S-doped MIL-53 as efficient heterogeneous electro-Fenton catalyst for degradation of sulfamethazine at circumneutral pH
The reduced S-modified MIL-53(Fe) was prepared by sulfurizing MIL-53(Fe) at low temperature, which was an efficient electro-Fenton catalyst at wide pH range (3–9) for sulfamethazine (SMT) degradation. The best temperature and MIL-53(Fe)/S ratio were 350 °C and 1:2, at which the BET surface area was much enlarged. The MIL-53(Fe) surface was etched by S to many 2D nanosheets with the thickness of ~50 nm, while S 2–2 replaced OH - to coordinate with Fe 2+ and increased the Fe 2+ content, which improved the catalytic performance. Even at initial pH of 7.0, the SMT removal was 95.8%, and the rate constant ( k ) in the Hetero-EF process was 16-folds of that in the Homo-EF process. The turnover frequency (TOF d ) value of MIL-53(Fe)/S(1:2)−350 was 0.48 L g −1 min −1 , which was 6.8 times that of commercial FeS 2 . The S 2–2 in catalyst adjusted the pH superfast, and promoted the generation of Fe 2+ and thus efficiently activating H 2 O 2 to form surface · OH, which was verified to be the main radical by EPR and radical scavenger experiments. This catalyst showed promising prospect for environmental application and could be regenerated by sulfidation method. S-doped MIL-53(Fe) was an excellent pH regulator, thus promoting promising application in Hetero-EF processes.
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