Activation of peroxydisulfate by MIL-88A(Fe) under visible light toward tetracycline degradation: Effect of synthesis temperature on catalytic performance

Three different MIL-88A(Fe) samples (named as MIL-88A(Fe)-65, MIL-88A(Fe)-95 and MIL-88A(Fe)-125) were synthesized by a one-step hydrothermal method at the different synthesis temperature (65 °C, 95 °C and 125 °C) on the control, and they were adopted as high-efficiency catalysts for peroxydisulfate (PDS) activation to remove tetracycline (TC) from water under visible light irradiation. Various characterization methods (including XRD, BET surface area, UV–vis DRS, PL and XPS) indicate that synthesis temperature affects the crystal facet exposure, specific surface area, band gap energy, energy band position and ≡Fe2+/≡Fe3+ ratio of as-prepared MIL-88A(Fe). Activation of PDS by MIL-88A(Fe)-95 sample showed the highest efficiency for TC degradation under visible light mainly due to the photo-generated electrons on the conduction band of MIL-88A(Fe)-95 are more likely to be captured by O2 and PDS to produce reactive oxygen species. As-synthesized MIL-88A(Fe)-95 catalyst is stable and can be efficiently reused in the process of activating PDS to degrade TC. More importantly, TC degradation efficiency in real water matrices by MIL-88A(Fe)-95/PDS oxidation system is significantly higher than that in distilled water because bicarbonate ions in selected real water bodies can promote PDS activation, suggesting good practicability of this oxidation process. Mechanism analysis verifies that 1O2, O2•−, SO4•−, and •OH participate in TC degradation. This work laid a foundation for further developing the synthesis conditions to synthesize high-performance MIL-88A(Fe) applied in PS-AOPs.