In situ synthesis of oxygen-doped carbon quantum dots embedded in MIL-53(Fe) for efficient degradation of oxytetracycline.

Introducing carbon quantum dots (CQDs) into photocatalysts is believed to boost the charge transfer rate and reduce charge complexation. Doping heteroatoms such as N, S, or P enable CQDs to have an uplifting electron transfer capability. However, the application of oxygen-doped CQDs to improve the performance of photocatalysts has rarely been reported. Herein, a type of carbon-oxygen quantum dots (COQDs) was in situ embedded into MIL-53(Fe) to aid peroxydisulfate (PDS)-activated degradation of oxytetracycline (OTC) under visible light irradiation. The successful embedding of COQDs was confirmed by XRD, FT-IR, XPS, SEM, and TEM techniques. Photoelectrochemical testing confirmed its better performance. The prepared COQDs1/MIL-53(Fe) showed 88.2% decomposition efficiency of OTC in 60 min, which was 1.45 times higher than that of pure MIL-53(Fe). In addition, the performance of the material was tested at different pH, OTC concentrations, catalyst dosing, and PDS dosing. It was also subjected to cyclic testing to check stability. Moreover, free radical trapping experiments and electron paramagnetic resonance were conducted to explore the possible OTC deterioration mechanism. Our work provides a new idea for the development of MOFs for water treatment and remediation.

Removal of oxytetracycline from water by S-doped MIL-53(Fe): Synergistic effect of surface adsorption and persulfate activation.

In this study, a novel catalyst based on MIL-53(Fe) was synthesized and modified through sublimed sulfur (S-MIL-53(Fe)) to induce a synergistic effect of surface adsorption and persulfate activation. The S-doped modification not only increased the surface area but also accelerated the electron transfer process of the iron cycle. The performance of the newly synthesized S-MIL-53(Fe) adsorptive catalyst was evaluated by chemical adsorption and peroxydisulfate (PDS) activated removal of an emerging pollutants, oxytetracycline (OTC). The S-MIL-53(Fe) adsorptive catalyst was able to adsorb 61.7% of OTC after 120 min, and the removal efficiency reached 84.8% within 5 min after PDS dosing. The boosting effect of sulfur on the system was confirmed by characterization analysis and experimental testing. Even after 7 cycles, the removal efficiency of S-MIL-53(Fe) (69.0%) for OTC remained superior to that of pure MIL-53(Fe) (25.1%). Additionally, the adsorption kinetics and adsorption isotherm model of the material were investigated. The possible OTC degrading process was proposed based on radical quenching and electron paramagnetic resonance (EPR). This study provides a feasible way to fabricate an S-doped MIL-53(Fe) adsorptive catalyst for the remediation of antibiotics-containing wastewater.

Highly efficient removal of oxytetracycline using activated magnetic MIL-101(Fe)/γ-Fe2O3 heterojunction catalyst.

A novel magnetic nanocomposite MIL-101(Fe)/γ-Fe2O3 was synthesized by hydrothermal method. The physical structure and chemical property of the as-obtained magnetic nanocomposite was characterized. The ability of MIL-101(Fe)/γ-Fe2O3 to promote photo-assisted peroxydisulfate (PDS) activation was investigated by using oxytetracycline (OTC) as the target pollutant. The results showed that the composite with a FeCl3•6H2O: γ-Fe2O3 mass ratio of 10:1 exhibited the highest degradation efficiency (up to 91.2%). Influencing factors such as pH, catalyst dosage, PDS concentration and OTC concentration on the catalytic performance of MIL-101(Fe)/γ-Fe2O3 were also investigated to determine the optimum conditions. More importantly, the MIL-101(Fe)/γ-Fe2O3 can be magnetically recovered and reused for 4 cycles. Based on radical quenching and electron spin resonance (ESR), the possible degradation mechanism of OTC in photo-assisted PDS activation (PPA) system was proposed. This research provided novel insights for the design and preparation of a new type of magnetic Fe-MOFs for environmental remediation.

Degradation of oxytetracycline by magnetic MOFs heterojunction photocatalyst with persulfate: high stability and wide range.

Photocatalysis with persulfate (PS) is an effective method for the degradation of degrading organic pollutants. In this study, Fe3O4/MIL-101(Fe), a magnetic heterojunction photocatalyst, was produced using a hydrothermal method. The material coupled with PS exhibited excellent removal efficiency for oxytetracycline (OTC) (87.1%, 1 h). And it has a wide range of applications, with good removal efficiency for OTC concentrations of 30 to 70 mg/L and pH values of 3 to 9. •SO4- and •OH played a major role in the OTC removal reaction and there was an Fe(III)/Fe(II) cycle during the reaction. With excellent stability and recoverability, the OTC removal efficiency decreased by only 4.29% after four cycles, and the Fe leaching did not exceed 0.035 mg/L per cycle. This study provides significant insights into the removal of organic pollutants from water bodies.