenton catalytic activity because the presence of rich oxygen functional groups (high C–O/CO ratio) and nitrogen species (pyridinic N and pyrrolic N) promoted H2O2 generation and accelerated Fe(III)/Fe(II) cycle. Moreover, H3PO4 activation of biochar endowed the EF catalytic membrane with higher electrocatalytic activity, while it was opposite using biochar with higher pyrolysis temperature (600–700 °C). In particular, owing to the oxidative degradation by electro-generated •OH and •O2−, Fe-g-C3N4/ABC-600/Graphite/PVDF (600 represented the pyrolysis temperature) membrane presented 100% tetracycline removal within 0.749 min of residence time, excellent self-cleaning performance (flux recovery = 100%) at neutral pH and low energy consumption (0.199 W h/L) for the reclamation of synthetic municipal wastewater effluent. In addition, membrane self-cleaning mechanism was closely related to the synergy between partial mineralization and reduced fouling potential of foulants. Besides, the EF membrane also exhibited good reusability and stability, which was promising to apply in antibiotics removal.