Norfloxacin Degradation Rate Research Articles

Chlorine dioxide radicals triggered by chlorite under visible-light irradiation for enhanced degradation and detoxification of norfloxacin antibiotic: Radical mechanism and toxicity evaluation

A novel combined chlorine dioxide (ClO2)-photocatalysis technique was developed by dosing chlorite (ClO2−) in a visible light photocatalytic system. Active ClO2 radicals were produced through the activation of ClO2− by photoinduced ·OH radicals. It is for this reason that the degradation rate of norfloxacin (NOR) in the combined ClO2-photocatalysis system was promoted to 0.2672 min−1, approximately 6.6 times faster than the single photocatalytic system. The durable active ClO2 guaranteed the stability of the combined ClO2-photocatalysis system when facing external interferences, such as pH change, inorganic ions, and natural organic matter (NOM). Quantitative structure–activity relationship (QSAR) prediction and toxicity verification identified effective elimination of biological toxicity of NOR with the assistance of ClO2. Moreover, the residual ClO2− can be retransformed into ClO2 based on the ClO2−/ClO2 dynamic interchange mechanism, facilitating ClO2− residue elimination. ClO2− also served as the sacrificial agent of ·OH for promoting electron-hole separation and protecting photocatalysts from photo-erosion, which was responsible for the outstanding stability in multiple cycle tests. Results showed the novel combined technique can respond well to natural sunlight. This work provides a strategy for designing advanced oxidation processes (AOPs) by integrating ClO2 oxidation and photocatalytic oxidation to achieve degradation and detoxification of antibiotic wastewater under natural sunlight.

Ligand-metal charge transfer mechanism enhances TiO2/Bi2WO6/rGO nanomaterials photocatalytic efficient degradation of norfloxacin under visible light

Overuse of antibiotics threatens water security, and photocatalysis is a potential technology to alleviate this problem. In this study, the TiO2/Bi2WO6/rGO nanocomposite materials were prepared by a solvothermal process, and a series of characterizations were carefully examined. Then, the removal of norfloxacin from water under visible light irradiation was investigated to evaluate the photocatalytic activity of TiO2/Bi2WO6/rGO. The TiO2/Bi2WO6/rGO composite catalyst has higher photocatalytic activity than TiO2 and TiO2/Bi2WO6 under visible light, and the optimal addition content for rGO is 0.5%. After 60 min of visible light irradiation, the degradation rate of norfloxacin on TiO2/Bi2WO6/rGO-0.5% reached 87.79%. Furthermore, the UV–Vis of the complex suggests that the ligand-metal electron transfer mechanism enhances the catalytic activity of TiO2/Bi2WO6/rGO. Finally, the mechanism of photocatalytic degradation of norfloxacin by TiO2/Bi2WO6/rGO composite catalyst was proposed.

Degradation of norfloxacin by hydroxylamine enhanced fenton system: Kinetics, mechanism and degradation pathway

This study demonstrated a fast and efficient degradation of a typical antibiotic norfloxacin (NOR) in a hydroxylamine enhanced Fenton (HA-Fenton) system, which showed a higher catalytic activity over a wider pH range (3.0–9.0). The removal efficiency of NOR was 96% at following conditions: 10 mg/L NOR, 10 μM Fe2+, 1.0 mM H2O2, 0.4 mM HA and pH 5.0. The degradation rate of NOR in the HA-Fenton system (0.23 min−1) was 10.9 times of that (0.021 min−1) in Fenton system. The addition of HA to Fenton system accelerated the conversion of Fe3+ to Fe2+, leading to the high concentration of ·OH in the HA-Fenton system. Ten degradation transformation products were detected by ultra-performance liquid chromatography tandem quadrupole time of flight mass spectrometer (UPLC-QTOF-MS), consequently, three main degradation steps were proposed, including defluorination, quinolone group transformation, and defluorination and piperazinyl ring opening. Further analyses of NO3−, NO2− and F− after the reaction indicated that defluorination process was the crucial degradation step. The HA-Fenton system might offer an efficient alternative for degradation of antibiotics in wastewater.

Degradation of norfloxacin wastewater using kaolin/steel slag particle electrodes: Performance, mechanism and pathway

In this work, kaolin/steel slag particle electrodes (KSPEs) were synthesized using a calcination method, and they were used to degrade norfloxacin (NOR) wastewater in three-dimensional (3D) reactor. Characterization methods used by KSPEs included SEM, XRF, XRD and BET. The effects of cell voltage, initial pH, KSPEs dosage and initial NOR concentration on NOR degradation were studied in the optimization experiment of operating parameters. The NOR degradation rate and COD removal rate can reach 96.02% and 93.45% under the optimal parameters within 30 min, and energy consumption is 0.99 kWh m−3. As a result, KSPEs shows excellent catalytic performance and cycling, and still has high electrocatalytic activity after 10 cycles. Finally, the degradation mechanism and degradation pathways of KSPEs to treat NOR are proposed.

Preparation of Cu2O Particles and their Photocatalytic Properties

Photocatalytic technology is a potential way for the environmental problems caused by antibiotics contained in water. In this paper, Cu2O particles were prepared by hydrothermal method. The microstructure and morphology of Cu2O were characterized by XRD, SEM. The optical and electrochemical properties of the prepared samples were studied by UV-Vis and photocurrent. The results show that the prepared Cu2O have an octahedral morphology and exposes more (111) crystal planes, with a particle size of 2-5 μm, and has the better optical absorption performance at 500-600 nm. Finally, the photocatalytic performance of the samples was evaluated using Norfloxacin as the target degradation pollutant. The results show that the degradation rate of Norfloxacin over the prepared Cu2O was 79.8%.The •OH and •O2 − play a major role in degradation of Norfloxacin.

Immobilized Ag3PO4/GO on 3D nickel foam and its photocatalytic degradation of norfloxacin antibiotic under visible light.

In this study, a series of Ag3PO4/graphene oxide (GO) films were dip-coated on a metal nickel foam. The immobilized catalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy and photoluminescence spectroscopy. The results show that Ag3PO4/GO was successfully supported on a nickel foam. The photocatalytic activity of the film catalyst under visible light was investigated by the degradation of norfloxacin, an antibiotic. Photocatalytic stability of this catalyst was also investigated. An optimized film exhibited superior activity and stability, the degradation rate of norfloxacin was about 83.68% in 100 min and the reaction rate constant k was 1.9 times that of pristine Ag3PO4. Further investigation found that photo-generated holes (h+) and superoxide anion radicals (·O2−) are the main active species in the photodegradation process. The result indicates that the addition of GO inhibits the recombination of photogenerated electron–hole pairs, and thus has improved the photocatalytic activity and cyclic stability under visible light. The photocatalytic mechanism of the film catalyst was proposed. The prepared Ag3PO4/GO film catalyst is a promising candidate for treatment of wastewater containing antibiotics.

Degradation effect and mechanism of gas-liquid phase dielectric barrier discharge on norfloxacin combined with H2O2 or Fe2+

Norfloxacin (NOR) is a typical kind of Fluoroquinolone antibiotics which is extensively used around the world. Residues of NOR have been found continuously increasing in the water systems thus posing detrimental effects to the aquatic ecosystem and human health. In this study, the degradation effect and mechanism on NOR in aqueous solution are investigated by gas-liquid phase dielectric barrier discharge (DBD) plasma combined with different catalysts (H2O2 or Fe2+). The concentrations of three representative plasma-generated long-lived reactive species (H2O2, O3 and NO3-) were measured in dH2O and found enhancing with the lengthening discharge period. Variations on the treatment parameters were carried out in discharge power, initial solution pH and the concentration of catalysts. A discharge power at 60 W provided optimal balance on the degradation effect and energy efficiency would be beneficial, while there is not much impact from the initial solution pH on NOR degradation. Both H2O2 and Fe2+ at low concentration (0.5–10 mg/L of Fe2+, 0.1–1.0 mmol/L of H2O2) were observed contributing to the improvement on the NOR degradation rate, while inhibition would occur at high concentration (10–20 mg/L of Fe2+, 1.0–2.0 mmol/L of H2O2). The DBD/H2O2 (0.5 mmol/L)/Fe2+ (10 mg/L) system was found the optimal condition to achieve a high NOR degradation rate of more than 98% after plasma treatment for only 0.5 min at discharge power of 60 W. Moreover, 72.3 ± 1.7% of the total organic carbon (TOC) in NOR solution have been removed in the DBD/Fe2+ (10 mg/L) system at 15 min which signifies a high mineralization efficiency. The cleavage of piperazine ring and quinolone ring, defluorination and hydroxylation are considered the major pathways for NOR degradation. The biological toxicity of the plasma/Fe2+-induced degradation intermediates has been detected and it fluctuated with the treatment time and finally declined. Therefore, the DBD/catalyst system could be an effective and promising method on pharmaceutical wastewater treatment in the future.

Norfloxacin degradation byBacillus subtilisstrains able to produce biosurfactants on a bioreactor scale

The discharge of antibiotics into the environment has become a major concern since this group of pharmaceuticals influence on microbial communities not only by its mode of action, but also because of the risk of a worldwide dispersal of antibiotic resistance genes (ARG). Antibiotics residues have been found in various environments such as waters, sediments, and soils. Moreover, most WWTPs are not designed to treat such kind of pollutants, which remain incompletely removed. Currently, biodegradation processes which involved bacterial strains with increased degradation capabilities is one of the most promising technique. The aim of this study was to evaluate the norfloxacin biodegradation potential of the three Bacillus subtilis strains named T-1, T’-1 and I’-1a on a bioreactor scale. The aerobic degradation was conducted in a 5-liter bioreactor on minimal salts medium in co-metabolic culture supplemented with glucose. The degradation rate of norfloxacin was determined with the HPLC technique. The surface tension was determined using ring method in order to observe the changes in biosurfactants production. Also, the biofilm formation abilities of the bacteria with two quantitative methods, crystal violet (CV) method and TTC-based test and enzymes production were evaluated.

Removal of norfloxacin using coupled synthesized nanoscale zero-valent iron (nZVI) with H2O2 system: Optimization of operating conditions and degradation pathway

Abstract In this study, nanoscale zero-valent iron (nZVI) was synthesized in the laboratory by the borohydride reduction method. nZVI was characterized by transmission electron microscopy (TEM), scan electronic microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). In addition, the degradation performance of norfloxacin (NOR) in nZVI/H 2 O 2 Fenton-like system was investigated in detail under various experimental conditions. It was found that the removal of NOR depended on its initial concentration, initial pH, temperature, H 2 O 2 concentration and nZVI dose. At the ambient temperature, the degradation rate of NOR by nZVI/H 2 O 2 Fenton-like reaction under the acidic medium (pH = 3–4) was more than 95% within 40 min of the reaction time, and the mineralization degree was around 50% in terms of total organic carbon (TOC) measurement. Optimal temperature for NOR removal was 308 K, and higher temperature would cause useless decomposition of H 2 O 2 and consequently reduction of NOR degradation. The degradation rate and total removal efficiency of NOR were favored by increasing the nZVI and H 2 O 2 dosages. The optimal conditions for NOR degradation were: initial pH = 4.0, H 2 O 2 concentration = 20 mmol/L, nZVI dose = 100 mg/L, temperature = 308 K. The rate constants ( K ob s ) of NOR degradation could be fitted well with a pseudo-second-order kinetic equation. Several degradation intermediates of NOR were detected and confirmed, including C 15 H 20 FN 3 O ( m / z 278), C 9 H 11 FN 2 ( m / z 167), C 7 H 7 FN 2 ( m / z 139), and C 7 H 8 FN ( m / z 126), respectively. Based on the identified intermediates and the Gaussian quantum statistics molecular bonding energy calculation, the possible pathway for NOR degradation under nZVI/H 2 O 2 Fenton-like reaction was discussed.