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Toxics Feb 2024Florfenicol (FLO) is a widely used antibacterial drug, which is often detected in the environment. In this paper, the photolysis mechanism of FLO in water was...
Study on the Direct and Indirect Photolysis of Antibacterial Florfenicol in Water Using DFT/TDDFT Method and Comparison of Its Reactivity with Hydroxyl Radical under the Effect of Metal Ions.
Florfenicol (FLO) is a widely used antibacterial drug, which is often detected in the environment. In this paper, the photolysis mechanism of FLO in water was investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The focus of the study is to elucidate the direct photolysis mechanism of FLO in the water environment and the indirect photolysis of free radicals (·OH, ·NO, and ·SO) as active species. The effect of metal ions Ca/Mg/Zn on the indirect photolysis was also investigated. The results show that the direct photolysis of FLO involves C-C/C-N/C-S bond cleavage, the C5-S7 bond cleavage is most likely to occur, and the C17-C18 cleavage reaction is not easy to occur during the direct photodegradation of FLO. The indirect photolysis of FLO is more likely to occur in the environment than direct photolysis. The main indirect photolysis involves OH-addition, NO-addition, and SO-addition on benzene ring. The order of difficulty in the indirect photolysis with ·OH is C2 > C3 > C4 > C5 > C6 > C1, Ca can promote the indirect photolysis with ·OH, and Mg/Zn has a dual effect on the indirect photolysis with ·OH. In other words, Mg and Zn can inhibit or promote the indirect photolysis with ·OH. These studies provide important information for theoretical research on the environmental behavior and degradation mechanism of drug molecules.
PubMed: 38393222
DOI: 10.3390/toxics12020127 -
Chemical Science Sep 2023Mn(diimine)(CO)X (X = halide) complexes are critical components of chromophores, photo- and electrocatalysts, and photoactive CO-releasing molecules (photoCORMs). While...
Mn(diimine)(CO)X (X = halide) complexes are critical components of chromophores, photo- and electrocatalysts, and photoactive CO-releasing molecules (photoCORMs). While these entities have been incorporated into metal-organic frameworks (MOFs), a detailed understanding of the photochemical and chemical processes that occur in a permanently porous support is lacking. Here we site-isolate and study the photochemistry of a Mn(diimine)(CO)Br moiety anchored within a permanently porous MOF support, allowing for not only the photo-liberation of CO from the metal but also its escape from the MOF crystals. In addition, the high crystallinity and structural flexibility of the MOF allows crystallographic snapshots of the photolysis products to be obtained. We report these photo-crystallographic studies in the presence of coordinating solvents, THF and acetonitrile, showing the changing coordination environment of the Mn species as CO loss proceeds. Using time resolved experiments, we report complementary spectroscopic studies of the photolysis chemistry and characterize the final photolysis product as a possible Mn(ii) entity. These studies inform the chemistry that occurs in MOF-based photoCORMs and where these moieties are employed as catalysts.
PubMed: 37712014
DOI: 10.1039/d3sc03553k -
Journal of the American Chemical Society Nov 2023Photochemical homolysis of hydrogen peroxide (HO) occurs widely in nature and is a key source of hydroxyl radicals (·OH). The kinetics of HO photolysis play a pivotal...
Photochemical homolysis of hydrogen peroxide (HO) occurs widely in nature and is a key source of hydroxyl radicals (·OH). The kinetics of HO photolysis play a pivotal role in determining the efficiency of ·OH production, which is currently mainly investigated in bulk systems. Here, we report considerably accelerated HO photolysis at the air-water interface of microdroplets, with a rate 1.9 × 10 times faster than that in bulk water. Our simulations show that due to the quasiplanar conformational preference of HO at the air-water interface compared to the bulk or gas phase, the absorption peak in the spectrum of HO is significantly redshifted by 45 nm, corresponding to greater absorbance of photons in the sunlight spectrum and faster photolysis of HO. This discovery has great potential to solve current problems associated with ·OH-centered heterogeneous photochemical processes in aerosols. For instance, we show that accelerated HO photolysis in microdroplets could lead to markedly enhanced oxidation of SO and volatile organic compounds.
PubMed: 37914533
DOI: 10.1021/jacs.3c08101 -
Chemosphere Aug 2023Glucocorticoids (GCs), as endocrine disruptors, have attracted widespread attention due to their impacts on organisms' growth, development, and reproduction. In the...
Glucocorticoids (GCs), as endocrine disruptors, have attracted widespread attention due to their impacts on organisms' growth, development, and reproduction. In the current study, the photodegradation of budesonide (BD) and clobetasol propionate (CP), as targeted GCs, was investigated including the effects of initial concentrations and typical environmental factors (Cl, NO, Fe, and fulvic acid (FA)). The results showed that the degradation rate constants (k) were 0.0060 and 0.0039 min for BD and CP at concentration of 50 μg·L, and increased with the initial concentrations. Under the addition of Cl, NO, and Fe to the GCs/water system, the photodegradation rate was decreased with increasing Cl, NO, and Fe concentrations, which were in contrast to the addition of FA. Electron resonance spectroscopy (EPR) analysis and the radical quenching experiments verified that GCs could transition to the triplet excited states of GCs (GCs*) for direct photolysis under irradiation to undergo, while NO, Fe, and FA could generate ·OH to induce indirect photolysis. According to HPLC-Q-TOF MS analysis, the structures of the three photodegradation products of BD and CP were elucidated, respectively, and the phototransformation pathways were inferred based on the product structures. These findings help to grasp the fate of synthetic GCs in the environment and contribute to the understanding of their ecological risks.
Topics: Glucocorticoids; Photolysis; Nitrogen Dioxide; Water; Water Pollutants, Chemical; Kinetics
PubMed: 37119927
DOI: 10.1016/j.chemosphere.2023.138799 -
Environmental Research Jul 2023Titanium oxide-based photocatalysts (TOBPs) have been widely utilized as potential materials for numerous applications, such as wastewater treatment, water-splitting... (Review)
Review
Titanium oxide-based photocatalysts (TOBPs) have been widely utilized as potential materials for numerous applications, such as wastewater treatment, water-splitting reactions, carbon dioxide (CO) reduction and photosynthesis. However, the large bandgap of intrinsic TiO limits their absorption toward visible light, which is the central part of the solar spectrum, resulting in low photocatalytic activities under sunlight. To overcome this obstacle, several strategies, such as doping with either metal or non-metal elements or combining with other compounds, are efficient ways to reduce the bandgap of TiO, leading to effectively extending their absorption toward the visible region and increasing their catalytic performance. In this review, we discussed the application of TOBPs for the photodegradation of hazardous organic pollutants in wastewater to produce quality reused water. The synthesis of TiO and the enhancement of photocatalytic activities of TOBPs by different techniques with detailed information were provided. Application of TOBPs for decomposing hazardous organic pollutants such as dyes, phenolic compounds and pharmaceuticals under optimum conditions have been listed. Also, the photodegradation mechanisms of hazardous organic compounds have been investigated. This work also brings ideas for future perspectives and research plan to inhibit the disadvantages and expand the application of TOBPs to remove toxic organic pollutants.
Topics: Photolysis; Titanium; Environmental Pollutants; Water; Catalysis
PubMed: 37127104
DOI: 10.1016/j.envres.2023.116000 -
Water Research Jul 2024Nitrate photolysis has become an efficient, low-cost and promising technology for emerging contaminants removal, while its performance and mechanism for waste activated...
Insights into the effect of nitrate photolysis on short-chain fatty acids production from waste activated sludge in anaerobic fermentation system: Performance and mechanisms.
Nitrate photolysis has become an efficient, low-cost and promising technology for emerging contaminants removal, while its performance and mechanism for waste activated sludge (WAS) treatment is still unknown. This study innovatively introduced nitrate photolysis for WAS disintegration, and investigated the effect of nitrate addition (150-375 mg N/L) for short-chain fatty acids (SCFAs) production during anaerobic fermentation (AF). The results showed that nitrate photolysis significantly promoted the SCFAs production from WAS, and peaked at 280.7 mg/g VSS with 7-d fermentation with 150 mg N/L addition (150N-UV), which increased by 8.8-35.0 % and 10.7-23.3 % compared with other photolysis groups and sole nitrate groups. Effective release of the soluble organics was observed in the nitrate photolysis groups during AF, especially soluble proteins, reaching 1505.4 mg COD/L at 9 d in 150N-UV group, promoted by 7.0∼15.7 % than nitrate/nitrate photolysis groups. The model compounds simulation experiment further demonstrated the positive effect of nitrate photolysis on organics hydrolysis and SCFAs accumulation. The result of the radical capture and quenching verified the reactive oxygen species contributed more compared with reactive nitrogen species. Functional group analysis confirmed the effective bioconversion of the macromolecular organics during the fermentation. Moreover, the nitrate photolysis enhanced the enrichment of the functional consortia, including anaerobic fermentation bacteria (AFB), e.g., Fnoticella, Romboutsia, Gracilibacter and Sedimentibacter, and nitrate reducing bacteria (NRB), e.g., Acinerobacter and Ahniella. The macrogenetic analysis further revealed that glycolysis, amino acid metabolism, acetate metabolism and nitrogen metabolism were the dominating metabolic pathways during fermentation, and the abundance of the relevant genes were enhanced in 150N-UV group.
Topics: Sewage; Nitrates; Photolysis; Fermentation; Anaerobiosis; Fatty Acids, Volatile; Waste Disposal, Fluid; Bioreactors
PubMed: 38761600
DOI: 10.1016/j.watres.2024.121772 -
Environmental Research Aug 2023Dissolved organic matter (DOM) widely exists in aquatic environment and plays a critical role in environmental photochemical reaction. The photochemical behaviors of DOM... (Review)
Review
Dissolved organic matter (DOM) widely exists in aquatic environment and plays a critical role in environmental photochemical reaction. The photochemical behaviors of DOM in sunlit surface waters have received widely attention because its photochemical effects for some coexisted substances in aquatic environment, especially for organic micropollutants degradation. Therefore, to gain a comprehensive understanding of the photochemical properties and environmental effects of DOM, we reviewed the influence of sources on the structure and composition of DOM with relevant identified techniques to analysis functional groups. Additionally, identification and quantification for reactive intermediates are discussed with a focus on influencing factors to produce reactive intermediates by DOM under solar irradiation. These reactive intermediates can promote the photodegradation of organic micropollutants in the environmental system. In future, attention should be paid to the photochemical properties of DOM and environmental effects in real environmental system and development of advanced techniques to study DOM.
Topics: Dissolved Organic Matter; Photolysis; Solar Energy
PubMed: 37209983
DOI: 10.1016/j.envres.2023.116174 -
Journal of Hazardous Materials Aug 2024Photochemical transformation is an important attenuation process for the non-steroidal anti-inflammatory drug naproxen (NPX) in both engineered and natural waters....
Photochemical transformation is an important attenuation process for the non-steroidal anti-inflammatory drug naproxen (NPX) in both engineered and natural waters. Herein, we investigated the photolysis of NPX in aqueous solution exposed to both ultraviolet (UV, 254 nm) and natural sunlight irradiation. Results show that N purging significantly promoted NPX photolysis under UV irradiation, suggesting the formation of excited triplet state (NPX*) as a critical transient. This inference was supported by benzophenone photosensitization and transient absorption spectra. Sunlight quantum yield of NPX was only one fourteenth of that under UV irradiation, suggesting the wavelength-dependence of NPX photochemistry. NPX* formed upon irradiation of NPX underwent photodecarboxylation leading to the formation of 2-(1-hydroxyethyl)-6-methoxynaphthalene (2HE6MN), 2-(1-hydroperoxyethyl)-6-methoxynaphthalene (2HPE6MN), and 2-acetyl-6-methoxynaphthalene (2A6MN). Notably, the conjugation and spin-orbit coupling effects of carbonyl make 2A6MN a potent triplet sensitizer, therefore promoting the photodegradation of the parent NPX. In hospital wastewater, the photolysis of NPX was influenced because the photoproduct 2A6MN and wastewater components could competitively absorb photons. Bioluminescence inhibition assay demonstrated that photoproducts of NPX exhibited higher toxicity than the parent compound. Results of this study provide new insights into the photochemical behaviors of NPX during UV treatment and in sunlit surface waters.
Topics: Naproxen; Photolysis; Ultraviolet Rays; Sunlight; Water Pollutants, Chemical; Anti-Inflammatory Agents, Non-Steroidal; Benzophenones; Photosensitizing Agents
PubMed: 38852251
DOI: 10.1016/j.jhazmat.2024.134841 -
Environmental Research Sep 2023This study deals with the fabrication of metal ion (M = Co, Ni, and Cu) doped- BiO photocatalysts by solution combustion method. All the synthesized materials were...
Co, Ni and Cu incorporated BiO nano photocatalysts: Synthesis, DFT analysis of band gap modification, adsorption and photodegradation analysis of rhodamine B and Triclopyr.
This study deals with the fabrication of metal ion (M = Co, Ni, and Cu) doped- BiO photocatalysts by solution combustion method. All the synthesized materials were characterized and analysed with the help of XRD, FESEM, EDX, HRTEM, UVDRS, Zeta potential, PL, and LCMS techniques for the structural, morphological, surface charge, optical and degradation pathways characteristics. Synthesized compounds were used for the decontamination (adsorption and degradation) of two organic pollutants namely Rhodamine B and Triclopyr. Adsorption aspects of the pollutants were studied in terms of different isotherm, kinetic and thermodynamic models. Adsorption phenomenon was best fitted with the Freundlich (R = 0.992) and Langmuir isotherm (R = 0.999) models along with pseudo second order model of kinetics for RhB and TC, respectively. Moreover, the thermodynamic parameters indicated exothermic and endothermic adsorption (ΔH ° (-7.19 kJ/mol) for RhB) and (ΔH ° (52.335 kJ/mol) for TC), respectively. Evaluated negative values of ΔG ° indicated spontaneous adsorption with most favourable at 298 K and 318 K for both the pollutants (RhB and TC) respectively. Modification with metal ions significantly improved the removal efficiency of pure BiO photocatalyst and followed the trend Co/BiO > Ni/BiO > Cu/BiO > BiO. DFT calculations demonstrate that amongst the doped materials, only Co/BiO is characterized by an indirect band gap; which exhibited efficacious photocatalytic activity. Besides, the highest degradation efficiency was obtained in the case of Co/BiO (2 mol %); being 99.80% for RhB in 30 min and 98.50% for TC in 60 min, respectively. The doped nanostructures lead to higher absorption of visible light and more separation of light-induced charged carriers. Effect of pH of the reaction medium and role of reactive oxygen species was also examined. Finally, a probable mechanism of charge transfer and degradation of the pollutants was also presented.
Topics: Adsorption; Photolysis; Thermodynamics; Water Pollutants, Chemical
PubMed: 37348633
DOI: 10.1016/j.envres.2023.116478 -
Frontiers in Chemistry 2023Nitroguaiacols are typical constituents of biomass-burning emissions, including absorbing aerosols which contribute to climate change. Although they are also harmful to...
Nitroguaiacols are typical constituents of biomass-burning emissions, including absorbing aerosols which contribute to climate change. Although they are also harmful to humans and plants, their atmospheric fate and lifetimes are still very speculative. Therefore, in this work, the photolysis kinetics of aqueous-phase 4-nitroguaiacol (4NG) and 5-nitroguaiacol (5NG), and the resulting photo-formed products were investigated under artificial sunlight, observing also the effect of sunlight on the absorption properties of the solutions. We found the photolysis of 5NG slower than that of 4NG, whereas the absorbance in the visible range prevailed in the 5NG solutions at the end of experiments. Although we identified dinitroguaiacol as one of the 4NG photolysis products, which increased light absorption of 4NG-containing solutions, considerably more chromophores formed in the 5NG photolyzed solutions, implying its stronger potential for secondary BrC formation in the atmosphere. In general, denitration, carbon loss, hydroxylation, nitration, and carbon gain were characteristic of 4NG phototransformation, while carbon loss, hydroxylation, and carbon gain were observed in the case of 5NG. The photolysis kinetics was found of the first order at low precursor concentrations (<0.45 mM), resulting in their lifetimes in the order of days (125 and 167 h illumination for 4NG and 5NG, respectively), which suggests long-range transport of the investigated compounds in the atmosphere and proposes their use as biomass-burning aerosol tracer compounds.
PubMed: 37521016
DOI: 10.3389/fchem.2023.1211061