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Effects of water matrix components on degradation efficiency and pathways of antibiotic metronidazole by UV/TiO2 photocatalysis
摘要： In this study, the effects of water matrix components such as anions (Cl-, SO4 2-, NO3 -, HCO3 -, and H2PO4 -); cations (Ca2+, Mg2+, and Fe3+); natural organic matter (humic acid); and pharmaceutical excipient (glucose) on the photocatalytic degradation of metronidazole (MNZ) by UV/TiO2 were investigated. Degradation of MNZ noticeably decreased in the presence of H2PO4 -, Fe3+, and humic acid (HA). However, the addition of glucose tripled the rate of MNZ degradation. The transformation products formed during photocatalysis were detected and identified using Waters UPLC-QTof/MS (ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry) and UPLC-MS/MS (ultra-performance liquid chromatography–tandem mass spectrometry) instruments. The enhanced degradation of MNZ in the presence of glucose was due to the side reactions of MNZ and its intermediates with other organics released when glucose was degraded. HA could activate charge transfer steps, resulting in different photodegradation products. Iron(III) ions competed with MNZ under light adsorption and reacted with organic intermediates, which hindered MNZ degradation. The presence of H2PO4 - ions seemed to have no effect on the degradation pathways of MNZ but only slowed down the removal of MNZ and its intermediates by interacting with TiO2. These results indicate that the presence of water matrix components significantly changed the degradation pathways and hence affected the degradation efficiency.
关键词： Photocatalysis,Metronidazole,Titanium dioxide,Water matrix components,Degradation pathways
更新于2025-09-23 15:21:01
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Carbon quantum dots as a fluorophore for “inner filter effect” detection of metronidazole in pharmaceutical preparations
摘要： With houttuynia cordata as carbon source, photoluminescent carbon quantum dots (CDs) were obtained via a one-step hydrothermal procedure. The absorption band of metronidazole (MNZ, maximum absorption wavelength at 319 nm) can well overlap with the excitation bands of CDs (maximum excitation wavelength at 320 nm). A fluorescent approach has been developed for detection of MNZ based on the inner filter effect (IFE), in which as-prepared CDs act as an IFE fluorophore and the MNZ as an IFE absorber. We have investigated the mechanism of quenching the fluorescence of CDs and found that the IFE leads to an exponential decay in fluorescence intensity of CDs with increasing concentration of MNZ, but showed a good linear relationship (R2 ? 0.9930) between ln(F0/F) with the concentration of MNZ in the range of 3.3 (cid:2) 10(cid:3)6 to 2.4 (cid:2) 10(cid:3)4 mol L(cid:3)1. Due to the absence of surface modification of the CDs or establishing any covalent linking between the absorber (MNZ) and the fluorophore (CDs), the developed method is simple, rapid, low-cost and less time-consuming. Meanwhile, it possesses a higher sensitivity, wider linear range, and satisfactory selectivity and has potential application for detection of MNZ in pharmaceutical preparations.
关键词： metronidazole,carbon quantum dots,inner filter effect,pharmaceutical preparations,fluorescence detection
更新于2025-09-16 10:30:52
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Architecturing CoTiO3 overlayer on nanosheets-assembled hierarchical TiO2 nanospheres as a highly active and robust catalyst for peroxymonosulfate activation and metronidazole degradation
摘要： Catalytic performance of a heterogeneous cobalt-based catalyst for advanced oxidative process (AOP) correlates tightly with its structure and composition. The main objective of this study is to maximize the utilization and accessibility of cobalt sites while enhancing their activity and stability through rational structural and composition designs, and thus to achieve an excellent performance for heterogeneous peroxymonosulfate (PMS) activation. To this end, a novel CoTiO3/TiO2 composite (CTT), composed of CoTiO3 overlayer on nanosheets-assembled hierarchical TiO2 nanospheres, was elaborately designed and synthesized. The resulting CTT possessed certain features including CoTiO3-rich surface, large surface area (114.8 m2 g?1), and highly open porous channels, which afforded sufficient accessible active sites against undesirable particle agglomeration and shedding. Moreover, cobalt sites of CTT exhibited a higher activity toward PMS than those of Co3O4 due to the composition-induced distinct adsorption nature, easy electron transfer, and strong bond-weakening ability. Benefitting from the unique combination of structural and compositional advantages, CTT manifested remarkable catalytic efficiency, low cobalt leaching (0.078 mg L?1), and excellent reusability in activation of PMS for degradation of the emerging antibiotic pollutant metronidazole (MNZ). The potential degradation pathway for MNZ and the catalytic mechanism were further elucidated. The design strategy proposed in this study may provide a new opportunity for future development of high-performance heterogeneous cobalt-based catalysts in remediation of aquatic environment.
关键词： Heterogeneous cobalt-based catalyst,CoTiO3-rich surface,Metronidazole,Peroxymonosulfate activation,Catalytic degradation,Nanosheets-assembled hierarchical structure
更新于2025-09-12 10:27:22