Antibiotics In Water Research Articles

Degradation of Antibiotics via UV-Activated Peroxodisulfate or Peroxymonosulfate: A Review

The ultraviolet (UV)/H2O2, UV/O3, UV/peroxodisulfate (PDS) and UV/peroxymonosulfate (PMS) methods are called UV-based advanced oxidation processes. In the UV/H2O2 and UV/O3 processes, the free radicals generated are hydroxyl radicals (•OH), while in the UV/PDS and UV/PMS processes, sulfate radicals (SO4•−) predominate, accompanied by •OH. SO4•− are considered to be more advantageous than •OH in degrading organic substances, so the researches on activation of PDS and PMS have become a hot spot in recent years. Especially the utilization of UV-activated PDS and PMS in removing antibiotics in water has received much attention. Some influencing factors and mechanisms are constantly investigated and discussed in the UV/PDS and UV/PMS systems toward antibiotics degradation. However, a systematic review about UV/PDS and UV/PMS in eliminating antibiotics is lacking up to now. Therefore, this review is intended to present the properties of UV sources, antibiotics, and PDS (PMS), to discuss the application of UV/PDS (PMS) in degrading antibiotics from the aspects of effect, influencing factors and mechanism, and to analyze and propose future research directions.

Distribution Coefficient of QNs in Urban Typical Water and Its Main Environmental Influencing Factors

Sediment is the main storage medium of antibiotics in a water environment, and a growing body of research has focused on the distribution behavior of antibiotics in water-sediment. However, most of the previous studies were based on laboratory simulation, and less attention was paid to the distribution behavior of antibiotics in a natural water environment and its correlation with environmental factors. Thus, the surface water and sediment in Shijiazhuang were taken as the research object for this study. The temporal and spatial distribution characteristics of quinolone (QNs) antibiotics in Shijiazhuang water were analyzed by using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS), calculating the distribution coefficients of quinolone (QNs) antibiotics in water and sediment, and confirming the main environmental factors influencing the distribution coefficient in natural water. The results showed that:① the content of ΣQNs in water and sediment ranged from 8.0 to 4.4×103 ng·L-1 and 16 to 2.2×103 ng·g-1 in Shijiazhuang water, whereas the primary QNs in water and sediment were enrofloxacin (ENR) and ofloxacin (OFL), respectively. ② The total concentrations of ΣQNs in Shijiazhuang water showed a tendency of being higher in December (1.0×104 ng·L-1) than in April (5.5×103 ng·L-1), and QNs in sediment were also higher in December (7.8×103 ng·g-1) than in April (6.2×103 ng·g-1). ③ The distribution coefficient of QNs in Shijiazhuang water varied from 34 to 2.9×105 L·kg-1 and showed a trend of being greater in December than in April. ④ The results of correlation analysis showed that total nitrogen (TN), nitrate nitrogen (NO3--N), nitrite nitrogen (NO2--N), and ammonia nitrogen (NH4+-N) were significantly correlated with most distribution coefficients of QNs[OFL, norfloxacin (NOR), ENR, difloxacin (DIF), and oxolinic acid (OXO)], whereas temperature (T), total organic carbon (TOC), and total dissolved solids (TDS) were significantly correlated with individual distribution coefficients of QNs[marbofloxacin (MAR) and DIF]. Therefore, the eutrophication level of water affects the distribution behavior of antibiotics in water-sediment.

Plasmonic Bi promotes the construction of Z-scheme heterojunction for efficient oxygen molecule activation.

Reactive oxygen species (ROS) are essential to photocatalytic degradation of antibiotics in water. In this work, we prepared Ag3PO4/Bi@Bi4Ti3O12 by simple in-situ reduction method and precipitation method, which improves the ability to capture visible light and increases the activity of photoinduced molecular oxygen activation, resulting in reactive oxygen species (ROS) such as superoxide radicals (•O2-), hydroxyl radicals (•OH), and H2O2. The excellent TC degradation efficiency derive from the SPR effect of the metal Bi on the surface enhances the light absorption intensity, and development of a Z-scheme heterojunction between Ag3PO4 and Bi4Ti3O12 promotes the activation of molecular oxygen. A possible photodegradation mechanism of the as-prepared photocatalyst was proposed. This work provides an insight perspective to the synthesis photocatalysts with molecular oxygen activation for environmental remediation.

Study on the synthesis and characterization of CoTiO3 catalysts and their catalytic properties in Oxone activation for the degradation of tetracycline antibiotic in water

The chemical degradation of sulfate by activated Oxyone has the advantages of high degradation capacity, wide pH range and convenient transportation and storage, making it one of the most attractive advanced oxidation processes (AOPs). Besides, Co is the metal most capable of activating Oxone to produce sulfate. Therefore, it is critical to develop Co-based catalyst, an effective and recyclable heterogeneous catalyst, for activating Oxone to degrade tetracycline. In this study, CoTiO3 was extensively investigated for the activation of Oxone to generate sulfate radicals and degrade tetracycline antibiotics. The results showed that more than 95% of tetracyclines could be degraded at the amount of CoTiO3 catalyst of 0.02 g, the Oxone reagent concentration of 0.4 mmol l−1, and the pH value of 7. The removal rate of tetracyclines could still reach more than 85% after the CoTiO3 composite was repeatedly used for four consecutive cycles. These results indicate that CoTiO3/Oxone can be explored as an effective system for degrading long-lived organic pollutants.

Improved photodegradation of antibiotics pollutants in wastewaters by advanced oxidation process based on Ni-doped TiO2.

The number of antibiotic compounds in wastewaters has been growing globally due to the covid-19 problem. Using antibiotics to treat the patients would produce larger amounts of these compounds into the environment with negative impacts. Hence, finding out the method for the elimination of toxic organic pollutants as well as antibiotics in water is urgent (In this study, the treatment of antibiotic pollutants including cefalexin (CF) and tetracycline (TC) was investigated by applying the advanced oxidation process based on Ni-doped TiO2 (Ni-TiO2). The characterizations technologies such as XRD, XPS, UV-vis, PL, and PC indicated that Ni doping would improve the photocatalytic performance of TiO2. In the photodegradation experiments, the Ni-TiO2 possessed high photocatalytic degradation efficiencies with 93.6% for CF and 82.5% for TC. Besides, the removal rates of antibiotics after five cycles are higher than 75%, implying excellent stability of Ni-TiO2 photocatalyst. The result from the treatment of wastewater samples revealed that the Ni-TiO2 photocatalytic had good performance for removal of CF and TC at a high level of 88.6 and 80.2%, respectively.

Removal of ciprofloxacin antibiotic pollutants from wastewater using nano-composite adsorptive membranes

The emergence of antibiotics in water has been globally recognized as a critical pollution issue. Antibiotics (such as Ciprofloxacin (CPFX) pose a serious threat to humans and to the ecosystem due to its accumulation in water sources which can lead to chronic health problems and endanger aquatic life. It is therefore crucial to properly remove them from water. In this work, a nano-composite adsorptive membrane based on Zirconium Phosphate (ZrP) adsorbent supported on Polyethersulfone (PES) was synthesized and evaluated for the removal of CPFX from synthetic aqueous solutions. The membranes described here showed a very high antibiotic removal rate. The effect of various parameters such as the initial concentration of the antibiotic, the adsorbent dosage, contact time, pH, and temperature was studied. The equilibrium data were found to reasonably best fit with the Temkin isotherm model. The membranes showed a high ciprofloxacin removal (99.7%) as opposed to (68%) when PES membrane alone was used. Moreover, a significant improvement in the membrane's water flux (100.84 L/m2.h) and permeability (97.62 L/m2.hr.bar) were noticed as opposed to pure PES membrane's flux and permeability. The adsorptive membranes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET). The results confirmed the successful formation of ZrP nanoparticles adsorbent within the membrane matrix, and with enhanced hydrophilic properties. The membrane was successfully regenerated and reused up to 5 times. The results of this work showed the potential of such membranes for the removal of ciprofloxacin and at a high efficiency.

Study of microplastics as sorbents for rapid detection of multiple antibiotics in water based on SERS technology

Online monitoring of antibiotics in the environment attracts more and more attention. Surface-enhanced Raman scattering (SERS) is a promising technique for the detection of trace amounts of antibiotics in the environment, which is fast, non-invasive and sensitive. To investigate the enrichment of trace amounts of antibiotics in water, polyethylene microplastics (PE MPs) were prepared as sorbents to simply concentrate enrofloxacin, ciprofloxacin hydrochloride monohydrate and triclosan in water, followed by the SERS measurement of antibiotics extract washed from MPs on an AgNPs@Si SERS substrate. Limit of detection of Rhodamine 6G is 2.1 × 10-12 M achieved from the AgNPs@Si SERS, indicating a high enhancement. The detection results show that SERS peaks of the antibiotics could be observed from the spectra of the extracts eluted from MPs, indicating MPs could adsorb and desorb antibiotics from water. Besides, for enrofloxacin and triclosan, the intensity of SERS measured from the MPs extracts are higher than that of directly from the spiked water, demonstrating the proposed method could lower the detectable concentration of hydrophobic antibiotics in water. Moreover, the proposed MPs sorbents combined with SERS method was applied to detect the antibiotics in real river water, with minimal detection of 10-10 M, 10-8 M, and 10-8 M achieved for enrofloxacin, ciprofloxacin hydrochloride monohydrate and triclosan, respectively. The proposed method provides a promising simple, rapid and low reagent consuming means for monitoring antibiotics in water.

Dye-encapsulated Zr-based MOFs composites as a sensitive platform for ratiometric luminescent sensing of antibiotics in water

Overuse of antibiotics posed a global threat to human health and the ecological environment. Efficient detection and control of antibiotic pollution demand novel sensory materials. Here, a dual-luminescent material FS@UIO66 was successfully synthesized by encapsulating fluorescent molecules (fluorescein sodium, FS) in UIO66 based on the in-situ encapsulation method. We found that the dual emission peaks of FS@UIO66 at 369 and 515 nm can be sensitively and synchronously quenched by tetracycline (TET). Interestingly, these two peak intensities were switched anisotropically by levofloxacin (LEV), in which the signal at 515 nm was enhanced. Photophysical analysis revealed that there may exist a competition and replenishment mechanism in the sensing processes. The ratiometric fluorescent feature was employed for rapid detection of TET and LEV, with detection limits of 0.2444 μM and 0.2808 μM for TET and LEV, respectively. The superior sensitivity, high selectivity, and excellent recyclability of FS@UIO66 in sensing TET and LEV were demonstrated in this work. In addition, TET and LEV were also successfully detected by FS@UIO66 in water from real water environment. The results indicate that FS@UIO66 composites are favorable for TET and LEV detection, presenting a great sensing platform for antibiotic detection.

Z-scheme Au@TiO2/Bi2WO6 heterojunction as efficient visible-light photocatalyst for degradation of antibiotics

Semiconductor photocatalysis can be regarded as one of effective strategies to overcome the great challenges encountered with conventional technologies for environmental remediation. In this research, Z-scheme heterostructure composed of core–shell Au@TiO2 nanoparticles and flower-like Bi2WO6 nanosheets has been successfully prepared through the reverse micelle sol–gel method followed by a hydrothermal process. The structural characteristics, chemical compositions and photoelectrochemical properties of this ternary composite photocatalyst (Au@TiO2/Bi2WO6) were further investigated in detail. Benefitted from the synergy of the heterojunction construction and metallic surface plasmon resonance effect, the Au@TiO2/Bi2WO6 with an optimal mass ratio of Au@TiO2 to Bi2WO6 exhibited the significantly enhanced photocatalytic activity for degradation of antibiotics under visible-light irradiation, in which the degradation efficiency of sulfamethoxazole (SMX) and tetracycline hydrochloride (TC) could be up to 96.9% and 95.0% within 75 min, respectively. The reaction rate constant for SMX and TC degradation was calculated to be around 0.0425 min−1 and 0.0314 min−1, which has 7.2 times and 1.9 times enhancement compared with single Bi2WO6, respectively. In addition, the cyclic stability and photocatalytic mechanism of Au@TiO2/Bi2WO6 were further verified. Our primary results provide a feasible strategy to develop core–shell heterostructured photocatalysts with superior performance for the efficient removal of low-concentration antibiotics in water.

Complementarity of two approaches based on the use of high-resolution mass spectrometry for the determination of multi-class antibiotics in water. Photodegradation studies and non-target screenings

The development of analytical methodologies to monitor different antibiotic families in water and the implementation of alternatives for their efficient elimination are a great challenge. The aim of this research was to develop a method based on solid-phase extraction followed by ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry to analyse multi-class antibiotics, including macrolides, cephalosporins, fluoroquinolones, sulfonamides and diaminopyrimidines, in waters. Several parameters affecting the extraction such as the sample pH, type of sorbent and cartridge, elution volume and breakthrough volume were optimized. The method was validated in real samples, and matrix effect was assessed, demonstrating that the use of isotopically labelled surrogate compounds was mandatory to avoid standard addition calibration for each individual samples. Urban and hospital wastewater samples, as well as natural waters, were analysed, confirming the presence of 12 of the 14 target compounds at concentrations up to 3.5 µg L−1. Non-target analysis based on data-independent workflow was also performed, enabling the identification of 94 pollutants. Preliminary photodegradation experiments were also assessed, revealing the total removal of many target compounds after the first 5–10 min of UVC irradiation. In addition, 20 by-products formed after photolysis could be identified using a non-target approach.

Natural Materials Modified and Applied to the Detection of Drugs In Situ: Modification of Eggshell and Quantification of Oxytetracycline.

This work describes a novel sensing system using eggshells as substrate for the first time, targeting the detection and semiquantitative determination of antibiotics in waters from aquaculture, enabling simple, inexpensive, and in situ drug monitoring. Eggshell was ground and the resulting powder was modified by adsorption of suitable reagents, and it takes a typical colour after contact with the antibiotic. The colour intensity is correlated with the concentration of the antibiotic. This novel approach was applied to oxytetracycline, one of the antibiotics commonly used in aquaculture. The chemical changes on the eggshell powder were evaluated and optimised to produce an intense colour change as a function of the concentration of the antibiotic. The colour changes were evaluated by visual comparison with images taken with a digital camera, applying an appropriate mathematical treatment to the colour coordinates of the HSL system used by Windows. The selectivity of the response was tested against other antibiotic drugs. The materials were also used in the analysis of a spiked environmental water sample. Overall, this work presents a rapid, inexpensive, simple and equipment-free method for screening and discrimination of tetracycline drugs in aquaculture. The method is a green approach by reusing eggshells and decreasing the level of contamination correlated to analytical methods, thus being a promising tool for local, rapid, and cost-effective antibiotic monitoring.

Preparation of a 3D flower-like spherical structure g-C3N4/CuBi2O4/Bi2MoO6 photocatalyst for efficient removal of antibiotics under visible light

For the remediation of antibiotic-contaminated water bodies, this study synthesized g-C3N4/CuBi2O4/Bi2MoO6 3D flower-like spherical photocatalysts by a solvothermal method. The tetracycline antibiotics were used as the target pollutants and degraded under visible light to evaluate the photocatalytic performance of the prepared photocatalysts. Notably, the g-C3N4/CuBi2O4/Bi2MoO6 photocatalyst achieved 84.6 % and 91.6 % for the degradation of tetracycline hydrochloride and chlortetracycline (100 mL, 20 mg/L), respectively, within 2 h under visible light irradiation. Furthermore, we found that the composites showed very low degradation rates for dye-based contaminants, but still exhibited excellent photocatalytic activity for antibiotics in a mixed contaminant system of dyes and antibiotics. And the intermediate was detected by gas chromatography-mass spectrometry (GC–MS), suggesting a possible photo-degradation pathway for tetracycline. Finally, biochemical experiments were carried out to further illustrate the effective degradation of antibiotics in water after photocatalytic degradation by observing and comparing the growth of mung bean seeds.

Antibiotics in the Basque coast (N Spain): Occurrence in waste and receiving waters, and risk assessment (2017–2020)

The study of the presence of antibiotics in the aquatic environment is a preliminary step to analyse their possible harmful effects on aquatic ecosystems. In order to monitor their occurrence in the aquatic environment, the European Commission established in 2015, 2018, and 2020 three Watch Lists of substances for Union-wide monitoring (Decisions (EU) 2015/495, 2018/840, and 2020/1161), where some antibiotics within the classes of macrolides, fluoroquinolones and penicillins were included.In the Basque coast, northern Spain, three macrolide antibiotics (erythromycin, clarithromycin, azithromycin) and ciprofloxacin were monitored quarterly from 2017 to 2020 (covering a period before and after the COVID19 outbreak), in water samples collected from two Waste Water Treatment Plants (WWTPs), and three control points associated with receiving waters (transitional and coastal water bodies). This work was undertaken for the Basque Water Agency (URA).The three macrolide antibiotics in water showed a frequency of quantification >65 % in the Basque coast, with higher concentrations in the WWTP emission stations than in receiving waters. Their frequency of quantification decreased from 2017 to 2020, as did the consumption of antibiotics in Spanish primary care since 2015. Ciprofloxacin showed higher frequencies of quantification in receiving waters than in wastewaters, but the highest concentrations were observed in the WWTP emission stations. Although consumption of fluoroquinolones (among which is ciprofloxacin) in primary care in the Basque Country has decreased in recent years, this trend was not observed in the waters sampled in the present study. On the other hand, concentrations of clarithromycin, azithromycin, and ciprofloxacin in receiving waters exceeded their respective Predicted No-Effect Concentrations, so they could pose an environmental risk. These substances are widely used in human and animal medicine, so, although only ciprofloxacin is included in the third Watch List, it would be advisable to continue monitoring macrolides in the Basque coast as well.

Removal of Trace Plant Antibiotics from Water Systems by Adsorption: A Review

AbstractPlant antibiotics in water are considered an emerging issue due to their interference with human health. Antibiotics protect crops from diseases; however, low levels of antibiotics are found in wastewater due to their incomplete removal. Several treatment methods are available, but with limitations such as high operation and maintenance costs and the formation of toxic by‐products. Antibiotic removal by adsorption is an alternative method, being a low‐energy process with simple operation, mainly if used with carbonaceous adsorbents. Antibiotic removal was fit to a wide variety of isotherm and kinetic models, with the Freundlich isotherm as the most employed one. This paper aims to review the use of the adsorption process in the removal of plant antibiotics from water systems.

Fabrication of Zn-MOF derived graphitic carbon materials with mesoporous structure for adsorptive removal of ceftazidime from aqueous solutions

Antibiotic-resistant genes (ARGs) and antibiotics were detected in various environmental media. Metal-organic framework materials (MOFs) have great advantages in removing many pollutants in water. However, their microporous structure and poor hydrothermally stability make them difficult to realize efficient adsorption performance of macromolecular pollutants. Therefore, this study is devoted to preparing MOF-derived mesoporous carbon materials with excellent pore structure and stability so as to improve the adsorption performance of macromolecular antibiotics in water. In this study, the surface morphological structure of the MOF material was regulated from the preparation process. Firstly, the template agent formed micelles in the MOF framework, so that self-assembly and crystal growth were carried out under the guidance of cooperative templates. Secondly, the morphological structure of the material surface was modified by high-temperature calcination and surface etching. A series of graphitic carbon material MC-X with tunable mesoporous structure were prepared using Zn-MOF materials as precursors and N-Cetyldimethylamine as template. The pore size and mesoporous ratio of the MC-0.3 material had undergone large changes, the pore size varied from 1.73 nm to 3.94 nm, and the mesoporous ratio transformed from 12.6% to 97.71%. Unexpectedly, the material converted from hydrophilic to hydrophobic, and possessed an ultra-high ceftazidime (CAZ) adsorption capacity of 371.18 mg·g−1. The adsorption mechanisms of CAZ on MC-0.3 were mainly molecular size matching selection, hydrophobic effect and hydrogen bonding. After 5 adsorption-desorption cycles, MC-0.3 could maintain about 90% of the initial adsorption capacity.

Enhanced degradation of carbamazepine in water over SC-modified NiFe2S4 nanocomposites by peroxymonosulfate activation

In this study, novel Semi-coke-modified NiFe2S4 nanocomposites with different mass ratios are successfully prepared by hydrothermal method to activate peroxymonosulfate (PMS) for the degradation of carbamazepine (CBZ) in water. The factors affecting the degradation of CBZ, such as initial solution pH, PMS and catalyst dosage, inorganic anions, and humic acid (HA) are investigated. The possible PMS activation mechanism and CBZ possible degradation pathways are also explored. The results show that the performance of SCNF-0.5/PMS (mass ratio of SC:NiFe2S4 = 1:2) is better than that of monomeric NiFe2S4 and semi-coke (SC). X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) spectrometer, and free radical quenching experiments show that both non-radical (1O2 and Ov) and free radical pathways (SO4− and OH) may be responsible for the degradation of CBZ, but 1O2 is dominant active species. S2− promotes the Ni2+/Ni3+, Fe2+/Fe3+ cycle to ensure the stable performance of the catalyst, and the oxygen vacancies (Ov) in the SC act synergistically with the catalyst to promote the degradation of CBZ. This study may provide new insights into the degradation of antibiotics in water by modifying stable bimetallic sulfide to activate PMS.

Occurrence, Comparison and Priority Identification of Antibiotics in Surface Water and Sediment in Urbanized River: A Case Study of Suzhou Creek in Shanghai

Antibiotics in water have attracted increasing attention due to their potential threat to aquatic ecosystems and public health. Most previous studies have focused on heavily polluted environments, while ignoring urbanized rivers with high population density. Taking Suzhou Creek in Shanghai as an example, this study attempted to explore the antibiotic pollution characteristics of typical urbanized rivers. Further, it screened out priority antibiotics so as to provide reference for the regular monitoring of antibiotics in urban surface water in the study’s later stage. Four classes of 27 antibiotics in surface water samples and sediment samples were detected and analyzed by SPE-UPLC-MS/MS under both wet season and dry season. Results demonstrate that the total amount of antibiotics detected reached 1936.9 ng/L and 337.3 ng/g in water samples and sediment samples, respectively. Through Pearson correlation analysis, it can be shown that there is a very significant correlation between a variety of antibiotics in water and sediment. The results of ecological risk assessment based on risk quotient (RQ) show that certain antibiotics presented high and medium risk to the surrounding ecosystem. Finally, the priority antibiotics selected by optimized priority screening method were EM, SPD, CLR and RTM. Therefore, we have proven that the antibiotics being discharged in urbanized rivers show different types of antibiotics, while presenting a toxicological risk to certain species.

Preparation and characterization of novel Niln2S4/UiO-66 photocatalysts for the efficient degradation of antibiotics in water

Photocatalysis is considered an economical, environmentally friendly, and effective technology for removing pollutants. The construction of Z-Scheme heterojunctions has been identified as one of the feasible solutions capable of enhancing the photocatalytic activity. Herein, a series of visible light responsive photocatalysts (NiIn2S4/UiO-66 composites) with excellent activity and stability were prepared by using a solvothermal process. It is found that 20 mg L−1 of tetracycline (TC) could be almost completely degraded under visible light irradiation within 1 h, when the mass ratio of NiIn2S4 to UiO-66 is 0.5:1 (NISU-0.5) and the solution pH = 11. In addition, after six cycles, the degradation rate of tetracycline photocatalyzed by NISU-0.5 still reach up to 90%. Ultraviolet photoelectron spectra (UPS), X-ray photoelectron spectra (XPS) and electron spin resonance measurements (ESR) confirm the formation of the Z-Scheme heterostructure between NiIn2S4 and UiO-66. The synergistic effect between built-in electric field, energy band bending and coulomb interactions in interface of Z-Scheme heterojunction is conducive to restrain the recombination of photogenerated electrons and holes, which greatly improve the photocatalytic activity. In conclusion, this study offers a new thought for design and synthesis of Z-Scheme heterojunctions and provides a cost-effective strategy for solving environmental pollution and energy problems in the future.

Rapid and ultra-trace levels analysis of 33 antibiotics in water by on-line solid-phase extraction with ultra-performance liquid chromatography-tandem mass spectrometry

A method was developed for the determination of 33 antibiotics belonging to 4 different antibiotic groups, including sulfonamides (16), fluoroquinolones (12), macrolides (1), and tetracyclines (4) in water samples using on-line solid-phase extraction-ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (on-line SPE-UPLC-MS/MS). The enrichment and analysis conditions were optimized for the determination of trace concentrations (nanogram per liter). Aliquots of the water samples (5 mL) were filtered through a membrane and enriched on an on-line polymeric column with hydrophilic–lipophilic balance (HLB). The analyte was eluted by the mobile phase during on-line SPE and separated on an Acquity BEH130 column, detected by tandem mass spectrometry, and quantified using an external standard method. The optimization of the analytical methods was discussed, which included optimization of pH of the sample, filtration membrane, Na2EDTA, chromatographic column, formic acid and aqueous ammonia in mobile phase. The detection limit for all test compounds by this method was in the range of 0.2–1.5 ng/L, with recoveries of 76.6–118%. The precision of the method, as indicated by the relative standard deviation, was 2.4–7.9%. Results of analysis of surface water samples demonstrated the ability of the proposed method to analyze ultra-trace levels of antibiotics, without the need for complex manual pretreatment.

Facile synthesis of NiAl2O4/g-C3N4 composite for efficient photocatalytic degradation of tetracycline

Designing high-efficiency photocatalysts responsive to visible light is important for the degradation of antibiotics in water. Heterojunction engineering is undoubtedly an effective strategy to improve the photocatalytic performance. In this work, spinel-type metal oxides (NiAl2O4, NAO) are synthesized by a simple sol-gel and calcination process. After compounding graphitic carbon nitride (g-C3N4), NAO/g-C3N4 heterojunction is obtained, which then is used as the photocatalyst for tetracycline hydrochloride (TC). The effects of photocatalyst dosage, the initial concentration of TC, and solution pH on photodegradation performance are systematically studied. The removal rate of TC on NAO/g-C3N4 reach up to ∼90% after visible light irradiation for 2 hr and the degradation rate constant is ∼7 times, and ∼32 times higher than that of pure NAO and g-C3N4. The significantly improved photocatalytic activity can be attributed to the synergistic effect between well matched energy levels in NAO/g-C3N4 heterojunctions, improvement of interfacial charge transfer, and enhancement of visible light absorption. This study provides a way for the synthesis of efficient photocatalysts and an economic strategy for removing antibiotics contamination in water.