Dependence of transformation product formation on pH during photolytic and photocatalytic degradation of ciprofloxacin

Mapping the risk of ciprofloxacin in European water bodies: Incorporating the impact of bioavailability

Widespread use of ciprofloxacin (CIP) in surface waters has raised ecological and human health concerns. However, the measured environmental concentration (MEC) of CIP may not directly indicate its ecological impact because CIP bioavailability and thus toxicity are influenced by environmental factors, such as pH and dissolved organic carbon (DOC). The present study integrates CIP toxicity as a function of pH and DOC into an environmental risk assessment (ERA) of CIP in European surface waters. A bioavailability model and water quality databases were used to estimate the predicted no-effect concentration (PNECECO) of CIP to protect freshwater ecosystems under five ERA scenarios. PNECECO values were predicted following the European Medicines Agency guidelines using ecotoxicity data for the cyanobacterium Microcystis aeruginosa, identified as the freshwater species most sensitive to CIP. The PNECECO values predicted under Scenarios 1 (not considering bioavailability) and 2 (assuming the most bioavailable form of CIP, the zwitterion CIP+/- at maximum relative abundance) were 25 ng L-1 and 32 ng L-1, respectively. Including the bioavailability effect of pH in Scenario 3 resulted in a range of PNECECO values from 25.0 to 62.4 ng L-1 (across Europe) whereas further including weak (Scenario 4) and strong (Scenario 5) CIP-DOC binding led to larger regional variations in PNECECO (25.8-1207 ng L-1). The PNECECO values were combined in Monte Carlo simulations with MEC data for the CIP to assess the probabilities of unacceptable risk (PUR), uncertain risk (PUN), and acceptable risk (PAR) for Europe and for ten countries. The EU-wide PUR values (9.8 %-22.0 %) were unrepresentative of individual countries (0 %-99 %), while variations in PUR across scenarios (0 %-95 %) indicated different influences of pH and DOC by country. Overall, DOC has a stronger impact than pH on the predicted no-effect concentrations (PNECs) and on the ecological risk of CIP, and thus the consideration of bioavailability can greatly improve the environmental relevance of the ERA outcomes.

Fate of emerging antibiotics in soil-plant systems: A case on fluoroquinolones

Fluoroquinolones (FQs), a class of broad-spectrum antibiotics widely used to treat human and animal diseases globally, have limited adsorption and are often excreted unchanged or as metabolites. These compounds enter the soil environment through feces, urban wastewater, or discharge of biological solids. The fluorine atoms in FQs impart high electronegativity, chemical stability, and resistance to microbial degradation, allowing them to potentially enter food chains. The persistence of FQs in soils raises questions about their impacts on plant growth, an aspect not yet conclusively determined. We reviewed whether, like other organic compounds, FQs are actively absorbed by plants, resulting in bioaccumulation and posing threats to human health. The influx of FQs has led to antibiotic resistance in soil microbes by exerting selective pressure and contributing to multidrug-resistant bacteria. Therefore, the environmental risks of FQs warrant further attention. This work provides a comprehensive review of the fate and behavior of FQs at the plant-environment interface, their migration and transport from the environment into plants, and associated toxicity. Current limitations in research are discussed and prospects for future investigations outlined. Thus, understanding antibiotic behavior in plants and translocation within tissues is not only crucial for ecosystem health (plant health), but also assessing potential human health risks. In addition, it can offer insights into the fate of emerging soil pollutants in plant-soil systems.

Photochemical degradation of antibiotics: real-time investigation by aerodynamic thermal breakup droplet ionization mass spectrometry

A method is proposed for studying photochemical reactions in solution in real time using aerodynamic/thermal breakup droplet ionization mass spectrometry. Capabilities of the method were demonstrated by analyses of photodegradation processes of three antibiotics (thiamphenicol, ciprofloxacin, and ofloxacin) by means of aqueous solutions. The method rapidly provided information about photochemical changes for understanding the photochemical processes.

Trimetallic MOF-derived Fe-Mn-Sn oxide heterostructure enabling exceptional catalytic degradation of organic pollutants

Developing efficient and environmentally benign heterogeneous catalysts that activate peroxymonosulfate (PMS) for the degradation of persistent organic contaminants remains a challenge. Metal-organic frameworks (MOFs)-derived metal oxide catalysts in advanced oxidation processes (AOPs) have received considerable attention research fraternity. Herein, we report an innovative magnetic trimetallic MOF-derived Fe-Mn-Sn oxide heterostructure (FeMnO@Sn) with adjustable morphology, size and Sn content, prepared through an impregnation-calcination strategy. The formation of a novel magnetic Fe2O3/Fe3O4/Mn3O4 heterostructure induces the generation of abundant Fe2+ and Mn2+ sites on the FeMnO@Sn surface. Meanwhile, the introduction of SnO2 into the Fe2O3/Fe3O4/Mn3O4 heterostructure facilitates the cleavage of the OO bond in adsorbed PMS. The synergy among the different functionalities of each metal oxide plays a vital role in the swift and effective degradation of pollutants. In addition, the uniquely designed catalyst exhibits magnetic properties that facilitate easy recycling and repeated use, thereby meeting environmental protection requirements. Overall, this research highlights the design of heterogeneous catalysts for the effective activation of PMS and provides valuable insights for the advancement of future environmental catalysts.

Photocatalytic activation of peroxydisulfate by UV-LED through rGO/g-C3N4/SiO2 nanocomposite for ciprofloxacin removal: Mineralization, toxicity, degradation pathways, and application for real matrix

If trace amounts of antibiotics remain in the environment, they can lead to microbial pathogens becoming resistant to antibiotics and putting ecosystem health at risk. For instance, ciprofloxacin (CIP) can be found in surface and ground waters, suggesting that conventional water treatment technologies are ineffective at removing it. Now, a rGO/g-C3N4/SiO2 nanocomposite was synthesized in this study to activate peroxydisulfate (PDS) under UVA-LED irradiation. UVA-LED/rGO-g-C3N4-SiO2/PDS system performance was evaluated using Ciprofloxacin as an antibiotic. Particularly, rGO/g-C3N4/SiO2 showed superior catalytic activity for PDS activation to remove CIP. Operational variables, reactive species determination, and mechanisms were investigated. 0.85 mM PDS and 0.3 g/L rGO/g-C3N4/SiO2 eliminated 99.63% of CIP in 35 min and mineralized 59.78% in 100 min at pH = 6.18. By scavenging free radicals, bicarbonate ions inhibit CIP degradation. According to the trapping experiments, superoxide (O2•-) was the main active species rather than sulfate (SO4•-) and hydroxyl radicals (•OH). RGO/g-C3N4/SiO2 showed an excellent recyclable capability of up to six cycles. The UVA-LED/rGO-g-C3N4-SiO2/PDS system was also tested under real conditions. The system efficiency was reasonable. By calculating the synergistic factor (SF), this work highlights the benefit of combining composite, UVA-LED, and PDS. UVA-LED/rGO-g-C3N4-SiO2/PDS had also been predicted to be an eco-friendly process based on the results of the ECOSAR program. Consequently, this study provides a novel and durable nanocomposite with supreme thermal stability that effectively mitigates environmental contamination by eliminating antibiotics from wastewater.

Revealing the synergistic effect between radical and non-radical species of sulfur-doped carbon nitride for ciprofloxacin removal: Based on density functional theory study

The distinct characteristics of active species produced during the photocatalytic reaction can result in alterations in the degradation routes of organic pollutants with diverse chemical structures. The relationship between the active species and degradation pathways of organic pollutants lacks a direct experimental or characterization method, so in-depth research is still needed to understand the details of their interactions. In this study, sulfur-doped bulk carbon nitride (SBCN) was prepared based on bulk carbon nitride (BCN), and the process of S-doping enhancing the production of O21 was revealed. Through the degradation experiment, the degradation rate of CIP by SBCN reached 91 %, which was higher than that of BCN (66 %). The increase of degradation rate was mainly attributed to the increase of O21. Through the density functional theory (DFT) calculation of CIP and its degradation intermediate, due to the preferential oxidation of CIP by O21, O21 changes the initial degradation direction of CIP, releasing more attack sites for ˙O2-, thereby achieving more efficient degradation of CIP through the synergy of O21 and ˙O2-. In this study, the attack preferences of the active species and their synergistic promotion provide important insights for the efficient photocatalytic degradation of organic pollutants.

Empowering Adsorption and Photocatalytic Degradation of Ciprofloxacin on BiOI Composites: A Material-by-Design Investigation

Binary and ternary composites of BiOI with NH2-MIL-101(Fe) and a functionalized biochar were synthesized through an in situ approach, aimed at spurring the activity of the semiconductor as a photocatalyst for the removal of ciprofloxacin (CIP) from water. Experimental outcomes showed a drastic enhancement of the adsorption and the equilibrium (which increased from 39.31 mg g-1 of bare BiOI to 76.39 mg g-1 of the best ternary composite in 2 h time), while the kinetics of the process was not significantly changed. The photocatalytic performance was also significantly enhanced, and the complete removal of 10 ppm of CIP in 3 h reaction time was recorded under simulated solar light irradiation for the best catalyst of the investigated batch. Catalytic reactions supported by different materials obeyed different reaction orders, indicating the existence of different mechanisms. The use of scavengers for superoxide anion radicals, holes, and hydroxyl radicals showed that although all these species are involved in CIP photodegradation, the latter play the most crucial role, as also confirmed by carrying out the reaction at increasing pH conditions. A clear correlation between the reduction of BiOI crystallite sizes in the composites, as compared to the bare material, and the material performance as both adsorbers and photocatalyst was identified.

Facile aqueous synthesis and comparative evaluation of TiO2-semiconductor and TiO2-metal nanohybrid photocatalysts in antibiotics degradation under visible light

Advanced oxidation processes using TiO2-based nanomaterials are sustainable technologies that hold great promise for the degradation of many types of pollutants including pharmaceutical residues. A wide variety of heterostructures coupling TiO2 with visible-light active nanomaterials have been explored to shift its photocatalytic properties to harness sun irradiation but a systematic comparison between them is lacking in the current literature. Furthermore, the high number of proposed nanostructures with different size, morphology, and surface area, and the often complex synthesis processes hamper the transition of these materials into commercial and effective solutions for environmental remediation. Herein, we have designed a facile and cost-effective method to synthesize two heterostructured photocatalysts representative of two main families of novel structures proposed, hybrids of TiO2 with metal (Au) and semiconductor (CeO2) nanomaterials. The photocatalysts have been extensively characterized to ensure a good comparability in terms of co-catalyst doping characteristics, morphology and surface area. The photocatalytic degradation of ciprofloxacin and sulfamethoxazole as target pollutants, two antibiotics of high concern polluting water sources, has been evaluated and CeO2/TiO2 exhibited the highest activity, achieving complete antibiotic degradation at very low photocatalyst concentrations. Our study provides new insights into the development of inexpensive heterostructured photocatalysts and suggests that the non-stoichiometry and characteristic d and f electronic orbital configuration of CeO2 have a significantly improved role in the enhancement of the photocatalytic reaction.

Efficient photocatalytic degradation of ciprofloxacin by graphite felt-supported MnS/Polypyrrole composite: Dominant reactive species and reaction mechanisms

The accumulation of antibiotics in aquatic environments poses a serious threat to human health. Photocatalytic degradation is a promising method for removing antibiotics from water, but its practical implementation requires improvements in photocatalyst activity and recovery. Here, a novel graphite felt-supported MnS/Polypyrrole composite (MnS/PPy/GF) was constructed to achieve effective adsorption of antibiotics, stable loading of photocatalyst, and rapid separation of spatial charge. Systematic characterization of composition, structure and photoelectric properties indicated the efficient light absorption, charge separation and migration of the MnS/PPy/GF, which achieved 86.2% removal of antibiotic ciprofloxacin (CFX), higher than that of MnS/GF (73.7%) and PPy/GF (34.8%). The charge transfer-generated 1O2, energy transfer-generated 1O2, and photogenerated h+ were identified as the dominant reactive species, which mainly attacked the piperazine ring in the photodegradation of CFX by MnS/PPy/GF. The •OH was confirmed to participate in the defluorination of CFX via hydroxylation substitution. The MnS/PPy/GF-based photocatalytic process could ultimately achieve the mineralization of CFX. The facile recyclability, robust stability, and excellent adaptability to actual aquatic environments further confirmed MnS/PPy/GF is a promising eco-friendly photocatalyst for antibiotic pollution control.

Photocatalytic degradation of four emerging antibiotic contaminants and toxicity assessment in wastewater: A comprehensive study

Excessive usage and unrestricted discharge of antibiotics in the environment lead to their accumulation in the ecosystem due to their highly stable and non-biodegradation nature. Photodegradation of four most consumed antibiotics such as amoxicillin, azithromycin, cefixime, and ciprofloxacin were studied using Cu2O-TiO2 nanotubes. Cytotoxicity evaluation of the native and transformed products was conducted on the RAW 264.7 cell lines. Photocatalyst loading (0.1-2.0 g/L), pH (5, 7 and 9), initial antibiotic load (50-1000 μg/mL) and cuprous oxide percentage (5, 10 and 20) were optimized for efficient photodegradation of antibiotics. Quenching experiments to evaluate the mechanism of photodegradation with hydroxyl and superoxide radicals were found the most reactive species of the selected antibiotics. Complete degradation of selected antibiotics was achieved in 90 min with 1.5 g/L of 10% Cu2O-TiO2 nanotubes with initial antibiotic concentration (100 μg/mL) at neutral pH of water matrix. The photocatalyst showed high chemical stability and reusability up to five consecutive cycles. Zeta potential studies confirms the high stability and activity of 10% C-TAC (Cuprous oxide doped Titanium dioxide nanotubes for Applied Catalysis) in the tested pH conditions. Photoluminescence and Electrochemical Impedance Spectroscopy data speculates that 10% C-TAC photocatalyst have efficient photoexcitation in the visible light for photodegradation of antibiotics samples. Inhibitory concentration (IC50) interpretation from the toxicity analysis of native antibiotics concluded that ciprofloxacin was the most toxic antibiotic among the selected antibiotics. Cytotoxicity percentage of transformed products showed r: -0.985, p: 0.01 (negative correlation) with the degradation percentage revealing the efficient degradation of selected antibiotics with no toxic by-products.

Materials Based on Co, Cu, and Cr as Activators of PMS for Degrading a Representative Antibiotic-The Strategy for Utilization in Water Treatment and Warnings on Metal Leaching

A chromate of copper and cobalt (Φy) was synthesized and characterized. Φy activated peroxymonosulfate (PMS) to degrade ciprofloxacin (CIP) in water. The Φy/PMS combination showed a high degrading capability toward CIP (~100% elimination in 15 min). However, Φy leached cobalt (1.6 mg L^-1), limiting its use for water treatment. To avoid leaching, Φy was calcinated, forming a mixed metal oxide (MMO). In the combination of MMO/PMS, no metals leached, the CIP adsorption was low (<20%), and the action of SO₄•^- dominated, leading to a synergistic effect on pollutant elimination (>95% after 15 min of treatment). MMO/PMS promoted the opening and oxidation of the piperazyl ring, plus the hydroxylation of the quinolone moiety on CIP, which potentially decreased the biological activity. After three reuse cycles, the MMO still presented with a high activation of PMS toward CIP degradation (90% in 15 min of action). Additionally, the CIP degradation by the MMO/PMS system in simulated hospital wastewater was close to that obtained in distilled water. This work provides relevant information on the stability of Co-, Cu-, and Cr-based materials under interaction with PMS and the strategies to obtain a proper catalyst to degrade CIP.

Metal Oxide Nanostructures (MONs) as Photocatalysts for Ciprofloxacin Degradation

In recent years, organic pollutants have become a global problem due to their negative impact on human health and the environment. Photocatalysis is one of the most promising methods for the removal of organic pollutants from wastewater, and oxide semiconductor materials have proven to be among the best in this regard. This paper presents the evolution of the development of metal oxide nanostructures (MONs) as photocatalysts for ciprofloxacin degradation. It begins with an overview of the role of these materials in photocatalysis; then, it discusses methods of obtaining them. Then, a detailed review of the most important oxide semiconductors (ZnO, TiO₂, CuO, etc.) and alternatives for improving their photocatalytic performance is provided. Finally, a study of the degradation of ciprofloxacin in the presence of oxide semiconductor materials and the main factors affecting photocatalytic degradation is carried out. It is well known that antibiotics (in this case, ciprofloxacin) are toxic and non-biodegradable, which can pose a threat to the environment and human health. Antibiotic residues have several negative impacts, including antibiotic resistance and disruption of photosynthetic processes.

Integrated adsorption and photocatalytic degradation based removal of ciprofloxacin and sulfamethoxazole antibiotics using Fc@rGO-ZnO nanocomposite in aqueous systems

Ferrocene functionalized rGO-ZnO nanocomposite was synthesized via the facile hydrothermal method. ZnO was reduced over the 3-dimensional rGO framework (3D-Fc@rGO) using Camellia sinensis extract. The Fc@rGO-ZnO nanocomposite was employed for pharmaceutical degradation (sulfamethoxazole (SMX) and ciprofloxacin (CIP)) in an aqueous solution under UV C light. The physicochemical properties of the as-prepared photocatalyst were characterized using FTIR, XRD, FESEM, EDS mapping, HR-TEM, XPS, and DR-UV Vis. The as-synthesized Fc@rGO-ZnO photocatalyst performed remarkably against pristine ZnO, with a fivefold increase in removal efficiency. This superior activity was attributed to its improved light harvesting, charge carrier interface, and enhanced charge separation. Additionally, the photocatalyst obeyed the Lagergen model for pseudo-first-order kinetics. Congruously, the integrated approach of Fc@rGO and ZnO as oxidizing agents was proficient in removing >95% of antibiotics (CIP and SMX) within 180 min. Furthermore, the heterostructure configuration developed between Fc@rGO and ZnO helps in charge migration and generation of abundant •OH and •O₂^- radicals for photodegradation activities. The toxicity assessment of the treated solutions showed improved cell viability in the algal strains of Scenedesmus and Chlorella sp. Moreover, this novel approach for the synthesis of a photoactive nanocomposite is found to be low-cost and reusable for three cycles. The nanocomposite is environmentally sustainable paving the way for practical applications in the treatment of different classes of antibiotics.

Twisty C-TiO2 /PCN S-Scheme Heterojunction with Enhanced n→π * Electronic Excitation for Promoted Piezo-Photocatalytic Effect

Herein, a twisty C-TiO₂ /PCN (CNT) Step-scheme (S-scheme) heterojunction is fabricated and applied to degrade ciprofloxacin (CIP) with the assistance of ultrasonic vibration and visible light irradiation. The nitrogen-rich twisty polymeric carbon nitride (PCN) can not only induce a non-centrosymmetric structure with enhanced polarity for a better piezoelectric effect but also provide abundant lone pair electrons to promote n→π* transition during photocatalysis. Its hybridization with C-TiO₂ particles can construct S-scheme heterojunction in CNT. During the piezo-photocatalysis, the strain-induced polarization electric field in the heterojunction can regulate the electron migration between the two components, resulting in a more effective CIP degradation. With the synergistic effect of ultrasonic vibration and visible light irradiation, the reaction rate constant of CIP degradation by CNT increases to 0.0517 min^-1 , which is 1.86 times that of photocatalysis and 6.46 times that of ultrasound. This system exhibits a stable CIP decomposition efficiency under the interference of various environmental factors. In addition, the in-depth investigation found that three pathways and 12 major intermediates with reduced toxicity are produced after the reaction. Hopefully, the construction of this twisty CNT S-scheme heterojunction with enhanced piezo-photocatalytic effect offers inspiration for the design of environmentally functional materials.

A comprehensive review on quinolone contamination in environments: current research progress

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.

Methods involved in the treatment of four representative pharmaceuticals in hospital wastewater using sonochemical and biological processes

A primary pollution source by pharmaceuticals is hospital wastewater (HWW). Herein, the methods involved in the action of a biological system (BS, aerobic activated sludge) or a sonochemical treatment (US, 375 kHz and 30.8 W), for degrading four relevant pharmaceuticals (azithromycin, ciprofloxacin, paracetamol, and valsartan) in HWW, are shown. Before treatment of HWW, the correct performance of BS was assessed using glucose as a reference substance, monitoring oxygen consumption, and organic carbon removal. Meanwhile, for US, a preliminary test using ciprofloxacin in distilled water was carried out. The determination of risk quotients (RQ) and theoretical analyses about reactive moieties on these target substances are also presented. For both, the degradation of the pharmaceuticals and the calculation of RQ, analyses were performed by LC-MS/MS. The BS action decreased the concentration of paracetamol and valsartan by ∼96 and 86%, respectively. However, a poor action on azithromycin (2% removal) was found, whereas ciprofloxacin concentration increased ∼20%; leading to an RQ value of 1.61 (high risk) for the pharmaceuticals mixture. The analyses using a biodegradation pathway predictor (EAWAG-BDD methodology) revealed that the amide group on paracetamol and alkyl moieties on valsartan could experience aerobic biotransformations. In turn, US action decreased the concentration of the four pharmaceuticals (removals > 60% for azithromycin, ciprofloxacin, and paracetamol), diminishing the environmental risk (RQ: 0.51 for the target pharmaceuticals mixture). Atomic charge analyses (based on the electronegativity equalization method) were performed, showing that the amino-sugar on azithromycin; piperazyl ring, and double bond close to the two carbonyls on ciprofloxacin, acetamide group on paracetamol, and the alkyl moieties bonded to the amide group of valsartan are the most susceptible moieties to attacks by sonogenerated radicals. The LC-MS/MS analytical methodology, RQ calculations, and theoretical analyses allowed for determining the degrading performance of BS and US toward the target pollutants in HWW.•Biological and sonochemical treatments as useful methods for degrading 4 representative pharmaceuticals are presented.•Sonochemical treatment had higher degrading action than the biological one on the target pharmaceuticals.•Methodologies for risk environmental calculation and identification of moieties on the pharmaceuticals susceptible to radical attacks are shown.

Incorporation of Ag-doped ZnO nanorod through Graphite hybridization: Effective approach for degradation of Ciprofloxacin

To remove the Ciprofloxacin (CIP) from aqueous solution, ZnO-Ag-Gp nanocomposite exhibited efficient photocatalytic properties. The biopersistent CIP is pervasive in surface water and also hazardous to human and animal health. This study utilized the hydrothermal technique to prepare Ag-doped ZnO hybridizing Graphite (Gp) sheet (ZnO-Ag-Gp) to degrade pharmaceuticals pollutant CIP from an aqueous medium. The structural and chemical compositions of the photocatalysts were determined by XRD, FTIR and XPS analysis. FESEM and TEM images revealed the nanorod ZnO with round shape Ag distributed on a Gp surface. The reduced bandgap of the ZnO-Ag-Gp sample enhanced the photocatalytic property which was measured by using UV-vis Spectroscopy. Dose optimization study found that 1.2 g/L is optimum for single (ZnO) and binary (ZnO-Gp and ZnO-Ag), where 0.3 g/L ternary (ZnO-Ag-Gp) exhibited maximum degradation efficiency (98%) within 60 min for 5 mg/L CIP. Pseudo 1st order reaction kinetics rate was found highest for ZnO-Ag-Gp (0.05983 min^-1) and it decreased to 0.03428 min^-1 for annealed sample. Removal efficiency decreased to only 90.97% at 5th run and hydroxyl radicals played a vital role to degrade CIP from aqueous solution. UV/ZnO-Ag-Gp will be a promising technique to degrade wide-ranging pharmaceutical antibiotics from the aquatic medium.

Bacterial cellulose flakes loaded with Bi2MoO6 nanoparticles and quantum dots for the photodegradation of antibiotic and dye pollutants

Effective strategies to improve charge separation in semiconductor particles are critical for improving the photodegradation of organic pollutants at levels sufficient for environmental applications. Herein, Bi₂MoO₆ (BMO_MOF), comprising both nanoparticles (NPs) and quantum dots (QDs), was synthesized from a bismuth-based metal-organic framework (Bi-MOF) precursor. Surface defects on BMO_MOF, the combination of NPs and QDs, and modified energy band edges improved photogenerated charge separation and facilitated redox reactions. When compared to BMO derived from uncoordinated Bi, the BMO_MOF photocatalyst (PC) was more efficient at photodegrading tetracycline hydrochloride (TCH) and ciprofloxacin (CIP), two widely-used antibiotics ubiquitous in wastewater, as well as the carcinogenic pollutant rhodamine B (RhB). BMO_MOF was then loaded on the biopolymer bacterial cellulose (BC) to further enhance photocatalytic performance and facilitate the recovery of the PC after water treatment processes. The novel BMO_MOF/BC photocatalytic flakes were significantly larger than pure BMO_MOF, and thus easier to recuperate. Furthermore, anchoring BMO_MOF on BC flakes augmented significantly the photodegradation of TCH, CIP, and RhB, mainly because hydroxyl groups in BC act as hole traps facilitating photogenerated electron-hole separation. Results obtained with BMO_MOF/BC highlight promising approaches to develop optimal PCs for aqueous pollutants degradation.

A Bioavailability Model to Predict the Impact of pH and Dissolved Organic Carbon on Ciprofloxacin Ecotoxicity to the Cyanobacterium Microcystis aeruginosa

Ciprofloxacin (CIP) is a pseudopersistent antibiotic detected in freshwater worldwide. As an ionizable chemical, its fate in freshwater is influenced by water chemistry factors such as pH, hardness, and dissolved organic carbon (DOC) content. We investigated the effect of pH, DOC, and Ca²⁺ levels on the toxicity of CIP to Microcystis aeruginosa and developed a bioavailability model on the basis of these experimental results. We found that the zwitterion (CIP^+/- ) is the most bioavailable species of CIP to M. aeruginosa, whereas DOC is the most dominant factor reducing CIP toxicity, possibly via binding of both CIP^+/- and CIP⁺ to DOC. pH likely also regulates CIP-DOC binding indirectly through its influence on CIP speciation. In addition, higher tolerance to CIP by M. aeruginosa was observed at pH < 7.2, but the underlying mechanism is yet unclear. Calcium was identified as an insignificant factor in CIP bioavailability. When parameterized with the data obtained from toxicity experiments, our bioavailability model is able to provide accurate predictions of CIP toxicity because the observed and predicted total median effective concentrations deviated by <28% from each other. Our model predicts that changes in pH and DOC conditions can affect CIP toxicity by up to 10-fold, suggesting that CIP in many natural environments is likely less toxic than in standard laboratory toxicity experiments. Environ Toxicol Chem 2022;41:2835-2847. © 2022 SETAC.

Visible-Light-Driven Photocatalytic Degradation of Tetracycline Using Heterostructured Cu2O-TiO2 Nanotubes, Kinetics, and Toxicity Evaluation of Degraded Products on Cell Lines

This study first reports on the tetracycline photodegradation with the synthesized heterostructured titanium oxide nanotubes coupled with cuprous oxide photocatalyst. The large surface area and more active sites on TiO₂ nanotubes with a reduced band gap (coupling of Cu₂O) provide faster photodegradation of tetracycline under visible light conditions. Cytotoxicity experiments performed on the RAW 264.7 (mouse macrophage) and THP-1 (human monocytes) cell lines of tetracycline and the photodegraded products of tetracycline as well as quenching experiments were also performed. The effects of different parameters like pH, photocatalyst loading concentration, cuprous oxide concentration, and tetracycline load on the photodegradation rate were investigated. With an enhanced surface area of nanotubes and a reduced band gap of 2.58 eV, 1.5 g/L concentration of 10% C-TAC showed the highest efficiency of visible-light-driven photodegradation (∼100% photodegradation rate in 60 min) of tetracycline at pH 5, 7, and 9. The photodegradation efficiency is not depleted up to five consecutive batch cycles. Quenching experiments confirmed that superoxide radicals and hydroxyl radicals are the most involved reactive species in the photodegradation of tetracycline, while valance band electrons are the least involved reactive species. The cytotoxicity percentage of tetracycline and its degraded products on RAW 264.7 (-0.932) as well as THP-1 (-0.931) showed a negative correlation with the degradation percentage with a p-value of 0.01. The toxicity-free effluent of photodegradation suggests the application of the synthesized photocatalyst in wastewater treatment.

Nb/N Co-Doped Layered Perovskite Sr2TiO4: Preparation and Enhanced Photocatalytic Degradation Tetracycline under Visible Light

Sr2TiO4 is a promising photocatalyst for antibiotic degradation in wastewater. The photocatalytic performance of pristine Sr2TiO4 is limited to its wide bandgap, especially under visible light. Doping is an effective strategy to enhance photocatalytic performance. In this work, Nb/N co-doped layered perovskite Sr2TiO4 (Sr2TiO4:N,Nb) with varying percentages (0−5 at%) of Nb were synthesized by sol-gel and calcination. Nb/N co-doping slightly expanded the unit cell of Sr2TiO4. Their photocatalytic performance towards antibiotic (tetracycline) was studied under visible light (λ > 420 nm). When Nb/(Nb + Ti) was 2 at%, Sr2TiO4:N,Nb(2%) shows optimal photocatalytic performance with the 99% degradation after 60 min visible light irradiation, which is higher than pristine Sr2TiO4 (40%). The enhancement in photocatalytic performance is attributed to improving light absorption, and photo-generated charges separation derived from Nb/N co-doping. Sr2TiO4:N,Nb(2%) shows good stability after five cycles photocatalytic degradation reaction. The capture experiments confirm that superoxide radical is the leading active species during the photocatalytic degradation process. Therefore, the Nb/N co-doping in this work could be used as an efficient strategy for perovskite-type semiconductor to realize visible light driving for wastewater treatment.

Solar-light driven photodegradation of antimicrobials, their transformation by-products and antibiotic resistance determinants in treated wastewater

This study aimed to assess the possibility of using solar light-driven photolysis and TiO₂-based photocatalysis to remove (1) antibiotic residues, (2) their transformation products (TPs), (3) antibiotic resistance determinants, and (4) genes identifying the indicator bacteria in a treated wastewater (secondary effluent). 16 antimicrobials belonging to the different classes and 45 their transformation by-products were selected for the study. The most susceptible to photochemical decomposition was tetracycline, which was completely removed in the photocatalysis process and in more than 80% in the solar light-driven photolysis. 83.8% removal (on average) was observed using photolysis and 89.9% using photocatalysis in the case of the tested genes, among which the genes sul1, uidA, and intI1 showed the highest degree of removal by both methods. The study revealed that applied methods promisingly remove the tested antibiotics, their TPs and genes even in such a complex matrix including treated wastewater and photocatalysis process had a higher removal efficiency of antibiotics, TPs and genes tested. Moreover, the high percentage removal of the intI1 gene (>93%) indicates the possibilities of use of the solar light-driven photolysis and TiO₂-based photocatalysis in minimizing the antibiotic resistance genes transfer by mobile genetic elements.

Insight into the degradation of ciprofloxacin by medium-pressure UV-activated monochloramine process

The degradation efficiency and mechanisms of ciprofloxacin (CIP), a typical antibiotic, by a medium-pressure ultraviolet/chloramine (MPUV/NH₂Cl) treatment were investigated. The results showed that CIP degradation by MPUV/NH₂Cl was significantly higher than that by NH₂Cl oxidation and MPUV photolysis, and that this degradation processes were consistent with pseudo-first-order kinetics. The initial CIP concentration (7.5-30.2 μM) and the presence of HCO₃^- (0.5-10 mM) significantly inhibited CIP degradation with k_obs,CIP 0.0090-0.0069 and 0.0078-0.0048 cm²/mJ. In contrast, NO₃^- (50-500 μM) and Br^- (0.5-10 mM) significantly promoted the degradation with k_obs,CIP 0.0078-0.0102 and 0.0078-0.0124 cm²/mJ. The effect of Cl^- (0.5-10 mM) and natural organic matter (1-5 mg/L) were negligible. The NH₂Cl dosage (30-60 μM) presented a dual effect, in which its increase within the optimal concentration range (30-40 μM) accelerated CIP degradation due to the formation of reactive radicals, whereas an excessive increase (40-60 μM) quenched the free radicals, ultimately quenching the free radicals and inhibiting the degradation. The optimum pH for CIP degradation under MPUV/NH₂Cl treatment was 7.0. The contribution of reactive halogen species (i.e., reactive chlorine species and reactive nitrogen species) to CIP degradation was substantially greater than that of hydroxyl radicals under acidic or neutral conditions. We identified the degradation products of CIP and proposed degradation pathways, which included defluorination and cracking of the piperazine ring, with the latter being dominant. Compared to haloacetic acid (HAA) and nitrogenous disinfection byproducts (N-DBPs), MPUV/NH₂Cl significantly reduced trihalomethane (THM) production and theoretical cytotoxicity by 80.1% and 78.4% respectively, compared to the background experiment in natural water at a UV dose of 300 mJ/cm².

In silico toxicity evaluation for transformation products of antimicrobials, from aqueous photolysis degradation

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.

Preparation of a Heterogeneous Catalyst CuO-Fe2O3/CTS-ATP and Degradation of Methylene Blue and Ciprofloxacin

A heterogeneous particle catalyst (CuO-Fe2O3/CTS-ATP) was synthesized via injection molding and ultrasonic immersion method, which is fast and effective. The particle catalyst applied attapulgite (ATP) wrapped by chitosan (CTS) as support, which was loaded dual metal oxides CuO and Fe2O3 as active components. After a series of characterizations of catalysts, it was found that CuO and Fe2O3 were successfully and evenly loaded on the surface of the CTS-ATP support. The catalyst was used to degrade methylene blue (MB) and ciprofloxacin (CIP), and the experimental results showed that the degradation ratios of MB and CIP can reach 99.29% and 86.2%, respectively, in the optimal conditions. The degradation mechanism of as-prepared catalyst was analyzed according to its synthesis process and ∙OH production, and the double-cycle catalytic mechanism was proposed. The intermediate products of MB and CIP degradation were also identified by HPLC-MS, and the possible degradation pathways were put forward.

High Photocatalytic Activity of g-C3N4/La-N-TiO2 Composite with Nanoscale Heterojunctions for Degradation of Ciprofloxacin

Ciprofloxacin (CIP) in natural waters has been taken as a serious pollutant because of its hazardous biological and ecotoxicological effects. Here, a 3D nanocomposite photocatalyst g-C₃N₄/La-N-TiO₂ (CN/La-N-TiO₂) was successfully synthesized by a simple and reproducible in-situ synthetic method. The obtained composite was characterized by XRD, SEM, BET, TEM, mapping, IR, and UV-vis spectra. The photocatalytic degradation of ciprofloxacin was investigated by using CN/La-N-TiO₂ nanocomposite. The main influential factors such as pH of the solution, initial CIP concentration, catalyst dosage, and coexisting ions were investigated in detail. The fastest degradation of CIP occurred at a pH of about 6.5, and CIP (5 mg/L starting concentration) was completely degraded in about 60 min after exposure to the simulated solar light. The removal rates were rarely affected by Na⁺ (10 mg·L⁻¹), Ca²⁺ (10 mg·L⁻¹), Mg²⁺ (10 mg·L⁻¹), and urea (5 mg·L⁻¹), but decreased in the presence of NO₃⁻ (10 mg·L⁻¹). The findings indicate that CN/La-N-TiO₂ nanocomposite is a green and promising photocatalyst for large-scale applications and would be a candidate for the removal of the emerging antibiotics present in the water environment.

Photodegradation of norfloxacin in ice: Role of the fluorine substituent

Ice is an important medium in cold regions, because it regulates the environmental behaviors and the fate of pollutants. The photodegradation of fluoroquinolone (FQ) antibiotics as emerging contaminants of concern in ice remains poorly understood. Here, the photodegradation of fluorine-containing norfloxacin (NOR) as one model of FQs in ice formed from freezing solutions was investigated. Pipemidic acid (PPA) as a structural analogue of NOR was selected to compare the effect of molecular structure on the antibiotic photodegradation in the ice. Results suggested that the photodegradation rate constant of NOR in ice relative to pure water increased by 40.0%. Both the absorbance in the absorption spectra and quantum yields of NOR in ice over water increased by 1.4 times. Direct photodegradation mainly caused the defluorination of NOR, which was more important than cleavage and oxidation of the piperazine ring by self-sensitized photooxidation in ice. The defluorination rate of NOR in the ice relative to water increased by about 12.7%. The fluorine substituent played a more important role in the NOR photodegradation in the ice, resulting in a 1.6-fold increase in the photodegradation rate constant of NOR relative to PPA. This work provides a new insight into the role of fluorine substituents in the photodegradation of fluorinated pharmaceuticals in cold regions.

Fe-N-C catalyst with Fe-NX sites anchored nano carboncubes derived from Fe-Zn-MOFs activate peroxymonosulfate for high-effective degradation of ciprofloxacin: Thermal activation and catalytic mechanism

Developing high-efficient catalysts is crucial for activating peroxymonosulfate (PMS). Fe-N-C catalysts exhibit excellent performance for PMS activation because of the contribution of doped N, Fe-Nx and Fe₃C sites. In our work, a series of Fe-N-C catalysts with high-performance was obtained by pyrolyzing Fe-Zn-MOFs precursors. During pyrolysis process, the change of chemical bonds and formation of active sites in the precursor were elucidated by characterization analysis and related catalytic experiments. Graphitic N, Fe-Nx and Fe₃C were confirmed to activate PMS synergistically for ciprofloxacin (CIP) degradation. Besides, the catalytic performance was proportional to the amount of doped iron and calcination temperature. Moreover, the Fe-N-C-3-800/PMS system not only displayed good recycling performance, but also had high anti-interference ability. Integrated with quenching and electron paramagnetic resonance (EPR) experiments, a non-radical pathway dominated by ¹O₂ was proposed. Furthermore, PMS could bond to Fe-N-C-3-800 to form intermediate for charge transfer, thus accelerate electron transfer between CIP and PMS to realize degradation of CIP. Six main pathways of CIP degradation were proposed, which include bond fission of N-C on piperazine ring and direct oxidation of CIP. This study provided a new idea for the design of heterogeneous carbon catalysts in advanced oxidation field.

ZnO-CdO nanocomposites incorporated with graphene oxide nanosheets for efficient photocatalytic degradation of bisphenol A, thymol blue and ciprofloxacin

The widespread existence of different organic contaminants mostly phenolic compounds, organic dyes and antibiotics in water bodies initiated by the various industrial wastes that raised great scientific concern and public awareness as well recently owing to their prospective capability to spread these contaminants resistant gene and pose hazard to human. In the present study, a series of nanostructured ZnO-CdO incorporated with reduced graphene oxide (ZCG nanocomposites) were successfully synthesized by a simple refluxing method and characterized by using the X-ray diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, photoluminescence spectroscopy, field emission-scanning microscope (FE-SEM) and UV-visible diffused reflectance spectroscopy (DRS) for the photocatalytic degradation of bisphenol A (BPA), thymol blue (ThB) and ciprofloxacin (CFn) with illumination of UV light. The maximum degradation and mineralization of BPA, ThB and CFn was achieved around 98.5%, 98.38% and 99.28% over the ZCG-5 nanocomposite photocatalyst after UV light irradiation for 180 min, 120 min and 75 min, respectively. The superior photocatalytic activity of ZCG-5 ascribed to enhance adsorption capacity, effective separation of charge carriers consequential for the production of more ROS after incorporation of RGO nanosheets with ZnO-CdO in photocatalyst. The conceivable photocatalytic degradation mechanism of BPA, ThB and CFn was elucidated through ROS identification and the assessment of photocatalyst stability by reusability, EEO (kwh/m³order) and UV light dose (mJ/cm²) were evaluated. The plausible photocatalytic degradation pathways were proposed for the degradation of BPA, ThB and CFn via GC-MS analysis. The present work investigates the efficient removal of BPA, ThB and CFn using ZCG nanocomposites as photocatalyst.

Transformation Products of Emerging Pollutants Explored Using Non-Target Screening: Perspective in the Transformation Pathway and Toxicity Mechanism—A Review

The scientific community has increasingly focused on forming transformation products (TPs) from environmental organic pollutants. However, there is still a lot of discussion over how these TPs are generated and how harmful they are to living terrestrial or aquatic organisms. Potential transformation pathways, TP toxicity, and their mechanisms require more investigation. Non-target screening (NTS) via high-resolution mass spectrometry (HRMS) in model organisms to identify TPs and the formation mechanism on various organisms is the focus of this review. Furthermore, uptake, accumulation process, and potential toxicity with their detrimental consequences are summarized in various organisms. Finally, challenges and future research initiatives, such as performing NTS in a model organism, characterizing and quantifying TPs, and evaluating future toxicity studies on TPs, are also included in this review.

Performance of TiO2/UV-LED-Based Processes for Degradation of Pharmaceuticals: Effect of Matrix Composition and Process Variables

Ultra-violet light-emitting diode (UV-LED)-based processes for water treatment have shown the potential to surpass the hurdles that prevent the adoption of photocatalysis at a large scale due to UV-LEDs' unique features and design flexibility. In this work, the degradation of five EU Watch List 2020/1161 pharmaceutical compounds was comprehensively investigated. Initially, the UV-A and UV-C photolytic and photocatalytic degradation of individual compounds and their mixtures were explored. A design of experiments (DoE) approach was used to quantify the effects of numerous variables on the compounds' degradation rate constant, total organic carbon abatement, and toxicity. The reaction mechanisms of UV-A photocatalysis were investigated by adding different radical scavengers to the mix. The influence of the initial pH was tested and a second DoE helped evaluate the impact of matrix constituents on degradation rates during UV-A photocatalysis. The results showed that each compound had widely different responses to each treatment/scenario, meaning that the optimized design will depend on matrix composition, target pollutant reactivity, and required effluent standards. Each situation should be analyzed individually with care. The levels of the electrical energy per order are still unfeasible for practical applications, but LEDs of lower wavelengths (UV-C) are now approaching UV-A performance levels.

Influence of chemical speciation on enrofloxacin degradation by UV irradiation: Kinetics, mechanism and disinfection by-products formation

Fluoroquinolones (FQs) were frequently detected in aqueous environment. The UV irradiation have been reported as an efficient method for FQs degradation. This study investigated the influence of chemical speciation on enrofloxacin (ENR) photolysis process by UV irradiation. The results showed that chemical speciation of ENR significantly affected the photodegradation kinetics, and the highest degradation rate was observed in the zwitterion form. Presence of natural organic matter (NOM) and inorganic anions had different degrees of influences on ENR photodegradation for three chemical speciation of ENR. The contribution of ¹O₂ on ENR degradation in neutral and alkalinity condition was significantly higher than that in acidic condition. The cation and zwitterion of ENR was beneficial to the formation of trichloromethane (TCM) and haloacetonitrile (HAN) during the chlorination alone. Compared with the chlorination of ENR, the UV pretreatment respectively caused 4.06-fold and 3.14-fold decrease in TCM formation at acidic and neutral reaction condition during subsequent chlorination. Also the decrease in HAN formation at neutral and alkalinity condition was found after UV treatment followed by chlorination. The UV pretreatment caused higher yield of HAN in the subsequent chlorination at acidic condition than that at neutral and alkalinity condition. Through the UV pretreatment at neutral condition, the generated concentration of halonitromethane (HNM) reached the maximum value during the subsequent chlorination. Potential toxic risk analysis showed the toxicity decreased in zwitterion form of ENR, while toxicity increased in cationic and anionic form after UV irradiation pretreatment.

Degradation of Ciprofloxacin by Titanium Dioxide (TiO2) Nanoparticles: Optimization of Conditions, Toxicity, and Degradation Pathway

The popular use of ciprofloxacin is often irrational, so it causes environmental pollution such as resistance. The solution to overcome environmental pollution due to ciprofloxacin is degradation by using TiO2 nanoparticles. TiO2 nanoparticles performance is influenced by environment such as light source, pH solvent, duration of lighting and TiO2 nanoparticles mass. The residual levels determination of ciprofloxacin was carried out by using a UV-Vis spectrophotometer. Toxicity test of ciprofloxacin degradation products with TiO2 nanoparticles used Escherichia coli bacteria. Liquid Chromatography Mass Spectrometry (LCMS) was used to determine the type of ciprofloxacin degradation product with TiO2 nanoparticles. The optimum condition for the ciprofloxacin degradation with TiO2 nanoparticles is lighting for 5 hours by using a white mercury UV lamp and 50 mg TiO2 nanoparticles with pH solvent of 5.5. The toxicity of ciprofloxacin degradation product with TiO2 nanoparticles was low. The smallest degradation product identified with m/z was p-fluoraniline (m/z 111). Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Construction of direct Z-scheme Bi5O7I/UiO-66-NH2 heterojunction photocatalysts for enhanced degradation of ciprofloxacin: Mechanism insight, pathway analysis and toxicity evaluation

Direct Z-scheme Bi₅O₇I/UiO-66-NH₂ (denoted as BU-x) heterojunction photocatalysts were successfully constructed through ball-milling method. Photocatalytic activities of the as-prepared BU-x samples were determined by using a typical fluoroquinolone antibiotic, ciprofloxacin (CIP). All BU-x heterojunctions exhibited better CIP removal performances than that of pristine Bi₅O₇I and UiO-66-NH₂ upon exposure to white light irradiation. In comparison, the heterojunction with UiO-66-NH₂ content of 50 wt% (BU-5) showed excellent structural stability and the optimal adsorption-photodegradation efficiency for the CIP removal. The removal efficiency of CIP (10 mg/L) over BU-5 (0.75 g/L) achieved 96.1% within 120 min illumination. Meanwhile, the effect of photocatalyst dosage, pH and inorganic anions were systemically explored. Reactive species trapping experiments, electron spin resonance (ESR) signals, Mott-Schottky measurements and density functional theory (DFT) simulation revealed that the photo-generated holes (h⁺), hydroxyl radical (·OH) and superoxide radical (·O₂^-) played crucial roles in CIP degradation. This result can be ascribed to that the unique Z-scheme charge transfer configuration retained the excellent redox capacities of Bi₅O₇I and UiO-66-NH₂. Meanwhile, the CIP degradation pathways and the toxicity of various intermediates were subsequently analyzed. This work provided a feasible idea for removing antibiotics by bismuth-rich bismuth oxyhalide/MOF-based heterostructured photocatalysts.

Degradation and transformation of norfloxacin in medium-pressure ultraviolet/peracetic acid process: An investigation of the role of pH

Given that fluoroquinolone antibiotics (FQs) are frequently detected in aquatic environments, there is an urgent need for the development of efficient water treatment technologies for their removal. Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have increasingly attracted attention as promising technologies for water decontamination in this regard. In this study, a novel PAA-based AOP (the medium-pressure ultraviolet (MPUV)/PAA process) was employed to degrade norfloxacin (NOR), which is an extensively applied FQ that is widely present in water. Mechanistic and kinetic aspects of the role of pH on this NOR degradation process were investigated. The results obtained showed that the MPUV/PAA process could effectively degrade NOR (pH = 5-9), and the degradation efficiency was significantly enhanced at pH 7 and 9 compared with that at pH 5. This observation could be attributed to the effect of pH on the ionic forms of NOR and the generation of reactive oxygen species (ROS). Further, the rate of PAA photolysis, which resulted in the formation of reactive radicals, increased with pH, as evidenced by the observed increase in the molar absorption coefficient of PAA (ε_PAA). Electron paramagnetic resonance (EPR) tests also indicated that the generation of ROS was significantly enhanced when the pH increased from 5 to 7, and at pH 9, a large amount of •OH were possibly consumed by PAA to form organic radicals, leading to a decrease in the •OH signal. Furthermore, it was observed that •OH is primarily responsible for NOR degradation in the MPUV/PAA process at pH 5, whereas organic radicals were primarily responsible for the degradation at pH 7 and 9. The identification of the transformation products (TPs) led to the observation of different NOR transformation pathways owing to the MPUV/PAA process under different pH conditions. Overall, this study provides a comprehensive understanding of the role of pH on the MPUV/PAA degradation behavior of FQs.

Application of TiO2-Based Photocatalysts to Antibiotics Degradation: Cases of Sulfamethoxazole, Trimethoprim and Ciprofloxacin

The extensive application of antibiotics in human and veterinary medicine has led to their widespread occurrence in a natural aquatic environment. Global health crisis is associated with the fast development of antimicrobial resistance, as more and more infectious diseases cannot be treated more than once. Sulfamethoxazole, trimethoprim and ciprofloxacin are the most commonly detected antibiotics in water systems worldwide. The persistent and toxic nature of these antibiotics makes their elimination by conventional treatment methods at wastewater treatment plants almost impossible. The application of advanced oxidation processes and heterogeneous photocatalysis over TiO2-based materials is a promising solution. This highly efficient technology has the potential to be sustainable, cost-efficient and energy-efficient. A comprehensive review on the application of various TiO2-based photocatalysts for the degradation of sulfamethoxazole, trimethoprim and ciprofloxacin is focused on highlighting their photocatalytic performance under various reaction conditions (different amounts of pollutant and photocatalyst, pH, light source, reaction media, presence of inorganic ions, natural organic matter, oxidants). Mineralization efficiency and ecotoxicity of final products have been also considered. Further research needs have been presented based on the literature findings. Among them, design and development of highly efficient under sunlight, stable, recyclable and cost-effective TiO2-based materials; usage of real wastewaters for photocatalytic tests; and compulsory assessment of products ecotoxicity are the most important research tasks in order to meet requirements for industrial application.

Enhanced activated persulfate oxidation of ciprofloxacin using a low-grade titanium ore under sunlight: influence of the irradiation source on its transformation products

In this work, the activated persulfate oxidation of ciprofloxacin (CIP) using a low-grade titanium ore under sunlight or simulated sunlight were conducted to analyze the CIP degradation efficiency and to identify the transformation products (TPs) generated during oxidation under both types of irradiation sources by using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). All advance oxidation process experiments were performed in a 2700-mL raceway reactor at a pH value of ~ 6.5 and an initial CIP concentration of 1 mg/L, during 90 min of reaction time. The control experiments carried out under simulated sunlight achieved a 97.7 ± 0.6% degradation efficiency, using 385 W/m² of irradiation with an average temperature increase of 11.7 ± 0.6 °C. While, the experiments under sunlight reached a 91.2 ± 1.3% degradation efficiency, under an average irradiation value of 19.2 ± 0.3 W/m² in October-November 2019 at hours between 11:00 am and 3:00 pm with an average temperature increase of 1.4 ± 0.8 °C. Mass spectrometry results indicated that 14 of the 108 possible TPs reported in the literature were detected. The calculated exact mass, measured accurate mass, and its characteristic diagnostic fragment ions were listed, and two new TPs were tentative identified. The TP generation analysis showed that some specific compounds were detected in different time intervals with kinetic variations depending on the irradiation used. Consequently, two CIP degradation pathways were proposed, since the type of irradiation determines the CIP degradation mechanism. Graphical abstract.

Insights into the Mechanism of the Bi/BiVO4 Composites for Improved Photocatalytic Activity

The increasing concentration of residual ciprofloxacin (CIP) can cause potential harm to the environment. Photocatalysis has been regarded as an effective method for the degradation of CIP. Bi/BiVO4 with excellent photocatalytic performance was synthesized partial reduction with NaBH4. The structure, morphology, composition, and optical performance of BiVO4 and Bi/BiVO4 were characterized by a variety of techniques. The results showed that the Bi/BiVO4 exhibits high photocatalytic activity in the degradation of CIP. Comparison of BiVO4 and Bi/BiVO4 has lower photoluminescence intensity and higher photocurrent responses intensity. The introduction of Bi made Bi/BiVO4 have a higher charge separation efficiency and generate more active free radicals. In addition, the radical trapping experiments revealed that superoxide free radicals and holes were the main active free radicals during the degradation of CIP. The pathway of CIP degradation was investigated through high performance liquid chromatography-mass spectrometry, and a possible degradation mechanism was proposed.