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1.
Chemosphere ; 262: 127895, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32799151

RESUMO

In order to improve the adsorption efficiency of ammonia nitrogen in low temperature wastewater, the modified activated carbon (Fe-AC) was prepared by impregnation-calcination modification of Fe(NO3)3. The characterization results indicated that the total pore volume, specific surface area and the point of zero charge of activated carbon increased after modification. A better adsorption effect was achieved under neutral condition than under alkaline or acidic condition. The effect of Ca2+ on competitive adsorption of NH4+ was greater than that of Na+ when both cations were present. Pseudo-first-order kinetic model was confirmed to be consistent with Fe-AC adsorption kinetic data, and Langmuir model was consistent with adsorption isotherm data. The adsorption thermodynamics demonstrated that the ammonia nitrogen adsorption process by Fe-AC was spontaneous and low-temperature was helpful to improve the adsorption capacity. The mechanism of adsorption of ammonia nitrogen by Fe-AC was the comprehensive effect of physical adsorption and chemical adsorption, which was the essential reason for improving the adsorption efficiency of ammonia nitrogen by Fe-AC at a low temperature. This research offered a new way for the modification of activated carbon and a new method for the removal of ammonia nitrogen at a low temperature.


Assuntos
Amônia/química , Carvão Vegetal/química , Águas Residuárias/química , Poluentes Químicos da Água/química , Adsorção , Temperatura Baixa , Ferro/química , Cinética , Nitrogênio/química , Temperatura , Termodinâmica , Poluentes Químicos da Água/análise
2.
Ecotoxicol Environ Saf ; 205: 111317, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32950807

RESUMO

Electrolytic manganese residue (EMR) is a solid waste remained in filters after using sulfuric acid to leaching manganese carbonate ore. EMR contains high concentration of soluble manganese (Mn2+) and ammonia nitrogen (NH4+-N), which seriously pollutes the environment. In this study, a low cost of phosphate based binder for Mn2+ and NH4+-N stabilization in EMR by low grade-MgO (LG-MgO) and superphosphate was studied. The effects of different types of stabilizing agent on the concentrations of NH4+-N and Mn2+, the pH of the EMR leaching solution, stabilizing mechanisms of NH4+-N and Mn2+, leaching test and economic analysis were investigated. The results shown that the pH of the EMR leaching solution was 8.07, and the concentration of Mn2+ was 1.58 mg/L, both of which met the integrated wastewater discharge standard (GB8978-1996), as well as the concentration of NH4+-N decreased from 523.46 mg/L to 32 mg/L, when 4.5 wt.% LG-MgO and 8 wt.% superphosphate dosage were simultaneously used for the stabilization of EMR for 50 d Mn2+ and NH4+-N were mainly stabilized by Mn3(PO4)2·2H2O, MnOOH, Mn3O4, Mn(H2PO4)2·2H2O and NH4MgPO4·6H2O. Economic evaluation revealed that the treatment cost of EMR was $ 11.89/t. This study provides a low-cost materials for NH4+-N and Mn2+ stabilization in EMR.


Assuntos
Amônia/química , Manganês/química , Amônia/análise , Carbonatos , Eletrólise , Eletrólitos/química , Poluentes Ambientais/análise , Manganês/análise , Nitrogênio/análise , Fosfatos/química , Resíduos Sólidos/análise , Águas Residuárias/química
3.
Nat Commun ; 11(1): 3880, 2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32759942

RESUMO

Geological sources of H2 and abiotic CH4 have had a critical role in the evolution of our planet and the development of life and sustainability of the deep subsurface biosphere. Yet the origins of these sources are largely unconstrained. Hydration of mantle rocks, or serpentinization, is widely recognized to produce H2 and favour the abiotic genesis of CH4 in shallow settings. However, deeper sources of H2 and abiotic CH4 are missing from current models, which mainly invoke more oxidized fluids at convergent margins. Here we combine data from exhumed subduction zone high-pressure rocks and thermodynamic modelling to show that deep serpentinization (40-80 km) generates significant amounts of H2 and abiotic CH4, as well as H2S and NH3. Our results suggest that subduction, worldwide, hosts large sources of deep H2 and abiotic CH4, potentially providing energy to the overlying subsurface biosphere in the forearc regions of convergent margins.


Assuntos
Ecossistema , Hidrogênio/química , Metano/química , Minerais/química , Compostos Orgânicos/química , Termodinâmica , Amônia/química , Fenômenos Químicos , Fenômenos Geológicos , Sulfeto de Hidrogênio/química , Fenômenos Mecânicos , Fenômenos de Química Orgânica , Alcaloides de Triptamina e Secologanina/química , Erupções Vulcânicas
4.
PLoS One ; 15(8): e0238386, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853235

RESUMO

Moving Bed Biofilm Reactors (MBBRs) can efficiently treat wastewater by incorporating suspended biocarriers that provide attachment surfaces for active microorganisms. The performance of MBBRs for wastewater treatment is, among other factors, contingent upon the characteristics of the surface area of the biocarriers. Thus, novel biocarrier topology designs can potentially increase MBBR performance in a significant manner. The goal of this work is to assess the performance of 3-D-printed biofilter media biocarriers with varying surface area designs for use in nitrifying MBBRs for wastewater treatment. Mathematical models, rendering, and 3D printing were used to design and fabricate gyroid-shaped biocarriers with a high degree of complexity at three different levels of specific surface area (SSA), generally providing greater specific surface areas than currently available commercial designs. The biocarriers were inoculated with a nitrifying bacteria community, and tested in a series of batch reactors for ammonia conversion to nitrate, in three different experimental configurations: constant fill ratio, constant total surface area, and constant biocarrier media count. Results showed that large and medium SSA gyroid biocarriers delivered the best ammonia conversion performance of all designs, and significantly better than that of a standard commercial design. The percentage of ammonia nitrogen conversion at 8 hours for the best performing biocarrier design was: 99.33% (large SSA gyroid, constant fill ratio), 94.74% (medium SSA gyroid, constant total surface area), and 92.73% (large SSA gyroid, constant biocarrier media count). Additionally, it is shown that the ammonia conversion performance was correlated to the specific surface area of the biocarrier, with the greatest rates of ammonia conversion (99.33%) and nitrate production (2.7 mg/L) for manufactured gyroid biocarriers with a specific surface area greater than 1980.5 m2/m3. The results suggest that the performance of commercial MBBRs for wastewater treatment can be greatly improved by manipulation of media design through topology optimization.


Assuntos
Biofilmes/crescimento & desenvolvimento , Reatores Biológicos/microbiologia , Águas Residuárias/análise , Águas Residuárias/microbiologia , Amônia/química , Bactérias/crescimento & desenvolvimento , Meios de Comunicação de Massa , Nitratos/química , Nitrificação/fisiologia , Nitrogênio/química , Impressão Tridimensional , Eliminação de Resíduos Líquidos/métodos
5.
Nat Commun ; 11(1): 3535, 2020 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-32669568

RESUMO

Macrophages are professional phagocytes known to play a vital role in controlling Mycobacterium tuberculosis (Mtb) infection and disease progression. Here we compare Mtb growth in mouse alveolar (AMs), peritoneal (PMs), and liver (Kupffer cells; KCs) macrophages and in bone marrow-derived monocytes (BDMs). KCs restrict Mtb growth more efficiently than all other macrophages and monocytes despite equivalent infections through enhanced autophagy. A metabolomics comparison of Mtb-infected macrophages indicates that ornithine and imidazole are two top-scoring metabolites in Mtb-infected KCs and that acetylcholine is the top-scoring in Mtb-infected AMs. Ornithine, imidazole and atropine (acetylcholine inhibitor) inhibit Mtb growth in AMs. Ornithine enhances AMPK mediated autophagy whereas imidazole directly kills Mtb by reducing cytochrome P450 activity. Intranasal delivery of ornithine or imidazole or the two together restricts Mtb growth. Our study demonstrates that the metabolic differences between Mtb-infected AMs and KCs lead to differences in the restriction of Mtb growth.


Assuntos
Autofagia/efeitos dos fármacos , Ornitina/farmacologia , Tuberculose/tratamento farmacológico , Ureia/química , Amônia/química , Animais , Apoptose , Arginase/química , Atropina/farmacologia , Proliferação de Células , Progressão da Doença , Feminino , Imidazóis/farmacologia , Macrófagos do Fígado/efeitos dos fármacos , Macrófagos do Fígado/microbiologia , Macrófagos Alveolares/efeitos dos fármacos , Macrófagos Alveolares/microbiologia , Macrófagos Peritoneais/efeitos dos fármacos , Macrófagos Peritoneais/microbiologia , Camundongos , Camundongos Endogâmicos C57BL , Óxido Nítrico/química , Fosfatidilserinas/química , RNA Interferente Pequeno/metabolismo , Espécies Reativas de Oxigênio/química
6.
Artigo em Inglês | MEDLINE | ID: mdl-32684079

RESUMO

The aim of this study was to interpret the development of Anammox activity by a mathematical model in an UASB reactor -originally inoculated with methanogenic granules- at which Anammox progress has been also experimentally observed while treating chicken manure digestate. Since ammonium is derived from anaerobic degradation of nitrogenous compounds in chicken manure similar to any other nitrogen-rich organic wastes; the reactor was operated intentionally at favorable conditions [i.e.; with external nitrite source for NH4 +:NO2 -≅1.0] in order to make Anammox process to prevail as operation continued. Results indicated significant ammonia removals (60% on average) although influent concentration was gradually increased up to 200 mg L-1. A modeling exercise has been undertaken to investigate the performance of the laboratory scale UASB reactor. In this scope, the experimental results were modeled by using Mantis2 model within GPS-X 6.5 simulation software that included several built in libraries. Accordingly, effluent chemical oxygen demand (COD) and total ammonia nitrogen (TAN) concentrations could be predicted with reasonably good accuracy demonstrating successful calibration. The regression coefficient (R2 ) and mean relative absolute error (MRAE) parameters were found as 0.66 and 16% and 0.70 and 19%, respectively.


Assuntos
Amônia/isolamento & purificação , Esterco , Amônia/química , Animais , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Galinhas , Nitrogênio/química , Oxirredução , Eliminação de Resíduos Líquidos
7.
J Chromatogr A ; 1624: 461201, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540063

RESUMO

Nowadays, sensitive chiral methods are required for the determination of chiral impurities and for assays in biological samples. Supercritical fluid chromatography (SFC), one of the main techniques to separate chiral molecules, can be coupled to MS to provide such sensitive methods. Moreover, chiral separation strategies are very useful to reduce the development time and cost of such methods. This study investigates the transfer of an existing non-MS compatible screening step (as part of a separation strategy) into an MS-compatible one. The initial step had a cumulative success rate of 100 % for 57 tested compounds using methanol or 2-propanol as mobile phase modifier on one of four chiral stationary phases. The additives applied in the original mobile phases, i.e. isopropylamine and trifluoroacetic acid, negatively affect the ionization in SFC-MS and thus need to be replaced. Formic acid, acetic acid, water, ammonia, ammonium acetate and ammonium formate were investigated as MS-compatible additives in different combinations and concentrations. Only methanol-based mobile phases were considered in this study because high system pressures were obtained with isopropanol. The other experimental parameters remained the same as in the initial screening step. The effects of the alternative additives on the obtained resolutions as well as on the global success rate were investigated. The best alternative MS-compatible mobile phase contained 0.5 % CH3COOH and 40 mM NH3 as additives. This mobile phase provided the highest number of separations and rather high resolutions. An MS-compatible screening step was defined with this alternative mobile phase. Compared to the original additives, a similar success rate was obtained.


Assuntos
Cromatografia com Fluido Supercrítico/métodos , Acetatos/química , Ácido Acético/química , Amônia/química , Formiatos/química , Espectrometria de Massas , Estereoisomerismo
8.
Chemosphere ; 257: 127215, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32505950

RESUMO

Red mud, as industrial solid waste, causes severe environmental problems such as soil alkalization and groundwater pollution. In this work, we researched and developed the red mud as a selective catalytic reduction catalyst for NOx removal with NH3 (NH3-SCR). After selective dissolution and specific heat treatment, different Ce precursors were used to modifying its physical and chemical properties. The results showed that Ce(NO3)3 and Ce(NH4)2(NO3)6 modified red mud (RMcn and RMcan) had excellent SCR performance below 300 °C. Ce(SO4)2 modified red mud (RMcs) showed relatively low NOx conversions at 200-300 °C. The redox property was improved with the Ce(NO3)3 and Ce(NH4)2(NO3)6, while depressed with the Ce(SO4)2. Agglomerates generated on the RMcs and blocked the accumulated pores due to the formation of Ce2(SO4)3. The surface acidity of RMcs enhanced with increased adsorption for ammonia. However, these new adsorbed ammonia species, highly related to the sulfate from the Ce2(SO4)3, were inert and did not react with the adsorbed or gaseous NO species at 200-300 °C. The abundant surface lattice oxygen from CeO2 microcrystals improved the catalytic oxidation capacity of the RMcn and RMcan.


Assuntos
Cério/química , Adsorção , Amônia/química , Catálise , Óxidos de Nitrogênio , Oxirredução , Óxidos/química , Oxigênio , Sulfatos/química , Propriedades de Superfície
9.
Food Chem ; 324: 126898, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32361096

RESUMO

Reactions involving reactive carbonyls, creatinine, and ammonia-producing compounds were investigated in order to clarify the formation of the heterocyclic aromatic amine (HAA) 2-amino-3,4-dimethylimidazo(4,5-f)quinoline (MeIQ). Obtained results showed that MeIQ was only produced when 2-butenal (crotonaldehyde) was present. Reaction yields depended on the pH, with a maximum around pH 6.5, and on concentrations of crotonaldehyde and creatinine. Ammonia was also required for MeIQ formation, but ammonia was produced by creatinine decomposition. The amount of MeIQ formed increased with reaction time, temperature, and oxygen content in the reaction atmosphere. Activation energy for MeIQ formation from crotonaldehyde, creatinine, and glutamine was 72.2 ± 0.4 kJ·mol-1. A reaction pathway that explains MeIQ formation is proposed. Obtained results suggest a main role of reactive carbonyls formed in foods (the food carbonylome) on HAA formation. In addition, they provide scientific basis for the understanding of how HAAs are formed and could be mitigated.


Assuntos
Aldeídos/química , Creatinina/química , Quinolinas/química , Amônia/química , Cromatografia Líquida de Alta Pressão , Compostos Heterocíclicos/química , Concentração de Íons de Hidrogênio , Oxigênio/química , Quinolinas/análise , Espectrometria de Massas em Tandem , Temperatura
10.
Chemosphere ; 255: 126931, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402879

RESUMO

A lab-scale biotrickling filter (BTF) packed with porcelain Rasching ring and ceramsite was applied for co-treating of low concentrations of hydrogen sulfide (H2S) and ammonia (NH3), as major pollutants typically found in e.g., intensive livestock production facilities. In this study, the outlet gas concentrations of H2S and NH3 were used for indicators if the treated gas reached odor-free condition. Overall, excellent removal efficiencies were obtained for both H2S and NH3 in the BTF during Stage I (H2S alone) and Stage II (H2S and NH3). Specifically, the H2S outlet concentration was below the detection limit (∼3.6 ppbv) and the NH3 outlet concentration was less than 0.4 ppmv when the inlet concentrations of H2S and NH3 were around 1.8 ppmv and 35.3 ppmv, respectively. In this case, the running empty bed residence time was 10.2 s. During Stage II, the outlet H2S concentration was decreased significantly when the inlet NH3 concentration was increased, likely due to the influence by pH. Meanwhile, the outlet nitrous oxide (N2O) concentration was kept low (<2% NH3) during the experiment, suggesting a proper operation of the BTF. After the inlet gas shifted from H2S alone at Stage I to H2S and NH3 at Stage II, the main sulfur-oxidizing bacteria (SOB) species in the BTF switched from Acidithiobacillus to Thiobacillus.


Assuntos
Amônia/química , Reatores Biológicos , Sulfeto de Hidrogênio/química , Bactérias , Filtração
11.
Food Chem ; 328: 127100, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32464558

RESUMO

Pyridines are produced during food processing and are important flavor compounds. In spite of that, their formation pathways are still poorly understood, in particular those related to 3-hydroxypyridines. In an attempt to fill this gap, this study describes, for the first time, precursors and reaction pathways leading to 3-hydroxypyridine formation. 3-Hydroxypyridines are produced by reaction of lipid-derived reactive carbonyls and ammonia-producing compounds and were studied by using gas chromatography coupled to mass spectrometry. Their main precursors resulted to be 4,5-epoxy-2-alkenals and 2,4-alkadienals. 3-Hydroxypyridines were produced at temperatures higher than 100 °C, at slightly basic pH values, and with an activation energy of about 50 kJ/mol. A reaction pathway that explains their formation in the course of the lipid oxidation pathway is proposed. The role of lipid oxidation on the production of 3-hydroxypyridines was confirmed by studying their formation in oxidized linseed and menhaden oils heated in the presence of glutamine.


Assuntos
Amônia/química , Manipulação de Alimentos , Lipídeos/química , Piridinas/química , Temperatura Alta , Óleo de Semente do Linho/química , Oxirredução
12.
Chemosphere ; 253: 126896, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32402467

RESUMO

High concentrations of manganese (Mn2+) and ammonia nitrogen (NH4+-N) in electrolytic manganese residue (EMR) have seriously hindered the sustainable development of electrolytic manganese industry. In this study, an innovative basic burning raw material (BRM) was used to stabilize/solidify Mn2+ and NH4+-N in EMR. The characteristics of EMR and BRM, stabilize mechanism of NH4+-N and Mn2+, and leaching test were investigated. The concentrations of NH4+-N and Mn2+ were 12.8 mg/L and 0.1 mg/L, respectively, when the solid liquid ratio was 1.5:1, and the mass ratio of EMR and BRM was 100:10, at the temperature of 20 °C reacting for 12 h Mn2+ was mostly solidified as bustamite ((Mn,Ca)Si2O6), groutite (MnOOH) and ramsdellite (MnO2). NH4+-N was mostly recycled by (NH4)2SO4 and (NH4)3H(SO4)2. Leaching test results indicated that the concentrations of heavy metals were within the permitted level for the integrated wastewater discharge standard (GB8978-1996). Economic evaluation revealed that the cost of EMR treatment was $ 10.15/t by BRM. This study provided a new research idea for EMR harmless disposal.


Assuntos
Amônia/química , Materiais de Construção/análise , Eletrólitos/química , Compostos de Manganês/química , Nitrogênio/química , Reciclagem , Gerenciamento de Resíduos/métodos , China , Metais Pesados/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise
13.
Chemosphere ; 252: 126458, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32199163

RESUMO

In/H-Beta catalyst was prepared by optimizing the support, concentration of ion exchange liquid and calcination temperature to investigate the effects of synthesis conditions on catalytic activity of selective catalytic reduction of NOx with CH4. The results showed that the In/H-Beta catalyst exhibited the superior activity when concentration of exchange liquid was 0.033 M and calcination temperature was 500 °C, the NOx removal ratio could reach 97.6%. In addition, reaction conditions could affect the catalytic performance. When O2 concentration was 10%, CH4:NO ratio was no less than one, space velocity was lower than 23600 h-1 and NO initial concentration was no more than 700 ppm, In/H-Beta could exhibit superior catalytic activity. Moreover, the catalytic performances of In/H-Beta catalysts were discussed after enduring H2O or/and SO2. This novel strategy could open the door for selective catalytic reduction of NOx with CH4.


Assuntos
Amônia/química , Óxidos de Nitrogênio/química , Catálise , Modelos Químicos , Oxirredução , Temperatura
14.
Ecotoxicol Environ Saf ; 194: 110384, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32126412

RESUMO

Electrolytic manganese residue (EMR) contains a large amount of NH4+-N and Mn2+ and can negatively impact the environment. A stabilization treatment of soluble contaminants in the EMR is necessary for its reuse and safe stacking. This study presents experimental results for the stabilization of NH4+-N and Mn2+ in the EMR using phosphogypsum leachate as a low-cost phosphate source and MgO/CaO (PLMC) process. The results demonstrated that the stabilization efficiency of NH4+-N and Mn2+ was 93.65% and 99.99%, respectively, under the following conditions: a phosphogypsum leachate dose of 1.5 mL g-1, an added MgO dose of 0.036 g g-1, an added CaO dose of 0.1 g g-1 and a reaction time of 2 h. The stabilization effect of the PLMC process was higher and more cost effective than that of using Na3PO4·12H2O and MgO/CaO. The concentration of NH4+-N and Mn2+ in the leaching liquor decreased to 80 mg L-1 and 0.5 mg L-1, respectively, after the stabilization under the optimum conditions. The stabilization characteristics indicated that NH4+-N was stabilized to form NH4MgPO4·6H2O (struvite) and that Mn2+ was stabilized to form Mn5(PO4)2(OH)4, Mn3(PO4)2·3H2O and Mn(OH)2. PO43--P, F-, and heavy metal ions of the phosphogypsum leachate were removed from the leaching liquor and stabilized in the treated EMR.


Assuntos
Compostos de Cálcio/química , Sulfato de Cálcio/química , Óxido de Magnésio/química , Manganês/análise , Óxidos/química , Fósforo/química , Amônia/análise , Amônia/química , Eletrólise , Eletrólitos , Poluentes Ambientais/análise , Poluentes Ambientais/química , Resíduos Industriais/análise , Manganês/química , Solubilidade , Estruvita/análise , Estruvita/química
15.
Soft Matter ; 16(11): 2725-2735, 2020 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-32115597

RESUMO

Transmembrane pH gradient poly(isoprene)-block-poly(ethylene glycol) (PI-b-PEG) polymersomes were investigated for their potential use in the detoxification of ammonia, a metabolite that is excessively present in patients suffering from urea cycle disorders and advanced liver diseases, and which causes neurotoxic effects (e.g., hepatic encephalopathy). Polymers varying in PI and PEG block length were synthesized via nitroxide-mediated polymerization and screened for their ability to self-assemble into polymersomes in aqueous media. Ammonia sequestration by the polymersomes was investigated in vitro. While most vesicular systems were able to capture ammonia in simulated intestinal fluids, uptake was lost in partially dehydrated medium mimicking conditions in the colon. Polymeric crosslinking of residual olefinic bonds in the PI block increased polymersome stability, partially preserving the ammonia capture capacity in the simulated colon environment. These more stable vesicular systems hold promise for the chronic oral treatment of hyperammonemia.


Assuntos
Amônia/química , Portadores de Fármacos/química , Encefalopatia Hepática/tratamento farmacológico , Inativação Metabólica/genética , Amônia/metabolismo , Butadienos/química , Butadienos/farmacologia , Portadores de Fármacos/farmacologia , Fluoresceína-5-Isotiocianato/química , Hemiterpenos/química , Hemiterpenos/farmacologia , Encefalopatia Hepática/etiologia , Encefalopatia Hepática/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Hepatopatias/complicações , Hepatopatias/tratamento farmacológico , Hepatopatias/metabolismo , Metacrilatos/química , Tamanho da Partícula , Polietilenoglicóis/química , Polietilenoglicóis/farmacologia , Polimerização , Polímeros/química , Polímeros/farmacologia , Força Próton-Motriz/efeitos dos fármacos , Distúrbios Congênitos do Ciclo da Ureia/complicações , Distúrbios Congênitos do Ciclo da Ureia/tratamento farmacológico , Distúrbios Congênitos do Ciclo da Ureia/metabolismo , Água/metabolismo
16.
Org Lett ; 22(4): 1575-1579, 2020 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-32013447

RESUMO

An efficient one-pot synthesis of 4-(1H)-quinolones through an orthogonal engagement of diverse o-haloaryl ynones with ammonia in the presence of Cu(I), involving tandem Michael addition and ArCsp2-N coupling, is presented. The substrate scope of this convenient protocol, wherein ammonium carbonate acts as both an in situ ammonia source and a base toward diverse 2-substituted 4-(1H)-quinolones, has been mapped and its efficacy validated through concise total synthesis of bioactive natural products pseudanes (IV, VII, VIII, and XII), graveoline, graveolinine, and waltherione F.


Assuntos
Amônia/química , Cetonas/química , Metoxaleno/análogos & derivados , Quinolinas/síntese química , Quinolonas/síntese química , Metoxaleno/síntese química , Metoxaleno/química , Estrutura Molecular , Quinolinas/química , Quinolonas/química
17.
Chemosphere ; 250: 126272, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32109703

RESUMO

Reduction of harmful nitrogen oxides (NOx) from diesel engine exhausts is one of the key challenges in environmental protection, and can be achieved by NH3-assisted selective catalytic reduction (NH3-SCR) using copper-exchanged chabazite zeolites (i.e. Cu-CHA, including Cu-SSZ-13 and Cu-SAPO-34) as catalysts. Understanding the redox chemistry of Cu-CHA in NH3-SCR catalysis is crucial for further improving the NOx reduction efficiency. Here, a series of Cu-SSZ-13 catalysts with different Cu ion exchange levels were prepared, thoroughly characterized by different techniques such as X-ray diffraction, diffuse reflectance ultraviolet-visible spectroscopy and temperature-programmed desorption using NH3 as a probe molecule, etc., and tested in NH3-SCR reactions under steady-state conditions. In situ studies by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), supplemented with density-functional theory calculations, provided solid evidence for the formation of ammonium ion (NH4+) intermediates resulting from the reduction of Cu2+ to Cu+ by co-adsorbed NH3 and NO molecules on Cu-SSZ-13. Catalytic relevance of the NH4+ intermediates, as demonstrated by an increase of NO conversion over Cu-SSZ-13 pre-treated in NH3/NO atmosphere, can be attributed to the formation of closely coupled Cu+/NH4+ pairs promoting the Cu+ re-oxidation and, consequently, the overall NH3-SCR process. This study thus paves a new route for improving the NH3-SCR efficiency over Cu-CHA zeolite catalyst.


Assuntos
Amônia/química , Cobre/química , Óxidos de Nitrogênio/química , Zeolitas/química , Catálise , Teoria da Densidade Funcional , Poluição Ambiental/prevenção & controle , Oxirredução , Espectrofotometria Infravermelho , Emissões de Veículos/toxicidade
18.
Artigo em Inglês | MEDLINE | ID: mdl-32050414

RESUMO

Anaerobic ammonia oxidation (anammox) has been one of the most innovative discoveries for the treatment of wastewater with high ammonia nitrogen concentrations. The process has significant advantages for energy saving and sludge reduction, also capital costs and greenhouse gases emissions are reduced. Recently, the use of anammox has rapidly become mainstream in China. This study reviews the engineering applications of the anammox process in China, including various anammox-based technologies, selection of anammox reactors and attempts to apply them to different wastewater treatment plants. This review discusses the control and implementation of stable reactor operation and analyzes challenges facing mainstream anammox applications. Finally, a unique and novel perspective on the development and application of anammox in China is presented.


Assuntos
Anaerobiose , Reatores Biológicos , Esgotos , Águas Residuárias/química , Amônia/química , Amônia/metabolismo , Bactérias/metabolismo , Reatores Biológicos/microbiologia , China , Engenharia , Gases de Efeito Estufa , Humanos , Nitrogênio/química , Nitrogênio/metabolismo , Oxirredução , Esgotos/química , Esgotos/microbiologia , Águas Residuárias/microbiologia
19.
Sci Rep ; 10(1): 489, 2020 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-31949227

RESUMO

Soil nitrification via ammonia oxidation is a key ecosystem process in terrestrial environments, but little is known of how increasing irrigation of farmland soils with saline waters effects these processes. We investigated the effects of long-term irrigation with saline water on the abundances and community structures of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Irrigation with brackish or saline water increased soil salinity (EC1:5) and NH4-N compared to irrigation with freshwater, while NO3-N, potential nitrification rates (PNR) and amoA gene copy numbers of AOA and AOB decreased markedly under irrigation regimes with saline waters. Moreover, irrigation with brackish water lowered AOA/AOB ratios. PNR was positively correlated with AOA and AOB amoA gene copy numbers across treatments. Saline and brackish water irrigation significantly increased the diversity of AOA, as noted by Shannon index values, while saline water irrigation markedly reduced AOB diversity. In addition, irrigation with brackish or fresh waters resulted in higher proportions of unclassified taxa in the AOB communities. However, irrigation with saline water led to higher proportions of unclassified taxa in the AOA communities along with the Candidatus Nitrosocaldus genus, as compared to soils irrigated with freshwater. AOA community structures were closely associated with soil salinity, NO3-N, and pH, while AOB communities were only significantly associated with NO3-N and pH. These results suggest that salinity was the dominant factor affecting the growth of ammonia-oxidizing microorganisms and community structure. These results can provide a scientific basis for further exploring the response mechanism of ammonia-oxidizing microorganisms and their roles in nitrogen transformation in alluvial grey desert soils of arid areas.


Assuntos
Irrigação Agrícola/métodos , Amônia/química , Archaea/metabolismo , Bactérias/metabolismo , Nitrificação , Águas Salinas/química , Microbiologia do Solo , Proteínas Arqueais/genética , Proteínas Arqueais/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Variações do Número de Cópias de DNA , Ecossistema
20.
Carbohydr Polym ; 230: 115598, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31887938

RESUMO

We present a novel method for processing bacterial cellulose/graphene oxide (BC/GO) aerogels with multifunctional properties. The addition of a small amount of dimethyl sulfoxide (DMSO) to the aqueous dispersion of the nanomaterials during the gelification process affected the water freezing temperature of the system and thereby affecting the porous structure of the aerogel obtained after liophilization. The possibility to obtain small and elongated pore with axial orientation allowed a significant improvement of the structural stability of the aerogels. Moreover, the aerogels reduction by thermal treatment with ammonia gas induced crosslinking between the different nanophases, thus given an incremental factor for the mechanical performance of the aerogels under harsh conditions. The resulting aerogels also showed significant improvements in terms of thermal stability and electrical conductivity. These multifunctional BC/GO aerogels present high potential as sustainable and ecological alternative materials for lightweight packaging, filters for atmosphere and water treatment, or energy applications.


Assuntos
Celulose/análogos & derivados , Grafite/química , Amônia/química , Reagentes para Ligações Cruzadas/química , Dimetil Sulfóxido/química , Condutividade Elétrica , Géis/química , Temperatura Alta , Oxirredução , Porosidade
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