Synthesis and Characterization of ZnBi2O4 Nanoparticles: Photocatalytic Performance for Antibiotic Removal under Different Light Sources

A review of non-thermal plasma -catalysis: The mutual influence and sources of synergetic effect for boosting volatile organic compounds removal

This review is aimed at researchers in air pollution control seeking to understand the latest advancements in volatile organic compound (VOC) removal. Implementing of plasma-catalysis technology for the removal of volatile organic compounds (VOCs) led to a significant boost in terms of degradation yield and mineralization rate with low by-product formation. The plasma-catalysis combination can be used in two distinct ways: (I) the catalyst is positioned downstream of the plasma discharge, known as the "post plasma catalysis configuration" (PPC), and (II) the catalyst is located in the plasma zone and exposed directly to the discharge, called "in plasma catalysis configuration" (IPC). Coupling these two technologies, especially for VOCs elimination has attracted the interest of many researchers in recent years. The term "synergy" is widely reported in their works and associated with the positive effect of the plasma catalysis combination. This review paper investigates the state of the art of newly published papers about catalysis, photocatalysis, non-thermal plasma, and their combination for VOC removal application. The focus is on understanding different synergy sources operating mutually between plasma and catalysis discussed and classified into two main parts: the effect of the plasma discharge on the catalyst and the effect of the catalyst on plasma discharge. This approach has the potential for application in air purification systems for industrial processes or indoor environments.

Recent advances in designing and developing efficient sillenite-based materials for photocatalytic applications

Sillenite materials have been the subject of intense investigation for recent years due to their unique characteristics. They possess a distinct structure with space group I23, allowing them to exhibit distinctive features, such as an electronic structure ideal for certain applications such as photocatalysis. The present research delves into the structure, synthesis, and properties of sillenites, highlighting their suitability for photocatalysis. It explores also advanced engineering strategies for designing sillenite-based photocatalysts, including heterojunction formation, morphology modification, doping, and hybrid processes. Each strategy offers advantages and limitations that are critically discussed. The review then lists and discusses the photocatalytic performance of various sillenite-based systems recently developed for common applications, such as removing hazardous organic and inorganic contaminants, and even infrequent applications, such as microbial inactivation, H2 generation, CO2 reduction and N2 fixation. Finally, valuable insights and suggestions are put forward for future research directions in the field of sillenite-based photocatalysis. This comprehensive overview would provide a valuable resource for the development of efficient photocatalytic systems to address environmental and energy challenges.

Progress of photocatalytic oxidation-adsorption synergistic removal of organic arsenic in water

Photocatalytic oxidation-adsorption synergistic treatment of organic arsenic pollutants is a promising wastewater treatment technology, which not only degrades organic arsenic pollutants by photocatalytic degradation but also removes the generated inorganic arsenic by adsorption. This paper compares the results of photocatalytic oxidation-adsorption co-treatment of organic arsenic pollutants such as monomethylarsonic acid, dimethylarsinic acid, phenylarsonic acid, p-arsanilic acid, and 3-nitro-4-hydroxyphenylarsonic acid on titanium dioxide, goethite, zinc oxide, and copper oxide. It examines the influence of the morphology of organic arsenic molecules, pH, coexisting ions, and the role of natural organic matter. The photocatalytic oxidation-adsorption co-treatment mechanism is investigated, comparing the hydroxyl radical oxidation mechanism, the hydroxyl radical and superoxide anion radical cooxidation mechanism, and the hydroxyl radical and hole cooxidation mechanism. Finally, the future prospects of metal oxide photocatalytic materials and the development of robust and efficient technologies for removing organic arsenic are envisioned.

Photocatalytic degradation of norfloxacin antibiotics on ZnxCd(1-x)S/g-C3N4 composites in water

g-C3N4/ZnxCd(1-x)S composites were synthesized by a simple hydrothermal method. The composites were characterized by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, infrared spectroscopy, and electron micro-projective microscopy. According to the performance of ZnxCd(1-x)S for the photocatalytic degradation of norfloxacin under visible light in water, the best stoichiometric number of x was 0.5. The best photolytic norfloxacin degradation rate of g-C3N4/ZnxCd(1-x)S composites was 89.8%, which was obtained when the dosage ratio of g-C3N4 to ZnxCd(1-x)S was 1:1. The experiment was conducted to investigate the effect of pH on the catalyst to obtain the optimal NORF degradation environment pH in the range of 7 ± 0.3; by simulating the anions that may be contained in the actual environmental water, the results showed that the catalyst has a certain effect on the degradation of NORF when the water contains NO3-, Cl- and HCO3-. In addition, this study also obtained that the main active substances produced by the catalyst during degradation were electron-hole pairs by adding different trapping agents in the NORF removal experiments; and the catalyst was able to achieve a degradation rate of 86.1% after four cycles of the experiments, which proved that it had good stability.

Gold-Deposited Graphene Nanosheets for Self-Cleaning Graphene Surface-Enhanced Raman Spectroscopy with Superior Charge-Transfer Contribution

The interaction of graphene with metals initiates charge-transfer interaction-induced chemical enhancements, which critically depend on the doping effect from deposited metallic configurations. In this paper, we have explored the gold nanoparticle-decorated monolayer graphene nanosheets for the large graphene-induced Raman enhancement of adsorbed analytes, indicating the surface-enhanced Raman spectroscopy (SERS) capabilities of metal-doped graphene (G-SERS). Here, the systematically sputtered Au thickness optimization procedure revealed noticeable modifications in the graphene Raman spectra and photoluminescence (PL) background quenching, which indicated favorable charge transfer through n-type doping of chemical vapor deposition-grown graphene nanosheets. The highly consistent, individually distributed morphology of the gold nanoislands over graphene nanosheets depicted a reproducibly uniform G-SERS signal with excellent relative standard deviation values (<5%), resulting in the strongest Raman intensity enhancement factors of ∼108 (MB) (methylene blue) and 107 (DPA) (2,6-pyridinedicarboxylic acid) composed of the weakest PL background. The combined charge-transfer-induced chemical enhancement and electromagnetic enhancement from individual Au nanoislands result in a lowering of detectability down to 10-16 M (MB) and 10-11 M (DPA) concentrations with efficient time-dependent signal stability. Additionally, the GAu demonstrated its effective (∼94.4%) photocatalytic degradation capabilities by decomposing MB dye molecules from a concentration of 1 μM to 2.52 fM within 60 min. Therefore, the prominent charge-transfer contribution through controlled Au decoration over graphene nanosheets provides a potential strategy for fabricating superior SERS sensors and photocatalysts exhibiting adequate signal consistency, stability, and photodegradation efficiency through overcoming the limitations of the traditional sensing platforms.

Photocatalytic Activity and Self-Cleaning Effect of Coating Mortars with TiO2 Added: Practical Cases in Warm Sub-Humid Climates

In this study, the photocatalytic activity of coating mortars with synthetized and commercial TiO2 nanoparticles added has been evaluated at 2, 3 and 5% by weight of cement by calculating the degradation efficiency of methyl orange and red wine dyes exposed to both visible-light and UV radiation; also, the self-cleaning effect of coatings exposed to weather conditions (warm sub-humid climate) was assessed. TiO2 nanoparticles were synthesized via the sol-gel method to a low synthesis temperature and characterized via X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The results show synthesized TiO2 particles in anatase phase with a crystallite size of 14.69 nm, and hemispherical particles with sizes of submicron order. The addition percentage with the best performance in the coating mortars was 3%, with both commercial and synthesized TiO2; however, coating mortars with synthesized TiO2 exhibited the highest degradation efficiency for both dyes when they were exposed to visible light, while mortars with commercial TiO2 exhibited the highest degradation efficiency when exposed to UV radiation. In addition, in coating mortars with synthesized TiO2, the self-cleaning effect was evident from the beginning of exposure to weather, reaching the largest dye-free surface at the end of exposure. The compressive strength increased significantly in mortars with TiO2 addition.

Rational design of full-spectrum visible-light-responsive bimetallic sulfide Bi2S3/CoS2 composites for high-efficiency photocatalytic degradation of naproxen and bacterial inactivation

Photocatalytic water decontamination has emerged as a highly promising technology for efficient and rapid water treatment, harnessing sustainable solar energy as its driving force. In this study, we prepared visible-light active Bi2S3/CoS2 composites for the degradation of naproxen (NPX) and the inactivation of Escherichia coli (E. coli). The homogeneous dispersion of CoS2 was stably integrated with Bi2S3, resulting in a significant enhancement of the specific surface area, efficient utilization of visible light, and effective separation of photogenerated charge carriers. Consequently, this synergistic photocatalytic system greatly facilitated the successful degradation of NPX and the inactivation of E. coli under visible-light irradiation. Compared to the pure Bi2S3 and CoS2 catalysts, the Bi2S3/CoS2 (1:2) composites displayed significantly enhanced photodegradation activity, achieving 96.46% (k = 0.2847 min-1) degradation of NPX within 90 min and maintaining good recyclability with no significant decline after six successive cycles. Additionally, the photocatalytic inactivation of E. coli results indicated that Bi2S3/CoS2 composites exhibited excellent performance, leading to the inactivation of 7 log10 cfu mL-1 of bacterial cells after 150 min of visible-light exposure. Scanning Electron Microscopy (SEM) and K+ ions leakage tests demonstrated that the destruction of the E. coli cell membrane structure resulted in cell death. The outcomes of this work suggest that Bi2S3/CoS2 composites hold significant potential for treating water contaminated with antibiotic and microbial pollutants.

Nanomaterials to address the genesis of antibiotic resistance in Escherichia coli

Escherichia is a genus of prokaryotic gram-negative bacteria which forms a vital component of the gut microbiota of homeotherms including humans. Many members of this genus are commensals and pathogenic strains, which are responsible for some of the most common bacterial infections and can be fatal, particularly in the case of newborns and children. The fecal matter in wastewater treatment plants serves as major environmental sinks for the accumulation of Escherichia. The rise in antibiotic pollution and the lateral gene exchange of antibiotic-resistant genes have created antibiotic-resistant Escherichia strains that are often called superbugs. Antibiotic resistance has reached a crisis level that nowadays existing antibiotics are no longer effective. One way of tackling this emerging concern is by using nanomaterials. Punitively, nanomaterials can be used by conjugating with antibodies, biomolecules, and peptides to reduce antibiotic usage, whereas, preventatively, they can be used as either nano-antimicrobial additives or nano-photocatalytic sheets to reduce the microbial population and target the superbugs of environmental Escherichia. In this review, we have explored the threat posed by pathogenic Escherichia strains in the environment, especially in the context of antibiotic-resistant strains. Along with this, we have discussed some nanomaterial-mediated strategies in which the problem can be addressed by using nanomaterials as nanophotocatalytics, antimicrobial additives, drugs, and drug conjugates. This review also presents a brief overview of the ecological threats posed by the overuse of nanomaterials which warrants a balanced and judicious approach to the problem.

Efficient removal of the antibiotic Cefixime on Mg0.3Zn0.7O under solar light: kinetic and mechanism studies

The heterogeneous photocatalysis is known to provide significant degradation and mineralization of emerging contaminants including antibiotics. For this, nanosized Mg_0.3Zn_0.7O (MZO) was prepared by nitrate route to be used as photocatalyst. The single-phase was confirmed by X-ray diffraction with a crystallite size of 33 nm. The morphology was visualized by scanning electron microscope/energy-dispersive X-ray analysis. The physicochemical properties were studied by the FTIR, XPS, and optical analyses. The diffuse reflectance gives a direct forbidden band of 3.26 eV. The electrochemical characterization showed an n-type semiconductor with a flat band of - 0.56 V_Ag/AgCl. The photodegradation of Cefixime (CFX) was carried out under solar light; the operating parameters such as the catalyst dose, solution pH, and initial CFX concentration (C_o) were optimized. The best performance occurs at neutral pH ~ 6 within 4 h with an abatement of 94% for an initial CFX concentration of 5 mg/L and MZO dose of 0.75 g/L. The photodegradation follows a first-order kinetic with an apparent rate constant of 0.012 min^-1. The effects of scavenging agents indicated the dominant role of hydroxyl ^•OH followed by the holes (h⁺). The results showed the potentiality of MZO as an environmentally friendly photocatalyst for CFX photodegradation.

Sorbent and Photocatalytic Potentials of Local Clays for the Removal of Organic Xenobiotic: Case of Crystal Violet

Natural materials are widely used in the field of environmental remediation and are appreciated for their surface physical and chemical properties. Clay constitutes a typical example. In this work, we report the evaluation of sorbent and photocatalytic potentials of local clay of two irrigated rice field waters in the degradation of crystal violet. The structural, textural and compositional properties of the local clay were investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) analysis. The analysis results showed that these materials were composed mainly of quartz and kaolinite. The efficiency of these adsorbents (Y. Clay and L. Clay) to eliminate crystal violet dye from aqueous medium was examined at different initial concentrations, pH, contact time, adsorbent dose and the possible interference of inorganic salts from fertilizers. Kinetic studies showed that the adsorption process was well described by the pseudo-second order model and the equilibrium modelling results fitted adequately to the Freundlich model. The maximum amount of uptake capacity achieved at pH 2.0 was 18.40 (mg·g−1) and 20.40 (mg·g−1), respectively, for Y. Clay and L. Clay. The evaluation of the photocatalytic potential showed that the raw clay samples do not show photocatalytic activities during the 30 min of exposure to UV light. On the other hand, their photocatalytic potential is manifested when loaded with titanium dioxide (TiO2). Clays coupled with TiO2 under UV light showed an improvement in the degradation of the crystal violet dye by 15%. The synergistic effects between the high photocatalytic activity of TiO2 and the strong adsorption capacity of clays can be one promising technique for in situ remediation of contaminated soaked rice field.

Ultrasound-Assisted Hydrothermal Synthesis of SrSnO3/g-C3N4 Heterojunction with Enhanced Photocatalytic Performance for Ciprofloxacin under Visible Light

In this work, an SrSnO3/g-C3N4 heterojunction with different dosage of SrSnO3 was fabricated by an ultrasound-assisted hydrothermal approach and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectra (UV-Vis DRS), and photoluminescence spectroscopy (PL). Ciprofloxacin was adopted to assess the degradation performance, and the sample combined with 40% SrSnO3 eliminated 93% of ciprofloxacin (20 mg/L) within 3 h under visible light, which is 6.6 and 1.7 times greater than for SrSnO3 and g-C3N4, respectively. Furthermore, 85% CIP was extinguished after five cycles of a photocatalytic process. Ultimately, a possible photocatalytic mechanism was dissected.

Bismuth Sillenite Crystals as Recent Photocatalysts for Water Treatment and Energy Generation: A Critical Review

Photocatalysis has been widely studied for environmental applications and water treatment as one of the advanced oxidation processes (AOPs). Among semiconductors that have been employed as catalysts in photocatalytic applications, bismuth sillenite crystals have gained a great deal of interest in recent years due to their exceptional characteristics, and to date, several sillenite material systems have been developed and their applications in photoactivity are under study. In this review paper, recent studies on the use of Bi-based sillenites for water treatment have been compiled and discussed. This review also describes the properties of Bi-based sillenite crystals and their advantages in the photocatalytic process. Various strategies used to improve photocatalytic performance are also reviewed and discussed, focusing on the specific advantages and challenges presented by sillenite-based photocatalysts. Furthermore, a critical point of certain bismuth catalysts in the literature that were found to be different from that reported and correspond to the sillenite form has also been reviewed. The effectiveness of some sillenites for environmental applications has been compared, and it has demonstrated that the activity of sillenites varies depending on the metal from which they were produced. Based on the reviewed literature, this review summarizes the current status of work with binary sillenite and provides useful insights for its future development, and it can be suggested that Bismuth sillenite crystals can be promising photocatalysts for water treatment, especially for degrading and reducing organic and inorganic contaminants. Our final review focus will emphasize the prospects and challenges of using those photocatalysts for environmental remediation and renewable energy applications.

Construction of plasmonic Bi/Bismuth oxycarbonate/Zinc bismuth oxide ternary heterojunction for enhanced charge carrier separation and photocatalytic performances

In this work, a novel plasmonic ternary Bi/Bismuth oxycarbonate/Zinc bismuth oxide (Bi-Bi₂O₂CO₃-ZnBi₂O₄) is synthesized synergistically by a one-step hydrothermal method. The results show that the metallic Bi spheres and ZnBi₂O₄ nanoparticles are uniformly distributed on the surface of flower-like Bi₂O₂CO₃ layer. Compared with the bare ZnBi₂O₄ and Bi-Bi₂O₂CO₃, the ternary Bi-Bi₂O₂CO₃-ZnBi₂O₄ heterojunction displays a significantly improved solar energy harvesting efficiency and enhanced photocatalytic degradation activity for environmental organic pollutants. The degradation efficiency of organics reaches to 98.4% under simulated solar light illumination. The degradation kinetics indicates that the photocatalytic reaction rate constant of ternary system is about 4.4 and 29.5 times higher than that of pure ZnBi₂O₄ and Bi-Bi₂O₂CO₃, respectively. Moreover, O₂^- and h⁺ are the main active species in the photodegradation reaction. The improvement of the photocatalytic activity of the composites is attributed to the synergistic effect of ternary heterostructure and surface plasmon resonance (SPR), which promotes charge transfer and effectively inhibits the recombination of photogenerated carriers.

Synthesis, structural, and opto-electrochemical properties of cobalt aluminate type spinel and its use with ZnO for Cr(VI) photoreduction

The discovery of the occurrence of inorganic pollutants in surface waters is identified in the system assessment quality. The most harmful elements are pesticides, persistent organic pollutants, pharmaceuticals, personal care products, and heavy metals are still dangerous to the environment due to their general uses. Chromate has the largest concentration compared to the other metals in the wastewater industries. This work evaluates the application of the spinel p-CoAl₂O₄ as a photocatalyst prepared by the nitrate synthesis process to reduce Cr(VI), a hazardous metal for the environment. The photocatalyst was characterized using thermal analysis (TG), X-ray diffraction, UV-diffuse reflectance spectroscopy, scanning electron microscopy, fluorescent X-ray, Fourier transform infrared spectroscopy, electrical conductivity, and photoelectrochemically. The results showed that the efficiency of optimum reduction of Cr(Vl) to Cr(IIl) photoreduction is more effective (77%) for pH = 3.6 than that at high pH values up to 8 (7%). Moreover, the effect of the hetero-system CoAl₂O₄/ZnO on photocatalytic efficiency was investigated. The photocatalytic activity increases up to 99% with 1 g L^-1, a total catalyst dosage over the hetero-system CoAl₂O₄/ZnO at a ratio of 75%/25%. This data is better relative to CoAl₂O₄ or ZnO alone. The Cr(VI) photoreduction activity improvement was caused by the best separation and the photogeneration of electron-hole on the CoAl₂O₄/ZnO surfaces. Finally, the Lagergren pseudo-first-order and the Langmuir-Hinshelwood models fit well the experimental kinetics.

Antibiotic residues in environment: antimicrobial resistance development, ecological risks, and bioremediation

The overuse of antibiotics and their disposal without processing are leading the environment and its inhabitants towards a serious health emergency. There is abundance of diverse antibiotic resistance genes and bacteria in environment, which demands immediate attention for the effective removal of antibiotics. There are physical and chemical methods for removal, but the generation of toxic byproducts has directed the efforts towards bioremediation for eco-friendly and sustainable elimination of antibiotics from the environment. Various effective and reliable bioremediation approaches have been used, but still antibiotic residues pose a major global threat. Recent developments in molecular and synthetic biology might offer better solution for engineering of microbe-metabolite biodevices and development of novel strains endowed with desirable properties. This review summarizes the impact of antibiotics on environment, mechanisms of resistance development, and different bioremediation approaches.

Photocatalytic Degradation of Cefixime Trihydrate by Bismuth Ferrite Nanoparticles

The present work was carried out to synthesize bismuth ferrite (BFO) nanoparticles by combustion synthesis, and to evaluate the photocatalytic activity of synthesized bismuth ferrite nanoparticles against cefixime trihydrate. BFO nanoparticles were successfully synthesized using bismuth (III) nitrate and iron (III) nitrate by a combustion synthesis method employing different types of fuels such as maltose, succinic acid, cinnamic acid, and lactose. The effects of the different types of fuels on the morphology and size of the bismuth ferrite nanoparticles were investigated. Characterization of the as-obtained bismuth ferrite nanoparticles was carried out by different techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-Dispersive Spectroscopy (EDS), N₂-sorption analysis, Fourier-transform infrared spectroscopy (FT-IR), and ultraviolet-visible (UV-vis) spectroscopy. Photoluminescence studies were also carried out for the various bismuth ferrite nanoparticles obtained. Degradation of cefixime trihydrate was investigated under sunlight to evaluate the photocatalytic properties of the bismuth ferrite nanoparticles, and it was found that the bismuth ferrite nanoparticles followed first-order degradation kinetics in solar irradiation in the degradation of antibiotic, cefixime trihydrate.

A Review of the Use of Semiconductors as Catalysts in the Photocatalytic Inactivation of Microorganisms

Obtaining clean and high-quality water free of pathogenic microorganisms is a worldwide challenge. Various techniques have been investigated for achieving an effective removal or inactivation of these pathogenic microorganisms. One of those promising techniques is photocatalysis. In recent years, photocatalytic processes used semiconductors as photocatalysts. They were widely studied as a green and safe technology for water disinfection due to their high efficiency, being non-toxic and inexpensive, and their ability to disinfect a wide range of microorganisms under UV or visible light. In this review, we summarized the inactivation mechanisms of different waterborne pathogenic microorganisms by semiconductor photocatalysts. However, the photocatalytic efficiency of semiconductors photocatalysts, especially titanium dioxide, under visible light is limited and hence needs further improvements. Several strategies have been studied to improve their efficiencies which are briefly discussed in this review. With the developing of nanotechnology, doping with nanomaterials can increase and promote the semiconductor’s photocatalytic efficiency, which can enhance the deactivation or damage of a large number of waterborne pathogenic microorganisms. Here, we present an overview of antimicrobial effects for a wide range of nano-photocatalysts, including titanium dioxide-based, other metal-containing, and metal-free photocatalysts. Promising future directions and challenges for materials research in photocatalytic water disinfection are also concluded in this review.

Application of Bi12ZnO20 Sillenite as an Efficient Photocatalyst for Wastewater Treatment: Removal of Both Organic and Inorganic Compounds

This work aims to synthesize and characterize a material that can be used as an effective catalyst for photocatalytic application to remove both organic and inorganic compounds from wastewater. In this context, sillenite Bi12ZnO20 (BZO) in a pure phase was synthesized using the sol-gel method. Before calcination, differential scanning calorimetry (DSC) analysis was done to determine the temperature of the formation of the sillenite phase, which was found to be 800 °C. After calcination, the phase was identified by X-ray diffraction (XRD) and then refined using the Rietveld refinement technique. The results prove that BZO crystals have a cubic symmetry with the space group I23 (N°197); the lattice parameters of the structure were also determined. From the crystalline size, the surface area was estimated using the Brunauer-Emmett-Teller (BET) method, which was found to be 11.22 m2/g. The formation of sillenite was also checked using the Raman technique. The morphology of the crystals was visualized using electron scanning microscope (SEM) analysis. After that, the optical properties of BZO were investigated by diffuse reflectance spectroscopy (DRS) and photoluminescence (PL); an optical gap of 2.9 eV was found. In the final step, the photocatalytic activity of the BZO crystals was evaluated for the removal of inorganic and organic pollutants, namely hexavalent chromium Cr(VI) and Cefixime (CFX). An efficient removal rate was achieved for both contaminants within only 3 h, with a 94.34% degradation rate for CFX and a 77.19% reduction rate for Cr(VI). Additionally, a kinetic study was carried out using a first-order model, and the results showed that the kinetic properties are compatible with this model. According to these findings, we can conclude that the sillenite BZO can be used as an efficient photocatalyst for wastewater treatment by eliminating both organic and inorganic compounds.