Efficient photo-degradation of BPA in textile wastewater assisted by primitive carbonate: The exceptional contribution of PMS in magnetic Cu0-CuFe2O4@TpPzDa COFs S-scheme heterojunction

Abstract

Herein, the magnetic core Cu0-CuFe2O4 was rationally embedded into a donor-acceptor (D-A) COFs shell composed of pyrazine-2,5-diamine (PzDa) and 2, 4, 6-triformylphloroglucinol (Tp) to form Cu0-CuFe2O4@TpPzDa S-scheme heterojunction for photo-degradation of BPA in textile wastewater. However, the photocatalytic performance of Cu0-CuFe2O4@TpPzDa was almost completely annihilated (the degradation efficiency of BPA remained only 5%) due to the adverse effects of the coordination between the interfacial Cu2+ in Cu0-CuFe2O4 core with the organic units in TpPzDa shell. Interestingly, when PMS was introduced, the Cu0-CuFe2O4@TpPzDa/vis system was reactivated to achieve 100% degradation of BPA (20 mg/L) with a degradation rate constant of 0.1672 min−1. Series of experiments and DFT calculations revealed exceptional contributions of PMS. It may not only coordinate with Cu2+ to positively revise the band structure and recover the D-A charge transfer within TpPzDa, moreover, the adsorption of PMS on pyrazine (PzDa) strongly minimized the exciton binding energy. The promoted electron-hole separation of TpPzDa, as well as facilitated S-scheme charge transfer within Cu0-CuFe2O4@TpPzDa, led to the generation of more active species h+, O2•− and 1O2. In addition, the primitive carbonate commonly co-existing in textile wastewater would further protect Cu0 from oxidation, ensuring that the emphasized electron bridge role of Cu0, which further accelerated the photo-degradation kinetic of BPA to 0.2189 min−1. This property, along with the convenient magnetic separation ability and remarkable stability inherited from the core and COFs-shell, offers a great opportunity for BPA degradation in line with the concept of “treating waste with waste”.