Synergistic and efficient photocatalytic degradation of rhodamine B and tetracycline in wastewater based on novel S-scheme heterojunction phosphotungstic Acid@MIL-101(Cr).

Abstract

To efficiently treat rhodamine B (RhB) and tetracycline (TC) in wastewater, MIL-101(Cr) was prepared by hydrothermal method and encapsulated with phosphotungstic acid (H₃PW₁₂O₄₀, abbreviated as PTA) to form an S-scheme heterojunction PTA@MIL-101(Cr)-x (P@M-x, x = 50, 100, 150, 200). The experimental results showed that after 180 min under visible light at pH 7, the degradation rates of RhB and TC were 97.81% and 99.9%, respectively. Meanwhile, the cycling experiments have showed that the P@M-100 S-scheme heterojunction exhibits good stability. Density Functional Theory (DFT) calculations theoretically verified the experimental results and elucidated the electrons migrate to MIL-101(Cr) and hole enrichment on the PTA surface. It was also revealed that the P@M-x photocatalyst belongs to the S-scheme heterojunction. Moreover, •O₂^- and h⁺ had been identified as the main active constituents during the photocatalytic degradation process. The synergistic effect of MIL-101(Cr) and PTA enhances the visible light absorption of P@M-x S-scheme heterojunction, resulting in more efficient electron transfer ability and faster photoreaction rate, thereby improved its photocatalytic performance. This study provides a potential solution for addressing aromatic pollutants in water.