Removal of Cefixime from aqueous solutions via proxy electrocoagulation: modeling and optimization by response surface methodology

A focused review on photocatalytic potential of graphitic carbon nitride (g-C3N4) based metal oxide-nanostructures for effective remediation of most overused antibiotics

Researchers in the field of photocatalysis are interested in finding a solution to the problem of charge transfer and recombination in photodegradation mechanisms. The ideal photoactive catalyst would be inexpensive, environmentally friendly, easily manufactured, and highly efficient. Graphitic carbon nitride (g-C3N4) and metal oxide (MOx) based nanocomposites (g-CN/MOx) are among the photocatalysts that provide the best results in terms of charge transfer capacity, redox capabilities, and charge recombination inhibition. This article provides a comprehensive overview of the latest research on antibiotic removal from wastewater using photocatalysts based on g-C3N4 and metal oxides nanocomposites. Amoxicillin (AMX), Azithromycin (AZM), Cefixime (CFM), Ciprofloxacin (CIP), and Tetracycline (TC) are some of the common antibiotics that are the focus of this review article's examination of the photocatalytic behavior of various g-C3N4/metal oxide-based photocatalysts. A research gap demonstrates that many studies are required to use these nanocomposites for photodegradation of antibiotics. By providing a better grasp of the photocatalysis process, this review encourages scientists and researchers to develop an accurate and appropriate photocatalyst to reduce environmental risks. The main findings of this review article suggest that the cost-effective g-C3N4/MOx-based nanocomposites exhibit excellent photodegradation properties, high charge transfer, broadening light response, and charge separation. They promote enhanced charge transportation, superior electron conductivity, high redox capability, and suppressing charge recombination rate. The photodegradation mechanism involves various reactive oxygen species (ROSs), including superoxide radicals, hydroxyl radicals, and holes which promotes the photocatalysis process. The exact transportation mechanism of electrons and holes is unclear, but a rapid charge-carrier transit can significantly increase and speed up the photooxidation process.

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.

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.

Synthesis and Characterization of TiO2 Nanotubes (TiO2-NTs) with Ag Silver Nanoparticles (Ag-NPs): Photocatalytic Performance for Wastewater Treatment under Visible Light

In this work, we present the influence of the decoration of TiO₂ nanotubes (TiO₂-NTs) with Ag silver nanoparticles (Ag-NPs) on the photocatalysis of emerging pollutants such as the antibiotic diclofenac sodium. The Ag-NPs were loaded onto the TiO₂-NTs by the anodization of metallic titanium foils. Diclofenac sodium is an emerging pollutant target of the pharmaceutical industry because of its negative environmental impact (high toxicity and confirmed carcinogenicity). The obtained Ag-NP/TiO₂-NT nanocomposites were characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM), transmission spectroscopy (TEM), and X-ray photoelectron spectroscopy (XPS). In order to study the photocatalytic behavior of Ag-NPs/TiO₂-NTs with visible cold LEDs, the possible photocatalytic mechanism of antibiotic degradation with reactive species (O₂°⁻ and OH°) was detailed. Moreover, the Langmuir–Hinshelwood model was used to correlate the experimental results with the optimized catalyst. Likewise, reuse tests showed the chemical stability of the catalyst.

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.