Photocatalytic Degradation Of Oxytetracycline Research Articles

Photocatalytic degradation of oxytetracycline using ZnO catalyst

AbstractIn the present study, the degradation of oxytetracycline (OTC) under ultraviolet (UV) light in the presence of ZnO catalyst was investigated, and optimum parameters for degradation efficiency were determined. Different pH values, ZnO dosages, reaction times, OTC concentrations, and UV lights were used in this study. The optimum conditions found were as follows: pH 4, ZnO 1 g L−1, reaction time 25 min, and OTC concentration 10 mg L−1. Degradation efficiency was 42.1%, 76%, 70.7%, and 61.7% for ZnO and photocatalytic (for UV‐A, UV‐B, and UV‐C) degradation at optimal conditions, respectively. The resulting products after the photocatalytic oxidation of OTC were determined in the study. To identify the toxicity of degradation products and OTC, the lowest LC 50 (50% lethal concentration) and EC 50 (50% effective concentration) values were found. The resulting ethanamine, 2‐(2,6‐dimethylphenoxy)‐N‐methyl‐ by‐products were observed to be more toxic than OTC. Furthermore, it was seen that isopropoxy carbamic acid, ethyl ester by‐products were formed, whose presence is environmentally risky for aquatic environments due to their low EC50 values.

Oxytetracycline degradation and antidermatophytic activity of novel biosynthesized MoS2 photocatalysts

The presence of environmental contamination poses a significant threat to life on our planet. Oxytetracycline, an antibiotic with a broad spectrum of effectiveness, demonstrates resistance to biodegradation, potentially resulting in an ecological hazard. In this study, we synthesized both pure and biosynthesized Molybdenum Disulfide (MoS2) nanoparticles using extracts from the bark of Ficusreligiosa L (FR) and leaves of ZiziphusjujubeL (ZJ). These nanopartices were characterized by various analytical methods to assess their efficiency in photocatalytic degradation of oxytetracycline (OTC) and their antidermatophytic activity. X-ray diffraction patterns revealed that the prepared MoS2 catalysts typically exhibited hexagonal phase structure with crystalline size of approximately 13, 6, and 4 nm. Both pure and biosynthesized MoS2 nanoparticles displayed a nanoflake-like morphology with a spherical size distribution. BET surface area analyses exhibited an increase in surface area for biosynthesized MoS2 nanoparticles from 79 to 121 m2g−1. Optical absorption revealed a red shift in band gap energy, decreasing from 2.37 to 2.03 eV for biosynthesized MoS2 nanoparticles. The biosynthesized MoS2:FR nanoparticles exhibited remarkable OTC degradation with 99 % achieved within 100 min along with strong antifungal activity (Minimum Inhibitory Concentration - MIC of 12.5 µg/mL, Minimum Fungicidal Concentration - MFC of 25 µg/mL). These biosynthesized MoS2 catalysts are promising for water treatment purposes.

Photocatalytic degradation of oxytetracycline by UiO-66 doped three-dimensional flower-like MoS2 heterojunction: DFT, degradation pathways, mechanism

BackgroundMoS2 has potential in the photocatalytic degradation. The combination of UiO-66 (University of Oslo) and MoS2 not only accelerates the electron transfer efficiency but also increases active sites, thereby further improves the photocatalytic activity. MethodsThe three-dimensional flower-like MoS2/UiO-66 heterojunctions were prepared by in-situ hydrothermal method, which took advantage of metal-organic framework and semiconductor material. Oxytetracycline degradation was used to assess the photocatalytic performance, and the effects of catalyst dosage and solution pH on the performance were looked into. Significant findingsMoS2 nanosheets formed three-dimensional flower-like spheres on the surface of UiO-66 particles as they expanded in all directions. The unique structure exposed more active sites and provided sufficient surface reaction sites for the reactants. The composite had a broad-spectrum light response, and the oxytetracycline degradation efficiency reached 86.6 % after 120 min’ irradiation. The band structure and density of states of MoS2 were calculated. The possible degradation paths were deduced by theoretical calculation and experimental detection. This excellent photodegradation can be attributed to the fact that Z-type heterojunction promoted the separation of photogenerated electron-hole pairs, prolonged the carrier lifetime, and generated more active substances. In addition, the cyclic test showed that the composite material had good repeatability and potential application prospect.

Photocatalytic degradation of oxytetracycline by SiO2–TiO2–Ag electrospun fibers

The contamination and dispersion of antibiotics into the environment through effluents from sewage treatment plants have produced serious consequences like the generation of resistant bacteria, generating a health emergency, so the need arises to develop processes to eliminate antibiotics in effluents. One of the methodologies used is advanced oxidation where a complete degradation of antibiotics can be reached, among the advanced oxidation processes, photocatalysis stands out as an efficient degradation pathway of organic pollutants from a photocatalyst. In the present investigation SiO2–TiO2 fibers were obtained by sol-gel and electrospinning techniques which had a cylindrical morphology and a smooth surface free of defects with a diameter 266 ± 62 nm. In increasing photocatalytic properties, the SiO2–TiO2 fibers were doped with silver by electrodeposition resulting in the deposition of particles with a branched dendritic morphology with a size of approximately 1 μm. The characterization of SiO2–TiO2–Ag fibers by infrared in the fibers eluted bands characteristic of the Si–O–Si and Ti–O–Ti bonds, and by means of the X-ray diffraction were identified crystalline phases corresponding to the anatase and rutile of the Titania, as well as face-centered cubic silver. Oxytetracycline was used as a contaminant to investigate the photocatalytic performance of SiO2–TiO2–Ag material, where from an initial concentration of 30 ppm in the presence of SiO2–TiO2 fibers its degradation percentage was 65%, unlike 90% in 7 h using silver-doped fibers. The increased degradation of oxytetracycline is attributed to the success in decreasing the banned band of SiO2–TiO2 fibers from 3.1eV to 2.5eV to silver doping.

One-pot solvothermal synthesis of Bi/Bi2S3/Bi2WO6 S-scheme heterojunction with enhanced photoactivity towards antibiotic oxytetracycline degradation under visible light

A novel noble-metal-free ternary Bi/Bi2S3/Bi2WO6 S-scheme heterojunction and Schottky junction was successfully synthesized by one-pot solvothermal method. UV–Vis spectroscopy showed improved light absorption in the ternary composite structure. Electrochemical impedance spectroscopy and photoluminescence spectroscopy confirmed the reduced interfacial resistivity and photogenerated charge recombination rate of the composites. Using oxytetracycline (OTC) as model pollutant, Bi/Bi2S3/Bi2WO6 presented high photocatalytic activity towards OTC degradation, where the removal rate of Bi/Bi2S3/Bi2WO6 was 1.3 and 4.1 times higher than that of Bi2WO6 and Bi2S3 under visible light irradiation in 15 min, respectively. The excellent visible photocatalysis activity was attributed to the SPR effect of metal Bi and the direct S-scheme heterojunction of Bi2S3 and Bi2WO6 with the matched energy band structure, which led to the increased electron transfer rate and high separation efficiency of the photogenerated election-hole pairs. After seven cycles, the degradation efficiency for 30 ppm OTC with Bi/Bi2S3/Bi2WO6 only decreased 20.4%. In the degradation solution, the composite photocatalyst leached only 16 ng/L Bi and 26 ng/L W of metal with high photocatalytic stability. Moreover, free radical quenching experiment and electron spin-resonance spectroscopy experiment revealed that ·O2−, 1O2, h+ and ·OH played crucial roles in the photocatalytic degradation of OTC. Based on the analysis of high performance liquid chromatography-mass spectrometry for the intermediates in the degradation process, the degradation pathway was provided. Finally, combined with ecotoxicological effect analysis, the decreased toxicity of OTC after degradation towards rice seedlings was confirmed.

Adsorption and photocatalytic degradation process of oxytetracycline using mesoporous Fe-TiO2 based on high-resolution mass spectrometry

In this study, the adsorption and photocatalytic degradation of oxytetracycline (OTC) were systematically investigated using different metal-doped anatase-phase mesoporous TiO2 nanocatalysts (M−TiO2, M = Fe, Co, Ni, Cr). The results showed that doping with different metals had a significant effect on the ability of TiO2 to adsorb and degrade OTC. Comparing the photoelectric properties of four photocatalysts (Fe-TiO2, Co-TiO2, Ni-TiO2 and Cr-TiO2), it was observed that the mutual synergy between the separation ability of the photogenerated carriers and the adsorption ability of pollutants was the fundamental reason for the excellent photocatalytic performance of Fe-TiO2. The relative intensities of the high-resolution mass spectrometry (HRMS) peaks were used to track and analyse the degradation products of pollutants at different adsorption or light-irradiation times during the photocatalytic process. The ability of the pollutants to undergo dark-state adsorption significantly influenced their degradation paths and products. The possible mechanism of the photocatalytic decomposition of pollutants using Fe-TiO2 along different paths was proposed according to the Fukui function calculation and MS results. To the best of our knowledge, this is the first time that quantitative HRMS results have been used to assess the degradation pathways of pollutants.

The photocatalytic degradation of oxytetracycline using 2D and 3D Bi5O7I and BiOCl under visible light irradiation – Optimization of the reaction parameters

Bismuth oxyhalides are a group of efficient photocatalysts to achieve the complete degradation of organic pollutants in water under UV-A/visible light irradiation. In this work, BiOCl and Bi5O7I were synthesized through different procedures to obtain 2D (nanoneedles) and 3D (microspheres and nanoflakes) structures. The structural, chemical and optical properties of the materials were characterized as well as their photocatalytic activity to degrade the antibiotic oxytetracycline under visible light irradiation. Bi5O7I nanoflakes completely degraded oxytetracycline within 300 min of UV-A/visible light irradiation while BiOCl materials achieved only 80% of removal. The pH, initial concentration of oxytetracycline and the catalyst dosage were optimized using the Box-Behnken design of experiments. At pH of 9, irrespective of dosage and initial concentration of oxytetracycline, the complete degradation was achieved after < 10 min of irradiation, with an initial rate constant of 0.36 min−1. Under the optimal reaction conditions, Bi5O7I nanoflakes demonstrated to efficiently remove the target pollutant in tap water through three consecutive reaction cycles, displaying the potential of this material to be tested in upscaled systems.

Photocatalytic degradation of oxytetracycline with the REMs (Er, Tm, Yb)-doped nickel and copper aluminates

Oxytetracycline (OTC) is an antibiotic drug. It is widely used in veterinary, animal husbandry, and agriculture. Antibiotics are emerging environmental pollutants. We propose an efficient photocatalytic method for remediation of aqueous reservoirs from OTC. We synthesized erbium-, thulium- and ytterbium-doped nickel and copper aluminates. The doped samples have better dispersion, higher specific surface areas (188 m2 g−1 for Er-NA) and decreased energy band gaps. The doping of nickel and copper aluminates (NA and CA) significantly improved the photocatalytic performance. Er-CA was the most photoactive. The Er-doping of NA and CA increased photodegradation efficiency from 27 to 73 % and from 65 to 90 %, respectively. The LC-MS analysis allowed to identify the major intermediates of OTC photodegradation. The photocatalytic metabolites were hemocompatible and did not present cytotoxicity towards monocytic cells. We envisage a great potential of the rare-earth-metal-doped semiconductors in the removal of emerging environmental pollutants.

Photocatalytic Degradation of Oxytetracycline Using Zeolite Imidazole Framework-8 (ZIF-8) as an Effective Catalyst

Antibiotics are a class of organic pollutant in the medical field for hundreds of years. Due to the continuous discharge of antibiotics in the environment, the phenomenon of pseudo-persistence of antibiotics is produced. Therefore, it is necessary to develop an advanced sustainable technology to remove antibiotics from water resources. In this study, Zeolite Imidazole Framework-8 (ZIF-8) was prepared by a simple and rapid method. Oxytetracycline (OTC) degradation was performed using ZIF-8 as a photocatalyst under visible light (VL) (500[Formula: see text]W xenon lamp) irradiation. Under different experimental conditions, ZIF-8 has strong catalytic removal performance for OTC. When the reaction conditions are: OTC concentration of 80 mg L[Formula: see text], ZIF-8 concentration of 1.0[Formula: see text]g[Formula: see text]L[Formula: see text], pH 5.96, the OTC removal rate is more than 90%. Through the detection and analysis of degradation intermediates, the possible degradation pathway of OTC was proposed. This study showed that the OTC removal rate of ZIF-8 could still reach 69% after four times of recycling. The results showed that the ZIF-8/VL system had high OTC removal efficiency and good recyclability.

Photocatalytic Degradation of Oxytetracycline by Sio2-Tio2-Ag Electrospun Fibers

Photocatalytic Degradation of Oxytetracycline by Sio2-Tio2-Ag Electrospun Fibers

Photocatalytic degradation of oxytetracycline under visible light by nanohybrids of CoFe alloy nanoparticles and nitrogen-/sulfur-codoped mesoporous carbon

Efficient photodegradation of antibiotics in water systems is significant for environmental restoration and water purification. In this work, a series of catalysts for oxytetracycline (OTC) degradation under visible light was proposed. The hybrids (denoted by CoFe@NSC) of CoFe alloy and N/S-codoped mesoporous carbon were obtained by annealing CoFe Prussian blue analogue (CoFe PBA) nanocubes under different temperatures using thioacetamide as the N and S resource. The CoFe@NSC photocatalysts show substantially boosted photocatalytic activity for OTC degradation compared with that of the CoFe PBA catalyst. Among the three CoFe@NSC hybrids obtained by pyrolyzing at 800 °C, 900 °C, and 1000 °C, the CoFe@NSC-1000 hybrid at 1000 °C exhibits the highest photocatalytic activity toward OTC degradation under visible light irradiation for its highly conjugated nanostructure, large specific surface area (733.0 m2 g−1), enhanced visible light absorption capacity, and improved separation/migration rate for photogenerated charge carriers. Approximately 90% of OTC was degraded by CoFe@NSC-1000 catalyst after visible light irradiation for 150 min. Electron spin resonance (ESR) and trapping tests indicate that the photoinduced superoxide and hydroxyl radicals are the main active species for photodegradation. The possible photocatalytic mechanism was proposed based on the active species, trapping experiments and ESR analysis. The biotoxicity of photocatalytic degradation products and residual antibiotic were also explored using E. coli as the reference organism. This work offers new insight into the development of novel catalysts for photodegradation of antibiotics.

Novel 2D/2D g-C3N4/Bi4NbO8Cl nano-composite for enhanced photocatalytic degradation of oxytetracycline under visible LED light irradiation

A novel visible-light-responsive 2D/2D g-C3N4/Bi4NbO8Cl nano-composite photocatalyst was hydrothermally synthesized using g-C3N4 and Bi4NbO8Cl. Various characterization techniques were employed to characterize the as-synthesized g-C3N4/Bi4NbO8Cl nano-composites. The photocatalytic efficiency of the nano-composite materials was assessed by the degradation of an emerging pharmaceutical pollutant, oxytetracycline (OTC), under visible LED light irradiation. It was observed that at an optimum mass ratio of 20% (g-C3N4 to Bi4NbO8Cl), the 20g-C3N4/Bi4NbO8Cl nano-composite produced the highest photocatalytic degradation efficiency toward OTC. The photocatalytic degradation of OTC (20 mgL−1) by 20g-C3N4/Bi4NbO8Cl (1 gL−1), under 60 min of visible LED light irradiation was 87%, which was about 1.2 and 1.8 times higher as compared to that of pure Bi4NbO8Cl and g-C3N4, respectively. This improved performance was associated with the formation of type-II heterojunction, which resulted in better visible-light absorption and reduced recombination of photogenerated electron-hole pairs. Moreover, it was observed that after four cycles of degradation experiments, the nano-composite was stable. The results of this work not only demonstrate the construction of 2D/2D g-C3N4/Bi4NbO8Cl nano-composite for successful low-cost and energy-efficient photocatalytic degradation of recalcitrant pollutant but also motivate the production of similar photocatalysts targeting environmental remediation.

V2O5/RGO/Pt nanocomposite on oxytetracycline degradation and pharmaceutical effluent detoxification

AbstractBACKGROUNDAntibiotics have been identified as significant pollutants owing to their adverse impact on the environment through the development of antibiotic‐resistant bacteria. In a previous study, an e‐waste‐based reduced graphene oxide‐V2O5‐platinum (RGOV‐Pt(1%)) nanocomposite was prepared and subsequently used for the photocatalytic degradation of oxytetracycline (OTC), a tetracycline group of antibiotics.RESULTSThis study aimed to assess the impact of additives such as H2O2, NaCl, Na2CO3, ethanol and persulfate on the photocatalytic degradation of OTC using RGOV‐Pt(1%) nanocomposite. The results showed that the degradation efficiency decreased in the presence of NaCl and Na2CO3 owing to the electron–hole scavenging property of their anions. Low concentrations of H2O2 (up to 10 mmol L–1) increased the OTC degradation efficiency, whereas high concentrations decreased the OTC degradation owing to the quenching of hydroxyl radicals. However, the presence of persulfate increased the OTC degradation efficiency owing to the formation of hydroxyl radicals. Furthermore, the OTC degradation pathway was elucidated using high‐performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). The study was extended to real pharmaceutical effluent and the degradation efficiency was found to be less for real effluent (87%) in comparison with OTC (99%) in aqueous solution.CONCLUSIONRGOV‐Pt(1%) photocatalyst effectively degraded OTC. An OTC degradation pathway was proposed based on the intermediates formed. The impact of additives was established. Effective real pharmaceutical effluent detoxification was observed. Thus the synthesized RGOV‐Pt(1%) nanocomposite is a hopeful alternative for the removal of antibiotics in contaminated waters and sites. © 2019 Society of Chemical Industry

Photocatalytic Degradation of Oxytetracycline by Photosensitive Materials and Toxicological Analysis by Caenorhabditis elegans.

This study explored a facile one-step hydrothermal method of preparing a high-performance photocatalyst, namely, graphene-TiO₂, for oxytetracycline (OTC) removal. The nanocomposites were characterized by Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy and X-ray diffraction (XRD). The photocatalytic properties of different graphene loading types and various OTC initial concentrations, temperatures, and initial pH values were investigated. Results showed that the material with 10% graphene content exhibited the best performance and removal efficiency (beyond 99%) of OTC within 180 min at 35 °C and pH 5.5. The effects of different reactive oxygen species scavengers on photodegradation and the contributions were evaluated, and a possible reaction mechanism was proposed. Caenorhabditis elegans was used for toxicity testing during the entire degradation process and achieved a favorable result.

Ultra-light and compressible 3D BiOCl/ RGO aerogel with enriched synergistic effect of adsorption and photocatalytic degradation of oxytetracycline

An ultra-light and compressible three-dimensional bismuth oxychloride/reduced graphene oxide (BiOCl/RGO) aerogel is fabricated via a facile hydrothermal method and characterized by various techniques. Owing to the improved visible-light response, lower internal resistance and enhanced electron transfer ability, the BiOCl/RGO aerogel (BGA) displays outstanding synergistic effect of adsorption and photocatalytic degradation. This not only reduces the diffusion distance between pollutants and photocatalysts but also inhibits the recombination of electrons and holes, thereby augmenting the photocatalytic activity. The optimized 40% BGA harvests the highest removal rate of 93.3% for 20 mg⋅L−1 oxytetracycline (OTC), which is ca. 1.43 folds higher than that of the pure BiOCl. Holes has been proved to play a dominate role in the OTC degradation. Meanwhile, the antibacterial activity test shows that the biotoxicity of OTC toward Escherichia coli DH5a is largely eliminated after 40% BGA treatment. In addition, the 40% BGA presents superior stability and recyclability after 4 cycles. It is anticipated that the BGA has great potential in actual wastewater treatment.

Comparing Photocatalytic Activity of ZnO and Nanospherical ZnO/Bentonite Catalyst: Preparation, Structural Characterization and their Photocatalytic Performances using Oxytetracycline Antibiotic in Aqueous Solution

&lt;strong&gt;&lt;/strong&gt;Photocatalytic degradation of Oxytetracycline (OTC) in aqueous solution was performed using pure ZnO and ZnO/Bent composites. Both catalysts were synthesized trough a simple one-step chemical precipitation method. The prepared samples were characterized using SEM-EDAX and XRD analysis. Due to the immobilization of ZnO nanospheres upon bentonite surface, 25.67 m&lt;sup&gt;2&lt;/sup&gt; g&lt;sup&gt;-1&lt;/sup&gt; of specific surface area was obtained for the ZnO/Bent which lower than the specific surface area of the raw bentonite (112.25 m&lt;sup&gt;2&lt;/sup&gt; g&lt;sup&gt;-1&lt;/sup&gt;). ZnO/Bent catalyst showed the best photocatalytic performance than ZnO for OTC degradation under UV light.

Photocatalytic Degradation of Oxytetracycline by Ternary Mixed Catalyst and Toxicity Assessment Using Boar Sperm.

Response surface methodology was adopted to obtain ternary mixed catalysts of TiO2-loaded ZSM-5 zeolite and graphene. Oxytetracycline was used as challenged toxicant to evaluate the photocatalytic degradation efficiency of the composites. The optimal weight ratio of graphene, TiO2, and ZSM-5 was 1:8:1. The composites were characterized by ultraviolet-visible spectroscopy, X-ray diffraction, fourier transform infrared, N2 adsorption-desorption isotherms, and transmission electron microscope with an energy-dispersive spectroscopy system, etc. Synthesized samples showed high stability and strong visible-light absorption efficiency. The optimal operating conditions of oxytetracycline photocatalytic degradation were achieved over a wide range of pH and temperature. With 0.1 g/L of optimal ternary mixed composite, the photocatalytic degradation of oxytetracycline was nearly reached completion within 150 min at all treatment temperatures at pH 7. Toxicity of degraded oxytetracycline solution was assayed by a boar sperm quality model using fluorescent staining and flow cytometry. During 180 min of photocatalytic treatment, the degraded oxytetracycline solution showed increasing biotoxicity and changed the morphology and function of boar sperm, despite not killing them.

Photocatalytic Degradation of Oxytetracycline in Aqueous Solutions with TiO2in Suspension and Prediction by Artificial Neural Networks

In this study, the photocatalytic degradation of oxytetracycline (OTC) in aqueous solutions has been studied under different conditions such as initial pollutant concentrations, amount of catalyst, and pH of the solution. Experimental results showed that photocatalysis was clearly the predominant process in the pollutant degradation, since OTC adsorption on the catalyst and photolysis are negligible. The optimal TiO2 concentration for OTC degradation was found to be 1.0 g/L. The apparent rate constant decreased, and the initial degradation rate increased with increasing initial OTC concentration with the other parameters kept unchanged. Subsequently, data obtained from photocatalytic degradation were used for training the artificial neural networks (ANN). The Levenberg–Marquardt algorithm, log sigmoid function in the hidden layer, and the linear activation function in the output layer were used. The optimized ANN structure was four neurons at the input layer, eighteen neurons at the hidden layer, and one neuron at the output layer. The application of 18 hidden neurons allowed to obtain the best values for R2 and the mean squared error, 0.99751 and 7.504e–04, respectively, showing the relevance of the training, and hence the network can be used for final prediction of photocatalytic degradation of OTC with suspended TiO2.

Rapid synthesis of Ti-MCM-41 by microwave-assisted hydrothermal method towards photocatalytic degradation of oxytetracycline

This study employed microwave-assisted hydrothermal method to synthesize Ti-MCM-41, which are mesoporous materials with a high surface area and excellent photocatalytic ability. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and ultraviolet–visible spectroscopy (UV–Vis) were employed. The XRD findings showed that Ti-MCM-41 exhibited a peak at 2θ of 2.2°, which was attributed to the hexagonal MCM-41 structure. The BET (Brunauer–Emmett–Teller) results agreed with the TEM findings that Ti-MCM-41 has a pore size of about 3–5nm and a high surface area of 883m2/g. FTIR results illustrated the existence of Si–O–Si and Si–O–Ti bonds in Ti-MCM-41. The appearance of Ti 2p peaks in the XPS results confirmed the FTIR findings that the Ti was successfully doped into the MCM-41 structure. Zeta (ζ)-potential results indicated that the iso-electric point (IEP) of Ti-MCM-41 was at about pH3.02. In this study, the photocatalytic degradation of oxytetracycline (OTC) at different pH was investigated under Hg lamp irradiation (wavelength 365nm). The rate constant (K′obs) for OTC degradation was 0.012min−1 at pH3. Furthermore, TOC (total organic carbon) and high resolution LC–MS (liquid chromatography–mass spectrometry) analyses were conducted to elucidate the possible intermediate products and degradation pathway for OTC. The TOC removal efficiency of OTC degradation was 87.0%, 74.4% and 50.9% at pH3, 7 and 10, respectively. LC–MS analysis results showed that the degradation products from OTC resulted from the removal of functional groups from the OTC ring.

Advantages of TiO2/5A composite catalyst for photocatalytic degradation of antibiotic oxytetracycline in aqueous solution: Comparison between TiO2 and TiO2/5A composite system

Abstract To probe advantages in TiO2/5A zeolite composite system, the photocatalytic degradation and adsorption of the antibiotic oxytetracycline (OTC) by unsupported TiO2 and 5A zeolite coated with 15 mass% TiO2 (15%T5A) under a series of conditions were investigated. The primary adsorption results indicated that 5A had much better adsorptive capability of OTC than TiO2 except at high pH values (pH ≧ 11). A multivariate analysis and a response surface methodology (RSM) were applied to develop a quadratic model as a functional relationship between OTC removal efficiency and the independent variables (the initial pH values and the dosage of the catalyst). The optimal OTC removal conditions found with 15%T5A dosage were 1.00 g/L for pH 5 and 7, 0.80 g/L for pH 9, and 0.68 g/L for pH 11. Under these conditions, the 15%T5A composite photocatalysis showed a quicker OTC removal and degradation speed than unsupported TiO2. Besides, competitive organics like tert-butyl alcohol (TBA), methanol and humid acid, were added during the photocatalytic degradation of OTC by UV + TiO2 and UV + 15%T5A at pH 7. The experimental results indicated that the 15%T5A composite system had a better anti-interference capability of radical scavengers, and humid acid at a low concentration than unsupported TiO2. Moreover, the 15%T5A proved a more stable activity during recycled use and a much quicker sedimentation performance than nano-TiO2.