Search Results (79)

A strong interaction between Bi³⁺ and ZnO was used to successfully sensitize ZnO nanorods with quantum dots (QDs) of Bi₂O₃ through three different strategies. Although the Bi₂O₃ QDs had similar particle size distributions, their photocatalytic performance varied significantly, prompting the investigation of factors beyond particle size. The study revealed that the photochemical method selectively deposited Bi₂O₃ QDs onto electron-rich ZnO sites, providing a favorable pathway for efficient electron–hole separation and transfer. Consequently, abundant h⁺ and ·OH radicals were generated, which effectively degraded Rhodamine B (RhB). As demonstrated in the RhB degradation experiments, the Bi₂O₃/ZnO nanorod catalyst achieved an 89.3% degradation rate within 120 min, significantly outperforming catalysts with other morphologies. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) results indicated that the Bi₂O₃/ZnO heterostructure constructed an effective interface to facilitate the spatial separation of photogenerated charge carriers, which effectively prolonged their lifetime. The electron paramagnetic resonance (EPR) results confirmed that the ·OH radicals played a key role in the degradation process. Full article

This study focuses on the influence of prolonged ultraviolet (UV) irradiation on the mechanical properties and surface microstructure of glass fiber-reinforced plastics (GFRPs) and basalt fiber-reinforced plastics (BFRPs), which are widely used in construction and transport infrastructure. The relevance of the research lies in the need to improve the reliability of composite materials under extended exposure to harsh climatic conditions. Experimental tests were conducted in a laboratory UV chamber over 2000 h, simulating accelerated weathering. Mechanical properties were evaluated using three-point bending, while surface conditions were assessed via profilometry and microscopy. It was shown that GFRPs exhibit a significant reduction in flexural strength—down to 59–64% of their original value—accompanied by increased surface roughness and microdefect depth. The degradation mechanism of GFRPs is attributed to the photochemical breakdown of the polymer matrix, involving free radical generation, bond scission, and oxidative processes. To verify these mechanisms, FTIR spectroscopy was employed, which enabled the identification of structural changes in the polymer phase and the detection of mass loss associated with matrix decomposition. In contrast, BFRP retained up to 95% of their initial strength, demonstrating high resistance to UV-induced aging. This is attributed to the shielding effect of basalt fibers and their ability to retain moisture in microcavities, which slows the progress of photo-destructive processes. Comparison with results from natural exposure tests under extreme climatic conditions (Yakutsk) confirmed the reliability of the accelerated aging model used in the laboratory. Full article

Photochemical degradation is a major removal pathway for pharmaceutical pollutants in water, and dissolved organic matter (DOM) in water is an important factor affecting this process. This study investigates the differential effects of seasonally-varied dissolved organic matter (DOM) from Songhua River and Liao River on the photodegradation of pharmaceutical pollutants, using levofloxacin (LFX), sulfamethoxazole (SMZ), and ibuprofen (IBP) as target compounds. The results demonstrated that summer and autumn DOM inhibited the photodegradation of LFX and SMZ through light screening and dynamic quenching effects, with inhibition rates of 35.1% and 55.5%, respectively, whereas winter DOM enhanced degradation through photo-oxidation mechanisms. DOM from Songhua River and Liao River significantly promoted the photodegradation of IBP. Quenching experiments showed differences in the contributions of photochemically reactive intermediates (PPRIs) to the photodegradation of different target pollutants, with hydroxyl radicals (•OH) dominating LFX photodegradation (48.79% contribution), excited triplet states of DOM (³DOM*) dominating SMZ photodegradation (85.20% contribution), and singlet oxygen (¹O₂) dominating IBP photodegradation (79.89% contribution). The photodegradation pathways were elucidated by measuring the photodegradation by-products of the target pollutants: LFX mainly underwent piperazine ring cleavage and oxidative decarboxylation, SMZ underwent isoxazole ring opening and deamination during photodegradation, and IBP underwent photodecarboxylation and oxidation reactions. Under the influence of the DOM from the Songhua River and Liao River, the generation of multiple photodegradation by-products led to an increasing trend in the acute toxicity of target pollutants to luminescent bacteria. This investigation elucidates the dual regulatory mechanisms of natural aquatic DOM on both photo-induced degradation pathways and toxicity evolution dynamics of pharmaceutical contaminants, which is of great significance for understanding the photochemical transformation behavior and risk assessment of pharmaceutical pollutants in aquatic environments. Full article

Antimicrobial fragrances, commonly found in household and personal care products, are frequently detected in water bodies, yet their environmental fate and transformation mechanisms remain inadequately explored. This study investigates the photochemical transformation of cinnamaldehyde (CA), a representative antimicrobial fragrance, and its consequence for toxicological effects. The results showed that under UV irradiation, 94.6% CA was eliminated within 60 min, with a degradation rate of 0.059 min⁻¹. Laser flash photolysis, quenching experiments, and electron paramagnetic resonance spectra identified O₂^•− and ³CA^* as the important species, contributing 29.4% and 33.6%, respectively, to the transformation process. Additionally, singlet oxygen (¹O₂), hydroxyl radicals (^•OH), and solvated electrons (e_aq⁻) were involved in mediating the oxidation reactions. These species facilitated photoionization and oxidation, resulting in the formation of five major transformation products, including cis-cinnamyl aldehyde, cinnamic acid, styrene, 1aH-indeno [1,2-b]oxirene), and 1-Oxo-1H-indene. Most of these products were persistent, and exhibited considerable ecotoxicological risks. Specifically, the cinnamic acid and 1-Oxo-1H-indene caused severe skin irritation, while cinnamic acid induced significant eye irritation. Notably, the transformation products demonstrated sensitizing effects on human skin. This study underscores the overlooked ecotoxicological risks associated with the photochemical transformation of antimicrobial fragrances, revealing their potential to generate potent allergens and other harmful byproducts. Full article

Pharmaceutical residues are emerging contaminants of growing concern due to their persistence and poor removal efficiency in conventional wastewater treatment plants. This study evaluates UVC photolysis with type C ultraviolet radiation (UVC) and UVC/TiO₂ photocatalysis of a mixture of four pharmaceuticals—atenolol (ATL), acetaminophen (ACM), clofibric acid (CLA), and antipyrine (ANT)—commonly found in treated urban wastewater. A comprehensive kinetic model was developed to describe their degradation, taking into account the generation of reactive oxygen species (ROS): hydroxyl (HO^●), superoxide ion (O₂^●−) radicals, and singlet oxygen (¹O₂), along with their reactions with both the pharmaceuticals and dissolved organic matter. Direct quantum yields were determined as 8.05 × 10⁻³ mol·Einstein⁻¹ for ATL, 1.93 × 10⁻³ for ACM, 3.12 × 10⁻¹ for CLA, and 5.12 × 10⁻² for ANT. In addition, rate constants of the reactions between singlet oxygen and pharmaceuticals were 9.93, 1.3 × 10⁶, 1.18 × 10², and 1.14 × 10⁴ M⁻¹s⁻¹ for ATL, ACM, CLA, and ANT, respectively. Scavenger experiments confirmed the key role of the ROS involved. The model reproduces the inhibitory effect of natural organic matter in secondary effluent and, in most cases, treated, accurately predicts the concentration profiles of the pharmaceuticals. Under photocatalytic conditions (0.10 g·L⁻¹ TiO₂), all compounds were completely degraded in less than 15 min. This validated model provides a useful tool for understanding the degradation mechanisms of pharmaceutical mixtures and for supporting the design of effective water strategies based on photochemical processes. Full article

Micro-pollutants in water and wastewater pose significant risks to aquatic ecosystems due to their toxic and persistent nature. However, micro-pollutant abatement using conventional advanced oxidation processes requires high energy and chemical consumption. Therefore, a visible-light-driven photochemical system mediated by AgCl/AgBr composites (Vis-AgCl/AgBr system) was proposed to degrade tetrabromobisphenol A (TBBPA), a model micro-pollutant. The AgCl/AgBr composites, which were fabricated using a simple precipitation method, had a heterojunction structure (an interface formed between AgCl and AgBr). The AgCl/AgBr composites exhibited a narrow bandgap of 2.26 eV, which resulted in high catalytic activity under visible light. The Vis-AgCl/AgBr system efficiently degraded TBBPA in simulated and real water. The TBBPA degradation efficiency of the Vis-AgCl/AgBr system reached 99% within 30 min, which was 0.94–5.9 times higher than that by AgCl or AgBr alone. This efficient TBBPA degradation was attributable to reactive species produced in the Vis-AgCl/AgBr system, including photoelectrons (e⁻), holes (h⁺), hydroxyl radicals (•OH), and superoxide radicals (•O₂⁻). Reduction by e⁻ and oxidation by h⁺, •OH, and •O₂⁻ caused the destruction of TBBPA and the formation of bromide (Br⁻) and debrominated organic products. Debromination was anticipated to reduce the toxicity and persistency of TBBPA and increase its biodegradability. The findings of this study provide a cost-effective solution to the abatement of refractory emerging micro-pollutants in water and wastewater when sunlight can be used as a light source. Full article

With unique photochemical properties, graphitic carbon nitride (g-C₃N₄) has gained significant attention for application in photocatalytic degradation of a wide range of organic pollutants. However, its performance is limited by the rapid electron–hole recombination and the relatively weak redox capability. Substantial progress has been made in the preparation of g-C₃N₄-based photocatalysts with enhanced photocatalytic activity. This review summarizes the recent advances in strategies to improve the photocatalytic activity of g-C₃N₄-based photocatalysts and their application in the photocatalytic degradation of organic pollutants. Morphology control, doping, functionalization, metal deposition, dye sensitization, defect engineering, and construction of heterojunctions can be used to improve the photocatalytic activity of g-C₃N₄ through promoting charge carrier separation, reducing the bandgap, and suppressing charge recombination. Furthermore, a range of oxidants, such as hydrogen peroxide and persulfate, can be coupled with g-C₃N₄-based photocatalysts to enhance the generation of reactive oxygen species and boost the photocatalytic degradation of organic pollutants. Precise control over the g-C₃N₄ structure during the synthesis process remains a challenge, and further improvements are required in photocatalyst stability and the mineralization rates of organic pollutants. More research and development effort is needed to address the existing challenges, refine the design of g-C₃N₄-based photocatalysts to improve their activity, and promote their practical application in pollutant degradation. Full article

Nb-Sn, V-Sn mixed-metal oxides and Nb-Si, V-Si metal oxide–silicas were successfully synthesized through a “soft” templating method, in which appropriate amounts of metal salts (either niobium(V) chloride, or vanadium(IV) oxide sulfate hydrate or tin(II) chloride dihydrate) or tetraethyl orthosilicate (TEOS) were mixed with hexadecyltrimethylammonium chloride (HDTA) or sodium dodecyl sulfate (SDS) solutions to obtain a new series of mesoporous oxides, followed by calcination at different temperatures. As-obtained samples were characterized by SEM, TEM, XRD, and UV-Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange II (MO) under simulated sunlight irradiation. The effects of metal species and calcination temperature on the physicochemical characteristic and photocatalytic activity of the samples were investigated in detail. The results indicated that, compared to pure oxides, mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum photocatalytic discoloration rate of 97.3% (with MO initial concentration of 0.6·10⁻⁴ mol/dm³) was achieved in 300 min with the NbSiOx material, which was much higher than that of Degussa P25 under the same conditions. Additionally, the samples were tested in the photochemical oxidation process, i.e., advanced oxidation processes (AOPs) to treat the commercial non-ionic surfactant: propylene oxide ethylene oxide polymer mono(nonylphenyl) ether (N8P7, PCC Rokita). A maximum of 99.9% photochemical degradation was achieved in 30 min with the NbSiOx material. Full article

The effects of photochemical reactions induced by UV radiation in solutions of metal phthalocyanines were carried out to determine the factors that might influence the photostability of photosensitized phthalocyanines. Three different indium phthalocyanines, including the diindium triple-decker phthalocyanine, In₂Pc₃ (1), sandwich indium phthalocyanine, InPc₂ (2) and iodoindium phthalocyanine, InPcI (3) in benzene, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dichloromethane (DCM) and 1-chloronaphtalene, were studied. The rate of decay of absorption is explained by a decomposition reaction that is of first-order kinetics with respect to the phthalocyanine concentration. In general, the presence of ligand I⁻ in phthalocyanine InPcI enhances the rate of decomposition. The kinetics of the degradation process proved to depend on the molecular structure of the complex and seems to be controlled by interactions of the macrocycle bridging nitrogen atoms with the solvent molecules. The indium phthalocyanines in benzene displayed the capacity for singlet oxygen generation. Full article

Background/Objectives: The aim was to study the possibilities of biomedical application of gadolinium oxide nanoparticles (Gd₂O₃ NPs) synthesized under industrial conditions, and evaluate their physicochemical properties, redox activity, biological activity, and safety using different human cell lines. Methods: The powder of Gd₂O₃ NPs was obtained by a process of thermal decomposition of gadolinium carbonate precipitated from nitrate solution, and was studied using transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, mass spectrometry, and scanning electron microscopy (SEM) with energy dispersive X-ray analyzer (EDX). The redox activity of different concentrations of Gd₂O₃ NPs was studied by the optical spectroscopy (OS) method in the photochemical degradation process of methylene blue dye upon irradiation with an optical source. Biological activity was studied on different human cell lines (keratinocytes, fibroblasts, mesenchymal stem cells (MSCs)) with evaluation of the effect of a wide range of Gd₂O₃ NP concentrations on metabolic and proliferative cellular activity (MTT test, direct cell counting, dead cell assessment, and visual assessment of cytoarchitectonics). The test of migration activity assessment on a model wound was performed on MSC culture. Results: According to TEM data, the size of the NPs was in the range of 2–43 nm, with an average of 20 nm. XRD analysis revealed that the f Gd₂O₃ nanoparticles had a cubic structure (C-form) of Gd₂O₃ ($Ia\overline{3)}$ with lattice parameter a = 10.79(9) Å. Raman spectroscopy showed that the f Gd₂O₃ nanoparticles had a high degree of crystallinity. By investigating the photooxidative degradation of methylene blue dye in the presence of f Gd₂O₃ NPs under red light irradiation, it was found that f Gd₂O₃ nanoparticles showed weak antioxidant activity, which depended on the particle content in the solution. At a concentration of 10⁻³ M, the highest antioxidant activity of f Gd₂O₃ nanoparticles was observed when the reaction rate constant of dye photodegradation decreased by 5.5% to 9.4 × 10⁻³ min⁻¹. When the concentration of f Gd₂O₃ NPs in solution was increased to 10⁻² M upon irradiation with a red light source, their antioxidant activity changed to pro-oxidant activity, accompanied by a 15% increase in the reaction rate of methylene blue degradation. Studies on cell lines showed a high level of safety and regenerative potential of Gd₂O₃ NPs, which stimulated fibroblast metabolism at a concentration of 10⁻³ M (27% enhancement), stimulated keratinocyte metabolism at concentrations of 10⁻³ M–10⁻⁵ M, and enhanced keratinocyte proliferation by an average of 35% at concentrations of 10⁻⁴ M. Furthermore, it accelerated the migration of MSCs, enhancing their proliferation, and promoting the healing of the model wound. Conclusions: The results of the study demonstrated the safety and regenerative potential of redox-active Gd₂O₃ NPs towards different cell lines. This may be the basis for further research to develop nanomaterials based on Gd₂O₃ NPs for skin wound healing and in regenerative medicine generally. Full article

Hybrid pigments were obtained by combining zinc oxide with the anionic dye Congo red (CR), a breakthrough with significant environmental implications. By adjusting the ratio of solid mass to dye concentration, it is possible to obtain pigments with pink hues from a white solid (ZnO) through its adsorption of CR. The process involved using ZnO, prepared at 800 °C using cassava starch suspension as a suitable fuel. The oxide was characterized using XRD, SEM, and BET, and the results showed that the textural properties are typical of nanoparticles, with a size of 50.5 nm, a pore size of 3.48 nm, and a surface area of 3.03 nm, making it suitable for molecular dye removal. Controlling the adsorbent mass (in grams) and dye concentration (in mg L⁻¹) makes it possible to consistently produce hybrid pigments in various shades of pink that exhibit good thermal resistance. When dispersed in white waterborne paint, they are chemically stable in different solvents, have excellent painted surface coverage, and resist photochemical degradation. The results demonstrate technical feasibility and compatibility with the Sustainable Development Goals, particularly Goals 6, 11, 12, 14, 15, and 17, offering a promising solution for a more sustainable future. Full article

Many pharmaceuticals (PhMs), compounds for the treatment or prevention of diseases in humans and animals, have been identified as pollutants of emerging concern (PECs) due to their wide environmental distribution and potential adverse impact on nontarget organisms and populations. They are often found at significant levels in soils due to the continuous release of effluent and sludge from wastewater treatment plants (WWTPs), the release of which occurs much faster than the removal of PhMs. Although they are generally present at low environmental concentrations, conventional wastewater treatment cannot successfully remove PhMs from influent streams or biosolids. In addition, the soil application of animal manure can result in the pollution of soil, surface water, and groundwater with PhMs through surface runoff and leaching. In arid and semiarid regions, irrigation with reclaimed wastewater and the soil application of biosolids are usual agricultural practices, resulting in the distribution of a wide number of PhMs in agricultural soils. The ability to accurately study the fate of PhMs in soils is critical for careful risk evaluation associated with wastewater reuse or biosolid return to the environment. The behavior and fate of PhMs in soils are determined by a number of processes, including adsorption/desorption (accumulation) to soil colloids, biotic (biodegradation) and abiotic (chemical and photochemical degradation) degradation, and transfer (movement) through the soil profile. The sorption/desorption of PhMs in soils is the main determinant of the amount of organic chemicals taken up by plant roots. The magnitude of this process depends on several factors, such as crop type, the physicochemical properties of the compound, environmental properties, and soil–plant characteristics. PhMs are assumed to be readily bioavailable in soil solutions for uptake by plants, and such solutions act as carriers to transport PhMs into plants. Determining microbial responses under exposure conditions can assist in elucidating the impact of PhMs on soil microbial activity and community size. For all of the above reasons, soil remediation is critical when soil pollutants threaten the environment. Full article

Based on the life cycle assessment methodology, this study systematically analyzes the energy utilization of environmental waste through photocatalytic treatment and simultaneous hydrogen production. Using 10,000 tons of organic wastewater as the functional unit, the study evaluates the material consumption, energy utilization, and environmental impact potential of the photocatalytic waste synchronous hydrogen production system (specifically, the synchronous hydrogen production process of 4-NP wastewater with CDs/CdS/CNU). The findings indicate that potential environmental impacts from the photochemical treatment of environmental waste and synchronous hydrogen production primarily manifest in freshwater ecological toxicity, marine ecological toxicity, terrestrial ecological toxicity, and non-carcinogenic toxicity to humans. These ecological impacts stem from the catalyst’s adsorption and metal leaching during the photo-degradation and hydrogen production processes of environmental waste. By implementing reasonable modifications and morphological refinements to the catalyst, these effects can be mitigated while achieving enhanced efficiency in environmental waste processing and simultaneous hydrogen production. The research outcomes provide valuable insights for advancing sustainable development in green technology for environmental waste treatment and energy utilization. Full article

The present work investigates the physicochemical stability of spray paints when irradiated with artificial solar light (at spectral range 300–800 nm). This research highlights the importance of understanding the materials used in street art and public murals, recognising them as a significant component of contemporary cultural heritage. By examining the stability and degradation of spray paints toward solar light exposure, the study aims to contribute to the preservation of contemporary murals, which reflect current social and cultural narratives. A physicochemical approach was employed for the study of spray paints’ physical and thermal properties, as well as the effect of specific photochemical ageing reactions/processes. The photochemical ageing results were compared with reference (unaged) samples. Specifically, a multi-technique approach was applied using stereo microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurement, colorimetry, glossimetry, differential scanning calorimetry (DSC), UV-Vis spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and pyrolysis-GC/MS (Py-GC/MS). The photodegradation of the spray paints occurred from the first 144 h of solar light irradiation, resulting in changes in morphology, colour, gloss, roughness, and wettability. Regarding photochemical stability, ageing seems to affect the binders more than the synthetic organic pigments and the inorganic fillers. In particular, acrylic binders showed small chemical changes, whereas the alkyd, nitrocellulose, and styrene binders underwent severe chemical modification. The results suggest that simulated daylight irradiation prompts the migration of additives toward the surface of the spray paint films. In addition, the results of the analyses on the white spray paints in comparison with the coloured paints (from the same manufacturer) showed that there seems to be an active distinct photoageing mechanism involving titanium dioxide, but the whole issue needs further investigation. Full article

Evaporative water concentration takes place in arid or semi-arid environments when stationary water bodies, such as lakes or ponds, prevalently lose water by evaporation, which prevails over outflow or seepage into aquifers. Absence or near-absence of precipitation and elevated temperatures are important prerequisites for the process, which has the potential to deeply affect the photochemical attenuation of pollutants, including contaminants of emerging concern (CECs). Here we show that water evaporation would enhance the phototransformation of many CECs, especially those undergoing degradation mainly through direct photolysis and triplet-sensitized reactions. In contrast, processes induced by hydroxyl and carbonate radicals would be inhibited. Our model results suggest that the photochemical impact of water evaporation might increase in the future in several regions of the world, with no continent likely being unaffected, due to the effects of local precipitation decrease combined with an increase in temperature that facilitates evaporation. Full article