-
Scientific Reports Jun 2024A composite of Zinc oxide loaded with 5-weight % silver decorated on carbon nanotubes (Ag-loaded ZnO: CNT) was synthesized using a simple refluxed chemical method. The...
A composite of Zinc oxide loaded with 5-weight % silver decorated on carbon nanotubes (Ag-loaded ZnO: CNT) was synthesized using a simple refluxed chemical method. The influence of deviation in the weight % of carbon nanotube loading on photocatalytic dye degradation (methylene blue and rose bengal) and antibiotic (antimicrobial and antifungal) performance was investigated in this study. The light capture ability of Ag-loaded ZnO:CNT in the visible region was higher in photocatalytic activity than that of Ag-loaded ZnO and ZnO:CNT. The bandgap of the Ag-loaded ZnO: CNT was tuned owing to the surface plasmon resonance effect. The photocatalytic degradation investigations were optimized by varying the wt% in CNTs, pH of dye solution, concentration of the dye solution, and amount of catalytic dose. Around 100% photocatalytic efficiency in 2 min against MB dye was observed for Ag doped ZnO with 10 wt% CNT composite at pH 9, at a rate constant 1.48 min. Bipolaris sorokiniana fungus was first time tested against a composite material, which demonstrated optimum fungal inhibition efficiency of 48%. They were also tested against the bacterial strains Staphylococcus aureus, Bacillus cerius, Proteus vulgaris, and Salmonella typhimurium, which showed promising antibacterial activity compared to commercially available drugs. The composite of Ag doped ZnO with 5 wt% CNT has shown competitive zone inhibition efficacy of 21.66 ± 0.57, 15.66 ± 0.57, 13.66 ± 0.57 against bacterial strains Bacillus cerius, Proteus vulgaris, and Salmonella typhimurium which were tested for the first time against Ag-loaded ZnO:CNT.
Topics: Zinc Oxide; Silver; Nanotubes, Carbon; Anti-Bacterial Agents; Catalysis; Antifungal Agents; Staphylococcus aureus; Methylene Blue; Coloring Agents; Rose Bengal; Microbial Sensitivity Tests; Salmonella typhimurium; Hydrogen-Ion Concentration; Photolysis; Photochemical Processes
PubMed: 38890495
DOI: 10.1038/s41598-024-64746-6 -
Journal of Hazardous Materials Aug 2024Urea abatement has been a prominent challenge for UPW production. This research proposed a productive strategy combining pre-chlorination and VUV/UV processes under...
Urea abatement has been a prominent challenge for UPW production. This research proposed a productive strategy combining pre-chlorination and VUV/UV processes under acidic conditions to settle this problem. This study first revealed the reaction kinetics between urea and free chlorine in a large pH range from 2.5 to 9.6, where the reaction constant rate varied from 0.06 to 0.46 M·s. Substitution reaction mediated by Cl was the dominant process at low pH (pH<3). The differences of dominant pathways resulted in the differences in reaction products: The detected concentration of dichloramine at pH 2.5 was twice that at pH 4.5 and 6.5. Further, this study found that pre-chlorination/VUV/UV process could achieve the thorough removal of 2-mg/L urea with chlorination of less than 5 min and VUV/UV irradiation of less than 200 mJ/cm. Chloride ions, low pH, and higher chlorine dosage were found to be the positive factors to improve urea removal efficiency in pre-chlorination/VUV/UV process. The reaction rate constants between chlorourea with·OH and·Cl were calculated to be 3.62 × 10 and 2.26 × 10 L·mol·s, respectively.·Cl,·OH and photolysis contributed 60.5 %, 22.9 % and 16.6 % in chlorourea degradation, respectively. Pre-chlorination/VUV/UV achieved a DOC removal efficiency of 78.5 %. And nitrogen in urea was converted into inorganic nitrogenous compounds. Finally, compared with direct VUV/UV/chlorine and VUV/UV/persulfate processes, this process saved more than 70 % of energy in VUV/UV unit.
PubMed: 38889471
DOI: 10.1016/j.jhazmat.2024.134836 -
Journal of Hazardous Materials Aug 2024Organophosphate esters (OPEs) are widely used commercial additives, but their environmental persistence and toxicity raise serious concerns necessitating associated... (Review)
Review
Organophosphate esters (OPEs) are widely used commercial additives, but their environmental persistence and toxicity raise serious concerns necessitating associated remediation strategies. Although there are various existing technologies for OPE removal, comprehensive screening for them is urgently needed to guide further research. This review provides a comprehensive overview of the techniques used to remove OPEs from soil and water, including their related influencing factors, removal mechanisms/degradation pathways, and practical applications. Based on an analysis of the latest literature, we concluded that (1) methods used to decontaminate OPEs include adsorption, hydrolysis, photolysis, advanced oxidation processes (AOPs), activated sludge processes, and microbial degradation; (2) factors such as the quantity/characteristics of the catalysts/additives, pH value, inorganic ion concentration, and natural organic matter (NOM) affect OPE removal; (3) primary degradation mechanisms involve oxidation induced by reactive oxygen species (ROS) (including •OH and SO•) and degradation pathways include hydrolysis, hydroxylation, oxidation, dechlorination, and dealkylation; (5) interference from the pH value, inorganic ion and the presence of NOM may limit complete mineralization during the treatment, impacting practical application of OPE removal techniques. This review provides guidance on existing and potential OPE removal methods, providing a theoretical basis and innovative ideas for developing more efficient and environmentally friendly techniques to treat OPEs in soil and water.
Topics: Esters; Soil Pollutants; Water Pollutants, Chemical; Environmental Restoration and Remediation; Organophosphates; Water Purification
PubMed: 38889460
DOI: 10.1016/j.jhazmat.2024.134834 -
Beilstein Journal of Organic Chemistry 2024Organic photocatalysts frequently possess dual singlet and triplet photoreactivity and a thorough photochemical characterization is essential for efficient light-driven...
Organic photocatalysts frequently possess dual singlet and triplet photoreactivity and a thorough photochemical characterization is essential for efficient light-driven applications. In this article, the mode of action of a polyazahelicene catalyst (Aza-H) was investigated using laser flash photolysis (LFP). The study revealed that the chromophore can function as a singlet-state photoredox catalyst in the sulfonylation/arylation of styrenes and as a triplet sensitizer in energy transfer catalysis. The singlet lifetime is sufficiently long to exploit the exceptional excited state reduction potential for the activation of 4-cyanopyridine. Photoinduced electron transfer generating the radical cation was directly observed confirming the previously proposed mechanism of a three-component reaction. Several steps of the photoredox cycle were investigated separately, providing deep insights into the complex mechanism. The triplet-excited Aza-H, which was studied with quantitative LFP, is formed with a quantum yield of 0.34. The pronounced triplet formation was exploited for the isomerization reaction of ()-stilbene to the -isomer and the cyclization of cinnamyl chloride. Catalyst degradation mainly occurs through the long-lived Aza-H triplet (28 µs), but the photostability is greatly increased when the triplet efficiently reacts in a catalytic cycle such that turnover numbers exceeding 4400 are achievable with this organocatalyst.
PubMed: 38887585
DOI: 10.3762/bjoc.20.106 -
The Journal of Physical Chemistry. A Jun 2024Methyl esters are an important component of combustion and atmospheric systems. Reaction with the OH radical plays an important role in the removal of the simplest...
Methyl esters are an important component of combustion and atmospheric systems. Reaction with the OH radical plays an important role in the removal of the simplest methyl ester, methyl formate (MF, CHOCHO). In this paper, the overall rate coefficients for the reactions of OH and OD with MF isotopologues, studied under pseudo-first-order conditions, are reported using two different laser flash photolysis systems with the decay of OH monitored by laser-induced fluorescence. The room-temperature rate coefficient for OH + MF, (1.95 ± 0.34) × 10 cm molecule s, is in good agreement with the literature. The rate coefficient exhibits curved Arrhenius behavior, and our results bridge the gap between previous low-temperature and shock tube studies. In combination with the literature, the rate coefficient for the reaction of OH with MF between 230 and 1400 K can be parametrized as = (3.2 × 10) × (T/300 K) × exp(-141.4 K/) cm molecule s with an overall estimated uncertainty of ∼30%. The reactions of OD with MF isotopologues show a small enhancement (inverse secondary isotope effect) compared to the respective OH reactions. The reaction of OH/OD with MF shows a normal primary isotope effect, a decrease in the rate coefficient when MF is partially or fully deuterated. Experimental studies have been supported by calculations at the CCSD(T)-F12/aug-cc-pVTZ//M06-2/6-31+G** level of theory. The calculated, zero-point-corrected, barrier heights for abstraction at the methyl and formate sites are 1.3 and 6.0 kJ mol, respectively, and the predictions of kinetic isotope effects are in agreement with experiment. Fitting the experimental isotopologue data refines these barriers to 0.9 ± 0.6 and 4.1 ± 0.9 kJ mol. The branching ratio is approximately 50:50 at 300 K. Between 300 and 500 K, abstraction via the higher-energy, higher-entropy formate transition state becomes more favored (60:40). However, experiment and calculations suggest that as the temperature increases further, with higher energy, less constrained conformers of the methyl transition state become more significant. The implications of the experimental and theoretical results for the mechanisms of MF atmospheric oxidation and low-temperature combustion are discussed.
PubMed: 38885649
DOI: 10.1021/acs.jpca.4c02524 -
Environmental Science & Technology Jul 2024Understanding of nitrous acid (HONO) production is crucial to photochemical studies, especially in polluted environments like eastern China. In-situ measurements of...
Understanding of nitrous acid (HONO) production is crucial to photochemical studies, especially in polluted environments like eastern China. In-situ measurements of gaseous and particulate compositions were conducted at a rural coastal site during the 2018 spring Ozone Photochemistry and Export from China Experiment (OPECE). This data set was applied to investigate the recycling of reactive nitrogen through daytime heterogeneous HONO production. Although HONO levels increase during agricultural burning, analysis of the observation data does not indicate more efficient HONO production by agricultural burning aerosols than other anthropogenic aerosols. Box and 1-D modeling analyses reveal the intrinsic relationships between nitrogen dioxide (NO), particulate nitrate (pNO), and nitric acid (HNO), resulting in comparable agreement between observed and simulated HONO concentrations with any one of the three heterogeneous HONO production mechanisms, photosensitized NO conversion on aerosols, photolysis of pNO, and conversion from HNO. This finding underscores the uncertainties in the mechanistic understanding and quantitative parametrizations of daytime heterogeneous HONO production pathways. Furthermore, the implications for reactive nitrogen recycling, ozone (O) production, and O control strategies vary greatly depending on the HONO production mechanism. On a regional scale, the conversion of HONO from pNO can drastically enhance O production, while the conversion from NO can reduce O sensitivity to NOx changes in polluted eastern China.
Topics: Ozone; Nitrous Acid; China; Nitrogen; Air Pollutants; Aerosols; Nitrogen Dioxide
PubMed: 38885439
DOI: 10.1021/acs.est.3c07967 -
Environmental Monitoring and Assessment Jun 2024In the current work, Response Surface Methodology (RSM)-a statistical method-is used to optimize procedures like photocatalysis with the least amount of laboratory...
In the current work, Response Surface Methodology (RSM)-a statistical method-is used to optimize procedures like photocatalysis with the least amount of laboratory testing. However, to determine the most effective model for achieving the maximum rate of removal efficiency, the Response Surface Methodology was employed. The Ba-doped BiFeO photocatalyst was synthesized by the co-precipitation method, and its intrinsic properties were investigated by utilizing a range of spectroscopic techniques, such as FESEM, EDX, XRD, FTIR, and UV-vis. Herein, four independent factors such as, pH, contact time, pollutant concentration, and catalyst dosage were chosen. The results revealed that under acidic conditions with a contact duration of 2 min, a moderate catalyst dosage, and higher pollutant concentration, a degradation rate of 89.8% was achieved. The regression coefficient (R) and probability value (P) were determined to be 0.99551 and 0.0301, respectively, therefore confirming the excellent fit of the RSM model. Furthermore, this research investigated the potential photocatalytic degradation mechanisms of cefixime, demonstrating that the removal efficiency of cefixime is greatly influenced by the functional parameters.
Topics: Catalysis; Nanostructures; Water Pollutants, Chemical; Cefixime; Bismuth; Photolysis; Photochemical Processes; Ferric Compounds
PubMed: 38884667
DOI: 10.1007/s10661-024-12781-1 -
Journal of Molecular Biology Jun 2024Heliorhodopsin (HeR) is a new rhodopsin family discovered in 2018 through functional metagenomic analysis. Similar to microbial rhodopsins, HeR has an all-trans retinal...
Heliorhodopsin (HeR) is a new rhodopsin family discovered in 2018 through functional metagenomic analysis. Similar to microbial rhodopsins, HeR has an all-trans retinal chromophore, and its photoisomerization to the 13-cis form triggers a relatively slow photocycle with sequential intermediate states (K, M, and O intermediates). The O intermediate has a relatively long lifetime and is a putative active state for transferring signals or regulating enzymatic reactions. Although the first discovered HeR, 48C12, was found in bacteria and the second HeR (TaHeR) was found in archaea, their key amino acid residues and molecular architectures have been recognized to be well conserved. Nevertheless, the rise and decay kinetics of the O intermediate are faster in 48C12 than in TaHeR. Here, using a new infrared spectroscopic technique with quantum cascade lasers, we clarified that the hydrogen bond between transmembrane helices (TM) 3 and 4 is essential for the altered O kinetics (Ser112 and Asn138 in 48C12). Interconverting mutants of 48C12 and TaHeR clearly revealed that the hydrogen bond is important for regulating the dynamics of the O intermediate. Overall, our study sheds light on the importance of the hydrogen bond between TM3 and TM4 in heliorhodopsins, similar to the DC gate in channelrhodopsins.
PubMed: 38880378
DOI: 10.1016/j.jmb.2024.168666 -
Environmental Pollution (Barking, Essex... Jun 2024Water pollution caused by antibiotics and synthetic dyes and imminent energy crises due to limited fossil fuel resources are issues of contemporary decades. Herein, we...
Water pollution caused by antibiotics and synthetic dyes and imminent energy crises due to limited fossil fuel resources are issues of contemporary decades. Herein, we address them by enabling the multifunctionality in dual Z-scheme MoS/WO/AgBiS across photolysis, photo Fenton-like, and night catalysis. Defect, basal, and facet-engineered WO is modified with MoS and AgBiS, which extended its photoresponse from the UV-NIR region, inhibited carrier recombination, and reduced carrier transfer resistance. The electric field rearrangement leads to a flow of electrons from MoS and AgBiS to WO and intensifies the electron population, which is crucial for night catalysis. When MoS/WO/AgBiS was employed against doxycycline hydrochloride (DOXH), it removed 95.65, 81.11, and 77.92 % of DOXH in 100 min during photo-Fenton (PFR), night-Fenton (NFR), and photocatalytic (PCR) reactions, respectively. It also effectively removed 91.91, 98.17, 99.01, and 98.99 % of rhodamine B (RhB), Congo red (CR), methylene blue (MB), and methylene orange (MO) in Fenton reactions, respectively. ESR analysis consolidates the ROS generation feature of MoS/WO/AgBiS using HO with and without irradiation. This work provides a strategy to eliminate the deficiencies of WO and is conducive to the evolution of applications seeking to combat environmental and energy crises.
PubMed: 38880327
DOI: 10.1016/j.envpol.2024.124375 -
The Science of the Total Environment Jun 2024Tioxazafen (TXF) is the first 1,2,4-oxadiazole nematicide. In the present study, the aqueous degradation of TXF was investigated in terms of hydrolysis and photolysis....
Tioxazafen (TXF) is the first 1,2,4-oxadiazole nematicide. In the present study, the aqueous degradation of TXF was investigated in terms of hydrolysis and photolysis. Under the irradiation of simulated sunlight, TXF degraded very fast in ultrapure water and buffers with half-lives (ts) <8.3 min. A sole photoproduct (PP) PP228a was isolated, and identified by spectroscopic means (UV, IR, HRMS, and H NMR) to be the thiophen-3-yl isomer converted from its thiophen-2-yl parent. Comparing with TXF, PP228a had quite extended ts ranging from 6.9 to 7.9 d. The photolysis kinetics of TXF and PP228a showed no pH-dependence, and varied for each individual compound as affected by nitrate, fulvic acid, and humic acid. Besides, both compounds were hydrolytically stable. 6 PPs of PP228a were identified, with two of them being its isomers. The mechanisms involved in the process included the biradical photosensitization, photoinduced electron transfer, and ring contraction-ring expansion reactions. The 48 h-EC to Daphnia magna was 0.808 mg/L for PP228a comparing to >1.12 mg/L for TXF, while the results of Vibrio fischeri assays indicated that one or more PPs of PP228a might have higher toxicity.
PubMed: 38880139
DOI: 10.1016/j.scitotenv.2024.173817