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[Display omitted] • Novel graphitic carbon nitride (g-C 3 N 4) nanodots (CCNDs) were synthesized. • CCNDs applied to the selective and sensitive detection of CTC by AIE-based fluorescence-enhanced effect. • CCNDs were successfully applied to the actual detection of CTC in chicken and feed samples as well as living cells. • The bonding mechanism of CCNDs towards CTC was investigated in detail. In this study, the novel graphitic carbon nitride (g-C 3 N 4) nanodots etched with citrate (CCNDs) were synthesized successfully. And the result CCNDs exhibited an obvious aggregation emission effect (AIE) by forming a fluorescence complex with chlortetracycline (CTC) and significantly enhanced the fluorescence intensity of CCNDs. On the strength of this, the synthesized CCNDs demonstrated remarkable sensitivity and selectivity to CTC, which has been effectively studied and utilized for selectively and sensitively detecting CTC by AIE-based fluorescence-enhanced effect with a detection range spanning from 0 to 15 μM and a limit of detection (LOD) as low as 13 nM. The CCNDs were viably used for actually detecting CTC in real samples including chicken and feed, and further extended to detecting CTC in living cells. Finally, the bonding mechanism of CCNDs towards CTC was investigated in detail by dynamic light scattering (DLS), zeta(ζ) potential, TEM, ultraviolet-visible absorption spectrometry (UV-Vis), resonance light scattering (RLS) and fluorescence lifetime. It is due to the combination of a special fluorescent complex between CCNDs and CTC, which distinguishes CTC from other TCs. [ABSTRACT FROM AUTHOR]

The chlortetracycline (CTC) residue in food poses a threat to human health. Therefore, developing sensitive, convenient and selective analytical methods for CTC detection is crucial. This study innovatively uses tin disulfide/bimetallic organic framework (SnS 2 /ZnCo-MOF) nanocomposites in conjunction with gold nanoparticles (AuNPs) to co-modify a glassy carbon electrode (GCE). Further, a molecularly imprinted polymer (MIP)-based electrochemical sensing platform Au-MIP/SnS 2 /ZnCo-MOF/Au/GCE (AZG) was fabricated for selective CTC detection. SnS 2 /ZnCo-MOF enhanced the stability and surface area of the AZG sensor. The presence of AuNPs facilitated electron transport between the probe and the electrode across the insulating MIP layer. The fixation of AuNPs and MIP via electropolymerization enhanced the selective recognition of this sensor and amplified its output signal. The AZG sensor demonstrated a wide linear detection range (0.1–100 μM), low detection limit (0.072 nM), and high sensitivity (0.830 μA μM−1). It has been used for detecting CTC in animal-origin food with good recovery (96.08%–104.60%). [Display omitted] • Ultrasensitive sensor was successfully developed for selective determination of CTC. • SnS 2 /ZnCo-MOF provided more uptake sites for the loading of CTC template. • AuNPs act as "electron wires" to facilitate electron transfer. • The low LOD and good recovery as well as stability were achieved. • The sensor showed great potential for CTC detection in animal-origin food. [ABSTRACT FROM AUTHOR]

Antibiotics are widely used in clinical medicine due to their excellent antibacterial abilities. As typical emerging pollutants, their misuse can lead to excess antibiotics entering the environment, causing antimicrobial resistance and leading to serious health problems via food chain. Herein, a nano-fluorescent probe based on nitrogen-doped carbon dots (N-CDs) was constructed for the sensitive detection of chlortetracycline (CTC). N-CDs with stable fluorescence were synthesized by hydrothermal method using alizarin red and melamine as raw materials. The N-CDs exhibited significant independence to excitation wavelength. The fluorescence of N-CDs was significantly quenched by CTC ascribing to the fluorescence resonance energy transfer mechanism. The concentration of N-CDs, solution pH and incubation time were optimized to obtain the optimal detection parameters. Under optimal conditions, CTC exhibited excellent linearity over the range of 20–1200 μg/L, and the detection limit was 8.74 μg/L. The method was validated with actual water samples and achieved satisfied spiked recoveries of 97.6–102.6%. Therefore, the proposed method has significant application value in the detection of CTC in waters. [Display omitted] • N-CDs were obtained by hydrothermal method with alizarin red and melamine. • N-CDs based probes exhibited high selectivity for chlortetracycline. • Quenching of CTC fluorescence was contributed to resonance energy transfer. • The constructed probe was sensitive, rapid, robust for detecting CTC. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiZnCo-N-C heterojunction structures composed of bimetallic oxides were prepared. • The catalytic system enabled efficient degradation of tetracycline antibiotics. • All components of the material provided the environment for electron transfer. • NiZnCo-N-C had great d-orbital hybridization used to adsorb CTC and PDS. • NiZnCo-N-C had more oxygen vacancies used to create ·O 2 – and 1O 2. The bimetallic oxides heterojunction structure from new 3D-ZIF was prepared to degrade the chlortetracycline by PDS activation. The system achieved more than 95 % degradation of chlortetracycline within 40 min. Theoretical calculations and physicochemical characterization of the NiZnCo-N-C proved that the material had better electron transfer properties and multi-site reactivity, and the presence of Zn provided an effective intermediate medium for the reaction of Co and Ni, while the non-metallic N-C component also constituted good electron reaction sites. Meanwhile, the existence of abundant oxygen vacancies established the good foundation for the formation of oxygen radicals in the material, and the rapid electron transfer processes speeded up non-radical processes such as electron transfer and 1O 2.The combination of two degradation pathways reduced the impact of environmental factors, the PDS + NiZnCo-N-C system exhibited relatively stable or even better performance in the existence of inorganic anions. Furthermore, the structure of the NiZnCo-N-C had the smallest d-band center, which efficiently adsorbed PDS molecules and broke the O-O bond in PDS. DFT Conclusion and LC-MS of CTC suggested the various reaction processes in the system. Our study provided new solutions and insights for the organic pollutions in the aquatic environment. [ABSTRACT FROM AUTHOR]

A GSH-Se nanozyme, which simultaneously possesses fluorescent and glutathione peroxidase-like activities, was prepared using a one-pot hydrothermal method. This nanozyme can be used for fluorescence-enhanced detection or imaging of CTC in food and cells. [Display omitted] • Novel GSH-Se nanozyme shows dual fluorescence and peroxidase-like activities. • Enhanced GSH-Se fluorescence detects chlortetracycline (CTC) sensitively and selectivity. • Low toxicity, GSH-Se enables real-time CTC monitoring in cells. Developing rapid monitoring methods to detect antibiotic residues in food plays an important role in safeguarding human health. This study presents the development of a novel fluorescence-enhanced detection method for chlortetracycline (CTC) using a GSH-Se nanozyme. A GSH-Se nanozyme prepared using a one-pot hydrothermal method not only possesses excellent fluorescent properties but also exhibits good glutathione peroxidase-like activity. The results show that the addition of CTC leads to a significant enhancement in the fluorescence intensity of GSH-Se, and this increase exhibits a good linear relationship with the concentration of CTC. The linear range of this method is 0.02–1 µM, and the limit of detection (LOD) for CTC was 0.02 µM. Moreover, the cell toxicity of GSH-Se is low and can be used for monitoring and imaging of CTC in cells, and satisfactory results have been obtained in the analysis of actual food samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • The spontaneous binding behavior of CTC to casein was revealed for the first time. • Binding sites engaged in the formation of the casein-CTC complex were deciphered. • The complexation between casein and CTC inhibited the thermal degradation of CTC. Bovine casein was selected as a model protein to evaluate the impact of food matrix on the thermal degradation of antibiotics. Fluorescence quenching and isothermal titration calorimetry experiments revealed that chlortetracycline (CTC) could spontaneously bind to casein via hydrogen bonding and hydrophobic interactions. The amino acid residues forming the binding pocket were further identified using molecular docking, while saturation transfer difference NMR deciphered that the binding of CTC engages its -N(CH 3) 2 group. Moreover, the degradation behavior of free CTC versus that bound in casein-CTC complex was compared during thermal treatment. Compared with free CTC, a lower first-order rate constant was observed in the presence of casein. Removal of casein shortened the half-life of CTC by at least 48.1% at low concentrations. Elucidating that the formation of protein-antibiotic complexes alters the amenability of antibiotics to degradative reactions, which could help eliminate residual antibiotics and guarantee the safety of dairy products. [ABSTRACT FROM AUTHOR]

Among the tetracycline antibiotics, chlortetracycline (CTC) is the most frequently used antibiotic except for tetracycline (TC) for enhancing the ability of the organism to fight bacterial infections. The poor metabolism and degradability of CTC can cause serious health effects. Most studies have focused on the detection and analysis of TC, and research on CTC is relatively scarce. This is because the structures of CTC and TC and oxytetracycline (OTC) are extremely similar, and even indistinguishable. In this study, CTC was used as a template molecule and a molecularly imprinted layer was coated on the surface of highly fluorescent N-CDs using a reversed-phase microemulsion method to form N-CDs@MIPs. It was possible to specifically identify CTC without the influence of TC and OTC, which are extremely similar in structure. By comparing with the non-imprinted polymer (N-CDs@NIPs), it exhibited high sensitivity and selectivity with an imprinting factor of 2.02. And it was used in the determination of CTC in milk with recoveries and relative standard deviations of 96.7%–109.8% and 0.64%–3.27%, respectively, with high accuracy and precision. The specificity of the measurement is excellent compared with other assays, and it is a valid and reliable assay. [Display omitted] • Identify CTC specifically from the extremely similar structures of CTC, TC and OTC. • N-CDs@MIPs accurately detect CTC by a test signal and a validation signal. • The MIT was introduced, which is a source of high selectivity. • The synthesized N-CDs@MIPs retain the highly fluorescent properties of N-CDs. [ABSTRACT FROM AUTHOR]

Chlortetracycline (CTC), a widely used typical tetracycline antibiotic, has raised increasing concerns due to its potential health and environmental risks. Biodegradation is considered an effective method to reduce CTC in environment. In this study, a strain Aspergillus sp. LS-1, which can efficiently degrade CTC, was isolated from CTC-rich activated sludge. Under optimal conditions, the maximum removal efficiency of CTC could reach 95.41%. Temperature was the most significant factor affecting the degradation efficiency of LS-1. The 19 products were identified in the CTC degradation by strain LS-1, and three degradation pathways were proposed. All the degradation pathways for CTC exhibited ring-cleaving, which may accelerate the mineralization of CTC. To gain more comprehensive insights into this strain, we obtained the genome of LS-1, which had high GC content (50.1%) and completeness (99.3%). The gene annotation revealed that LS-1 contains some vital enzymes and resistance genes that may carry functional genes involved in the CTC degradation. In addition, other antibiotic resistance genes were found in the genome of LS-1, indicating that LS-1 has the potential to degrade other antibiotics. This study provides a more theoretical basis for the investigation of CTC degradation by fungi and new insights into the biodegradation of CTC. [Display omitted] • Aspergillus sp. LS-1 can degrade chlortetracycline 95.41% within 72h. • Temperature was the most significant factor affecting the degradation efficiency. • LS-1 contains enzymes and resistance genes involved in CTC degradation. • Three potential biodegradation pathways of chlortetracycline were proposed. [ABSTRACT FROM AUTHOR]

Four robust Cd(II)-CPs can be acted as sensitive dual-responsive sensors for Co2+/Hg2+ and chlortetracycline in water with excellent selectivity and recyclability. The quenching mechanism of four CPs were investigated in detail. [Display omitted] • Four new ternary Cd(II)-CPs were synthesized and characterized. • 1 and 3 exhibited selective sensing for chlortetracycline and Hg2+. • 2 and 4 exhibited selective sensing for chlortetracycline and Co2+. Four new ternary Cd(II) coordination polymers (CPs) based on rarely-used 2-(pyridin-2-yl)-1-(pyridin-3-ylmethyl)-1 H -benzo[ d ]imidazole (L) were synthesized via hydrothermal method, namely {[Cd(L)(H 2 DOBDC)]·H 2 O} n (1), {[Cd(L)(TP)]·2H 2 O} n (2), [Cd 2 (L)(DCTP) 2 (H 2 O)] n (3) and {[Cd 2 (L)(NDA) 2 ]·H 2 O} n (4) (H 4 DOBDC = 2,5-dihydroxy terephthalic acids, H 2 TP = terephthalic acid, H 2 DCTP = 2,5-dichloroterephthalic acid and H 2 NDA = 1, 4-naphthalenedicarboxylic acid). 1 and 2 are 4-connected 2D sql layers, in which 2 is further expanded into a 3D supramolecular network by π − π stacking interaction, while 3 and 4 exhibit three-dimensional frameworks with unusual topology. 1 and 3/2 and 4 can act as dual-functional fluorescent sensors for the sensing of Hg2+ / Co2+and chlortetracycline (CTC) with response times of 30 s for Hg2+ / Co2+ and 20 s for CTC, respectively, in which 2 and 3 as promising fluorescence probes for analytes with detection limits of 1.44 and 0.91 μmoL/L, 3.34 and 0.66 μmoL/L, respectively. The fluorescence sensing mechanism was discussed in detail. [ABSTRACT FROM AUTHOR]

Here we demonstrated that the Co doped anatase titanium dioxide (Co@TiO 2) prepared by a facile wet chemical method could activate peroxymonosulfate (PMS) for efficiently degrading a wide range of refractory organic pollutants. The characterization results demonstrated that the doped Co replaced partial Ti while did not bring obvious structural change. The Co@TiO 2 /PMS system can efficiently remove about 100 % chlortetracycline (CTC) within 40 min and 100 % Rhodamine B (RhB) within 15 min. The Co@TiO 2 /PMS/CTC system maintained a good catalytic performance over a wide pH range from 3 to 11 and the removal efficiency of CTC improved with increasing pH. The Co@TiO 2 /PMS system had a good anti-interference ability, which was free from interference by inorganic ions (such as H 2 PO 4 2-, NO 3 - and SO 4 2-, etc.) and HA, and also in the different real water matrixes and refractory organic pollutants. Quenching experiments and electron spin resonance (EPR) measurements confirmed that the system had a typical radical process as hydroxyl radical (•OH), sulfate radical (SO 4 •−) and superoxide radical (O 2 •−) were the main reactive species for the degradation of CTC. Furthermore, the Co@TiO 2 also showed excellent stability and low metal leaching during long-term use because of the excellent chemical and physical stability of TiO 2. A Co-doped anatase TiO 2 catalyst was synthesized by a facile wet chemical strategy and used for degrading various organic contaminants via peroxymonosulfate activation. [Display omitted] • Co doped anatase TiO 2 was prepared by a facile wet chemical method. • Effects of doping amount and annealing temperature were studied. • Co@TiO 2 /PMS system noticeably removed 100 % CTC under a broad conditions within 40 min • The system had a typical radical process as •OH, SO 4 •− and O 2 •− were the main reactive species. • The fantastic adaptability of the Co@TiO 2 /PMS system was also demonstrated. [ABSTRACT FROM AUTHOR]

Tetracyclines continue to be important antimicrobials in veterinary medicine. However, the pharmacokinetics (PK) of tigecycline (TIG) and minocycline (MIN) in broiler chickens has not been investigated to date, and the PK of chlortetracycline (CTC) and tetracycline (TET) remains insufficiently researched, especially in terms of absorption. These antimicrobials have never been compared in a single setting in a single species; therefore, the aim of the present study was to compare the PK of TIG, MIN, CTC, and TET in broiler chickens. Each drug (10 mg/kg) was administered intravenously (IV) and orally (PO). The plasma concentrations of each drug were determined by liquid chromatography-tandem mass spectrometry, and the results were analyzed using compartmental and noncompartmental PK models. Despite the fact that all of the studied antimicrobials were administered at an identical IV dose, the area under the concentration-timecurve between zero and the last sampling point (AUC0/t) for MIN (35,014 6 3,274 mg ! hour/mL) and CTC (41,851 6 10,965 mg ! hour/mL) differed significantly fromthat determined forTIG(18,86664,326 mg!hour/ mL) and TET (17,817 6 4,469 mg!hour/mL). After IV administration, the values of AUC0/t were also directly related to total body clearance values which were significantly higher forTIG(0.5660.14 L/hour!kg) andTET (0.60 6 0.14 L/hour!kg) than for CTC (0.256 0.05 L/ hour!kg) and MIN (0.2960.03 L/hour!kg). In turn, after PO administration, TIG was absorbed in only 1.55% 6 0.82, and CTC in 30.54% 6 6.99, whereas the bioavailability of MIN and TET was relatively high at 52.33% 6 3.92 and 56.45% 6 9.71, respectively. The differences in PK parameters between these drugs, despite their structural similarities, suggest that active transport mechanisms may play a role in their absorption and distribution. [ABSTRACT FROM AUTHOR]

The changes of enzyme activities, microbial community structure and function, and the diversity and resistance level of antibiotic-resistant bacteria (ARB) were studied in soil during ten repeated treatments with chlortetracycline (CTC) and/or ciprofloxacin (CIP) together with organic manure (OM) under laboratory conditions. The activities of neutral phosphatase (NPA) and catalase (CAT) displayed the suppression-recovery-stimulation trend in the OM&CTC treatment but the stimulation trend in the OM&CTC&CIP treatment. The NPA was stimulated but the CAT was little affected in the OM&CIP treatment. Soil microbial functional diversity displayed the suppression-recovery-stimulation trend in the OM&CTC and OM&CTC&CIP treatments and the stimulation-suppression trend in the OM&CIP treatment with the treatment frequency. Metagenomic analysis showed that the relative abundances of Actinobacteria and Firmicutes in the antibiotic treatment significantly increased by 0.5–235.6%, but that of Proteobacteria decreased by 0.2–27.3% compared to the control with the treatment frequency. Furthermore, the relative abundances of dominant bacterial genera including Streptomyces , Actinomadura , Mycobacterium , and Streptococcus in the antibiotic treatment significantly increased by 1.1–10433.3% compared to the control. Meanwhile, repeated antibiotic treatments induced a significant increase in the diversity and resistance level of ARB isolates, especially in the OM&CTC treatment. It is concluded that repeated treatments with CTC and/or CIP can alter enzyme activities, microbial community structure and function, and increase the diversity and resistance level of ARB isolates. Image 1 • The suppression-recovery-stimulation trend in the NPA and CAT was found in the OM&CTC treatment. • The stimulation trend in the NPA was found in the OM&CIP and OM&CTC&CIP treatments. • The suppression-recovery trend in soil microbial functional diversity was found in the antibiotic treatments. • Repeated antibiotic treatments altered the soil microbial community structure. • Repeated antibiotic treatments significantly increased the diversity and resistance level of ARB isolates. [ABSTRACT FROM AUTHOR]

Abstract Tetracyclines belong to antimicrobial classes with the highest consumption in veterinary medicine and agriculture, which leads to the contamination of the environment and food products, as well as to antibiotic resistance and adverse drug reactions. Chloro-derivatives of tetracyclines are thought to be relatively more phototoxic than others and belong to the most frequently cited drugs as photosensitizers. Melanins are heterogenous biopolymers determining skin, hair and eye colour. They are biosynthesized in a multistep process in melanocytes. Melanins, besides photoprotective and antioxidant properties, may also contribute to adverse skin drug reactions, which involve e.g. hyperpigmentation disorders and phototoxic reactions. Furthermore, they have the ability to form a drug-melanin complex, which leads to deposition of the drug or its metabolites in pigmented tissues. The aim of the study was to examine the ability of chlortetracycline to form a complex with melanin, as well as the effect of the drug on viability, antioxidant defence system and melanogenesis in normal human epidermal melanocytes exposed to the UVA radiation. The obtained results show for the first time that chlortetracycline forms a complex with melanin polymers, which creates a possibility of the drug accumulation in pigmented tissues. A simultaneous exposition of normal melanocytes to chlortetracycline and to the UVA radiation decreases cell viability, proportionally to the drug concentration and the irradiation time. The phototoxic effect appears to be related to the induction of oxidative stress in melanocytes, mainly through an increase of SOD and a decrease of the CAT activity. Chlortetracycline itself does not influence the melanin content or the activity of tyrosinase. The UVA radiation appeared to be a conditioning factor stimulating melanogenesis, whereas the presence of the drug augmented this effect. Graphical abstract Image 1 Highlights • Chlortetracycline forms a complex with melanin polymers. • Chlortetracycline causes concentration-dependent decreases in melanocyte viability. • Chlortetracycline and UVA irradiation induces oxidative stress in melanocytes. • Chlortetracycline doesn't induce melanin synthesis in cells unexposed to UVA. • The phototoxicity of chlortetracycline manifests in the induction of melanogenesis. [ABSTRACT FROM AUTHOR]

Abstract Algae, which are ubiquitous in surface waters (e.g., lakes, ponds, wetlands) may play an important role in sunlight-driven transformation of compounds. This study is to investigate the role of algae (Chlorella Vulgaris) in chlortetracycline (CTC) photolysis and explore the photosensitive mechanism. The algae were found to significantly accelerate the photodegradation rate of CTC and extracellular organic matters (EOMs) were confirmed to be the major active substances. Triplet state EOMs (3EOMs*) were verified to be the dominant reactive species with 93% contribution to the indirect photodegradation rate of CTC, while ·OH and 1O 2 contributed minor (7%). The steady-state concentration of 3EOMs* was determined by probe compounds (2,4,6-trimethylphenol) to be 3.50 × 10−14–1.88 × 10−13 M with the increase of EOMs from 2.0 to 8.0 mg L−1. The rate constant for reaction of 3EOMs* with CTC was calculated to be 3.17 × 109 M−1s−1. 3EOMs* were found to react with CTC mainly via electron transfer, on basis of susceptible reaction of 3EOMs* with the hydroxyl and amidogen groups in CTC. In addition, the energy transfer of 3EOMs* to CTC was possible according to the higher energy of 3EOMs* than that of triplet CTC. Graphical abstract Image 1 Highlights • Chlorella Vulgaris could significantly accelerate the rate of CTC photolysis. • Algogenic EOMs were determined to be the dominant photosensitizer. • Triplet state EOMs (3EOMs*) contributed 93% to indirect photolysis of CTC. • 3EOMs* reacted with CTC mainly via electron transfer and energy transfer. [ABSTRACT FROM AUTHOR]

Abstract Due to the widespread use of antibiotics in healthcare and livestock production, antibiotic resistance genes and residual antimicrobials would enter environment and further discharge into the municipal sewage system. The objective of this work was to explore the potential effect of chlortetracycline (CTC) on biological nutrient removal from wastewater. Thus, the effects of CTC on biological phosphorus and nitrogen removal were investigated with respect to the viability of bacteria, the activities of key metabolic enzymes, and the transformations of intermediate metabolites. Results showed that the presence of 0.1 mg·L−1 CTC did not show any impact on biological phosphorus and nitrogen removal. Nevertheless, the long-term exposure to 1 and 10 mg·L−1 CTC decreased TN removal efficiency from 77.4% to 64.1% and 53.4%, respectively. Meanwhile, the presence of 10 mg·L−1 CTC decreased the SOP removal efficiency from 96.3% to 78.1%. Mechanism studies indicated that CTC could affect the activities of reductase and the transformations of polyhydroxyalkanoates and glycogen, resulting in inhibition of denitrification and phosphorus uptake, which may be the major reason for the high level of CTC showing adverse influence on wastewater biological nutrient removal. Graphical abstract This study showed the long-term exposure to mg·L−1 CTC inhibited denitrification and phosphorus uptake by affecting the transformations of PHAs and glycogen and decreasing the activity of NIR. Unlabelled Image Highlights • The high level of CTC could affect nitrogen and phosphorus removal. • Microbial enzymatic activities were analyzed at different CTC concentration. • Nitrogen and phosphorus removal rate was related to microbial enzymatic activity. • The transformations of PHAs and glycogen were suppressed by CTC addition. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the removal of chlortetracycline (CTC) antibiotic using sulfate radical-based oxidation process. Sodium persulfate (PS) was used as a source to generate sulfate radicals by homogeneous (Fe 2+ ) and heterogeneous (zero valent iron, ZVI) iron as a catalyst. Increased EDTA concentration was used to break the CTC-Fe metal complexes during CTC estimation. The influence of various parameters, such as PS concentration, iron (Fe 2+ and ZVI) concentration, PS/iron molar ratio, and pH were studied and optimum conditions were reported. CTC removal was increased with increasing concentration of PS and iron at an equal molar ratio of PS/Fe 2+ and PS/ZVI processes. PS/Fe 2+ and PS/ZVI oxidation processes at 1:2 (500 μM PS and 1000 μM) molar ratio showed 76% and 94% of 1 μM CTC removal in 2 h. Further increased molar ratio 1:2 onwards, PS/Fe 2+ process showed a slight increase in CTC degradation whereas in PS/ZVI process showed similar degradation to 1:2 (PS/Fe) ratio at constant PS 500 μM concentration. Slower activation of persulfate which indirectly indicates the slower generation of sulfate radicals in PS/ZVI process showed higher degradation efficiency of CTC. The detected transformation products and their estrogenicity results stated that sulfate radicals seem to be efficient in forming stable and non-toxic end products. [ABSTRACT FROM AUTHOR]

Nano micro-electrolysis materials with loading copper were synthesized by a modified reduction method under inert atmosphere and characterized with XRD, BET, SEM and SEM mapping. The effects of nano micro-electrolysis material types, initial pH, nano micro-electrolysis material with loading copper dosage, and initial chlortetracycline concentration on chlortetracycline removal were evaluated. Batch studies results indicated that the maximum removal and total organic carbon removal of chlortetracycline were found to be 99.1% and 70.7% under the optimal conditions of m = 0.5 g/L, pH = 3.6 and C 0  = 50 mg/L. The degradation mechanisms and kinetics were investigated, and the two constants model was discovered to be reasonable fit for the experimental data kinetic model with initial chlortetracycline as variables. These results demonstrated that nano micro-electrolysis materials with loading copper could potentially be used for chlortetracycline removal. [ABSTRACT FROM AUTHOR]

Chlortetracycline (CTC) is widely used as a veterinary antibiotic and is considered as a recalcitrant pollutant. In this study, spiked CTC (2 mg L −1 ) in wastewater was degraded using laccase from the white rot fungi, Trametes Versicolor combined with ultrasonication (UlS). Over 60% of CTC was removed in 2 h by UlS assisted laccase (UAL) treatment where laccase treatment alone took 2 days to degrade 87% of CTC under similar CTC concentration (2 mg L −1 ), laccase dose (0.5 IU) and pH 6.0 conditions. UAL treatment showed 5.3 folds higher CTC degradation rate compared to laccase alone treatment at pH 6.0. Further, pH optimization of UAL treatment was done and pH 4.5 was found to be optimum wherein 80% of CTC degradation was obtained which is 2.6 folds higher compared to degradation at pH 6.0. The UAL treatment with optimized pH was not only increased CTC degradation efficiency (∼80%) but also reduced the degradation time to 2 h. The obtained results highlighted the enhanced degradation rate, efficiency and unaltered stability of laccase during UAL treatment which can be used for oxidizing other tetracycline groups of antibiotics. Moreover, laccase and UAL treatments showed similar degradation products and no estrogenic activity. [ABSTRACT FROM AUTHOR]

Chlortetracycline is (CTC) is a tetracycline antibiotic which is being in the white-tailed deer industry to improve production and animal health. In this paper, we present a method for determining chlortetracycline residues in edible white-tailed deer tissues, using liquid chromatography with heated electrospray ionization and mass spectrometry detection. The procedure involved extraction with EDTA-McIlvaine buffer at pH 4.0, followed by solid-phase extraction cleanup using a hydrophilic-lipophilic balance (HLB) cartridge. The liquid chromatography analysis was performed with heated electrospray ionization and mass spectrometry detection. The limit of quantification for the method was 2.7 ng/g and limit of detection was 0.8 ng/g. The recovery values were >78.5% for muscle, 65.1% for kidney, 63.1% for liver. Mean tissue residue concentration of chlortetracycline and it's epimer, 4-epi chlortetracycline (4-epi-CTC) at 10-day withdrawal period for kidney, liver, muscle was 122.8, 44.7 and 26.7 ng/g, respectively. Chlortetracycline tissue residue concentration at 45-day withdrawal period for kidney, liver, muscle was 19.2, 28.9 and 10.7 ng/g, respectively. Mean tissue concentration of CTC was less than the established maximum residual limit (MRL) values for bovine tissues. We have validated and successfully applied this method in the qualitative and quantification of chlortetracycline in white-tailed deer tissue samples. [ABSTRACT FROM AUTHOR]

The short- and long-term effects of chlortetracycline (CTC) on the nitritation- anaerobic ammonium oxidation (anammox) process were evaluated. The half maximal inhibitory concentration of CTC in the batch tests of the nitritation-anammox process was 278.91 mg/L at an exposure time of 12 hr. The long-term effects of CTC on the process were examined in a continuous-flow nitritation-anammox reactor. Within 14 days, the nitrogen removal rate significantly decreased from 0.61 to 0.25 kg N/m 3 /day with 60 mg/L CTC in the influent. The performance suppressed by CTC barely recovered, even after CTC was removed from the influent. Furthermore, the inhibition of CTC also reduced the relative abundance of ammonium oxidizing bacteria (AOB) and anaerobic ammonium oxidizing bacteria (AnAOB) in the reactor, resulting in both a decreased amount of and an imbalance between AOB and AnAOB. When fresh anammox sludge was reseeded into the nitritation-anammox reactor, the nitrogen removal rate recovered to 0.09 ± 0.03 kg N/m 3 /day. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel flexible high active polymer ZnCoO@PVDF membranes with high piezo-catalytic efficiency piezo-catalysis was preparation. • Zn 0.8 Co 0.2 O@PVDF membranes showed best piezoelectric coefficient of 44.7 pC/N under ultrasonic conditions. • The piezo-catalytic efficiency is enhanced by improving of β-phase PVDF with the introducing of ZnCoO. • Zn 0.8 Co 0.2 O@PVDF membranes showed excellent degradation and reuse efficiency for the removal of chlortetracycline. • The Zn 0.8 Co 0.2 O@PVDF piezoelectric membranes can be easily recycled and exhibits excellent cycle stability. Piezo-catalysis technology is considered an emerging technology to remove organic pollutants from wastewater. In this study, a ZnCoO@PVDF membranes with high-voltage electrical properties was prepared for the piezo-catalytic degradation of chlortetracycline (CTC) in wastewater. The entry of Co into the main lattice of ZnO changes the electrical properties of ZnO. The d 33 test shows that Co increases the piezoelectric coefficient of ZnO by 6.5 times. Under ultrasonic conditions, the Zn 0.8 Co 0.2 O@PVDF membranes exhibit the best piezo-catalytic activity, with a degradation rate constant of 0.2027 mM−1, which is 34.94 times higher than that of pure PVDF. At the same time, the doping of Zn 0.8 Co 0.2 O caused the change of the crystal form of PVDF, the β phase with piezoelectric properties increased significantly, and the piezoelectric coefficient increased from 27.3 pC/N of PVDF to 44.7 pC/N. Multiple by-products and degradation pathways were identified using LC-MS, and two main degradation pathways were proposed based on density functional theory (DFT) calculations. The toxicity of CTC and its by-products was estimated using Toxicity Estimation Software Tool (TEST) software, which further confirmed the reduction of environmental risk after piezoelectric catalytic degradation. This study provides new insights into the efficient piezo-catalytic treatment of antibiotic wastewater. [ABSTRACT FROM AUTHOR]

A 1D zigzag chain Cd(II) coordination polymer [Cd(L) 2 (tcpa)] n (1) was synthesized under hydrothermal condition. Furthermore, 1 presented fluorescence probe to detect chlortetracycline in aqueous solution and could be reused five times without significantly decrease. [Display omitted] • A 1D zigzag chain Cd(II) coordination polymer based bis(2-methylbenzimidazol) was obtained. • 1 can as a promising fluorescence probe to detect chlortetracycline in aqueous solution. • The fluorescent sensing mechanism of 1 was discussed. A 1D zigzag chain Cd(II) coordination polymer (CP), [Cd(L) 2 (tcpa)] n (1) (L = 1,3-bis(2-methylbenzimidazol-1-yl)-2-propanol, H 2 tcpa = tetrachloroterephthalic acid) was hydrothermally synthesized and characterized. 1 can be a promising fluorescence probe to detect chlortetracycline (CTC) with a limit of detection of 2.3 × 10−8 mol/L. 1 could be reused five times. Further, the fluorescent sensing mechanism of 1 was discussed. [ABSTRACT FROM AUTHOR]

Swine manure was typical for the combined pollution of heavy metals and antibiotics. The effects of widely used veterinary antibiotic chlortetracycline (CTC), Cu and their combination on swine manure anaerobic digestion performance and microbial community have never been investigated. Thus, four 2 L anaerobic digestion reactors were established including reactor A (control), B (CTC spiked by 0.5 g/kg dry weight, dw), C (Cu spiked by 5 g/kg dw) and D (combination of CTC, 0.5 g/kg dw, and Cu, 5 g/kg dw), and dynamics of bacterial and archaeal community structure was investigated using high throughput sequencing method. Results showed that addition of CTC and Cu separately could increase the total biogas production by 21.6% and 15.8%, respectively, while combination of CTC and Cu severely inhibited anaerobic digestion (by 30.3%). Furthermore, corresponding to different stages and reactors, four kinds of microbes including bacteria and archaea were described in detail, and the effects of CTC, Cu and their combination mainly occurred at hydrolysis and acidification phases. The addition of Cu alone changed the dynamics of archaeal community significantly. It was genus Methanomassiliicoccus that dominated at the active methane production for A, B and D, while it was genus Methanobrevibacter and Methanoculleus for C. [ABSTRACT FROM AUTHOR]

The individual and combined toxicities of chlortetracycline (CTC), oxytetracycline (OTC) and enrofloxacin (ENF) have been examined in two green algae representative of the freshwater environment, the international standard strain Pseudokichneriella subcapitata and the native strain Ankistrodesmus fusiformis . The toxicities of the three antibiotics and their mixtures were similar in both strains, although low concentrations of ENF and CTC + ENF were more toxic in A. fusiformis than in the standard strain. The toxicological interactions of binary mixtures were predicted using the two classical models of additivity: Concentration Addition (CA) and Independent Action (IA), and compared to the experimentally determined toxicities over a range of concentrations between 0.1 and 10 mg L −1 . The CA model predicted the inhibition of algal growth in the three mixtures in P. subcapitata , and in the CTC + OTC and CTC + ENF mixtures in A. fusiformis . However, this model underestimated the experimental results obtained in the OTC + ENF mixture in A. fusiformis . The IA model did not predict the experimental toxicological effects of the three mixtures in either strain. The sum of the toxic units (TU) for the mixtures was calculated. According to these values, the binary mixtures CTC + ENF and OTC + ENF showed an additive effect, and the CTC + OTC mixture showed antagonism in P. subcapitata , whereas the three mixtures showed synergistic effects in A. fusiformis . Although A. fusiformis was isolated from a polluted river, it showed a similar sensitivity with respect to P. subcapitata when it was exposed to binary mixtures of antibiotics. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) has been applied to animal manure stabilization, and antibiotics is frequently found in animal manure. However, antibiotic degradation and microbial community structures during two-stage AD (acidification and methanogenesis) remain poorly understood. This experiments on two-stage anaerobic swine manure digesters were performed to investigate the degradation mechanisms and effects of chlortetracycline (CTC) and oxytetracycline (OTC) on microbial community structures. Results showed that acidification and methanogenesis showed good degradation performance for manure containing CTC and OTC at 60 and 40 mg/kg·TS, respectively. CTC and OTC were degraded by 59.8% and 41.3% in the acidogenic stage and by 76.3% and 78.3% in the methanogenic stage, respectively. CTC and OTC negatively affected bacterial community in methanogenic and acidogenic stages, respectively. They also adversely influenced the archaeal species in the methanogenic stage. Two-stage AD was proposed to treat manure containing antibiotics and to reduce the negative effects of antibiotics on AD. [ABSTRACT FROM AUTHOR]

After applying for many years, antibiotics, such as chlortetracycline (CTC), have been widely detected in aquatic environment. The persistence and toxicity effect of them ungently calling for better solution. In this study, CuO nanosheet-liked structure has been successfully synthesized through a C 3 N 4 templating method with the presence of benzyl alcohol and sodium citrate by assembling small CuO nanoparticles onto the surface of C 3 N 4 nanosheet. Because of the C 3 N 4 -liked structure, narrowing band gap, enhanced visible light absorption and decreased recombination rate of photogenerated electron-hole pairs, the as-prepared CuO nanosheet-liked structure exhibits an enhanced visible-light photocatalytic activity in the degradation of CTC. Furthermore, Pt nanoparticles with a dimension around 10 nm have been loaded onto the surface of CuO nanosheet-liked structure to enhance the visible-light photoactivity of the photocatalyst. For the first time, the CuO-based photocatalyst can be applied in the photocatalytic degradation of CTC and displays an improved performance while comparing to TiO 2 -based photocatalysts. In particular, nearly 50% concentration of CTC in the solution can be degraded with the presence of Pt/CuO-NS-2 in 120 min. With the synergy effect between H 2 O 2 and Pt/CuO-NS-2, the degradation efficiency and ability of CTC has been further improved. Around 80% of CTC in the solution was degraded in 60 min. [ABSTRACT FROM AUTHOR]

Chlortetracycline (CTC) has been widely applied as antibiotic for years and frequently detected in water. The presence of CTC not only leading inhibition of growth and toxic effect to specific species, but also raising concern for their potential influences of human health. In order to decline the negative effect and water pollution causing by the chlortetracycline (CTC), a novel aerogel named TPGA with 3D structure has been successfully fabricated using graphene oxide (GO), titanium dioxide nanosheets and platinum nanoparticles as raw materials. The structures and properties of this composite are carefully characterized by multiple methods, including TEM, SEM, SRD, EDS, FTIR, DRS and PL. Because of the increased separation and transfer of photogenerated electron-hole pairs, enlarged surface area and improved utilization of visible light, the TPGA composite exhibits an improved photocatalytic activity in the degradation of CTC under visible-light irradiation. In particular, while the m TiO2-NS/Pt : m GO = 0.5, around 45% of CTC in the solution can be degraded in 90 min. [ABSTRACT FROM AUTHOR]

The wide presence of antibiotic chlortetracycline in the environment has aroused increasing ecological and human health concerns. Biodegradation can be a promising strategy to dissipate chlortetracycline. However, there is a paucity of knowledge on the biodegradation of chlortetracycline. The present study investigated the biodegradation of chlortetracycline by a microbial community in liquid culture, the potential intermediates, the influences of temperature, external carbon and nitrogen sources, and the composition of chlortetracycline-degrading microbial community. At the initial chlortetracycline level of 100 |xgl_1, the average removal rates of 48.7% and 84.9% were achieved by acclimated microbial populations in one and four weeks, respectively. Four potential intermediates were identified using LC/MS/MS analysis. Moreover, microbial growth was observed with chlortetracycline biodegradation. Chlortetracycline could be used as sole carbon and nitrogen sources by the microbial community, while temperature rise and addition of external nitrogen source favored chlortetracycline biodegradation. Illumina MiSeq high-throughput sequencing analysis indicated that bacterial community structure considerably changed with the degradation of chlortetracycline. Firmicutes, Proteobacteria and Bacteroidetes were the dominant phylum groups in chlortetracycline-degrading bacterial community. [ABSTRACT FROM AUTHOR]

The heterogeneous photo−Fenton method is a promising technology for wastewater treatment based on the development of efficient catalysts through which the inefficient Fe(III)/Fe(II) cycles and low utilization of H 2 O 2 are optimized. In this work, viable heterogeneous photo−Fenton catalysts (NCS) are synthesized by in situ compounding nitrogen−doped carbon quantum dots (N−CQDs) with schwertmannite (SCH). Specifically, the NCS catalysts exhibit greatly enhanced capacity for chlortetracycline (CTC) degradation, in comparison with those of the pristine SCH and N−CQDs, with a remarkable efficiency of 95.12% at a wide pH range (3.0–7.0). In particular, this allows an efficient Fe(III)/Fe(II) conversion due to the fast electron transport capability provided by N−CQDs, coupled to an excellent structural stability of the catalysts. Main active species including •OH, •O 2 − and 1O 2 are identified in the degradation process, and a possible degradation mechanism is tentatively proposed. In addition, related cytotoxicity of CTC degradation intermediates is verified via co−culturing with E. coli. This study provides a new strategy to overcome the disadvantages of photo−Fenton processes and develop new technologies for advanced water treatment. [Display omitted] • Nitrogen−doped CQDs were combined with SCH to develop photo–Fenton catalysts. • NCS displayed superior activity towards CTC degradation in photo–Fenton systems. • Degradation pathway of CTC and related cytotoxicity of intermediates were revealed. [ABSTRACT FROM AUTHOR]

Tetracycline antibiotics (TCs) and heavy metals are commonly used in livestock and poultry farming, leading to their coexistence in the aquatic environment. This coexistence causes combined toxicity to aquatic organisms. Here, zebrafish embryos were exposed to chlortetracycline (CTC), oxytetracycline (OTC), zinc chloride (ZnCl 2), and their combinations for 120 h to evaluate their adverse effects on the growth, antioxidant system, immune system, and endocrine system during the early stage of life. OTC/ZnCl 2 combined exposure significantly reduced the body weight, whereas the TCs/ZnCl 2 combination significantly increased the heart rate of zebrafish larvae, suggesting growth impairment induced by TCs and ZnCl 2. Further, combined groups showed more prominent toxicity to the antioxidant system than single groups, as revealed by related levels of enzyme activity and gene expression. In addition, the levels of most pro-inflammatory genes were downregulated, and those of NF-κB-related genes were upregulated in all treatment groups, indicating an immunosuppressive response and the potential role of NF-κB signaling, while the combined treatment was not more toxic than TCs or ZnCl 2 alone. Similarly, hormone and endocrine related gene levels were determined. Although both single and combined exposures caused certain endocrine-disrupting effects, the combined exposure did not result in higher toxicity than a single exposure. Our findings showed that a mixture of TCs and ZnCl 2 might exert greater toxic effects as compared to a single compound on some systems, providing fundamental data on the toxic effects of single and combined TC and ZnCl 2 exposure on aquatic organisms, although studies are needed to explore the underlying mechanisms. [Display omitted] • Greater effects on early growth of zebrafish are observed in the combined group. • The combined groups induce more severe oxidative stress in zebrafish larvae. • Single and co-exposure to CTC or OTC and ZnCl 2 both induce immunosuppression and endocrine disruption. [ABSTRACT FROM AUTHOR]

In this work, kinetics, equilibrium, thermodynamic and other adsorption properties of a novel activated carbon with regular-shaped pores (NH 4 Cl-modified activated carbon, NAC) for removal of chlortetracycline antibiotic from aqueous solutions was compared with those of a commercial standard activated carbon (SAC). Effects of temperature, on chlortetracycline adsorption by both adsorbents were carefully investigated and compared. Then optimum conditions were used for comparing the adsorption properties of adsorbents. Among the isotherm models studied, the equilibrium experimental data of both activated carbons were followed by Redlich-Peterson model, and the parameters calculated from the studied models showed more favourability of chlortetracycline adsorption onto NAC via the physical π - π electron-donor-acceptor interaction. The experimental data were fitted to several kinetic models and, based on calculated respective parameters such as rate constants, equilibrium adsorption capacities, correlation coefficients and statistical indices, both the Ritchie second order and pseudo second-order model showed the best in describing the adsorption process for both activated carbons, and the kinetic performance of NAC was significantly higher than that of SAC. The calculated thermodynamic parameters of the adsorption process revealed that, under the conditions used in this study, the adsorption of chlortetracycline onto NAC is more feasible, spontaneous and endothermic than its adsorption onto SAC. Overall, the results indicated that, compared to SAC, NAC is a more suitable choice for removal of chlortetracycline antibiotic from aqueous solutions. [ABSTRACT FROM AUTHOR]

Residual emerging contaminants in wastewater sludge remain an obstacle for its wide and safe applications such as landfilling and bio-fertilizer. In this study, the feasibility of individual ultrasonication (UlS) and Fenton oxidation (FO) and combined, Ferro-sonication processes (FO) on the degradation of chlortetracycline (CTC) in wastewater sludge was investigated. UlS parameters such as amplitude and sonication time were optimized by response surface methodology (RSM) for further optimization of FS process. Generation of highly reactive hydroxyl radicals in FO and FS processes were compared to evaluate the degradation efficiency of CTC. Increasing in the ratio of hydrogen peroxide and iron concentration showed increased CTC degradation in FO process; whereas in FS, an increase in iron concentration did not show any significant effect (p > 0.05) on CTC degradation in sludge. The estimated iron concentration in sludge (115 mg/kg) was enough to degrade CTC without the addition of external iron. The only adjustment of sludge pH to 3 was enough to generate in-situ hydroxyl radicals by utilizing iron which is already present in the sludge. This observation was further supported by hydroxyl radical estimation with adjustment of water pH to 3 and with and without the addition of iron. The optimum operating UlS conditions were found to be 60% amplitude for 106 min by using RSM. Compared to standalone UlS and FO at 1:1 ratio, FS showed 15% and 8% increased CTC degradation respectively. In addition, UlS of sludge increased estrogenic activity 1.5 times higher compared to FO. FS treated samples did not show any estrogenic activity. [ABSTRACT FROM AUTHOR]

A series of mesoporous silicate adsorbents with superior adsorption performance for hazardous chlortetracycline (CTC) were sucessfully prepared via a facile one-pot hydrothermal reaction using low-cost illite/smectite (IS) clay, sodium silicate and magnesium sulfate as the starting materials. In this process, IS clay was “teared up” and then “rebuilt” as new porous silicate adsorbent with high specific surface area of 363.52 m 2 /g (about 8.7 folds higher than that of IS clay) and very negative Zeta potential (− 34.5 mV). The inert Si O Si (Mg, Al) bonds in crystal framework of IS were broken to form Si(Al) O − groups with good adsorption activity, which greatly increased the adsorption sites served for holding much CTC molecules. Systematic evaluation on adsorption properties reveals the optimal silicate adsorbent can adsorb 408.81 mg/g of CTC (only 159.7 mg/g for raw IS clay) and remove 99.3% (only 46.5% for raw IS clay) of CTC from 100 mg/L initial solution (pH 3.51; adsorption temperature 30°C; adsorbent dosage, 3 g/L). The adsorption behaviors of CTC onto the adsorbent follows the Langmuir isotherm model, Temkin equation and pseudo second-order kinetic model. The mesopore adsorption, electrostatic attraction and chemical association mainly contribute to the enhanced adsorption properties. As a whole, the high-efficient silicate adsorbent could be candidates to remove CTC from the wastewater with high amounts of CTC. [ABSTRACT FROM AUTHOR]

In the last years, increasing attention has been paid on the presence of antibiotics in aqueous environments due to their ecological damage and potential adverse effects on organisms. Membrane biofilm reactors (MBfR) have been gained a significant popularity as an advanced wastewater treatment technology in removing of organic micro-pollutants. In this study, the performance of H 2 -MBfR for simultaneous removal of nitrate and chlortetracycline, formation of transformation products and community analysis of the biofilm grown on the gas permeable hollow fiber membranes was evaluated by considering effect of the hydraulic retention time, surface loadings of target pollutants and H 2 pressure. The results showed that the simultaneous chlortetracycline (96%) and nitrate removal (99%) took placed successfully under the conditions of 5 h HRT and 2 psi H 2 pressure. It has been determined that the main elimination process was biodegradation and Betaproteobacteria species was responsible for chlortetracycline degradation. [ABSTRACT FROM AUTHOR]

Molecular modeling of chlortetracycline was performed based on DFT approach implemented in Gaussian software. The differences between simulated electronic spectra and those recorded experimentally were analyzed. Experimental investigations were carried out using electronic absorption spectra as well as fluorescence ones. Spectral shift to the changing of solvent polarity was measured in various solvents (binary solutions) and graphical correlations were evidenced between the electronic band wavenumbers and some theoretical functions on solvent electro-optical macroscopic parameters (refractive index and dielectric constant); interpretation was done based on the solvatochromic theory dedicated to universal interaction forces. Fluorescence spectra, studied in mixture of solvents (ternary solutions), evidenced also specific interactions in water-alcohols not considered in the classical solvatochromic approach. [ABSTRACT FROM AUTHOR]

The presence of pharmaceutically active compounds (PhACs) in water and wastewater has raised concerns because of potential environmental impacts and thus their removal is of high importance. The adsorption behavior of chlortetracycline (CTC) from aqueous solution on raw and activated pinewood biochar was studied at 298 K. The effect of initial pH of the solution was studied by performing the experiment at three different pHs (1, 5 and 9). At each pH, CTC showed varied electrostatic charge (+ 1, 0 and − 1, respectively) which affected its adsorption. The results indicated that CTC followed Langmuir isotherm and the related parameters were calculated. Also, it was observed that the maximum adsorption occurred at pH 1. The adsorption capacity of CTC for raw and activated biochar was at least 2.1 and 208.3 mg/g adsorbent, respectively. The characteristics of biochars were studied using zeta potential analyzer, laser size analyzer and scanning electron microscopy (SEM). The results showed that raw and activated biochars are promising candidates for removal of CTC from water due to the acidic character of pinewood that can result in better interaction with ionizable compounds at lower pHs. [ABSTRACT FROM AUTHOR]

Manure containing antibiotics is considered a hazardous substance that poses a serious health risk to the environment and to human health. Anaerobic digestion (AD) could not only treatment animal waste but also generate valuable biogas. However, the interaction between antibiotics in manure and the AD process has not been clearly understood. In this study, experiments on biochemical methane potential (BMP) were conducted to determine the inhibition of the AD process from antibiotics and the threshold of complete antibiotic removal. The thresholds of the complete antibiotic removal were 60 and 40 mg/kg·TS for CTC and OTC, respectively. CTC and OTC with concentrations below thresholds could increase the BMP of manure. When the CTC and OTC concentrations exceeded the thresholds, they inhibited manure fermentation, and the CTC removal rate declined exponentially with concentration (60–500 mg/kg·TS). The relationship between OTC antibiotic concentration and its removal rate in AD treatment was described with exponential (40–100 mg/kg·TS) and linear equations (100–500 mg/kg·TS). [ABSTRACT FROM AUTHOR]

[Display omitted] • In this paper, the histidine-fabricated copper nanoclusters (Cu NCs@His) was first developed to detect chlortetracycline. • The developed probe exhibited a wide linear range and a lower detection limit towards chlortetracycline. • Quenching mechanisms were the static quenching and inner filter effect. • This proposed method has been applied for the detection of chlortetracycline in real samples. In this study, histidine-protected copper nanoclusters (Cu NCs@His) were established by using a one-pot method, which histidine and ascorbic acid were applied as the template and reducing agent, respectively. The as-developed Cu NCs@His endued green emission wavelength at 494 nm with the excitation of 378 nm. The Cu NCs@His exhibited green fluorescence under UV light (365 nm). Using Cu NCs@His as a pattern nanosensor, the fluorescent "turn off" mechanism was fabricated for the determination of chlortetracycline in the light of the linear decrease of fluorescence intensities around 494 nm. The chlortetracycline conducted as a quencher, leading to reveal an excellent linear relationship between ln(F 0 /F) of Cu NCs@His and chlortetracycline concentrations with the range of 0.5–200 μM, and the detection limit was 0.876 μM. The fluorescence quenching of Cu NCs@His revealed excellent selectivity for chlortetracycline over other potential interfering substances in the human body. This strategy was exhibited to be a convenient sensing platform for the detection of chlortetracycline in real medical samples, which could unfold a brand new and direct system for the sensing of chlortetracycline in real samples. [ABSTRACT FROM AUTHOR]

As an emerging fluorescent nanomaterial, gold nanoclusters are of increasing interest in sensing and imaging because of their stable luminescence properties, large Stokes shift and low toxicity. Here, red-emitting gold nanoclusters stabilized by 6-Deoxy-6-mercapto-β-cyclodextrin (6-SH-CD@Au NCs) were successfully synthesized based on photo-reduction method for the detection of chlortetracycline. Under alkaline conditions, chlortetracycline transforms into iso-chlortetracycline (iso-CTC), which has a distinct blue fluorescence at 415 nm. The fluorescence intensity at 415 nm changed with increasing concentration of chlortetracycline and inner filter effect (IFE) of 6-SH-CD@Au NCs, while the fluorescence of the gold nanocluster at 670 nm decreased due to the IFE of iso-CTC. This fluorescent system detected chlortetracycline with good linearity in the concentration range of 5 nM-1 μM, and the limit of detection is 2.7 nM. The developed fluorescence sensor and test paper assay had been successfully applied for the detection of chlortetracycline in milk samples. The results demonstrated that the ratiometric sensor has advantages of simplicity, high sensitivity and specificity, cost-effectiveness and ease of operation. [Display omitted] • The novel photo-reduction strategy for the synthesis of gold clusters is a simple green process. • The method has good selectivity and sensitivity for chlortetracycline. • The fluorescent sensor was successfully applied to the detection of CTC in milk. [ABSTRACT FROM AUTHOR]

Chlortetracycline (CTC) is a tetracycline derivative antibiotic that has been widely used in the livestock industry for prophylactic and therapeutic purposes. Effective measures should be taken to decrease the environmental risks associated with CTC-rich waste. Biochar produced by biomass waste showed great potential for organic contaminants removal by adsorption and catalytic degradation. This study prepared iron oxide-modified coffee grounds biochar (CGF) at different temperatures for enhanced CTC removal by adsorption and degradation. The main mechanism for CTC removal was found to be electrostatic interaction. In addition, pore diffusion, hydrogen bonds, and π-π bonds also contributed to CTC adsorption. Maximum CTC adsorption capacity was 223.63 mg/g for CGF800 (CGF prepared at 800 °C pyrolysis). The free radical content of CGF600 (CFG prepared at 600 °C pyrolysis) was higher than CGF800, and there were no significant advantages in using biochar prepared at a higher temperature for persulfate activation. The ion mass-to-charge ratio (M/z) is used to describe the ratio of mass to charge of an ion or peak, which can infer compound structure. The structure of CTC degradation products was analyzed by UPLC-MS, and the M/z values were determined as 444, 273, and 154. Thus, pyrolysis of coffee grounds at higher temperatures increased CTC adsorption capacity, and CGF can indirectly assist in CTC degradation by persulfate activation. [Display omitted] • Iron oxide modified biochar was prepared from coffee grounds by pyrolysis. • Maximum CTC adsorption capacity of 223.63 mg/g biochar was attained. • Chemisorption by electrostatic attraction was the main adsorption mechanism. • Persulfate-assisted degradation of CTC improved removal efficiency to 83.48%. • The degradation products were analyzed by UPLC-MS. [ABSTRACT FROM AUTHOR]

A simple co-precipitation method was used to synthesize ibandronate nano-functionalized hydroxyapatite (IB-HAP) and used for the removal of Pb2+/Cu2+ and chlortetracycline. The effects of the amount of modifier IB added, the initial concentration and the pH value of the solution on the adsorption effect of heavy metal ions were investigated. When the P atom in IB accounts for 5% of the total phosphorus, the adsorption capacity of IB-HAP was 1565.3 mg/g (Pb2+) and 246.71 mg/g (Cu2+), respectively. By adding heavy metal ions and chlortetracycline (CTC) in different addition sequences, the co-adsorption effect of various pollutants on IB-HAP was studied. According to microstructure analysis and simulation, the adsorption mechanism was studied from a microscopic point of view. It is the first time that modifiers and pollutants were used as central molecules to study the interaction sites and interaction strengths with surrounding molecules in a wholly covered state by Hirshfeld surface analysis. Finally, the desorption experiments showed that IB-HAP had strong regeneration and sustainability. These results showed that IB-HAP was a potential adsorbent, and this study also provided new guidelines and valuable methods for analyzing the mechanism of co-adsorption of heavy metal ions and antibiotics. [Display omitted] • IB-HAP was synthesized, and its single adsorption capacity was 1565.3(Pb2+) and 246.71(Cu2+) mg/g, respectively. • Different addition sequences would affect the co-adsorption effect of Cu2+/Pb2+ and chlortetracycline. • The interactions in completely surrounded states were firstly studied by Hirshfeld surface analyses. • Hydrogen bond and coordination interaction were the main force for the adsorption process. • IB-HAP had strong regeneration and sustainability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Applied voltage improved performances of AnEMBR in treating high CTC wastewater. • Applied voltage greatly reduced ARGs abundances in effluent of AnEMBR. • HGT and microbial community shift contributed to ARGs proliferation in sludge. • Enriched tetracycline degradation gene at 0.7 V reduced ARGs selection pressure. The spread of antibiotics and antibiotic resistance genes (ARGs) in environments has posed potential threats to public health. Unfortunately, conventional biological wastewater treatment technologies generally show insufficient removal of antibiotics and ARGs. Bioelectrochemical systems, which can effectively degrade refractory organic pollutants via enhancing microbial metabolisms through electrochemical redox reaction, may provide an alternative for the control of antibiotics and ARGs. Herein, an anaerobic electrochemical membrane bioreactor (AnEMBR) was conducted by combining bioelectrochemical system and anaerobic membrane bioreactor to treat antibiotic-containing wastewater. The AnEMBR at open circuit showed stable CH 4 production and high removal of COD and chlortetracycline (CTC) in treating 2.5–15 mg/L CTC. However, increasing CTC to 45 mg/L completely inhibited the methanogenesis of AnEMBR at open circuit. After applying external voltage in AnEMBR, the performances of AnEMBR were significantly improved (e.g. , increased CH 4 production and CTC removal). Moreover, CTC exposure significantly increased the relative abundances of ARGs in sludge, supernatant, and effluent in AnEMBR at open circuit. Applying voltage greatly attenuated the total relative abundances of ARGs in the supernatant and effluent of AnEMBR compared to those at open circuit. This could be attributed to the enrichment of tetracycline degradation gene tetX , which greatly enhanced the removal of CTC by the AnEMBR and thus reduced the selective pressure of CTC on the microorganisms in supernatant and effluent for ARGs proliferation. These results would provide an effective wastewater treatment technology for treating high-level antibiotic-containing wastewater to mitigate the potential risk of ARGs and antibiotics spread in receiving water body. [ABSTRACT FROM AUTHOR]

Microbial degradation of chlortetracycline (CTC) is an effective bioremediation method. In the present study, an enrichment technique was used to isolate a Bacillus cereus LZ01 strain capable of effectively degrading CTC from cattle manure. Response surface methodology was used to identify optimized conditions under which strain LZ01 was able to achieve maximal CTC removal (83.58%): temperature of 35.77 °C, solution pH of 7.59, CTC concentration of 57.72 mg/L and microbial inoculum of 0.98%. The antibacterial effect of CTC degradation products on Escherichia coli was investigated by the disk diffusion test, revealing that the products by LZ01 degradation of CTC exhibited lower toxicity than parent compound. Shake flask batch experiments showed that the biodegradation of CTC was a synergistic effect of intracellular and extracellular enzymes, and intracellular enzyme had a better degradation effect on CTC (77.56%). Whole genome sequencing revealed that genes associated with ring-opening hydrolysis, demethylation, deamination and dehydrogenation in strain LZ01 may be involved in the biodegradation of CTC. Subsequent seven possible biodegradation products were identified by LC-MS analyses, and the biodegradation pathways were proposed. Overall, this study provides a theoretical foundation for the characterization and mechanism of CTC degradation in the environment by Bacillus cereus LZ01. [Display omitted] • A Bacillus cereus strain capable of biodegrading CTC was isolated. • The degradation conditions of CTC by strain LZ01 were evaluated and optimized by RSM. • The product of LZ01 degradation of CTC exhibited low toxicity. • The products of CTC and possible degradation pathways were proposed. • Genomics revealed functional genes associated with CTC biodegradation. [ABSTRACT FROM AUTHOR]

Chlortetracycline (CTC) degradation mechanism in aqueous phase ozonation was evaluated for degradation mechanism and its correlation with the biodegradability and mineralization. CTC was removed within 8 and 4 min of ozonation at pH 2.2 and 7.0, respectively. At pH 2.2, HPLC–triple quadrupole mass spectrometry (MS) detected 30 products. The structures for some of these products were proposed on the basis of ozonation chemistry, CTC structure and MS data; these structures were then confirmed by nuclear magnetic resonance (NMR) spectra. Double bond cleavages, dimethyl amino group oxidation, opening and removal of the aromatic ring and dechlorination, mostly direct ozonation reactions, gave products with molecular weights (m.w.) 494, 510, 524, 495 and 413, respectively. Subsequent degradations gave products with m.w. 449, 465, 463 and 415. These products were arranged into a degradation pathway. At pH 7.0, the rate of reaction was increased, though the detected products were similar. Direct ozonation at pH 2.2 increased the biodegradability by altering the structures of CTC and its products. Nevertheless, direct ozonation alone remained insufficient for the mineralization, which was efficient at pH 7.0 due to the production of free radicals. [ABSTRACT FROM AUTHOR]

The thermal behavior of tetracycline hydrochloride (TC) and chlortetracycline hydrochloride (CTC) antibiotics was evaluated using thermoanalytical techniques TGA-DTA, DSC and evolved gas analysis by TGA-FTIR, providing information regarding thermal stability, decomposition steps and melting. TGA-FTIR revealed hydrochloric acid, water, isocyanic acid, dimethylamine, methane as main decomposition products for both antibiotics. Ammonia and carbon dioxide from the decomposition of the isocyanic acid have also been detected. According to DSC data the melting process occurred just before decomposition at 220.9 °C for TC. Tentative mechanisms for the thermal behavior of TC and CTC are presented. [ABSTRACT FROM AUTHOR]

This study was aimed at the degradation of chlortetracycline (CTC) in aqueous solution by direct and indirect photooxidation employing a solar simulator. Ruthenium complexes, tris -(2,2′-bipyridine) ruthenium(II) chloride (Ru3B), and tris -(1,10-phenanthroline) ruthenium(II) chloride (Ru3P) were used as photosensitizers to promote singlet oxygen ( 1 [O 2 ] ∗ ) formation in indirect photooxidation. The degradation kinetics of CTC followed a first-order kinetic, and the rate constant and the maximum percentage of degradation decreased by raising the concentration of CTC. This effect was attributed to that the amount of radiant energy absorbed by each CTC molecule decreased by raising the concentration of CTC. Addition of Ru3B produced a 6.98-fold increase in the degradation rate and 3-fold increment in the maximum percentage of degradation in comparison to direct photolysis. This is due to the formation of 1 [O 2 ] ∗ in the aqueous medium, as corroborated by the finding that a reduction in the level of dissolved oxygen produces a proportional decrease in the removal rate of CTC. High-resolution mass spectrometry studies demonstrated that degradation byproducts result from reduction–oxidation processes and the loss of functional groups, highlighting the hydrolysis and reduction of the primary amide, the formation of double bonds, and the addition of 1 [O 2 ] ∗ to the aromatic ring of CTC. The presence of humic acid in the solution favored direct photolysis but inhibited the action of photosensitizers. [ABSTRACT FROM AUTHOR]

Complexation of antibiotics with metals is a well-known phenomenon. Wastewater treatment plants contain metals and antibiotics, thus it is essential to know the effect of these complexes on toxicity towards microorganisms, typically present in secondary treatment processes. In this study, stability constants and toxicity of chlortetracycline (CTC) and metal (Ca, Mg, Cu and Cr) complexes were investigated. The calculated stability constants of CTC–metal complexes followed the order: Mg–CTC > Ca–CTC > Cu–CTC > Cr–CTC. Gram positive Bacillus thuringiensis (Bt) and Gram negative Enterobacter aerogenes (Ea) bacteria were used as model microorganisms to evaluate the toxicity of CTC and its metal complexes. CTC–metal complexes were more toxic than the CTC itself for Bt whereas for Ea, CTC and its metal complexes showed similar toxicity. In contrast, CTC spiked wastewater sludge (WWS) did not show any toxic effect compared to synthetic sewage. This study provides evidence that CTC and its metal complexes are toxic to bacteria when they are biologically available. As for WWS, CTC was adsorbed to solid part and was not biologically available to show measurable toxic effects. [ABSTRACT FROM AUTHOR]