Adsorptional photocatalytic mineralization of oxytetracycline and ampicillin antibiotics using Bi2O3/BiOCl supported on graphene sand composite and chitosan

Fabrication of Ag-doped BiOF-reduced graphene oxide composites for photocatalytic elimination of organic dyes

Bismuth oxyfluoride (BiOF) is an emerging class of material with notable chemical stability, unique layered structure and striking energy band structure. Bi-based semiconductor materials and reduced graphene oxides (rGOs) have attracted considerable attention due to their broad spectrum of potential applications. Herein, we successfully synthesised an efficient photocatalyst comprising BiOF-rGO nanocomposites with embedded Ag nanoparticles using a simple hydrothermal method. The synthesised nanocomposites were characterised through Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy and ultraviolet (UV)-visible spectroscopy. The XRD results indicated the crystalline structures of the BiOF, Ag-doped BiOF and Ag-doped BiOF-rGO composites. Photocatalytic activity assessments focused on the degradation of methylene blue (MB) and methyl orange (MO) dyes under UV-light and sunlight irradiation. The Ag-doped BiOF-rGO composite exhibited significantly enhanced degradation efficiency, achieving 61.81 % and 74.25 % degradation of MB and MO, respectively, after 300 min under UV-light irradiation. On the contrary, pure BiOF demonstrated only 17.63 % and 48.29 % degradation for MB and MO, respectively, under similar conditions. Furthermore, under sunlight irradiation, the Ag-doped BiOF-rGO composite exhibited an MB removal efficiency of 43.87 % after 300 min, whereas pure BiOF showed only 27.47 % under identical conditions. These results underscore the potential of Ag-doped BiOF-rGO composites as highly efficient and adaptable photocatalysts for the photodegradation of organic dyes in industrial wastewater.

Photocatalytic activity enhancement of nanostructured metal-oxides photocatalyst: a review

Nanostructured metal oxide semiconductors have emerged as promising nanoscale photocatalysts due to their excellent photosensitivity, chemical stability, non-toxicity, and biocompatibility. Enhancing the photocatalytic activity of metal oxide is critical in improving their efficiency in radical ion production upon optical exposure for various applications. Therefore, this review paper provides an in-depth analysis of the photocatalytic activity of nanostructured metal oxides, including the photocatalytic mechanism, factors affecting the photocatalytic efficiency, and approaches taken to boost the photocatalytic performance through structure or material modifications. This paper also highlights an overview of the recent applications and discusses the recent advancement of ZnO-based nanocomposite as a promising photocatalytic material for environmental remediation, energy conversion, and biomedical applications.

Synthesis of hydroxyethylcellulose phthalate-modified silver nanoparticles and their multifunctional applications as an efficient antibacterial, photocatalytic and mercury-selective sensing agent

Water contamination by several aquatic pollutants such as dyes, heavy metal ions and microbes is a prevalent concern to health and environment. Thus, developing facile, economical, and eco-friendly strategies to tackle this problem have become paramount. Hence, this study reports the synthesis of hydroxyethylcellulose phthalate-capped silver nanoparticles (HEC-PA@AgNPs) using a simple sunlight-assisted route. The multifunctional applications of the synthesized particles as an efficient nanoprobe for the selective sensing of Hg2+ as well as their photocatalytic and antimicrobial activities were demonstrated. HEC-PA@AgNPs were systematically characterized by various advanced analytical techniques such as FTIR, UV-Vis spectroscopy, X-ray diffraction (XRD), zeta potential (ZP) and dynamic light scattering (DLS). The successful functionalization of AgNPs with HEC-PA was manifested using FTIR. SEM and XRD revealed the formation of spherical AgNPs with a face centered cubic structure and a crystallite size of 14 nm. The particles demonstrated a hydrodynamic size of 40 nm with a good colloidal stability as evidenced from the ZP value of -35 mV, suggesting the effective role of the negatively charged HEC-PA capping agent in stabilizing the NPs. HEC-PA@AgNPs exhibited fast naked-eye colorimetric detection, high selectivity, and sensitivity to Hg2+ in spiked real water samples over a wide range of pH (3-9) and temperatures (298-328 K), achieving a detection limit of 119 nM. The presence of other diverse metal ions didn't affect the specificity of the particles toward Hg ions. Further, the sensing mechanism is based on a characteristic redox reaction between Hg2+ and AgNPs. Further, HEC-PA@AgNPs showcased a more noxious antimicrobial activity to gram-positive bacteria (B. subtilis and S. aureus) than gram-negative bacteria (E. coli). Besides, AgNPs exhibited high photocatalytic potential under sunlight irradiation with a degradation efficiency of 79 % for methylene blue dye in only 80 min following pseudo-1st order kinetics with a rate constant of 0.019 min-1. The photocatalyst exhibited good reusability after five recycling runs. These results render our approach promising multifunctional analytical probe for environmental and biomedical applications.

Fabrication of multiphase MoSe2 modified BiOCl nanosheets for efficient piezo-photoelectric hydrogen evolution and antibiotic degradation

Efficient spatial charge separation plays a crucial role in improving the photocatalytic performance. Therefore, 1T/2H MoSe2/BiOCl (1T/2H MS/BOC) and 2H MoSe2/BiOCl (2H MS/BOC) piezo-photocatalysts are synthesized. By combining piezoelectric catalysis and photocatalysis, a highly active piezo-photocatalytic process is realized. The optimal 1T/2H MS/BOC piezo-photocatalyst displays superior diclofenac (DCF) degradation and hydrogen (H2) evolution activity under the combined action of ultrasound and light. In particular, the DCF degradation kinetic constant (k) of optimal 0.5% 1T/2H MS/BOC under the synergistic effect of ultrasound and light is 0.057 min-1, which is 8.1 and 6.3 times higher than those of BiOCl (0.007 min-1) and 0.5% 2H MS/BOC (0.009 min-1). Moreover, the H2 evolution rate of 0.5% 1T/2H MS/BOC is 122.5 μmol g-1 h-1, which is also higher than those of BiOCl (45.8 μmol g-1 h-1) and 2H MS/BOC (49.5 μmol g-1 h-1). The dramatic improvement in the DCF degradation and H2 evolution piezo-photocatalytic performance of 1T/2H MS/BOC catalysts is ascribed to the built-in polarization electric field and abundance of active sites of 1T/2H MS/BOC as well as the advantageous band structure between BiOCl and 1T/2H MoSe2. Additionally, three probable degradation pathways of DCF were put forward from the results of liquid chromatography-mass spectrometry (LCMS) and density functional theory (DFT) calculations. This study provides the design strategy of high efficiency piezo-photocatalysts in environmental purification and energy-generation fields based on phase and band structure engineering.

Photocatalytic degradation of reactive brilliant blue KN-R by Ti-doped Bi2O3

In this study, different compositions of Ti-doped Bi₂O₃ photocatalytic materials were prepared by chemical solution decomposition method. It was used to degrade reactive brilliant blue KN-R, and then characterized by XRD, SEM, UV-vis DRS, XPS, photocurrent, and other detection methods. The results show that when the catalyst dosage is 1.0 g/L and the initial concentration of reactive brilliant blue KN-R is 20 mg/L, the degradation rate of pure Bi₂O₃ to reactive brilliant blue KN-R is 75.30%; the Ti doping amount is 4% (4Ti/Bi₂O₃), 4Ti/Bi₂O₃ had the best degradation effect on reactive brilliant blue KN-R, and the degradation rate could reach 93.27%. When 4Ti/Bi₂O₃ was reused for 4 times, the degradation rate of reactive brilliant blue KN-R only decreased by 6.91%. Doping Ti can inhibit the growth of Bi₂O₃ grains, making the XRD peak of Ti/Bi₂O₃ material wider. The pure Bi₂O₃ particles are larger and the surface is smooth. With the increase of Ti doping content, the surface of Ti/Bi₂O₃ material grows from roughness to nanofibrous Bi₄Ti₃O₁₂. The visible light absorption performance and electron separation and transfer ability of Bi₂O₃ are significantly improved by doping Ti ions. The band gap is reduced from 2.81 to 2.75 eV. In conclusion, doping Ti enhances the visible light absorption and electron separation and transfer capabilities of Bi₂O₃, reduces the band gap, and improves the surface morphology, which makes Bi₂O₃ have higher photocatalytic performance.

Calcination-Induced Oxygen Vacancies Enhancing the Photocatalytic Performance of a Recycled Bi2O3/BiOCl Heterojunction Nanosheet

With the rapid development of industry, bismuth-based semiconductors have been widely used for the photocatalytic degradation of organic contaminants discharged into wastewater. Herein, a Bi₂O₃/BiOCl (BBOC) heterojunction was constructed with high photocatalytic activity toward Rhodamine B (RhB) in the first cycle of the photocatalysis test, while the photocatalytic performance was drastically reduced after repeated testing. The adsorbed RhB molecules occupying the facial active sites of BBOC contributed to the decline of photocatalytic activity. The spent BBOC can be reactivated by the decomposition of the adsorbed RhB and the introduction of oxygen vacancies during calcination under an air atmosphere. The BBOC thus recovered exhibited a superior apparent rate constant of 0.08087 min^-1 compared with 0.05228 min^-1 of pristine BBOC. This study provided an effective strategy to investigate the deactivation/activation mechanism of bismuth-based heterojunction photocatalysts.

A review on bismuth-based nanocomposites for energy and environmental applications

Bismuth, a heavy metal which is found to be inexpensive and at a reduced cost, is utilized in the synthesis of different nanomaterials with novel structure, remarkable physical and chemical properties, adjustable bandgap, notable efficiency for photothermal conversion. These characteristics have made this element desirable for various applications such as storage and conversion of energy, electronics, sensors, photocatalysis, and other biomedical applications. These review papers are the vital points for the students, this report guides them to the research papers which focus on the impressive development in the area of bismuth and similar nanostructures. The purpose of the present review is to discuss the various synthesis routes of bismuth-based nanomaterials along with green synthesis, different nanostructures of bismuth, their significant properties, diverse applications and directions for the upcoming research. Therefore, with these different tuneable synthesis methods of bismuth-based nanomaterials combined with their novel properties, would elucidate on the future devices based on various nanostructures of bismuth.

Heterostructured α-Bi2O3/BiOCl Nanosheet for Photocatalytic Applications

Photocatalytic degradation of organic pollutants in wastewater is recognized as a promising technology. However, photocatalyst Bi₂O₃ responds to visible light and suffers from low quantum yield. In this study, the α-Bi₂O₃ was synthetized and used for removing Cl^- in acidic solutions to transform BiOCl. A heterostructured α-Bi₂O₃/BiOCl nanosheet can be fabricated by coupling Bi₂O₃ (narrow band gap) with layered BiOCl (rapid photoelectron transmission). During the degradation of Rhodamine B (RhB), the Bi₂O₃/BiOCl composite material presented excellent photocatalytic activity. Under visible light irradiation for 60 min, the Bi₂O₃/BiOCl photocatalyst delivered a superior removal rate of 99.9%, which was much higher than pristine Bi₂O₃ (36.0%) and BiOCl (74.4%). Radical quenching experiments and electron spin resonance spectra further confirmed the dominant effect of electron holes h⁺ and superoxide radical anions ·O₂^- for the photodegradation process. This work develops a green strategy to synthesize a high-performance photocatalyst for organic dye degradation.

Spindle-like MIL101(Fe) decorated with Bi2O3 nanoparticles for enhanced degradation of chlortetracycline under visible-light irradiation

Improving the photocatalytic performance of metal-organic frameworks (MOFs) is an important way to expand its potential applications. In this work, zero-dimensional (0D) Bi₂O₃ nanoparticles were anchored to the surface of tridimensional (3D) MIL101(Fe) by a facile solvothermal method to obtain a novel 0D/3D heterojunction Bi₂O₃/MIL101(Fe) (BOM). The morphology and optical properties of the as-prepared Bi₂O₃/MIL101(Fe) composite were characterized. The photocatalytic activity of the synthesized samples was evaluated by degrading chlortetracycline (CTC) under visible-light irradiation. The obtained BOM-20 composite (20 wt % Bi₂O₃/MIL101(Fe)) exhibits the highest photocatalytic activity with CTC degradation efficiency of 88.2% within 120 min. The degradation rate constant of BOM-20 toward CTC is 0.01348 min^-1, which is 5.9 and 4.3 times higher than that of pristine Bi₂O₃ and MIL101(Fe), respectively. The enhanced photocatalytic activity is attributed to the formation of a Z-scheme heterojunction between Bi₂O₃ and MIL101(Fe), which is conducive to the rapid separation of photogenerated carriers and the enhancement of photogenerated electron and hole redox capacity. The intermediate products were analyzed by liquid chromatography-mass spectrometry (LC-MS), and a possible photocatalytic degradation path of CTC was proposed. This work provides a new perspective for the preparation of efficient MOF-based photocatalysts.

Enhanced removal of oxytetracycline from wastewater using bimetallic Fe/Ni nanoparticles combined with ZIF-8 nanocomposites

The integration of metal-organic frameworks with other functional materials has recently emerged as a promising approach for creating innovative materials for environmental remediation. Here, a nano-sized iron/nickel (Fe/Ni) functionalized zeolitic imidazolate framework-8 (ZIF-8-Fe/Ni) was fabricated for oxytetracycline (OTC) removal from wastewater. Cyclic voltammetry and amperometric I-t measurements indicated that OTC was degraded by ZIF-8-Fe/Ni. X-ray diffraction spectroscopy (XRD), transmission electron microscopy mapping (TEM-mapping) and X-ray photoelectron spectroscopy (XPS) indicated that Fe/Ni was evenly dispersed throughout ZIF-8 and partially oxidized after reaction with OTC. OTC adsorption isotherms and kinetics best fitted the Langmuir isotherm (R² > 0.982) and pseudo-second-order model (R² > 0.997), respectively. Reduction kinetics data followed the pseudo-first-order model (R² > 0.905), where the apparent activation energy (Ea) was 22.9 kJ mol^-1, demonstrating that OTC degradation was mainly via a chemical process. The practical removal efficiency of OTC from real wastewater by ZIF-8-Fe/Ni was 92.6%, where even after application of ZIF-8-Fe/Ni for 5 consecutive removal cycles, a high OTC removal of 74.9% was maintained. Thus ZIF-8-Fe/Ni exhibited both high removal efficiency and good recyclability.

Synergistic Mechanism of Photocatalysis and Photo-Fenton by Manganese Ferrite and Graphene Nanocomposite Supported on Wood Ash with Real Sunlight Irradiation

The present research aimed to evaluate the photocatalytic activity of reduced graphene oxide and manganese ferrite nanocomposite supported on eucalyptus wood ash waste (WA) from industrial boilers, for the decolorization of methylene blue (MB) solutions, using sunlight as an irradiation source. For this, the photocatalyst named MnFe2O4-G@WA was synthesized by a solvothermal method and characterized by analyzes of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller and zeta potential. Firstly, the photocatalyst was evaluated for photocatalytic decolorization of MB under different reaction conditions. Then, the influence of pH, photocatalyst dose and H2O2 was evaluated. MnFe2O4-G@WA showed 94% of efficiency for photocatalytic decolorization of MB under operating conditions of solar irradiation, 0.25 g/L of catalyst, 300 mg/L of H2O2. The proposed degradation reaction mechanism suggested that the photodegradation of MB was through a synergistic mechanism of photocatalysis and photo-Fenton reactions, with the combined action of the three materials used. The data adjusted to the first order kinetics from the Langmuir–Hinshelwood model. In addition, MnFe2O4-G@WA showed high stability, maintaining its efficiency above 90% after 5 cycles. The results indicated that the nanophotocatalyst is a potential technology for the decolorization of MB solutions.

Graphene-based photocatalytic nanocomposites used to treat pharmaceutical and personal care product wastewater: A review

Photocatalytic technology has been widely studied by researchers in the field of environmental purification. This technology can not only completely convert organic pollutants into small molecules of CO₂ and H₂O through redox reactions but also remove metal ions and other inorganic substances from water. This article reviews the research progress of graphene-based photocatalytic nanocomposites in the treatment of wastewater. First, we elucidate the basic principles of photocatalysis, the types of graphene-based nanocomposites, and the role of graphene in photocatalysis (e.g., graphene can accelerate the separation of photon-hole pairs and increase the intensity and range of light absorption). Second, the preparation, characterization, and application of composites in wastewater are introduced. We also discuss the kinetic model of the photocatalytic degradation of pollutants. Finally, the enhancement mechanism of graphene in terms of photocatalysis is not completely clear, and graphene-based photocatalysts with high catalytic efficiency, low cost, and large-scale production have not yet appeared, so there is an urgent need for more extensive and in-depth research.

Applications of Heterogeneous Photocatalysis to the Degradation of Oxytetracycline in Water: A Review

Photocatalytic processes are being studied extensively as potential advanced wastewater treatments for the removal of pharmaceuticals, pesticides and other recalcitrant micropollutants from the effluents of conventional wastewater treatment plants (WWTPs). Oxytetracycline (OTC) is a widespread antibiotic which is frequently detected in surface water bodies as a recalcitrant and persistent micropollutant. This review provides an update on advances in heterogeneous photocatalysis for the degradation of OTC in water under UV light, sunlight and visible-light irradiation. Photocatalysts based on pure semiconducting oxides are rarely used, due to the problem of rapid recombination of electron–hole pairs. To overcome this issue, a good strategy could be the coupling of two different semiconducting compounds with different conduction and valence bands. Several methods are described to enhance the performances of catalysts, such as doping of the oxide with metal and/or non-metal elements, surface functionalization, composites and nano-heterojunction. Furthermore, a discussion on non-oxidic photocatalysts is briefly provided, focusing on the application of graphene-based nanocomposites for the effective treatment of OTC.

Photocatalytic Degradation of Orange G Dye by Using Bismuth Molybdate: Photocatalysis Optimization and Modeling via Definitive Screening Designs

In the current study, Bismuth molybdate was synthesized using simple co-precipitation procedure, and their characterization was carried out by various methods such as FT-IR, SEM, and P-XRD. Furthermore, the photocatalytic degradation of Orange G (ORG) dye using synthesized catalyst under visible light irradiation was studied. Response surface Method was used for the optimization of process variables and degradation kinetics evaluated by modeling of experimental data. Based on the experimental design outcomes, the first-order model was proven as a practical correlation between selected factors and response. Further ANOVA analysis has revealed that only two out of six factors have a significant effect on ORG degradation, however ORG concentration and irradiation time indicated the significant effects sequentially. Maximum ORG degradation of approximately 96% was achieved by keeping process parameters in range, such as 1 g L-1 loading of catalyst, 50 mg L-1 concentration of ORG, 1.4 mol L-1 concentration of H2O2 at pH 7 and a temperature of 30 °C. Kinetics of ORG degradation followed the pseudo first order, and almost complete degradation was achieved within 8 h. The effectiveness of the Bi2MoO6/H2O2 photo-Fenton system in degradation reactions is due to the higher number of photo-generated e- available on the catalyst surface as a result of their ability to inhibit recombination of e- and h+ pair.

Modern Carbon-Based Materials for Adsorptive Removal of Organic and Inorganic Pollutants from Water and Wastewater

Currently, a serious threat for living organisms and human life in particular, is water contamination with persistent organic and inorganic pollutants. To date, several techniques have been adopted to remove/treat organics and toxic contaminants. Adsorption is one of the most effective and economical methods for this purpose. Generally, porous materials are considered as appropriate adsorbents for water purification. Conventional adsorbents such as activated carbons have a limited possibility of surface modification (texture and functionality), and their adsorption capacity is difficult to control. Therefore, despite the significant progress achieved in the development of the systems for water remediation, there is still a need for novel adsorptive materials with tunable functional characteristics. This review addresses the new trends in the development of new adsorbent materials. Herein, modern carbon-based materials, such as graphene, oxidized carbon, carbon nanotubes, biomass-derived carbonaceous matrices-biochars as well as their composites with metal-organic frameworks (MOFs) and MOF-derived highly-ordered carbons are considered as advanced adsorbents for removal of hazardous organics from drinking water, process water, and leachate. The review is focused on the preparation and modification of these next-generation carbon-based adsorbents and analysis of their adsorption performance including possible adsorption mechanisms. Simultaneously, some weak points of modern carbon-based adsorbents are analyzed as well as the routes to conquer them. For instance, for removal of large quantities of pollutants, the combination of adsorption and other methods, like sedimentation may be recommended. A number of efficient strategies for further enhancing the adsorption performance of the carbon-based adsorbents, in particular, integrating approaches and further rational functionalization, including composing these adsorbents (of two or even three types) can be recommended. The cost reduction and efficient regeneration must also be in the focus of future research endeavors. The targeted optimization of the discussed carbon-based adsorbents associated with detailed studies of the adsorption process, especially, for multicomponent adsorbate solution, will pave a bright avenue for efficient water remediation.

Water hyacinth plant extract mediated green synthesis of Cr2O3/ZnO composite photocatalyst for the degradation of organic dye

The Cr2O3/ZnO composite catalysts with varying the amount of chromium precursors abbreviated as 0.02CrZn, 0.04CrZn, 0.06CrZn, 0.08CrZn, 0.1CrZn, and fixed the amount of Zn precursor (0.1 M) were prepared by using water hyacinth (Eichhornia crassipes) extract as a template/capping agent. The prepared catalysts were characterized and the catalytic performances of the catalysts were also checked for the degradation of methylene blue (MB) dye. The photocatalytic MB dye degradation by 0.08CrZn catalyst was achieved and 85% of MB dye was degraded within 90 min irradiation time. However, 0.1CrZ, 0.06CrZ, 0.04CrZ, 0.02CrZ, ZnO, and Cr2O3 catalysts degrade only 80, 74, 79, 76, 52, and 74% of MB dye, respectively. The catalytic performances indicated that the addition of optimum amount of chromium precursor in the preparation of Cr2O3/ZnO composite catalysts with the aid of Eichhornia crassipes plant extract enhances the catalytic activities. This performance enhancement could be as a result of reducing the electron/hole pair separation and the porosity resulted from the plant extract in the catalyst system.

Degradations of endocrine-disrupting chemicals and pharmaceutical compounds in wastewater with carbon-based nanomaterials: a critical review

Although water occupies 75% of the earth's surface, only 0.0067% of the total water is available for human activities. These statistics further decline with the population growth and consequent multiplication in the amount of annual waste produced. The demand for clean and safe drinking water has always been a prime concern in the global scenario. Among various types of waste materials, endocrine-disrupting chemicals (EDCs) and pharmaceutical effluents have become a constant threat to the aquatic ecosystem and possess challenges worldwide. Endocrine-disrupting chemicals (EDCs) are a mixed group of emerging concern chemicals with the ability to mimic the mechanisms of biosynthesis, transport, and metabolism of hormones. These chemicals pose various health threats such as early puberty, infertility, obesity, diabetes, reproductive disorders, cancerous tumors, and related disorders (immune cells, hormones' activity, and various organs). On the other hand, pharmaceutical compounds such as antibiotics also harm the natural environment, human health, and soil microbiology. Their low concentration, ranging from a few ng/L to μg/L, gives rise to a micro-pollution phenomenon, which makes it difficult to detect, analyze, and degrade in wastewater treatment plants. Activated carbons (ACs) and other adsorbents, including naturally occurring materials (wood, keratin) are considered as nanomaterials (NMs) reference for the separation of organic pollutants. It is generally acknowledged that mass-transfer phenomena control sorption kinetics at the liquid/solid interface, with retention controlled by the sorbent/sorbate properties. Therefore, the type of interaction (strong or weak van der Waals forces) and the hydrophilic/hydrophobic properties of the adsorbent are two crucial factors. Besides, EDCs and pharmaceutical compound sorption on such kinds of nanoporous solids depend on both the molecule size and charge density. The applications of nanomaterials on non-conservative methods, like advanced oxidation processes or AOPs (e.g., photocatalysis and Fenton reaction), are contemplated as more apt in comparison to conservative technology like reverse osmosis nanofiltration, and adsorption, etc. One of the reasons is that AOPs generate free radicals (hydroxyls), which are strong oxidants for the demineralization of organic compounds and the extreme case that hydroxyl radicals can attack any kinds of pollutants with the generation of only water and carbon dioxide as final products. AOPs may imply the use of NMs as either catalysts or photocatalysts, which improve the selective removal of the target pollutant. Therefore, various literature reviews have revealed that there is a timely need to upgrade the efficiency of the remediation approaches to protect the environment against EDCs and pharmaceuticals adequately. There is currently a lack of definitive risk assessment tools due to their complicated detection and associated insufficiency in the health risk database. Hence, our present review focuses on applying carbon-based nanomaterials to remove EDCs and pharmaceuticals from aqueous systems. The paper covers the effect of these pollutants and photocatalytic methods for treating these compounds in wastewater, along with their limitations and challenges, plausible solutions, and prospects of such techniques.

Recent advances in photodegradation of antibiotic residues in water

Antibiotics are widely present in the environment due to their extensive and long-term use in modern medicine. The presence and dispersal of these compounds in the environment lead to the dissemination of antibiotic residues, thereby seriously threatening human and ecosystem health. Thus, the effective management of antibiotic residues in water and the practical applications of the management methods are long-term matters of contention among academics. Particularly, photocatalysis has attracted extensive interest as it enables the treatment of antibiotic residues in an eco-friendly manner. Considerable progress has been achieved in the implementation of photocatalytic treatment of antibiotic residues in the past few years. Therefore, this review provides a comprehensive overview of the recent developments on this important topic. This review primarily focuses on the application of photocatalysis as a promising solution for the efficient decomposition of antibiotic residues in water. Particular emphasis was laid on improvement and modification strategies, such as augmented light harvesting, improved charge separation, and strengthened interface interaction, all of which enable the design of powerful photocatalysts to enhance the photocatalytic removal of antibiotics.

Synthesis and enhanced photocatalytic activity of the flower-like CdS/Zn3(PO4)2 Z-scheme heteronanostructures

CdS/Zn3(PO4)2 Z-scheme heteronanostructures were prepared through a simple hydrothermal route and precipitation methods, and the efficiency for the photocatalytic degradation of MB solution can be improved greatly.

Application of graphene-based materials for removal of tetracyclines using adsorption and photocatalytic-degradation: A review

Tetracyclines are extensively used to treat human and animal infectious diseases due to its effective antimicrobial activities. About 70-90% of its parent materials are released into the environment through urine and feces, implying they are the most frequently detected antibiotics in the environment with high ecological risks. Adsorption and photocatalysis have been promising techniques for the removal of tetracyclines due to effectiveness and efficiency. Graphene-based materials provide promising platforms for adsorptive and photocatalytic removal of tetracyclines from aqueous environment owning to distinctive remarkable physicochemical, optical, and electrical characteristics. Herein, we intensively reviewed the available literatures in order to provide comprehensive insight about the applications and mechanisms of graphene-based materials for removal of tetracyclines via adsorption and phototocatalysis. The synthesis methods of graphene-based materials, the tetracycline adsorption and photocatalytic-degradation conditions, and removal mechanisms have been extensively discussed. Finally concluding remarks and future perspectives have been deduced and recommended to stimulate further researches in the subject. The review study can be used as theoretical guideline for further researchers to improve the current approaches of material synthesis and application towards tetracyclines removal.

Design and performance of a novel direct Z-scheme NiGa2O4/CeO2 nanocomposite with enhanced sonocatalytic activity

A novel direct Z-scheme NiGa₂O₄/CeO₂ nanocomposite was designed and prepared via simple sol-hydrothermal and calcination methods, and its sonocatalytic activity was tested by studying the degradation of a model antimicrobial agent, malachite green (MG), under ultrasonic irradiation. Near complete (96.2%) degradation of MG (at 10 mg/L) could be achieved by the NiGa₂O₄/CeO₂ nanocomposite (at 1.0 g/L) after ultrasonic irradiation (40 kHz, 300 W) for 60 min at 25 °C. Under the same conditions, only 51.2 and 72.0% of the MG degraded in the presence of NiGa₂O₄ and CeO₂ (at 1.0 g/L), respectively. These results demonstrate that the direct Z-scheme NiGa₂O₄/CeO₂ nanocomposite has excellent sonocatalytic activity, which is attributed to the matching band-gaps between NiGa₂O₄ and CeO₂. The sonocatalytic activity of NiGa₂O₄/CeO₂ nanocomposite decreased by 17% after four cycles of reuse, which is indicative of relatively good reusability. Scavenging experiments revealed that sonocatalytic degradation of MG results from the combined action of hydroxyl radicals (OH) and holes (h⁺), with the latter having a greater contribution. The pathways and mechanism of MG degradation were proposed based on the degradation intermediates detected. The results demonstrate that the prepared direct Z-scheme NiGa₂O₄/CeO₂ nanocomposite worked as designed and exhibited high and stable sonocatalytic activity during MG degradation, and could thus serve as a promising candidate in sonocatalytic treatment of other organic pollutants in wastewaters. The findings also provide new insights on the mechanism of sonocatalytic degradation and the design of efficient Z-scheme sonocatalysts.

Assessment of ampicillin removal efficiency from aqueous solution by polydopamine/zirconium(iv) iodate: optimization by response surface methodology

Polydopamine/zirconium(iv) iodate was prepared by incorporating polydopamine into zirconium iodate gel and studied as an effective adsorbent for ampicillin. In order to characterize the prepared composite, FTIR, XRD, TGA-DTA, SEM and TEM were used. The effects of experimental variables on ampicillin removal were examined using response surface methodology. The optimum conditions for ampicillin removal were 7, 130 min, 20 mg/20 mL and 50 mg L-1 for pH, contact time, adsorbent dose and initial ampicillin concentration, respectively. Under the optimum conditions, the maximum ampicillin removal percentage was found to be 99.12%. The Langmuir isotherm and pseudo-second-order kinetic models explained the removal process more appropriately. The maximum adsorption capacity at 303 K was 100.0 mg g-1. Thermodynamic study revealed that the ampicillin adsorption was spontaneous and endothermic in nature. The reusability of the prepared material was also explored.

Preparation of Hollow Flower-Like Microspherical β-Bi2O3/BiOCl Heterojunction and High Photocatalytic Property for Tetracycline Hydrochloride Degradation

Tetracycline cannot be effectively degraded in wastewater treatment. Therefore, the development of excellent photocatalysts is of significant importance for environmental protection. In this study, a β-Bi₂O₃/BiOCl heterojunction photocatalyst with hollow flower-like microspheres was successfully synthesized by the in-situ reaction of HCl and β-Bi₂O₃ hollow spheres. The prepared samples are characterized by Scanning electron microscopy, Transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N₂ physical adsorption, UV-vis diffuse reflectance spectroscopy, and Photoluminescence. Then, research on the photocatalytic performance for the degradation of tetracycline hydrochloride was conducted. The results show that the photocatalytic performance of the β-Bi₂O₃/BiOCl composite is significantly better than the β-Bi₂O₃ and BiOCl. The increase in photocatalytic activity is due to the formation of a heterojunction between β-Bi₂O₃ and BiOCl, which effectively promotes the separation of photogenerated electron-hole pairs. Additionally, the heterojunction nanocomposite demonstrated the outstanding photocatalytic stability after five cycles, which indicates that the material can be used for water environment purification. This paper provides assistance for studying the photocatalytic mechanism of heterojunction photocatalytic materials.

A review of graphene-based nanomaterials for removal of antibiotics from aqueous environments

Antibiotics as emerging pharmaceutical pollutants have seriously not only threatened human life and animal health security, but also caused environmental pollution. It has drawn enormous attention and research interests in the study of antibiotics removal from aqueous environments. Graphene, an interesting one-atom-thick, 2D single-layer carbon sheet with sp² hybridized carbon atoms, has become an important agent for removal of antibiotic, owing to its unique physiochemical properties. Recently, a variety of graphene-based nanomaterials (GNMs) are reported to efficiently remove antibiotics from aqueous solutions by different technologies. In this review, we summarize different structure and properties of GNMs for the removal of antibiotics by adsorption. Meanwhile, advanced oxidation processes (AOPs), such as photocatalysis, Fenton process, ozonation, sulfate radical and combined AOPs by the aid of GNMs are summarized. Finally, the opportunities and challenges on the future scope of GNMs for removal of antibiotics from aqueous environments are proposed.

Mineralization of cefoperazone in acid medium by the microwave discharge electrodeless lamp irradiated photoelectro-Fenton using a RuO2/Ti or boron-doped diamond anode

The mineralization of 125 mL of 50-300 mg L^-1 cefoperazone (CFPZ) has been comparatively studied by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation (AO), electro-Fenton (EF) and photoelectro-Fenton (PEF) with a RuO₂/Ti or boron-doped diamond (BDD) anode and an activated carbon fiber (ACF) cathode. A microwave discharge electrodeless lamp (MDEL) was used as the UV source in PEF process. CFPZ decays always followed pseudo-first-order kinetics and their constant rates increased in the order: AO < EF < MDEL-PEF, regardless of anode types. Higher mineralization was achieved in all methods using BDD instead of RuO₂/Ti, while the most potent BDD-MDEL-PEF gave 88% mineralization under its optimum conditions of 0.36 A, pH 3.0 and 1.0 mmol L^-1 Fe²⁺. The synergistic mechanisms were explored by quantifying the electrogenerated H₂O₂ and formed ^•OH, in which 2.27 and 2.58 mmol L^-1 H₂O₂ were accumulated in AO-H₂O₂ with RuO₂/Ti or BDD anode, respectively, while 92.0 and 263.5 μmol L^{-1 •}OH were generated in EF with RuO₂/Ti or BDD anode, respectively. The oxidation power of EAOPs with different anodes was also compared by measuring the evolutions of NO₃^- and NH₄⁺ as well as four generated carboxylic acids including oxalic, oxamic, formic and fumaric acids.

Degradation of antibiotics in multi-component systems with novel ternary AgBr/Ag3PO4@natural hematite heterojunction photocatalyst under simulated solar light

Abatement of antibiotics from aquatic systems is of great importance but remains a challenge. Herein, we prepared ternary AgBr/Ag₃PO₄@natural hematite (AgBr/Ag₃PO₄@NH) heterojunction composite via a simple route for the photocatalytic degradation of antibiotic pollutants. By adjusting the dose of Ag species, four products with different Ag content (denoted as Ag_0.5BrPFe, Ag₁BrPFe, Ag_1.5BrPFe, and Ag₂BrPFe) were developed. Among them, Ag_1.5BrPFe exhibited the best photocatalytic activity. Four antibiotics (i.e. ciprofloxacin (CIP), norfloxacin (NOR), sulfadiazine (SDZ), and tetracycline (TTC)) could be degraded with synthesized Ag_1.5BrPFe in multi-component systems. Water matrix indexes including solution pH, coexisting anions, humic acids exhibited distinct effects on the degradation process. The results revealed that the degradation process was accelerated at acidic conditions while depressed at basic conditions. Superoxide radical and hole were detected by in situ electron spin resonance technique and played the dominant roles. The degradation pathway TTC was tentatively established followed with the identification of the degradation intermediates and computational analysis. This work would shed light on the photocatalytic degradation mechanism of organic pollutants by the AgBr/Ag₃PO₄@NH composite.

A novel L-Histidine (C, N) codoped-TiO2-CdS nanocomposite for efficient visible photo-degradation of recalcitrant compounds from wastewater

The aim of current study is to synthesis novel visible driven photocatalysts (L-Histidine (C, N) codoped-TiO₂-CdS) with different loadings of L-Hisitdine (1, 2, and 3 wt.%) and CdS (1:9, 7:1, and 1:5 mass ratios of CdS to TiO₂). Then, their application for photo-degradation of methyl orange (MO) and biologically treated palm oil mill effluent (POME) were studied. The structure, optical properties, and morphology of the prepared nanocomposites were also characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR), photoluminescence spectroscopy (PL), and diffuse reflectance spectra (DRS). DRS results indicated that all the modified samples with different L-Hisitdine and CdS loadings showed a red shift to visible region. The results of photo-degradation experiments showed that L-Hisitdine with a weight fraction of 2% and mass ratio of TiO₂ to CdS of 7:1 were the optimum amount of the modifiers in the photocatalyst network. The PL intensity of the photocatalyst decreased with addition of L-Hisitdine and CdS nanoparticles due to a decrease in e^-/h⁺ recombination. The effects of organic pollutant concentration, initial pH, catalyst concentration, and irradiation time on the photo-degradation process of MO and POME were studied using full faced centered central composite design (CCFD) under response surface methodology (RSM). The obtained results showed that MO was completely removed at initial concentration of 10 mg/L, acidic pH, and catalyst loading of 1.5 g/L after 120 min. The complete degradation of biologically treated POME was achieved at original pH, 300 mg/L of chemical oxygen demand (COD) concentration, catalyst loading of 2 g/L, and irradiation time of 2 h.

Heterogeneous activation of peroxymonosulfate for bisphenol AF degradation with BiOI0.5Cl0.5

This study represents the first investigation on the application of peroxymonosulfate (PMS) for the degradation of bisphenol AF (BPAF) using halogen bismuth oxide composites (BiOI_0.5Cl_0.5). The hierarchical BiOI_0.5Cl_0.5 was successfully synthesized and systematically characterized with multifarious techniques including XRD, SEM, FTIR and XPS to investigate the morphology and physicochemical properties of the samples. Several parameters affecting the degradation efficiency including catalyst dosage, PMS loading, and pH value were elucidated. Inorganic ions such as HCO₃⁻ showed significant inhibition in the BiOI_0.5Cl_0.5/PMS process due to the quenching effect. The effect of various water matrices including tap water and surface water on the removal of BPAF was studied to indicate that the present reaction system shows great potential for cleaning BPAF waste water. Furthermore, the production of sulfate radicals and hydroxyl radicals was validated through radical quenching and ESR tests, thus a possible oxidation mechanism was proposed. Overall, these results reveal that the activation of PMS by the BiOI_0.5Cl_0.5/PMS system is an efficient and promising advanced oxidation technology for the treatment of BPAF-contaminated waters and wastewaters.

This study represents the first investigation on the application of peroxymonosulfate (PMS) for the degradation of bisphenol AF (BPAF) using halogen bismuth oxide composites (BiOI_0.5Cl_0.5).