Photodegradation Of Norfloxacin Research Articles

Novel Br-doped Bi2WO6 photocatalyst for high-efficiency removal of norfloxacin: mechanism and photocatalytic activity.

In this work, the bismuth tungstate (Bi2WO6) photocatalyst was successfully prepared, and the pure Bi2WO6 was modified with Br (Br-Bi2WO6). The effects of different experimental conditions on the degradation of norfloxacin (NOR) solution under visible light were investigated. The Br-Bi2WO6 photocatalyst was characterized by FTIR, XRD, SEM, BET, XPS, DRS, EIS, and EPR. The results show that the Br-modified Bi2WO6 photocatalyst can effectively improve the photocatalytic performance. The best photocatalytic performance of Br-Bi2WO6 was observed when the doping amount of Br was 3%. The degradation percentage of norfloxacin can reach 94.67%. The presence of anions and cations (Cl-, SO42-, Ag+, and Cu2+) in the solution significantly inhibited the photocatalytic activity of 3%Br-Bi2WO6. The photocatalytic degradation of norfloxacin by 3%Br-Bi2WO6 was not greatly affected in the presence of HCO3- and NO3-. The characterization analysis showed that Br was successfully doped on the Bi2WO6 photocatalyst, and the original structure of Bi2WO6 was not destroyed by the addition of Br. Br doping increased the specific surface area of Bi2WO6 and decreased the band gap of Bi2WO6 resulting in a broader visible light absorption range. In addition, Br doping promoted the migration rate of photogenerated electron-hole pairs. The ·O2- and h+ played a major role in the photodegradation of norfloxacin, and the mechanism of photocatalytic degradation of norfloxacin by Br-Bi2WO6 was proposed.

Boosting visible-light-promoted photodegradation of norfloxacin by S-doped g-C3N4 grafted by NiS as robust photocatalytic heterojunctions

As a result of industrial expansion and ill-considered exploitation of resources, serious environmental issues have recently emerged that have led to damage to the ecosystem. In particular, antibiotics, such as norfloxacin (NOR) have emerged as highly hazardous contaminants resulting from the increased use of these drugs worldwide. Photocatalysis-based degradation using heterojunctions has become almost the only way to permanently and eco-friendly degrade these pollutants. Herein, noble metal-free nanohybrids composed of S-doped g-C3N4 grafted by NiS (denoted as NiS/SCN) have been fabricated via hydrothermal and one-step polymerization (at 550 °C) procedures. The photocatalytic activity of 3 %NiS/SCN photocatalyst was almost 6- and 20-times as high as SCN and NiS, respectively, achieving 96.2 % NOR degradation within 90 min. The recommended photocarriers transfer pathway was suggested and supported experimentally. Considerably, loading a small amount of NiS cocatalyst over S-doped g-C3N4 boosted performance in addition to efficient reusability. This increased photocatalytic activity can be attributed to the fact that doping g-C3N4 with sulfur can reduce the bandgap and thus broaden the response range to visible-light, and the effective effect of Schottky junction can significantly improve the separation rate of electron-hole pairs. Accordingly, the constructed NiS/SCN nanocomposites are potential candidates for photocatalysis processes, particularly visible-light-induced degradation of organic pollutants.

Cornstalk hydrochar produced by phosphoric acid-assisted hydrothermal carbonization for effective adsorption and photodegradation of norfloxacin

Hydrochars have been widely applied in removing pollutants from aqueous solutions. In this study, hydrochars synthesized by H3PO4-assisted hydrothermal carbonization (HC-xPs) were used to remove norfloxacin (NOR) from water through synergistic adsorption and photodegradation. HC-xPs showed the morphology of carbon microspheres with an average diameter of 0.3 μm. The specific surface area of the hydrochar carbonized with 5 mol/L H3PO4 (HC-5P) was 11.2 times higher than that of the pristine hydrochar (HC). Furthermore, phosphorus-containing functional groups were introduced to HC-5P, beneficial to its adsorption of NOR. The highest NOR adsorption was achieved on HC-5P with the maximum Langmuir capacity of 69.1 mg g−1, owing to multiple mechanisms including electrostatic effects, π-π interactions, hydrophobic interactions, and hydrogen bonding. Compared with HC, HC-5P also demonstrated increased visible light absorption capacity. The first-order rate constant of HC-5P on combined adsorption and photodegradation of NOR was 12.0 times of HC. The photodegradation intermediates were identified by HPLC-MS to understand NOR degradation pathways. This work can be extended to the preparation of low-cost and highly efficient hydrochars for adsorption and photodegradation of pollutants in water.

Photodegradation for different dissociated species of norfloxacin and ofloxacin in water ice under solar irradiation

Ice is an important medium that regulates the transformation of organic contaminants. Nonetheless, photodegradation of emerging fluoroquinolone (FQ) antibiotics in the ice, particularly those with varying dissociated species, remains inadequately explored. In this study, the photodegradation of norfloxacin (NOR) and ofloxacin (OFL) in different dissociated species in water ice were investigated. Results indicated that the quantum yield of the zwitterion for NOR in the ice was 1.7–5.0 times higher than that of the cation, and 1.3 times higher than that of the anion. The quantum yield of the zwitterion for OFL in the ice was 2.5–3.4 times higher than that of the cation, and 1.4 times higher than that of the anion. The degradation pathways of NOR and OFL with different dissociated species depended on their molecular structure. Most products possessed lower developmental toxicity than parent NOR and OFL, respectively. OFL showed a higher inhibitory rate of Escherichia coli activity at the initial time of photodegradation, which was higher than that of NOR. This study offers novel insights into the impact of dissociated species on the photodegradation of FQs in ice and contributes to understanding the environmental behavior of fluorinated pharmaceuticals in the cryosphere.

Fabrication of Z-scheme ZnO/g-C3N4 heterojunction modified by silver nanoparticles for photocatalytic removal of Norfloxacin and Rhodamine B

A novel ternary photocatalyst with a Z-scheme heterojunction was successfully synthesized through the deposition of Ag nanoparticles onto the surface of a ZnO/g-C3N4 composite. The prepared photocatalysts were characterized by XRD, FT-IR, XPS, HRSEM, TEM, DRS, PL, EIS, TPC, and M-S. The photocatalytic performance of the as-synthesized photocatalysts was systematically investigated through the photodegradation of norfloxacin (NOR) and rhodamine B (RhB) under visible light irradiation. The photodegradation efficiency of 5% Ag/ZnO/g-C3N4 (5AZCN) composite photocatalyst reached 86.7% (480 min) and 98.0% (60 min) for NOR and RhB, respectively. Moreover, the apparent rate constants of the 5AZCN composite photocatalysts for NOR and RhB were found to be 3.4 and 22.2 times higher than that of the ZCN composite photocatalysts, respectively. The significantly enhanced photocatalytic performance was ascribed to the widened range of visible light response and the efficient separation and migration of carriers facilitated by the introduction of Ag nanoparticles that functioned as electron transfer mediators. Based on the free radicals quenching experiment and electron spin resonance (ESR) spectroscopy characterization, superoxide radicals (·O2−) were the main reactive species in the photodegradation process. Furthermore, the charge transfer process was proved to be a Z-scheme transfer mechanism. This work provides a promising approach to simply constructing novel efficient Z-scheme photocatalysts for the elimination of environmental pollutants.

Construction of dual Z-scheme V2O5/FeVO4/Fe2O3 photocatalytic system via in-situ synthesis for enhanced solar light-driven photocatalytic degradation of antibiotics and mechanism insight

A novel high-proportion dual Z-scheme V2O5/FeVO4/Fe2O3 photocatalyst was successfully constructed by in-situ synthesis strategy of solid phase V2O5 and Fe2O3, and applied within the photodegradation of norfloxacin in solution under simulated solar light. The photocatalytic activity of the ternary Z-scheme V2O5/FeVO4/Fe2O3 nanocomposite was estimated. A series of factors affecting the photocatalytic performance of V2O5/FeVO4/Fe2O3 were investigated. The possible mechanism on the ternary dual Z-scheme V2O5/FeVO4/Fe2O3 photocatalytic system was proposed. The results reveal that the obtained FeVO4 nanoparticles exist between V2O5 and Fe2O3 nanoparticles, and that the three nanoparticles can coexist with two blurred contact interfaces, which promotes electron transmission and high separation efficiency of electron-hole pairs. The Z-scheme V2O5/FeVO4/Fe2O3 system exhibits superior photocatalytic activity, due to the formation of the high-proportion dual Z-scheme photocatalyst, as well as strong redox capacity from its two valence band oxidation surfaces. Moreover, V2O5/FeVO4/Fe2O3 has preeminent stability after five cycles, and photo-generated hole plays a major role in photocatalytic degradation. It is expected that the dual Z-scheme V2O5/FeVO4/Fe2O3 photocatalytic technology holds great application prospects in the construction of effective photocatalysts and the treatment of antibiotics in water and wastewater utilizing solar energy.

Construction of zinc-oxygen double vacancies BiOCl/ZnS Z-scheme heterojunction and photocatalytic degradation of norfloxacin

Defect (vacancy) engineering can modulate the catalyst surface atoms and electrons, which is a low-cost and effective modification strategy for Z-scheme heterojunction. In this paper, metal and non-metal double vacancies (VZn+O) Z-scheme heterojunction photocatalysts (BiOCl/ZnS−VZn+O) were synthesized for the degradation of norfloxacin (NOR) for the first time. The results show that the built-in electric field of BiOCl/ZnS−VZn+O catalyst induces the directional migration of photogenerated carriers, which greatly improves the carrier migration and separation efficiency. The introduced nonmetallic (O) vacancies can lower the conduction band of BiOCl, while the metallic (Zn) vacancies can enhance the valence band of ZnS. Due to the synergistic efficiency formed by the double vacancies and Z-scheme heterojunction, BiOCl/ZnS−VZn+O showed excellent performance in photodegradation of NOR (97.9% degradation rate of 20 mg/L NOR in 50 min photodegradation). In addition, the mechanism of action, intermediates and degradation pathways of photodegradation were discussed in detail.

Pompon-like Bi2WO6 hierarchical nanostructures: preparation and their application in photodegradation of norfloxacin and difloxacin hydrochloride

Pompon-like Bi2WO6 hierarchical nanostructures: preparation and their application in photodegradation of norfloxacin and difloxacin hydrochloride

Microwave-assisted method synthesis of Ag/CNQDs/g-C3N4 with excellent photocatalytic activity for the degradation of norfloxacin

In this paper, through microwave-assisted process combined with a chemical reduction method, the novel ternary photocatalysts Ag/CNQDs/g-C3N4 composites were prepared successfully for the norfloxacin removal. The Ag/CNQDs/g-C3N4 composites possessed the suitable specific surface area, better crystal structure and excellent stability. Furthermore, forming an internal electric field, the isotype heterojunction structure between CNQDs and g-C3N4 could promote effective carrier separation. Unexpectedly, the Ag/CNQDs/g-C3N4 with the synergistic effect of the up-conversion fluorescent properties of CNQDs and the surface plasmon resonance (SPR) effect of Ag NPs, showed the excellent photocatalytic property. As a result, the optimized Ag/CNQDs/g-C3N4 composites exhibit excellent photocatalytic degradation of norfloxacin under visible light irradiation. The norfloxacin removal rate was reached almost 100% within 120 min, and the quasi-first-order kinetic constant (k) value was 0.04233 min−1, which was more than 4 times higher than that of g-C3N4. Moreover, the·O2- and h+ were the dominant active species involved in the photo-degradation of norfloxacin. In the mineralization process, the toxicity of norfloxacin degradation intermediates gradually reduced. This work not only provides new insights for the design of g-C3N4-based composites for photocatalysis applications, but also affords an effective strategy in the environmental remediation field.

Photodegradation of norfloxacin adsorbed on clay and carbon-clay nanomaterials: an evaluation based on antimicrobial tests

Photodegradation of norfloxacin adsorbed on clay and carbon-clay nanomaterials: an evaluation based on antimicrobial tests

Photodegradation of norfloxacin in ice: Role of the fluorine substituent

Ice is an important medium in cold regions, because it regulates the environmental behaviors and the fate of pollutants. The photodegradation of fluoroquinolone (FQ) antibiotics as emerging contaminants of concern in ice remains poorly understood. Here, the photodegradation of fluorine-containing norfloxacin (NOR) as one model of FQs in ice formed from freezing solutions was investigated. Pipemidic acid (PPA) as a structural analogue of NOR was selected to compare the effect of molecular structure on the antibiotic photodegradation in the ice. Results suggested that the photodegradation rate constant of NOR in ice relative to pure water increased by 40.0%. Both the absorbance in the absorption spectra and quantum yields of NOR in ice over water increased by 1.4 times. Direct photodegradation mainly caused the defluorination of NOR, which was more important than cleavage and oxidation of the piperazine ring by self-sensitized photooxidation in ice. The defluorination rate of NOR in the ice relative to water increased by about 12.7%. The fluorine substituent played a more important role in the NOR photodegradation in the ice, resulting in a 1.6-fold increase in the photodegradation rate constant of NOR relative to PPA. This work provides a new insight into the role of fluorine substituents in the photodegradation of fluorinated pharmaceuticals in cold regions.

Constructing 2D/2D N-ZnO/g-C3N4 S-scheme heterojunction: Efficient photocatalytic performance for norfloxacin degradation

The low separation efficiency of carriers limited the application of g-C3N4 (CN) in the photodegradation of fluoroquinolones antibiotics, and the construction of two-dimensional/two-dimensional (2D/2D) heterojunction was an effective strategy. In this paper, 2D/2D N-ZnO/CN S-scheme heterojunction composites (x NZCN, x was the mass ratio of ZIF-L/CN) were prepared by calcining ZIF-L/CN composites which were formed via ultrasonic-assisted electrostatic self-assembly method. The photodegradation efficiencies of Norfloxacin (NOR), enrofloxacin, levofloxacin, and ciprofloxacin reached more than 90% in 90 min by 15% NZCN/vis system. Moreover, the rate constant of 15% NZCN for photodegrading NOR was 4.15 times and 4.65 times higher than CN and N-ZnO, respectively. The efficient photocatalytic performance of 15% NZCN was attributed to the excellent light capture capacity and the effective migration and separation of carriers. The active species that worked in the photodegradation of NOR were dominated by holes and superoxide radicals. In addition, degradation pathways of NOR were proposed. This work enriched 2D/2D heterojunction engineering for CN, and provided a new possibility for combining 2D MOFs-derivatives with CN to solve the antibiotic pollution problem in the environment.

Research on Photodegradation of Norfloxacin by Modified Carbon Nitrogen Compounds

Photocatalysis is an economical and reliable method for degradation of pharmaceutical pollutants. Under mild conditions, the photocatalyst can absorb optical energy and accelerate the photo degradation of pollutants. As a new type of non-metallic semiconductor catalyst, graphite phase carbon nitride(g-C3N4) has many excellent properties such as low band gap, large specific surface area and so on. Norfloxacin (NOR) is a synthetic antibiotic with many good properties such as high antibacterial activity and low toxicity. Because of its wide application in medical treatment and animal breeding, it has caused great pollution to the environment. In this paper, the performance of g-C3N4 and the mechanism of photocatalytic degradation of NOR are analyzed. Several effective modification methods are described, and several problems that need to be solved in current research are put forward.

Construction of novel symmetric double Z-scheme BiFeO3/CuBi2O4/BaTiO3 photocatalyst with enhanced solar-light-driven photocatalytic performance for degradation of norfloxacin

A symmetric double Z-scheme BiFeO3/CuBi2O4/BaTiO3 with enhanced solar photocatalytic performance was fabricated, and employed in the photodegradation of norfloxacin. The photocatalytic performances of BiFeO3/CuBi2O4/BaTiO3, BiFeO3, CuBi2O4 and BaTiO3 were compared. Also, the mechanism on the symmetric double Z-scheme BiFeO3/CuBi2O4/BaTiO3 photocatalytic system was proposed. The results display that BiFeO3/CuBi2O4/BaTiO3 has more superior photocatalytic performance, which results from the construction of the symmetric double Z-scheme photocatalyst. Its light absorption range is extended to UV-vis and near-infrared (NIR) light, which effectively utilizes the whole solar light spectrum. Especially, the large VB oxidation surface of this composite photocatalyst promotes e--h+ separation and improves the oxidation-reduction ability. Also, BiFeO3/CuBi2O4/BaTiO3 can be recycled with superior stability for 5 cycles. Furthermore, in the photodegradation, the h+ and •OH play major roles, while the •O2− plays little role. Hence, the BiFeO3/CuBi2O4/BaTiO3/solar light technology has great application prospects in the treatment of contaminated wastewater with antibiotics.

Enhanced visible light photocatalytic performance with metal-doped Bi2WO6 for typical fluoroquinolones degradation: Efficiencies, pathways and mechanisms

To clarify the photocatalytic mechanisms of metal-doped Bi2WO6 for fluoroquinolones (FQs) degradation, the effects of the chemical characteristics of four metals, molar ratios of the doped metals, morphology of the catalysts, and electrostatic interactions on the degradation of norfloxacin (NOR) and ciprofloxacin (CIP) were evaluated under visible light irradiation. Experimental results implied that the doping of Mg2+, Fe3+, Zn2+ and Cu2+ dramatically improved the photodegradation of Bi2WO6 for NOR and CIP removal, in which 1% Mg/Bi2WO6 exhibited the highest degradation rate of 89.44% for NOR and 99.11% for CIP. Photodegradation of NOR fitted to the pseudo-first-order model (k1 value of 0.02576 min−1), whereas that of CIP be better described by pseudo-second-order model. Moreover, the two FQs photodegradation pathways and the possible intermediates were summarized. The mechanisms of the metal dopants for the enhancement of photocatalytic activity were attributed to its enhanced specific surface area, electrostatic absorption, as well as the significant photogeneration of ·O2− and h+. Also, the photocatalyst exhibited a high stability with 78.5% photocatalytic performance after four cycles of repeated usage.

One-pot controllable synthesis of BiOBr/β-Bi2O3 nanocomposites with enhanced photocatalytic degradation of norfloxacin under simulated solar irradiation

The low quantum yield and weak catalytic ability of bismuth oxyhalides retard their applications in photocatalytic degradation. To promote the performances of bismuth oxyhalides in photodegradation of antibiotics, a series of BiOBr/β-Bi2O3 nanocomposites was synthesized via a facile solvothermal process in which one-pot strategy was adopted to accomplish the purpose by adjusting the mole ratio of the bismuth and bromine. The formation of heterojunction at the BiOBr/β-Bi2O3 surface boundary was confirmed by XRD, PL, DRS, XPS and HR-TEM. The photocatalytic properties of these BiOBr/β-Bi2O3nanocomposites were evaluated by the photodegradation of norfloxacin under simulated sunlight irradiation. The BiOBr/β-Bi2O3 nanocomposites obtained at the molar ratio of 3:1 (Bi:Br) exhibit the best photodegradation activity. The photocurrent density of BiOBr/β-Bi2O3 nanocomposites (Bi:Br = 3:1) is twice higher than that of the pristine BiOBr, indicating the in-situ generating Bi2O3 on the BiOBr surface can effectively promote the separation of photogenerated electron-hole pairs and thus improving the photocatalytic performance. Furthermore, the photocatalytic mechanism was investigated using trapping experiments and ESR study. The results reveal that the matched energy band structure between BiOBr and Bi2O3 was able to facilitate the charge transfer and reduce the recombination of the photogenerated carriers. This work supplies a simple procedure for the in-situ growing Bi2O3 on Bi-based photocatalysts and an effective measurement for degrading norfloxacin.

Assessing the photocatalytic transformation of norfloxacin by BiOBr/iron oxides hybrid photocatalyst: Kinetics, intermediates, and influencing factors

Norfloxacin (NOR) is a widely used fluoroquinolone antibacterial that has drawn much concern due to its adverse effect on aquatic ecology and human health. In this study, a novel magnetically recoverable BiOBr/iron oxides (BiOBr/Fe3O4) heterojunction photocatalyst with high photocatalytic activity on NOR was successfully synthesized using a facile in-situ coprecipitation method. The samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, N2 adsorption-desorption analysis, and vibrating sample magnetometer. Several factors affecting the catalytic performance of BiOBr/Fe3O4 were investigated. Results showed that the catalytic degradation efficiency of NOR increased with the increasing bicarbonate doses, but decreased with the increasing natural organic matter concentrations. The presence of nitrate stimulated NOR degradation by BiOBr/Fe3O4 at low concentrations but inhibited the degradation at high concentrations. The photogenerated reactive species were determined based on free radicals trapping experiments, revealing that the photodegradation of NOR over BiOBr/Fe3O4 under visible light was dominated by superoxide radicals and hydroxyl radicals rather than oxidation by direct holes. On the basis of the degradation products identified by HPLC–MS, the NOR degradation pathway was proposed. NOR possibly underwent the piperazine ring transformation, decarboxylation and defluorination to generate eleven intermediates. Toxicity assays by Vibrio fischeri proved that the NOR photocatalytic transformation products retained negligible antibacterial activity relative to the parent compound. The catalytic degradation of NOR by BiOBr/Fe3O4 was also effective in the actual natural waters.

Photodegradation of Norfloxacin in aqueous solution containing algae

AbstractPhotodegradation of Norfloxacin in aqueous solution containing algae under a medium pressure mercury lamp (15 W, λmax = 365 nm) was investigated. Results indicated that the photodegradation of Norfloxacin could be induced by the algae in the heterogeneous algae-water systems. The photodegradation rate of Norfloxacin increased with increasing algae concentration, and was greatly influenced by the temperature and pH of solution. Meanwhile, the cooperation action of algae and Fe(III), and the ultrasound were beneficial to photodegradation of Norfloxacin. The degradation kinetics of Norfloxacin was found to follow the pseudo zero-order reaction in the suspension of algae. In addition, we discussed the photodegradation mechanism of Norfloxacin in the suspension of algae. This work will be helpful for understanding the photochemical degradation of antibiotics in aqueous environment in the presence of algae, for providing a new method to deal with antibiotics pollution.

Photodegradation of norfloxacin in aqueous suspensions of titanium dioxide

The photocatalytic degradation of an antibiotic norfloxacin [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline-carboxylic acid, 1], has been investigated in aqueous suspensions of titanium dioxide (TiO 2) under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation kinetics were investigated under different conditions such as different types of TiO 2, pH (ranging from 4 to 11), catalyst concentration (0.5–3 g L −1), substrate concentration (0.15–0.5 mM) and in the presence of electron acceptor such as hydrogen peroxide (H 2O 2, 10 mM) besides molecular oxygen. Semiconductor titanium dioxide (Degussa P25) was found to be more efficient as compared with other photocatalysts.