g-C3N4/Ca2Fe2O5 heterostructures for enhanced photocatalytic degradation of organic effluents under sunlight

Brownmillerite Calcium Ferrite, a Promising Perovskite-Related Material in the Degradation of a Tight Dye under Ambient Conditions

Evaluation of effective and low-cost materials as catalysts to combat the threat of pollution is a significant and growing trend. With this aim, we have synthesized calcium ferrite brownmillerite by wet preparation approach as a catalyst for pollution. The structural analysis is established by the X-ray diffraction of Ca2 Fe2 O5 , whereas the tetrahedral and octahedral sites band stretching for ferrite specimen has been deduced using FTIR. The bandgap energy has been estimated by the Tauc relation (2.17 eV). Ca2 Fe2 O5 brownmillerite exhibits a BET surface area of 10 m2 /g and a BJH pore volume of 0.121 cm3 /g with the average particle size of 70 nm. Importantly, the alizarin Red S dye degradation has been studied using the prepared ferrite catalyst, under dark ambient conditions and without the presence of any acidic or basic additives. Degradation is also supported by both FTIR and TOC analysis. Surface properties of brownmillerite Ca2 Fe2 O5 have been characterized using electronic spectroscopy and CO2 temperature programmed desorption (TPD) analysis and revealed that the basic surface of brownmillerite Ca2 Fe2 O5 offers active sites that are suitable for degradation processes. All results show that the preparation of brownmillerite Ca2 Fe2 O5 via the Pechini method is suitable to produce fine surfaces and pores with nanosized particles.

A Sustainable and Regenerative Process for the Treatment of Textile Effluents Using Nonphotocatalytic Water Splitting by Nanoporous Oxygen-Deficient Ferrite

Water is crucial for life. Being the world's third-largest industry, the textile industry pollutes 93 billion cubic meters of water each year. Only 28% of textile wastewater is treated by lower- to middle-income countries due to the costly treatment methods. The present work demonstrates the utilization of surface oxygen defects and nanopores in Mg0.8Li0.2Fe2O4 (Li-MgF) to treat textile effluents by a highly economical, scalable, and eco-friendly process. Nanoporous, oxygen-deficient Li-MgF splits water by a nonphotocatalytic process at room temperature to produce green electricity as hydroelectric cell. The adsorbent Li-MgF can be easily regenerated by heat treatment. A 70-90% reduction in the UV absorption intensity of adsorbent-treated textile effluents was observed by UV-visible spectroscopy. The oxygen defects on Li-MgF surface and nanopores were confirmed by X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller (BET) measurements, respectively. To analyze the adsorption mechanism, three known organic water-soluble dyes, brilliant green, crystal violet, and congo red, were treated with nanoporous Li-MgF. The dye decolorization efficiency of Li-MgF was recorded to be 99.84, 99.27, and 99.31% at 250 μM concentrations of brilliant green, congo red, and crystal violet, respectively. The results of Fourier transform infrared (FTIR) spectroscopy confirmed the presence of dyes on the material surface attached through hydroxyl groups generated by water splitting on the surface of the material. Total organic carbon analysis confirmed the removal of organic carbon from the dye solutions by 82.8, 77.0, and 46.5% for brilliant green, Congo red, and crystal violet, respectively. Based on the kinetic and isotherm models, the presence of a large number of surface hydroxyl groups on the surface of the material and OH- ions in solutions generated by water splitting was found to be responsible for the complete decolorization of all of the dyes. Adsorption of chemically diverse dyes by the nanoporous, eco-friendly, ferromagnetic, economic, and reusable Li-MgF provides a sustainable and easy way to treat textile industry effluents in large amounts.

Sustainable, efficient, and synergistic photocatalytic degradation toward organic dyes and formaldehyde gas via Cu2O NPs@wood

Cuprous oxide (Cu2O) nanoparticles (NPs) was anchored on wood by simple spraying method, then both soft and hard wood has been endowed efficient function photocatalytic degradation toward organic dyes and formaldehyde gas synergistically. The best recycle ability of wood based photocatalyst toward organic pollutants was achieved, which was characterized by photocatalytic degradation efficiency of methylene blue (MB) more than 95% after 100 cycles, and formaldehyde gas over 85% after 60 cycles. Cu2O NPs@wood performed much lower forbidden bandwidth (Eg), which accelerated to generate much more radical of e- and finally promoted the capacity of photocatalytic degradation. The proposed Cu2O NPs@wood catalysts has potential to be applied both in the field of wastewater and air pollution remediation.

Radiation synthesis and photocatalytic performance of floated graphene oxide decorated ZnO/ alginate-based beads for methylene blue degradation under visible light irradiation

Organic dye contamination, emanating from pharmaceutical, paper, and textile industries into water resources, severely threatens marine and human life even at low concentrations. Photocatalysis is one of the most important remediation techniques that decolorize water by employing the power of light. In this work, the development of floated beads of Sodium Alginate/hydroxyethyl methacrylate (Alg-g-HEMA) encompass graphene oxide (GO) decorated Zinc oxide (ZnO) utilizing ionizing radiation was designed to function as a photocatalyst when exposed to visible light. Floatability was induced using calcium carbonate. GO was sonochemically decorated with ZnO nanoparticles and the yield was characterized using XRD, FTIR, TEM, SEM, and EDX techniques. Optical characteristics of the developed nanostructure were performed using UV-Vis spectrophotometry. The photocatalytic activity of the floated (Alg-g-HEMA)-ZnO@GO beads was assessed for the photo decolorization of methylene blue dye (MB) under visible light. The upshot of operational factors such as photocatalyst dose, pH, initial dye concentration, and irradiation time on the decolorization of MB was examined. It was observed that 1 g of the developed (Alg-g-HEMA)-ZnO@GO photocatalyst was able to decolorize 1000 ml of 20 ppm of MB within 150 min at pH 9. In terms of kinetics, photo-decolorization follows Langmuir Hinshelwood pseudo-first order.

Facile preparation of porphyrin@g-C3N4/Ag nanocomposite for improved photocatalytic degradation of organic dyes in aqueous solution

In the quest of improving the photocatalytic efficiency of photocatalysts, the combination of two and more semiconductors recently has garnered significant attention among scientists in the field. The doping of conductive metals is also an effective pathway to improve photocatalytic performance by avoiding electron/hole pair recombination and enhancing photon energy absorption. This work presented a design and fabrication of porphyrin@g-C₃N₄/Ag nanocomposite using acid-base neutralization-induced self-assembly approach from monomeric porphyrin and g-C₃N₄/Ag material. g-C₃N₄/Ag material was synthesized by a green reductant of Cleistocalyx operculatus leaf extract. Electron scanning microscopy (SEM), X-ray diffraction (XRD), FT-IR spectroscopy, and UV-vis spectrometer were utilized to analyse the properties of the prepared materials. The prepared porphyrin@g-C₃N₄/Ag nanocomposite showed well integration of porphyrin nanostructures on the g-C₃N₄/Ag's surface, in which porphyrin nanofiber was of the diameter in nanoscales and the length of several micrometers, and Ag NPs had an average particle size of less than 20 nm. The photocatalytic behavior of the resultant nanocomposite was tested for the degradation of Rhodamine B dye, which exhibited a remarkable RhB photodegrading percentage. The possible mechanism for photocatalysis of the porphyrin@g-C₃N₄/Ag nanocomposite toward Rhodamine B dye was also proposed and discussed.

Immobilization of a TiO2-PEDOT:PSS hybrid heterojunction photocatalyst for degradation of organic effluents

Heterojunction photocatalysts have recently emerged for use in degradation of organic pollutants, typically being suspended in effluent solution to degrade it. Post degradation, the catalyst must be removed from the treated solution, which consumes both energy and time. Moreover, the separation of nano catalysts from the treated solution is challenging. In the present work, we explore fabrication of immobilized TiO₂-PEDOT:PSS hybrid heterojunction catalysts with the support of a PVA (polyvinyl alcohol) matrix. These photocatalytic films do not require any steps to separate the powdered catalyst from the treated water. While the PVA-based films are unstable in water, their stability could be significantly enhanced by heat treatment, enabling efficient removal of organic effluents like methylene blue (MB) and bisphenol-A (BPA) from the aqueous solution under simulated sunlight irradiation. Over 20 cycles, the heterojunction photocatalyst maintained high photocatalytic activity and showed excellent stability. Hence, an immobilization of the TiO₂-PEDOT:PSS hybrid heterojunction is suggested to be beneficial from the viewpoint of reproducible and recyclable materials for simple and efficient wastewater treatment.

Enhanced non-linear optical properties of porphyrin-based polymers covalently functionalized with graphite phase carbon nitride

In our work, a flurry of original porphyrin-based polymers covalently functionalized g-C₃N₄ nanohybrids were constructed and nominated as PPorx-g-C₃N₄ (x = 1, 2 and 3) through click chemistry between porphyrin-based polymers with alkyne end-groups [(PPorx-C≡CH (x = 1, 2 and 3)] and azide-functionalized graphitic carbon nitride (g-C₃N₄-N₃). Due to the photoinduced electron transfer (PET) between porphyrin-based polymers [PPorx (x = 1, 2 and 3)] group and graphite phase carbon nitride (g-C₃N₄) group in PPorx-g-C₃N₄ nanohybrids, the PPorx-g-C₃N₄ nanohybrids exhibited better non-linear optical (NLO) performance than the corresponding PPorx-C≡CH and g-C₃N₄-N₃. It found that the imaginary third-order susceptibility (Im [χ⁽³⁾]) value of the nanohybrids with different molecular weight (MW) of the pPorx group in the nanohybrids ranged from 2.5×10³ to 7.0 × 10³ g mol^-1 was disparate. Quite interestingly, the Im [χ⁽³⁾] value of the nanohybrid with a pPorx group's MW of 4.2 × 10³ g mol^-1 (PPor2-g-C₃N₄) was 1.47 × 10^-10 esu, which exhibited the best NLO performance in methyl methacrylate (MMA) of all nanohybrids. The PPorx-g-C₃N₄ was dispersed in polymethyl methacrylate (PMMA) to prepare the composites PPorx-g-C₃N₄/PMMA since PMMA was widely used as an alternative to glass. PPor2-g-C₃N₄/PMMA showed the excellent NLO performance of all nanohybrids with the Im [χ⁽³⁾] value of 2.36 × 10^-10 esu, limiting threshold of 1.71 J/cm², minimum transmittance of 8% and dynamic range of 1.09 in PMMA, respectively. It suggested that PPorx-g-C₃N₄ nanohybrids were potential outstanding NLO materials.

Revealing Resistive Switching Mechanism in CaFeOx Perovskite System with Electroforming-Free and Reset Voltage-Controlled Multilevel Resistance Characteristics

Recently, perovskite (PV) oxides with ABO₃ structures have attracted considerable interest from scientists owing to their functionality. In this study, CaFeO_x is introduced to reveal the resistive switching properties and mechanism of oxygen vacancy transition in PV and brownmillerite (BM) structures. BM-CaFeO_2.5 is grown on an Nb-STO conductive substrate epitaxially. CaFeO_x exhibits excellent endurance and reliability. In addition, the CaFeO_x also demonstrates an electroforming-free characteristic and multilevel resistance properties. To construct the switching mechanism, high-resolution transmission electron microscopy is used to observe the topotactic phase change in CaFeO_x . In addition, scanning TEM and electron energy loss spectroscopy show the structural evolution and valence state variation of CaFeO_x after the switching behavior. This study not only reveals the switching mechanism of CaFeO_x , but also provides a PV oxide option for the dielectric material in resistive random-access memory (RRAM) devices.

TiO2-Based Heterostructure Containing g-C3N4 for an Effective Photocatalytic Treatment of a Textile Dye

Water pollution has become a serious environmental issue. The textile industries using textile dyes are considered to be one of the most polluting of all industrial sectors. The application of solar-light semiconductor catalysts in wastewater treatment, among which TiO2 can be considered a prospective candidate, is limited by rapid recombination of photogenerated charge carriers. To address these limitations, TiO2 was tailored with graphitic carbon nitride (g-C3N4) to develop a heterostructure of g-C3N4@TiO2. Herein, a simple hydrothermal synthesis of TiO2@g-C3N4 is presented, using titanium isopropoxide (TTIP) and urea as precursors. The morphological and optical properties and the structure of g-C3N4, TiO2, and the prepared heterostructure TiO2@g-C3N4 (with different wt.% up to 32%), were analyzed by various laboratory methods. The photocatalytic activity was studied through the degradation of methylene blue (MB) aqueous solution under UV-A and simulated solar irradiation. The results showed that the amount of g-C3N4 and the irradiation source are the most important influences on the efficiency of MB removal by g-C3N4@TiO2. Photocatalytic degradation of MB was also examined in realistic conditions, such as natural sunlight and different aqueous environments. The synthesized g-C3N4@TiO2 nanocomposite showed superior photocatalytic properties in comparison with pure TiO2 and g-C3N4, and is thus a promising new photocatalyst for real-life implementation. The degradation mechanism was investigated using scavengers for electrons, photogenerated holes, and hydroxyl radicals to find the responsible species for MB degradation.

Facile synthesis of broom stick like FeOCl/g-C3N5 nanocomposite as novel Z-scheme photocatalysts for rapid degradation of pollutants

A simple and cost-effective route has been utilized for the preparation of a novel lamellar structured FeOCl/g-C₃N₅ nanocomposite as Z-scheme photocatalyst. The preparation method was performed under the ambient temperature conditions without any hazardous chemicals. Various characterization techniques, namely XRD, FESEM, TEM, FT-IR, UV-Vis, DRS, and PL were carried out to analyse the nanocomposite for confirmation of FeOCl/g-C₃N₅ nanocomposite. To evaluate its and visible light degradation performances tetracycline (T-C) was used as target pollutant. Among the optimum loading for the g-C₃N₅ incorporated FeOCl binary nanocomposites, the g-C₃N₅/FeOCl exhibited a superlative degradation performance toward the T-C antibiotic pollutant. The results confirmed that 95% of T-C was degraded within 40 min under photodegradation mechanism. The improved photodegradation performance in degradation of T-C was mainly due to the reduction in electron-hole recombination, broadening in the light absorption by g-C₃N₅ incorporation, which leads to shortening the degradation time. Furthermore, the hydroxyl and superoxide radicals played a major role in the photodegradation process and the possible mechanism was elucidated and proposed. The present work implies a novel, sustainable, and efficient Z-scheme system that may deliver a convenient method for environment remediation.

Magnetic visible-light activated photocatalyst ZnFe2O4/BiVO4/g-C3N4 for decomposition of antibiotic lomefloxacin: Photocatalytic mechanism, degradation pathway, and toxicity assessment

Magnetic ZnFe₂O₄/BiVO₄/g-C₃N₄ (ZBC) composites were prepared via a facile hydrothermal and calcination method for the degradation of a representative antibiotics lomefloxacin (LFX) under visible light irradiation. The optimal photocatalyst ZBC-10 with a ZnFe₂O₄:BiVO₄:g-C₃N₄ mass ratio of 1:8:10 performed 96.1% removal of LFX after 105 min of illumination. The excellent performance is ascribed to the effective construction of heterojunctions and its capacity to form a double Z-scheme charge transmission pathway among the hosts in ZBC-10. The composite enhanced the separation and migration of photoexcited charge carriers and the effective generation of multiple active radicals including ·OH, ·O₂^-, and ¹O₂. The LFX degradation process, identified based on an integrated HPLC-Q-TOF-MS analysis and density functional theory computation of the Fukui indices, comprised of three pathways initiated by the opening of the piperazinyl ring, separation of piperazinyl and quinoline moieties, and cleavage of the pyridine ring on the quinoline moieties. Ecotoxicological evaluation confirmed the reduced toxicity of transformation intermediates over photocatalysis. Convenient magnetic recovery, high performance, and high recyclability made ZBC-10 a promising visible-light-activated photocatalyst for practical implementation in eliminating antibiotics from wastewater.

Review on Methylene Blue: Its Properties, Uses, Toxicity and Photodegradation

The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.