Visible-light-driven photocatalytic degradation of tetracycline hydrochloride by Z-scheme Ag3PO4/1T@2H-MoS2 heterojunction: Degradation mechanism, toxicity assessment, and potential applications

Low concentration of peroxymonosulfate coupled with visible light triggers oxygen reactive species generation over constructed Bi25FeO40/BiOCl Z-scheme heterojunction for various tetracycline antibiotics removal

Photocatalytic peroxymonosulfate (PMS) oxidation systems demonstrate significant potential and promising prospects through the interconnection of photocatalytic and PMS oxidation for simultaneously achieving efficient pollutant removal and reduction of PMS dosage, which prevents resource wastage and secondary pollution. In this study, a Z-scheme Bi25FeO40/BiOCl (BOFC) heterojunction was constructed to carry out the photocatalytic PMS oxidation process for tetracyclines (TCs) pollutants at low PMS concentrations (0.08 mM). The photocatalytic PMS oxidation rate of Bi25FeO40/BiOCl composites for tetracycline hydrochloride (TCH), chlortetracycline (CTC), oxytetracycline (OTC) and doxycycline (DXC) reaches 86.6%, 83.6%, 86.7%, and 88.0% within 120 min. Simultaneously, the BOFC/PMS system under visible light (Vis) equally displayed the practical application prospects for the solo and mixed simulated TCs antibiotics wastewater. Based on the electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) valence band spectrum, a Z-scheme electron migration pathway was proposed to elucidate the mechanism underlying the performance enhancement of BOFC composites. Bi25FeO40 in BOFC composites can serve as active site for activating PMS by the formation of Fe3+/Fe2+ cycle. Toxicity estimation software tool (T.E.S.T.) and mung beans planting experiment demonstrates that BOFC/PMS/Vis system can reduce toxicity of TCs wastewater. Therefore, BOFC/PMS/Vis system achieves efficient examination in different water environments and efficient utilization of PMS, which displays a scientific reference for achieving environmentally-friendly and resource-saving handling processes.

MoS2-based nanocomposites and aerogels for antibiotic pollutants removal from wastewater by photocatalytic degradation process: A review

Photocatalytic technologies based on molybdenum disulfide (MoS2) catalysts are effective, eco-friendly, and promising for antibiotic pollutants treatment. The technologies used by MoS2-based nanocomposites and aerogels for efficient degradation of antibiotics are reviewed in detail for the first time in this paper. The fundamental aspects of MoS2 were comprehensively scrutinized, encompassing crystal structure, optical properties, and photocatalytic principle. Then, the main synthesized methods and advantages/disadvantages for the preparation of MoS2-based nanocomposites and aerogels were systematically presented. Besides, a comprehensive overview of diverse MoS2-based nanocomposites and aerogels photo-degradation systems that enhanced the degradation of antibiotic pollutants were revealed. Meanwhile, the photo-degradation mechanism concentrated on the photoelectron transfer pathways and reactive oxygen species (ROS) were systematically evaluated. Finally, the challenges and perspectives for deeply development of MoS2-based nanocomposites and aerogels were discussed. This review may help researchers to deeply understand the research status of MoS2-based nanocomposites and aerogels for antibiotics removal, and makes clear the photo-degradation mechanism from photoelectron transfer pathways and ROS aspects of MoS2-based nanocomposites and aerogels.

Zinc-Doped BiOBr Hollow Microspheres for Enhanced Visible Light Photocatalytic Degradation of Antibiotic Residues

Photocatalysis represents an effective technology for environmental remediation. Herein, a series of Zn-doped BiOBr hollow microspheres are synthesized via one-pot solvothermal treatment of bismuth nitrate and dodecyl ammonium bromide in ethylene glycol along with a calculated amount of zinc acetate. Whereas the materials morphology and crystal structure remain virtually unchanged upon Zn-doping, the photocatalytic performance toward the degradation of ciprofloxacin is significantly improved under visible light irradiation. This is due to the formation of a unique band structure that facilitates the separation of photogenerated electron-hole pairs, reduced electron-transfer resistance, and enhanced electron mobility and carrier concentration. The best sample consists of a Zn doping amount of 1%, which leads to a 99.2% degradation rate of ciprofloxacin under visible photoirradiation for 30 min. The resulting photocatalysts also exhibit good stability and reusability, and the degradation intermediates exhibit reduced cytotoxicity compared to ciprofloxacin. These results highlight the unique potential of BiOBr-based photocatalysts for environmental remediation.

Construction of p-n-p nano heterojunction through coupling La2O3, (BiO)2CO3 and Ag3PO4 for effective photocatalytic degradation of doxycycline: Insights into mechanism, pathway and intermediate toxicity evaluation

The present work is centred around the development of La2O3/(BiO)2CO3/Ag3PO4 (LBA), a p-n-p nano-heterojunction to photodegrade doxycycline under visible light irradiation. Here, ultrasonication assisted co-precipitation method was employed to synthesize the photocatalyst. The photocatalyst was characterized using different analysis such as SEM, TEM, elemental mapping, XRD, XPS, FTIR, Raman, BET, DRS, PL and EIS which confirmed the successful fabrication of LBA and their excellent ability to refrain the e-/h+ recombination owing to the construction of the heterojunction. LBA was found to degrade DOX by 91.75 % with the high mineralization of 87.23%. The impact of the reaction parameters influencing the photodegradation process including the concentration of the NCs and DOX, pH and the influence of the commonly present anions were studied. The stability and reusability of the LBA was assessed through subjecting it to four cycles of photodegradation of DOX. In addition, the recovered LBA was characterized through XPS and XRD analysis to confirm the particles stability and reusability. The active participation of the photogenerated charges and the reactive oxygen species were identified through the scavenging assay and ESR analysis. Further, GC-MS/MS analysis was performed to put forward a plausible photodegradation pathway. The toxicity of the end products as well as the intermediates was predicted through ECOSAR software.

Inactivation of antibiotic resistant bacteria by Fe3O4 @MoS2 activated persulfate and control of antibiotic resistance dissemination risk

Antibiotic resistance poses a global environmental challenge that jeopardizes human health and ecosystem stability. Antibiotic resistant bacteria (ARB) significantly promote the spreading and diffusion of antibiotic resistance. This study investigated the efficiency and mechanism of inactivating tetracycline-resistant Escherichia coli (TR E. coli) using Fe3O4 @MoS2 activated persulfate (Fe3O4 @MoS2/PS). Under optimized conditions (200 mg/L Fe3O4 @MoS2, 4 mM PS, 35 °C), TR E. coli (∼7.5 log CFU/mL) could be fully inactivated within 20 min. The primary reactive oxygen species (ROS) responsible for TR E. coli inactivation in the Fe3O4 @MoS2/PS system were hydroxyl radicals (•OH) and superoxide radicals (•O2-). Remarkably, the efflux pump protein was targeted and damaged by the generated ROS during the inactivation process, resulting in cell membrane rupture and efflux of cell content. Additionally, the horizontal transmission ability of residual antibiotic resistance genes (ARGs) harboring in the TR E. coli was also reduced after the inactivation treatment. This study offers an efficient approach for TR E. coli inactivation and substantial mitigation of antibiotic resistance dissemination risk.

Visible-light S-scheme heterojunction of copper bismuthate quantum dots decorated Titania-spindles for exceptional tetracycline degradation

The rational heterojunctions for antibiotics degradation have sparked significant attention in wastewater purification. In this study, we report a unique S-scheme photocatalytic system by in-situ growth of CuBi2O4 quantum dots (QDs) onto {101} facet of TiO2 spindles (TiO2-P) via hydrothermal transformation of Na-titanate nanotubes, which is observed by transmission electron microscopy technology. The CuBi2O4/TiO2-P effectively achieves photo-degradation of tetracycline (TC) using visible light (e.g. an 82% TC degradation efficiency at 60 min), which is attributed to the promotion of the charge separation and retaining strong redox capacity at the heterojunction interfaces via the active species of O2-, OH, and h+. Moreover, density functional theory (DFT) calculations show that a built-in electric field forms at the interface of the S-scheme heterojunction. In all, this work introduces a straightforward in-situ hydrothermal growth method to construct S-scheme photocatalysts for effective water treatment.

Degradation of norfloxacin by red mud-based prussian blue activating H2O2: A strategy for treating waste with waste

The massive accumulation of red mud (RM) and the abuse of antibiotics pose a threat to environment safety and human health. In this study, we synthesized RM-based Prussian blue (RM-PB) by acid solution-coprecipitation method to activate H2O2 to degrade norfloxacin, which reached about 90% degradation efficiency at pH 5 within 60 min and maintained excellent catalytic performance over a wide pH range (3-11). Due to better dispersion and unique pore properties, RM-PB exposed more active sites, thus the RM-PB/H2O2 system produced more reactive oxygen species. As a result, the removal rate of norfloxacin by RM-PB/H2O2 system was 8.58 times and 2.62 times of that by RM/H2O2 system and PB/H2O2 system, respectively. The reactive oxygen species (ROS) produced in the degradation process included ·OH, ·O2- and 1O2, with 1O2 playing a dominant role. The formation and transformation of these ROS was accompanied by the Fe(III)/Fe(II) cycle, which was conducive for the sustained production of ROS. The RM-PB/H2O2 system maintained a higher degradation efficiency after five cycles, and the material exhibited strong stability, with a low iron leaching concentration. Further research showed the degradation process was less affected by Cl-, SO42-, NO3-, and humic acids, but was inhibited by HCO3- and HPO42-. In addition, we also proposed the possible degradation pathway of norfloxacin. This work is expected to improve the resource utilization rate of RM and achieve treating waste with waste.

Heteroatom-modulated NiCo2O4 apparent energy activation of PMS for tetracycline removal: Mechanism and toxicity analysis

Heteroatom doping to reconfigure the electronic structure of heterogeneous catalysts is expected to lead to the development of advanced oxidation water purification materials with superior performance and greater stability. Herein, a series of catalysts with different elemental doping was developed by a simple and environmentally friendly one-step self-propagating combustion method to remove Tetracycline (TC). After S-doping, the normalized kinetic constant of TC was significantly increased from 30.49 to 159.41 min-1M-1 within 30 min, which is even higher than most recent heterogeneous catalysts. The prepared S-doped NiCo2O4 (NCO-S) exhibits an extremely promising catalytic performance for oxidation (92.8 %) and mineralization (65.9 %) of TC in a wide pH range (3-11). The resistance to interference is excellent for inorganic ions and even in real water samples. Quenching experiments, electron paramagnetic resonance (EPR), and electrochemical analyses demonstrated that the non-radical oxidation pathway, including electron transfer and 1O2, dominated the degradation process after S doping. It is speculated that possible intermediates and toxicological studies are discussed, finding that the overall degradation process is moving towards low toxicity to reveal prospects for large-scale applications. This work not only provides a way to remove TC, but may also inspire the design of more efficient and stable materials for water treatment and other applications.

Principle of CoS2/ZnIn2S4 heterostructure effect and its mechanism of action in a visible light-catalyzed antibacterial process

The development of visible-light-driven catalytic antimicrobial technology is a significant challenge. In this study, heterojunctions were constructed for the appropriate modification of semiconductor-based photocatalysts. A simple hydrothermal method was used for material reconstruction, and smaller CoS2 nanoparticles were deposited and in situ grown on two-dimensional nanoflower-like ZnIn2S4 carriers to form CoS2/ZnIn2S4 (CS/ZIS) Schottky heterojunctions. Systematic study via characterization techniques and density functional theory calculations indicated that the excellent photocatalytic activity of CS/ZIS stemmed from the solid interfacial coupling between the two solid-phase materials. These materials acted as co-catalysts to increase the number of active reaction sites, enhance charge transfer, drive unidirectional electron movement, and improve charge separation efficiency, which effectively facilitated the production of reactive oxygen species (ROS). The optimized CS/ZIS heterojunction exhibited excellent performance for the efficient photocatalytic degradation of organic matter and inactivation of Escherichia coli (E. coli) compared with the ZnIn2S4 photocatalyst. Moreover, the antibacterial mechanism of the heterojunction photocatalyst and the extent of damage to the cell membrane and internal cytoplasm were explored by performing various assays. It was demonstrated that superoxide radicals are the predominant active species and multiple ROS act together to cause oxidative stress damage and cell inactivation.

Highly porous BiOBr@NU-1000 Z-scheme heterojunctions for synergistic efficient adsorption and photocatalytic degradation of tetracycline

Designing an effective photoactive heterojunction having dual benefits towards photoenergy conversion and pollutant adsorption is regarded as an affordable, green method for eliminating tetracycline (TC) from wastewater. In this regard, a series of BiOBr@NU-1000 (BNU-X, X = 1, 2 and 3) heterojunction photocatalysts are constructed. BNU-X preserves the original skeleton structure of the parent NU-1000, and its high porosity and specific surface area enable superior TC adsorption. At the same time, BNU-X is an effective Z-scheme photocatalyst that improves light trapping, promotes photoelectron-hole separation, and shows excellent photocatalytic degradation efficiency towards TC with the value of the photodegradation kinetic rate constant k being 2.2 and 24.8 times those of NU-1000 and BiOBr, respectively. The significant increase in the photocatalytic activity is ascribed to the construction of an efficient Z-scheme photocatalyst, which promotes the formation of superoxide radicals (˙O2-) and singlet oxygen (1O2) as the main oxidative species in the oxidation system. This research has the advantage of possibilities for the development of porous Z-scheme photocatalysts based on photoactive MOF materials and inorganic semiconductors for the self-purification and photodegradation of organic contaminants.

Photocatalytic degradation performance of antibiotics by WO3/α-Fe2O3/zeolite type II heterojunction with core-shell structure

The accumulation of antibiotics in the environment can be harmful to human health, and research on their disposal technologies is of increasing interest. In this study, WO3/α-Fe2O3/zeolite (WFZ) type II heterojunction composites with core-shell structures were prepared by coupling WO3 semiconductors with visible-light photocatalytic activity with α-Fe2O3 via hydrothermal synthesis using zeolite as a carrier for the adsorption of synergistic photocatalytic degradation of antibiotics in wastewater. X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), specific surface, and porosity measurements were used to characterize the structure of WFZ type II heterojunction. The performance of WFZ heterojunction for the visible photocatalytic degradation of antibiotics (tetracycline hydrochloride (TCH), ciprofloxacin (CIP), and levofloxacin hydrochloride (LVF)) was investigated. Through four photocatalytic cycles, the catalyst exhibited excellent durability and stability. This was attributed to the core-shell structure and type II heterojunction promoting the effective separation of photogenerated carriers and the extended visible light response range, which resulted in the best photocatalytic activity of the catalyst under visible light irradiation. Radical trapping experiments showed that superoxide radicals (•O2-) and hydroxyl radical (•OH) were the main active species that played a major role in the photocatalytic degradation. These findings show that the synthesized WFZ type-II heterojunction can be used as a reliable visible-light-responsive photocatalyst for the treatment of antibiotics in wastewater.

Freezing degradation of the anticonvulsant oxcarbazepine by bromate in water ice under sunlight irradiation

Ice plays a crucial role in contaminant transformation in seasonally ice-covered waters. In this study, the characteristics and mechanisms of an emerging contaminant oxcarbazepine (OXC) degradation by a disinfection by-product bromate ( [Formula: see text] ) in ice were explored via combined experiments and theoretical calculations. Results showed that 74.0 % and 86.4 % of OXC was degraded by [Formula: see text] in ice after 140 min in dark and 120 min under solar irradiation, respectively, while the reaction was negligible in water. The oxidation-reduction potential of [Formula: see text] solution at 1000 μmol L-1 was 56.9 % higher than that at 50 μmol L-1. The oxidation-reduction potential of [Formula: see text] solution at pH 2 was 14.8 %-109.5 % higher than those at other pH values. Enhanced OXC degradation by [Formula: see text] in ice could be attributed to increased [Formula: see text] oxidation capacity resulting from locally elevated [Formula: see text] and H+ concentrations. Hypobromous acid (HOBr), •OH, and Br• generated by direct photolysis under solar irradiation further promoted the OXC degradation in ice. Br• formed by the direct photolysis of accumulated HOBr under solar irradiation caused the generation of bromine-containing degradation products. Bromine-containing degradation products possessed higher potential toxicities, which could contribute to increase the secondary pollution of water environment.