Search

The hydroxyl radical (

The degradation and mineralization of volatile organic compounds (VOCs) in gas-solid phase photocatalytic systems suffer great challenges due to the low electron transfer efficiency and slow benzene ring-opening kinetics. Hence, a heterojunction photocatalyst of Bi

International audience; Photocatalytic oxidation (PCO) using a TiO(2) catalyst is an effective technique to remove gaseous volatile organic compounds (VOCs). Herein, a lab-scale continuous reactor is used to investigate the photocatalytic performance toward ethylbenzene (EB) vapor removal over TiO(2) nanoparticles immobilized on glass fiber tissue. The role of the reactive species in the removal of EB and the degradation pathway were studied. Firstly, the effect of key operating parameters such as EB concentration (13, 26, 60 mg/m(3)), relative humidity levels (From 5 to 80%), gas carrier composition (dry air + EB, O(2) + EB and N(2) + EB) and ultraviolet (UV) radiation wavelength (UV-A (365 nm), UV-C (254 nm)) were explored. Then, using superoxide dismutase and tert-butanol as trapping agents, the real contribution of superoxide radical anion (O(2)(.-)) and hydroxyl radicals (OH(.)) to EB removal was quantified. The results show that (i) small water vapor content enhances the EB degradation; (ii) the reaction atmosphere plays an important role in the photocatalytic process; and (iii) oxygen atmosphere/UV-C radiation shows the highest EB degradation percentage. The use of radical scavengers confirms the major contribution of the hydroxyl radical to the photocatalytic mechanism with 75% versus 25% for superoxide radical anion.

Chemodynamic therapy (CDT) can efficiently kill cancer cells by producing hydroxyl radical (•OH), a kind of high-toxic reactive oxygen species (ROS), via Fenton or Fenton-like reactions. This study involved a versatile nanomedicine, MSN@DOX/GA-Fe/PDA (M@DGP), delivered via microneedles, which was expected to combine chemodynamic/photothermal/chemotherapy and efficiently increase ROS accumulation to achieve significant therapeutic efficacy against melanoma.The composition of the synthesized nanoparticles was confirmed by a series of characterizations including transmission electron microscopy, Fourier transform infrared spectroscopy, and zeta potential. The photothermal properties of the nanomedicine was evaluated via infrared imaging, and •OH-producing ability was evaluated by UV-Vis and electron spin resonance. The mechanisms of ROS accumulation were studied in B16 cells by detecting intracellular •OH, glutathione, and ROS levels. The drug-loaded microneedles (M@DGP-MNs) were prepared, and their morphology and mechanical strength were characterized. The in vivo antimelanoma effect and biosafety evaluation of the nanomedicine were investigated in tumor-bearing C57 mice.M@DGP was successfully prepared and could achieve ROS accumulation through a photothermal-enhanced Fenton reaction, polydopamine-induced glutathione consumption, and doxorubicin-mediated mitochondrial dysfunction which induced oxidative stress and apoptosis of tumor cells. M@DGP-MNs showed superior antitumor efficacy and good biosafety, providing a promising strategy for melanoma treatment.

Activation of lignin by demethylation for improving the reactivity has attracted extensive attentions. However, it still faces many challenges, such as the unsatisfied increase of hydroxyl content and the undesired cracking of linear linkages. Here, the efficient demethylations for significantly increasing the hydroxyl content and protecting the structure of industrial lignin were explored using lewis acid as modification reagent. As BBr

According to the latest report from the intergovernmental panel on climate change (IPCC), currently, global warming due to methane (CH4) alone is about 0.5°C while due to carbon dioxide (CO2) alone is about 0.75°C. As CH4 emissions will continue growing, in order to limit warming to 1.5˚C, some of the most effective strategies are rapidly reducing CH4 emissions and developing large scale CH4 removal methods. The aim of this review article is to summarise and propose possible methods for atmospheric CH4 removal, based on the hydroxyl radical (°OH), which is the principal natural sink of many gases in the atmosphere and on many water surfaces. Inspired by mechanisms of °OH generation in the atmosphere and observed or predicted enhancement of °OH by climate change and human activities, we proposed several methods to enhance the °OH sink by some physical means using water vapour and artificial UV radiation.

Radical addition reactions of olefins have emerged as an attractive tool for the rapid assembly of complex structures, and have plentiful applications in organic synthesis, however, such reactions are often limited to polymerization or 1,2-difunctionalization. Herein, we disclose an unprecedented radical relay 1,4-oxyimination of two electronically differentiated olefins with a class of bifunctional oxime carbonate reagents via an energy transfer strategy. The protocol is highly chemo- and regioselective, and three different chemical bonds (C-O, C-C, and C-N bonds) were formed in a single operation in an orchestrated manner. Notably, this reaction provides rapid access to a large variety of structurally diverse 1,4-oxyimination products, and the obtained products could be easily converted into valuable biologically relevant δ-hydroxyl-α-amino acids. With a combination of experimental and theoretical methods, the mechanism for this 1,4-oxyimination reaction has been investigated. Theoretical calculations reveal that a radical chain mechanism might operate in the reaction.

Metal ions are key components in atmosphere that potentially affect the optical properties and photochemical reactivity of atmospheric humic-like substances (HULIS), while this mechanism is still unclear. In this study, we demonstrated that atmospheric HULIS coupled with Fe

The hydrogen bond (H-bond) is essential to stabilizing the three-dimensional biological structure such as protein, cellulose, and lignin, which are integral parts of animal and plant cells; thus, stereo-recognition of the H-bond is extremely attractive. Herein, a methodology combining the variable-temperature

Microbially mediated iron redox processes are of great significance in the biogeochemical cycles of elements, which are often coupled with soil organic matter (SOM) in the environment. Although the influences of SOM fractions on individual reduction or oxidation processes have been studied extensively, a comprehensive understanding is still lacking. Here, using ferrihydrite

Chronic inflammatory wounds pose therapeutic challenges in the biomedical field. Polymeric nanofibrous matrices provide extracellular-matrix-like structures to facilitate wound healing; however, wound infection and the subsequent accumulation of reactive oxygen species (ROS) delay healing. Therefore, we herein developed electrospun nanofibers (NFs), composed of chitosan-stabilized Prussian blue (PBChi) nanoparticles (NPs) and poly(vinyl alcohol) (PVA), with ROS scavenging activity to impart antioxidant and wound healing properties. The PBChi NPs were prepared using chitosan with different molecular weights, and their weight ratio with respect to PVA was optimized to yield PBChi-NP-coated PVA NFs with well-defined NF structures. In situ and in vitro antioxidant activity assays showed that the PBChi/PVA NFs could effectively remove ROS. Particularly, PBChi/PVA NFs with a lower chitosan molecular weight exhibited greater antioxidant activity. The hydroxyl radical scavenging activity of PBChi10k/PVA NFs was 60.4 %, approximately two-fold higher than that of PBChi100k/PVA NFs. Further, at the concentration of 10 μg/mL, they could significantly lower the in vitro ROS level by up to 50.7 %. The NFs caused no significant reduction in cell viability, owing to the excellent biocompatibility of PVA with PBChi NPs. Treatment using PBChi/PVA NFs led to faster cell proliferation in in vitro scratch wounds, reducing their size from 202 to 162 μm. The PBChi/PVA NFs possess notable antioxidant and cell proliferation properties as ROS-scavenging wound dressings.

Shifting four-electron (4e

Fe(II)-catalyzed ferrihydrite transformation under anoxic conditions has been intensively studied, while such mechanisms are insufficient to be applied in oxic environments with depleted Fe(II). Here, we investigated expanded pathways of sunlight-driven ferrihydrite transformation in the presence of dissolved oxygen, without initial addition of dissolved Fe(II). We found that sunlight significantly facilitated the transformation of ferrihydrite to goethite compared to that under dark conditions. Redox active species (hole-electron pairs, reactive radicals, and Fe(II)) were produced from the ferrihydrite interface via the photoinduced electron transfer processes. Experiments with systematically varied wet chemistry conditions probed the relative contributions of three pathways for the production of hydroxyl radicals: (1) oxidation of water (5.0%); (2) reduction of dissolved oxygen (40.9%); and (3) photolysis of Fe(III)-hydroxyl complexes (54.1%). Results also showed superoxide radicals as the main oxidant for Fe(II) reoxidation under acidic conditions, thus promoting the ferrihydrite transformation. The presence of inorganic ions (chloride, sulfate, and nitrate) did not only affect the hydrolysis and precipitation of Fe(III) but also the generation of radicals via photoinduced charge transfer reactions. The involvement of redox active species and the accompanying mineral transformations would exert a profound effect on the fate of multivalent elements and organic contaminants in aquatic environments.

Hydrazine is widely used in industrial and agricultural production, but excessive hydrazine possesses a serious threat to human health and environment. Here two new ratiometric fluorescence probes

Antioxidants fucoidans from three seaweeds, Undaria pinnatifida (FUP), Macrocystis pyrifera (FMP) and Fucus vesiculosus (FFV) are sold commercially. However, it is unclear which fucoidan is the most potent antioxidant. Therefore, our objective was to compare the antioxidant activities of these fucoidans. For this purpose, six in vitro antioxidant tests were used, total antioxidant capacity, hydroxyl radical scavenging assay, ferrous and cupric chelating assay, reducing power and H

During the pyrite oxidation process, aqueous ferrous/ferric ions (Fe

Dark formation of hydroxyl radicals (•OH) from soil/sediment oxygenation has been increasingly reported, and solid Fe(II) is considered as the main electron donor for O

Hydroxyl radical produced by hydrogen peroxide decomposition under UV radiation was used to degrade larch tannins in an environmentally friendly manner. The formaldehyde reactivity of the degraded products was used as an index to control the mean degree of polymerization (mDP) of the degraded products, and the effects of different mDP on the antioxidant activity of tannins were studied. Results showed that hydroxyl radical could significantly reduce the degree of polymerization (DP) and molecular weight (

Poria cocos, a famous traditional Chinese medicine and a well-known food or food supplement, has shown therapeutic potential against cancer and the uneasiness of the mind. In addition, polysaccharides (PCPs) in this fungus were found to be various bioactive. In this work, one such PCP, PCP-1, extracted by deep eutectic solvent (DES) and separated using Sephadex G-15 columns, was characterized using GC-MS, HPGPC, FT-IR, and NMR, while also tested for physicochemical properties. Results indicated that PCP-1 contained 96.89 ± 3.21% total sugars and was a glucan with molecular weight of 3.2 kD. The main glycosidic linkage was 1,3-linked Glcp with 96.82 mol% content and a triple helix structure, and β-D-Glcp-(1 → linkage connected to the main chain through an O-6 atom was the backbone structure. In terms of the physicochemical property, PCP-1 was soluble in water, but not in organic solvent, and processed a relative high water-holding capacity (8.64 ± 0.14 g/g) and low oil-holding capacity (2.52 ± 0.21 g/g). In addition, in vitro, PCP-1 was found to have the ability of scavenging DPPH, hydroxyl free radical, superoxide anion radical and reducing ferric at different levels. This research would be useful for the further application of PCP-1.

The ZrSn composites materials were prepared in one pot by chemical co-precipitation method. SnO2 was incorporated to ZrxOy modifying the molar percentage from 1 to 5 mol%. The ZrSn composites were characterized by different techniques: XRD, FTIR, DRS, SEM, N2 physisorption and HR-TEM. The ZrSn composites were dried at 80 °C and thereafter were evaluated in the photodegradation of phenol under UV irradiation. The percentages of degradation and mineralization were determined after a reaction time of 150 min by UV–Vis spectroscopy and Total Organic Carbon analysis (TOC), respectively. The composite containing SnO2 in a 3 mol% showed the highest photoactivity with a 72% of photodegradation, a higher value compared with the obtained with TiO2-P25 (62%). Finally, a possible reaction mechanism was proposed based on certain studies, which allows to follow the formation of the active species •OH, •O2− and h+. The formation of the •OH specie was measured by fluorescence spectroscopy whereas the inhibition of the species •O2− and h+ was determined by UV–Vis spectroscopy. The results showed that the ZrSn composites not promotes the hydroxyl radical formation. In addition, the holes capture showed a full-loss of the photoactivity while the minimization of (•O2−) radicals in the reaction media results in a decrement of the photoactivity. The formation of heterojunctions and the presence of localized states in the synthesized composites offer an excellent alternative for a fast photodegradation of phenol.

This study used coagulation sludge from a landfill leachate treatment to prepare a modified coagulation sludge (MCS) catalyst by the limited oxygen pyrolysis method, and the adsorption, degradation efficiency, and reaction mechanism of bisphenol A (BPA) in the MCS activated peroxymonosulfate (MCS/PMS) process were investigated. The pyrolysis temperature determined the adsorption capacity and the activation ability of MCS. At a pyrolysis temperature of 300 °C for 2 h, the MCS300-2 test material had the best adsorption capacity for BPA, while MCS450-2 prepared at a pyrolysis temperature of 450 °C for 2 h had a better catalytic performance towards PMS. In the MCS/PMS process, BPA (20 mg/L) could be completely degraded at 120 min under room temperature when the initial pH = 7, PMS dosage = 3 g/L, and MCS dosage = 0.3 g/L. Radical quenching experiments indicated that both hydroxyl radical (·OH) and sulfate radical (SO

Natural chalcopyrite was evaluated as heterogeneous Fenton catalyst. Catalytic performance was evaluated considering different systems, catalyst dosage, H

Iron chalcogenides have attracted great interest as potential substitutes of nature enzymes in the colorimetric biological sensing due to their unique chemodynamic characteristics. Herein, we reported the preparation of ultrathin FeS nanosheets (NSs) by a simple one-pot hydrothermal method and the prepared FeS NSs exhibit strong Fenton-reaction activity to catalyze hydrogen peroxide (H2O2) for generation of hydroxyl radical (•OH). Based on the chromogenic reaction of resultant •OH with 3,3′,5,5′-tetramethylbenzidine (TMB), we develop colorimetric biosensors for highly sensitive detection of H2O2 and glutathione (GSH). The fabricated biosensors show wide linear ranges for the detection of H2O2 (5-150 μmol/L) and GSH (5-50 μmol/L). Their detection limits for H2O2 and GSH reach as low as 0.19 μmol/L and 0.14 μmol/L, respectively. The experimental results of sensing intracellular H2O2 and GSH demonstrate that this colorimetric method can realize the accurate detection of H2O2 and GSH in normal cells (LO2 and 3T3) and cancer cells (MCF-7 and HeLa). Our results have demonstrated that the synthesized FeS NSs is a promising material to construct colorimetric biosensors for the sensitive detection of H2O2 and GSH, holding great promising for medical diagnosis in cancer therapy.

The present study specifically investigates vacuum ultraviolet (VUV) catalytic oxidation for toluene degradation over CeO2 nanorods. Synergetic effects of ultraviolet photocatalytic oxidation (UV-PCO) and ozone catalytic oxidation (OZCO) were manifested in the results of toluene removal and COx generation, while the combination of UV-PCO and OZCO (UV-OZCO) did not lead to improvement of mineralization. All the processes contribute to ozone decomposition, but no obvious synergetic effects of the different processes can be observed. Intermediate analysis results indicated that more toluene was oxidized into by-products, such as benzyl alcohol and benzaldehyde, by UV-OZCO rather than forming COx. Both hydroxyl radical (•OH) and superoxide radical (•O2-) were found in all the processes of the VUV-PCO-OZCO system (combination of VUV photolysis, UV-PCO, OZCO and UV-OZCO processes). In the UV-OZCO process, the formation of hydroxyl radical was promoted, while that of superoxide radical was impeded, resulting in lower mineralization level of toluene. The mechanistic study of toluene degradation over CeO2 nanorods in the VUV-PCO-OZCO system revealed that with the formation of •O2- and •OH, toluene is first oxidized to intermediates, followed by further ring-opening reaction and, finally, degradation into CO2 and H2O. CeO2 nanorods function as both ozonation catalyst and photocatalyst, and the redox pair of Ce3+ and Ce4+ are interconvertible and can keep a balance.

In recent years, chemodynamic therapy (CDT) has received extensive attention as a novel means of cancer treatment. The CDT agents can exert Fenton and Fenton-like reactions in the acidic tumor microenvironment (TME), converting hydrogen peroxide (H

Azo dyes such as Congo red can easily cause cancer when they come into contact or are absorbed by the human body, so it is urgent to find a fast and simple method for degrading Congo red. In order to better achieve this research goal, an ultrasonic method was used to degrade Congo red solution in a rotating flow field. The concentration of hydroxyl radical in the solution was significantly increased under the action of ultrasonic cavitation, chemical action of zero valent iron, and mechanochemistry. Under the strong oxidation of hydroxyl radical and the reduction of nano zero valent iron peeled off in the reaction process, the reaction speed is significantly accelerated and should promote the reaction. The effect of increasing stirring and adding iron powder particles on ultrasonic cavitation was studied by numerical simulation, and the yield of hydroxyl radical in the system was measured by fluorescence analysis. The experimental results show that, first, the rotating field formed by mixing increases the uniformity of ultrasonic sound field distribution and the amplitude of sound pressure, and it improves the cavitation intensity. In the effective dispersion area, the strong ultrasonic wave can form a temporary high-energy microenvironment in the suspension through cavitation, generate high strength shockwaves and micro jets, and thus significantly deagglomerate the iron powder aggregates. The addition of iron powder particles then provides a complementary Fenton reagent for the degradation reaction. The concentration of hydroxyl radicals in the solution was significantly increased by the synergy of the two actions. The degradation rate of Congo red reached more than 99% after 30 min of reaction.

Hydroxyl radicals (OH) play a crucial role in plasma-bio applications. As pulsed plasma operation is preferred, and even expanded to the nanosecond range, it is essential to study the relationship between OH radical production and pulse characteristics. In this study, we use optical emission spectroscopy to investigate OH radical production with nanosecond pulse characteristics. The experimental results reveal that longer pulses generate more OH radicals. To confirm the effect of pulse properties on OH radical generation, we conduct computational chemical simulations, focusing on two types of pulse properties: pulse instant power and pulse width. The simulation results show that, similar to the experimental results, longer pulses generate more OH radicals. In the nanosecond range, reaction time is critical for OH radical generation. In terms of chemical aspects, N2 metastable species mainly contribute to OH radical generation. It is a unique behavior observed in nanosecond range pulsed operation. Furthermore, humidity can turn over the tendency of OH radical production in nanosecond pulses. In a humid condition, shorter pulses are advantageous for generating OH radicals. Electrons play key roles in this condition and high instant power contributes to them.

Atmospheric brown carbon (BrC) can impact the radiative balance of the earth and form photooxidants. However, the light absorption and photochemical properties of BrC from different sources remain poorly understood. To address this gap, dilute water extracts of particulate matter (PM) samples collected at Davis, CA over one year were analyzed using high resolution aerosol mass spectrometry (HR-AMS) and UV-vis spectroscopy. Positive matrix factorization (PMF) on combined AMS and UV-vis data resolved five water-soluble organic aerosol (WSOA) factors with distinct mass spectra and UV-vis spectra: a fresh and an aged water-soluble biomass burning OA (WSBBOAfresh and WSBBOAaged) and three oxygenated OA (WSOOAs). WSBBOAfresh is the most light-absorbing, with a mass absorption coefficient (MAC365nm) of 1.1 m2 g-1, while the WSOOAs are the least (MAC365nm = 0.01-0.1 m2 g-1). These results, together with the high abundance of WSBBOAs (∼52% of the WSOA mass), indicate that biomass burning activities such as residential wood burning and wildfires are an important source of BrC in northern California. The concentrations of aqueous-phase photooxidants, i.e., hydroxyl radical (·OH), singlet molecular oxygen (1O2*), and oxidizing triplet excited states of organic carbon (3C*), were also measured in the PM extracts during illumination. Oxidant production potentials (PPOX) of the five WSOA factors were explored. The photoexcitation of BrC chromophores from BB emissions and in OOAs is a significant source of 1O2* and 3C*. By applying our PPOX values to archived AMS data at dozens of sites, we found that oxygenated organic species play an important role in photooxidant formation in atmospheric waters.

In this paper, reaction kinetics, degradation mechanisms and associated toxicity have been assessed in detail concerning the abatement of neonicotinoid insecticide clothianidin (CLO) by ozone-based oxidation in water. The second-order rate constants for the reaction of CLO with molecular ozone (O3) and hydroxyl radical ([rad]OH) were determined by the direct and competition kinetics (with UV/H2O2 system as the radical source) methods, respectively, and estimated to be 103 M−1 s−1 and 3.7·109 M−1 s−1. This suggested a (potential) higher contribution of the indirect mechanism rather than the direct degradative pathway in the CLO ozonation process. Additionally, CLO oxidation was studied through an O3 and O3/H2O2 system for three complex real water matrices with distinct characteristics. DOC content was found to be the main parameter responsible for making difficult the achievement of high CLO degradations, whereas carbonate alkalinity did not exert a great impact on the process efficiency. Results indicated that typical ozone doses (up to 1 mg O3/mg DOC) were not enough for the complete removal of this micropollutant, ranging only from 50 to 80%. The study concerning the transformation products (TPs), performed by means of high-resolution mass spectrometry, allowed to suggest potential degradation routes based on the five major CLO-TPs identified. It was inferred that [rad]OH was involved in the formation of all TPs, whereas O3 was only involved in the formation of two of them. A preliminary toxicity assessment concerning CLO and its TPs during ozonation was conducted at three different trophic levels via the ECOSAR software. Results showed that none of the compounds was classified as very toxic for aquatic organisms, and all TPs exhibited minor toxicity than the parent compound. Changes in molecular structure, such as chlorothiazole ring breakdown, could be the main reason for this considerable decrease in toxicity. Overall, the present study demonstrates that ozonation can be considered a suitable technology alternative for CLO (and associated toxicity) abatement from aqueous matrices., This work was financially supported by MCIN/AEI/10.13039/501100011033, with the project PID2020-112674RB-I00, as well as by the Agency for Management of University and Research Grants of the Government of Catalonia (project 2017SGR131).

Remote sensing (RS) of volcanic gases has become a central tool for studying volcanic activity. For instance, ultraviolet (UV) skylight spectroscopy with grating spectrographs (GS) enables SO2 (and, under favourable conditions, BrO) quantification in volcanic plumes from autonomous platforms at safe distances. These measurements can serve volcanic monitoring and they cover all stages of volcanic activity in long measurement time series, which substantially contributes to the refinement of theories on volcanic degassing. Infrared (IR) remote sensing techniques are able to measure further volcanic gases (e.g., HF, HCl, CO2, CO). However, the employed Fourier transform spectrometers (FTSs) are intrinsically intricate and, due to limited resolving power or light throughput, mostly rely on either lamps, direct sun, or hot lava as light source, usually limiting measurements to individual field campaigns. We show that many limitations of grating spectrographs and Fourier transform spectrometer measurements can be overcome by Fabry-Perot interferometer (FPI) based spectrograph implementations. Compared to grating spectrographs and Fourier transform spectrometers, Fabry-Perot interferometer spectrographs reach a 1-3 orders of magnitude higher spectral resolution and superior light throughput with compact and stable set-ups. This leads to 1) enhanced sensitivity and selectivity of the spectral trace gas detection, 2) enables the measurement of so far undetected volcanic plume constituents [e.g., hydroxyl (OH) or sulfanyl (SH)], and 3) extends the range of gases that can be measured continuously using the sky as light source. Here, we present measurements with a shoe-box-size Fabry-Perot interferometer spectrograph (resolving power of ca. 150000), performed in the crater of Nyiragongo volcano. By analysing the light of a ultraviolet light emitting diode that is sent through the hot gas emission of an active lava flow, we reach an OH detection limit of about 20 ppb, which is orders of magnitude lower than the mixing ratios predicted by high-temperature chemical models. Furthermore, we introduce example calculations that demonstrate the feasibility of skylight-based remote sensing of HF and HCl in the short-wave infrared with Fabry-Perot interferometer spectrographs, which opens the path to continuous monitoring and data acquisition during all stages of volcanic activity. This is only one among many further potential applications of remote sensing of volcanic gases with high spectral resolution.

In the past few years, pharmaceutical compounds have appeared as emerging category of environmental pollutants. These microcontaminants can exhibit adverse acute and chronic effects on natural flora and fauna. The detection of pharmaceutical residues in surface waters (rivers, streams, and lakes), seawater, groundwater, soils, sludges, and wastewater treatment plants has been widely documented. Advanced oxidation processes (AOPs) have garnered extensive attention for abetment of emerging pharmaceutical contaminants and minimize their associated environmental risks. Given a clean and efficient oxidizing agent, hydrogen peroxide (H2O2) has been extensively utilized in AOPs. Integration of H(2)O(2 )with different substrates/catalysts boosts up its oxidizing features. H(2)O(2 )may be combined with ozone, UV, Fe2+/Fe3+ ions (Fenton and photo-Fenton-like processes) and with heterogeneous systems (TiO2). The generation of strong oxidative hydroxyl radical (HO:) in H2O2-assisted AOP by various types of activating methods is likely to play a critical role in micropollutants treatment, reusing, and risk reduction. Advanced oxidation process catalyzed by H(2)O(2)may consists of combination of following catalysts: UV/H2O2, O-3/UV/ H2O2, H2O2/TiO2/UV, Fe2+/H2O2, Fe2+/H2O2/UV, Electro-Fenton, O3/H2O2). In this review, we have discussed current reports on various hydrogen peroxide-based advanced oxidation processes for degradation of pharmaceutical pollutants of emerging concern. The ongoing challenges, conclusive remarks and imperative future directions are also outlined. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Background: Coumarin is an oxygen-containing compound in medicinal chemistry. Coumarin plays an important role in both natural systems like plants and synthetic medicinal applications as drug molecules. Many structurally different coumarin compounds have been found to possess a wide range of similarities with the vital molecular targets in terms of their pharmacological action and small modifications in their structures, resulting in significant changes in their biological activities. Objective: This review provides detailed information regarding the studies focused on the recent advances in various pharmacological aspects of coumarins. Method: Various oxygen-containing heterocyclic compounds represent remarkable biological significance. The fused aromatic oxygen-heterocyclic nucleus can change its electron density, thus altering the chemical, physical and biological properties, respectively, due to its multiple binding modes with the receptors, which play a crucial role in the pharmacological screening of drugs. Several heterocyclic compounds have been synthesized which have their nuclei derived from various plants and animals. In coumarins, the benzene ring is fused with a pyrone nucleus which provides stability to the nucleus. Coumarins have shown a wide range of pharmacological activities, such as anti-tumor, anticoagulant, anti-inflammatory, anti-oxidant, antiviral, antimalarial, anti-HIV, antimicrobial, etc. Results: Reactive oxygen species, like superoxide anion, hydroxyl radical, and hydrogen peroxide, are a type of unstable molecule containing oxygen, which reacts with other molecules in the cell during metabolism; however, when the number of reactive oxygen species increases, it may lead to cytotoxicity, thereby damaging the biological macromolecules. Hydroxyl Radical (OH) is a strong oxidizing agent and it is responsible for the cytotoxicity caused by oxygen in different plants, animals, and other microbes. Coumarin is the oldest and effective compound having antimicrobial, anti-inflammatory, antioxidant, antidepressant, analgesic, anticonvulsant activities, etc. Naturally existing coumarin compounds act against SARS-CoV-2 by preventing viral replication and targeting the active site against the Mpro target protein. Conclusion: This review highlights the different biological activities of coumarin derivatives. In this review, we provide an updated summary of the researches which are related to recent advances in biological activities of coumarins analogs and their most recent activities against COVID -19. Natural compounds act as a rich resource for novel drug development against various SARS-CoV-2 viral strains and viruses, like herpes simplex virus, influenza virus, human immunodeficiency virus, hepatitis B and C viruses, middle east respiratory syndrome, and severe acute respiratory syndrome.

The toxic potential of H2O2 is limited, even if intracellular concentrations of H2O2 under conditions of oxidative stress increase to the micromolar concentration range. Its toxicity is mostly restricted to the oxidation of highly reactive thiol groups, some of which are functionally very important. Subsequently, the HO· radical is generated spontaneously from H2O2 in the Fenton reaction. The HO· radical is extremely toxic and destroys any biological structure. Due to the high reactivity, its action is limited to a locally restricted site of its generation. On the other hand, H2O2 with its stability and long half-life can reach virtually any site and distribute its toxic effect all over the cell. Thereby HO·, in spite of its ultra-short half-life (10–9 s), can execute its extraordinary toxic action at any target of the cell. In this oxidative stress scenario, H2O2 is the pro-radical, that spreads the toxic action of the HO· radical. It is the longevity of the H2O2 molecule allowing it to distribute its toxic action from the site of origin all over the cell and may even mediate intercellular communication. Thus, H2O2 acts as a spreader by transporting it to sites where the extremely short-lived toxic HO· radical can arise in the presence of “free iron”. H2O2 and HO· act in concert due to their different complementary chemical properties. They are dependent upon each other while executing the toxic effects in oxidative stress under diabetic metabolic conditions in particular in the highly vulnerable pancreatic beta cell, which in contrast to many other cell types is so badly protected against oxidative stress due to its extremely low H2O2 inactivating enzyme capacity.

The difficulty in Fe(III)/Fe(II) conversion in the Fe(III)/peroxymonosulfate (PMS) process limits its efficiency and application. Herein, L-cysteine (Cys), a green natural organic ligand with reducing capability, was innovatively introduced into Fe(III)/PMS to construct an excellent Cys/Fe(III)/PMS process. The Cys/Fe(III)/PMS process, at room temperature, can degrade a variety of organic contaminants, including dyes, phenolic compounds, and pharmaceuticals. In subsequent experiments with acid orange 7 (AO7), the AO7 degradation efficiency followed pseudo-first-order kinetic which exhibited an initial “fast stage” and a second “slow stage”. The rate constant values ranged depending on the initial Cys, Fe(III), PMS, and AO7 concentrations, reaction temperature, and pH values. In addition, the presence of Cl−, NO3−, and SO42− had negligible impact while HCO3− and humic acid inhibited the degradation of AO7. Furthermore, radical scavenger experiments and methyl phenyl sulfoxide (PMSO) transformation assay indicated that sulfate radical, hydroxyl radical, and ferryl ion (Fe(IV)) were the dominant reactive species involved in the Cys/Fe(III)/PMS process. Finally, based on the results of gas chromatography-mass spectrometry, several AO7 degradation pathways, including N=N cleavage, hydroxylation, and ring opening were proposed. This study provided a new insight to improve the efficiency of Fe(III)/PMS process by accelerating Fe(III)/Fe(II) cycle with Cys.

Pig plasma contains a large amount of protein. Porcine plasma polypeptide can be prepared by the enzymatic hydrolysis of porcine plasma protein. The present study investigated the function, structure, and mechanisms of porcine plasma peptides.The results showed that WVRQAPGKGL had a major ability to scavenge hydroxyl radical scavenging activity (HRSA) (35.25%), 2,2'-azino-bis (3-ethylbenzothiazo line-6-sulfonic acid) diammonium salt radical scavenging activity (ABTS RSA) (93.09%) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH RSA) (25.72%), as well as in angiotensin converting enzyme (ACE) inhibition (91.64%). WVRQAPGKGL could inactivate ACE by binding to Zn2+ because of the presence of carboxyl in WVRQAPGKGL. The ACE inhibition, HRSA, and DPPH of synthetic WVRQAPGKGL were improved by 12.70%, 16.06%, and 117.11% respectively after in vitro digestion. It (0.1 mg mLA new difunctional (antioxidant and hypotensive) peptide, WVRQAPGKGL, derived from porcine plasma hydrolyzate was isolated by gel filtration and reverse phase chromatography, and identified by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS)

The atmospheric oxidation degradation of fluorotelomer acrylates (FTAcs) has been proposed as a potential source of perfluorocarboxylic acids (PFCAs) in remote locations. In this paper, detailed reactions of the main oxidant OH radicals with 4:2 FTAc in the atmosphere have been investigated by using density functional theory (DFT) calculation. All possible pathways involved in the oxidation process were presented and discussed. Based on the mechanism, transition state theory (TST) was used to predict the rate constants of the key elementary steps including the initial reactions of OH radical with n:2 FTAcs and the subsequent reactions of the main intermediates. Studies show that the reaction processes of OH radical addition to C = C bond are dominant and the fluorotelomer glyoxylate and formaldehyde are the major products. At 296 K, the calculated overall rate constant of 4:2 FTAc with OH radical is 1.19 × 10

Atmospheric nitrous acid (HONO) is a dominant precursor of hydroxyl (OH) radicals, and its formation mechanisms are still controversial. Few studies have simultaneously explored effects of different combustion processes on HONO sources. Hereby, synchronous HONO measurement in urban (BJ), suburban (XH) and rural (DBT) areas with different combustion processes is performed in the North China Plain in winter. A box model is utilized to analyze HONO formation mechanisms. HONO concentration is the highest at the DBT site (2.51 ± 1.90 ppb), followed by the XH (2.18 ± 1.95 ppb) and BJ (1.17 ± 1.20 ppb) sites. Vehicle exhaust and coal combustion significantly contribute to nocturnal HONO at urban and rural sites, respectively. During a stagnant pollution period, the NO+OH reaction and combustion emissions are more crucial to HONO in urban and rural areas; meanwhile, the heterogeneous reaction of NO

The leaching and non-recoverability of mental ions have always limited the practical application of Fenton-like processes. For the first time, we synthesized molybdenum phosphide (MoP) with dual active sites for the degradation of diclofenac (DCF) in the Fenton-like process. The DCF degradation rate constant (k) of MoP + H2O2 process was calculated to be 0.13 min-1 within 40 min, indicating a highly efficient catalytic ability of MoP. In addition, this catalyst exhibits a stable structure and good activity, which could apply in a broad pH range, different ions solution and real wastewater condition. Accordingly, this efficient catalytic capability may be attributed to the presence of the metal sites Moδ+ and the electron-rich sites Pδ− in MoP, which could induce the generation of hydroxyl radical (•OH) and superoxide radical (•O2−) through electron transfer, resulting in the effective removal of DCF. This study provides an idea for the optimization of Fenton-like technologies and environmental remediation.

The mechanism of reaction of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) with ·CH

Various semiconductor powders (such as bismuth oxybromide/bismuth oxyiodide (BiOBr/BiOI) nanojunctions) can photodegrade wastewater efficiently, but their practical application is limited by poor recovery performance. To address the problem, we report the construction of BiOBr/BiOI nanojunctions on flexible carbon fiber cloth (CFC) substrate as an easily recycled photocatalyst by the dipping-solvothermal-dipping-solvothermal four-step method. CFC/BiOBr/BiOI is composed of CFC substate and two layers of nanosheets, while BiOBr nanosheets (thickness: 10–30 nm, diameter: 200–400 nm) were grown in the inner layer and BiOI nanosheets (thickness: 50–80 nm, diameter:300–600 nm) were grown in the outer layer. CFC/BiOBr/BiOI (4 × 4 cm2) can effectively photodegrade 97.7% acid orange 7 (AO7), 91.3% levofloxacin (LVFX) and 97.8% tetracycline (TC) within 120 min under the illumination of visible-light, better than CFC/BiOBr (73.2% AO7, 71.6% LVFX and 81.6% TC). Furthermore, superoxide radical (•O2−) and hydroxyl radical (•OH) are the main active substances during removing LVFX by CFC/BiOBr/BiOI. Besides, CFC/BiOBr/BiOI can efficiently reduce 93.5% chemical oxygen demand (COD) concentration of acrylic resin production wastewater (ARPW) under visible-light illumination for 3 h, better than CFC/BiOBr (36.6% COD). Therefore, CFC/BiOBr/BiOI has broad application prospects in purifying wastewater as a new type of easily recycled photocatalyst.

The rational integration of chemotherapy and hydroxyl radical (·OH)-mediated chemodynamic therapy (CDT) via functional metal-organic frameworks (MOF) carriers has great potential in cancer therapy. In this work, aminotriazole (3-AT) doped polyhedral metal organic frameworks (denoted as MAF) were prepared by template ligand replacement, where CDT was initiated by Cu2+/Cu+ modulated Fenton reaction and enhanced by effectively regulating the catalase activity with 3-AT. However, a rod-like Cu-MOF with 3-AT served as a ligand was obtained by the hydrothermal method without using template. In contrast to Cu-MOF, pH-responsive MAF was chosen as the carrier for targeted drug delivery due to its higher drug load of 17.6% and relatively uniform size, where doxorubicin (DOX) as a model drug was loaded in its cavity and hyaluronic acid (HA) was coated on its surface via electrostatic interactions (denoted as HA-MAF@DOX). In vitro experiments demonstrated that HA-MAF@DOX had high transport efficiency of DOX, effective regulation of catalase (CAT) activity and enhanced cytotoxicity to HepG2 cells. This work is the first use of enzyme inhibitors as ligands to construct functional MOFs via template ligand replacement for effective regulating enzyme activity, mediating intracellular redox homeostasis and enhancing CDT efficacy, which provides a feasible strategy for the construction the functional MOFs in cancer therapy.

Photochemical and microbial processing are the prevailing mechanisms that shape the composition and reactivity of dissolved organic matter (DOM); however, prior research has not comparatively evaluated the impacts of these processes on the photoproduction of reactive intermediates (RIs) from freshly sourced terrestrial DOM. We performed controlled irradiation and incubation experiments with leaf and soil samples collected from an acid-impacted lake watershed in the Adirondack Mountain region of New York to examine the effects of DOM processing on the apparent quantum yields of RIs (Φapp,RI), including excited triplet states of DOM (3DOM*), singlet oxygen (1O2), and hydroxyl radicals (•OH). Photodegradation led to net reductions in Φapp,1O2, Φapp,3DOM*, and Φapp,•OH, whereas (photo-)biodegradation resulted in increases in Φapp,1O2 and Φapp,3DOM*. Photodegradation and (photo-)biodegradation also shifted the energy distribution of 3DOM* in different directions. Multivariate statistical analyses revealed the potential relevance of photo-biodegradation in driving changes in Φapp,1O2 and Φapp,3DOM* and prioritized five bulk DOM optical and redox properties that best explained the variations in Φapp,1O2 and Φapp,3DOM* along the watershed terrestrial-aquatic continuum. Our findings highlight the contrasting impacts of photochemical and microbial processes on the photoreactivity of freshly sourced terrestrial DOM and invite further studies to develop a more holistic understanding of their implications for aquatic photochemistry., Photochemical and microbial processing exert divergent effects on the photoproduction of reactive intermediates from dissolved organic matter sourced from an acid-impacted Adirondack lake watershed.

This study synthesized UiO-66 (Zr) in situ on wood via a one-step solvothermal method. UiO-66/wood was successfully prepared and its catalytic performance for the ofloxacin (OFX) photodegradation under simulate sunlight was also explored. UiO-66/wood exhibited a better catalytic performance, and its degradation rate constant was about 1.2 and 1.5 times than that of UiO-66 and wood, respectively. The effects of solution initial concentration, pH of the system and dosage of the photocatalyst were explored. Additionally, the active species trapping experiments and UV–vis diffused reflectance spectra measurements were conducted to investigated the photocatalytic mechanism of the UiO-66/wood composite, superoxide radical (O2•–) and hydroxyl radical (•OH) were the main reactive species. In addition, the possible degradation pathways of OFX were analyzed by LC-MS. Meanwhile, the UiO-66/wood showed outstanding stability and reusability after 4 cycles experiments. The removal performance of UiO-66/wood towards real samples showed it has potential in actual application .

The antioxidant capacity of β-carotene has been studied in terms of H-atom abstraction reactions using quantum chemical methods. These oxidation reactions are studied for the all-trans as well as 15,15'-cis isomers (15Z) of β-carotene, as the latter is only ~ 10 kJ/mol less stable than the all-trans isomer in the gas phase and about 9 kJ/mol less stable in aqueous solution. Hydrogen abstraction from the rotamers obtained through C-C single and double bond rotations has been shown to play an important role in determining the antioxidant capacity of β-carotene. Hydrogen abstraction from the C4 and C5-CH3 positions of the β-ionone rings and the C7 and C9 positions along the polyene chain of β-carotene by hydroxyl radical have been studied. In the all-trans form the most favorable H-atom abstraction reaction occurs at the C4 position of the terminal regions of the polyene -system of β-carotene, closely followed by hydrogen abstraction from the C5 methyl position. The H-atom abstraction reactions are more exothermic in water than in the gas phase due to solvation energies for the water product.

There is evidence that contaminants can transform at the elevated temperatures of thermal remediation; however, the contribution of redox active minerals to transformation has not been investigated. Three redox active minerals (

This study aimed to treat toxic and refractory organic wastewater, and to address the limitations of Fenton method in treating organic wastewater, that the active components are easy to lose and usually operate at the pH value of 2 ∼ 3. In the present study, CuCe oxide catalyst was produced through citric acid-assisted complexation. Besides, the structural stability and catalytic wet peroxide oxidation (CWPO) performance of the catalyst after 5 times of application were delved into by characterization. The effects of catalyst dosage and pH on quinoline removal were ascertained, while the reusability of the catalyst was explored. Moreover, the variations of pH, hydroxyl radical concentration and UV–Vis spectra in the reaction system were analyzed. The possible degradation pathway and the catalytic mechanism were also discussed. As suggested from the results, the catalyst exhibited high catalytic activity, structural stability and pH adaptability; it also had high CWPO performance for quinoline at the pH from 3.8 to 10.5, and the pH value need not be regulated. Under optimal conditions, 98.1% of quinoline and 86.1% of total organic carbon (TOC) were removed. In the CWPO process of quinoline, the ·OH attacked the nitrogen ring and the benzene ring in sequence.

Dissolved organic matter (DOM) can facilitate the transformation of contaminants through the production of reactive intermediates, such as singlet oxygen (1O2), and hydroxylating species (˙OH and other intermediates of similar reaction chemistry).

The combination of chemotherapy (CT) and chemodynamic therapy (CDT) is an emerging therapeutic strategy for tumors; however, its therapeutic efficacy is usually impaired by the shortage of high-efficiency intracellular catalysts for CDT and the poor tumor selectivity of CT. To address this concern, novel carrier-free nanodrugs (CMC-DD2) self-assembled from the natural melanin complex (CMC) with a superior CDT performance, and dehydroabietic acid hexamer (DD2) displaying a potent antitumor activity were proposed for the synergistic combination of CT and CDT. CMC-DD2 preferred to enter tumor cells and localize in the nucleus after lysosome escape due to its pH-dependent charge-reversal properties. Nanodrugs internalized by the nucleus directly bound the DNA and altered its conformation. Then, the dissociation of CMC-DD2 was efficiently triggered by intracellular hydrogen peroxide (H2O2) with the release of DNA damaging agents, including nitrate anions, hydroxyl radicals (●OH) and DD2. Finally, severe DNA damage induced mitochondrial apoptosis in HepG2 cells. An in vivo assessment further demonstrated the superior tumor selectivity and suppressor capacity and no/low toxicity of the nanodrugs. Overall, novel carrier-free, charge-reversal, nucleus-targeting, biodegradable, and DNA-affinity nanodrugs represent safe and effective platforms for the combination of CT and CDT.

[ES] La alta escasez de agua y el constante incremento en la industrialización ha propiciado el deterioro de las reservas de agua como consecuencia de la excesiva generación y liberación de desechos contaminantes. Actualmente, se han reportado una gran variedad de contaminantes de diferente naturaleza, entre ellos se pueden mencionar los microplásticos (MPs) que han sido detectados en agua potable e incluso en animales para la ingesta humana lo cual puede acarrear graves problemas de salud. Cabe mencionar que uno de los mayores problemas a nivel medioambiental de los MPs radica en su alta estabilidad, ya que los métodos habituales utilizados para la eliminación de contaminantes no ejercen efecto. En este sentido, los Procesos de Oxidación Avanzada (POAs) han surgido como una alternativa a la eliminación de contaminantes de difícil degradación, debido a la generación principalmente de radicales hidroxilo que tienen un elevado potencial de oxidación y son muy poco selectivos. En este trabajo nos hemos centrado en el uso del proceso foto-Fenton, con sales de hierro y peróxido de hidrógeno e utilizando la luz solar como fuente de radiación, para llevar a cabo la degradación de MPs, específicamente la poliamida 6,6 (PA66), a pesar de que este polímero no es propiamente un plástico, la literatura lo considera dentro de ellos debido a su importancia como contaminante. A partir de PA66 obtenida de la industria textil, se evaluó el proceso de degradación con distintas técnicas y métodos analíticos destacando entre ellos la microscopía FESEM y la espectroscopía TF-IR. Se realizaron estudios en simulador solar en condiciones habituales de trabajo de procesos foto-Fenton (5 mg/L de Fe, 10 mg/L de H2O2 y pH = 2.8) y qué efectos podían producir tanto el tiempo de radiación como la presencia de una matriz natural como la salinidad en las aguas de tratamiento. Además, se realizaron estudios para confirmar que el proceso de degradación de la PA66 observado (numerosas imperfecciones aparecieron en la superficie del microplástico) era debido a la acción tanto del radical hidroxilo como del radical superóxido utilizando secuestrantes de ambos y comparando los procesos. Posteriormente se evaluó la degradación de la PA66 a nivel planta piloto utilizando dos diferentes fuentes de irradiación: LED vis y LED vis + solar realizando para ello, un estudio previo de diseño de experimentos tipo Doehlert para minimizar recursos y residuos y obtener las óptimas condiciones de tratamiento de la PA66 y, con base a estas condiciones se comparó la degradación de 4 diferentes MPs: PA66, poliamida 6 (PA6), aramida y poliéster (PES). Por último, se estudió la degradación de la PA66 bajo estas mismas condiciones en un periodo de 100 h. Los estudios de estabilidad mostraron que la PA66 no presenta fotólisis ni hidrólisis y los ensayos de degradación mediante el proceso foto-Fenton en un periodo de 7 h mostraron la formación de defectos sobre la superficie de la PA66 y disminución de grupos funcionales de acuerdo microscopia FESEM y FTIR, asimismo, el MP mostró cambios en su punto de fusión a diferentes tiempos de tratamiento como consecuencia de la rotura de las cadenas del polímero. Este mismo efecto se observó en un tiempo de degradación de 100 h de la PA66 con un aumento en el número y diámetro de defectos formados. La adición de NaCl a 30 g/L (alta salinidad) provocó una disminución en el daño generado debido a la reacción de los radicales hidroxilo y formación de especies reactivas con menor potencial de oxidación. La adición de 2-propanol y p-benzoquinona como atrapadores del radical hidroxilo y anión superóxido corroboraron esta suposición. La PA66 tratada en planta piloto mediante el uso de radiación LED vis + solar presentó un mayor grado de degradación en comparación con la tratada únicamente con radiación LED vis (incremento de 90 veces más el área superficial especifica de la PA66 tratada con respecto a la PA66 sin tratamiento)., [CA] L'alta escassetat d'aigua i el constant increment en la industrialització ha propiciat la deterioració dels cossos d'aigua a conseqüència de l'excessiva generació i alliberament de deixalles contaminants. Actualment, s'han reportat una gran varietat de contaminants de diferent naturalesa, entre ells es poden esmentar els microplàstics (MPs) que han sigut detectats en aigua potable i fins i tot en animals per a la ingesta humana la qual cosa pot implicar greus problemes de salut. Cal esmentar que un dels majors problemes a nivell mediambiental dels MPs radica en la seua alta estabilitat, ja que els mètodes habituals utilitzats per a l'eliminació de contaminants no exerceixen cap efecte. En aquest sentit, els Processos d'Oxidació Avançada (POAs) han sorgit com una alternativa a l'eliminació de contaminants de difícil degradació, a causa de la generació principalment de radicals hidroxil que tenen un elevat potencial d'oxidació i són molt poc selectius. En aquest treball ens hem centrat en l'ús del procés foto-Fenton, amb sals de ferro i peròxid d'hidrogen e utilitzant la llum solar com a font de radiació, per a dur a terme la degradació de MPs, específicament la poliamida 6,6 (PA66). A partir de PA66 obtinguda de la indústria tèxtil, es va avaluar el procés de degradació amb diferents tècniques i mètodes analítics destacant entre ells la microscòpia FESEM i la espectroscopía FT-IR. Es van realitzar estudis en simulador solar en condicions habituals de treball de processos foto-Fenton (5 mg/L de Fe, 10 mg/L de H2O2 i pH = 2.8) i quins efectes podien produir tant el temps de radiació com la presència d'una matriu natural com la salinitat en les aigües de tractament. A més, es van realitzar estudis per a confirmar que el procés de degradació de la PA66 observat (nombroses imperfeccions van aparèixer en la superfície del microplàstic) era degut a l'acció tant del radical hidroxil com del radical superòxid utilitzant segrestants de tots dos i comparant els processos. Posteriorment es va avaluar la degradació de la PA66 a nivell planta pilot utilitzant dues diferents fonts d'irradiació: LED vis i LED-vis + solar realitzant per a això, un estudi previ de disseny d'experiments tipus Doehlert per a minimitzar recursos i residus i obtindre les òptimes condicions de tractament de la PA66 i, amb base a aquestes condicions es va comparar la degradació de 4 diferents MPs (PA66, PA6, Aramida i PES). Finalment, es va estudiar la degradació de la PA66 sota aquestes mateixes condicions en un període de 100 h. Els estudis d'estabilitat van mostrar que la PA66 no presenta fotòlisis ni hidròlisi i els assajos de degradació mitjançant el procés foto-Fenton en un període de 7 h van mostrar la formació de defectes sobre la superfície de la PA66 i disminució de grups funcionals d'acord microscòpia FESEM i FT-IR, així mateix, el MP va mostrar canvis al punt de fusió a diferents temps de tractament a conseqüència del trencament de les cadenes del polímer. Aquest mateix efecte es va observar en un temps de degradació de 100 h de la PA66 amb un augment en el nombre de defectes formats i diàmetre dels defectes. L'addició de NaCl a 30 g/L (alta salinitat) va provocar una disminució en el mal generat a causa del secuestrament dels radicals hidroxil i formació d'espècies reactives amb menor potencial d'oxidació. L'addició de 2-propanol i p-benzoquinona com atrapadores del radical hidroxil i anió superòxid van corroborar aquesta suposició. La PA66 tractada en planta pilot mitjançant l'ús de radiació LED-vis + solar va presentar un major grau de degradació en comparació amb la tractada únicament amb radiació LED-vis (increment de 90 vegades més l'àrea superficial especifica de la PA66 tractada respecte a la PA66 sense tractament). L'avaluació de la degradació dels 4 MPs va mostrar que el PES i la aramida no són degradables en aquestes condicions i la PA6 va presentar una menor degradació que la PA66., [EN] The high scarcity of water and the constant increase in industrialization has led to the deterioration of water bodies as a consequence of the excessive generation and release of pollutant wastes. Currently, a great variety of pollutants of different nature have been reported, among them we can mention microplastics (MPs) that have been detected in drinking water and even in animals for human consumption, which can cause serious health problems. It is worth mentioning that one of the biggest environmental problems of MPs lies in their high stability, since the usual methods used for the elimination of contaminants have no effect. In this sense, Advanced Oxidation Processes (AOPs) have emerged as an alternative for the removal of pollutants that are difficult to degrade, mainly due to the generation of hydroxyl radicals that have a high oxidation potential and are not very selective. In this work we have focused on the use of the photo-Fenton process, with iron salts and hydrogen peroxide and using sunlight as a source of radiation, to carry out the degradation of PMs, specifically polyamide 6,6 (PA66), despite that this polymer is not a plastic, literature considers it among them due to its importance as a pollutant. Using PA66 obtained from the textile industry, the degradation process was evaluated with different techniques and analytical methods, among them FESEM microscopy and TF-IR spectroscopy. Studies were carried out in a solar simulator under usual working conditions of photo-Fenton processes (5 mg/L Fe, 10 mg/L H2O2 and pH = 2.8) and it was studied the effect by the radiation time and the presence of a natural matrix such as salinity in the treatment water. In addition, studies were conducted to confirm that the PA66 degradation process observed (numerous imperfections appeared on the surface of the microplastic) was due to the action of both oxygen species (hydroxyl radical and the superoxide radical) by using scavengers of both and comparing the processes. Subsequently, PA66 degradation was evaluated at pilot plant level using two different irradiation sources: LED vis and LED vis + solar, a previous study of Doehlert type design of experiments to minimize resources and waste and obtain the optimal conditions for PA66 treatment and, based on these conditions the degradation of 4 different MPs: PA66, polyamide 6 (PA6), aramid and polyethylene (PES) was compared. Finally, the degradation of PA66 under these same conditions was studied over a period of 100 h. The stability studies showed that PA66 does not present photolysis or hydrolysis and the degradation tests by the photo-Fenton process in a period of 7 h showed the formation of defects on the surface of PA66 and decrease of functional groups according to FESEM and FTIR microscopy, also, the MP showed changes in its melting point at different treatment time as a result of the breaking of the polymer chains. This same effect was observed at a degradation time of 100 h of PA66 with an increase in the number of defects formed and in their diameters. The addition of NaCl at 30 g/L (high salinity) caused a decrease in the damage generated due to the reaction of hydroxyl radicals and formation of reactive species with lower oxidation potential. The addition of 2-propanol and p-benzoquinone as hydroxyl radical and superoxide anion scavengers corroborated this assumption. PA66 treated in pilot plant using LED vis + solar irradiation showed a higher degree of degradation compared to PA66 treated only with LED vis irradiation (90-fold increase in the specific surface area of treated PA66 with respect to untreated PA66). The evaluation of the degradation of the 4 MPs showed that PES and aramid are not degradable under these conditions and PA6 presented a lower degradation than PA66.

The oxidation of widely-used herbicide metazachlor (MTZ) by hydroxyl radical (HO