Boosting electron transfer in Cu2O@PDA hollow fiber membranes to decompose oxytetracycline under visible light with persulfate

In this study, a polydopamine (PDA)-functional hollow fiber membrane (HFM) modified by Cu2O (Cu2O/PDAHFM) was developed via photocatalysis coupled persulfate activation for oxytetracycline (OTC) degradation. It is found that PDA facilitates electron transfer and therefore promotes OTC degradation, achieving 96% removal efficiency. The quenching experiments and electron paramagnetic resonance (EPR) experiments demonstrated that •SO4−, •OH, •O2−, 1O2, and h+ contributed to the OTC removal. Based on intermediates identified by liquid chromatograph mass spectrometer (LC-MS), three possible degradation pathways of OTC were proposed. The toxicity of intermediates was evaluated by using Toxicity Estimation Software Tool (T.E.S.T.). Moreover, the Cu2O/PDAHFM can achieve more than 80% removal of OTC after 6 cycles, demonstrating the reusability of the catalyst. In addition, flow reactors with two types of membrane modules for continuous wastewater were constructed, and computational fluid dynamics (CFD) was used to simulate the mass transfer and degradation processes to compare the two reactors for degrading contaminants. This work provides deep insight into the mechanisms of photocatalysis coupled with persulfate activation for OTC degradation and an alternative method for designing wastewater treatment devices.