Photocatalytic Degradation Of Ciprofloxacin Research Articles

Photocatalytic antibiotic degradation in coated open microchannels by applying 2D and 3D flow modeling with kinetics

The accumulation of active pharmaceutical ingredients in the aqueous environment is a serious problem that will become even more concerning in the future. In this work, the photocatalytic degradation of ciprofloxacin (CIP) in aqueous solution was assessed over P25-TiO2 coated open microchannels with gravity-driven flow under UV-A irradiation. The deposition of different amounts of TiO2 in the microchannels was carried out via a facile, self-developed procedure. The degradation kinetics of ciprofloxacin was described via the Langmuir-Hinshelwood mechanism. Since the flow characteristics in the microchannel had influence on the concentration distribution of CIP in the microchannel, the coupled momentum and mass conservation law was solved numerically in MATLAB 2023a (2D case) as well as in ANYS Fluent 2023 R1 (2D and 3D cases). Although the implemented 2D model in MATLAB 2023a allowed the preliminary estimation of the selected kinetic parameters, namely adsorption equilibrium constant and specific Langmuir-Hinshelwood rate constant, the sensitivity of the model was not satisfactory which was attributed to the empirical correlations used for the estimation of the external mass transfer coefficient. The 2D and 3D models in ANSYS Fluent 2023 R1 predicted efficiently the outlet concentration of ciprofloxacin for different inlet CIP concentrations and liquid phase flow rates. Therefore, the as developed 2D and 3D models in ANSYS Fluent 2023 R1 can be used for the design of reactors containing coated microchannels with gravity-driven flow for photocatalytic degradation of active pharmaceutical ingredients.

Photocatalytic Degradation of Ciprofloxacin: A Combined Experimental and Theoretical Study Using Curcumin and Hydrogen Peroxide

Contamination of soil, water, and wastewater by pharmaceuticals, including antibiotics, is a global health problem. This work evaluated the use of a natural compound, curcumin (CUR), as a homogeneous photocatalyst, together with hydrogen peroxide (H2O2) as a benign oxidant, to promote the photodegradation of ciprofloxacin (CIP). Furthermore, we carried out theoretical calculations using density functional theory (DFT) to assess the chemical reactivity of ciprofloxacin. In addition, the intermolecular interaction patterns of two crystalline polymorphs of the antibiotic drug were analyzed through Hirshfeld surfaces. Finally, calculations using the TD-DFT formalism were carried out to understand the effects on the CIP molecule caused by the simultaneous presence of the CUR molecule and ultraviolet-visible light (UV-Vis). A photooxidative effect was observed in the presence of the CUR photocatalyst (CIP + CUR (1:0.5)), resulting in a degradation of CIP of up to 24.4%. However, increasing the concentration of the CUR photocatalyst (ciprofloxacin + curcumin (1:1)) decreased the photodegradation of CIP, which may be caused by competition between the CIP molecule and CUR for ROS generated in situ. Additionally, the calculation results showed that the electronic excitations caused by the associated CIP + CUR structures affect the CIP molecule, resulting in the effects observed experimentally. The results show that CUR, when applied as a photosensitizing catalyst, presents synergistic potential with H2O2 in the photocatalytic degradation of ciprofloxacin. This photocatalytic process can be applied to the environmental remediation of pharmaceutical micropollutants, a subject of ongoing studies.

BiVO4/sulfur-doped g-C3N4 nanocomposite as photocatalyst for degradation of ciprofloxacin under visible light irradiation

In recent years, the use of antibiotics has greatly increased, which has caused environmental pollution. We offer a photocatalyst based on BiVO4/sulfur-doped g-C3N4 nanocomposite, which was made by a one-step thermal condensation method from thiourea and bismuth vanadate to degradate ciprofloxacin (CIP). The BiVO4/sulfur-doped g-C3N4 photocatalyst was analyzed by certain techniques including XRD, FTIR, BET, FESEM, EDX, TEM, DRS, photoluminesence, and Mott-Schottky to determine various physicochemical properties. The photocatalytic degradation of CIP, as a model pollutant, under visible LED light irradiation was tested to investigate the catalytic performance of nanocomposite. Response Surface Methodology (RSM) was employed to optimize operational parameters, including photocatalyst dosage (50–150 mg), CIP concentration (10–30 mg/L), initial pH of the solution (3–11), and irradiation time (12–120 min). The BiVO4/sulfur-doped g-C3N4 nanocomposite, with a narrow bandgap of 2.15 eV, exhibited exceptional photocatalytic performance in degrading CIP. The optimal conditions for CIP removal were photocatalyst dosage of 120.9 mg, CIP concentration of 10 mg/L, and initial solution pH of 3, resulting in 93.5 % removal efficiency after 105 min of irradiation. The photocatalytic degradation kinetics of CIP followed a pseudo-first-order model with a rate constant (K) of −0.0221 L/min, indicating rapid degradation process. The photocatalyst maintained excellent performance after 5 reuses, with only a 3 % reduction in efficiency. XRD analysis confirmed the structural stability of the nanocomposite after reuse.

Solvothermal preparation of CuO/g-C3N4 and photocatalytic degradation of ciprofloxacin

Composite materials CuO/g-C3N4 (CuOCN) were prepared using a solvothermal method to investigate their degradation effect on ciprofloxacin (CIP). The materials were characterized through X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectrophotometry (DRS), and X-ray photoelectron spectroscopy (XPS). The toxicity of degradation products of CIP was assessed through antibacterial experiments, and the degradation mechanism of CIP was investigated using quenching agent capture and high-performance liquid chromatography-mass spectrometry (HPLC-MS). The results of XRD and FTIR indicate that the CuOCN composite has been successfully synthesized. The photocatalytic experiment shows that adding 15% (w/w) of Cu3(BTC)2(H2O)3 in melamine (CuOCN2) has a relatively good degradation effect on CIP and can be reused multiple times. The TEM results indicate that both CuO and g-C3N4 have a layered structure and are attached together. HRTEM analysis reveals that the two components in CuOCN2 are arranged in a layered structure, with CuO displaying two crystal planes. Energy Dispersive Spectrometer (EDS) analysis reveals that the proportion of CuO in the three composite materials is 7.86% (w/w), 15.93% (w/w), and 84.83% (w/w), respectively. DRS detection reveals that the greater the amount of CuO added, the broader the visible light absorption range of the composite material, and the narrower the bandgap width. The photocurrent and photoresistance indicate that CuOCN2 exhibits a good photoelectric effect. XPS analysis shows that the CuOCN2 composite material possesses both the chemical composition and structure of CuO and g-C3N4. During the catalytic degradation process of CIP, four active substances, h+, e−, ·O2 −, and ·OH, were produced, leading to a reduction in the toxicity of the degradation products. Through HPLC-MS analysis, it was found that CIP undergoes reactions such as defluorination, ring opening of piperazine, and quinolone during degradation, resulting in reduced toxicity. This study provides an experimental basis for the degradation of CIP by CuOCN2.

Coupling Cu Coordination Polymers with CdS Forming an S-Scheme Heterojunction for Rapid Charge Separation and High Photocatalytic Activity.

Energy and the environment are significant impacting factors for the future development of humankind. In order to improve the corrosion resistance of CdS and decrease the recombination of photogenerated carriers, a novel Cu-CPs@CdS heterojunction with high efficiency mesopores was constructed by a simple hydrothermal method. The effective interfacial contact formation between nano-CdS and Cu-CPs promotes the transfer of photogenerated carriers while exhibiting a high spatial separation rate of charges. The photocatalytic performance of the heterojunction was evaluated by the photocatalytic degradation of organic pollutants and photocatalytic hydrogen generation. The photocatalytic degradation of ciprofloxacin (CIP) could reach 90.34%, and the hydrogen generation was high as 9227.82 μmol·g-1 under simulated sunlight irradiation. The boosted photocatalytic activity of Cu-CPs@CdS results from (i) the formation of coordination bonds, which not only enhanced the stability of heterojunctions but also provided a path for photogenerated carrier migration, (ii) integrating Cu-CPs, which provided more active sites, and (iii) the matched energy band structure between CdS and Cu-CPs that promoted speedy S-scheme interfacial charge-transfer pathways, culminating in efficient photogenerated charge separation and transfer. This research offered a fresh tactic to restrict photocorrosion and enhance the production of photocatalytic H2 over CdS-based catalysts.

Effects of TiO2 Nanoparticles Synthesized via Microwave Assistance on Adsorption and Photocatalytic Degradation of Ciprofloxacin.

In this study, the optimal microwave-assisted sol-gel synthesis parameters for achieving TiO2 nanoparticles with the highest specific surface area and photocatalytic activity were determined. Titanium isopropoxide was used as a precursor to prepare the sol (colloidal solution) of TiO2. Isopropanol was used as a solvent; acetylacetone was used as a complexation moderator; and nitric acid was used as a catalyst. Four samples of titanium dioxide were synthesized from the prepared colloidal solution in a microwave reactor at a temperature of 150 °C for 30 min and at a temperature of 200 °C for 10, 20, and 30 min. The phase composition of the TiO2 samples was determined by X-ray diffraction analysis (XRD) and Fourier-transform infrared spectroscopy (FTIR). Nitrogen adsorption/desorption isotherms were used to determine the specific surface area and pore size distributions using the Brunauer-Emmett-Teller (BET) method. The band-gap energy values of the TiO2 samples were determined by diffuse reflectance spectroscopy (DRS). The distribution of Ti and O in the TiO2 samples was determined by SEM-EDS analysis. The effects of adsorption and photocatalytic activity of the prepared TiO2 samples were evaluated by the degradation of ciprofloxacin (CIP) as an emerging organic pollutant (EOP) under UV-A light (365 nm). The results of the photocatalytic activity of the synthesized TiO2 nanoparticles were compared to the benchmark Degussa P25 TiO2. Kinetic parameters of adsorption and photocatalysis were determined and analyzed. It was found that crystalline TiO2 nanoparticles with the highest specific surface area, the lowest energy band gap, and the highest photocatalytic degradation were the samples synthesized at 200 °C for 10 min. The results indicate that CIP degradation by all TiO2 samples prepared at 200 °C show a synergistic effect of adsorption and photocatalytic degradation in the removal process.

Photocatalytic defluorination of ciprofloxacin by nitrogen-defected g-C3N4 under simulated sunlight: Mechanistic insight and pathway analysis

The photocatalytic degradation of ciprofloxacin (CIP) has been widely reported to be induced by ring cleavage and defluorination. However, the role of photo-generated reactive radicals, especially electrons, in defluorination remains controversial. This study investigates the effects of reactive radicals such as hydroxyl radicals (·OH) and electrons on CIP degradation and defluorination in photocatalytic processes by nitrogen-defected g-C3N4. Almost complete CIP degradation and 46.5 % defluorination were obtained under the best conditions tested. Scavenging tests, degradation intermediate product identification, and theoretical calculations were performed to explore the reaction routes driven by ·OH and electrons in depth. Scavenging tests revealed that ·OH and electrons were predominantly responsible for direct CIP defluorination, whereas electrons played an indirect role as critical intermediates for the formation of ·OH. Time-dependent intermediate evolution analysis demonstrated that CIP degradation mainly occurred by piperazine ring cleavage and defluorination. Density functional theory (DFT) calculations based on the Hirschfeld charge, Fukui index and electrostatic potential confirmed that zwitterionic CIP+- is more reactive than CIP+ and that the piperazine ring in CIP is susceptible to nucleophilic and radical attacks by ·O2– and ·OH. Finally, electron-assisted ·OH substitution and C-F bond cleavage were proposed as the main mechanisms for CIP defluorination. This study provides a thorough understanding of CIP defluorination mechanisms by nitrogen-defected g-C3N4-based photocatalysis.

Facile fabrication of CeO2/L-Bi2O2CO3 composite photocatalyst for removal of ciprofloxacin under visible light irradiation

The application of semiconductor photocatalytic technology to degrade antibiotics in water has been proved to be a promising technology CeO2/L-Bi2O2CO3 composite photocatalyst was efficiently prepared by a facile room temperature precipitation technique and employed in the photocatalytic degradation of ciprofloxacin (CIP). When the concentration of ciprofloxacin was 20 mg/L and the dosage of catalyst was 1.0 g/L, the degradation rate of CIP was 89.96 % after 120 min reaction with optimal catalyst. The addition of L-cysteine not only changed the crystallinity of Bi2O2CO3, but also broadened its visible light absorption range. Additionally, the combination of CeO2 and L-Bi2O2CO3 creates a heterojunction interface accelerates the electron transfer, thereby improving the photocatalytic activity. The degradation process was confirmed to involve the significant participation of O2– and h+ through free radical capture experiments. HPLC-MS analysis detected the intermediates of CIP degradation, leading to the proposition of two potential degradation pathways. Moreover, an electron transfer mechanism was suggested by analyzing the Mott-Schottky (M−S) curve and Taut-plot curves. This work provides new paradigm for the rational design of modified Bi2O2CO3-based photocatalysts and the treatment of contain CIP wastewater.

Hollow α-Bi2O3/TiO2 nanotube arrays hierarchical heterojunction with strong interface interaction for efficient photocatalytic ciprofloxacin degradation

Interfacial regulation for photocatalyst is considered as an effective strategy to enhance visible-light utilization and charges transfer. But it is still a great challenge for the conscious design of interfacial engineering. Herein, hollow α-Bi2O3/TiO2 nanotube arrays (α-Bi2O3/TNAs) hierarchical heterojunction was constructed to modulate the interface structure for efficient photocatalytic degradation of ciprofloxacin (CIP). The systematic characterization analysis, density functional theory (DFT) calculations and electron paramagnetic resonance spectra revealed that the Z-scheme charges transfer mechanism was affirmed between α-Bi2O3 and TNAs. The hierarchical tubular heterostructure was contributed to enhancing light absorption, and the strong interfacial interaction could promote the separation and transfer of photogenerated charges. The optimal α-Bi2O3/TNAs exhibited higher photocatalytic activity for CIP (73.9 %) than TNAs (25.3 %) under visible-light irradiation. The anions and natural organic matters could decline CIP removal owing to competing active sites or aggravating radicals consumption. The theoretical calculations further demonstrated that the staggered energy levels produced an internal electric field at heterojunction interface to promote charges transfer. Three degradation pathways of CIP were proposed based on DFT calculations and LC-MS. The photocatalytic degradation of CIP by α-Bi2O3/TNAs could effectively reduce its toxicity, and eventually alleviate the environmental hazards of antibiotics.

Ultraviolet Photodegradation of Ciprofloxacin Using Zinc Oxide and Iron-Doped Zinc Oxide (Fe-ZnO) Nanoparticles (NPs): Kinetic and Isotherm Measurements

This article describes the auto-combustion sol-gel synthesis of zinc oxide (ZnO), 0.1% iron-doped zinc oxide (0.1% Fe-ZnO), and 0.2% iron-doped zinc xide (0.2% Fe-ZnO) NPs with the goal of determining their suitability as a photocatalyst for the degradation of a hazardous antibiotic drug (ciprofloxacin). The functional group, surface morphology, and crystallinity of ZnO, 0.1% Fe-ZnO, and 0.2% Fe-ZnO NPs were studied using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and x-ray diffraction analysis (XRD). Various parameters, such as solution pH, catalyst dosage, light exposure period, and initial drug concentration, were optimized for quantitative degradation. The photocatalytic degradation of ciprofloxacin using ZnO, 0.1% Fe-ZnO, and 0.2% Fe-ZnO follows pseudo-first-order kinetics. The proposed method has been applied to commercial formulations such as Ciprofloxacinro, Ciprofloxacinro XR, and Ciprofloxacinro ProQuin XR with satisfactory results.

Photocatalytic degradation of ciprofloxacin from water with waste polystyrene and TiO2 composites

Ciprofloxacin (CIP) is one of the widely used antibiotics with a broad antimicrobial spectrum in the fluoroquinolone type. Its concentration in water bodies has increased over the years due to its frequent use. Since ciprofloxacin in the aquatic ecosystem adversely affects human health as well as other organisms, it must be removed from wastewater.The aim of this study was to develop Polystyrene (PS) and Titanium dioxide (TiO2) composites that can be used as catalysts in CIP removal by photocatalytic process. Waste PS (obtained from disposable cutlery) was used in the synthesis of these composites. In this study, PS-TiO2 composites with different PS content (C20, C50, C80; the numbers in the names indicate the PS percentage in the composite by weight) were synthesized. This is important in terms of the use of one waste in the removal of another waste.This process was optimized using Box-Behnken design, one of the response surface method. Parameters such as the amount of polymer in the composite, pH and initial CIP concentration were studied and their effects on CIP removal were found. The validity and adequacy of the selected model were evaluated according to the relevant statistical data. These are R2 = 0.9751, adjusted R2 = 0.9565, the model's p-value <0.05 and the lack of fit-value 0.246. Optimum conditions for CIP removal were obtained when the C50 was used, with a pH value of 3 and an initial CIP concentration of 5 mg/L.In the process carried out under these conditions, the CIP removal was found to be 95.01 % at the end of 180 min. This value was predicted as 94.37 % in the model. According to these results, C50 composite synthesized with waste PS can be used effectively for CIP removal.

Photocatalytic degradation of ciprofloxacin by Gd-Co/g-C3N4 under low-power light source: Degradation pathways and mechanistic insights

Ciprofloxacin hydrochloride (CIP) is remained in the natural environment. Photocatalysis is a promising technology for removing hard-to-degrade pollutants from water. For this purpose, we constructed a three-dimensional porous structure of graphitic-phase carbon nitride (3D g-C3N4) and doped rare earth element Gd and metal Co into 3D g-C3N4 to form a photocatalyst (Gd-Co/CN). We conducted photocatalytic experiments to evaluate its photocatalytic activity with CIP as the target pollutant. Experimental results showed that Gd-Co/CN had the best photocatalytic degradation of CIP under a 30 W LED lamp. The increase in photocatalytic activity is mainly attributed to the doping of Gd and Co expanding the specific surface area of 3D g-C3N4, and providing more reaction sites for photocatalytic reactions. Gd-Co/CN enhances O2 adsorption and activation and generates radicals (O2− and h+), allowing efficient degradation of CIP under low-power light sources. Furthermore, Gd-Co/CN also showed excellent stability and reusability in cycling experiments. This study explored the degradation pathways and mechanisms of CIP by using ultra-high-performance liquid chromatography and mass spectrometry (HPLC-MS) and density functional theory (DFT). It provides a more energy-efficient and environmentally friendly method for the treatment of antibiotic wastewater.

In situ heterojunction growth of CdS‐Bi2MoO6 microspheres for highly efficient photocatalytic degradation of Ciprofloxacin under visible light

AbstractIn‐situ synthesis was utilized to create a novel CdS‐Bi2MoO6 microspheres heterojunction photocatalyst for the degradation of Ciprofloxacin (CIP). Under visible light irradiation (&gt; 420 nm), the prepared samples demonstrated effective photocatalytic activity, the highest CIP degradation rate can reach 87 % within 60 minutes. The apparent kinetic rate constant (0.0503 min−1) is 2.9 and 5.4 times greater than that of pure CdS (0.0173 min−1) and Bi2MoO6 (0.00929 min−1), respectively. XRD, FT‐IR, Raman, SEM, TEM, HRTEM, XPS, EIS, PL, and other techniques have been applied to analyze the composition and structure of the catalyst. Furthermore, various active substance capture experiments and EPR spectra were used to examine the potential photocatalytic mechanisms. ⋅ O2− and h+ have been proven to be the most active substances in the photocatalytic degradation of CIP. The prepared samples have excellent stability, and the photodegradation system positively impacts toxicity reduction. The effective treatment of antimicrobial wastewater is a possible use for the catalyst.

Photocatalytic degradation of ciprofloxacin by using tannin-doped BaTiO3 catalyst

The aim of this study is to highlight the significance of ciprofloxacin degradation, a commonly used antibiotic in healthcare and agriculture, by synthesizing tannin-doped BaTiO3 (T-Ba) photocatalysts at various tannin amounts (0–50 wt%) and investigating their photocatalytic activity under both UV-A light and visible light irradiation. The impact of several parameters, including the initial concentration of ciprofloxacin, photocatalyst dosage, initial solution pH, and scavengers effect, on the photocatalytic activity was explored. The photocatalysts were characterized by FTIR, SEM, XRD, XPS, TEM, BET, PL and UV-DRS analysis. In the conducted studies, it was observed that the highest efficiency was achieved at 96 % under appropriate parameters. The kinetic study was conducted based on the Langmuir-Hinshelwood equations. According to stability tests, ciprofloxacin degradation was found as 92 % after the second cycle, while it was 50 % after the fifth cycle.

Photocatalytic degradation of ciprofloxacin using a novel carbohydrate-based nanocomposite from aqueous solutions

Pharmaceutical substances in the ecosystem pose a notable hazard to human and aquatic organism well-being. The occurrence of ciprofloxacin (CIP) within water sources or the food chain can perturb plant biochemical processes and induce drug resistance in both humans and animals. Therefore, effective removal is imperative prior to environmental discharge. This study introduces a Novel Carbohydrate-Based Nanocomposite (Fe3O4/MOF/AmCs-Alg) as a proficient photocatalytic agent for degrading CIP in aqueous solutions. The fabricated nanocomposite underwent characterization using FTIR, XRD, FESEM, DRS, and VSM techniques. The analyses conducted verified the successful synthesis of the Fe3O4/MOF/AmCs-Alg nanocomposite. Utilizing the optimized parameters (pH = 5, nanocomposite dose = 0.4 g/L, CIP concentration = 10 mg/L, light intensity = 75 mW/cm2, and a duration of 45min), the Fe3O4/MOF/AmCs-Alg/Vis nanocomposite demonstrated an impressive CIP degradation efficiency of 95.85%. Under optimal experiment conditions, CIP removal efficiency in tap water and treated wastewater samples was 91.27% and 76.78%, respectively. Furthermore, the total organic carbon (TOC) analysis indicated a mineralization rate of 51.21% for CIP. Trapping studies demonstrated that the superoxide radical (O2°−) had a notable contribution to the breakdown of CIP. In summary, the Fe3O4/MOF/AmCs-Alg/Vis system offers numerous benefits, encompassing effective degradation capabilities, effortless catalyst retrieval, and remarkable nanocomposite reusability.

Lamellar WO3/AgI S-scheme heterojunction for superior visible light driven photocatalytic degradation of ciprofloxacin

A unique lamellar WO3/AgI S-scheme heterojunction is constructed via integrated hydrothermal and coprecipitation methods. Optimized WO3/AgI composite shows significantly enhanced photocatalytic ciprofloxacin (CIP) degradation under visible light irradiation, achieving a removal rate of 53.4 % within 3 h, which is about 7.63 and 1.56 times superior than those of pristine WO3 and AgI, respectively. The characterizations, experiment results and Density Functional Theoretical (DFT) calculation results confirm the enhanced light absorption, well-aligned straddling band structures and reasonable formation of S-scheme heterojunction with efficient photogenerated carriers transfer between WO3 and AgI. Moreover, O2− and h+ are identified as the main active species, with O2− plays a dominant role in WO3/AgI during the photocatalytic degradation of CIP. This work elucidates a possible approach to develop photocatalysts with a high antibiotic removal efficiency through a higher reducing ability and stronger oxidizing ability of S-scheme heterojunction by reasonable structure configuration.

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.

Highly conductive Ti3C2 MXene reinforced g-C3N4 heterojunction photocatalytic for the degradation of ciprofloxacin: Mechanism insight

The extensive use of ciprofloxacin (CIP) poses a great threat to aquatic ecosystem, due to its potentially serious inhibitory effect on the microbial activity and low natural degradation rate. Photocatalytic degradation has emerged as a feasible method for treating CIP pollution. In this study, Ti3C2 reinforced g-C3N4 heterojunction material (MX/CN) was prepared using solvent drying method. The heterojunction composite accelerated the electron transfer rate, and the resulting MX/CN exhibited superior photocatalytic activity against CIP under visible light driving. The MX/CN sample achieved higher CIP photocatalytic removal rate of 97.8 %, 1.23 times higher than CN. Moreover, 6 %-MX/CN showed the best photocatalytic activity at pH = 7 when the initial concentration of CIP was 10 mg/L. Under neutral condition, the presence of Cl−, NO3−, and HCO3− reduced the degradation of CIP, where the addition of HCO3– caused a competed redox reaction with •OH in the system, resulting in a reduction of the CIP degradation efficiency to 30.9 %. The photocatalytic mechanism involving MX/CN was proposed according to the trapping experiments of active species, which confirmed that •O2− was the primary active component in photocatalytic degradation of CIP and h+ and •OH also played significant roles. Finally, cycling experiments using MX/CN showed that the CIP degradation efficiency maintained more than 90 % after five cycles.

Construction of Z-scheme heterojunction TiO2-ZnO@Oxygen-doped gC3N4 composite for enhancing H2O2 photoproduction and removal of pharmaceutical pollutants under visible light

In this study, the heterojunction photocatalyst of titanium dioxide-zinc oxide@oxygen-doped graphitic carbon nitride (TiO2-ZnO@OCN (TZ@OCN)) was synthesized using a simple and cost-effective hydrothermal self-assembly process. Characterization of the fabricated materials revealed that the incorporation of TiO2 and ZnO as inherent semiconductors along with the oxygen doping has effectively broadened the absorption spectrum of gC3N4, which can promote the electron generation and provide more active sites for O2 and H+ adsorption. It is noteworthy that the mentioned structure modification resulted in a superior H2O2 production rate among gC3N4-based photocatalysts with up to 3.11 mM.g−1 under visible light irradiation. Moreover, a valence band shifting from 1.57 to 2.91 eV upon doping oxygen atoms also elucidated the participation of active species in the photocatalytic degradation of ciprofloxacin (99.7 %, k = 0.030 min−1) and tetracyline (94.6 %, k = 0.017 min−1), in which superoxide radicals (•O2−) were shown to play a major role in removing the antibiotic. Besides, a Z-scheme heterojunction mechanism is additionally suggested, demonstrating the effectiveness of electron-hole pair splitting in the oxidation of antibiotics. Conclusively, the results show a novel and feasible modification pathway to enhance the photocatalytic activities of gC3N4 and other advanced semiconductor catalysts, especially for eliminating antibiotics and generating H2O2 within aqueous media.

Diurnal-independent, visible-light-storing of Ag2O@SrAl2O4:Eu2+,Dy3+ for the round-the-clock decomposition of ciprofloxacin

A round-the-clock photocatalyst that can efficiently separate charge carriers will break through the practical application of photocatalytic-based advanced oxidation processes (PC-AOPs) in wastewater treatment. In this work, an energy-storable p-n heterojunction Ag2O@SrAl2O4:Eu2+,Dy3+ (Ag2O@SAED) was successfully prepared to achieve round-the-clock photocatalytic degradation of ciprofloxacin (CIP). Ag2O@SAED can efficiently degrade ∼ 80 % of CIP (with ∼ 56 % mineralization) under low power consumption of 12 W LED visible light source radiation for 2 h. In addition, surprisingly, Ag2O@SAED also shows certain energy storage properties, so that it can effectively reduce the energy consumption of the treatment process compared with conventional photocatalytic processes. Non-radical singlet oxygen (1O2) is the main reactive species, which is produced mainly from intermediate superoxide radicals (·O2−). Moreover, the site of CIP attacked by 1O2 was tentatively confirmed by Fukui index based on density functional theory (DFT) calculations. The activities of round-the-clock degradation of CIP in different water matrices were examined. The degradation efficiency in tap water, Yangtze River and wastewater plant effluent were 61.88 %, 57.61 % and 55.87 %, respectively. The synergistic effect of p-n heterojunctions is effective in degrading CIP during daytime, and the light released from SAED activates the activity of Ag2O to degrade CIP at night. This study contributes to further understanding the principles and mechanisms of round-the-clock photocatalysts for degradation of organic pollutants and provides directions for the practical application of photocatalytic technology.