Search Results (304)

Due to its persistence and potential negative effects on ecosystems and human health, microplastic pollution in aquatic environments has become a major worldwide concern. Photocatalytic degradation is a sustainable manner to degrade microplastics to non-toxic by-products. In this review, comprehensive discussion focuses on the synergistic effects of various photocatalytic materials including TiO₂, ZnO, WO₃, graphene oxide, and metal–organic frameworks for producing heterojunctions and involving multidimensional nanostructures. Such mechanisms can include the generation of reactive oxygen species and polymer chain scission, which can lead to microplastic breakdown and mineralization. The advancements of material modifications in the (nano)structure of photocatalysts, doping, and heterojunction formation methods to promote UV and visible light-driven photocatalytic activity is discussed in this paper. Reactor designs, operational parameters, and scalability for practical applications are also reviewed. Photocatalytic systems have shown a lot of development but are hampered by shortcomings which include a lack of complete mineralization and production of intermediary secondary products; variability in performance due to the fluctuation in the intensity of solar light, limited UV light, and environmental conditions such as weather and the diurnal cycle. Future research involving multifunctional, environmentally benign photocatalytic techniques—e.g., doped composites or composite-based catalysts that involve adsorption, photocatalysis, and magnetic retrieval—are proposed to focus on the mechanism of utilizing light effectively and the environmental safety, which are necessary for successful operational and industrial-scale remediation. Full article

This study investigated the remediation of organic acid pollutants, specifically butyric acid (C₄H₈O) and valeric acid (C₅H₁₀O₂), as well as their binary mixtures in the vapor phase at various ratios. The remediation process involved the use of a continuous pilot-scale reactor. A TiO₂ catalyst was deposited on glass fiber tissue (GFT) and ultraviolet (UV) irradiation with an intensity of 20 W/m². The main objective of this study was to assess the effectiveness of the photocatalytic process by oxidizing and mineralizing a mixture of carboxylic acids in a rectangular reactor at pilot scale. This was achieved by calculating the removal efficiency and the selectivity of CO₂ (S_CO2). Each individual compound was treated separately, followed by the treatment of binary mixtures with molar fractions of 0.25, 0.5, and 0.75. The concentration of pollutants at the inlet varied between 50, 100, 150, and 200 mg/m³, while the flowrate ranged from 2 to 6 m³/h. The obtained results for the removal efficiency of butyric acid, the binary acid mixture (25% butyric acid + 75% valeric acid), and valeric acid were satisfactory, with percentages of 58%, 32%, and 41%, respectively. It is evident that the selectivity toward CO₂ is better for butyric acid compared to valeric acid and the binary carboxylic acid mixture, with values of 43.70%, 33.49%, and 21.96%, respectively, across all concentrations. A simulation model based on mass transfer and catalytic oxidation mechanisms was developed and successfully validated against the experimental data for each pollutant. Reusability tests conducted on the TiO₂ on GFT, both in its initial (clean) state and after 50 h of the photocatalytic treatment of butyric acid, showed a 15% decrease in photocatalytic efficiency. Full article

In this research, an emerging, non-metallic photocatalyst was prepared by the thermal polymerization method from three different precursors: urea, melamine, and three mixtures of melamine and cyanuric acid. Graphitic carbon nitride (g-C₃N₄) samples from urea and melamine were synthesized in a muffle furnace at three different temperatures: 450°, 500°, and 550 °C for 2 h, while the samples made of a mixture of melamine and cyanuric acid (with mass ratios of 1:1, 1:2, and 2:1) were synthesized at 550 °C for 2 h. All the samples were characterized in order to determine their chemical and physical properties, such as crystallite size and structure, and phase composition by the following techniques: Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Nitrogen adsorption/desorption isotherms were used to investigate the Brunauer, Emmett, and Teller (BET) specific surface area and Barrett–Joyner–Halenda (BJH) pore size distribution. Band gap values were determined by diffuse reflectance spectroscopy (DRS). Furthermore, adsorption and photocatalytic degradation of the local anesthetic drug procaine were monitored under UV-A, visible, and simulated solar irradiation in a batch reactor. Kinetic parameters, as well as photocatalytic mechanisms using scavengers, were determined and analyzed. The results of the photocatalysis experiments were compared to the benchmark TiO₂ Evonik Aeroxide P25. The results indicated that the g-C₃N₄ sample synthesized from urea at 500 °C for 2 h exhibited the highest degradation rate of procaine under visible light. Full article

Non-radiative decay of surface plasmon (SP) offers a novel paradigm for efficient conversion of photons into carriers. However, the narrow bandwidth of SP has been a significant obstacle to the widespread applications. Previously, research and applications mainly focused on noble metals such as Au, Ag, and Cu. In this article, we report an Ag-Al alloy material, μ-Ag₃Al, in which the surface plasmon operating bandwidth is 1.7 times that of Ag and hot carrier transport properties are comparable with those of AuAl. The results show that μ-Ag₃Al allows efficient direct interband electronic transitions from ultraviolet (UV) to near infrared range. Spherical nanoparticles of μ-Ag₃Al exhibit the localized surface plasmon resonance (LSPR) effect in the ultraviolet region. Its surface plasmon polariton (SPP) shows strong non-radiative decay at 3.36 eV, which is favorable for the generation of high-energy hot carriers. In addition, the penetration depth of SPP in μ-Ag₃Al remains high across the UV to the near-infrared range. Moreover, the transport properties of hot carriers in μ-Ag₃Al are comparable with those in Al, borophene and Au-Al intermetallic compounds. These properties can provide guidance for the design of plasmon-based photodetectors, solar cells, and photocatalytic reactors. Full article

The present work examines pure and palladium photofixed TiO₂ and binary (TiO₂/ZnO) photocatalysts for breaking down tartrazine, a food coloring agent, in distilled water. Powders with the following compositions are obtained using the sol-gel process: 100TiO₂, 10TiO₂/90ZnO, 50TiO₂/50ZnO, and 90TiO₂/10ZnO. The composite materials are analyzed using SEM-EDS, UV-Vis, DTA-TG, and X-ray diffraction. The synthesized gels are then photo-fixed with UV light to incorporate palladium ions and are also examined for tartrazine (E102) degradation. The photocatalytic tests were carried out in a cylindrical glass reactor illuminated by ultraviolet light. Compared to mixed binary catalysts, the prepared pure TiO₂ catalyst demonstrated greater activity in the photodegradation of tartrazine (E102). The further of a specific quantity of zinc oxide reduced the catalytic properties of TiO₂. The recombination of photoinduced electron-hole pairs in ZnO may account for this. In comparison to the pure samples, the co-catalytic palladium-modified gels exhibited higher photocatalytic efficiency. Heterojunction and palladium modification of the composites partially captured and transferred the electrons. Consequently, the longer lifetime of the photogenerated charges improved the catalytic activity of the palladium titanium dioxide and binary gels. Additionally, under UV light, pure and palladium photofixed TiO₂ and binary sol-gel samples displayed excellent stability for tartrazine photodegradation. Full article

The global plastic crisis, with over 400 million metric tons produced annually and minimal recycling, demands urgent solutions. Photocatalytic plastic photoreforming offers a dual benefit: converting non-recyclable plastics into hydrogen fuel and valuable chemicals using solar energy under mild conditions. This critical review highlights recent advances in photocatalyst design, including semiconductors, MOF-derived materials, and co-catalyst systems, and explores key insights into plastic degradation mechanisms and reactor configurations. Operational factors such as pH, light intensity, and flow dynamics are discussed for their impact on hydrogen yield and product selectivity. Life cycle and techno-economic assessments reveal current challenges in efficiency, scalability, and cost to illuminate the feasibility of implementing the technology at industrial scale. This study suggests that innovations in catalyst engineering, light management, and system integration provide viable paths forward. With its potential to upcycle plastic waste and contribute to low-carbon hydrogen economies, photoreforming represents a promising approach in advancing circular economy goals, especially when coupled with policy support and smart separation strategies. Full article

The increasing presence of pharmaceuticals, particularly antiretroviral drugs (ARVs), in wastewater has raised concerns regarding their environmental and health impacts. Photocatalysis, driven by advanced photocatalysts, such as coloured TiO₂, ZnO, and composites with carbon-based materials, has shown promise as an effective method for degrading these pollutants. Despite significant laboratory-scale success, challenges remain in scaling this technology for real-world applications, particularly in terms of photocatalyst stability, the formation of toxic degradation by-products, and economic feasibility. This paper explores the current state of photocatalytic degradation for ARVDs, emphasizing the need for further research into degradation pathways, the development of more efficient and cost-effective photocatalysts, and the integration of photocatalysis into hybrid treatment systems. The future of photocatalysis in wastewater treatment hinges on improving scalability, reactor design, and hybrid systems that combine photocatalysis with traditional treatment methods to ensure comprehensive pollutant removal. Innovations in catalyst design and reactor optimization are essential for advancing photocatalysis as a viable solution for large-scale wastewater treatment. Full article

There is a need to develop facile methods for the determination of UV light extinction characteristics of photocatalysts. For this task, a novel technique is proposed, applicable to dispersed photocatalyst processes of practical interest. The technique is demonstrated by obtaining fairly extensive data sets of transmittance and extinction coefficients, using TiO₂ particle suspensions at various concentrations and pH values ~3, ~5, and ~8, with light lamps of different irradiation types (i.e., UVC and UVA), immersed in the medium. To estimate the light absorption coefficient, under various tested conditions, the simplified Kubelka–Munk model is employed. The results obtained, regarding both the total light extinction and absorption coefficient, are in accord with similar literature data. The demonstrated technique is considered useful for process development studies and the design of photocatalytic reactors. Full article

Air pollution from volatile organic compounds poses significant environmental and public health issues due to their toxicity and persistence in the environment. In this context, this experimental study explored photocatalytic degradation as a promising approach for the degradation of two polluting fatty acids, butyraldehyde (BUTY) and isovaleraldehyde, utilizing a TiO₂ photocatalyst-supported nonluminous textile within a continuous planar reactor. The impact of varying airflow rates (2 to 6 m³/h), initial pollutant concentrations (10 to 60 mg/m³), and air relative humidity (5 to 90%) on oxidation performance and removal efficiency were systematically investigated. The following optimal conditions were identified: an inlet concentration of 10 mg/m³, an airflow rate of 2 m³/h, a catalyst mass of 25 g/m², a UV intensity of 2 W/m², and 50% RH. The luminous textile photocatalytic degradation exhibited notable effectiveness for BUTY removal. To enhance our understanding, a mass transfer model using the Langmuir–Hinshelwood approach as a kinetic model was developed. This modeling approach allowed us to determine kinetic adsorption and degradation constants, reasonably agreeing with the experimental data. This study provides valuable insights into applying nonluminous textile-supported TiO₂ photocatalysts for environmental pollutant removal in continuous planar reactors. Full article

The pressing need to enhance the efficiency of wastewater treatment is underscored by the significant threat that water pollution poses to human health and environmental stability. Among current remediation techniques, photocatalysis has emerged as a promising approach due to its reliance on advanced material properties. Cerium oxide’s tunable bandgap and defect engineering, combined with graphene’s high surface area, conductivity, and functionalization, synergistically enhance photocatalytic performance. This makes CeO₂-graphene composites highly promising for environmental remediation applications. This review paper systematically examines water pollution challenges and evaluates existing treatment methodologies, with a particular emphasis on CeO₂-based photocatalysts modified with graphene and its derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO). These composites demonstrate potential for superior photocatalytic performance and reactor design. Key issues, including environmental impact, stability, reusability, and compatibility of these materials with evolving technologies, are thoroughly discussed. Additionally, considerations for scaling production and commercializing these composites are addressed, suggesting avenues for future research and industrial applications. This review aims to provide a comprehensive understanding of the synergistic effects of CeO₂ and graphene-based materials, opening new possibilities for advanced clean water treatment technologies. Full article

The global imperative for clean energy solutions has positioned photocatalytic water splitting as a promising pathway for sustainable hydrogen production. This review comprehensively analyzes recent advances in TiO₂-based photocatalytic systems, focusing on materials engineering, water source effects, and scale-up strategies. We recognize the advancements in nanoscale architectural design, the engineered heterojunction of catalysts, and cocatalyst integration, which have significantly enhanced photocatalytic efficiency. Particular emphasis is placed on the crucial role of water chemistry in photocatalytic system performance, analyzing how different water sources—from wastewater to seawater—impact hydrogen evolution rates and system stability. Additionally, the review addresses key challenges in scaling up these systems, including the optimization of reactor design, light distribution, and mass transfer. Recent developments in artificial intelligence-driven materials discovery and process optimization are discussed, along with emerging opportunities in bio-hybrid systems and CO₂ reduction coupling. Through critical analysis, we identify the fundamental challenges and propose strategic research directions for advancing TiO₂-based photocatalytic technology toward practical implementation. This work will provide a comprehensive framework for exploring advanced TiO₂-based composite materials and developing efficient and scalable photocatalytic systems for multifunctional simultaneous hydrogen production. Full article

Increasing pollution and public health concerns over persistent pollutants necessitate efficient methods like photocatalytic degradation. Despite its potential in air and water treatment, the scale-up of this technology is limited due to insufficient modeling studies. This research explores the photocatalytic degradation of benzo[a]pyrene (BaP) using immobilized zinc oxide (ZnO) photocatalysts in a 500 mm length annular reactor. The reactor has a 150 mm porous ZnO domain and a UV lamp. Process variables such as the BaP concentration, residence time, surface irradiance, and catalyst zone length were modeled using computational fluid dynamics (CFD). CFD simulations using a pseudo-first-order kinetic model revealed that optimizing these parameters significantly improved the degradation efficiency. The results revealed that optimizing these parameters enhanced the degradation efficiency by over thirteen times compared to the initial setup. The increased residence time, reduced BaP concentration, and improved surface irradiance allowed for more efficient pollutant breakdown, while a longer catalyst zone supported more complete reactions. However, challenges like the high recombination rates of electron–hole pairs and susceptibility to photo-corrosion persist for ZnO. Further studies are recommended to address these challenges. Full article

This study presents the development and application of a batch-type photoelectrochemical reactor employing advanced oxidation processes (AOPs) with in situ generated TiO₂ particles for the efficient degradation of azo dyes. The reactor uses titanium sheets as electrodes, facilitating the electrochemical generation of TiO₂, which acts as a photocatalyst under UV light. This study specifically targets azo dyes frequently encountered in industrial wastewater, focusing on Brilliant Blue, Erythrosine, and Tartrazine, which together form the Navy Blue dye composition. The experimental methodology replicates real-world conditions, ensuring the results are representative of practical scenarios. Key findings demonstrate that the in situ production of TiO₂ enables effective heterogeneous photocatalysis, achieving significant dye degradation rates. This research highlights the novelty of combining in situ TiO₂ generation with a batch-type reactor, offering advantages in cost-effectiveness, scalability, and environmental impact. Comparative analysis with existing methods underscores the reactor’s potential for industrial applications, particularly in wastewater treatment. Furthermore, this study outlines the mechanistic insights into dye degradation and provides a foundation for optimizing photocatalytic processes to address environmental challenges. Full article

The sol-gel process was used to create titanium dioxide (TiO₂) nanoparticles, a nanocrystalline semiconductor. How several synthesis factors, such as titanium precursor concentration, annealing temperature, and peptization temperature, affected the structural and morphological properties of TiO₂ nanoparticles were thoroughly explored. X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), measurements of the specific surface area and pore size using the BET method, and UV-visible diffuse reflectance spectroscopy were all used in this investigation. The specific surface area determined by BET analysis decreased with increasing calcination temperature. The XRD analysis showed that a composite sample consisting mainly of anatase with minor brookite phases was obtained when the titanium precursor concentration ranged between 0.2 and 0.4 M, whereas a concentration of 0.5 M resulted in the formation of pure anatase. The photocatalytic activity of the synthesized TiO₂ powders under different operational parameters was evaluated for the common commercial textile dye, i.e., methylene blue (MB). It was experimented that the model pollutant decoloration follows the Langmuir–Hinshelwood (L-H) model. In view of this detailed research work, it was observed that the TiO₂ produced with a titanium precursor concentration of 0.3 M, a pH value of 5 during the peptization step, and an annealing temperature of 600 °C were found to be the best conditions for this catalytic degradation process. When used in conjunction with a TiO₂ concentration of 0.04 g/L and a reactor suspension pH value of 6.0, the TiO₂ catalyst produced a stunning 98% degradation of methylene blue under these circumstances. Full article

The elimination of pollutants in real water and wastewater is a challenge for the successful application of electrooxidation processes (EOPs). The presence of inorganic salts in the reaction medium is of great relevance during EOPs, with active participation in the electrochemical reactions. A revision of the reported devices used in the decontamination and disinfection of real wastewater demonstrated the main drawbacks of efficiently removing pollutants. However, the combination of photocatalytic processes with electrochemical technologies has been explored to improve overall efficiency and reduce energy consumption. A wide variety of materials, mainly metals, polymers, carbon and graphite derivatives, oxides, and MOFs, as well as their combinations, have been applied to electrodes and photoactive coatings. The deposition of the active layer has been enriched with novel designs, including porous hierarchical growth and 3D printing. The use of powerful characterization techniques allows for the study of the composition, structure, surface, and photo- and electrochemical performance of the fabricated electrodes. The simultaneous optimization of the operating conditions, parameters, and reactors must be specifically defined according to each water matrix. This approach will increase the efficiency of the whole process and contribute to cost savings. Economic contributions have been revised to calculate the cost of wastewater treatment. Full article