Initial Tetracycline Concentration Research Articles

Role of iron(II) sulfide in autotrophic denitrification under tetracycline stress: Substrate and detoxification effect

Autotrophic denitrification using inorganic compounds as electron donors has gained increasing attention in the field of wastewater treatment due to its numerous advantages, such as no need for exogenous organic carbon, low energy input, and low sludge production. Tetracycline (TC), a refractory contaminant, is often found coexisting with nutrients (NO3− and PO43−) in wastewater, which can negatively affect the biological nutrient removal process because of its biological toxicity. However, the performance of autotrophic denitrification under TC stress has rarely been reported. In this study, the effects of TC on autotrophic denitrification with thiosulfate (Na2S2O3) and iron (II) sulfide (FeS) as the electron donors were investigated. With Na2S2O3 as the electron donor, TC slowed down the nitrate removal rate, which decreased from 1.32 to 0.18 d−1, when TC concentration increased from 0 mg/L to 50 mg/L. When TC concentration was higher than 2 mg/L, nitrite reduction was seriously inhibited, leading to nitrite accumulation. With FeS as the electron donor, nitrate removal was much more efficient under TC-stressed conditions, and no distinct nitrite accumulation was observed when the initial TC concentration was as high as 10 mg/L, indicating the effective detoxification of FeS. The detoxification effects in the FeS autotrophic denitrification system mainly resulted from the rapid adsorption of TC by FeS and effective degradation of TC, as proven by a relatively higher living biomass area. This study offers new insights into the response of sulfur-based autotrophic denitrifiers to TC stress and demonstrates that the FeS-based autotrophic denitrification process is a promising technology for the treatment of wastewater containing emerging contaminants and nutrients.

Experimental design, RSM and ANN modeling of tetracycline photocatalytic degradation using LDH@CN

The nano-photocatalyst of Cu-Al-Layered Double Hydroxide@Graphitic Carbon Nitride (LDH@CN NPC) was synthesized via a fast and cheap method, characterized, and applied for photocatalytic degradation of tetracycline (TC) antibiotic, as a model of main concern contaminant degradation under visible ray illumination and different conditions of initial TC concentration, irradiation time, photocatalyst dose and pH. The experimentally obtained results were modelled using the approaches of central composite design (CCD) and artificial neural network (ANN) to achieve a more accurate description of the process behaviour. Free radical trapping experiments verify that the holes and superoxide anion radicals were the main active species. Therefore, the high decomposition efficiency (96 %) where the parameters were 30 mgL−1, 7.18, 90 min, and 0.018 g of the mentioned variables, respectively, is attributed to the boosted in production of oxidants species through Z-scheme electron transfer heterojunction. The LC-Mass technique was also used to detect the intermediates and offer the proper pathway for photodegradation of TC. The favourable performance of this photocatalyst may be a promising step forward for prosperous large scale photodegradation of persistent organic pollutants in wastewater treatment plants. Evaluation of the developed models’ performance using several statistics showed a higher predictive capability of the ANN model. Comparison of photocatalytic performance of LDH@CN NPC with other recently developed counterparts highlighted its potential to be regarded as an alternative in the remediation of these categories of pollutants in water bodies.

Facile synthesis and preparation of graphite/chitosan/graphene quantum dots nanocomposite cathode for electrochemical removal of tetracycline from aqueous solution

In this research, graphene quantum dots (GQDs) was synthesized via the facile pyrolysis method. The properties of the prepared GQDs were examined by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), dynamic light scattering (DLS), photoluminescence (PL), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet–visible (UV–Vis) methods. Afterward, the graphite/chitosan/graphene quantum dots (Gr/CS/GQDs) nanocomposite was prepared and used as a cathode electrode in electro-Fenton (EF) process to study the tetracycline (TCL) removal from the aqueous solution. The effect of operational parameters in EF, including current density (mA/cm2), initial pH, initial TCL concentration (mg/L), and process time (min) on the TCL removal efficiency, was investigated via response surface methodology (RSM). The results showed that the optimal values for current density, pH, initial TCL concentration, and process time were 60 mA/cm2, 5, 30 mg/L, and 150 min, respectively. Maximum TCL removal efficiency was 92.98%. FT-IR, XRD, Raman spectroscopy, atomic force microscopy(AFM), SEM, mapping, energy dispersive X-Ray (EDX), Brunauer Emmett Teller (BET), and cyclic voltammetry (CV) analyses were performed to investigate the Gr/CS/GQDs cathode. Finally, gas chromatography–mass spectrometry (GC-MS), total organic carbon(TOC), and atomic absorption spectroscopy (AAS) analyses were performed and the reusability of the Gr/CS/GQDs cathode was investigated.

Adsorption-enhanced sonophotocatalytic removal of tetracycline from water using ceria-zirconia (x)CeO2-(1-x)ZrO2 binary oxide nanocatalyst

Objectives : Tetracycline (TC) antibiotics have a risk of causing gastrointestinal and hepatic disorders and, in rare cases, photosensitivity and deposition in bone tissue.Methods : Therefore, it is urgent to develop a technology that can completely remove TC remaining in the water. In this study, a new type of sonophotocatalytic decomposition system that can efficiently decompose TC, a water-based recalcitrant trace pollutant, was proposed.Results and Discussion : As a sonophotocatalyst, xCeO2-(1-x)ZrO2 (x = 0, 0.25, 0.5, 0.75, and 1) binary nanocomposites were synthesized by hydrothermal methods, followed by X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscope, UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area techniques. Interestingly, the 0.75CeO2-0.25ZrO2 (CZ0.75) nanocomposite had low adsorption and removal ability of TC in the absence of light, but due to the synergistic effect of the material and the advanced treatment system, the remaining TC was removed by 89.2% under sonophoto irradiation for 60 min. For CZ0.75, the effect of operating factors such as initial pH of solution, catalyst dosage, reaction time, initial TC concentration, and ultrasonic intensity was studied and the mechanism was analyzed.Conclusion : In addition, through LC-MS analysis, intermediate products obtained in the TC degradation process using the CZ0.75 catalyst and the TC degradation pathway were identified.

Degradation and mineralization of tetracycline by Fenton process

In this study, we aimed to systematically optimize the operating parameters in the degradation and mineralization of tetracycline by Fenton process. For this purpose; optimum values were found for Fe2+ concentration, H2O2 concentration and pH, reaction time, sedimentation times which are effective operating parameters in Fenton process. In this study where initial tetracycline concentration was used as 100 mg/L; optimum values were found as 4 for pH, 30 mg/L for Fe2+ concentration, 100 mg/L for H2O2 concentration and 10 min for reaction time and 90 min for sedimentation time. Under these conditions, the TC degradation was 100%, while the COD removal efficiency was approximately 94%. As a result of kinetic studies, BMG is the most suitable kinetic model in terms of tetracycline degradation, while it is seen that the most suitable kinetic model for tetracycline mineralization in terms of COD is the first-order kinetic model. The cost of removing 1 kg of tetracycline from the unit costs of chemicals and energy used in the Fenton process was found to be 1.527$.

How effective aerated continuous electrocoagulation can be for tetracycline removal from river water using aluminium electrodes?

The study assessed the effects of aeration on continuous electrocoagulation (EC) for tetracycline (TCL) removal from river water. Influence of hydraulic retention time (HRT) and initial drug concentration on treatment efficiency was tested. Best conditions for continuous EC operation were 12 min HRT, electrode spacing 2 cm, 9 V, and Al–Al electrode combination. Highest COD removal with non-aerated EC was 59.4% at 1 mg L−1 initial TCL concentration and further increasing TCL concentration decreased COD removal efficiency. Maximum TCL removal was 66.6% at 10 mg L−1 initial TCL concentration with non-aerated EC. Aerated EC enhanced COD and TCL removal to 61.4% and 71.5%, respectively. In XRD and FTIR spectra no new peaks were detected following EC treatment. XRD, FTIR and FESEM-EDS data supported that significant removal of TCL occurred by charge neutralization, entrapment, adsorption and precipitation driven by Al (OH)3 flocs. Pseudo-second order reaction rate constants explained the kinetics of TCL removal from river water. Sludge volume produced with continuous mode EC non-aerated and aerated EC was 31 cm3 and 39 cm3, respectively. Operating cost was estimated to 0.018 US$/m3 for non-aerated EC and 0.025 US$/m3 for aerated EC. EC can be augmented by aeration for enhanced removal of TCL from river water.

Facile synthesis of cadmium-doped graphite carbon nitride for photocatalytic degradation of tetracycline under visible light irradiation.

In recent years, using semiconductor photocatalysts for antibiotic contaminant degradation under visible light has become a hot topic. Herein, a novel and ingenious cadmium-doped graphite phase carbon nitride (Cd-g-C3N4) photocatalyst was successfully constructed via the thermal polymerization method. Experimental and characterization results revealed that cadmium (Cd) was well doped at the g-C3N4 surface and exhibited high intercontact with g-C3N4. Additionally, the introduction of cadmium significantly improved the photocatalytic activity, and the optimum degradation efficiency of tetracycline (TC) reached 98.1%, which was exceeded 2.0 times that of g-C3N4 (43.9%). Meanwhile, the Cd-doped sample presented a higher efficiency of electrical conductivity, light absorption property, and photogenerated electron-hole pair migration compared with g-C3N4. Additionally, the quenching experiments and electron spin-resonance tests exhibited that holes (h+), hydroxyl radicals (•OH), superoxide radicals (•O2-) were the main active species involved in TC degradation. The effects of various conditions on photocatalytic degradation, such as pH, initial TC concentrations, and catalyst dosage, were also researched. Finally, the degradation mechanism was elaborated in detail. This work gives a reasonable point to synthesizing high-efficiency and economic metal-doped photocatalysts.

Response of immobilized denitrifying bacterial consortium to tetracycline exposure

Tetracycline (TC) as one of the most widely used antibiotics commonly exists in aquaculture tail water and piggery wastewater, causing risks to human. However, the response of immobilized anaerobic denitrifying bacterial consortium to TC exposure lacks systematic research. In this study, the denitrification performance and the compositional shift of extracellular polymeric substances (EPS) and microbial community under TC stress were investigated. The inhabitation effect of TC on nitrate reduction of the immobilized bacterial consortium became evident at high concentrations (50 mg/L and 100 mg/L). Nitrite reduction was more sensitively inhibited than nitrate reduction. The inhabitation effect was mainly due to the fact that TC damaged cell membranes and subsequently effect the intracellular enzymes activities relating to denitrification (NAR and NIR activities). About 50% of TC can be removed by the immobilized bacterial consortium under all tested TC concentrations. Three-dimensional excitation-emission matrix (3D-EEM) results implied that the tryptophan like substances of EPS were obviously quenched with increasing TC concentration. EPS played an important role in TC removal. The denitification performance of the immobilized bacterial consortium under TC stress was attributed to the genera Paraccoccus, Pseudoxanthomonas, Diaphorobacter and Pseudomonas. Initial TC concentration obviously affected the microbial communities. This study may facilitate the management of aquaculture tail water and piggery wastewater contaminated with nitrate and antibiotics.

Activation of peroxydisulfate by black fungus-derived N-doped biochar for tetracycline degradation via non-radical dominated oxidation pathway

N-doped biochar (N-BC) was prepared from black fungus by coupling a hydrothermal method with thermal pyrolysis, and the physicochemical properties of N-BC were characterized in detail by various techniques. As-synthesized N-BC exhibited a better catalytic performance to activate peroxydisulfate (PDS) for tetracycline (TC) degradation compared with as-obtained N-doped hydrochar (N-HC), N-doped calcined carbon (NCC) and most of the reported carbon catalysts. After reaction of 60 min, 89.8% of TC (20 mg/L) was degraded by N-BC/PDS oxidation system, and TC degradation obeyed the pseudo-second-order kinetic with a reaction rate constant at 0.843 L⋅mg−1⋅min−1. The effect of some important parameters (N-BC dosage, PDS dose, initial TC concentration, solution pH, reaction temperature and inorganic anions) on TC degradation was also investigated and analyzed. The radical trapping experiments, EPR test, and electrochemical analysis confirmed that TC degradation in N-BC/PDS system was achieved via the radical (SO4•−, ‧OH) and non-radical (1O2, electron transfer) pathways, and the later played the dominant role. Finally, the performance of N-BC/PDS oxidation system for the removal of TC from the different real water matrices was studied. This study provided a new material for the preparation of highly active PDS catalyst for the treatment of antibiotic wastewater.

Carbon quantum dots decorated Ag/CuFe2O4 for persulfate-assisted visible light photocatalytic degradation of tetracycline: A comparative study

Tetracycline is a broad-spectrum antibiotic largely found in the environment with many adverse effects on environmental and human health. Recently, the coupling of different advanced oxidation processes has been promised as the effective approach for the degradation of refractory pollutants. In this work, the magnetically separable Ag/CuFe2O4/CQDs photocatalyst was successfully synthesized and characterized by X-ray powder diffraction, Differential reflectance spectroscopy, Transmission Electron Microscopy, Field emission scanning electron microscopy, and Energy-dispersive X-ray spectroscopy analysis. The potential of different systems namely photocatalyst/light, photocatalyst/persulfate and photocatalyst/persulfate/light as well as operation parameters, reusability and involved radicals were evaluated for tetracycline degradation. The highest removal efficiency for the different systems was obtained as photocatalyst/persulfate/light (100%, 30 min) > photocatalyst/persulfate (100%, 55 min) > photocatalyst/light (100%, 75 min). The 47% total organic carbon removal was obtained in optimum condition and intermediate products were proposed based on results of liquid chromatography-mass spectrometry. The results indicated that reaction rate constant (Kobs) decreased from 0.1319 to 0.0270 min−1, 0.0332 min−1 and 0.0174 min−1 with increasing pH, initial tetracycline concentration and humic acid (HA), respectively. The inhibitory effect of inorganic ions was obtained as Cl− < NO3− < HCO3−. The nanocomposite showed high reusability after 5 consecutive cycles (91.5%). The results of the scavenger analysis suggest the superoxide and positive hole are the main species involved in tetracycline degradation.

A High Flux Electrochemical Filtration System Based on Electrospun Carbon Nanofiber Membrane for Efficient Tetracycline Degradation

In this work, an electrochemical filter using an electrospun carbon nanofiber membrane (ECNFM) anode fabricated by electrospinning, stabilization and carbonization was developed for the removal of antibiotic tetracycline (TC). ECNFM with 2.5 wt% terephthalic acid (PTA) carbonized at 1000 °C (ECNFM-2.5%-1000) exhibited higher tensile stress (0.75 MPa) and porosity (92.8%), more graphitic structures and lower electron transfer resistance (23.52 Ω). Under the optimal condition of applied voltage 2.0 V, pH 6.1, 0.1 mol L−1 Na2SO4, initial TC concentration 10 ppm and membrane flux 425 LMH, the TC removal efficiency of the electrochemical filter of ECNFM-2.5%-1000 reached 99.8%, and no obvious performance loss was observed after 8 h of continuous operation. The pseudo-first-order reaction rate constant in flow-through mode was 2.28 min−1, which was 10.53 times higher than that in batch mode. Meanwhile, the energy demand for 90% TC removal was only 0.017 kWh m−3. TC could be converted to intermediates with lower developmental toxicity and mutagenicity via the loss of functional groups (-CONH2, -CH3, -OH, -N(CH3)2) and ring opening reaction, which was mainly achieved by direct anodic oxidation. This study highlights the potential of ECNFM-based electrochemical filtration for efficient and economical drinking water purification.

Tetracycline (TC) degradation via hydrodynamic cavitation (HC) combined Fenton's reagent: Optimizing geometric and operation parameters

In this study, the tetracycline degradation was conducted by using hydrodynamic cavitation (HC) device. The influences of Venturi tube parameters (divergence angle, throat length and convergent angle) and the operation conditions (inlet pressure (1.0-5.0 bar), initial tetracycline concentration (5.0-20 mg/L) and addition of some common inorganic anions) on tetracycline degradation were investigated. The results showed that a strong HC effect can be obtained when the Venturi tube with 22° half convergent angle, 2.0 mm throat length and 6.0° half divergence angle is used. The tetracycline degradation ratio can reach 83.17% when inlet pressure and initial concentration were 3.0 bar and 5.0 mg/L, respectively. The tetracycline HC degradation can be intensified by CO32− but inhibited by NO3− and SO42−. Liquid Chromatography-Mass Spectrometry result shows that tetracycline can be decomposed into small molecules in HC process. Total organic carbon reduction testifies that tetracycline can be effectively mineralized into H2O, CO2 and inorganic ions. The addition of Fenton's reagent can further enhance the tetracycline HC degradation efficiency. It is speculated that HC technology assisted by Fenton's reagent can be used for large-scale treatment of antibiotic wastewater.

Synthesis of low-cost Ti4O7 membrane electrode for electrooxidation of tetracycline under flow-through conditions: Performance, kinetics and mechanism

The high cost of anode material and the limitation of liquid-mass transfer on anode surface in electrochemical advanced oxidation processes always restrict the removal efficiency of organics. To overcome the limitations, this study synthesized a low-cost Ti4O7 membrane electrode by simple sol-gel method, and developed a flow-through electrooxidation system based on Ti4O7 membrane electrode. The membrane electrode presented high crystallinity, high specific surface area (10.18 m2/g), concentrated pore sizes distribution (0.1–1 µm), and high oxygen evolution potential (2.2 V vs. SHE). Furthermore, compared with stirring conditions, the flow-through conditions could enhance the liquid-mass transfer on anode surface, resulting in a high tetracycline degradation efficiency (97.24%) and a low energy consumption (0.18 kWh/gDOC). High degradation rates of tetracycline (more than 95%) were both observed with the initial tetracycline concentration ranged from 10 to 50 mg/L. The increase of pipeline pressure and current density had positive influence on tetracycline degradation. Hydroxyl radicals and sulfate radicals produced on the electrode surface are the main oxidants for tetracycline degradation. The degradation pathway of tetracycline included oxygenation, hydroxylation, demethylation, decarbonylation, ring-open, and C-N bond cleavage. Compared with materials prepared by conventional hot pressing and plasma spraying method, this simply synthesized Ti4O7 membrane electrode exhibited efficient oxidation capability and competitive electric cost for contaminants degradation, demonstrating its practicability, feasibility, and facilitation for the potential application.

Catalytic degradation of tetracycline using peroxymonosulfate activated by cobalt and iron co-loaded pomelo peel biochar nanocomposite: Characterization, performance and reaction mechanism

Tetracycline (TC) is a refractory pollutant that widely exists in water environments. Therefore, effective TC treatment methods must be developed. In this work, a cobalt and iron coloaded pomelo peel biochar composite (Co-Fe@PPBC) was successfully synthesized and used to activate peroxymonosulfate (PMS) for TC removal. The crystal structure, surface morphology, pore structure, and elemental valence of the synthesized Co-Fe@PPBC catalyst were investigated by BET, SEM, XRD, FTIR, XPS, TGA, Raman, and VSM. The effects of Co-Fe@PPBC dosage, PMS concentration, initial pH, initial TC concentration, and coexisting anions on TC removal were studied. In comparison with the oxidation (13.6%) by PMS alone and adsorption (9.6%) by Co-Fe@PPBC alone, the removal efficiency of TC was increased to 86.2% in the Co-Fe@PPBC/PMS system, indicating that Co-Fe@PPBC can successfully activate PMS. Remarkably, the results of scavenging examination and EPR analysis demonstrated the synergistic effect of free radical and non-free radical pathways in TC degradation. The cycling test showed that Co-Fe@PPBC has favourable stability and recyclability during repeated activation processes of PMS. Finally, three possible TC degradation methods were presented through the analysis of eight intermediates. Overall, Co-Fe@PPBC could be an economic and high-efficiency catalyst for PMS activation to remove organic pollutants in wastewater.

Removal of tetracycline hydrochloride using S–g-C3N4/PTFE membrane under visible light irradiation

As a type of medicine, tetracycline (TC) is widely used in the world, but it is not easy to degrade due to its poor biochemical properties and stable physicochemical properties. In this work, graphite sulfide carbon nitride compound (S–g-C3N4/PTFE membrane) photocatalyst, formed from a PTFE membrane and graphite sulfide carbon nitride (S–g-C3N4), was prepared for the treatment of TC in wastewater. A variety of characterization methods were used to analyze the catalyst, such as scanning electron microscope (SEM), X-ray diffractometer (XRD), infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), etc. Photocatalytic experiments showed that the photocatalytic degradation extent was 98.1% when the catalyst dosage was 1 ​g/L, the loading of S–g-C3N4 was 50 ​mg, pH was 5 and the initial concentration of TC was 10 ​mg/L. Moreover, S–g-C3N4/PTFE membrane has good recovery performance and photocatalytic stability, and has good degradation performance for most pollutants in urban sewage treatment plants. S–g-C3N4/PTFE membrane will have good application prospects in contaminated water environments because of its advantages of excellent degradation ability, easy regeneration and separation from the water phase.

Preparation of N,S-codoped magnetic bagasse biochar and adsorption characteristics for tetracycline.

Agricultural waste disposal and purification of polluted water are always the key issues of environmental restoration. In this work, thiourea-functionalized magnetic bagasse biochar (MFeBC) was prepared for tetracycline (TC) removal from aqueous solutions. Firstly, MFeBC was prepared by a combined impregnation and chemical coprecipitation method. Furthermore, MFeBC was characterized by Brunauer–Emmett–Teller surface area analysis, Fourier transform infrared spectrometry, X-ray diffraction analysis, scanning electron microscopy, X-ray photoelectron spectroscopy and the magnetic hysteresis curves. For the TC adsorption, the effects of different solution pH level, adsorbent dosage, initial TC concentration and temperature on the adsorption performance were studied respectively. Moreover, the results indicated that the Freundlich isotherm models appropriately described the adsorption process. The kinetic data were better fitted by the pseudo-second-order kinetic model. The maximum TC adsorption capacity of MFeBC reached 69.26 mg g−1. Hydrogen bonding and Π–Π interactions played a dominant role in the adsorption process. Therefore, MFeBC can be used as an effective adsorbent for tetracycline removal from aqueous solution.

Profiling of co-metabolic degradation of tetracycline by the bio-cathode in microbial fuel cells.

In this paper, a system of tetracycline (TEC) degradation by the bio-cathode in a microbial fuel cell (MFC) was constructed. Overall, the co-metabolic degradation performance of TEC was studied through single factor experiments and the ecological risk was evaluated using the E. coli growth inhibition rate and resistance genes. High throughput sequencing (HTS) was utilized to profile the biofilm community structure of the bio-cathode. Results showed that the degradation rate of TEC reached greater than 90% under optimal conditions, which was 10 mg L−1 initial TEC concentration, 0.2–0.7 g L−1 sodium acetate concentration and 12–18 L h−1 aeration. Furthermore, compared with the aerobic biodegradation of TEC, the degradation efficiency of the MFC bio-cathode for TEC was significantly increased by 50% and the eco-toxicity of TEC after 36 hour degradation was reduced by 60.9%, and TEC ARGs in effluent were cut down. HTS results showed that electrochemically active bacteria Acetobacter and TEC-resistant degradation bacteria Hyphomicrobium, Clostridium and Rhodopseudomonas were the main dominant bacteria in the cathode biofilm. Besides, based on 5 intermediates, degradation pathways involving deamidation, denitro dimethylation, dedimethylation and dehydroxylation of TEC were proposed. The degradation of TEC on the bio-cathode was mainly caused by microbial co-metabolism action. This study would enrich the study of MFC bio-cathodic degradation of antibiotics in water.

Adsorption modeling, thermodynamics, and DFT simulation of tetracycline onto mesoporous and high-surface-area NaOH-activated macroalgae carbon

Activated carbon (ENAC) was prepared by NaOH activation, using macroalgae (Enteromorpha clathrate) as raw material. The prepared activated carbon has a large surface area (1238.491 m2 g−1) and its total pore volume and average pore size are 0.6823 cm3g−1 and 2.2038 nm, respectively. The ENAC was characterized by SEM, FTIR, BET and XPS. The effects of contact time (0–960 min), initial tetracycline (TC) concentration (50–500 mg L−1), temperature (30–50 °C) and initial pH (2–11) on TC adsorption were evaluated. The adsorption isotherm and adsorption kinetics were discussed. Results showed that the adsorption isotherm was the Langmuir model, and the adsorption process can be described by the pseudo-second-order model. The N2 adsorption–desorption isotherm was type IV, indicating that the activated carbon had mesoporous structure. Thermodynamic analysis showed that the adsorption process was endothermic and spontaneous. The maximum adsorption capacity of TC was 381.584 mg g−1. Density functional theory (DFT) was used to simulate and analyze the adsorption process, and the influence of different types of N on the adsorption was expounded. The results showed that there are electrostatic interactions, π-π interactions and hydrogen bonding between the adsorbent and TC. These results indicated that the prepared ENAC had a great application prospect in the removal of antibiotics from aqueous solution.

Oxidative degradation of tetracycline using peroxymonosulfate activated by cobalt-doped pomelo peel carbon composite.

Tetracycline (TC) is a typical ecotoxic antibiotic, which easily causes bacterial resistance. Therefore, it is necessary to remove TC from the water environment. In recent years, advanced oxidation processes (AOPs) rely on the use of highly reactive oxidizing sulfate radical which is turning into an increasingly popular as a tool of the removal of TC. In this study, cobalt-doped pomelo peel carbon composite (Co-PPCC) was prepared by the impregnation coprecipitation method to activate peroxymonosulfate (PMS) to remove TC. SEM, BET, XRD, FTIR, XPS, TGA, and other analytical techniques indicated that a carbon composite catalyst with excellent performance has been successfully prepared. TC was removed by the synergistic effect of adsorption and catalytic degradation processes. The adsorption capacity was limited (only approximately 20% within 60 min) and tending to saturation, which indicated that the removal of TC in the Co-PPCC/PMS system was mainly due to oxidative degradation. The influence of the Co-PPCC and PMS dosage, initial TC concentration, initial pH values, and coexisting anions on the removal efficiency of TC was investigated. When the Co-PPCC catalyst dosage was 1 g/L, PMS concentration was 2 g/L, and pH value was 11, the removal efficiency of TC with a concentration of 50 mg/L reached 99% within 60 min. Free radical quenching experiment and electron paramagnetic resonance (EPR) analysis indicated that the free radical and non-radical degradation processes exist in the Co-PPCC/PMS/TC system. The main degradation products and the possible transformation pathways of TC were explored by LC-MS. In addition, after four cycles of Co-PPCC tests, the removal efficiency of TC can reach 64%. This study provides a new method to reuse abandoned pomelo peels and synthesize an economical and environmentally friendly catalyst for activating peroxymonosulfate to remove TC antibiotics in water.

Transformation of Tetracycline by Manganese Peroxidase from Phanerochaete chrysosporium

The negative impacts on the ecosystem of antibiotic residues in the environment have become a global concern. However, little is known about the transformation mechanism of antibiotics by manganese peroxidase (MnP) from microorganisms. This work investigated the transformation characteristics, the antibacterial activity of byproducts, and the degradation mechanism of tetracycline (TC) by purified MnP from Phanerochaete chrysosporium. The results show that nitrogen-limited and high level of Mn2+ medium could obtain favorable MnP activity and inhibit the expression of lignin peroxidase by Phanerochaete chrysosporium. The purified MnP could transform 80% tetracycline in 3 h, and the threshold of reaction activator (H2O2) was about 0.045 mmol L−1. After the 3rd cyclic run, the transformation rate was almost identical at the low initial concentration of TC (77.05–88.47%), while it decreased when the initial concentration was higher (49.36–60.00%). The antimicrobial potency of the TC transformation products by MnP decreased throughout reaction time. We identified seven possible degradation products and then proposed a potential TC transformation pathway, which included demethylation, oxidation of the dimethyl amino, decarbonylation, hydroxylation, and oxidative dehydrogenation. These findings provide a novel comprehension of the role of MnP on the fate of antibiotics in nature and may develop a potential technology for tetracycline removal.