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1.
Water Res ; 168: 115169, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31629231

RESUMO

Nitrite formation during Vacuum UV (VUV) photolysis of nitrate-containing water has been studied in this research. Here the goal was to understand the effect of water matrix, specifically dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and dissolved oxygen (DO), on the formation of nitrite in nitrate-containing water during treatment with VUV AOP. The results confirmed that the formation of nitrite was considerable during the VUV irradiation, and it increased with increasing the UV fluence. However, the rate of nitrite formation was not linearly correlated with the UV fluence. Also, nitrite formation increased with increasing the DOC in water. Tert-butanol, as OH radical scavenger, was used to elucidate the mechanism behind the impact of DOC. The effect of DIC was only pronounced at very high DIC concentration, which led to lower formation of nitrite. When both DOC and DIC were present in water, DOC had the dominant effect on nitrite formation. DO in water had the impact of reducing the formation of nitrite. All these results can help to understand the mechanisms involved in the transformation of nitrate to nitrite in various water matrices, and guide VUV applications for scientific and industrial proposes.


Assuntos
Nitritos , Água , Carbono , Fotólise , Raios Ultravioleta , Vácuo
2.
J Environ Sci (China) ; 85: 129-137, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31471019

RESUMO

Benzotriazole UV stabilizers (BT-UVs) have attracted concerns due to their ubiquitous occurrence in the aquatic environment, and their bioaccumulative and toxic properties. However, little is known about their aquatic environmental degradation behavior. In this study, photodegradation of a representative of BT-UVs, 2-(2-hydroxy-5-methylphenyl)benzotriazole (UV-P), was investigated under simulated sunlight irradiation. Results show that UV-P photodegrades slower under neutral conditions (neutral form) than under acidic or alkaline conditions (cationic and anionic forms). Indirect photodegradation is a dominant elimination pathway of UV-P in coastal seawaters. Dissolved organic matter (DOM) from seawaters accelerate the photodegradation rates mainly through excited triplet DOM (3DOM⁎), and the roles of singlet oxygen and hydroxyl radical are negligible in the matrixes. DOM from seawaters impacted by mariculture exhibits higher steady-state concentration of 3DOM⁎ ([3DOM⁎]) relative to those from pristine seawaters, leading to higher photosensitizing effects on the photodegradation. Halide ions inhibit the DOM-sensitized photodegradation of UV-P by decreasing [3DOM⁎]. Photodegradation half-lives of UV-P are estimated to range from 24.38 to 49.66 hr in field water bodies of the Yellow River estuary. These results are of importance for assessing environmental fate and risk UV-P in coastal water bodies.


Assuntos
Protetores Solares/química , Triazóis/química , Poluentes Químicos da Água/química , Fotólise , Água do Mar
3.
J Environ Manage ; 250: 109486, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31518793

RESUMO

Energy and water are the two major issues facing the modern mankind. Providing freshwater requires energy and producing energy uses water. In the present-day scenario, both these routes face growing problems and limitations. Energy crisis has risen due to the depletion of fossil fuels that cause pollution to water bodies making the water unusable for human consumption. In this regard, semiconductor nanocrystals with luminescent properties or carbon quantum dots (CQDs) are the newly developed nanomaterials whose distinctive photo-physical characteristics are focusing to a new generation of robust materials and sensors for sustainable development. In this review, advances in surface and band gap modification of CQDs to improve the activity of nanomaterials will be discussed with special reference to some specific CQDs exhibiting special optical properties for water treatment/splitting applications. Recent advances on CQDs nanocomposites including their applications in photodegradation of organic pollutants, sensing of heavy metal ions in water and water splitting are discussed critically to narrate the future prospects in this field. Challenges and limitations for further improvement are covered to provide smart choices for creating sustainability of benign environment and economic benefits.


Assuntos
Recuperação e Remediação Ambiental , Pontos Quânticos , Carbono , Humanos , Hidrogênio , Fotólise
4.
Inorg Chem ; 58(18): 12302-12310, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31522510

RESUMO

Photochemistry is a rich source of inspiration for developing alternative methods to functionalize proteins with drug molecules, fluorophores, and radioactive probes. Here, we report the synthesis and photochemical reactivity of a modified diethylenediamine pentaacetic acid chelate that was derivatized with a light-responsive aryl azide group (DTPA-PEG3-ArN3, compound 1). The corresponding nonradioactive and radioactive nat/68Ga3+ and nat/111In3+ complexes of DTPA-PEG3-ArN3 were synthesized and their physical and photochemical properties were studied to evaluate the potential of employing this ligand system in the photochemical synthesis of radiolabeled antibodies. Photodegradation kinetics revealed that irradiation with ultraviolet light (365 nm) induced rapid photoactivation of compound 1 and the metal complexes nat/68Ga-1- and nat/111In-1-. Light-induced reactions were complete in <100 s, with measured first-order rate constants of 0.078 ± 0.045 s-1, 0.093 ± 0.009 s-1, and 0.117 ± 0.054 s-1 (n = 2, per species) for compound 1, natGa-1-, and natIn-1-, respectively. Photochemically induced bioconjugation reactions between DTPA-PEG3-ArN3 and the monoclonal antibody trastuzumab, as well as pre- and postconjugation 68Ga- and 111In-radiolabeling experiments, were performed using either a one-pot or two-step strategy. Both approaches yielded radiolabeled trastuzumab ([68Ga]GaDTPA-azepin-trastuzumab) with average radiochemical conversions of 3.9 ± 1.0% (n = 4, one-pot), and 10.0 ± 1.0% (n = 3, two-step). One-pot radiolabeling reactions with [111In]InCl3 produced the corresponding [111In]InDTPA-azepin-trastuzumab radiotracer in a similar radiochemical conversion of 5.4 ± 0.8% (n = 3). Radiochemical conversions for the desired bimolecular coupling between the chelate and the protein were comparatively low. This observation is likely caused by the high photoinduced reactivity of the compounds and subsequent competition with background reactions. Nevertheless, access to DTPA-PEG3-ArN3 increases the scope of photoradiochemical methods to include metal ions like In3+ that form complexes with higher coordination numbers.


Assuntos
Quelantes/química , Radioisótopos de Gálio/química , Imunoconjugados/química , Radioisótopos de Índio/química , Ácido Pentético/química , Polietilenoglicóis/química , Trastuzumab/química , Argônio/química , Quelantes/síntese química , Luz , Ácido Pentético/síntese química , Fotólise , Polietilenoglicóis/síntese química
5.
Chemosphere ; 235: 1041-1049, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561293

RESUMO

Magnetic carbon nanotube (MCNT) composites with titanium dioxide (TiO2) have an enhanced photocatalytic disinfection efficiency (i.e. higher disinfection rate) and better applicability (i.e. solar light applicability and catalyst separation using its magnetic property) than bare TiO2 and/or MCNT. However, the role and mechanism of MCNT in the disinfection process are still unclear. Therefore, this study aimed at investigating the disinfection mechanism of Escherichia coli using MCNT-TiO2 nanocomposites under various conditions (i.e. the presence and absence of light and reactive oxygen species scavengers, and different MCNT-TiO2 ratio) and photocatalytic disinfection models. The results showed that (i) MCNT and its nanocomposites with TiO2 had much higher disinfection efficiencies than bare TiO2, (ii) the physical bacterial capture was the dominant disinfection mechanism, (iii) the higher disinfection rate was found at an optimum MCNT:TiO2 ratio of 5:1 under the tested experimental conditions, (iv) hydroxyl radical (OH) was the influencing reactive oxygen species on the photocatalytic disinfection using MCNT-TiO2, and (v) good correlation between experimental parameters (i.e. carbon contents, surface area and concentration of MCNT-TiO2) and the contribution rate of physical and photocatalysis reactions. The finding from this study and the methods proposed herein are essential for understanding the photocatalytic disinfection processes using TiO2 and its carbonaceous nanocomposites, which can promote the application of photocatalytic disinfection process.


Assuntos
Desinfecção/métodos , Escherichia coli/efeitos dos fármacos , Nanocompostos/química , Nanotubos de Carbono , Titânio , Catálise , Magnetismo , Nanocompostos/toxicidade , Fotólise/efeitos dos fármacos
6.
Chemosphere ; 235: 1116-1124, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561302

RESUMO

The porous graphitic carbon nitride nanosheets (PCNSs) with high yields were synthesized by using one-step chemical exfoliation method. PCNSs accelerated separation efficiency of photo-generated electron-hole pairs in comparison to bulk graphitic carbon nitride. The PCNS5 (exfoliation for 5 h) exhibited optimal photocatalytic disinfection capability towards Escherichia coli K-12 under simulated solar light irradiation with complete disinfection of 6.5 log10 cfu/mL of E. coil K-12 within 2 h. The enhanced photocatalytic activity of PCNS5 originated from mesoporous nanosheet structure. The possible mechanism of photocatalytic disinfection has proposed that intracellular reactive oxygen species levels and the activities of antioxidant enzymes (e.g., catalase and superoxide dismutase) were enhanced. Transmission electron microscope images observed during photocatalytic disinfection process suggested that the cell membrane was regarded as the first target for oxidation, resulting in a faster leakage of cytoplasmic content and finally degradation of DNA leading to bacterial death. Furthermore, the trapping experiment showed that superoxide radical (•O2-) and holes (h+) were responsible for E. coli K-12 disinfection by PCNS5.


Assuntos
Desinfecção/métodos , Escherichia coli K12/efeitos dos fármacos , Nanoestruturas/química , Nitrilos/toxicidade , Fotólise , Bactérias/efeitos dos fármacos , Membrana Celular/metabolismo , Dano ao DNA , Oxirredução , Porosidade , Espécies Reativas de Oxigênio
7.
Phys Chem Chem Phys ; 21(37): 20628-20640, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31495862

RESUMO

Methionine synthase (MetH) is a methylcobalamin (MeCbl)-dependent mammalian enzyme which plays a critical role in carrying out the transfer of a methyl group from methyl tetrahydrofolate to homocysteine to generate methionine and tetrahydrofolate. This catalytic cycle proceeds via cleavage of a Co-C bond which is formally heterolytic. This cleavage results in a structural change in the MeCbl cofactor bound to an enzyme. Unlike the native catalysis, upon photoexcitation, the Co-C bond in MeCbl-bound MetH generates the Co(ii)/CH3 radical pairs (RPs). Protein residues of the cap domain, particularly phenylalanine708 (F708) and leucine 715 (L715), which surrounds the upper face of the MeCbl cofactor, inhibit the photolysis of MeCbl by caging the CH3 radical and inducing the geminate recombination of the Co(ii)/CH3 RP. A molecular-level understanding of these effects requires a detailed investigation of the low-lying electronic states. Toward this, we have mutated the F708 residue with alanine (A708) and constructed the potential energy surfaces (PESs) for the low-lying S1 electronic state using a combined quantum mechanics/molecular mechanics (QM/MM) approach. The S1 PESs for the wild-type (WT) and mutant enzymes are the result of crossing of two electronic states, namely metal-to-ligand charge transfer (MLCT) and ligand field (LF) states, indicated by a seam. It is shown that the topologies of the S1 PESs are significantly modulated by introducing a mutation at the F708 position. Specifically, for the WT enzyme, the energy barrier of photoreaction and the energy difference between MLCT and LF minima are markedly higher than those of its mutant counterpart. Moreover, mutation influences the photoactivation of the Co-C bond in enzyme-bound MeCbl by decreasing the rate of geminate recombination and altering the rate of radical pair formation. This theoretical insight was also compared with transient absorption spectroscopic (TAS) studies which are in good agreement with the present findings.


Assuntos
5-Metiltetra-Hidrofolato-Homocisteína S-Metiltransferase/genética , Carbono/química , Cobalto/química , Vitamina B 12/análogos & derivados , 5-Metiltetra-Hidrofolato-Homocisteína S-Metiltransferase/metabolismo , Modelos Químicos , Estrutura Molecular , Mutação/genética , Fotólise , Domínios Proteicos/genética , Vitamina B 12/metabolismo
8.
J Agric Food Chem ; 67(35): 9926-9933, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31398027

RESUMO

Vitamins and flavonoids are two kinds of essential trace bioactives which are prone to photodegradation during food processing and storage. In this study, a particle-stabilized water-in-water (W/W) emulsion system composed of soy protein isolate (SPI) and guar gum (GG) was applied in loading riboflavin. Based on the significant binding affinity differences of SPI (Ka = 1.11 × 105 L mol-1) and GG (Ka = 9.00 × 103 L mol-1) to riboflavin, this hydrophilic and light-sensitive bioactive compound was loaded in SPI-rich droplets. Confocal images indicated that a stable microstructure of SPI-rich droplets suspended in GG-rich continuous phase was successfully constructed by manipulating the proportion of the two polymeric components and using zein-based particles (ZPs) as stabilizers. These negatively charged particles modified by pectin with a hydrodynamic diameter of 533 ± 5.7 nm were able to adsorb at the SPI/GG interface and subsequently stabilized the SPI-in-GG emulsion. Fluorescence spectra of riboflavin suggested that the formation of such W/W emulsion could effectively delay the photodegradation of riboflavin during an 8 h ultraviolet irradiation, and its color was maintained to a maximum extent. Therefore, this structured W/W emulsion could be a desired architecture for delivering light-sensitive cargo.


Assuntos
Riboflavina/química , Água/química , Zeína/química , Composição de Medicamentos , Emulsões/química , Excipientes/química , Galactanos/química , Interações Hidrofóbicas e Hidrofílicas , Cinética , Mananas/química , Tamanho da Partícula , Fotólise , Gomas Vegetais/química
9.
Bioresour Technol ; 289: 121762, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31311731

RESUMO

In this work, glucose addition (0.7 g l-1) almost doubled hydrogen yield of Chlorella pyrenoidosa (121.1 ml l-1 vs 65.5 ml l-1), with a positive correlation between hydrogen production and glucose consumption (-0.977, P < 0.01). When the electrons transport from water photolysis to algal hydrogenase was inhibited, the hydrogen productivity declined by 21.1%; whereas it dramatically decreased by 70.9% when the algal nicotinamide adeninedinucleotide dehydrogenase (NADH) was inhibited. Therefore, in the presence of glucose, the electrons for algae based hydrogen production would be mainly from glucose glycolysis rather than water photolysis. Further deuterated-glucose trial indicated that the glucose might serve as an electron donor for algal hydrogenases. Finally, a tentative electron transport route from glucose to algal hydrogenase was proposed, hoping to provide more scientific direction for further algae-based hydrogen production improvement.


Assuntos
Chlorella/metabolismo , Hidrogênio/metabolismo , Hidrogenase/metabolismo , Transporte de Elétrons , Elétrons , Glucose/metabolismo , Fotólise
10.
Adv Mater ; 31(33): e1902462, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31265196

RESUMO

The controlled presentation of proteins from and within materials remains of significant interest for many bioengineering applications. Though "smart" platforms offer control over protein release in response to a single external cue, no strategy has been developed to trigger delivery in response to user-specified combinations of environmental inputs, nor to independently control the release of multiple species from a homogenous material. Here, a modular semisynthetic scheme is introduced to govern the release of site-specifically modified proteins from hydrogels following Boolean logic. A sortase-mediated transpeptidation reaction is used to generate recombinant proteins C-terminally tethered to gels through environmentally sensitive degradable linkers. By varying the connectivity of multiple stimuli-labile moieties within these customizable linkers, YES/OR/AND control of protein release is exhaustively demonstrated in response to one and two-input combinations involving enzyme, reductant, and light. Tethering of multiple proteins each through a different stimuli-sensitive linker permits their independent and sequential release from a common material. It is expected that these methodologies will enable new opportunities in tissue engineering and therapeutic delivery.


Assuntos
Aminoaciltransferases/química , Proteínas de Bactérias/química , Materiais Biocompatíveis/química , Cisteína Endopeptidases/química , Sistemas de Liberação de Medicamentos/métodos , Hidrogéis/química , Proteínas Recombinantes/química , Aminoaciltransferases/administração & dosagem , Proteínas de Bactérias/administração & dosagem , Cisteína Endopeptidases/administração & dosagem , Dissulfetos/química , Liberação Controlada de Fármacos , Humanos , Luz , Oxirredução , Peptídeos/química , Fotólise , Polietilenoglicóis/química , Proteínas Recombinantes/administração & dosagem , Staphylococcus aureus/enzimologia
11.
J Environ Sci (China) ; 84: 1-12, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31284901

RESUMO

A series of functional organic-metal AgCl-decorated graphitic carbon nitride (AgCl-CNx) composites were synthesized and applied for the degradation of oxalic acid (OA) under visible light. The highest photocatalytic activity was achieved with AgCl decoration ratio of 1.0 (denoted as AgCl-CN1.0). The pseudo-first-order constant for OA degradation was 0.0722 min-1 with the mineralization efficiency of 90.80% after 60 min reaction in the photocatalytic process with AgCl-CN1.0. A variety of characterization techniques including Brunauer-Emmett-Teller, X-ray diffraction, scanning electron microscope, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectra, ultraviolet-visible diffuse reflectance spectra, photoluminescence, and Mott-Schottky were utilized to elucidate the physicochemical, microstructure, and optical properties contributing to the improvement of the photocatalytic performance. The results showed that AgCl-CN1.0 had an oblate flaky erythrocyte-like structure with a moderate band gap energy of ~3.00 eV. In addition, the effects of the key parameters (i.e., AgCl-CN1.0 dosage, initial OA concentration, solution pH, and presence of natural organic matter) on OA degradation were systematically investigated. Radical scavenger experiments indicated that photogenerated holes, electrons, superoxide anion radicals, and hydroxyl radicals were the dominant reactive species. Moreover, AgCl-CN1.0 exhibited excellent stability and reusability for OA degradation without detectable Ag+ release in the solution over multiple reaction cycles. The efficient OA mineralization could be mainly ascribed to the moderate specific surface area, increased numbers of active sites, and effective interfacial charge transfer of AgCl-CN1.0. Overall, the AgCl-CN1.0 composite was demonstrated to be a highly efficient, stable, and recoverable photocatalyst.


Assuntos
Grafite/química , Compostos de Nitrogênio/química , Ácido Oxálico/química , Fotólise , Compostos de Prata/química , Poluentes Químicos da Água/química
12.
J Environ Sci (China) ; 84: 69-79, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31284918

RESUMO

There is an urgent need for developing cost-effective methods for the treatment of perfluorooctanoic acid (PFOA) due to its global emergence and potential risks. In this study, taking surface-defective BiOCl as an example, a strategy of surface oxygen vacancy modulation was used to promote the photocatalytic defluorination efficiency of PFOA under simulated sunlight irradiation. The defective BiOCl was fabricated by a fast microwave solvothermal method, which was found to induce more surface oxygen vacancies than conventional solvothermal and precipitation methods. As a result, the as-prepared BiOCl showed significantly enhanced defluorination efficiency, which was 2.7 and 33.8 times higher than that of BiOCl fabricated by conventional solvothermal and precipitation methods, respectively. Mechanistic studies indicated that the defluorination of PFOA follows a direct hole (h+) oxidation pathway with the aid of •OH, while the oxygen vacancies not only promote charge separation but also facilitate the intimate contact between the photocatalyst surface and PFOA by coordinating with its terminal carboxylate group in a bidentate or bridging mode. This work will provide a general strategy of oxygen vacancy modulation by microwave-assisted methods for efficient photocatalytic defluorination of PFOA in the environment using sunlight as the energy source.


Assuntos
Bismuto/química , Caprilatos/química , Flúor/isolamento & purificação , Fluorcarbonetos/química , Fotólise , Poluentes Químicos da Água/química , Catálise , Micro-Ondas
13.
J Environ Sci (China) ; 84: 97-111, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31284920

RESUMO

Heterogeneous photocatalytic reaction has been generally applied for degradation of toxic contaminants. Degradations of a compound using the same kind of catalyst that was synthesized differently are commonly found in literature. However, the reported degradation intermediates are normally inconsistent. This issue is especially important for the degradation of toxic compounds because intermediates may be more toxic than their parent compounds and understanding the reason is necessary if appropriate catalysts are to be designed. This work systematically compares the photocatalytic degradation of diuron, a toxic recalcitrant herbicide, on two forms of zinc oxide (ZnO), i.e., conventional particles with zinc- and oxygen-terminated polar surfaces as the dominating planes, and nanorods with mixed-terminated nonpolar surfaces. Experimental and theoretical results indicate that both the rate of reaction and the degradation pathway depend on the adsorption configuration of diuron onto the surface. Diuron molecules adsorb in different alignments on the two surfaces, contributing to the formation of different degradation intermediates. Both the aliphatic and aromatic sides of diuron adsorb on the polar surfaces simultaneously, leading to an attack by hydroxyl radicals from both ends. On the other hand, on the mixed-terminated surface, only the aliphatic part adsorbs and is degraded. The exposed surface is therefore the key factor controlling the degradation pathway. For diuron degradation on ZnO, a catalyst confined to mixed-terminated surfaces, i.e., ZnO nanorods, is more desirable, as it avoids the formation of intermediates with potent phytotoxicity and cytogenotoxicity.


Assuntos
Diurona/química , Fotólise , Poluentes Químicos da Água/química , Óxido de Zinco/química , Adsorção , Catálise , Cinética , Testes de Toxicidade , Vigna
14.
J Agric Food Chem ; 67(31): 8452-8458, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31294967

RESUMO

Insights into the environmental fates of nitrated polycyclic aromatic hydrocarbons (NPAHs) in edible vegetables are of great significance for better evaluating human exposure to NPAHs through the dietary pathway. In this work, a fluorescence quenching method using graphene quantum dots as a fluorescent probe was first applied for the in vivo determination of 9-nitroanthracene (9-NAnt) and 1-nitropyrene (1-NPyr) adsorbed on the leaf surfaces of living lettuce (Lactuca sativa L.) seedlings. Moreover, the photolysis kinetics and mechanisms of the two adsorbed NPAHs were discussed. The photodegradation kinetics followed the pseudo-first-order equation, and the photodegradation half-life of 1-NPyr (7.4 ± 0.2 h) was greater than that of 9-NAnt (2.3 ± 0.1 h). Anthraquinone and pyrenediones were identified to be the main photolytic products of 9-NAnt and 1-NPyr, respectively. Intramolecular rearrangement was the most reasonable mechanism for the NPAH photolysis. The photolysis-driven degradation exhibited a key role in scavenging NPAHs from the vegetable leaf, indicating the reduction of NPAH transportation in the food chain.


Assuntos
Alface/química , Nitratos/química , Folhas de Planta/química , Hidrocarbonetos Policíclicos Aromáticos/química , Poluentes Atmosféricos/química , Cinética , Alface/crescimento & desenvolvimento , Alface/efeitos da radiação , Fotólise/efeitos da radiação , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/efeitos da radiação , Plântula/química , Plântula/crescimento & desenvolvimento , Plântula/efeitos da radiação
15.
J Agric Food Chem ; 67(27): 7609-7615, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31257874

RESUMO

Shallow water systems are uniquely susceptible to environmental processes such as photolysis and hydrolysis that can influence the dissipation of pesticides into sediments. The fungicide dicloran has previously been shown to undergo photolysis and is reported to dissipate in soils and sediments. The photodegradation and dissipation of dicloran in freshwater and seawater was monitored in a laboratory-simulated shallow water system. While no difference was observed between freshwater and seawater systems in the presence of simulated sunlight, the dissipation of dicloran in dark trial systems differed between salinities; 30% of the applied mass dissipated into the sediment in freshwater vs 22% in seawater, and the photodegradation rate and half-life were also impacted by the presence of sediment. The potential for dicloran to dissipate and photodegrade affects the overall behavior of dicloran between waters. Differences in chemical behavior with sediment presence and potential for photodegradation have the capacity to impact organisms within the ecosystem and suggest that these factors may need to be implemented into chemical exposure assessments dependent upon location.


Assuntos
Compostos de Anilina/química , Água Doce/química , Sedimentos Geológicos/química , Fotólise , Água do Mar/química , Luz Solar , Ecossistema , Fungicidas Industriais/química , Solo/química , Poluentes Químicos da Água/química
16.
World J Microbiol Biotechnol ; 35(8): 116, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31332538

RESUMO

Exploration of renewable energy sources is an imperative task in order to replace fossil fuels and to diminish atmospheric pollution. Hydrogen is considered one of the most promising fuels for the future and implores further investigation to find eco-friendly ways toward viable production. Expansive processes like electrolysis and fossil fuels are currently being used to produce hydrogen. Biological hydrogen production (BHP) displays recyclable and economical traits, and is thus imperative for hydrogen economy. Three basic modes of BHP were investigated, including bio photolysis, photo fermentation and dark fermentation. Photosynthetic microorganisms could readily serve as powerhouses to successively produce this type of energy. Cyanobacteria, blue green algae (bio photolysis) and some purple non-sulfur bacteria (Photo fermentation) utilize solar energy and produce hydrogen during their metabolic processes. Ionic species, including hydrogen (H+) and electrons (e-) are combined into hydrogen gas (H2), with the use of special enzymes called hydrogenases in the case of bio photolysis, and nitrogenases catalyze the formation of hydrogen in the case of photo fermentation. Nevertheless, oxygen sensitivity of these enzymes is a drawback for bio photolysis and photo fermentation, whereas, the amount of hydrogen per unit substrate produced appears insufficient for dark fermentation. This review focuses on innovative advances in the bioprocess research, genetic engineering and bioprocess technologies such as microbial fuel cell technology, in developing bio hydrogen production.


Assuntos
Eletrólise , Hidrogênio/metabolismo , Fontes de Energia Bioelétrica , Reatores Biológicos/microbiologia , Cianobactérias/metabolismo , Fermentação , Hidrogenase/metabolismo , Oxigênio/metabolismo , Fotólise , Fotossíntese
17.
Environ Sci Pollut Res Int ; 26(24): 25286-25300, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31256404

RESUMO

Copper and zinc composite oxides (Cu2O/ZnO) were synthesized by an impregnation-reduction-air oxidation method. A series of Cu2O/ZnO/rGO ternary composites were prepared by coupling with graphene oxide (GO) with different mass fractions in a solvothermal reaction system. The microscopic morphology, crystal structure, and optical characteristics of the photocatalysts were characterized. The degradation of p-Nitrophenol (PNP) and polyacrylamide (PAM) by photocatalytic materials under simulated solar irradiation were studied, and the degradation kinetics were also investigated. The results showed that cubic Cu2O was modified by ZnO nanorods and distributed on rGO nanosheets. The ternary Cu2O/ZnO/rGO nanocomposites have stronger simulated solar absorption ability and higher photodegradation efficiency than pure ZnO and binary Cu2O/ZnO nanocomposites. When the amount of Cu2O/ZnO/rGO-10 was 0.3 g L-1, the degradation rate of 10 mg L-1 PNP reached 98% at 90 min and 99.6% of 100 mg L-1 PAM at 30 min. The photocatalytic degradation processes of PNP and PAM all followed the pseudo-first-order kinetic model. Free radical trapping experiments showed that superoxide radicals were the main active substances to improve photocatalytic efficiency. In addition, after four recycles, the catalytic efficiency of Cu2O/ZnO/rGO-10 was still over 90%. It showed that Cu2O/ZnO/rGO-10 was a promising catalyst for wastewater treatment because of its good photostability and reusability.


Assuntos
Resinas Acrílicas/química , Nanocompostos/química , Nitrofenóis/química , Catálise , Cobre/química , Grafite/química , Oxirredução , Óxidos/química , Fotólise , Óxido de Zinco/química
18.
Ecotoxicol Environ Saf ; 182: 109472, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31352210

RESUMO

In present study, reductive graphene oxide and silver nanoparticles co-comodified TiO2 nanotube arrays were prepared, and which was investigated to degrade tetrabromobisphenol A. The arrays co-modified with silver nanoparticles and reductive graphene oxide prepared by electrodeposition method exhibited good photoelectrocatalytic degradative activity for tetrabromobisphenol A, and the degradation efficiency reached 99.6% within 80 min. The synergistic effect of high photoresponse of Ag nanoparticles with their high capture ability for photogenerated electrons and the extended wavelength absorption range of reductive graphene oxide resulted in the highest degradation efficiencies. Degradation is postulated to follow a stepwise reductive debromination mechanism.


Assuntos
Recuperação e Remediação Ambiental/métodos , Grafite/química , Nanotubos/química , Bifenil Polibromatos/análise , Prata/química , Luz Solar , Titânio/química , Catálise , Eletrodos , Oxirredução , Fotólise , Bifenil Polibromatos/efeitos da radiação
19.
Environ Sci Process Impacts ; 21(8): 1393-1402, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31322150

RESUMO

The hydroxyl radical (OH) is one of the most important oxidants controlling the oxidation capacity of the indoor atmosphere. One of the main OH sources indoors is the photolysis of nitrous acid (HONO). In this study, real-time measurements of HONO, nitrogen oxides (NOx) and ozone (O3) in an indoor environment in Guangzhou, China, were performed under two different conditions: (1) in the absence of any human activity and (2) in the presence of cooking. The maximum NOx and HONO levels drastically increased from 15 and 4 ppb in the absence of human activity to 135 and 40 ppb during the cooking event, respectively. The photon flux was determined for the sunlit room, which has a closed south-east oriented window. The photon flux was used to estimate the photolysis rate constants of NO2, J(NO2), and HONO, J(HONO), which span the range between 8 × 10-5 and 1.5 × 10-5 s-1 in the morning from 9:30 to 11:45, and 8.5 × 10-4 and 1.5 × 10-4 s-1 at noon, respectively. The OH concentrations calculated by photostationary state (PSS) approach, observed around noon, are very similar, i.e., 2.4 × 106 and 3.1 × 106 cm-3 in the absence of human activity and during cooking, respectively. These results suggest that under "high NOx" conditions (NOx higher than a few ppb) and with direct sunlight in the room, the NOx and HONO chemistry would be similar, independent of the geographic location of the indoor environment, which facilitates future modeling studies focused on indoor gas phase oxidation capacity.


Assuntos
Poluição do Ar em Ambientes Fechados/análise , Radical Hidroxila/análise , Óxidos de Nitrogênio/análise , Ácido Nitroso/análise , Ozônio/análise , Fotólise , China , Culinária , Humanos , Modelos Teóricos , Ácido Nitroso/efeitos da radiação , Oxirredução , Ozônio/efeitos da radiação , Luz Solar
20.
Environ Sci Pollut Res Int ; 26(25): 26134-26145, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31280443

RESUMO

Nitrous acid (HONO) is an important atmospheric pollutant that can strongly absorb ultraviolet irradiation in the region of 300-400 nm, as previously reported. Since the solar irradiance that reaches the surface of the earth has wavelengths greater than 290 nm, the photodissociation of HONO is considered the major method of hydroxyl radical formation in the troposphere. Thus, the photoinduced chemical reactivity of HONO is important. The present work investigated the reaction mechanism and kinetic parameters of HONO and sulfamethazine by using a laser flash photolysis technique and liquid chromatography-mass spectrometry. The results indicated that the sulfamethazine degradation rate was influenced by the HONO concentration and the initial concentration of sulfamethazine. Hydroxyl radicals derived from the photolysis of HONO attacked the aromatic ring of sulfamethazine to form sulfamethazine-OH adducts with a second-order rate constant of (3.8 ± 0.3) × 109 L mol-1 s-1. This intermediate would then react with HO· and oxygen molecules. The reaction rate constants of sulfamethazine-OH adducts with oxygen are (1.3 ± 0.1) × 107 L mol-1 s-1. The generation of sulfanilic acid and pyrimidine implies that the breaking down of S-N bonds of sulfamethazine and its HO adducts probably occur at the same time.


Assuntos
Radical Hidroxila/química , Ácido Nitroso/química , Oxigênio/química , Sulfametazina/química , Cinética , Fotólise , Raios Ultravioleta , Água/química
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