Degradation Of Antibiotic Norfloxacin Research Articles

Improving photocatalytic activity by construction of immobilized Z-scheme CdS/Au/TiO2 nanobelt photocatalyst for eliminating norfloxacin from water

To improve the photocatalytic activity of TiO2 NBs under irradiation of solar light, an immobilized Z-scheme composite photocatalyst CdS/Au/TiO2 NBs has been constructed. For the unique architectures, the TiO2 NBs provide more absorption and reaction sites, the CdS nanoparticles enhance overall light harvesting, and Au acts as the electron transfer mediator, promoting the interfacial charge transfer and efficient separation of electrons and holes. The morphology, elements, crystal structure, optical and photoelectrochemical properties, and photocatalytic activity of CdS/Au/TiO2 NBs were characterized. Results showed that CdS/Au/TiO2 NBs possesses higher photocatalytic activity toward the degradation of antibiotic norfloxacin under irradiation of simulated sunlight, which is attributed to the synergetic interaction of increased light absorption and separation of photogenerated electrons and holes. Besides, the degradation of norfloxacin was promoted by HCO3−, but inhibited by NO3− and Cl−. The radicals trapping experiments proved that superoxide radicals (O2−) was the dominating active species during the photocatalysis process. The photocatalytic degradation products of norfloxacin was analyzed, and nine intermediates were identified. Moreover, the photocatalytic degradation mechanism and photostability of CdS/Au/TiO2 NBs were analyzed in detail. The matched energy levels and unique ternary Z-scheme design are the key for improved photocatalytic activity. The deactivation of CdS/Au/TiO2 NBs after recycles mainly due to the release of CdS by photocorrosion and the loss of deposited Au.

Synthetic Mn(III) porphyrins as biomimetic catalysts of CYP450: Degradation of antibiotic norfloxacin in aqueous medium

Norfloxacin (NOR) is a synthetic broad-spectrum fluoroquinolone antibiotic classified as an emerging contaminant. Here, we investigate Mn(III) porphyrin-catalyzed NOR degradation using peroxides or peracids (H2O2, t-BuOOH, or Oxone®) as oxidants. We evaluate three Mn(III) porphyrins: the 1st-generation tetraphenylporphyrin and 2nd -generation porphyrins bearing halogen atoms at the ortho-positions of the porphyrin macrocycle meso-aryl groups. Experiments were carried out in aqueous medium under mild conditions. NOR degradation was 67%. Products were proposed by mass spectrometry (MS) analysis. Oxone® was the best oxidant for NOR degradation despite its possible decomposition in the reaction medium. The second-generation Mn(III) porphyrins were more resistant than the first-generation Mn(III) porphyrin, indicating that the bulky groups introduced into the porphyrin macrocycle meso-aryl groups led to more robust catalysts. The degradation products did not present cytotoxic behavior under the employed conditions. In conclusion, Mn(III) porphyrin-catalyzed NOR degradation is a promising strategy to degrade fluoroquinolones and other pollutants.

Degradation of norfloxacin by CoFe2O4-GO composite coupled with peroxymonosulfate: A comparative study and mechanistic consideration

Magnetic cobalt ferrite (CoFe2O4) was extensively investigated for the activation of peroxymonosulfate (PMS) to generate sulfate radicals. In this study, the CoFe2O4 nanoparticles were uniformly decorated on graphene oxide (GO) nanosheet. According to the large surface area and more surface oxygen species, the CoFe2O4-GO composite exhibited much better efficiency than CoFe2O4 for the generation of sulfate radicals. The degradation of antibiotic norfloxacin (NOR) by CoFe2O4-GO coupled with PMS was comprehensively investigated. Through radical quenching study and electron paramagnetic resonance (EPR) analysis, the active radical species were elucidated. The underlying mechanism was then discussed based on the detected radicals and X-ray photoelectron spectroscopy (XPS) observations. It was revealed that the NOR degradation by CoFe2O4-GO system was dominated by a nonradical process rather than a radical process. The surface oxygen species at defective sites of GO played a critical role in the degradation process. Finally, the developed CoFe2O4-GO composite showed a good potential for the remediation of NOR polluted natural river/lake water.

Degradation of antibiotic norfloxacin in aqueous solution using advanced oxidation processes (AOPs)—A comparative study

The consumption of antibiotics in today’s world has increased tremendously and as such they are frequently found in effluents, sewage treatment plants, hospital waste water and surface water like lakes and rivers. The aquatic organisms are severely affected due to the presence of these antibiotics. Moreover, as these antibiotics are mostly recalcitrant, biological treatment methods are not feasible. Hence, the present study is focused on the treatment of one such antibiotic called norfloxacin using advanced oxidation processes (AOPs). The parameters considered in this study include the effect of UV, initial pH of the recalcitrant solution, UV/H2O2, Fenton, photo-Fenton process, UV/TiO2 and UV/TiO2 immobilization with glass beads. Among all the processes studied, photo-Fenton process has found to be effective and removed 96% of the norfloxacin. The optimum conditions obtained for the maximum degradation with photo-Fenton process are: pH 3, H2O2 concentration of 200 mg/L and iron concentration of 30 mg/L, for an initial drug concentration of 150 ppm.

Degradation of antibiotic norfloxacin in aqueous solution by visible-light-mediated C-TiO2 photocatalysis

A visible-light-mediated C-TiO2 photocatalytic process (Vis/C-TiO2) was employed to degrade antibiotic norfloxacin. The influences of catalyst dosage, initial probe compound concentration and solution pH levels on the decay performance and reaction kinetics were investigated and optimized. Based on the experimental results, an equation was established to predict the observed rate constant under neutral pH. In addition, the decay rate was accelerated under weak alkali in the presence of moderate OH− anions. Hydroxyl radical was confirmed to play a major role in the Vis/TiO2 process, where in the presence of OH quencher and electron acceptor, retardation and improvement were found respectively. Furthermore, an original schematic diagram describing the surface property of C-TiO2 was built and further verified, in which, NH4+ cations normally served as hole scavengers showed a negligible effect because the adsorbed OH− formed a barrier for NH4+ ions to approach the holes, and the F− anions presented a significant suppression on norfloxacin decay due to the formation of hydrogen bond (OH⋯F) around the C-TiO2 surface. Besides, the recycling and sedimentation tests justified that the Vis/C-TiO2 process is a cost-effective and feasible way for wastewater treatment.