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Environmental Science & Technology Jun 2024Hydrogen-tuned 185 nm vacuum ultraviolet (VUV/H) photolysis is an emerging technology to destroy per- and polyfluoroalkyl substance (PFAS) in brine. This study...
Promotive Effects of Chloride and Sulfate on the Near-Complete Destruction of Perfluorocarboxylates (PFCAs) in Brine via Hydrogen-tuned 185-nm UV Photolysis: Mechanisms and Kinetics.
Hydrogen-tuned 185 nm vacuum ultraviolet (VUV/H) photolysis is an emerging technology to destroy per- and polyfluoroalkyl substance (PFAS) in brine. This study discovered the promotive effects of two major brine anions, i.e., chloride and sulfate in VUV/H photolysis on the hydrated electron (e) generation and perfluorocarboxylates (PFCAs) destruction and established a kinetics model to elucidate the promotive effects on the steady-state concentration of e ([e]). Results showed that VUV/H achieved near-complete defluorination of perfluorooctanoic acid (PFOA) in the presence of up to 1000 mM chloride or sulfate at pH 12. The defluorination rate constant () of PFOA peaked with a chloride concentration at 100 mM and with a sulfate concentration at 500 mM. The promotive effects of chloride and sulfate were attributed to an enhanced generation of e via their direct VUV photolysis and conversion of additionally generated hydroxyl radical to e by H, which was supported by a linear correlation between the predicted [e] and experimentally observed . The value increased from pH 9 to 12, which was attributed to the speciation of the H/e pair. Furthermore, the VUV system achieved >95% defluorination and ≥99% parent compound degradation of a concentrated PFCAs mixture in a synthetic brine, without generating any toxic perchlorate or chlorate.
Topics: Kinetics; Photolysis; Ultraviolet Rays; Fluorocarbons; Sulfates; Hydrogen; Chlorides; Salts; Water Pollutants, Chemical; Caprylates
PubMed: 38808621
DOI: 10.1021/acs.est.3c10552 -
The Journal of Organic Chemistry Jun 2024To address the scarcity of generally applicable photochemical routes to allenylidenes in solution, phenanthrene-based sources have been investigated. Specifically, the...
To address the scarcity of generally applicable photochemical routes to allenylidenes in solution, phenanthrene-based sources have been investigated. Specifically, the syntheses of 1-vinylidene-1a,9b-dihydro-1-cyclopropa[]phenanthrene, 1-(2-phenylvinylidene)-1a,9b-dihydro-1-cyclopropa[]phenanthrene, and 1-(2-methylvinylidene)-1a,9b-dihydro-1-cyclopropa[]phenanthrene, photochemical precursors to propadienylidene, 3-phenylpropadienylidene, and 3-methylpropadienylidene have been carried out. Photolysis of these new precursors in olefin traps and benzene afforded the expected cyclopropane adducts of the corresponding allenylidenes. Quantum chemical calculations show that the ground state of all three carbenes is a singlet with a singlet-triplet gap of ∼29, 30, and 33 kcal/mol for propadienylidene, 3-phenylpropadienylidene, and 3-methylpropadienylidene, respectively.
PubMed: 38808505
DOI: 10.1021/acs.joc.4c00147 -
PloS One 2024The examination of photocatalyst powders for the total removal of pollutants from aqueous solutions is a vital research subject within the realm of environmental...
The examination of photocatalyst powders for the total removal of pollutants from aqueous solutions is a vital research subject within the realm of environmental preservation. The objective of this study is to develop a photocatalyst heterojunction consisting of Zingiber/ZnO-H for the degradation of both the reactive red dye (RR 141) and ofloxacin antibiotic in wastewater. The current investigation outlines the process of synthesising a composite material by combining Zingiber montanum extract with zinc oxide (ZnO) by a hydrothermal method. The synthesis was conducted at a temperature of 180°C for a period of 4 hours. Consequently. The photocatalyst with a constructed heterojunction shown a notable enhancement in its photocatalytic activity as a result of the improved efficiency in charge separation at the interface. The application of economically viable solar energy facilitated the complete eradication of harmful pollutants through the process of detoxification. The removal of impurities occurs by a process that follows a first-order kinetics. Among the pollutants, RR141 demonstrates the greatest rate constant at 0.02 min-1, while ofloxacin has a rate constant of 0.01 min-1. The assessment of the stability of the produced photocatalyst was conducted after undergoing five cycles. This study additionally investigated the influence of sunshine on degradation, uncovering degradation rates of 97% for RR141 and 99% for ofloxacin when exposed to UV Lamp, and degradation rates of 97% for RR141 and 95% for ofloxacin when exposed to Solar Light.
Topics: Zinc Oxide; Ofloxacin; Anti-Bacterial Agents; Photolysis; Azo Compounds; Water Pollutants, Chemical; Catalysis; Kinetics
PubMed: 38805514
DOI: 10.1371/journal.pone.0300402 -
Life (Basel, Switzerland) May 2024Fixed nitrogen species generated by the early Earth's atmosphere are thought to be critical to the emergence of life and the sustenance of early metabolisms. A previous...
Fixed nitrogen species generated by the early Earth's atmosphere are thought to be critical to the emergence of life and the sustenance of early metabolisms. A previous study estimated nitrogen fixation in the Hadean Earth's N/CO-dominated atmosphere; however, that previous study only considered a limited chemical network that produces NO species (i.e., no HCN formation) via the thermochemical dissociation of N and CO in lightning flashes, followed by photochemistry. Here, we present an updated model of nitrogen fixation on Hadean Earth. We use the Chemical Equilibrium with Applications (CEA) thermochemical model to estimate lightning-induced NO and HCN formation and an updated version of KINETICS, the 1-D Caltech/JPL photochemical model, to assess the photochemical production of fixed nitrogen species that rain out into the Earth's early ocean. Our updated photochemical model contains hydrocarbon and nitrile chemistry, and we use a Geant4 simulation platform to consider nitrogen fixation stimulated by solar energetic particle deposition throughout the atmosphere. We study the impact of a novel reaction pathway for generating HCN via HCN, inspired by the experimental results which suggest that reactions with CH radicals (from CH photolysis) may facilitate the incorporation of N into the molecular structure of aerosols. When the HCN reactions are added, we find that the HCN rainout rate rises by a factor of five in our 1-bar case and is about the same in our 2- and 12-bar cases. Finally, we estimate the equilibrium concentration of fixed nitrogen species under a kinetic steady state in the Hadean ocean, considering loss by hydrothermal vent circulation, photoreduction, and hydrolysis. These results inform our understanding of environments that may have been relevant to the formation of life on Earth, as well as processes that could lead to the emergence of life elsewhere in the universe.
PubMed: 38792622
DOI: 10.3390/life14050601 -
Molecules (Basel, Switzerland) May 2024With the rising incidence of various diseases in China and the constant development of the pharmaceutical industry, there is a growing demand for floxacin-type...
With the rising incidence of various diseases in China and the constant development of the pharmaceutical industry, there is a growing demand for floxacin-type antibiotics. Due to the large-scale production and high cost of waste treatment, the parent drug and its metabolites constantly enter the water environment through domestic sewage, production wastewater, and other pathways. In recent years, the pollution of the aquatic environment by floxacin has become increasingly serious, making the technology to degrade floxacin in the aquatic environment a research hotspot in the field of environmental science. Metal-organic frameworks (MOFs), as a new type of porous material, have attracted much attention in recent years. In this paper, four photocatalytic materials, MIL-53(Fe), NH-MIL-53(Fe), MIL-100(Fe), and g-CN, were synthesised and applied to the study of the removal of ofloxacin and enrofloxacin. Among them, the MIL-100(Fe) material exhibited the best photocatalytic effect. The degradation efficiency of ofloxacin reached 95.1% after 3 h under visible light, while enrofloxacin was basically completely degraded. The effects of different materials on the visible photocatalytic degradation of the floxacin were investigated. Furthermore, the photocatalytic mechanism of enrofloxacin and ofloxacin was revealed by the use of three trappers (▪O, h, and ▪OH), demonstrating that the role of ▪O promoted the degradation effect of the materials under photocatalysis.
Topics: Metal-Organic Frameworks; Catalysis; Quinolones; Water Pollutants, Chemical; Photolysis; Light; Ofloxacin; Photochemical Processes; Anti-Bacterial Agents; Enrofloxacin
PubMed: 38792155
DOI: 10.3390/molecules29102294 -
Toxics Apr 2024Solar radiation triggers atmospheric nitrous acid (HONO) photolysis, producing OH radicals, thereby accelerating photochemical reactions, leading to severe secondary...
Solar radiation triggers atmospheric nitrous acid (HONO) photolysis, producing OH radicals, thereby accelerating photochemical reactions, leading to severe secondary pollution formation. Missing daytime sources were detected in the extensive HONO budget studies carried out in the past. In the rural North China Plain, some studies attributed those to soil emissions and more recent studies to dew evaporation. To investigate the contributions of these two processes to HONO temporal variations and unknown production rates in rural areas, HONO and related field observations obtained at the Gucheng Agricultural and Ecological Meteorological Station during spring and autumn were thoroughly analyzed. Morning peaks in HONO frequently occurred simultaneously with those of ammonia (NH) and water vapor both during spring and autumn, which were mostly caused by dew and guttation water evaporation. In spring, the unknown HONO production rate revealed pronounced afternoon peaks exceeding those in the morning. In autumn, however, the afternoon peak was barely detectable compared to the morning peak. The unknown afternoon HONO production rates were attributed to soil emissions due to their good relationship to soil temperatures, while NH soil emissions were not as distinctive as dew emissions. Overall, the relative daytime contribution of dew emissions was higher during autumn, while soil emissions dominated during spring. Nevertheless, dew emission remained the most dominant contributor to morning time HONO emissions in both seasons, thus being responsible for the initiation of daytime OH radical formation and activation of photochemical reactions, while soil emissions further maintained HONO and associated OH radial formation rates at a high level, especially during spring. Future studies need to thoroughly investigate the influencing factors of dew and soil emissions and establish their relationship to HONO emission rates, form reasonable parameterizations for regional and global models, and improve current underestimations in modeled atmospheric oxidation capacity.
PubMed: 38787110
DOI: 10.3390/toxics12050331 -
Chemosphere Aug 2024As global effects of water scarcity raise concerns and environmental regulations evolve, contemporary wastewater treatment plants (WWTPs) face the challenge of...
Continuous UV-C/HO and UV-C/Chlorine applied to municipal secondary effluent and nanofiltration retentate: Removal of contaminants of emerging concern, ecotoxicity, and reuse potential.
As global effects of water scarcity raise concerns and environmental regulations evolve, contemporary wastewater treatment plants (WWTPs) face the challenge of effectively removing a diverse range of contaminants of emerging concern (CECs) from municipal effluents. This study focuses on the assessment of advanced oxidation processes (AOPs), specifically UV-C/HO and UV-C/Chlorine, for the removal of 14 target CECs in municipal secondary effluent (MSE, spiked with 10 μg L of each CEC) or in the subsequent MSE nanofiltration retentate (NF, no spiking). Phototreatments were carried out in continuous mode operation, with a hydraulic retention time of 3.4 min, using a tube-in-tube membrane photoreactor. For both wastewater matrices, UV-C photolysis (3.3 kJ L) exhibited high efficacy in removing CECs susceptible to photolysis, although lower treatment performance was observed for NF. In MSE, adding 10 mg L of HO or Cl enhanced treatment efficiency, with UV-C/HO outperforming UV-C/Chlorine. Both UV-C/AOPs eliminated the chronic toxicity of MSE toward Chlorella vulgaris. In the NF, not only was the degradation of target CECs diminished, but chronic toxicity to C. vulgaris persisted after both UV-C/AOPs, with UV-C/Chlorine increasing toxicity due to potential toxic by-products. Nanofiltration permeate (NF) exhibited low CECs and microbial content. A single chlorine addition effectively controlled Escherichia coli regrowth for 3 days, proving NF potential for safe reuse in crop irrigation (<1 CFU/100 mL for E. coli; <1 mg L for free chlorine). These findings provide valuable insights into the applications and limitations of UV-C/HO and UV-C/Chlorine for distinct wastewater treatment scenarios.
Topics: Hydrogen Peroxide; Ultraviolet Rays; Wastewater; Water Pollutants, Chemical; Waste Disposal, Fluid; Chlorine; Filtration; Photolysis; Water Purification; Chlorella vulgaris; Escherichia coli; Oxidation-Reduction
PubMed: 38768787
DOI: 10.1016/j.chemosphere.2024.142355 -
Environmental Science and Pollution... May 2024Water pollution due to emerging contaminants, e.g., pharmaceuticals, is one of the most frequently discussed issues. Among them, paracetamol received great attention due...
Water pollution due to emerging contaminants, e.g., pharmaceuticals, is one of the most frequently discussed issues. Among them, paracetamol received great attention due to its physico-chemical properties, persistence, and adverse environmental effects. Different techniques were employed for its degradation and, among them, photodegradation is considered one of the most suitable to pursue the aim. This work aimed to synthesize mesoporous TiO, even with the presence of iron, through a one-pot method, with an enhanced ability to abate paracetamol. Precisely, pure and iron-containing (3.5 wt%) TiO were successfully obtained employing an uncommon procedure for this kind of material, mainly solution combustion synthesis (SCS). Moreover, a traditional hydrothermal method and a commercial Degussa P25 were also investigated for comparison purposes. The samples were characterized through N-physisorption at - 196 °C, XRD, XPS, EDX, DR UV-Vis, and FESEM analysis. The catalytic activity was investigated for the abatement of 10 ppm of paracetamol, under UV irradiation in acidic conditions (pH = 3) and in the presence of HO. As a whole, the best-performing catalysts were those obtained through the SCS procedure, highlighting a complete removal of the organic pollutant after 1 h in the case of Fe/TiO_SCS, thanks to its highly defective structure and the presence of metal Fe. To better investigate the performance of both pure and Fe-containing SCS samples, further oxidation tests were performed at pH = 7 and in the absence of HO. Noteworthy, in these conditions, the two samples exhibited different behaviors, highlighting different mechanisms depending on the presence or absence of iron in the structure. Finally, a kinetic study was conducted, demonstrating that a first order is suitable for its abatement.
Topics: Titanium; Acetaminophen; Catalysis; Photolysis; Iron; Water Pollutants, Chemical; Hydrogen Peroxide
PubMed: 38758438
DOI: 10.1007/s11356-024-33575-5 -
International Journal of Molecular... May 2024This current study assessed the impacts of morphology adjustment of perovskite BiFeO (BFO) on the construction and photocatalytic activity of P-infused g-CN/U-BiFeO...
This current study assessed the impacts of morphology adjustment of perovskite BiFeO (BFO) on the construction and photocatalytic activity of P-infused g-CN/U-BiFeO (U-BFO/PCN) heterostructured composite photocatalysts. Favorable formation of U-BFO/PCN composites was attained via urea-aided morphology-controlled hydrothermal synthesis of BFO followed by solvosonication-mediated fusion with already synthesized P-g-CN to form U-BFO/PCN composites. The prepared bare and composite photocatalysts' morphological, textural, structural, optical, and photocatalytic performance were meticulously examined through various analytical characterization techniques and photodegradation of aqueous rhodamine B (RhB). Ellipsoids and flakes morphological structures were obtained for U-BFO and BFO, and their effects on the successful fabrication of the heterojunctions were also established. The U-BFO/PCN composite exhibits 99.2% efficiency within 20 min of visible-light irradiation, surpassing BFO/PCN (88.5%), PCN (66.8%), and U-BFO (26.1%). The pseudo-first-order kinetics of U-BFO/PCN composites is 2.41 × 10 min, equivalent to 2.2 times, 57 times, and 4.3 times of BFO/PCN (1.08 × 10 min), U-BFO, (4.20 × 10 min), and PCN, (5.60 × 10 min), respectively. The recyclability test demonstrates an outstanding photostability for U-BFO/PCN after four cyclic runs. This improved photocatalytic activity exhibited by the composites can be attributed to enhanced visible-light utilization and additional accessible active sites due to surface and electronic band modification of CN via P-doping and effective charge separation achieved via successful composites formation.
Topics: Catalysis; Bismuth; Photolysis; Rhodamines; Light; Ferric Compounds; Nitrogen Compounds; Titanium; Photochemical Processes; Nitriles; Kinetics; Graphite; Oxides; Calcium Compounds
PubMed: 38732166
DOI: 10.3390/ijms25094948 -
Water Research Jun 2024Photochemical processes are typically not incorporated in screening-level substance risk assessments due to the complexity of modeling sunlight co-exposures and...
Direct and indirect photodegradation in aquatic systems mitigates photosensitized toxicity in screening-level substance risk assessments of selected petrochemical structures.
Photochemical processes are typically not incorporated in screening-level substance risk assessments due to the complexity of modeling sunlight co-exposures and resulting interactions on environmental fate and effects. However, for many substances, sunlight exerts a profound influence on environmental degradation rates and ecotoxicities. Recent modeling advances provide an improved technical basis for estimating the effect of sunlight in modulating both substance exposure and toxicity in the aquatic environment. Screening model simulations were performed for 25 petrochemical structures with varied uses and environmental fate properties. Model predictions were evaluated by comparing the ratios of predicted exposure concentrations with and without light to the corresponding ratios of toxicity thresholds under the same conditions. The relative ratios of exposure and hazard in light vs. dark were then used to evaluate how inclusion of light modulates substance risk analysis. Results indicated that inclusion of light reduced PECs by factors ranging from 1.1- to 63-fold as a result of photodegradation, while reducing PNECs by factors ranging from 1- to 49-fold due to photoenhanced toxicity caused by photosensitization. Consequently, the presence of light altered risk quotients by factors that ranged from 0.1- to 17-fold, since the predicted increase in substance hazard was mitigated by the reduction in exposure. For many structures, indirect photodegradation decreases environmental exposures independently of the direct photolysis pathway which is associated with enhanced phototoxicity. For most of the scenarios and chemicals in the present work, photosensitization appears to be mitigated by direct and indirect degradation from sunlight exposure.
Topics: Risk Assessment; Photolysis; Water Pollutants, Chemical; Sunlight; Models, Theoretical
PubMed: 38728777
DOI: 10.1016/j.watres.2024.121677