Enhancing peroxymonosulfate activation performance of MIL-101(Fe) for efficient dyes degradation: Co-modification of metal-doping and thermal activation

Background

MIL-101(Fe), an eco-friendly catalyst in sulfate radical based advanced oxidation processes (SR-AOPs) for treating textile wastewater, faces limitations in peroxymonosulfate (PMS) activation due to its fully coordinatively saturated state and the slow conversion of Fe^III to Fe^II.

Methods

Three co-modified MIL-101(Fe) catalysts of CUS-Fe^Ⅱ-MIL-101(Fe), CUS-Cu^Ⅱ-MIL-101(Fe) and CUS-Co^Ⅱ-MIL-101(Fe) were successfully synthesized by combining metal-doping (Fe²⁺, Cu²⁺ and Co²⁺) and thermal activation (300 °C). The physiochemical properties of as-synthesized catalysts were characterized by powder X-ray diffraction (PXRD), field emission electron microscope coupled with energy dispersive spectroscopy (FESEM-EDS), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FTIR). The effects of catalyst dosage and type, PMS concentration, solution pH and co-existing anions on methylene blue (MB) degradation in SR-AOPs systems were analyzed, and the degradation mechanisms was discussed by quenching tests with scavengers of Methanol (MeOH), tertbutyl alcohol (TBA), p-benzoquinone (BQ) and l-histidine (L-his).

Significant findings

Compared to the MB degradation efficiency of original MIL-101(Fe) (92.5 %), three co-modified catalysts shown higher MB degradation efficiencies of 97.5 %, 98.1 % and an outstanding 100 %, respectively. Free radicals quenching tests indicated that SO₄^•− and •OH played key roles in MB degradation mechanism. Promisingly, the three catalysts also demonstrated high degradation efficiencies above 94.0 % for four additional dyes.