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Electrochemical oxidation of fluoroquinolone antibiotics: Mechanism, residual antibacterial activity and toxicity change
Abstract
In this paper, we studied the electrochemical oxidation mechanisms of three typical fluoroquinolone antibiotics (FQs), and investigated residual antibacterial activity and toxicity changes after oxidation processes. Electrochemistry coupled to mass spectrometry (EC-MS) was used to study the oxidation processes of ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL). Eight oxidation products for each parent compound were identified and their chemical structures were elucidated. The transformation trend of each product, with the continuous increase of voltage from 0 to 3000 mV, was recorded by online EC-MS. The oxidation pathways were proposed based on the structural information and transformation trends of oxidation products. We found the oxidation mechanisms of FQs consisted of the hydroxylation and cleavage of piperazinyl ring via reactions hydroxyl radicals, while the fluoroquinolone core remained intact. The antibacterial activity of the parent compounds and their oxidation mixtures was estimated using zone inhibition tests for gram-negative bacteria Salmonella typhimurium. It was found that the oxidation mixtures of CIP and NOR retained the antibacterial properties with lower activity compared to their parent compounds, while the antibacterial activity of OFL was almost eliminated after oxidation. Furthermore, the toxicity of the three FQs and their oxidation mixtures were evaluated by using algal growth inhibition test (Desmodesmus subspicatus). The median effective concentration (EC50) values for the algal inhibition tests were calculated for the end point of growth rate. The toxicity of CIP and NOR to green algae after electrochemical oxidation, remained unchanged, while that of OFL significantly increased. The results presented in this paper contribute to an understanding of the electrochemical oxidation mechanisms of FQs, and highlight the potential environmental risks of FQs after electrochemical oxidation processes.
... The antibiotics and dyes used in these sectors are extremely poisonous, thus their wastewater effluents pose a serious hazard to the environment when they are dumped without being properly treated [1][2][3]. Among the most significant fluoroquinolone antibiotics, norfloxacin (NOR) is employed in both human and animal medicine due to its broad spectrum of activity [4]. Humans and animals alike have poor adsorption capacities for NOR, and the majority of NOR (60-70%) is expelled into the environment via urination and faeces [5]. ...
... About 100 mL of a 0. 4 ...
The treatment of wastewater through the use of photocatalytic materials over semiconducting metal oxide has gained widespread interest as a promising new green and cheap technology. For the first time norfloxacin (NOR) antibiotic and methylene blue (MB) dye degradation was achieved by a simpler, cheaper, and faster technique for the preparation of NiO/ZnO heterostructure via NiO and its combined forms with ZnO catalysts under hydrothermal process. X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and X-ray photoelectron (XPS) spectroscopy were the techniques that were used to analyze the structure, morphology, and elemental contents, respectively. The Tauc plot using absorption spectra was used to determine the band energy value of pure NiO, ZnO, and NiO–ZnO catalysts. The results showed that the energy band gap of these materials was 3.15, 3.38, and 2.93 eV, respectively. All photocatalysts performed good efficiency within 50 min of irradiation, among these NiO/ZnO having superior activity (30 mg of catalyst, and 10 µM of dye and antibiotic). Under these conditions, the photocatalytic degradation efficiency of the produced NiO/ZnO materials for the NOR and MB dye was achieved at 96.73% and 97.38%, respectively. Inhibition of the recombination of electron-hole pairs by charge transfer processes may account for the high activity of the p-n-type NiO/ZnO heterostructures for the degradation of NOR and MB. Because of their strong photocatalytic activity, heterostructures based on semiconducting composites, such as NiO/ZnO, have great promise for use in future manufacturing processes aimed at cleaning our surroundings of harmful organic pollutants.
... The relative abundance of another kind of algae, Desmodesmus, increased slightly with adding 1 mg/L antibiotic but decreased at a higher antibiotic concentration. The growth of Desmodesmus was promoted by low concentrations of antibiotics but could not resist the stress of high concentrations of antibiotics, as the median effective concentration of OFLX to Desmodesmus was approximately 6.8 mg/L (Zhu et al., 2016). ...
... The relative abundance of Desmodesmus increased by about 0.8 % in MBS-SW-OTC and MBS-SW-OFLX than MBS, which was higher than that in MBS-OTC1 and MBS-OFLX1 as well. It indicated that Desmodesmus could adapt to the wastewater with low concentrations of antibiotics (Zhu et al., 2016). The bacterial genera in SW were mainly Pseudomonas (11.3 %) and Proteiniphilum (8.2 %), and the unculturable genera accounted for 32.7 % (Fig. 5b). ...
The development of microalgae-bacteria symbiosis for treating wastewater is flourishing owing to its high biomass productivity and exceptional ability to purify contaminants. A nature-selected microalgae-bacteria symbiosis, mainly consisting of Dictyosphaerium and Pseudomonas, was used to treat oxytetracycline (OTC), ofloxacin (OFLX), and antibiotic-containing swine wastewater. Increased antibiotic concentration gradually reduced biomass productivity and intricately changed symbiosis composition, while 1 mg/L OTC accelerated the growth of symbiosis. The symbiosis biomass productivity reached 3.4-3.5 g/L (5.7-15.3% protein, 18.4-39.3% carbohydrate, and 2.1-3.9% chlorophyll) when cultured in antibiotic-containing swine wastewater. The symbiosis displayed an excellent capacity to remove 76.3-83.4% chemical oxygen demand, 53.5-62.4% total ammonia nitrogen, 97.5-100.0% total phosphorus, 96.3-100.0% OTC, and 32.8-60.1% OFLX in swine wastewater. The microbial community analysis revealed that the existence of OTC/OFLX increased the richness and evenness of microalgae but reduced bacteria species in microalgae-bacteria, and the toxicity of OFLX to bacteria was stronger than that of OTC.
... Various processes including membrane separation [6], biodegradation [14], adsorption [15,16], and advanced oxidation [17,18] have thus been developed to remove antibiotics from water. In the last few years, electrocoagulation process has attracted increase amount of attention due to its effectiveness in removing a wide range of pollutants in water and wastewater with low sludge production and low treatment cost [19,20]. ...
... It was reported that the oxidation mechanism of OFL, using a boron-doped diamond working electrode (applied potential 1500 mV), consists of the hydroxylation and cleavage of piperazinyl ring via reactions with hydroxyl radicals, while the fluoroquinolone core remained intact. Several oxidation products where then identified [18]. Similar findings on the degradation mechanism were also reported by Patidar and Strivastava [29] on titanium coated ruthenium oxide Ti/RuO 2 anode for an applied current density of 21.3 mA⋅cm − 2 . ...
Antibiotics are emerging micropollutants, which can be harmful and toxic for the human health and biotic community. Nowadays, it is recognized that the conventional wastewater treatment is relatively ineffective for their removal. Effluents are then among the main sources of antibiotics' releasing into environment. As a promising treatment process, electrocoagulation (EC) has proven efficacy for the treatment of many refractory pharmaceuticals but remains little studied for antibiotics. In this study, EC was applied for the first time to remove ofloxacin (OFL) and chloramphenicol (CAP), widely dispersed antibiotics in the environment worldwide. Results revealed that EC with Al-electrodes is effective for OFL and CAP removal in aqueous solution. 72 % of OFL is removed for 40 min electrolysis time, and a maximum of 78 % is reached after 105 min. CAP needs more time to reach 78 % (180 min) but its removal continues over time. Based on UV–visible, HPLC and FTIR analyses, it was shown that OFL is mainly removed by adsorption on the electro-generated Al(OH)3 flocs whereas cathodic degradation is responsible for CAP reduction. OFL adsorption is mainly controlled by surface complexation mechanism involving the surface functional group AlOH and the deprotonated carboxylate groups in the anionic (OFL⁻) and zwitterion (OFL⁰) ofloxacin. The cathodic degradation of CAP generates four main by-products: the nitroso product (NOCl2), an aromatic amine product (AMCl2) and two dechlorinated AMCl2 products (AMCl and AM). The toxicity assays showed that EC process could eliminate the antibacterial activity of OFL and CAP.
... H 2 O 2 can be produced continuously in the electro-Fenton reaction, and Fe 2+ can be continuously regenerated in situ by electrolysis . The reaction principle is described below (Hassan et al., 2020;Olvera-Vargas et al., 2021;Oturan et al., 2014;Zhang et al., 2019;Zhou et al., 2018): in the electro-Fenton reaction system with a sacrificial anode, the sacrificial iron anode provides Fe 2+ for the reaction under the condition of energization by the addition of H 2 O 2 . In addition, the Fe 3+ generated during the reaction is reduced to form Fe 2+ at the cathode, and Fe 2+ and H 2 O 2 undergo the Fenton reaction in the system. ...
... Second, the toxicity of ofloxacin and norfloxacin to green algae remained unchanged, while the toxicity of ofloxacin increased significantly. Therefore, electrochemical oxidation of ofloxacin has some environmental risks (Zhu et al., 2016). Dirany et al. used BDD as the anode and stainless steel (SS) as the cathode for the electrocatalytic oxidation of SMX. ...
The frequent use of antibiotics allows them to enter aqueous environments via wastewater, and many types of antibiotics accumulate in the environment due to difficult degradation, causing a threat to environmental health. It is crucial to adopt effective technical means to remove antibiotics in aqueous environments. The Fenton reaction, as an effective organic pollution treatment technology, is particularly suitable for the treatment of antibiotics, and at present, it is one of the most promising advanced oxidation technologies. Specifically, rapid Fenton oxidation, which features high removal efficiency, thorough reactions, negligible secondary pollution, etc., has led to many studies on using the Fenton reaction to degrade antibiotics. This paper summarizes recent progress on the removal of antibiotics in aqueous environments by Fenton and Fenton-like reactions. First, the applications of various Fenton and Fenton-like oxidation technologies to the removal of antibiotics are summarized; then, the advantages and disadvantages of these technologies are further summarized. Compared with Fenton oxidation, Fenton-like oxidations exhibit milder reaction conditions, wider application ranges, great reduction in economic costs, and great improved cycle times, in addition to simple and easy recycling of the catalyst. Finally, based on the above analysis, we discuss the potential for the removal of antibiotics under different application scenarios. This review will enable the selection of a suitable Fenton system to treat antibiotics according to practical conditions and will also aid the development of more advanced Fenton technologies for removing antibiotics and other organic pollutants.
... Many applications have been used to treat effluents rich in FQs, such as electrochemical oxidation [8], biodegradation [9], photodegradation [10], catalytic degradation [11], microextraction [12], oxidation (catalytic degradation) [13] and adsorption [14]. Among current methods, adsorption has proven to be a simple, high-performance and low-cost approach for removing low concentration FQ contaminants from aqueous media [15]. ...
... Adsorption studies carried out at various pH values revealed that the highest adsorption rate occurs at pH 8.0 point ( Figure 6). Since the adsorbent's isoelectric point is pH 9.41, it is positively charged for all pH values (pH [3][4][5][6][7][8][9] used in this investigation. The adsorption capacity between these points varies between 53-60 mg/g, indicating that the adsorption mechanism is predominantly non-ionic. ...
Antibiotics are among the most critical environmental pollutant drug groups. Adsorption is one of the methods used to eliminate these pollutants. In this study, activated carbon was produced from pumpkin seed shells and subsequently modified with KOH. The adsorbent obtained through this procedure was used to remove ciprofloxacin from aqueous systems. Fourier Trans-form-Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), elemental, X-ray Pho-toelectron Spectroscopy (XPS), Brunauer–Emmett–Teller (BET) and Zeta analyses were used to characterize the adsorbent. The surface area, in particular, was found to be a very remarkable value of 2730 m2/g. The conditions of the adsorption experiments were optimized based on inter-action time, adsorbent amount, pH and temperature. Over 99% success was achieved in removal operations carried out under the most optimal conditions, with an absorption capacity of 884.9 mg·g−1. In addition, the Langmuir isotherm was determined to be the most suitable model for the adsorption interaction.
Keywords: activated carbon; adsorption; ciprofloxacin; pollutant; pumpkin seed; thermodynam-ics
... In pathway III, the atoms of 32C and 35C on the piperazinyl ring are attacked by •OH to form P3 (m/z = 348) and P4 (m/z = 364). Subsequently, P4 was attacked by •O 2ˉ and 1 O 2 , and a ring-opening reaction occurred to further oxidize P4 to form P5 (m/z = 362), similar to the previous study (Zhu et al., 2016). According to the LBO calculation results and literature (Wang et al., 2021b), the 32C -28N bond is broken by radical oxidation and caused the -CO group to lose, thereby the P6 (m/z = 334) is formed. ...
... Whereafter, the P6 is converted into P7 (m/z = 291) due to loss of "CH 2 CH 2 NH" and continue to oxidize to produce P8 (m/z = 263). Subsequently, on one hand, the quinolone ring of P8 is oxidized by •O 2ˉ and 1 O 2 to form the intermediate P11 (m/z = 227), on the other hand, the defluorination of P8 also can generate P10 (Zhu et al., 2016;Sayed et al., 2018;Zhang et al., 2015). Ultimately, the intermediate P1, P10 and P11 are further oxidized to CO 2 and H 2 O. ...
The synergistic effect between photocatalytic and peroxymonosulfate (PMS) activation has been widely applied in the field of sewage treatment. In this work, we synthesized a two-dimensional/two-dimensional (2D/2D) CoAl-LDH/BiOBr Z-scheme photocatalyst via a simple method. Then, multiple detection results demonstrated that CoAl-LDH was successfully anchored onto BiOBr, as well as formed an intimate interaction. Moreover, the photocatalytic degradation performance of the catalysts/PMS/vis system had been explored under several conditions (e.g., different catalyst doses, PMS doses, anions and pollutants). The 8 wt% CoAl-LDH/BiOBr composite exhibited the highest degradation efficiency (96%) of ciprofloxacin (CIP). In addition, radicals quenching experiments and electron paramagnetic resonance (EPR) indicate that •O2ˉ and ¹O2 were the primary radicals for CIP degradation. The photoelectrochemical measurement and photoluminescence (PL) confirmed that 8 wt% CoAl-LDH/BiOBr exhibited the highest separation and transfer rate of charge carriers. The liquid chromatography-mass spectrometer (LC-MS) analysis revealed that oxidation of the piperazine ring and defluorination were the main CIP degradation pathways. Density functional theory (DFT) calculation, including the laplacian bond order (LBO) and Fukui index, which was consistent with the results of LC-MS. This study explained the superiority of the synergistic effect between photocatalysis and PMS activation on the degradation of pollutants.
... Najjar et al. (2013) found that with the increase of chlorine dosage, the removal rate of levofloxacin increased, and the inhibition rate of luminescence intensity of luminescent bacteria also increased, indicating that levofloxacin produced more toxic degradation products in the chlorination degradation process. Zhu et al. (2016) studied the electrochemical oxidation process of CIP, NOR, and OFL and the toxicity of the oxidation products. Through the growth inhibition experiment of green algae, it was found that the toxicity of CIP and NOR to green algae remained unchanged after electrochemical oxidation, while the toxicity of OFL increased significantly. ...
Quinolone (QN) antibiotics are a kind of broad-spectrum antibiotics commonly used in the treatment of human and animal diseases. They have the characteristics of strong antibacterial activity, stable metabolism, low production cost, and no cross-resistance with other antibacterial drugs. They are widely used in the world. QN antibiotics cannot be completely digested and absorbed in organisms and are often excreted in urine and feces in the form of original drugs or metabolites, which are widely occurring in surface water, groundwater, aquaculture wastewater, sewage treatment plants, sediments, and soil environment, thus causing environmental pollution. In this paper, the pollution status, biological toxicity, and removal methods of QN antibiotics at home and abroad were reviewed. Literature data showed that QNs and its metabolites had serious ecotoxicity. Meanwhile, the spread of drug resistance induced by continuous emission of QNs should not be ignored. In addition, adsorption, chemical oxidation, photocatalysis, and microbial removal of QNs are often affected by a variety of experimental conditions, and the removal is not complete, so it is necessary to combine a variety of processes to efficiently remove QNs in the future.
... In addition to the degree of mineralization as a measure of the effectiveness of the applied AOP process, another important factor is the change in toxicity during irradiation. Generally, treatment with different AOPs can affect the toxicity of organic products by changing the structure of the parent compound and forming by-products with a lower molecular weight [48][49][50][51][52]. As shown in Fig. 11 there was no complete inhibition of the relative growth of V. fischeri and S. aureus. ...
... The intermediates produced during the degradation of CIP were analyzed by UPLC-MS/MS and possible degradation pathways (as shown in Fig. 8) were suggested based on the molecular structure and m/z values of the intermediates (Fig. S19). In pathway I, the piperazine ring of CIP was oxidized and cracked, resulting in the intermediate P1 (m/z 306) (Zhu et al., 2016). Subsequently, intermediate P2 (m/z 288) was generated, and P2 was a defluorination product formed by the cleavage of the C-F bond and quinolone structure. ...
To avoid the loss of powder co-catalysts in metal sulfide-based co-catalytic Fenton process, we prepared a 3D N-doped graphene aerogel sponge-loaded CoS2 (SCG) and carried out a comparative study of ciprofloxacin (CIP) degradation in SCG/Fenton system, powdered CoS2/Fenton system, and conventional Fenton system. The results showed that SCG co-catalytic performance was comparable to that of powdered CoS2, the basic structure of SCG did not change after 10 times repeated experiments, and the leaching amount of Cox+ was less than 0.1 mg/L. Compared with conventional Fenton system, the content of Fe²⁺ in SCG/Fenton system and powdered CoS2/Fenton system increased from 1.05 mg/L to 8.2 mg/L and 7.9 mg/L, and the decomposition rate of H2O2 increased from 31.9% to 50.8% and 53.1%. The degradation rate constant of SCG/Fenton system was 0.1915 min⁻¹, 5.7 times that of Fenton system and 1.2 times that of powdered CoS2/Fenton system, and SCG/Fenton system had a strong anti-interference ability against Cl⁻, NO3⁻ and humic acid. ¹O2 and ·OH played a leading role in CIP degradation. S²⁻ and S2²⁻ on SCG surface acted as electron donors to accelerate Fe³⁺/Fe²⁺ conversion. The ecotoxicity of CIP degradation products was effectively eliminated. This study provides a reference for designing of 3D co-catalyst and a model for the application of co-catalytic Fenton system.
... Particularly, antibiotics, which are widely used to protect humans and animals against infection and to treat infectious diseases, are released from unmetabolized, unused and expired antibiotics, production plants and sewage sludges into the water environment [1][2][3]. Because of their serious ecological effects, preventing the release of antibiotics into the water and treatment of the water contaminated with antibiotics are of vital importance [4][5][6]. ...
The antibiotic level in the aquatic environment has reached threatening levels for human health and ecosystems. Therefore, it is of vital importance to effectively treat antibiotic-containing wastewater. Advanced oxidation processes (AOPs), especially heterogeneous catalytic processes, are considered the most effective process to treat the residual antibiotics in the wastewaters. In the AOPs, activated carbon-supported catalysts have a synergistic effect thanks to the more effective surface area and by transferring electrons to generate radicals through sp2 covalent carbon bond and oxygen functional groups. In this study, oxidative degradation of ciprofloxacin (CIP) in water by persulfate (PS) activated with an activated carbon-supported cobalt-based dual catalyst (Co-AC) synthesized from biomass mixture and cobalt chloride via chemical activation and pyrolysis was examined. The effects of catalyst dosage, contact time, pH, PS concentration and temperature on the performance of the catalyst were investigated in detail. The synergistic effect of the system depending on various combinations (CIP + PS, CIP + Co-AC, CIP + PS + Co-AC) was determined. Co-AC exhibited high catalytic activity in the CIP oxidation with PS activation, even in various water matrices containing some anions such as Cl−, SO42− and NO3−. CIP in the solution could be completely degraded within 120 min in the presence of 0.75 g/L catalyst, 2 mM PS at 25 °C without any pH adjustment. Quenching experiments showed that the Co-AC dual catalyst successfully activated PS to generate SO4•− and •OH radicals, but the SO4•− was more dominant on the CIP degradation. Kinetic analysis of experimental data revealed that the CIP degradation reaction fits the pseudo-first-order kinetics with an activation energy of 62.69 kJ/mol.
... To date several wastewater treatment methods have been developed to remove antibiotics from wastewater, among these methods, great attention has been paid to EAOP, based on the in-situ production of the highly reactive hydroxyl radical ( OH) The OH produced in the reactor is able to react with any organic contaminant and oxidize it [193]. ...
Environmental problems of great complexity arise from the enormous number of toxic substances that are generated by anthropogenic activities. Seemingly, society encounters new issues every day thus these problems seem to be endless. Now in the face of the COVID‐19 pandemic and the SARS‐CoV‐2 crisis, a large number of emerging treatment compounds generated by pharmaceutical companies worldwide makes future issues even more treacherous. For this reason, there is an increasing need to detect and treat emerging compounds to prevent them from becoming persistent pollutants. This review describes the advances in the use of electrochemical sensors with modified carbon‐based electrodes among other issues, to determine antibiotics, anti‐inflammatories and antidepressants levels in the environment. It further explores technologies suggested for cleaning wastewater polluted by pharmaceutical products using biological or advanced oxidation processes including photolysis, photocatalysis, microwave heating, ultrasound, Fenton, electro‐Fenton, photoelectro‐Fenton and various combined treatments.
... Marquardt's percent standard deviation (MPSD) (Eq. 19) applying error function was used for the fitting of experimental data into the nonlinear regression (Zhu et al. 2016): ...
Heterogeneous photo-electro-Fenton oxidation (hPEF) is known to be a robust technique, which can be employed for promoting organic degradation. This paper describes an environmentally friendly approach with the combination of photocatalysis and electrocatalysis in less acidic pH, aiming to achieve faster mineralization of a pharmaceutical micropollutant without adding any external oxidants. TiO2/GO/loaded Ag non-active electrodes are synthesized for the degradation of bupropion hydrochloride (antidepressant drug). The present work also seeks the parametric modeling and optimization of hPEF process parameters by using R programming. Nonlinear kinetic modeling was performed for the determination of kinetic parameters. The role of selected process parameters on the mineralization of bupropion was also explained in detail. The OH• and O2•− showed their active participation in the degradation process, while Ag and UV-C played an active role in the disinfection of treated wastewater.
... Over 150,000 chemicals have been registered for commercial use in Europe, USA and Canada in the last 30 years, and the production of chemicals is predicted to increase (Muir et al., 2019;UNEA, 2019). Some chemicals enter the ecosystem and have the potential to affect human and animal health (Lei et al., 2015;Zhu et al., 2016). Traditional target analytical methodologies are designed for the detection of a very small fraction of the substances present in the environment, mainly due to the complexity of matrices and consequent need of selectivity. ...
The progress in sensitivity and resolution in mass spectrometers in recent years provides the possibility to detect a broad range of organic compounds in a single procedure. For this reason, suspect and non-target screening techniques are gaining attention since they enable the detection of hundreds of known and unknown emerging contaminants in various matrices of environmental, food and human sources. Sample preparation is a critical step before analysis as it can significantly affect selectivity, sensitivity and reproducibility. The lack of generic sample preparation protocols is obvious in this fast-growing analytical field, and most studies use those of traditional targeted analysis methods. Among them, solvent extraction and solid phase extraction (SPE) are widely used to extract emerging contaminants from solid and liquid sample types, respectively. Sequential solvent extraction and a combination of different SPE sorbents can cover a broad range of chemicals in the samples. Gel permeation chromatography (GPC) and adsorption chromatography, including acidification, are typically used to remove matrix components such as lipids from complex matrices, but usually at the expense of compound losses. Ideally, the purification of samples intended for non-target analysis should be selective of matrix interferences. Recent studies have suggested quality assurance/quality control measures for suspect and non-target screening, based on expansion and extrapolation of target compound lists, but method validations remain challenging in the absence of analytical standards and harmonized sample preparation approaches.
... Many applications have been used to treat effluents rich in FQs, such as electrochemical oxidation [8], biodegradation [9], photodegradation [10], catalytic degradation [11], micro-extraction [12], oxidation (catalytic degradation) [13] and adsorption [14]. From current methods, adsorption has proven to be a easy, high-performance and cheap technique to remove low concentration FQ contaminants from aqueous medium [15]. ...
Antibiotics are among the most critical environmental pollutant drug groups. One of the methods used to remove this pollution is adsorption. In this study, activated carbon was produced from the pumpkin seed shell and then modified with KOH. This adsorbent obtained was used in the re-moval of ciprofloxacin from aqueous systems. Fourier Transform-Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), elemental, X-ray Photoelectron Spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and Zeta analyzes were used for the characterization of the ad-sorbent. In particular, the surface area was found to be a very remarkable value of 2730 m2/g. The conditions of the adsorption experiments were optimized based on interaction time, adsorbent amount, pH and temperature. Over 99% success has been achieved in removal works carried out under the most optimized conditions. In addition, it was determined that the Langmuir isotherm is the most suitable model for the adsorption interaction.
... Many applications have been used to treat effluents rich in FQs, such as electrochemical oxidation [8], biodegradation [9], photodegradation [10], catalytic degradation [11], micro-extraction [12], oxidation (catalytic degradation) [13] and adsorption [14]. From current methods, adsorption has proven to be a easy, high-performance and cheap technique to remove low concentration FQ contaminants from aqueous medium [15]. ...
Antibiotics are among the most critical environmental pollutant drug groups. One of the methods used to remove this pollution is adsorption. In this study, activated carbon was produced from the pumpkin seed shell and then modified with KOH. This adsorbent obtained was used in the re-moval of ciprofloxacin from aqueous systems. Fourier Transform-Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), elemental, X-ray Photoelectron Spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and Zeta analyzes were used for the characterization of the ad-sorbent. In particular, the surface area was found to be a very remarkable value of 2730 m2/g. The conditions of the adsorption experiments were optimized based on interaction time, adsorbent amount, pH and temperature. Over 99% success has been achieved in removal works carried out under the most optimized conditions. In addition, it was determined that the Langmuir isotherm is the most suitable model for the adsorption interaction.
... Recently, antibiotics in aquatic environments have attracted great attention, as trace levels of antibiotics have been reported to be sufficient to influence human health [1]. Thus, more attention is being paid to the detection of antibiotic residues in the environment, antibiotic transformation, the removal technology, and so on [2][3][4]. According to the reports about antibiotic levels in the aquatic environments in China, the median concentrations of most antibiotics were below 100 ng/L in the surface water and 10 ng/L in the groundwater [1]. ...
In this work, a simple and rapid method based on the lateral flow assay (LFA) has been developed for the detection of dual antibiotics. To achieve the quantitative assay and to reduce the non-specific adsorption, an internal system has been developed. A non-specific DNA was exploited as an internal standard and could be recognized by the DNA marker that was coated at the internal line. Two different kinds of aptamers were applied to recognize ampicillin (AMP) and kanamycin (KAM), and the distance between the detection line and conjugate pad was then optimized. Under the optimum conditions, the quantitative assays of AMP (R2 = 0.984) and KAM (R2 = 0.990) were achieved with dynamic ranges of 0.50 to 500.0 ng/L, and of 0.50 to 1000.0 ng/L, respectively. The LOQs of AMP and KAM were 0.06 ng/L and 0.015 ng/L, respectively. Finally, the proposed method has been successfully applied to analyze aquaculture water, tap water, and lake water, and hospital wastewater, indicating the established method could be used to monitor the environment.
... While adsorption is a simple and cost-effective technique, concentrated ENR solutions will be produced after regeneration, causing even greater environmental problems if not disposed properly. Recently, EAOPs have received increasingly attention for the remediation of organic pollutants containing wastewater due to its high efficient, versatility and thorough mineralization [6]. Among various EAOPs technique, electro-Fenton (EF) has been confirmed to be one of the most effective technology for the mineralization of ENR [7]. ...
In this study, enrofloxacin (ENR) degradation by heterogeneous electro-Fenton (hetero-EF) system using Fe/Co/Zn-tri-metal co-doped carbon nanofibers (Fe/Co/[email protected]) modified cathode, which was fabricated by simply carbonization of the electrospun [email protected] It was observed that the Fe/Co/[email protected] electrode showed rougher surface, better crystal shape, more graphitic structures, larger specific surface area (108.0131 m² g⁻¹) and pore volume (0.1109 cm³ g⁻¹) after calcination. Further electrochemical analysis revealed that the calcinated electrode possessed greater catalytic activity towards two-electron oxygen reduction reactions (2e-ORR), smaller electrochemical impedance, and higher corrosion potential compared to the initial [email protected] precursor. Under an optimized condition (e.g., pH=3, and current=40 mA), this hetero-EF system achieved an extraordinary ENR degradation efficiency of 99.08% within 30 min and a TOC removal efficiency of 47.13% within 150 min. Meanwhile, a remarkable yield and generation rate of H2O2 (129.029 mg L⁻¹ and 0.8602 mg L⁻¹ min⁻¹) and ·OH (36.388 mg L⁻¹ and 0.2426 mg L⁻¹ min⁻¹) were obtained. ENR degradation process involved the electron transfer between ≡FeII/III and ≡CoII/III redox couples as well as capture electron directly from cathode, which reduced the consumption of H2O2 and promoted the utilization of H2O2. Radical scavenging and electron paramagnetic resonance (EPR) tests verified that ¹O2 and HO2·/O2·⁻ served as the dominant reactive oxygen species (ROS) for ENR degradation. The possible ENR degradation pathway was deduced to be the open rings of piperazine and quinolone moiety as well as transformation into ciprofloxacin (CIP) according to the identification of produced intermediates. The relatively low energy consumption (3.07 kWh·m⁻³ and 2.54 kWh·m⁻³·order⁻¹) and low intermediates toxicity made the practical applications of this hetero-EF system a real possibility.
... Åëåêòðîõ³ì³÷íå îêèñëåííÿ öèïðîôëîêñàöèíó, íîðôëîêñàöèíó òà îôëîêñàöèíó (àíòèá³-îòèê³â ôòîðîõ³íîëîíîâîãî òèïó) íà àëìàçíîìó åëåêòðîä³, äîïîâàíîìó áîðîì, ïðîõîäèòü ÷åðåç ñòàä³þ ã³äðîêñèëþâàííÿ òà ðîçùåïëåííÿ ï³ïåð³-ç³í³ëîâîãî ê³ëüöÿ ã³äðîêñèë-ðàäèêàëàìè [82]. Ïðîäóêòè îêèñëåííÿ öèïðîôëîêñàöèíó òà íîðôëîêñàöèíó çáåð³ãàþòü àíòèáàêòåð³àëüí³ âëàñ-òèâîñò³, õî÷à ³ ñëàáê³ø³, í³ae âèõ³äí³ ðå÷îâèíè. ...
A critical analysis of literature data on wastewater treatment from pharmaceuticals was carried out. It was shown that many different methods have been proposed for the treatment of wastewaters containing drugs, pharmaceuticals and veterinary medicines; all these methods can be classified as destructive and non-destructive ones. The traditional methods of wastewater treatment include the following: biological treatment, filtration and coagulation/flocculation/sedimentation processes, they being the most common in sewage purification. Some up-to-date and advanced methods (advanced oxidation processes, electrochemical treatment, etc.) are also known. The used methods of wastewater treatment from pharmaceuticals can be conventionally divided into several following groups: (i) chemical treatment with the addition of hydrogen peroxide and/or other oxidants, such as ozone and sodium hypochlorite, together with catalysts to the system; (ii) photocatalytic methods; and (iii) electrocatalytic methods. It was noted that peroxene-based systems are especially promising for practical application; they imply the use of hydroxyl radical as an effective oxidant that is formed from the primary oxidant by its catalytic decomposition. The so-called conditionally reagent-free methods are considered as an alternative to chemical treatment methods, they include electrocatalytic and photochemical techniques, where oxygen-containing radicals (i.e. oxidizing agents) are formed under the action of electric current or UV radiation on the proper catalysts. An additional advantage of electrochemical methods is the possibility of direct electrochemical destruction of organic substances. The main disadvantages of such methods as well as other heterogeneous catalytic systems are relatively high sensitivity to the composition of a catalyst and too low process rate due to decelerated delivery of pollutants to the interfacial boundary where the reaction occurs.
... Although somewhat efficient, traditional water purification methods, such as biodegradation and chlorination cannot efficiently eliminate ofloxacin (Brown et al., 2006) and induce more toxic byproducts (Zhu et al., 2016;Zhang et al., 2019a). Therefore, it is essential to develop effective and environmentally friendly strategies to remove ofloxacin from wastewater and other aquatic environments. ...
Photocatalytic removal is more appropriate for the destruction of organic contaminants. The ternary Bi2MoO6-reduced graphene oxide (rGO)-TiO2 catalyst was synthesized using a simple hydrothermal method, and various surface analytical optical techniques were analyzed. The photocatalytic decomposition efficiency of the Bi2MoO6-rGO-TiO2 composite was 92.3% higher than those of pure and binary photocatalysts. The effects of operational parameters, such as catalyst ratio, catalyst variation, rGO ratio variation, and pH value variation were also analyzed. The as-prepared ternary photocatalyst exhibited low photoluminescence and high photocurrent density, which suppressed photon-induced electron and hole (h⁺) recombination and effective charge separation. The study demonstrated that rGO has excellent electron transfer performance and enhanced photocatalytic reaction stability. The perfect cycling stability of Bi2MoO6-rGO-TiO2 was retained even after five consecutive cycles on the photocatalytic degradation reaction performance. In this study, we propose a decomposition performance mechanism for ofloxacin degradation that underwent visible-light irradiation.
The dielectric barrier discharge (DBD) multi-component system containing plasma, α-Fe2O3/FeVO4, and peroxymonosulfate (PMS) with high catalytic activity was successfully constructed. Thereinto, α-Fe2O3/FeVO4 was loaded on the honeycomb ceramic plate (HCP) surface (α-Fe2O3/FeVO4/HCP) and placed under the water surface below the discharge area. The catalytic activity was evaluated by the removal rate of gatifloxacin (GAT), and the DBD+α-Fe2O3/FeVO4+PMS system exhibited the optimal catalytic activity. The enhanced catalytic activity can be attributed to the fact that the occurrence of synergistic catalysis that simultaneously includes plasma oxidation, photocatalysis, PMS oxidation, O3 catalysis, and Fenton reaction. The effect of various initial degradation parameters including input power, PMS dosage, pH, etc. On GAT removal was investigated. DBD+α-Fe2O3/FeVO4+PMS system has a significant increase in the concentration of H2O2 and O3, and the role played in the multi-component system was analyzed. The identification and analysis of organic matters during GAT degradation were visualized with the help of 3D EEMs. HPLC-MS and theoretical calculations identified the major intermediates and further deduced the possible GAT degradation pathways. Additionally, the acute toxicity of the major intermediates was predicted by the QSAR model. Finally, the possible mechanisms of synergistic catalysis to enhance catalytic activity were discussed based on the characteristics of several advanced oxidation processes (AOPs) and the results of experimental and characterization. This work provides a feasible technical route and theoretical basis for wastewater treatment by plasma combined with other AOPs.
Incomplete degradation of organic pollutants might lead to the increased environmental risk because of the potentially toxic intermediates, especially during chemical treatment processes. However, toxicity changes of common pollutants during chemical oxidation are still unclear because the toxicity results were easily influenced by oxidation means, reaction condition, toxicity assessment method, etc. This review summarized and evaluated the toxicity test and prediction methods commonly used in oxidation process, and then the potential toxic intermediates and their possible producing pathways was proposed as for polycyclic aromatic hydrocarbon, phenols, azo dyes, organophosphorus, organonitrogens, organochlorine pesticides, pharmaceuticals of different classes. Various intermediates, especially the oxygen-containing ones, such as hydroquinone-, benzoquinone-, catechol-like products and halogenated ones are prone to have higher toxicity while some of the dimers and polymers are highly toxic and refractory. In addition, environmental elements such as DOM and halogen ion have the potential to enhance the toxicity. The strategies to reduce the residual toxicity were usually to strengthen the reaction, for example, to increase the oxidant concentration or prolong reaction time. Coupling of multiple technologies is also an effective strategy.
This study explored the feasibility of a coupled system for antibiotic removal and biofuel production through microalgae cultivation. Initial, batch culture experiments demonstrated that sulfadiazine (SDZ) had an inhibitory effect on Chlorella sp. G-9, and 100.0 mg L-1 SDZ completely inhibited its growth. In order to improve SDZ removal efficiency by microalgae, three membrane photobioreactors (MPBRs) with different hydraulic retention times (HRTs) were established for continuous microalgae cultivation. The efficient coupling of SDZ removal and microalgal lipid production was achieved through the gradual increment of influent SDZ concentration from 0 to 100.0 mg L-1. The reduction in SDZ ranged between 57.8 and 89.7%, 54.7-91.7%, and 54.6-93.5% for the MPBRs with HRT of 4 d, 2 d, and 1 d, respectively. Chlorella sp. Was found to tolerate higher concentrations of SDZ in the MPBR system, and the resulting stress from high concentrations of SDZ effectively increased the lipid content of microalgae for potential biodiesel production. With the increase of influent SDZ concentration from 0 to 100.0 mg L-1, the lipid content of microalgae increased by 43.5%. Chlorophyll content, superoxide dismutase activity, and malondialdehyde content of microalgae were also evaluated to explore the mechanism of microalgae tolerance to SDZ stress in MPBR.
Fluoroquinolone antibiotics attract increasing attention in the water treatment field because of the potential adverse effects on aquatic ecosystems and human health. The graphitic carbon nitride (g-C 3 N 4 ) based photocatalysis has been demonstrated as an economically feasible and environmentally benign process to control these persistent contaminants. In this study, a new visible-light-driven of reduced graphene oxide (rGO) and nanoscale zero-valent iron (nZVI) co-modified g-C 3 N 4 -based photocatalyst was synthesized via ultrasonication-assisted chemisorption method. The optimized nZVI-loaded rGO/g-C 3 N 4 (10% IGCN) showed a reaction rate enhancement of 2.12∼3.69-fold and 1.20∼1.68-fold for the degradation of ofloxacin (OFL), norfloxacin (NOR), and ciprofloxacin (CIP) compared to that of carbon-doped g-C 3 N 4 (MCB 0.07 ) and rGO-supported g-C 3 N 4 (7.5% GCN) under the irradiation of simulated visible light, respectively. The enhanced photocatalytic activity can be ascribed to the synergistic effect of nZVI and rGO to improve the separation of charge carriers and boost the harvest of visible light. The degradation mechanisms were explored by scavenger tests and X-ray photoelectron spectroscopy (XPS), indicating that holes (h ⁺ ) played a dominant role in the decomposition of OFL, NOR, and CIP. The piperazine ring and C–N between the piperazine ring and benzene were the primary attack sites of h ⁺ . In addition, the ring-opening oxidation of benzene (C=C bond) connected by the C–F bond may also be an essential step. This study shed light on the degradation mechanism of OFL, NOR, and CIP under visible light irradiation of the 10% IGCN and provided theoretical support for the practical application of photocatalysis in treating antibiotics-containing water.
Pyrite and engineering carbon materials have received increasing attention for their catalytic potential in Fenton reactions due to their extensive sources and low cost. However, effects of carbon materials on the degradation of pollutants by pyrite-catalyzed heterogeneous Fenton oxidation have not been fully understood. In this study, the performance of pyrite-catalyzed heterogeneous Fenton system on the degradation of ciprofloxacin (CIP) was investigated in the presence of activated carbon (AC), biochar (BC), and carbon nanotubes (CNTs). Synchronous and asynchronous experiments (adsorption and catalysis) were conducted to elucidate the roles of the carbon materials in pyrite-catalyzed Fenton reactions. The results demonstrated that all the three carbon materials accelerated the pyrite-catalyzed Fenton oxidation of CIP. Under the experimental conditions, the reaction rates, which were obtained by fitting the synchronous experimental results with the pseudo-first-order kinetic model, of pyrite/AC, pyrite/BC and pyrite/CNTs with H2O2 for the removal of CIP were 8.28, 3.40 and 3.37 times faster than that of pyrite alone. Adsorption experiments and characterization analysis showed that AC had a higher adsorption capacity than BC and CNTs for CIP, which enabled it to distinguish itself in assisting the pyrite-catalyzed Fenton oxidation. In the presence of the carbon materials, the adsorption effect should not be neglected when studying the catalytic performance of pyrite. Free radical quenching experiments and electron spin-resonance spectroscopy (ESR) were used to detect and identify free radical species in the reactions. The results showed that hydroxyl radicals (•OH) contributed significantly to the degradation of CIP. The addition of carbon materials promoted the production of •OH, which favored the degradation of CIP. The results of this study suggested that the synergistic effect of oxidation and adsorption promoted the removal of CIP in pyrite/carbon materials/H2O2 systems, and coupling pyrite and carbon materials shows great potential in treating antibiotic wastewater.
The adsorption capacities of poly(styrene–divinylbenzene) resins were investigated, and resin SA-2, HZ202 and D101 showed the excellent adsorption property at the low doses of chlortetracycline hydrochloride (CH) solution, while resin D101 had outstanding performance at the high dose. The CH adsorption capacity and removal percentage of the D101 resin were 53.2 mg/g and 73.9%, respectively, when the volume of solution containing 5 mg/mL CH was 30 mL. Subsequently, adsorption kinetics, isotherms and thermodynamics for removal of CH from aqueous solution were studied under the different CH concentration. The adsorption process was complied with the pseudo-second-order model and Langmuir model. The adsorption process was fast, and adsorption equilibrium was achieved within 2 h. Based on the Langmuir model, the maximum adsorption capacities of CH on resin D101 were 118.20 mg/g at 298 K, 104.76 mg/g at 303 K and 91.68 mg/g at 308 K. Thermodynamic parameters calculated from the adsorption data at different temperature and CH concentration showed that the adsorption process was exothermal and spontaneous. The negative ∆H also suggested that the main interaction between CH and resin D101 was physical adsorption. The adsorption mechanism was investigated using a scanning electron microscopy, N2 adsorption–desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction spectra. Positive effect of Mg2+ on CH adsorption was observed. Resin D101 could be regenerated by ethanol containing 8% MgCl2, and the CH adsorption capacity of resin D101 decreased by 11.3% after five adsorption–desorption cycles, which displayed that the resin D101 was a promising adsorbent for CH removal in industrial applications.
Near β-Ti alloys, a perfect candidate material for numerous applications in the aerospace, are expected to exhibit high temperature endurability. Here, in order to evaluate the high temperature oxidation mechanism of the near β-Ti alloy, detailed microstructural characterization was performed on a near β-Ti alloy, Ti-55511 alloy after isothermal heat treatment at 600 °C in a tube furnace. Parabolic oxidation kinetics was observed. The oxide layer consisted of Al2O3, TiO2, VO2, and Magnéli phases. Polymorphic phase transformations and Magnéli phases played critical roles in the oxide layer thickening. The formation of defects was highly correlated with the incorporation of oxygen into Al2O3 and VO2, which resulted in lattice distortion of the oxides. Continuous oxidation led to the formation of the higher-valence oxide V2O5 in VO2 particles.
Antibiotics are the therapeutic option for countless infections treatment; unfortunately, they are the second most common group of drugs in wastewaters worldwide due to failures in industrial waste treatments and their irrational use in humans and animals. Several techniques have been assayed for the degradation and mineralisation of antibiotics to reduce the environmental impact; strategies focused on physical, chemical, biological, and combined process design for degradation. antibiotics laccases wastewaters antimicrobial resistance treatment.
The first traces of Tetracycline (TE) were detected in human skeletons from Sudan and Egypt, finding that it may be related to the diet of the time, the use of some dyes, and the use of soils loaded with microorganisms, such as Streptomyces spp., among other microorganisms capable of producing antibiotics. However, most people only recognise authors dating between 1904 and 1940, such as Ehrlich, Domagk, and Fleming. Antibiotics are the therapeutic option for countless infections treatment; unfortunately, they are the second most common group of drugs in wastewaters worldwide due to failures in industrial waste treatments (pharmaceutics, hospitals, senior residences) and their irrational use in humans and animals. The main antibiotics problem lies in delivered and non-prescribed human use, use in livestock as growth promoters, and crop cultivation as biocides (regulated activities that have not complied in some places). This practice has led to the toxicity of the environment as antibiotics generate eutrophication, water pollution, nutrient imbalance, and press antibiotic resistance. In addition, the removal of antibiotics is not a required process in global wastewater treatment standards. This review aims to raise awareness of the negative impact of antibiotics as residues and physical, chemical, and biological treatments for their degradation. We discuss the high cost of physical and chemical treatments, the risk of using chemicals that worsen the situation, and the fact that each antibiotic class can be transformed differently with each of these treatments and generate new compounds that could be more toxic than the original ones; also, we discuss the use of enzymes for antibiotic degradation, with emphasis on laccases.
Pt atomic–level engineering to achieve minimal Pt dosage and maximum electrocatalytic performance is an effective electrocatalyst design strategy. Here a one–step route to synthesize ultrasmall L–Cysteine–protected Pt8 nanoclusters (NCs) and co–catalysis with RuO2–IrO2 for electrocatalytic degradation of tetracycline is shown. Benefiting from sulfhydryl ligand protection and atomic–precision structure, the nanocluster electrocatalyst not only showed outstanding anti–sintering properties but also exhibited excellent electrocatalytic activity (degradation efficiency of 100% and mineralization rate of 73.8%) and high stability for tetracycline degradation, demonstrating the application potentials of Pt NCs catalyst for industrially electrochemical oxidation under practical technical conditions. Moreover, the electrocatalytic degradation mechanism of tetracycline was proposed by determining intermediates using liquid chromatography–mass spectrometry. This work provides an efficient atomic–level engineering strategy to enhance the electrocatalytic performance of Pt–based electrocatalysts, which has important implications for environmental remediation of antibiotic contaminated wastewater.
With focus on industrial scale up, this study presents a critical review of the experimental investigations over the last two decades in eliminating antibiotic and other pharmaceutically active compounds from water environment. The work includes issues typically missing in the current literature. Analysis of the conventional and emerging methods done on systematic classification into some useful domains reveals that around 80% of the experimental studies are on adsorption and chemical oxidation while 10% are on biological methods, 5%, on membrane separation and 2% are on hybrid methods. In terms of the highest reported degree of removal, the methods can be arranged in the order of hybrid treatment (95-98%)> adsorption and chemical oxidation (90-95%)>biological treatment (80-85%). However, critical observation is that these reported data on the highest degrees of removal in most of the cases, are based on laboratory scale studies under very ideal conditions using synthetic solution containing either a single or at the most a few selected drugs. Many studies, particularly on adsorption appear to be repetitive in nature where possibilities of development of adsorption material from nature are almost unlimited. The conventional water treatment plants running on a single method not only fail in effectively treating such complex wastewater but also serve as breeding grounds of antibiotic resistant bacteria. Hybrid methods are emerging as promising in near complete elimination. Strikingly, pilot scale studies are extremely scanty and absence of techno-economic data is hindering transfer of promising technologies from laboratory to the field. A paradigm shift in research focus is absolutely essential towards fast change of the scenario on the ground. This study directs further research towards the promising hybrid strategies in pilot scale to raise scale up confidence with enhanced research funding. This in turn will produce the much-needed impetus to technology transfer. Even the existing wastewater treatment plants can be turned technologically and economically more attractive by augmenting facilities with circular economy approach.
Electrochemical filtration system (EFS) has received broad interest due to its high efficiency for organic contaminants removal. However, the porous nature of electrodes and flow-through operation mode make it susceptible to potential fouling. In this work, we systematically investigated the impacts of biofouling on sulfanilic acid (SA) removal and effluent toxicity in an EFS. Results showed that the degradation efficiency of SA slightly deteriorated from 92.3% to 81.1% at 4.0 V due to the electrode fouling. Surprisingly, after the occurrence of fouling, the toxicity (in terms of luminescent bacteria inhibition) of the EFS effluent decreased from 72.3% to 40.2%, and cytotoxicity assay exhibited similar tendency. Scanning electron microscopy and confocal laser scanning microscopy analyses revealed that biofouling occurred on the porous cathode, and live microorganisms were the dominant contributors, which are expected to play an important role in toxicity suppression. The relative abundance of Flavobacterium genus, related to the degradation of p-nitrophenol (an aromatic intermediate product of SA), increased on the membrane cathode after fouling. The analysis of degradation pathway confirmed the synergetic effects of electrochemical oxidation and biodegradation in removal of SA and its intermediate products in a bio-fouled EFS, accounting for the decrease of the effluent toxicity. Results of our study, for the first time, highlight the critical role of biofouling in detoxication using EFS for the treatment of contaminated water.
Benzotriazole (BTA) is a widely used anticorrosive additive that is of endurance, bioaccumulation and toxicity, and BTA industrial wastewater treatment remains a challenge. This study reports efficient electrochemical removal of BTA by titanium oxide (TiSO) electroactive ceramic membrane (ECM), indicated by 98.1% removal at current density of 20 mA∙cm−2 and permeate flux of 692 LHM under cathode-to-anode flow pattern (1 h). Electrochemical analysis demonstrated the pH-dependent formation of anti-corrosive BTA film on the TiSO anode, which was responsible for improved BTA removal for cathode-to-anode (CA) flow pattern compared with that for anode-to-cathode (AC). The modelling results showed the CA flow pattern to be more favourable for BTA oxidation mediated by electro-generated •OH by preventing the formation of deactivation film via creating an alkaline boundary layer at the anode/electrolyte interface. Intermediates and essential active sites were identified by using experimental analysis and theoretical density functional theory (DFT) calculations, thereby the most likely degradation pathways were underlined. Toxicity analysis revealed remarkable decrease in oral rat LD50 values and bioaccumulation factor during electrochemical degradation of BTA. This study provides a proof-in-concept demonstration of effective removal for anti-corrosive emerging pollutants by TiSO-ECM under flow-through pattern.
This study investigates degradation processes of three antimicrobials in water (norfloxacin, ciprofloxacin, and sulfamethoxazole) by photolysis, focusing on the prediction of toxicity endpoints via in silico quantitative structure-activity relationship (QSAR) of their transformation products (TPs). Photolysis experiments were conducted in distilled water with individual solutions at 10 mg L⁻¹ for each compound. Identification of TPs was performed by means of LC-TOF-MS, employing a method based on retention time, exact mass fragmentation pattern, and peak intensity. Ten main compounds were identified for sulfamethoxazole, fifteen for ciprofloxacin, and fifteen for norfloxacin. Out of 40 identified TPs, 6 have not been reported in the literature. Based on new data found in this work, and TPs already reported in the literature, we have proposed degradation pathways for all three antimicrobials, providing reasoning for the identified TPs. QSAR risk assessment was carried out for 74 structures of possible isomers. QSAR predictions showed that all 19 possible structures of sulfamethoxazole TPs are non-mutagenic, whereas 16 are toxicant, 18 carcinogenic, and 14 non-readily biodegradable. For ciprofloxacin, 28 out of the 30 possible structures for the TPs are mutagenic and non-readily biodegradable, and all structures are toxicant and carcinogenic. All 25 possible norfloxacin TPs were predicted mutagenic, toxicant, carcinogenic, and non-readily biodegradable. Results obtained from in silico QSAR models evince the need of performing risk assessment for TPs as well as for the parent antimicrobial. An expert analysis of QSAR predictions using different models and degradation pathways is imperative, for a large variety of structures was found for the TPs.
Electrochemical reduction of intermolecular disulfide bridges has previously been demonstrated in immunoglobulins but failed to achieve reduction of intramolecular bonds. We now report an improved method that achieves the full reduction of both intermolecular and intramolecular disulfide bridges in a set of monoclonal antibodies based on their intact mass and on MS/MS analysis. The system uses an online electrochemical flow cell positioned online between a chromatography system and a mass spectrometer to give direct information on pairs of heavy and light chains in an antibody. The complete reduction of the intramolecular disulfide bridges is important, as the redox state affects the intact mass of the antibody chain. Disulfide bonds also hamper MS/MS fragmentation of protein chains and thus limit the confirmation of the amino acid sequence of the protein of interest. The improved electrochemical system and associated protocols can simplify sample processing prior to analysis, as chemical reduction is not required. Also, it opens up new possibilities in the top-down mass spectrometry analysis of samples containing complex biomolecules with inter- and intramolecular disulfide bridges.
Increasing amounts of antibiotics are introduced into soils, raising great concerns on their ecotoxicological impacts on the soil environment. This work investigated the individual and joint toxicity of three antibiotics, tetracycline (TC), sulfonamide (SD) and erythromycin (EM) via a whole-cell bioreporter assay. TC, SD and EM in aqueous solution demonstrated cytotoxicity, whilst soil exposure showed genotoxicity, indicating that soil particles possibly affected the bioavailability of antibiotics. Toxicity of soils exposed to TC, SD and EM changed over time, demonstrating cytotoxic effects within 14-d exposure and genotoxic effects after 30 days. Joint toxicity of TC, SD and EM in soils instead showed cytotoxicity, suggesting a synergetic effect. High-throughput sequencing suggested that the soil microbial response to individual antibiotics and their mixtures showed a different pattern. Soil microbial community composition was more sensitive to TC, in which the abundance of Pseudomonas, Pirellula, Subdivision3_genera_incertae_sedis and Gemmata varied significantly. Microbial community functions were significantly shifted by EM amendments, including signal transduction mechanisms, cytoskeleton, cell wall/membrane/envelope biogenesis, transcription, chromatin structure and dynamics, and carbohydrate transport and metabolism. This work contributes to a better understanding of the ecological effects and potential risks of individual and joint antibiotics on the soil environment.
In this work, carbon-doped CoMn2O4/Mn3O4 (C-CoMnO) composite catalyst were prepared via calcining solvothermal product of Mn²⁺, Co²⁺, and 2-methylimidazole in air. The catalytic performance of activating peroxymonosulfate (PMS) for ciprofloxacin (CIP) degradation was discussed. The results showed that the 0.1 g L–1 C-2CoMnO could effectively activate PMS, resulting in 96.18% CIP was degraded within 60 min. The corresponding total organic carbon removal ratio and apparent rate constant were 81.33% and 0.043 min⁻¹, respectively. The influencing factors, such as Co/Mn molar ratios, calcination temperature, PMS concentration, solution pH, and coexisting ions were explored. The optimal catalytic system exhibited good recycling performance, wide pH adaptation and high resistance to salt interference. SO4⋅⁻, ⋅OH, and ⋅O2⁻-based radicals, as well as ¹O2 and surface complexes-based nonradicals were participated in CIP degradation. The CIP degradation pathways were proposed. Density functional theory calculations (DFT) indicated that PMS was more easily activated via Co/Mn synergism. The doped carbon was also contributed to PMS activation via facilitating electron transfer. This study may shed light toward the synergistic effect of metal oxides in PMS activation.
Chlorophenols (CPs) are significant refractory pollutants that are highly toxic to humans and other organisms. Reactive electrode membranes (REMs) show considerable potential in the electrochemical removal of refractory pollutants by allowing flow-through operations with convection-enhanced mass transfer. However, relevant studies are commonly performed on the laboratory scale, and there is no straightforward method that guarantees success in scaling up engineered REM reactors. In this study, we demonstrated that a tubular concentric electrode (TCE) configuration with a titanium suboxide ceramic anode and a stainless-steel cathode is suitable for large-scale CPs removal. Both theoretical and experimental results showed that the TCE configuration not only allows the electrode surface to be orthogonal to electric field lines everywhere, but also has an ohmic resistance that is inversely proportional to the length of the electrode. In addition, the TCE configuration can be operated in either the anode-to-cathode (AC) or the cathode-to-anode (CA) mode based on the flow direction, creating adjustable conditions for selective degradation of CPs. This was confirmed by 98% removal of 2,4-dichlorophenol (2,4-DCP) and 72.5% removal of chemical oxygen demand (COD) in the CA mode, in which the kinetic constant was one order of magnitude higher than that for the AC mode under flow-through single-pass operations. This can be explained by the lower activation energy and free energy in the CA mode, as revealed by theoretical calculations and experimental measurements. The TCE configuration is also suitable for a numbering-up strategy to scale up the electrochemical reactor without increasing the ohmic resistance or decreasing the specific electrode area, achieving 99.4% removal of 2,4-DCP with an energy consumption of 1.5 kW·h·m⁻³ when three TCE modules were employed. This study presents a suitable electrode design configuration for the REM reactor, offering effective strategies to bridge the “Valley of Death” encountered when scaling up the electrochemical removal of CP pollutants.
Amoxicillin (AMX) and Ciprofloxacin (CIP) are antibiotics commonly used in human medicine with high environmental toxicity and poor biodegradability. They have been found in various hospital effluents and groundwater, and their environmental impact is still not fully understood. In this work, we investigated the possibility of treating model wastewaters containing the antibiotics AMX and CIP using ozonation, with the addition of H2O2 under various conditions, including different pH values, H2O2, and ozone dosages. The quantification of and treatment efficacy for antibiotic removal were determined via solid phase extraction followed by chromatographic separation by liquid chromatography coupled with tandem triple quadrupole mass spectrometry (LC/MS/MS). This analytical system is quite efficient for the detection of all major antibiotic classes, even if they are present at very low concentrations. The efficiency of ozonation was determined by measuring the TOC (Total Organic Carbon) changes after ozonation of the model wastewater and by measuring the concentration of the two antibiotics. In a sequential activated sludge process of ozone-treated model wastewater, almost complete TOC removal and an overwhelming decrease in antibiotic concentrations (up to 99%) were observed. Ozonation resulted in complete removal of AMX and CIP in less than 30 and 120 min, respectively. The results of this work indicate that ozonation could be a suitable pretreatment method to reduce the toxicity of contaminants (AMX and CIP) and improve the biodegradability of hospital wastewater.
Antibiotics are frequently detected in aquatic ecosystems, posing a potential threat to the freshwater environment. However, the response mechanism of freshwater microalgae to antibiotics remains inadequately understood. Here, the impacts of azithromycin (a broadly used antibiotic) on microalgae Chlorella pyrenoidosa were systematically studied. The results revealed that high concentrations (5–100 μg/L) of azithromycin inhibited algal growth, with a 96-h half maximal effective concentration of 41.6 μg/L. Azithromycin could weaken the photosynthetic activities of algae by promoting heat dissipation, inhibiting the absorption and trapping of light energy, impairing the reaction centre, and blocking electron transfer beyond QA. The blockage of the electron transport chain in the photosynthetic process further induced the generation of reactive oxygen species (ROS). The increases in the activities of superoxide dismutase, peroxidase and glutathione played important roles in antioxidant systems but were still not enough to scavenge the excessive ROS, thus resulting in the oxidative damage indicated by the elevated malondialdehyde level. Furthermore, azithromycin reduced the energy reserves (protein, carbohydrate and lipid) and impaired the cellular structure. In contrast, a hormesis effect on algal growth was found when exposed to low concentrations (0.5 and 1 μg/L) of azithromycin. Low concentrations of azithromycin could induce the activities of the PSII reaction centre by upregulating the mRNA expression of psbA. Additionally, increased chlorophyll b and carotenoids could improve the absorption of light energy and decrease oxidative damage, which further contributed to the increase in energy reserves (protein, carbohydrate and lipid). The risk quotients of azithromycin calculated in this study were higher than 1, suggesting that azithromycin could pose considerable ecological risks in real environments. The present work confirmed that azithromycin induced dual effects on microalgae, which provided new insight for understanding the ecological risk of antibiotics.
Graphite carbon nitride (g-C3N4) is a common photocatalyst, but it only shows limited photocatalytic performance due to its inherent carrier recombination. Hence, a novel 1D/2D FeV3O8 nanorod/g-C3N4 nanosheets composite photocatalyst...
The development of affordable and modular water/wastewater treatment technologies is highly desirable to counter the adverse effects of antibiotics. Electrochemical treatment, especially electrocatalysis, has a vast potential to degrade antibiotics due to its higher treatment efficiency, low power consumption, and flexible design. Correspondingly, the current review broadly discusses the present status and future trends regarding the electrocatalytic degradation of antibiotics. At the beginning, antibiotic distribution and the merits and demerits of conventional treatment technologies are briefly conveyed. Later, the electrocatalytic removal of antibiotics is discussed in detail with a special focus on catalyst type (e.g., metal-based and carbon-based nanomaterials), oxidative/reductive degradation pathways, and reaction mechanisms. A comprehensive assessment of removal efficiency, operational cost, environmental toxicity of nanomaterials, and residual by-product management has also been carried out. Overall, the feasibility of electrocatalysis technology for antibiotic removal and the critical strategies required for its development have been summarized to provide a roadmap for future research.
Novel [email protected] composites derived from metal-organic framework (MOF) were synthesized. Being subject to pyrolysis under different temperatures endows these [email protected] diverse physical-chemical properties, including morphology, crystal structure, defect level, magnetism, and most importantly, iron phase composition. [email protected] consists mainly of Fe3C and α-Fe, thus possesses strong ferromagnetic properties, which imparts the ability to be separated and recycled. Its catalytic activity towards the activation of persulfate (PS) and the decomposition of sulfamethoxazole (SMX) was found to be the best among all the [email protected], and this activity can be regenerated by simple heat treatment. Given the mixed form of iron and N-doped carbon, α-Fe/Fe3C species provide electrons for PS to decompose and generate sulfate radical (SO4·⁻), hydroxyl radical (·OH), and superoxide radical (O2·⁻), initiating the radical pathway for partial SMX degradation. The positively charged C atoms on PS bonded [email protected], as well as the conversion of O2·⁻ give rise to the generation of singlet oxygen (¹O2), which was responsible for the non-radical pathway for SMX degradation. As a consequence, SMX was degraded to intermediates through five degradation pathways, and finally mineralized to inorganic molecules. The results indicate that [email protected] has great potential to serve as a promising activator for persulfate-mediated environmental remediation.
Potato starch was modified chemically to prepare an adsorbent that is efficient for removing the ciprofloxacin antibiotic from its aqueous solution. The chemical modification process of potato starch involved cross-linking and esterification steps. The high-resolution X-ray diffraction characterization shows that the modification processes do not damage the starch crystal but reduces the crystallinity and the crystal size. In addition to that, holes on the surface of the round and oval shapes of the modified starch were noticed via scanning electron microscope. The parameters that could affect ciprofloxacin removal efficiency on cross-linked potato starch ester were investigated in detail, which included initial concentration of ciprofloxacin in aqueous solution, pH and temperature. The removal efficiency of ciprofloxacin increased with the increase in the initial pH value of the aqueous solution and reached the highest value of removal at a pH of 7, after which it was noticed that the removal efficiency decreased. The removal efficiency was decreased with increasing initial concentration of ciprofloxacin (expressed as chemical oxygen demand) from 25 to 125 ppm. Finally, the results showed that the increase in the temperature treatment from 25 to 45 °C negatively affected the removal efficiency.
Ciprofloxacin (CIP) in natural waters has caused serious environmental problems because of its potent biological activity. In this study, the visible light-induced degradation of CIP was examined by using bismuth oxybromide (BiOBr) as photocatalyst. The flake-shape BiOBr was synthesized by hydrothermal method and characterized by X-ray powder diffraction, scanning electron microscopy and UV–vis diffuse reflectance spectroscopy. The degradation process was monitored by high performance liquid chromatography. The photodegraded intermediates were identified by high performance liquid chromatography–mass spectrometry and the degradation pathway was proposed on the basis of product analysis. It was found that, during the visible light induced degradation of CIP on BiOBr, the piperazine moiety of CIP was the predominant reaction sites, while the quinolone and cyclopropane rings remained essentially intact. The pH-dependence of reaction rates, product analysis and theoretical calculation pointed to a surface reaction mechanism that the CIP oxidation is dominant by the direct hole oxidation process, whereas OH, which is the common active species in the advance oxidation processes, is not effective in the visible light induced photocatalytic process on BiOBr. This study demonstrated that CIP is a good model substrate to uncover the photodegradation mechanism for photocatalyst whose valence band has moderate oxidation ability.
The continuous ozonation of the antibiotic ofloxacin (OFX) has been performed using a synthetic water matrix and in a sewage treatment plant (STP) effluent. The aim was to study the effect of the water matrix on the ozonation with particular emphasis on the aquatic toxicity of treated water. OFX was completely removed in both water matrices, although the amount of ozone consumed for its depletion was strongly matrix-dependent. The extent of mineralization was limited and a number of intermediate transformation products (TPs) appeared, twelve of which could be identified. OFX reaction pathway includes the degradation of piperazinyl and quinolone moieties. The further oxidation of TPs gave rise to the formation and accumulation of carboxylic acids, aldehydes, nitrogen-containing organic compounds and inorganic ions. Aquatic toxicity of treated mixtures was assessed using four standard species: the bacteria Vibrio fischeri and Pseudomonas putida as target organisms and the algae Pseudokirchneriella subcapitata and the protozoan Tetrahymena thermophila as non-target organisms. OFX was toxic for the bacteria and the microalgae at the spiked concentration in untreated water. However, the continuous ozonation at the upper operational limit removed its toxic effects. T. thermophila was not affected by OFX, but was sensitive to STP effluent.
Copyright © 2015 Elsevier B.V. All rights reserved.
Identification the active species and reaction intermediates during the treatment of norfloxacin using Bi2WO6 photocatalysis were investigated in this study. To the best of our knowledge this is the first study on the active species and reaction intermediates for the degradation of any fluoroquinolones (FQs) using Bi2WO6 photocatalysis. The role of active species was determined by the influence of radicals’ scavengers and selected ions. The overall efficiency of Bi2WO6 photocatalysis was ascribed to photolysis, photocatalysis-via hydroxyl radical (OH), and photocatalysis-via direct hole (h+) oxidation, and their contribution was determined to be 15.0, 79.3, and 5.7%, respectively. Fourteen intermediates were identified in the treated samples. Among them, the five amide intermediates in Bi2WO6 photocatalysis were resulted from the OH oxidation on the piperazine in FQs. A reaction formula was developed to describe this reaction where amine translated into amide by the attack of OH radicals. Moreover, a mathematical model was successfully built up to predict the intermediates accumulation as the concentration of initial probe and reaction time is given, which is useful in practical application.
Significance
Understanding how bacteria rapidly evolve under antibiotic selective pressure is crucial to controlling the development of resistant organisms. We show that initial resistance emerges from successful segregation of mutant chromosomes at the tips of filaments followed by budding of resistant progeny. We propose that the first stages of emergence of resistance occur via the generation of multiple chromosomes within the filament and are achieved by mutation and possibly recombination between the chromosomes.
The aim of this review paper is to provide a comprehensive overview of different chemical and environmental aspects concerning fluoroquinolone antibiotics as emerging contaminants. A literature survey has been performed based on 204 papers from 1998 to mid-2013, resulting in a dataset consisting out of 4100 data points related to physical-chemical properties, environmental occurrence, removal efficiencies, and ecotoxicological data. In a first part, an overview is given on relevant physical-chemical parameters to better understand the behavior of fluoroquinolones during wastewater treatment and in the environment. Secondly, the route of these antibiotics after their application in both human and veterinary surroundings is discussed. Thirdly, the occurrence of fluoroquinolone residues is discussed for different environmental matrices. The final part of this review provides a tentative risk assessment of fluoroquinolone compounds and their transformation products in surface waters by means of hazard quotients. Overall, this review shows that fluoroquinolone antibiotics have a wide spread use and that their behavior during wastewater treatment is complex with an incomplete removal. As a result, it is observed that these biorecalcitrant compounds are present in different environmental matrices at potentially hazardous concentrations for the aquatic environment. The latter calls for actions on both the consumption as well as the wastewater treatment aspect to diminish the discharge of these biological active compounds.
Electrochemistry–mass spectrometry is used to simulate redox reactions in many research disciplines because this technique is fast and provides information on compound metabolites. However, the analysis of the degradation of refractory organic pollutants by reactive oxygen species is difficult to achieve by the electrochemistry step. Therefore, here we use online electro-Fenton-mass spectrometry to study for the first time the oxidation of 2,4′,5-trichlorobiphenyl [polychlorinated biphenyl (PCB) 31] by reactive oxygen species and the binding reactions of PCB degradation products with model substances of natural organic matter. The degradation products were identified by coupled Q Trap mass spectrometry. We observed a binding of a degradation product with γ-l-glutamyl-l-cysteinyl-glycine. We propose a transformation pathway. We conclude that online electro-Fenton-mass spectrometry is a promising technique to study the oxidation of refractory organic pollutants and further binding of degradation products with natural organic matter.
We measured concentrations of 56 active pharmaceutical ingredients (APIs) in effluent samples from 50 large wastewater treatment plants across the US. Hydrochlorothiazide was found in every sample. Metoprolol, atenolol, and carbamazepine were found in over 90% of the samples. Valsartan had the highest concentration (5300 ng/L), and also had the highest average concentration (1600 ng/L) across all 50 samples. Estimates of potential risks to healthy human adults were greatest for six anti-hypertensive APIs (lisinopril, hydrochlorothiazide, valsartan, atenolol, enalaprilat, and metoprolol), but nevertheless suggest risks of exposure to individual APIs as well as their mixtures are generally very low. Estimates of potential risks to aquatic life were also low for most APIs, but suggest more detailed study of potential ecological impacts from four analytes (sertraline, propranolol, desmethylsertraline, and valsartan).
The individual and combined toxicities of amoxicillin, erythromycin, levofloxacin, norfloxacin and tetracycline have been examined in two organisms representative of the aquatic environment, the cyanobacterium Anabaena CPB4337 as a target organism and the green alga Pseudokirchneriella subcapitata as a non-target organism. The cyanobacterium was more sensitive than the green alga to the toxic effect of antibiotics. Erythromycin was highly toxic for both organisms; tetracycline was more toxic to the green algae whereas the quinolones levofloxacin and norfloxacin were more toxic to the cyanobacterium than to the green alga. Amoxicillin also displayed toxicity to the cyanobacterium but showed no toxicity to the green alga. The toxicological interactions of antibiotics in the whole range of effect levels either in binary or multicomponent mixtures were analyzed using the Combination Index (CI) method. In most cases, synergism clearly predominated both for the green alga and the cyanobacterium. The CI method was compared with the classical models of additivity Concentration Addition (CA) and Independent Action (IA) finding that CI could accurately predict deviations from additivity. Risk assessment was performed by calculating the ratio between Measured Environmental Concentration (MEC) and the Predicted No Effect Concentration (PNEC). A MEC/PNEC ratio higher than 1 was found for the binary erythromycin and tetracycline mixture in wastewater effluents, a combination which showed a strong synergism at low effect levels in both organisms. From the tested antibiotic mixtures, it can be concluded that certain specific combinations may pose a potential ecological risk for aquatic ecosystems with the present environmentally measured concentrations.
Although antibiotics have been increasingly used and detected in natural samples, their ecotoxicological effects on aquatic wildlife are not yet extensively studied. Considering the environmental threat posed by the biological activity of antibiotics it is quite relevant to assess the resulting impact, especially on sub-lethal endpoints. As such, this study evaluated the effects of ciprofloxacin on Pseudokirchneriella subcapitata and Lemna minor growth, on the survival and reproduction of Daphnia magna and on Gambusia holbrooki survival. The risks associated with ciprofloxacin effects on non-target organisms were quantified through the calculation of the PEC/PNEC ratio. Overall, the toxicity values obtained (at the mg L(-1) level) were higher than the environmental concentrations. P. subcapitata and L. minor were more sensitive under short-term exposures than D. magna and G. holbrooki. No acute toxicity was observed for fish. The chronic assay with D. magna evidenced that long term exposures to lower concentrations of this antibiotic induced impairments on its life-history parameters. Such outcome may pre-empt potential damages on the long-term maintenance of natural populations continuously exposed to the input of antibiotics. Indeed, the PEC/PNEC ratios showed that ciprofloxacin represents a risk for the most sensitive aquatic organisms, since the defined threshold of an acceptable risk was considerably surpassed.
Electrochemistry (EC) coupled to mass spectrometry (MS) has already been successfully applied to metabolism research for pharmaceutical applications, especially for the oxidation behaviour of drug substances. Xenobiotics (chemicals in the environment) also undergo various conversions; some of which are oxidative reactions. Therefore, EC-MS might be a suitable tool for the investigation of oxidative behaviour of xenobiotics. A further evaluation of this approach to environmental research is presented in the present paper using sulfonamide antibiotics. The results with sulfadiazine showed that EC-MS is a powerful tool for the elucidation of the oxidative degradation mechanism within a short time period. In addition, it was demonstrated that EC-MS can be used as a fast and easy method to model the chemical binding of xenobiotics to soil. The reaction of sulfadiazine with catechol, as a model substance for organic matter in soil, led to the expected chemical structure. Finally, by using EC-MS a first indication was obtained of the persistence of a component under chemical oxidation conditions for the comparison of the oxidative stability of different classes of xenobiotics. Overall, using just a few examples, the study demonstrates that EC-MS can be applied as a versatile tool for mechanistic studies of oxidative degradation pathways of xenobiotics and their possible interaction with soil organic matter as well as their oxidative stability in the environment. Further studies are needed to evaluate the full range of possibilities of the application of EC-MS in environmental research.
In this study, exposure and ecotoxicity data of six human pharmaceuticals (carbamazepine, clofibric acid, diclofenac, ofloxacin, propranolol, and sulfamethoxazole) were collected, including our own experimental data and literature data. From this data collection, the two-tiered European draft guideline on the environmental risk assessment of human pharmaceuticals was tested. Measured environmental concentrations in effluents from France and in effluents and surface waters from Germany were compared to the predicted environmental concentrations (PECs) in both countries. In a similar manner, predicted no-effect concentrations (PNECs) derived from acute data and PNECs derived from chronic data were estimated for each pharmaceutical and corresponding PEC/PNEC ratios then were compared in both countries. Globally, results demonstrated that all environmental concentrations (predicted or measured) for each considered pharmaceutical exceeded the 10-ng/L cutoff value, which requires the implementation of the second-tier assessment based on ecotoxicity data. Moreover, the six pharmaceuticals showed a relatively limited acute toxicity, and carbamazepine and propranolol were inaccurately identified as having negligible risks under the current European draft procedure. Such results lead to discussion of the actual procedure on pharmaceuticals, especially on the need of appropriate ecotoxicity tests.
In a recent Opinion article, Martínez et al. outline the obstacles associated with determining the risks presented by antibiotic resistance genes in environmental microbial communities in terms of their potential to transfer to human pathogens. The authors then propose a system for ranking the risks associated with the detection of such genes. Within this system, antibiotic resistance genes that are already present on mobile genetic elements in human pathogens are ascribed the highest risk, whereas resistance genes encoding novel resistance mechanisms that have not yet been found on mobile elements in a pathogen are considered to be part of lower risk categories. We believe that the proposed assessment scheme overestimates the risks associated with well-known resistance genes that are already circulating among human pathogens and underappreciates the potential consequences of the transfer of previously unknown resistance determinants from the environmental resistome.
The degradation of 20.0 mg L−1 of trimethoprim (TMP), an antibiotic commonly detected in wastewaters, in an aqueous solution with 7.0 g L−1 Na2SO4 was accomplished by electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), photoelectro-Fenton (PEF) and solar photoelectro-Fenton (SPEF), as well as by the classical Fenton and photo-Fenton processes. All experiments were performed in a novel 2.2 L lab-scale flow plant equipped with compound parabolic collectors (CPCs) and an electrochemical filter-press cell with a BDD or Pt anode and a carbon-PTFE air-diffusion cathode to electrogenerate H2O2. The effect of initial Fe2+ concentration, current density and pH on the PEF method with the BDD anode (PEF-BDD) was firstly assessed by means of TMP and dissolved organic carbon (DOC) decays, aiming to establish a treatment process using minimal iron concentration, adequate current density/H2O2 production and maximal pH. This treatment was efficiently performed using a low Fe2+ dose of 2.0 mg L−1, a low current density of 5 mA cm−2 and pH of 3.5 without iron precipitation. The relative oxidation ability of EAOPs using the BDD/air-diffusion cell increased in the order: AO-H2O2 < EF < PEF < SPEF. The EF-BDD and PEF-BDD processes were more effective than the comparable Fenton and photo-Fenton ones. The PEF-BDD process exhibited slightly faster TMP degradation than the PEF-Pt one, whereas in SPEF the influence of the anode was almost negligible. After ca. 37 kJ L−1 UV energy, 77 and 73% mineralization with 30 and 26% current efficiency and 1.2 and 0.9 kWh m−3 energy cost were obtained, respectively. It was found a slow and partial TMP mineralization mainly linked to the formation of a high content of hardly oxidizable N-derivatives, containing the major part of N. Up to 18 aromatic products and 19 hydroxylated derivatives were detected by LC-MS during TMP degradation by PEF-Pt. An additional SPEF-Pt experiment using a real wastewater matrix spiked with TMP attained slower TMP and DOC decays.
A group of white rot fungi (Irpex lacteus, Panus tigrinus, Dichomitus squalens, Trametes versicolor and Pleurotus ostreatus) was investigated for the biodegradation of norfloxacin (NOR), ofloxacin (OF) and ciprofloxacin (CIP). The selected fluoroquinolones were readily degraded almost completely by I. lacteus and T. versicolor within 10 and 14d of incubation in liquid medium, respectively. The biodegradation products were identified by liquid chromatography-mass spectrometry. The analyses indicated that the fungi use similar mechanisms to degrade structurally related antibiotics. The piperazine ring of the molecules is preferably attacked via either substitution or/and decomposition. In addition to the degradation efficiency, attention was devoted to the residual antibiotic activities estimated using Gram-positive and Gram-negative bacteria. Only I. lacteus was able to remove the antibiotic activity during the course of the degradation of NOR and OF. The product-effect correlations evaluated by Principal Component Analysis (PCA) enabled elucidation of the participation of the individual metabolites in the residual antibacterial activity. Most of the metabolites correlated with the antibacterial activity, explaining the rather high residual activity remaining after the biodegradation. PCA of ligninolytic enzyme activities indicated that manganese peroxidase might participate in the degradation.
Copyright © 2014 Elsevier Ltd. All rights reserved.
To investigate the occurrence of antibiotics in urban rivers and their association with antibiotic-resistant Escherichia coli, 20 (fluoro)quinolone antibiotics (FQs), 16 tetracycline antibiotics (TCs) and their degradation products, and 25 sulfonamides (SAs) and some degradation products were determined in 45 river samples and 13 discharged wastewater samples collected from Wenyu River and its tributaries and 4 composite effluent samples from sewage treatment plants in Beijing, China. Fifteen FQs, eight TCs, including four degradation chemicals, and sixteen SAs, including four acetylated products, were detected in the river water. The SAs were the dominant antibiotic (total concentrations up to 3164.0 ng/L) in river water, followed by FQs (1430.3 ng/L) and TCs (296.6 ng/L). The sum concentrations for each class of detected antibiotic in the 13 discharge site samples were higher than those in river samples, up to 12326.7 ng/L for SAs, 6589.2 ng/L for FQs, and 730.1 ng/L for TCs, largely contributing to the high concentrations in the river basin. Log-linear regression analysis confirmed that the concentrations of FQs, TCs, and SAs in the Wenyu River basin were strongly correlated with the number of E. coli resistant to FQs (p < 0.05), TCs (p < 0.05), and SAs (p < 0.05), providing evidence for the environmental impacts of antibiotic usage.
The effect of ampicillin (AMP), amoxicillin (AMX), cephalotin (CEP), ciprofloxacin (CPF), gentamycin (GEN), and vancomycin (VAN) have been examined individually and as binary mixtures, on a non-target aquatic organism, the green alga Pseudokichneriella subcapitata. The β-lactam antibiotics AMP and AMX were not toxic to the alga at concentrations up to 2000mgl(-1) (less than 10% of algal growth inhibition), whereas the fluoroquinolone CPF, and the aminoglycoside GEN were the most toxic antibiotics, with an EC50=11.3±0.7mgl(-1) and 19.2±0.5mgl(-1), respectively. The cephalosporin CEP and the glycopeptide VAN were less toxic than the last two mentioned, showing an EC50>600mgl(-1) and 724±20mgl(-1), respectively. The toxicological interactions of binary mixtures were predicted by 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 1 and 50mgl(-1). In all cases a clear synergistic effect was observed, showing that single compound toxicity data are not adequate for the prediction of aquatic toxicities of antibiotic mixtures. Risk assessment was performed by calculating the ratio between predicted environmental concentrations (PEC) and the predicted no effect concentration (PNEC). All the antibiotics tested, excepting GEN, have a potential ecological risk, taking into account the PEC of hospital effluents from Buenos Aires, Argentina. These risks increase when antibiotics are present in binary mixtures.
Copyright © 2014 Elsevier Inc. All rights reserved.
Ciprofloxacin and sulfamethoxazole are two antibiotics commonly detected in the aquatic environment, but information on their toxicity towards natural microbial communities is largely absent. In particular no data are available for marine microorganisms. The aim of the current study was therefore to evaluate the chronic toxicity of ciprofloxacin and sulfamethoxazole to natural marine biofilms (periphyton), a complex ecological community comprising a variety of bacterial and algal species. The biofilms were sampled along the Swedish west coast and subsequently exposed over 4 days in a semi-static system to a concentration series of each antibiotic.
The treatment of ciprofloxacin (CIP) and ibuprofen (IBU) in test solutions by ferrate(VI) was investigated in this study. A series of jar test was performed in bench-scale at pH 6-9 and ferrate(VI) dose of 1-5mgL(-1). Results demonstrated that ferrate(VI) removed CIP from test solutions efficiently, with above 70% of reduction under study conditions. In contrary, the removal rates of IBU were very low, less than 25% in all conditions. Raising ferrate(VI) dose improved the treatment performance, while the influence of solution pH was not significant at pH 6-9 compared with that of ferrate(VI) dose. In addition, kinetic studies of ferrate(VI) with both compounds were carried out at pH 8 and pH 9 (20°C). Ferrate(VI) had a much higher reactivity with CIP than IBU at pH 8 and pH 9, with CIP's apparent second-order rate constants of 113.7±6.3M(-1)s(-1) and 64.1±1.0M(-1)s(-1), respectively. The rate constants of ferrate(VI) with IBU were less than 0.2M(-1)s(-1) at pH 8 and pH 9. Furthermore, seven oxidation products (OPs) were formed during CIP degradation by ferrate(VI). The attack on the piperazinyl ring of the CIP by ferrate(VI) appeared to lead to the cleavage or hydroxylation of the rings, and the attack on the quinolone moiety by ferrate(VI) might lead to the cleavage of the double bond at the six-member heterocyclic ring. No OPs of IBU were detected during ferrate(VI) oxidation due to very small part of IBU was degraded by ferrate(VI).
The electrochemical mineralization of environmentally persistent long-chain perfluorinated carboxylic acids (PFCAs), i.e., perfluorononanoic acid (C8F17COOH, PFNA) and perfluorodecanoic acid (C9F19COOH, PFDA) was investigated in aqueous solutions (0.25 mmol L(-1)) over Ti/SnO2-Sb-Ce (SnO2), Ti/SnO2-Sb/Ce-PbO2 (PbO2), and Ti/BDD (BDD) anodes under galvanostatic control at room temperature. Based on PFCA decay rate, total organic carbon (TOC) reduction, defluorination ratio, safety, and energy consumption, the performance of PbO2 electrode was comparable with that of BDD electrode. After 180 min electrolysis, the PFNA removals on BDD and PbO2 electrodes were 98.7 ± 0.4% and 97.1 ± 1.0%, respectively, while the corresponding PFDA removals were 96.0 ± 1.4% and 92.2 ± 1.9%. SnO2 electrode yielded lower PFCA removals and led to notable secondary pollution by Sb ions. The primary mineralization product, F(-), as well as trace amounts of intermediate PFCAs with shortened chain lengths, were detected in aqueous solution after electrolysis. On the basis of these results, a degradation mechanism including three potential routes is proposed: via formation of short-chain PFCAs by stepwise removal of CF2; direct mineralization to CO2 and HF; conversion to volatile fluorinated organic compounds. The results presented here demonstrate that electrochemical technique exhibits high efficiency in mineralizing PFNA and PFDA under mild conditions, and is promising for the treatment of long-chain PFCAs in wastewater.
With the support of ESCMID and European countries, EUCAST has developed a disk diffusion test with zone diameter breakpoints correlated with the EUCAST clinical MIC breakpoints. The development of the EUCAST disk diffusion method and quality control criteria are described, together with guidance on quality control and implementation of the method in clinical microbiology laboratories. The method includes the use of Mueller-Hinton agar without supplements for non-fastidious organisms and with 5% mechanically defibrinated horse blood and 20 mg/L β-NAD for fastidious organisms, a standardized inoculum resulting in confluent growth, an incubation time of 16-20 h, a reading guide on how to read zone diameters on individual species-agent combinations and zone diameter breakpoints calibrated to the EUCAST clinical MIC breakpoints. EUCAST recommendations are described in detail and updated regularly on the EUCAST website (http://www.eucast.org).
This spectroscopic study presents the kinetics and degradation pathways of oxidation of ciprofloxacin by permanganate in alkaline medium at constant ionic strength of 0.04mol−3. Orders with respect to substrate, oxidant and alkali concentrations were determined. Effect of ionic strength and solvent polarity of the medium on the rate of the reaction was studied. The oxidation products were identified by LC-ESI-MS technique. Product characterization of ciprofloxacin reaction mixtures indicates the formation of three major products corresponding to m/z 263, 306, and 348 (corresponding to full or partial dealkylation of the piperazine ring). The piperazine moiety of ciprofloxacin is the predominant oxidative site to KMnO4. Product analyses showed that oxidation by permanganate results in dealkylation at the piperazine moiety of ciprofloxacin, with the quinolone ring essentially intact. The reaction kinetics and product characterization point to a reaction mechanism that likely begins with formation of a complex between ciprofloxacin and the KMnO4, followed by oxidation at the aromatic N1 atom of piperazine moiety to generate an anilinyl radical intermediate. The radical intermediates subsequently undergo N-dealkylation. Investigations of the reaction at different temperatures allowed the determination of the activation parameters with respect to the slow step of proposed mechanism. The proposed mechanism and the derived rate laws are consistent with the observed kinetics.
Electro-oxidation tests with different anodes (Ti/Pt, DSA® type, graphite and three-dimensional (3D) electrode made of a fixed bed of activated carbon pellets) were performed on aqueous solutions containing the antibiotics Ofloxacin and Lincomycin. The effectiveness of the treatment of wastewater containing pharmaceuticals was assessed, as well as the electro-oxidation mechanism.The use of high electrode potentials (>2.8V versus NHE) ensured either significant anodic surface activation or minimization of fouling by in situ generated polymeric material. The use of a membrane-divided cell showed positive aspects in terms of molecule demolition, and average power consumption. The electro-oxidation was found to occur with first order kinetics mainly at anode surface when using Na2SO4 at low concentration (0.02N). Under these conditions, Ofloxacin is efficiently oxidized over all tested anodes (e.g. 50mgcm−2A−1h−1 for the bi-dimensional Ti/Pt electrode), whereas Lincomycin is oxidized with slow overall kinetics mainly due to difficult deprotonation, a step that precedes the primary electron transfer stage of the oxidation process. The three-dimensional electrode would be the most appropriate for continuous industrial-scale process. However, at the used potential, unacceptable corrosion of the carbon based electrode was noticed.
Thermospray ionization combined with a quadrupole mass spectrometer was used on line to detect electrochemically generated products directly from solution. To do so, an electrochemical cell was constructed and connected with the mass spectrometer in such a way that the electrolyte was forced by pressure from the working electrode into the heated capillary tube of the thermospray system. The fast response achieved allowed analysis to be performed in parallel with a cyclic voltammetry curve. The utility of the method is demonstrated by means of the electrooxidatlon of N,N-dimethylaniline in an aqueous medium. The potential-dependent formation of dimers and trimers is shown.
This study addressed the formation and properties of degradation products of ciprofloxacin, norfloxacin and lomefloxacin formed during ozonation of secondary wastewater effluent containing these fluoroquinolone antibiotics. The generation of the degradation products was interpreted in the context of transformations of effluent organic matter (EfOM) tracked via absorbance measurements. The structures of 20 degradation products were elucidated for ciprofloxacin and norfloxacin, respectively. 27 degradation products were identified for lomefloxacin. The prevalent oxidation pathways were suggested based on the structures of the identified products formed in the absence and presence of the hydroxyl radical scavenger t-butanol. These pathways were largely similar for all studied fluoroquinolones and involved attacks on the piperazine ring and the quinolone structure. The quinolone ring remained intact in the presence of t-butanol thus indicating that this functional group could only be oxidized by OH radicals while the piperazine ring was readily oxidized by molecular ozone. The cleavage of the quinolone moiety that resulted in several identified degradation products occurred via the attack by hydroxyl radicals on the carbon-carbon double bond adjacent to the carboxylic acid group. Lomefloxacin had more diverse oxidation products due to the presence of a methyl group on its piperazinyl ring. The concentrations of the identified degradation products behaved non-monotonically as a function of ozone dose or treatment time, yet exhibited interpretable correlations versus changes of EfOM absorbance. Examination of these correlations allowed developing a novel approach for elucidating the transformations of fluoroquinolone antibiotics during ozonation.
Risk assessment of xenobiotics requires a comprehensive understanding of their transformation in the environment. As most of the transformation processes usually involve a redox reaction or a hydrolysis as the first steps of the transformation, we applied an approach that uses an electrochemical cell to investigate model "redox" reactions in aqueous solutions for environmental processes. We investigated the degradation of a variety of xenobiotics from polar to nonpolar and analyzed their degradation products by on-line coupling of electrochemistry with mass spectrometry (EC-MS). Furthermore, we evaluated possible binding reactions with regard to the generation of non-extractable residues with some model substances (catechol, phthalic acid, γ-l-Glutamyl-l-cysteinyl-glycine (GSH) and l-histidine) deduced from a natural organic matter (NOM) structure model and identified possible binding-sites. Whereas typically investigations in soil/water-systems have been applied, we used to our knowledge for the first time a bottom-up approach, starting from the chemicals of interest and different model substances for natural organic matter to evaluate chemical binding mechanisms (or processes) in the EC-MS under redox conditions. Under oxidative conditions, bindings of the xenobiotics with catechol, GSH and histidine were found, but no reactions with the model compound phthalic acid were observed. In general, no chemical binding has yet been found under reductive conditions. In some cases (i.e. benzo[a]anthracene) the oxidation product only underwent a binding reaction, whereas the xenobiotic itself did not undergo any reactions. EC-MS is a promising fast and simple screening method to investigate the environmental behavior of xenobiotics and to evaluate the potential risks of newly synthesized substances.
Ofloxacin (OFL), a broad-spectrum and widespread-used photolabile fluoroquinolone, is frequently found in treated wastewaters, aquatic and terrestrial ecosystems leading to increasing concern during the past decades regarding its effects to the environment and human health. The elimination of OFL and other xenobiotics by the application of advanced oxidation processes using photolytic (PL) and photocatalytic (PC) treatments seems promising. However, an integrated assessment scheme is needed, in which, not only the removal of the parent compound, but also the effects of the photo-transformation products (PTPs) are investigated. For this purpose, in the present study, a chronic ecotoxic assessment using representative bacteria of marine and terrestrial ecosystems and a cytostatic and genotoxic evaluation using hepatoma cell line were performed. PL and PC treatments of OFL were applied using UV radiation. The photo-transformation of OFL during the treatments was monitored by DOC measurements and UPLC-MS/MS analysis. The chronic ecotoxicity of OFL and treated samples was evaluated using Pseudomonas putida and Vibrio fischeri; whereas the cytostasis and genotoxicity were estimated by the cytokinesis-block micronucleus assay (CBMN). The main results suggest that photo-transformation of OFL took place during these treatments since the concentration of OFL decreased when the irradiation time increased, as quantified by UPLC-MS/MS analysis, and this was not coupled with an analogous DOC removal. Furthermore, nine compounds were identified as probable PTPs formed through piperazinyl dealkylation and decarboxylation. The ecotoxicity of treated solutions to the bacteria studied decreased while the cytostasis to the hepatoma cell line remained at low levels during both treatments. However, the genotoxicity to the hepatoma cell line demonstrated a different pattern in which treated samples induced a greater number of MNi for the 4-16min of irradiation (p<0.05) during both treatments. After 64min of irradiation, the effects decreased to non genotoxic levels (p<0.05). These findings suggest that UV radiation for various treatment processes (catalytic or not), such as disinfection, may create genotoxic by-products. Therefore, in relevant technical applications, the residence time during treatment should receive special attention.
Solutions of the veterinary fluoroquinolone antibiotic enrofloxacin in 0.05 M Na2SO4 of pH 3.0 have been comparatively degraded by electrochemical advanced oxidation processes such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), photoelectro-Fenton (PEF) and solar photoelectro-Fenton (SPEF) at constant current density. The study has been performed using an undivided stirred tank reactor of 100 ml and a batch recirculation flow plant of 2.5 l with an undivided filter-press cell coupled to a solar photoreactor, both equipped with a Pt or boron-doped diamond (BDD) anode and a carbon–polytetrafluoroethylene gas diffusion cathode to generate H2O2 from O2 reduction. In EF, PEF and SPEF, hydroxyl radical (OH) is formed from Fenton's reaction between added catalytic Fe2+ and generated H2O2. Almost total decontamination of enrofloxacin solutions is achieved in the stirred tank reactor by SPEF with BDD. The use of the batch recirculation flow plant showed that this process is the most efficient and can be viable for industrial application, becoming more economic and yielding higher mineralization degree with raising antibiotic content. This is feasible because organics are quickly oxidized with OH formed from Fenton's reaction and at BDD from water oxidation, combined with the fast photolysis of complexes of Fe(III) with generated carboxylic acids under solar irradiation. The lower intensity of UVA irradiation used in PEF with BDD causes a slower degradation. EF with BDD is less efficient since OH cannot destroy the most persistent Fe(III)–oxalate and Fe(III)–oxamate complexes. AO-H2O2 with BDD yields the poorest mineralization because pollutants are only removed with OH generated at BDD. All procedures are less potent using Pt as anode due to the lower production of OH at its surface. Enrofloxacin decay always follows a pseudo first-order reaction. Its primary aromatic by-products and short intermediates including polyols, ketones, carboxylic acids and N-derivatives are detected by GC–MS and chromatographic techniques. The evolution of F−, NO3− and NH4+ ions released to the medium during each process is also determined.