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Photobromination of toluene derivatives using blue LED (454 nm) or UV LEDs (365, 385, 395 nm) with aqueous HBr and NaOCl·5H2O in trifluoromethyl benzene afforded the corresponding benzoic acids derivatives. The intermediates were (dibromomethyl)benzene derivatives, isolated in a nitrogen atmosphere. The dibromomethyl benzene derivatives afforded the corresponding aldehydes. After the reaction with HBr, the aqueous layer could be recovered and reused. [ABSTRACT FROM AUTHOR]

In the present study, biocomposite materials were created by incorporating biochar (BC) at rates of 1, 2.5, and 5 wt.% into a poly(butylene succinate) (PBSu) matrix using a two-stage melt polycondensation procedure in order to provide understanding of the aging process. The biocomposites in film form were exposed to UV irradiation for 7, 14, and 21 days. Photostability was examined by several methods, such as Fourier transform infrared spectroscopy (FTIR), which proved that new carbonyl and hydroxyl groups were formed during UV exposure. Moreover, Differential Scanning Calorimetry (DSC) measurements were employed to record the apparent UV effect in their crystalline morphology and thermal transitions. According to the molecular weight measurements of composites, it was apparent that by increasing the biochar content, the molecular weight decreased at a slower rate. Tensile strength tests were performed to evaluate the deterioration of their mechanical properties during UV exposure, while Scanning Electron Microscopy (SEM) images illustrated the notable surface alternations. Cracks were formed at higher UV exposure times, to a lesser extent in PBSu/BC composites than in neat PBSu. Furthermore, the mechanism of the thermal degradation of neat PBSu and its biocomposites prior to and upon UV exposure was studied by Pyrolysis–Gas Chromatography/Mass Spectrometry (Py–GC/MS). From all the obtained results it was proved that biochar can be considered as an efficient UV-protective additive to PBSu, capable of mitigating photodegradation. [ABSTRACT FROM AUTHOR]

[Display omitted] The highly efficient photo-oxidation of alcohols has sparked significant potential to cope with environmental pollution and the ever-increasing energy crisis. This study reports a unique Ti 3 C 2 /BiOBr (TB) heterojunction with a rich inter-face based on in situ exfoliation of MXene and subsequently anchored onto BiOBr sheets. The TB nano-composites exhibited substantially improved photo-catalytic activity towards the photo-oxidation of benzyl alcohol (BA) to benzaldehyde and achieved a formation rate of 1.73 mmol g−1 h−1, greater than pristine BiOBr. The ultra-thin inter-facial contact boosted the oxygen vacancies (O v) and Ti3+ and possessed the most negative adsorption energy, which boosted the transfer and separation of inter-facial charge carriers and the adsorption and dissociation of BA. Overall, the successful synthesis of TB composite, along with its exceptional photo-catalytic performance, offers valuable insights for applications in green chemistry and environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] Solar-light driven oxidation of benzylic alcohols over photocatalysts endows significant prospects in value-added organics evolution owing to its facile, inexpensive and sustainable process. However, the unsatisfactory performance of actual photocatalysts due to the inefficient charge separation, low photoredox potential and sluggish surface reaction impedes the practical application of this process. Herein, we developed an innovative Z-Scheme Cs 3 BiBr 9 nanoparticles@porous C 3 N 4 tubes (CBB-NP@P-tube-CN) heterojunction photocatalyst for highly selective benzyl alcohol oxidation. Such composite combining increased photo-oxidation potential, Z-Scheme charge migration route as well as the structural advantages of porous tubular C 3 N 4 ensures the accelerated mass and ions diffusion kinetics, the fast photoinduced carriers dissociation and sufficient photoredox potentials. The CBB-NP@P-tube-CN photocatalyst demonstrates an exceptional performance for selective photo-oxidation of benzylic alcohol into benzaldehyde with 19, 14 and 3 times higher benzylic alcohols conversion rate than those of C 3 N 4 nanotubes, Cs 3 Bi 2 Br 9 and Cs 3 Bi 2 Br 9 @bulk C 3 N 4 photocatalysts, respectively. This work offers a sustainable photocatalytic system based on lead-free halide perovskite toward large scale solar-light driven value-added chemicals production. [ABSTRACT FROM AUTHOR]

Information on the detection of the presence and potential for degradation of synthetic polymers (SPs) under various environmental conditions is of increasing interest and concern to a wide range of specialists. At this stage, there is a need to understand the relationship between the main participants in the processes of (bio)degradation of SPs in various ecosystems (reservoirs with fresh and sea water, soils, etc.), namely the polymers themselves, the cells of microorganisms (MOs) participating in their degradation, and humic substances (HSs). HSs constitute a macrocomponent of natural non-living organic matter of aquatic and soil ecosystems, formed and transformed in the processes of mineralization of bio-organic substances in environmental conditions. Analysis of the main mechanisms of their influence on each other and the effects produced that accelerate or inhibit polymer degradation can create the basis for scientifically based approaches to the most effective solution to the problem of degradation of SPs, including in the form of microplastics. This review is aimed at comparing various aspects of interactions of SPs, MOs, and HSs in laboratory experiments (in vitro) and environmental investigations (in situ) aimed at the biodegradation of polymers, as well as pollutants (antibiotics and pesticides) that they absorb. Comparative calculations of the degradation velocity of different SPs in different environments are presented. A special place in the analysis is given to the elemental chemical composition of HSs, which are most successfully involved in the biodegradation of SPs. In addition, the role of photo-oxidation and photoaging of polymers under the influence of the ultraviolet spectrum of solar radiation under environmental conditions on the (bio)degradation of SPs in the presence of HSs is discussed. [ABSTRACT FROM AUTHOR]

Abstract The knowledge of the formation of gas-phase carcinogenic acetonitrile (CH3CN) is limited in interstellar, troposphere, and combustion mediums; thus, its formation and fate are of great importance for all these gas-phase environments when accessing its toxicity and its wide range of applications. In this work, we propose a mechanism for the formation of CH3CN from the reaction of OH/O2 on ethanimine (CH3CH=NH) using ab initio/Density Functional Theory (DFT) potential energy surface in combination with microcanonical variational transition state theory (µVTST) and Ramsperger–Kassel–Marcus (RRKM)/master equation (ME) simulation to predict the rate constants and branching fraction in the temperature range of 100 K to 1000 K and pressure range of 0.0001 bar to 100 bar. The reaction starts with cis (Z) and trans (E) CH3CH=NH isomer with OH radical followed by spontaneous formation via pre-reactive complex, forming the carbon and nitrogen-centered radicals. The O2 radical then attacks the carbon and nitrogen-centered radicals to form acetonitrile (CH3CN) and HO2 radicals. The results show that N–H and C–H dominate the H-atoms abstraction by OH radicals is similar to its isoelectronic analogous reaction system, i.e., CH3CHO + OH/O2 and CH3CHCH2 + OH/O2 and similar to methanimine (CH2NH) systems. The calculated rate constants for OH-initiated oxidation of CH3CH=NH are in the range of ~ 10–11 cm3 molecule−1 s−1 (at 300 K) and are in very good agreement with previous experimental values of its isoelectronic reaction system. The atmospheric lifetime due to the loss of CH3CHNH by OH radical (10 to 11 h) is in very good agreement with the similar pollutants in the troposphere temperature range between 200 and 320 K. The results indicate that its contribution to global warming is negligible. However, the formation of products such as CH3CN may interact with other atmospheric species, which could lead to the production of potentially hazardous compounds such as cyanogen (N2C2) and hydrogen cyanide (HCN).

Temperature-dependent rate coefficients for the reactions of 2-methyl tetrahydrofuran (MTHF) with Cl atoms in the temperature range of 268–343 K at atmospheric pressure were measured using the relative-rate method. Ethylene and propane were used as reference compounds. Quantitative analysis of the post-photolysis reaction mixture was conducted using a gas chromatograph paired with a flame ionization detector (GC-FID). A gas chromatograph connected to a mass spectrometer (GC–MS) was employed for the purpose of qualitative analysis. In the experimental temperature range, the derived Arrhenius expression for the title reaction is represented by the equation k M T H F + C l Expt 268 - 343 K = (1.48 ± 0.13) × 10 - 12 × e x p 1474.51 ± 25.16 T cm3 molecule−1 s−1. In addition to our experimental findings, we conducted computational calculations employing the CCSD(T)//BHandHLYP/6–31 + G(d,p) level of theory to complement our study. The canonical transition state theory (CTST) was utilized to compute the rate coefficients at 250–400 K and 760 Torr. The Arrhenius expression for the theoretically calculated "k" values is found to be k M T H F + C l Theory 250 - 400 K = (1.51 ± 0.10) × 10 - 12 × e x p 1544.97 ± 22.14 T cm3 molecule−1 s−1. The local reactivity parameters, such as Fukui functions ( f r 0 ), local softness ( s r 0 ), and global softness (S ) were also calculated theoretically to understand the site-specific reactivity trend of MTHF towards Cl atoms. The atmospheric implications, branching ratios, degradation mechanism, and feasibility of the reaction are discussed in this study. [ABSTRACT FROM AUTHOR]

A photocatalyzed oxidation of functionalized cyclobutanones to access γ‐lactones has been performed in acetonitrile at room temperature, using anthraquinone derivatives as catalysts in the presence of TFA. The best reaction results were obtained by using 3 mol % of 9,10‐anthraquinone as a catalyst under 370 nm irradiation in an O2 environment. The scope and the limitations of this reaction have been investigated using both 2‐ and 3‐substituted cyclobutanones, as well as enantiopure ketones, to obtain full preservation of their stereochemical identity after the oxidation. The process furnishes in most cases the desired compounds with high purity after catalyst removal by simple filtration, and reducing the production of solvents waste. [ABSTRACT FROM AUTHOR]

The optimization of photoluminescence (PL) spectral bandwidths in InP‐based colloidal quantum dots (QDs) faces limitations with traditional synthetic methods. This study introduces a novel approach utilizing light‐induced thiolate ligand detachment to selectively precipitate QDs within an ensemble, triggered by photons whose energy matches the red tail of the band‐edge absorption peak. We demonstrate that incorporating benzoquinone as an electron acceptor under inert conditions crucially enhances the efficiency of photoexcited hole‐induced ligand detachment. Through careful optimization of laser exposure conditions, we successfully narrowed the PL bandwidth of InP/ZnSe/ZnS QDs from 39 to 35 nm. Our findings offer significant insights into the development of high‐performance QD‐based displays, promising advancements in color purity. [ABSTRACT FROM AUTHOR]

Abstract: Aim Photochemical mineralization is a significant pathway for the total oxidation of Dissolved Organic Carbon (DOC) in aquatic ecosystems. The concentration of DOC, watercolor, solar radiation intensity, diagenetic state of DOC, and oxygen availability are known regulating factors influencing the DOC photochemical mineralization process. However, these studies have not yet assessed the importance of these regulatory factors under extreme conditions of DOC concentration and watercolor. The aims of this study were: (1) to optimize methodological parameters for investigating the photo-degradation process in tropical humic/super-humic aquatic ecosystems; (2) to evaluate the relative importance of regulatory factors influencing photochemical mineralization in tropical humic/super-humic ecosystems; and (3) to measure photochemical mineralization rates in 20 coastal tropical humic/super-humic ecosystems and comparing them with available data worldwide. Methods Three types of DOC exposure experiments were conducted: (i) exposing water samples to different solar radiation intensities, (ii) exposing water samples of the same origin but with different DOC concentrations (dilutions) to sunlight and (iii) exposing water samples from a gradient of 20 environments with distinct characteristics to sunlight. Results Our results revealed that oxygen concentration became limiting for the photochemical mineralization process in experiments investigating super-humic ecosystems. Watercolor exhibited ambiguous effects on photochemical mineralization; in environments with colored-DOC, increased DOC watercolor favored higher potential photochemical mineralization rates, whereas in super-humic environments, increased DOC watercolor reduced the photochemical mineralization potential due to DOC self-shading. Conclusions We emphasize that the measured results in this study represent the highest values of photochemical mineralization ever recorded in the literature.

Green nanocomposite of ZnO supported into polyaniline/bentonite hybrid structure (Zn@/PA/BE) was synthesised and characterised and assessed as a multifunctional photocatalyst of 1.86 eV as bandgap energy. The Zn@/PA/BE catalyst was applied in the oxidation of the levofloxacin (LV) residuals in water in the presence of visible light. The recognised oxidation results demonstrate significant enhancement in photocatalytic activity by using the polyaniline/bentonite composite as a carrier for ZnO catalyst. Using the Zn@/PA/BE at 0.5 g/L as dosage resulted in complete oxidation for 10, 20, 30, 40, and 50 mg/L after illumination intervals of 25, 40, 60, 70, and 85 min, respectively. This was confirmed by the significant declination in the TOC content of the treated sample (10 mg/L) until the complete removal after 45 min reflecting the complete degradation and mineralisation. The formed secondary organic compounds during the incomplete oxidation reactions were identified. The intermediate compounds suggested oxidation pathways of carboxylation/de-carboxylation, hydroxylation, de-methylation, de-piperazinylation, and defluorination mechanisms. The hydroxyl radicals were detected as the most effective oxidising species during the reactions based on the active trapping tests and probe molecule investigation. The recyclability experiments reflected the significant stability and reusability of Zn@/PA/BE as a photocatalyst during the oxidation of LV molecules. [ABSTRACT FROM AUTHOR]

The effect of moisture on the photo-oxidative degradation of polyamide-6 (PA-6) was studied by analyzing the mechanical response after two different accelerated aging procedures. In the first aging procedure, the PA-6 was only exposed to ultra-violet (UV) radiation at 60 ∘ C. In the second procedure, the same duration of UV radiation was periodically interrupted while the relative humidity was raised to 100%. Diffusion-limited and nominally homogeneous degradation conditions were investigated using bulk and film specimens, respectively. Accelerated UV aging reduced the ductility of PA-6, but the additional hygrothermal exposure had no effect on the ductility or strength, indicating that humidity did not influence the photo-oxidation of PA-6. This finding contrasts with previous studies that found thermo-oxidation of PA-6 was accelerated by moisture. [ABSTRACT FROM AUTHOR]

Background: Cooling towers are specialized heat exchanger devices in which air and water interact closely to cool the water's temperature. However, the cooling water contains organic nutrients that can cause microbial corrosion (MC) on the metal surfaces of the tower. This research explores the combined wastewater treatment approach using electrochemical-oxidation (EO), photo- oxidation (PO), and photoelectrochemical oxidation (PEO) to contain pollutants and prevent MC. Methods: The study employed electro-oxidation, a process involving direct current (DC) power supply, to degrade wastewater. MC studies were conducted using weight loss assessments, scanning electron microscopy (SEM), and x-ray diffraction (XRD). Results: After wastewater is subjected to electro-oxidation for 4 h, a notable decrease in pollutants was observed, with degradation efficiencies of 71, 75, and 96%, respectively. In the wastewater treated by PEO, microbial growth is restricted as the chemical oxygen demand decreases. Discussion: A metagenomics study revealed that bacteria present in the cooling tower water consists of 12% of Nitrospira genus and 22% of Fusobacterium genus. Conclusively, PEO serves as an effective method for treating wastewater, inhibiting microbial growth, degrading pollutants, and protecting metal from biocorrosion. [ABSTRACT FROM AUTHOR]

Colorizing metals using micrometer and nanometer scale surface modifications has been vastly investigated and presents many advantages for applications across scientific and technological fields. By tuning the surface chemical composition or controlling its morphology, it is possible to produce a wide range of chromatic effects. Ultrafast laser processing presents here an interesting asset, as it allows to simultaneously provide chemical and morphological modifications at the micro‐scale in a single step. In this article, the composite colorization of copper surfaces with mW‐class average power deep ultraviolet (DUV) femtosecond laser pulses is demonstrated. The advantages of this setup are twofold: first, thanks to the increased absorption of copper in the DUV, the technique allows scaling down the requirement for laser power. Second, under ultrafast short‐wavelength illumination molecular oxygen bond‐breaks occur, enhancing the oxidation rate of the copper. The technique allows for highly controllable and efficient copper oxidation with the irradiation parameters. Taking these two effects into account, the generation of a wide spectrum of colors—from dark blue to shiny red—is demonstrated, and the role of the surface oxidation rate, the laser fluence, and laser scanning strategies in the colorization of copper surfaces employing DUV lasers is discussed. [ABSTRACT FROM AUTHOR]

Many of the highest priority targets in a wide range of disease states are difficult‐to‐drug proteins. The development of reversible small molecule inhibitors for the active sites of these proteins with sufficient affinity and residence time on‐target is an enormous challenge. This has engendered interest in strategies to increase the potency of a given protein inhibitor by routes other than further improvement in gross affinity. Amongst these, the development of catalytic protein inhibitors has garnered the most attention and investment, particularly with respect to protein degraders, which catalyze the destruction of the target protein. This article discusses the genesis of the burgeoning field of catalytic inhibitors, the current state of the art, and exciting future directions. [ABSTRACT FROM AUTHOR]

By planting LEDs on the surfaces of orifice baffles, a novel batch oscillatory baffled photoreactor (OBPR) together with polymer-supported Rose Bengal (Ps-RB) beads are here used to investigate the reaction kinetics of a photo-oxidation reaction between α-terpinene and singlet oxygen (1O2). In the mode of NMR data analysis that is widely used for this reaction, α-terpinene and ascaridole are treated as a reaction pair, assuming kinetically singlet oxygen is in excess or constant. We have, for the first time, here examined the validity of the method, discovered that increasing α-terpinene initially leads to an increase in ascaridole, indicating that the supply of singlet oxygen is in excess. Applying a kinetic analysis, a pseudo-first-order reaction kinetics is confirmed, supporting this assumption. We have subsequently initiated a methodology of estimating the 1O2 concentrations based on the proportionality of ascaridole concentrations with respect to its maximum under these conditions. With the help of the estimated singlet oxygen data, the efficiency of 1O2 utilization and the photo efficiency of converting molecular oxygen to 1O2 are further proposed and evaluated. We have also identified conditions under which a further increase in α-terpinene has caused decreases in ascaridole, implying kinetically that 1O2 has now become a limiting reagent, and the method of treating α-terpinene and ascaridole as a reaction pair in the data analysis would no longer be valid under those conditions. [ABSTRACT FROM AUTHOR]

Palm oil is an edible oil derived from the mesocarp of oil palm fruit (Elaeis guineensis), which has a high content of carotenoids and tocopherol components. This research aimed to study the effects of light intensity on the photo-oxidation stability of a red and yellow palm olein mixture. The red and yellow palm oleins were mixed into 100, 200, and 350 ppm carotene content. The photo-oxidation stability of the palm olein mixture was investigated under fluorescent light intensities of 5,000 and 10,000 lux at 31 ±2 °C for 7 days. Changes in the content of chlorophyll, carotene, tocopherols, and peroxide value (PV) were evaluated daily. The results showed that an increase in carotene and tocopherol contents effectively improved the photo-oxidative stability of the palm olein mixture. Degradation of chlorophyll, tocopherols, and increased PV were proportional to light intensity during photo-oxidation. There were no significant changes in carotene content at 5,000 lux light intensity exposure. The degradation rates of chlorophyll and tocopherols can be described as first-order reaction kinetics. In contrast, the increase rate of PV can be described as a zero-order kinetics model with k-values of 6.6 x 10-2, 4.9 x 10-2, 3.7 x 10-2 mequiv.kg-1.h-1, and 8.3 x 10-2, 6.8 x 10-2, and 5.6 x 10-2 mequiv.kg-1.h-1 in palm olein mixture, which contains 100, 200, and 350 ppm carotene at 5,000 and 10,000 lux light intensity exposure, respectively. These results suggested that carotene protected tocopherol in palm olein and that tocopherol and carotene synergistically acted as singlet oxygen quenchers during photo-oxidation.

The objective of this study was to determine the influence of sunlight on the quality of soybean oil (SBO) and palm olein (POL) and the consequences of their consumption on some biochemical parameters of rats. SBO and POL were purchased from the local market and divided into five (5) groups of 200 g each and transferred in transparent glass containers. One group served as control and the others exposed to sunlight 8 h/day for 15, 30, 45 and 60 days respectively. Their qualities were tested by measuring the oxidation parameters. Oil samples of days 0, 30 and 60 were administered to sixty male rats aged 28 days and some biochemical parameters evaluated. Results showed significant increase in the peroxide (PV) (8.83–62.63 meq O2 /Kg), thiobarbituric acid (TBA) (3.58–19.99 ppm), acid (AV) (0.27–0.56 % oleic acid) and a decrease in iodine value (IV) (50.45–67.57 g I2 /100 g) in photooxidized oils. Biochemical analysis revealed significant increase in Alkaline Phosphatase (ALP) (145–194 U/L), Alanine aminotransferase (ALT) (30–61 U/L), total cholesterol (16–59 mg/dl) and low density lipoprotein (LDL) (4–32 mg/dL) and triglycerides (50–83 mg/dl) in rats fed with photo-oxidized oils compared to control groups. Oils should not be exposed to sunlight.

In the present study, biocomposite materials were created by incorporating biochar (BC) at rates of 1, 2.5, and 5 wt.% into a poly(butylene succinate) (PBSu) matrix using a two-stage melt polycondensation procedure in order to provide understanding of the aging process. The biocomposites in film form were exposed to UV irradiation for 7, 14, and 21 days. Photostability was examined by several methods, such as Fourier transform infrared spectroscopy (FTIR), which proved that new carbonyl and hydroxyl groups were formed during UV exposure. Moreover, Differential Scanning Calorimetry (DSC) measurements were employed to record the apparent UV effect in their crystalline morphology and thermal transitions. According to the molecular weight measurements of composites, it was apparent that by increasing the biochar content, the molecular weight decreased at a slower rate. Tensile strength tests were performed to evaluate the deterioration of their mechanical properties during UV exposure, while Scanning Electron Microscopy (SEM) images illustrated the notable surface alternations. Cracks were formed at higher UV exposure times, to a lesser extent in PBSu/BC composites than in neat PBSu. Furthermore, the mechanism of the thermal degradation of neat PBSu and its biocomposites prior to and upon UV exposure was studied by Pyrolysis–Gas Chromatography/Mass Spectrometry (Py–GC/MS). From all the obtained results it was proved that biochar can be considered as an efficient UV-protective additive to PBSu, capable of mitigating photodegradation.

Numerous vanadium–titania composites have drawn significant interest as efficient photocatalysts for the photocatalytic oxidation of alcohols into valuable aldehydes or C–C coupling compound intermediates. In this comparative study, the photocatalytic potential of two conformations of vanadium–titania catalysts was analyzed, including a vanadium–titania solid solution of VTiOx and vanadium oxide supported on titania VOx/TiO2. The distinct structural interfaces among the components of these catalysts resulted in notably divergent catalytic performances. The VTiOx catalyst is superior to the corresponding supported VOx/TiO2 catalysts in the photo-oxidation of benzyl alcohol. The vanadium incorporated into the titania lattice influences surface oxygen vacancy defects, examined by a series of technologies, thus distinctly improving the photocatalytic activity. The experimental phenomena supported with density functional theory (DFT) studies indicate that incorporating V into the TiO2 lattice can effectively lower the activation energy for the lattice oxygen, thereby improving the generation and repair of oxygen vacancies and thus promoting photo-oxidation. [ABSTRACT FROM AUTHOR]

BackgroundCooling towers are specialized heat exchanger devices in which air and water interact closely to cool the water's temperature. However, the cooling water contains organic nutrients that can cause microbial corrosion (MC) on the metal surfaces of the tower. This research explores the combined wastewater treatment approach using electrochemical-oxidation (EO), photo-oxidation (PO), and photoelectrochemical oxidation (PEO) to contain pollutants and prevent MC.MethodsThe study employed electro-oxidation, a process involving direct current (DC) power supply, to degrade wastewater. MC studies were conducted using weight loss assessments, scanning electron microscopy (SEM), and x-ray diffraction (XRD).ResultsAfter wastewater is subjected to electro-oxidation for 4 h, a notable decrease in pollutants was observed, with degradation efficiencies of 71, 75, and 96%, respectively. In the wastewater treated by PEO, microbial growth is restricted as the chemical oxygen demand decreases.DiscussionA metagenomics study revealed that bacteria present in the cooling tower water consists of 12% of Nitrospira genus and 22% of Fusobacterium genus. Conclusively, PEO serves as an effective method for treating wastewater, inhibiting microbial growth, degrading pollutants, and protecting metal from biocorrosion.

The present work aimed to study the feasibility of photo-Fenton oxidation for the degradation of chlortetracycline chlorhydrate (CTC) in aqueous solutions, as well as the modelling of system behaviour by artificial neural networks. The removal performance of CTC oxidation by the Photo-Fenton process was studied under solar radiation. Different parameters were studied, such as pH (3 to 5), and initial concentrations of CTC (0.1 to 10 mg l–1), hydrogen peroxide (1.701 to 190.478 mg l–1), and ferrous ions (2.8 to 103.6 mg l–1). Results showed that a high removal efficiency of 92 % was achieved at pH 3 under optimised conditions, such as 10 mg l–1 of CTC, 127.552 mg l–1 of H2O2, and 36.4 mg l–1 of Fe2+. The transformation of CTC molecules was proved by UV-visible and HPLC analyses, which showed that almost no CTC molecules were remaining in the treated solution. A multi-layer perceptron artificial neural network has been developed to predict the experimental removal efficiency of CTC based on four dimensionless inputs: molecular weight, and initial concentrations of CTC, hydrogen peroxide and ferrous ions. The best network has been found with a high determination coefficient of 0.9960, and with a very acceptable root mean square error 0.0108. In addition, the global sensitivity analysis confirms that the most influential parameter for the CTC removal by photo-Fenton oxidation is the initial concentration of ferrous cations with a relative importance of 33 %.

Photosensitized oxidation has been considered to offer better disinfection mechanism under natural sunlight and the efficiency of its inactivation pathway depends on the concentration of dissolving oxygen, the solar irradiance, and the reactive nature of the liquid. This study aimed to evaluate the hydraulic mixer's aeration performance during photo-oxidation treatment. A hydraulic jump was created to aerate the sewage prior to its passage into a reactor, and the amount of dissolved oxygen generated was measured. The effect of mixing intensity on sunlight inactivation of faecal coliforms in a reactor was investigated for 60 min using velocity gradients of 520 s−1, 640 s−1, 720 s−1 and 960 s−1 produced under flow rates of 3 L min−1, 5 L min−1 and 7 L min−1 and 10 L min−1 respectively. The photo-oxidation kinetics of faecal coliform contained in settled and raw sewage samples were also studied under two dark control tests (static and dynamic tests) and a light test. The system achieved a 2.0–2.34 log reduction of faecal coliforms and dissolved oxygen was within the range of 1.9 mg L−1 - 3.0 mg L−1. In the dynamic control test, the inactivation rate constant of bacteria indicated a reduction of 1.11 log (92%) for settled sewage and 1.0 log (90%) for raw sewage. The coliform inactivation rate constant, due to the combined effect of turbulent mixing speed and dark inactivation rate constant, was 2.3 h−1, and the solar irradiance inactivation rate constant was 2.4 h−1. These results have demonstrated that induced aeration is an economically friendly approach to enhance wastewater treatment in developing nations with long sunshine hours.

The present work aimed to study the feasibility of photo-Fenton oxidation for the degradation of chlortetracycline chlorhydrate (CTC) in aqueous solutions, as well as the modelling of system behaviour by artificial neural networks. The removal performance of CTC oxidation by the Photo-Fenton process was studied under solar radiation. Different parameters were studied, such as pH (3 to 5), and initial concentrations of CTC (0.1 to 10 mg l −1), hydrogen peroxide (1.701 to 190.478 mg l −1), and ferrous ions (2.8 to 103.6 mg l −1). Results showed that a high removal efficiency of 92 % was achieved at pH 3 under optimised conditions, such as 10 mg l −1 of CTC, 127.552 mg l −1 of H2O2, and 36.4 mg l −1 of Fe2+. The transformation of CTC molecules was proved by UV-visible and HPLC analyses, which showed that almost no CTC molecules were remaining in the treated solution. A multi-layer perceptron artificial neural network has been developed to predict the experimental removal efficiency of CTC based on four dimensionless inputs: molecular weight, and initial concentrations of CTC, hydrogen peroxide and ferrous ions. The best network has been found with a high determination coefficient of 0.9960, and with a very acceptable root mean square error 0.0108. In addition, the global sensitivity analysis confirms that the most influential parameter for the CTC removal by photo-Fenton oxidation is the initial concentration of ferrous cations with a relative importance of 33 %. [ABSTRACT FROM AUTHOR]

Aerosol hygroscopicity and liquid water content (ALWC) have important influences on the environmental and climate effect of aerosols. In this study, we measured the hygroscopic growth factors (GF) of particles with dry diameters of 40, 80, 150, and 200 nm during the wintertime in Nanjing. Both the GF -derived hygroscopicity parameter (κ gf) and ALWC increased with particle size, but displayed differing diurnal variations, with κ gf peaking around the midday, while ALWC peaking in the early morning. Nitrate, ammonium and oxygenated organic aerosols (OOA) were found as the chemical components mostly strongly correlated with ALWC. A closure study suggests that during midday photo-oxidation and nighttime high ALWC periods, the κ of organic aerosols (κ org) was underestimated when using previous parameterizations. Accordingly, we re-constructed parameterizations for κ org and the oxidation level of organics for these periods, which indicates a higher hygroscopicity of photochemically formed OOA than the aqueous OOA, yet both being much higher than the generally assumed OOA hygroscopicity. Additionally, in a typical high ALWC episode, concurrently increased ALWC, nitrate, OOA as well as aerosol surface area and mass concentrations were observed under elevated ambient RH. This strongly indicates a coupled effect that the hygroscopic secondary aerosols, in particular nitrate with strong hygroscopicity, led to large increase in ALWC, which in turn synergistically boosted nitrate and OOA formation by heterogeneous/aqueous reactions. Such interaction may represent an important mechanism contributing to enhanced formation of secondary aerosols and rapid growth of fine particulate matter under relatively high RH conditions. [ABSTRACT FROM AUTHOR]

• Photo-oxidation significantly promoted the generation of ROS from ACs. • Photo-oxidation markedly affected functional groups and light absorption from ACs. • Photo-oxidation caused π-electrons transfer from ground state to an excited state. • The complex types and complexation time influenced ROS generation from ACs and TMs. Particulate matter (PM) can cause adverse health effects by overproducing reactive oxygen species (ROS). Although the ability of PM to induce ROS generation depends on its composition and environmental factors. This study explores how photo-oxidation affects ROS generation from aromatic compounds (ACs, including catechol (CAT), phthalic acid (PA), and 4,4′-oxydibenzoic acid (4,4′-OBA)) and their mixtures with transition metals (TMs, including Fe(II), Mn(II), and Cu(II)) using Fourier-transform infrared (FTIR) and Ultraviolet-visible spectroscopy (UV–Vis). Results showed that photo-oxidation facilitated ROS generation from ACs. CAT-Fe(II)/Cu(II) showed synergistic effects, but 4,4′-OBA-Fe(II)/Cu(II) showed antagonistic effects. ACs-Mn(II) and PA-Fe(II)/Cu(II) exhibited synergistic effects first and then showed antagonistic effects. The different interactions were due to complexation between ACs and TMs. The photo-oxidized ACs-TMs significantly enhanced ROS generation compared with ACs-TMs. The study suggested the photo-oxidation mechanism involved that the transfer of π-electrons from the ground to an excited state in benzene rings and functional groups, leading to the breakage and formation of chemical bonds or easier π-electron transfer from ACs to TMs. The former could generate ROS directly or produce polymers that promoted ROS generation, while the latter promoted ROS generation by transferring π-electrons to dissolved oxygen quickly. Our study revealed that both interactions among components and photo-oxidation significantly influenced ROS generation. Future studies should integrate broader atmospheric factors and PM components to fully assess oxidative potential and health impacts. [Display omitted] [ABSTRACT FROM AUTHOR]

Based on recent scientific-technical developments referring to the transformation and biodegradation mechanisms of plastic compounds, progress has been made both in the conceptualization of relevant definitions and in the development of technical standards that allow determining, in a more precise and reproducible way, the ratio of biodegradability of a determined material. From these advances, they have developed, furthermore, the so-called oxo-biodegradable plastics, in which pro-oxidant additives are added to the raw polymer in such a way that allow a optimal abiotic transformation process (photo/thermo oxidation), producing the fragmentation of the material under suitable conditions for its simultaneous or successive biotic degradation (enzymatic oxidation). Although, currently, oxobiodegradable plastics are widely used in different applications such as, for example, in agriculture and single-use plastics, until very recently a technical standard was developed that allows determining the relative degradation ratio of different types of plastics under abiotic and biotic conditions. This process implies that for producers to be able to use specific terms of bio-degradation and oxo-biodegradation for advertising purposes that claim to offer an environmentally friendly product, the relevant entities must carry out metrological tests in light of the new definitions and technical standards. Furthermore, a large amount of specialized literature has been generated in which the bio-degradation ratio of oxobiodegradable plastics is determined in very specific environments and conditions. This review gives a detailed account of the different definitions and scientific concepts involved in oxo-/bio- degradation and shows how these concepts have evolved over time. It also shows the evolution of the technical standards, which, in general, are adapted to the new scientific and technical developments in the field of plastics. Finally, a detailed analysis of results reported in the scientific literature shows the dependence of oxo-biodegradation on different parameters (UV radiation, temperature, exposure time, type of enzymes), specific environments (soil, composting, waste, recycling, etc.), different types of plastics (LDPE, HDPE, LLDPE, pro-oxidant additives) and, finally, on different analytical techniques used (FTIR, DSC, TGA, SEM, tensile test).

Two‐dimensional (2D) materials with unique physicochemical properties promote photocatalytic activities. As the 2D material composites research studies the statistical average of complex catalytic behaviors, an integrated photonic platform allows for clean and single flake level photo‐catalytic investigations with precisely quantified photocatalytic activities. In this paper, fluence‐dependent photo‐oxidation in two‐dimensional Tellurene (2D Te) is tracked by the evanescently coupled micro‐resonator. Nearly 32% of oxidation is achieved in ≈10 nm 2D Te flake, compared to only 4.5% oxidation in a 30 nm sample, probed by the resonance shift in silicon micro‐ring resonators substrate. The wider bandgap in the few layers of 2D Te allows faster charge transfer to adsorbed oxygen for a more efficient photocatalytic redox reaction. The photo‐oxidation in hybrid 2D Te results in invariant lineshapes of optical transmission resonance for wavelength trimming (more than 3× resonance bandwidth). The low threshold power, near‐infrared, and in‐waveguide resonance trimming scheme is compatible with most integrated photonic setups for easy fixing of the nanofabrication‐induced random resonance deviation for integrated photonic circuit applications in wavelength‐division‐multiplexing systems and spin qubits quantum computing. [ABSTRACT FROM AUTHOR]

Once emitted into the environment, macro- (MaP), micro- (MP) and nanoplastics (NP) are exposed to environmental weathering. Yet, the effects of biogeochemical weathering factors occurring in the soil environment are unknown. As the transport, fate, and toxicity of MP and NP depend directly on their surface properties, it is crucial to characterize their transformation in soils to better predict their impact and interactions in this environment. Here, we used scanning transmission x-ray micro spectroscopy to characterize depth profiles of the surface alteration of environmental plastic debris retrieved from soil samples. Controlled weathering experiments in soil and with UV radiation were also performed to investigate the individual effect of these weathering factors on polymer surface alteration. The results revealed a weathered surface on a depth varying between 1 µm and 100 nm in PS, PET and PP environmental plastic fragments naturally weathered in soil. Moreover, the initial step of surface fragmentation was observed on a PS fragment, providing an insight on the factors and processes leading to the release of MP and NP in soils. The comparison of environmental, soil incubated (for 1 year) and UV weathered samples showed that the treatments led to different surface chemical modifications. While the environmental samples showed evidence of alteration involving oxidation processes, the UV weathered samples did not reveal oxidation signs at the surface but only decrease in peak intensities (indicating decrease of the number of chemical C bonds). After a one-year incubation of samples in soil no clear aging effects were observed, indicating that the aging of polymers can be slow in soils. [ABSTRACT FROM AUTHOR]

Photo‐driven CH4 conversion to multi‐carbon products and H2 is attractive but challenging, and the development of efficient catalytic systems is critical. Herein, we construct a solar‐energy‐driven redox cycle for combining CH4 conversion and H2 production using iron ions. A photo‐driven iron‐induced reaction system was developed, which is efficient at selective coupling of CH4 as well as conversion of benzene and cyclohexane under mild conditions. For CH4 conversion, 94 % C2 selectivity and a C2H6 formation rate of 8.4 μmol h−1 is achieved. Mechanistic studies reveal that CH4 coupling is induced by hydroxyl radical, which is generated by photo‐driven intermolecular charge migration of an Fe3+ complex. The delicate coordination structure of the [Fe(H2O)5OH]2+ complex ensures selective C−H bond activation and C−C coupling of CH4. The produced Fe2+ can be used to reduce the potential for electrolytic H2 production, and then turns back into Fe3+, forming an energy‐saving and sustainable recyclable system. [ABSTRACT FROM AUTHOR]

The type of material used in packaging, lighting, and storage time can impact food quality during storage. This study aimed to investigate the progress of photosensitized oxidation in refined soybean oil using steady-state and time-resolved fluorescence spectroscopy. The experiment was conducted through accelerated photo-oxidation with Light-Emitting Diode (LED) in samples stored for ten days at room temperature (26.0 ± 2.0 °C) in clear polyethylene terephthalate (PET) packaging of different colors and different transmission spectra in the UV and visible range. Emission spectra were obtained with excitation at 373, 405, and 500 nm, resulting in two main emission peaks: the first with maximum emission between 430 and 555 nm and the second at around 660 nm. Fluorescence decay curves were obtained with excitation at 340 and 405 nm. The results indicated that transparent PET bottles are not effective in protecting soybean oil from photosensitized oxidation under the studied conditions. Strong correlations were observed between fluorescence parameters and peroxide and conjugated diene values, indicators of lipid oxidation progress. Fluorescence spectroscopy has several advantages over traditional methods as it is a simple, fast, low-cost, and low-waste technique. [ABSTRACT FROM AUTHOR]

Solar radiation experiments showed a shift in the composition of natural organic matter (NOM). Due to irradiation, the concentration of high molecular weight (HMW) molecules decreased, and that of the low molecular weight (LMW) fraction increased. Microbiological analyses showed that biodegradation was neglectable. To assess the consequences for water treatment processes, coagulation jar tests were performed by comparing the removal effectivity for NOM fractions from irradiated and unirradiated raw water. The degree of dissolved organic carbon (DOC) removal by coagulation was lower for irradiated waters. As primarily HMW organic compounds are removed by coagulation, the decrease in coagulation performance is attributed to the increase in the LMW concentration due to photochemical reactions induced by solar radiation. Flocs were about 15% larger for irradiated water. Possibilities to adapt water treatment to respond to changes in DOC composition and concentration are outlined. Ozonation–biofiltration is judged as the most promising treatment process to cope with climate change-related challenges in drinking water treatment. [ABSTRACT FROM AUTHOR]

We present an environment-friendly and highly efficient method for the oxidation of aromatic alcohols to carboxylic acids or ketones in air via light irradiation under external catalyst-, additive-, and base-free conditions. The photoreaction system exhibits a wide substrate scope and the potential for large-scale applications. Most of the desired products are easily obtained via recrystallization and separation from low-boiling reaction medium acetone in good yields, and the products can be subsequent directly transformed without further purification. [ABSTRACT FROM AUTHOR]

Random propylene–ethylene copolymers (RPC) are a type of polyolefin in increasing demand, mainly for packaging, due to its high impact resistance, large durability as well as high transparency and flexibility. The present study aims to investigate the morphological and rheological properties, as well as the photo-oxidation by UV irradiation, of five different RPCs and their nanocomposites. Organophilic montmorillonite is used as filler and maleic anhydride grafted RPCs as compatibilizers. Aging was performed by exposing strips of materials to UVA radiation for a maximum period of 96 h, and material degradation was analyzed following the evolution of carbonyl and hydroperoxide groups by FTIR and crystallinity by DSC. All nanocomposites display intercalated-exfoliated structure being the largest particle disaggregation presented by the polymer with the largest molecular weight. Rheological results support these observations. Neither the chemical composition of the polymers nor the presence of nanoclay/compatibilizer affects the photo-degradation mechanism of copolymers although the composite structure promotes the matrix photo-degradation. A parabolic relation was found between carbonyl and hydroxyl indexes of all stabilized and extracted materials, with or without clay. An increase in crystallinity with UV radiation dose was observed in all systems with a maximum determined in the case of the extracted systems. [ABSTRACT FROM AUTHOR]

The goal of this work was to investigate the morphological and chemical–physical changes induced by adding ZnO nanoparticles to bio-based polymeric materials based on polylactic acid (PLA) and polyamide 11 (PA11). Precisely, the photo- and water-degradation phenomena of nanocomposite materials were monitored. For this purpose, the formulation and characterization of novel bio-nanocomposite blends based on PLA and PA11 at a ratio of 70/30 wt.% filled with zinc oxide (ZnO) nanostructures at different percentages were performed. The effect of ZnO nanoparticles (≤2 wt.%) within the blends was thoroughly explored by employing thermogravimetry (TGA), size exclusion chromatography (SEC), matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF MS) and scanning and transmission electron microscopy (SEM and TEM). Adding up to 1% wt. of ZnO resulted in a higher thermal stability of the PA11/PLA blends, with a decrement lower than 8% in terms of molar masses (MMs) values being obtained during blend processing at 200 °C. ZnO promoted trans-ester-amide reactions between the two polymers, leading to the formation of PLA/PA11 copolymers. These species could work as compatibilisers at the polymer interface, improving thermal and mechanical properties. However, the addition of higher quantities of ZnO affected such properties, influencing the photo-oxidative behaviour and thus thwarting the material's application for packaging use. The PLA and blend formulations were subjected to natural aging in seawater for two weeks under natural light exposure. The 0.5% wt. ZnO sample induced polymer degradation with a decrease of 34% in the MMs compared to the neat samples. [ABSTRACT FROM AUTHOR]

While synthesis‐properties‐performance correlations are being studied for organophosphonic acid grafted TiO2, their stability and the impact of the exposure conditions on possible changes in the interfacial surface chemistry remain unexplored. Here, the impact of different ageing conditions on the evolution of the surface properties of propyl‐ and 3‐aminopropylphosphonic acid grafted mesoporous TiO2 over a period of 2 years is reported, using solid‐state 31P and 13C NMR, ToF‐SIMS and EPR as main techniques. In humid conditions under ambient light exposure, PA grafted TiO2 surfaces initiate and facilitate photo‐induced oxidative reactions, resulting in the formation of phosphate species and degradation of the grafted organic group with a loss of carbon content ranging from 40 to 60 wt %. By revealing its mechanism, solutions were provided to prevent degradation. This work provides valuable insights for the broad community in choosing optimal exposure/storage conditions that extend the lifetime and improve the materials′ performance, positively impacting sustainability. [ABSTRACT FROM AUTHOR]

By planting LEDs on the surfaces of orifice baffles, a novel batch oscillatory baffled photoreactor (OBPR) together with polymer-supported Rose Bengal (Ps-RB) beads are here used to investigate the reaction kinetics of a photo-oxidation reaction between α-terpinene and singlet oxygen (1O2). In the mode of NMR data analysis that is widely used for this reaction, α-terpinene and ascaridole are treated as a reaction pair, assuming kinetically singlet oxygen is in excess or constant. We have, for the first time, here examined the validity of the method, discovered that increasing α-terpinene initially leads to an increase in ascaridole, indicating that the supply of singlet oxygen is in excess. Applying a kinetic analysis, a pseudo-first-order reaction kinetics is confirmed, supporting this assumption. We have subsequently initiated a methodology of estimating the 1O2 concentrations based on the proportionality of ascaridole concentrations with respect to its maximum under these conditions. With the help of the estimated singlet oxygen data, the efficiency of 1O2 utilization and the photo efficiency of converting molecular oxygen to 1O2 are further proposed and evaluated. We have also identified conditions under which a further increase in α-terpinene has caused decreases in ascaridole, implying kinetically that 1O2 has now become a limiting reagent, and the method of treating α-terpinene and ascaridole as a reaction pair in the data analysis would no longer be valid under those conditions.

The present study is focused on the sol-gel ultrasonic hydrothermal synthesis of zinc oxide (ZnO) nanoparticles and its application in the degradation of Rhodamine B (RhB) dye. ZnO nanoparticles were synthesized with varying temperatures at 90 °C, 190 °C and 550 °C. Zinc nitrate hexahydrate [Zn(NO3)2·6H2O] and potassium hydroxide were used to prepare ZnO nanoparticles and investigated using the X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and diffuse reflectance spectroscopy (DRS) for crystallinity, surface morphology, and band gap, respectively. Results obtained from XRD analysis shows that the synthesized ZnO nanoparticles are of hexagonal structure and crystalline in size ranged from the 21.1–32.41 nm. The effects of temperature show that the crystalline size of ZnO increased with increasing temperature and surface morphology investigated by FESEM. DRS used to calculate the band gap of nanoparticles shows that 3.26 eV at 90 °C, 3.25 eV at 190 °C and 3.23 eV at 550 °C. The optimal condition was determined using the response surface methodology (RSM) based Box Behnken design (BBD) method. We found that the ZnO material synthesized at 90 °C exhibits a smaller size, providing a larger surface area for photocatalytic degradation of the RhB dye. Energy is saved as it was synthesized at low temperatures. The maximum removal efficiency of Rohdamine B (RhB) dye (25 mg/L) obtained were 95% at optimized conditions i.e. pH 7, 2 g/L catalyst dose after 70 min of ultraviolet photocatalytic treatment.

The photo-oxidation of polypropylene at two different temperatures and in three different environments—air, distilled water and sea water—has been followed as a function of the irradiation time. The photo-oxidation kinetic is dramatically dependent on the amount of oxygen available for the oxidation reactions and on the temperature. While the photo-oxidation is very fast in air, the degradation is much slower in the two aqueous media. The degradation in sea water is slightly slower than in distilled water. In all cases, the degradation kinetic increases remarkably with the temperature. This behavior has been attributed to the lower oxygen availability for the oxidation reactions of the polymers. The light difference of the degradation kinetic between the two aqueous media depends on the small difference of the oxygen concentration at the test temperatures of 40 and 70 °C. At the latter temperature, the difference between the degradation kinetic in distilled water and sea water is still less important because increasing the temperature decreases the solubility of the oxygen, and it tends to became very similar in both samples of water. [ABSTRACT FROM AUTHOR]

The goal of this research was to investigate the efficacy photocatalysis with natural solar radiation and artificial UV radiation for disinfecting total coliforms in biologically treated wastewater. The effect of TiO2 dosage and irradiation time on total coliform inactivation as measured by log reduction values (LRV), removal of BOD, COD, turbidity, and effluent properties as measured by pH and conductivity was investigated. Two sets of experimental equipment were constructed, one for using solar UV light and the other for using artificial UV light. After four hours of irradiation with 60 mg/L TiO2, photocatalysis achieved LRVs of 1.4 and 1, respectively, under UV and solar radiation. COD and BOD were reduced by 67% and 50% respectively under UV and solar radiation after two hours of irradiation with 60 mg/L TiO2. Turbidity was reduced by 71%. Both conductivity and acidity of the effluent were reduced as TiO2 concentration was increased. Photocatalysis with natural solar radiation produced disinfection results that were comparable to that of efficient UV light exposure. Artificial UV light and natural solar radiation can be combined in photocatalysis process to form a hybrid process. [ABSTRACT FROM AUTHOR]

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Heterogeneous Brønsted acidic catalysts such as phosphoric acids are the conventional activators for organic transformations. However, the photocatalytic performance of these catalysts is still rarely explored. Herein, a novel Zr-based metal−organic framework Zr-MOF-P with phosphoric acids as a heterogeneous photocatalyst has been fabricated, which shows high selectivity and reactivity towards the photo-oxidation of sulfides under white light illumination. A mechanism study indicates that the selective oxygenation of sulfides occurs with triplet oxygen rather than common reactive oxygen species (ROS). When Zr-MOF-P is irradiated, the hydroxyl group of phosphoric acid is converted into oxygen radical, which takes an electron from the sulfides, and then the activated substrates react with the triplet oxygen to form sulfoxides, avoiding the destruction of the catalysts and endowing the reaction with high substrate compatibility and fine recyclability. [ABSTRACT FROM AUTHOR]

• ABS with a thickness of 450 µm experiences a critical aging period that leads to a transition from ductile to brittle behaviour. • This critical aging time was identified using dynamic tensile tests, which enabled the application of uniform stress across the sample under dynamic conditions. • Atomic Force Microscopy (AFM) analysis revealed that polybutadiene elastomer nodules on the sample surface became rigid due to photo-oxidation. • The brittle behaviour of the material is attributed to the development of thin, fragile layers that contribute to the overall brittle fracture of the sample. The extensive use of Acrylonitrile Butadiene Styrene (ABS) raises challenges due to its vulnerability to oxidative degradation, primarily impacting its mechanical behavior. Photodegradation appears to be the pivotal driver in this degradation process. The main aim of the present study is to provide a comprehensive approach to the underlying mechanisms governing the transition from ductile to brittle behavior in ABS after exposure to UV-induced photodegradation. This study thus focuses on the multiphase nature of ABS, wherein polybutadiene (PB) nodules are dispersed within a matrix of styrene-acrylonitrile. Dynamic mechanical tensile tests have been employed to highlight aged layer mechanical impact by blocking the dissipative response of the matrix and applying a homogenous stress field, while atomic force microscopy (AFM) has been used to characterize the local mechanical properties of ABS finely. The evolution of global mechanical properties has been correlated with changes in microstructural behavior. One of the main contributions of the present work is the correlation between the formation of brittle layers with the brittle state of aged ABS. Mechanical testing using dynamical tensile test revealed a critical aging time marking the transition from a ductile to a brittle state of the 450 µm thick samples. Chemical analysis using infrared spectroscopy revealed evolutions in the material composition, especially in the carbonyl, hydroxyl, and PB unsaturation groups. Distinct thin oxidized layers on each exposed surface were observed using optical microscopy. Finally, AFM analysis on the exposed surface shows the stiffening of PB nodules, indicating the formation of brittle thin layers due to oxidation causing an apparent fragile behavior of ABS. [ABSTRACT FROM AUTHOR]

• PP grades and processing methods show different aging responses. • 3D-printing enhances PP aging resistance vs. conventional processes. • Recycled PP requires re-stabilization for improved aging resistance. This study investigates the weathering resistance of three polypropylene grades (impact-resistant, recycled and UV-stabilized) processed by Fused Filament Fabrication (FFF), injection and thermo-compression. Samples undergo accelerated aging, simulating conditions equivalent to six months in tropical environments with high hydrothermal and UV exposures. They are characterized by chemical, thermal, rheological, mechanical and microstructural analyses. 3D-printed impact-resistant and UV-stabilized PP resist to the considered aging conditions, attributed to the presence of stabilizers. On the contrary, the properties of recycled PP deteriorate over time due to low stabilizer concentration and the presence of impurities post-recycling. Samples processed by thermo-compression and injection display lower aging resistance compared to their 3D-printed counterparts, due to degradation and alteration in the crystalline structure induced by the processing method, like the 'skin effect' observed in injection. These findings highlight the importance of re-stabilization during recycling and the potential of 3D-printing for enhancing the aging resistance of polypropylene. [ABSTRACT FROM AUTHOR]