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1.
Chemosphere ; 247: 125968, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32069733

RESUMO

It was revealed that Anammox process promotes the anaerobic degradation of benzene under denitrification. This study investigates the effect of dissimilatory nitrate reduction to ammonium (DNRA) and exogenous ammonium on anaerobic ammonium oxidation bacteria (AnAOB) during the anaerobic degradation of benzene under denitrification. The results indicate that anammox occurs synergistically with organisms using the DNRA pathway, such as Draconibacterium and Ignavibacterium. Phylogenetic analysis showed 64% (16/25) and 36% (5/25) hzsB gene sequences, a specific biomarker of AnAOB, belonged to Candidatus 'Brocadia fuldiga' and Candidatus 'Kuenenia', respectively. Exogenous ammonium addition enhanced the anammox process and accelerated benzene degradation at a 1.89-fold higher average rate compared to that in the absence of exogenous ammonium and AnAOB belonged to Ca. 'Kuenenia' (84%) and Ca. 'Brocadia fuldiga' (16%). These results indicate that Ca. 'Brocadia fuldiga' could also play a role in DNRA. However, the diversity of abcA and bamA, the key anaerobic benzene metabolism biomarkers, remained unchanged. These findings suggest that anammox occurrence may be coupled with DNRA or exogenous ammonium and that anammox promotes anaerobic benzene degradation under denitrifying conditions. The results of this study contribute to understanding the co-occurrence of DNRA and Anammox and help explore their involvement in degradation of benzene, which will be crucial for directing remediation strategies of benzene-contaminated anoxic environment.


Assuntos
Compostos de Amônio/química , Anaerobiose , Bactérias/metabolismo , Benzeno/metabolismo , Desnitrificação , Recuperação e Remediação Ambiental/métodos , Compostos de Amônio/metabolismo , Bactérias/genética , Reatores Biológicos/microbiologia , Nitratos , Nitrogênio/metabolismo , Oxirredução , Filogenia
2.
Top Curr Chem (Cham) ; 378(1): 16, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31942682

RESUMO

The cooperation between two orthogonal catalytic events during the formation of carbon-carbon and carbon-heteroatom bonds has emerged as an effective strategy for enantioselective chemical synthesis. In recent years, a number of pioneering investigations have described useful chemical synthesis methods whereby the reactivity or nucleophile-electrophile combinations can be fine-tuned or extended far beyond the effect and influence of a single catalyst. The recognition of this has had profound implications for the development cooperative catalysis as a field and has provided a foundation for the development of broadly useful chemical synthesis methods. This chapter focuses on the combination of tertiary amine Lewis base and transition metal catalysts, which the authors hope will simulate further developments and advances.


Assuntos
Compostos de Amônio/química , Bases de Lewis/química , Metais/química , Carbono/química , Catálise , Técnicas de Química Sintética/métodos , Estereoisomerismo , Elementos de Transição/química
3.
Chem Commun (Camb) ; 56(10): 1549-1552, 2020 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-31930244

RESUMO

In accordance with the rapid increase in demand for selective and spatial chemical tagging, and accurate detection of proteins of interest, we develop a sensitive protein detection method, termed "Supra-blot" capitalizing on high-affinity host-guest interaction between cucurbit[7]uril (CB[7]) and adamantylammonium (AdA). The method can directly detect chemically tagged proteins without false-positive signals caused by endogenous biomolecules. Not only a single specific protein, but also spatially localized proteins in cells were labeled with AdA, and selectively detected by a host molecule-enzyme hybrid, CB[7]-conjugated horseradish peroxidase (CB[7]-HRP) generating amplified chemiluminescence signals. This study shows the great potential of Supra-blot for accurate and reliable detection of proteins of interest in cells.


Assuntos
Hidrocarbonetos Aromáticos com Pontes/química , Peroxidase do Rábano Silvestre/química , Imidazóis/química , Medições Luminescentes/métodos , Amantadina/química , Compostos de Amônio/química , Células HEK293 , Histonas/química , Histonas/metabolismo , Peroxidase do Rábano Silvestre/metabolismo , Humanos
4.
Chemosphere ; 242: 125233, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896207

RESUMO

Acid/base/oxidant pretreatment influenced subsequent quaternary ammonium epoxide compounds modified carbon (QAE-AC) and hence PFOA and nitrate removal. This work discerned that the most favorable QAE-AC protocol for PFOA removal was achieved when the wood carbon pretreated with HNO3 to adjust the carbon's slurry pH to 4.77, and tailored with the QUAB188. For nitrate removal, the most favorable when the carbon was pretreated with NaOH to raise the carbon's slurry pH to 9.34, and then loaded with the QUAB360. Based on experimentally results and molecular model, we found that pore volume, phenolic groups and the surface charge were the main factors affecting the PFOA removal, while the only factor affecting nitrate removal was surface charge. The QUAB's epoxide functionalities have cross-linked with phenolics along the activated carbon's graphene edge sites. QAE is preferentially reacted with the phenolic in the micropores and mesopores of carbon, and some QAE molecules form new "pore-like structures" outside the pores with the graphene planes or other QAE molecules. This pore-like structure hosted adsorption capacity by the quaternary ammonium. The favorable PFOA adsorption sites were in smaller mesopores via both hydrophobic interaction and electrostatic interaction; and nitrate sorption was occurring in the smaller micropores via anion exchange. Therefore, it can be considered that QAE-AC can simultaneously adsorb PFOA and nitrate in water.


Assuntos
Caprilatos/química , Fluorcarbonetos/química , Modelos Químicos , Nitratos/química , Compostos de Amônio Quaternário/química , Poluentes Químicos da Água/química , Adsorção , Compostos de Amônio/química , Ânions , Carvão Vegetal/química , Compostos de Epóxi , Oxidantes , Água
5.
Environ Sci Pollut Res Int ; 27(8): 8350-8358, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31902072

RESUMO

The change in particulate matter (PM)2.5 composition in relation to precursors over recent decades has not been elucidated clearly in Beijing. Using ground-based measurements from the literature, this study investigated the yearly time series of PM2.5 and its chemical composition over Beijing from 1999 to 2016 to identify the driving forces underlying these changes. The PM2.5 concentration declined slightly, due to the organic carbon, elemental carbon, and dust rather than to either sulfate-nitrate-ammonium (SNA) aerosols. Before 2013, the trend of SNA aerosols was opposite to that of PM2.5; however, subsequently, SNA aerosols have represented the major contribution to the reduction of PM2.5, coinciding with a large decline of regional precursor gases. The yearly time series of SNA aerosols can be explained better by regional precursor gases than by local ones. Generally, precursor gases emissions over the region of North China Plain can be controlled if Beijing's air quality is to be improved.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Compostos de Amônio , Sulfatos/química , Compostos de Sulfidrila/química , Aerossóis , Poluentes Atmosféricos/química , Compostos de Amônio/química , Pequim , China , Material Particulado , Estações do Ano
6.
Environ Sci Pollut Res Int ; 27(7): 7493-7503, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31884547

RESUMO

In this study, a novel MgO-biochar composite was generated for nutrient recovery from biogas slurry using magnesium chloride (MgCl2) and ammonia hydroxide (NH3·H2O). Biochar properties, including pH, CEC, pHpzc, magnesium content, surface area, and total pore volume (Vtotal), were evaluated. Moreover, the removal of NH4+ and PO43- in both single and bi-solute system were investigated. Results indicated that NH3·H2O pretreatment and MgO-coating enhanced biochar pH, CEC, and pHpzc. Additionally, there were generally higher surface area and Vtotal in MgAWS550. The maximum adsorption capacities for NH4+ and PO43-, respectively, increased as WS550 (0.555 and 1.57 mg g-1) < MgWS550 (15.4 and 21.8 mg g-1) < MgAWS550 (17.5 and 31.3 mg g-1). Moreover, higher removal efficiencies were achieved in the bi-solute system, and over 25% and 90% of NH4+ and PO43-, respectively, was removed from biogas slurry by MgASW550. Mechanically, NH4+ removal was mainly attributed to ionic exchange, while PO43- adsorption on MgO-coated biochars was due to electrostatic attraction and precipitation. Furthermore, the formation of struvite (MgNH4PO4·6H2O) further enhanced N and P in the bi-solute system.


Assuntos
Compostos de Amônio/análise , Carvão Vegetal/química , Óxido de Magnésio/análise , Fosfatos/análise , Adsorção , Compostos de Amônio/química , Hidrólise , Óxido de Magnésio/química , Fosfatos/química
7.
Chemosphere ; 245: 125606, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31855756

RESUMO

The accumulation of ammonia in water bodies can cause eutrophication and reduce water quality. Furthermore, 80% of the ammonia in the world is consumed as fertilizer, which makes it a resource that can be recovered under the circular economy concept. Then, ammonia from wastewater can be valorised for agricultural applications. Liquid-liquid membrane contactors (LLMCs) have been postulated as a novel and eco-friendly technology for ammonia recovery, because they can convert dissolved ammonia into ammonium salts by an acid stripping solution. The concentration of the ammonium salt produced is limited by the co-transport of water in LLMC. Further concentration by electrodialysis (ED) is presented as a solution to overcome this problem. In this work, ammonia streams with different initial ammonia concentrations (1.7-4.0 g/L) were treated by LLMCs to produce liquid ammonium salt fertilizers (as NH4NO3 and NH4H2PO4). Then, these ammonium solutions were concentrated by ED in order to achieve the nitrogen content required for direct application in agriculture for fertigation. After the LLMC process, the fertilizer obtained was composed of approximately 5.1% or 10.1% (w/w) nitrogen, depending on the initial ammonia concentration. After that, it was possible to concentrate these ammonium salts by a factor of 1.6 ± 0.3 using ED with an optimal energy consumption of 0.21 ± 0.08 kWh/kg ammonium salt and 93.1 ± 4.2% of faradaic yield. This gave a liquid fertilizer composed of 15.6% (w/w) nitrogen as NH4NO3. Overall, it was possible to integrate two innovative membrane technologies for the valorisation and concentration of nutrients from ammonia wastewater streams.


Assuntos
Amônia/isolamento & purificação , Compostos de Amônio/química , Fertilizantes , Membranas Artificiais , Águas Residuárias/química , Agricultura/métodos , Amônia/análise , Nitrogênio/análise , Reciclagem
8.
Food Chem ; 308: 125682, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-31655479

RESUMO

In this work, a multifunctional food packaging composite coating with transparent, biodegradable, antifogging and antibacterial properties was designed and fabricated by quaternary ammonium salt modified chitosan (HACC) and poly (vinyl alcohol) (PVA) via a facile and environment-friendly solution casting method. A simple quaternization modification enabled the coating simultaneously to achieve excellent antifogging and antibacterial functions. The excellent antifogging property of the HACC/PVA composite coating was attributed to the strong water absorbency of quaternary ammonium chitosan and PVA. A nearly 98% transmittance ratio of coated glasses was achieved during antifogging test. In addition, the inhibition rate of the HACC/PVA composite coating kill against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Botrytis cinerea were up to ~99%. The antibacterial effect was demonstrated by each group of strawberries after storage for 1, 3, 5 days. The multifunctional coating has broad prospects in the application of fruit and vegetable packaging.


Assuntos
Compostos de Amônio/química , Antibacterianos/farmacologia , Quitosana/farmacologia , Embalagem de Alimentos , Quitosana/química , Escherichia coli/efeitos dos fármacos , Compostos de Amônio Quaternário , Staphylococcus aureus/efeitos dos fármacos
9.
Chemosphere ; 238: 124654, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524611

RESUMO

Nitrate is a byproduct of the anaerobic ammonium oxidation (anammox) process and is related to its electron transfer. However, little is known about the influence of nitrate on the anammox process. In this work, the biphasic effect of exogenous nitrate on the anammox process was investigated in an upflow biofilter (UBF) reactor with ammonium as the sole electron donor. The responses of anammox to increased nitrate were analyzed by one-way ANOVA test and found to be significantly different under a constant and decreased nitrite condition (p < 0.01). With a single increase in nitrate and constant ammonium and nitrite in the influent, the total nitrogen removal rate (TNRR) of anammox was uninhibited, but stoichiometry deviated and nitrate production always showed a linear decrease. In contrast, anammox exhibited a range of activity with constant ammonium and simultaneously increased nitrate and decreased nitrite in the influent, including a continuous reduction of TNRR, a nonpersistent ammonium overconsumption and a pronounced nonlinear response of nitrate production. Correlation analysis shows that the lack of ammonium overconsumption was accompanied by the disappearance of nitrate underproduction. Kinetic models of product formation were effectively used to explore the nitrate production behavior of anammox subjected to increased nitrate, and the metabolite of nitrate was divided into a growth negative coupling type and growth (partial) coupling type under a constant and decreased nitrite condition, respectively. These findings collectively suggest that nitrate has a biphasic effect on the anammox process and is correlated with the availability of nitrite.


Assuntos
Compostos de Amônio/química , Anaerobiose/efeitos dos fármacos , Nitratos/farmacologia , Reatores Biológicos , Desnitrificação , Cinética , Nitratos/química , Nitritos/química , Nitrogênio/química , Oxirredução
10.
J Environ Sci (China) ; 86: 24-37, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31787188

RESUMO

Problems associated with water eutrophication due to high phosphorus concentrations and related environmentally safe solutions have attracted wide attention. A novel bis(diallyl alkyl tertiary ammonium salt) polymer, particularly poly(N1,N1,N6,N6-tetraallylhexane-1,6-diammonium dichloride) (PTAHDADC), was synthesized and characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, mercury intrusion method, and thermogravimetric analysis. The adsorption characteristics in phosphorus were evaluated in dilute solution, and the recycling properties of PTAHDADC were investigated. Results showed that PTAHDADC possessed macropores with a size distribution ranging from 30 to 130 µm concentrating at 63 µm in diameter and had 46.52% of porosity, excellent thermal stability below 530K, and insolubility. PTAHDADC could effectively remove phosphorus at pH = 7-11 and had a removal efficiency exceeding 98.4% at pH = 10-11. The adsorption equilibrium data of PTAHDADC for phosphorus accorded well with the Langmuir and pseudo-second-order kinetic models. Maximum adsorption capacity was 52.82 mg/g at 293 K. PTAHDADC adsorbed phosphorus rapidly and reached equilibrium within 90 min. Calculated activation energy Ea was 15.18 kJ/mol. PTAHDADC presented an excellent recyclability with only 8.23% loss of removal efficiency after five adsorption-desorption cycles. The morphology and structure of PTAHDADC slightly changed as evidenced by the pre- and post-adsorption of phosphorus, but the process was accompanied by the partial deprotonation of the (-CH2)3NH+ group of PTAHDADC. The adsorption was a spontaneous exothermic process driven by entropy through physisorption, electrostatic attraction, and ion exchange. Survey results showed that PTAHDADC was a highly efficient and fast-adsorbing phosphorus-removal material prospective in treating wastewater.


Assuntos
Compostos de Amônio/química , Fósforo/química , Polímeros/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Compostos de Amônio/análise , Águas Residuárias
11.
J Agric Food Chem ; 67(49): 13509-13517, 2019 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-31725280

RESUMO

In this study, novel water-soluble quaternary ammonium salts of iminofullerenes (IFQA) were synthesized by nitrene chemistry in combination with quaternization and identified as [C60(NCH2CH2NH3+·CF3COO-)4·10H2O]n by various spectroscopies. Maize and Arabidopsis seeds were used to test the bioactivity of IFQA in seed germination. Compared with the control, maize seed exposure to 50 mg/L IFQA (normal: 73.1% vs 58.7%; drought: 66.7% vs 50.0% at the second day) and Arabidopsis seed exposure to 20 mg/L IFQA (normal: 77.5% vs 58.8%; drought: 63.3% vs 36.7% at the second day) had higher germination rates and quicker germination. The results of two-dimensional gel electrophoresis combined with mass spectroscopy showed that the abundance of 21 proteins in embryo proteome of maize seeds was significantly changed (>1.5 fold). The downregulated six storage proteins and upregulated four proteins induced by IFQA for energy production and sugar metabolism indicated a faster metabolic activity of maize seed germination. The upregulated eight stress-related proteins and antioxidant enzymes suggested that the role of IFQA was to activate the metabolic processes in seed germination and also increase seed stress response. The results provide important information to understand the mechanism of seed germination enhancement by carbon nanomaterials.


Assuntos
Compostos de Amônio/farmacologia , Arabidopsis/crescimento & desenvolvimento , Fulerenos/farmacologia , Reguladores de Crescimento de Planta/farmacologia , Sementes/efeitos dos fármacos , Triticum/crescimento & desenvolvimento , Compostos de Amônio/química , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Arabidopsis/metabolismo , Fulerenos/química , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Germinação/efeitos dos fármacos , Reguladores de Crescimento de Planta/síntese química , Reguladores de Crescimento de Planta/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Sementes/genética , Sementes/crescimento & desenvolvimento , Sementes/metabolismo , Triticum/efeitos dos fármacos , Triticum/genética , Triticum/metabolismo
12.
Chem Commun (Camb) ; 55(90): 13546-13549, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31647068

RESUMO

Drugs containing amine groups react with CO2 to form crystalline ammonium carbamates or carbamic acids. In this approach, both the cation and anion of the salt, or the neutral CO2 adduct, are derived from the parent drug, generating new crystalline versions in a 'masked' or prodrug form. It is proposed that this approach may serve as a valuable new tool in engineering the physical properties of drugs for formulation purposes.


Assuntos
Aminas/química , Compostos de Amônio/química , Carbamatos/química , Dióxido de Carbono/química , Ânions/química , Cátions/química , Cristalografia por Raios X , Modelos Moleculares , Estrutura Molecular , Sais/química
13.
Chemosphere ; 226: 934-944, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31509923

RESUMO

The anaerobic ammonium oxidation (anammox) process has the advantages of a high nitrogen removal rate, low operational cost, and small footprint and has been successfully implemented to treat high-content ammonium wastewater. However, very little is known about the toxicity of the heavy metal element Ni(II) to the anammox process. In this study, the short- and long-term effects of Ni(II) on the anammox process in an upflow anaerobic sludge blanket (UASB) reactor were revealed. The results of the short-term batch test showed that the half maximal inhibitory concentration (IC50) of Ni(II) on anammox biomass was 14.6 mg L-1. A continuous-flow experiment was performed for 150 days of operation, and the results illustrated that after domestication, the achieved nitrogen removal efficiency was up to 93±0.03% at 10 mg L-1 Ni(II). The settling velocity, specific anammox activity and EPS content decreased as the Ni(II) concentration increased. Nevertheless, the content of heme c increased as the Ni(II) increased. These results indicate that short-term exposure to Ni(II) has an adverse impact on anammox process, but the anammox system could tolerate 10 mg L-1 Ni(II) stress after acclimation during continuous-flow operation for 150 days. High-throughput sequencing results indicated that the presence of Ni(II) had an impact on the microbial community composition in the anammox reactor, especially Candidatus Kuenenia. At Ni(II) concentrations of 0-10 mg L-1, the relative abundance of Candidatus Kuenenia decreased from 36.23% to 28.46%.


Assuntos
Compostos de Amônio/química , Bactérias/metabolismo , Reatores Biológicos/microbiologia , Níquel/química , Nitrogênio/química , Esgotos/química , Águas Residuárias/química , Anaerobiose , Bactérias/crescimento & desenvolvimento , Oxirredução
14.
Environ Sci Pollut Res Int ; 26(31): 32209-32223, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31494857

RESUMO

CO2 and H2S removal from flue gases is indispensable to be done for protection of environment with respect to global warming as well as clean air. Chemical absorption is one of the most developed and capable techniques for the removal of these sour gases. Among the many solvents, ionic liquids (ILs) are more capable due to their desirable green solvent properties. However, ILs being usually costlier, the blends of ILs and amines are more suggestive for absorption. In the present work, various essential characterization properties such as density, viscosity, sound velocity, and refractive index of two ionic liquid-amine blend systems viz. (1) 2-Hydroxy ethyl ammonium formate (HEF) + 1-(2-aminoethyl) piperazine (AEP) and (2) 2-Hydroxy ethyl ammonium formate (HEF) + 2-Amino-2-methyl-1-propanol (AMP) are reported. The temperature range for which all the measurements were conducted is 298.15 to 333.15 K. For both systems of (HEF + AEP) and (HEF + AMP), HEF mass fractions were varied from 0.2 to 0.8.The density and viscosity results were correlated as a function of temperature and concentration of ionic liquid and amine with Redlich-Kister and Grunberg-Nissan models, respectively. Moreover, feed forward neural network model (ANN) is explored for correlating experimentally determined sound velocity and refractive index data. The measured properties are further analyzed to estimate various thermodynamic as well as transport properties such as diffusivity of CO2/H2S in the (HEF + AEP) and (HEF + AMP), thermal expansion coefficients, and isentropic compressibility, ΔG0, ΔS0, ΔH0, using the available models in the literature.


Assuntos
Monofosfato de Adenosina/análise , Compostos de Amônio/química , Dióxido de Carbono/química , Líquidos Iônicos/química , Íons/química , Acústica , Monofosfato de Adenosina/química , Aminas , Ésteres do Ácido Fórmico/química , Temperatura Alta , Reologia , Solventes/química , Temperatura , Termodinâmica , Viscosidade
15.
Molecules ; 24(18)2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31487829

RESUMO

4,8-Dihydrodifurazano[3,4-b,e]pyrazine (DFP) is one kind of parent compound for the synthesis of various promising difurazanopyrazine derivatives. In this paper, eleven series of energetic salts composed of 4,8-dihydrodifurazano[3,4-b,e]pyrazine-based anions and ammonium-based cations were designed. Their densities, heats of formation, energetic properties, impact sensitivity, and thermodynamics of formation were studied and compared based on density functional theory and volume-based thermodynamics method. Results show that ammonium and hydroxylammonium salts exhibit higher densities and more excellent detonation performance than guanidinium and triaminoguanidinium salts. Therein, the substitution with electron-withdrawing groups (-NO2, -CH2NF2, -CH2ONO2, -C(NO2)3, -CH2N3) contributes to enhancing the densities, heats of formation, and detonation properties of the title salts, and the substitution of -C(NO2)3 features the best performance. Incorporating N-O oxidation bond to difurazano[3,4-b,e]pyrazine anion gives a rise to the detonation performance of the title salts, while increasing their impact sensitivity meanwhile. Importantly, triaminoguanidinium 4,8-dihydrodifurazano[3,4-b,e]pyrazine (J4) has been successfully synthesized. The experimentally determined density and H50 value of J4 are 1.602 g/cm3 and higher than 112 cm, which are consistent with theoretical values, supporting the reliability of calculation methods. J4 proves to be a thermally stable and energetic explosive with decomposition peak temperature of 216.7 °C, detonation velocity 7732 m/s, and detonation pressure 25.42 GPa, respectively. These results confirm that the derivative work in furazanopyrazine compounds is an effective strategy to design and screen out potential candidates for high-performance energetic salts.


Assuntos
Compostos de Amônio/química , Ânions/química , Cátions/química , Modelos Teóricos , Pirazinas/química , Sais/química , Algoritmos , Estrutura Molecular , Sensibilidade e Especificidade , Termodinâmica
16.
Mater Sci Eng C Mater Biol Appl ; 104: 109961, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500022

RESUMO

Formation of fungal biofilms on health care-related materials causes serious clinical consequences. This study reports a novel fungal repelling strategy to control fungal biofilm formation on denture biomaterials through layer-by-layer self-assembly (LBL). Amphiphilic quaternary ammonium chitosans (CS612) were synthesized and used as the antimicrobial positive layer, and sodium alginate (SA) was chosen as the negative layer to construct LBL multilayers on poly (methyl methacrylate) (PMMA)-based denture materials. The presence of LBL multilayers on denture disc was confirmed and characterized by surface zeta potential, water contact angle, AFM, and FT-IR analyses. The multilayer coatings, especially CS612 as the outmost layer, effectively prevented the fungal initial adhesion and biofilm formation. The Candida cells avoided the multilayer coatings and suspended in broth solution instead of forming biofilms, suggesting that the LBL multilayers had fungal repelling effects. The LBL multilayers were biocompatible toward mammalian cells. In stability tests, after immersion in PBS for 4 weeks under constant shaking and repeated brushing with a denture brush for up to 3000 times, the biofilm-controlling effects of the LBL multilayers were not affected, pointing to a novel long-term strategy in controlling fungal biofilms on denture and other related biomaterials.


Assuntos
Alginatos/química , Compostos de Amônio/química , Biofilmes/efeitos dos fármacos , Candida/efeitos dos fármacos , Quitosana/química , Materiais Revestidos Biocompatíveis/farmacologia , Materiais Dentários/farmacologia , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Materiais Revestidos Biocompatíveis/química , Materiais Dentários/química , Polimetil Metacrilato/farmacologia , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Propriedades de Superfície/efeitos dos fármacos
17.
J Environ Sci (China) ; 85: 177-188, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31471025

RESUMO

The effect of preparation parameters on the performance of zeolite for ammonium (20-300 mg N/L) adsorption from simulated wastewater is reported. It was found that the ratios of Na2O/SiO2 and Si/Al had a more important influence than crystallization time on zeolite adsorption properties. Relatively low Na2O/SiO2 ratios were beneficial for fabrication of zeolites with high proportions of micropore area and volume, which led to the surface adsorption mechanism being dominated by surface free energy and pore effects. However, with decreasing Si/Al ratios, the effect of ion-exchange was more prominent due to the high negative surface potential of zeolite. In addition, the concentration of weak acid sites on the zeolites was increased with lower ratios of Na2O/SiO2 and Si/Al, which may promote ammonium removal. Therefore, the most effective zeolite for ammonium removal, which was fabricated at Na2O/SiO2 = 1.375, Si/Al = 4 and crystallization time of 48 hr, exhibited the cooperative effects of adsorption, ion-exchange and a large amount of weak acid sites. The maximum ammonium adsorption capacity (35.06 ±â€¯0.98 mg/g) and the removal efficiency (94.44% ±â€¯4.00%) were obtained at the dosage of 4.0 g/L zeolite NaX at ammonium concentrations of 300 mg N/L and 20 mg N/L, respectively. The Freundlich isotherm and pseudo-first-order kinetics models provided excellent fitting for the ammonium adsorption process. In addition, zeolite NaX showed about 1.23-3.2 times the ammonium adsorption capacity of clinoptilolite. The stable and efficient reusability of zeolite NaX after five regeneration cycles demonstrated that this adsorbent has considerable potential for practical industrial applications.


Assuntos
Compostos de Amônio/química , Modelos Químicos , Zeolitas/química , Adsorção
18.
Bioresour Technol ; 291: 121888, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31374413

RESUMO

A coupled microbial fuel cell (MFC) system, consisting of a nitrifying sulfide removal MFC and a denitrifying sulfide removal MFC, was assembled to simultaneously treat ammonium and sulfide in wastewater. It provided a promising approach to recover electricity from wastewater containing sulfide and ammonium. Considering both substrate removal and electricity generation performance, the desirable feeding S/N molar ratio was deemed as 3 and the optimal temperature was found to be 30 °C. Under this condition, the coupled MFC achieved a sum coulomb production of 554.8 C/d, a total nitrogen removal efficiency of 58.7 ±â€¯1.3% and a sulfur production percent of 27.4 ±â€¯0.4-33.3 ±â€¯0.9%. The introduction of nitrifiers and electroactive oxic microbes from the oxic-cathode chamber into the anoxic-cathode chamber favored nitrogen removal.


Assuntos
Fontes de Energia Bioelétrica , Nitrogênio/isolamento & purificação , Sulfetos/isolamento & purificação , Águas Residuárias/química , Compostos de Amônio/química , Desnitrificação , Eletricidade , Eletrodos
19.
Anal Chim Acta ; 1081: 120-130, 2019 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-31446949

RESUMO

Mass spectrometry-based approaches enable us to capture changes in the metabolome in biological systems with high sensitivity and resolution. But global MS-based profiling of the bile acids (BAs) submetabolome is still a challenging task. Particularly for unconjugated BAs, the collision-induced dissociation (CID) fragment ions showed low ion intensities which were insufficient for analysis. This study is aimed at the development of an anion attachment MS-based approach for pseudotargeted profiling of the BAs submetabolome. We demonstrated that anion attachment MS with the combination use of ammonia fluoride (NH4F) and formate could provide stable anionic adduct ([M + HCOO]-) with good MS responses for unconjugated BAs. A mechanistic study revealed that the underlying rationale is due to the NH4F-induced approximate matching of attractions between BAs and anion for the 24-carboxyl hydrogen. This 24-carboxyl hydrogen regioselectivity is useful to screen for potential unconjugated BAs from the biological matrix. The stability and regioselectivity of anion attachment allowed the establishment of SRM transitions for unconjugated BAs for the first time. To profile conjugated BAs that come from the conjugation of glycine or taurine at 24-carboxyl hydrogen, specific precursor/fragment ion transitions were used for the detection. Finally, SRM-based UPLC-MS/MS method was developed for the pseudotargeted profiling of the BAs submetabolome with good linearity (r2 > 0.995) and high sensitivity (0.20-1.37 ng mL-1 for LLOQ). With this method, a total of 83 BAs, covering 45 unconjugated BAs and 38 conjugated BAs, were successfully determined in different biosamples from experimental colitis mice. The BAs metabolism homeostasis was disrupted by colitis, characterized by the decreased BAs levels in serum and excessive BAs accumuation in the gall bladder and colon. Overall, the present anion attachment MS-based approach is sufficiently sensitive and robust to comprehensively measure various BAs.


Assuntos
Compostos de Amônio/química , Ácidos e Sais Biliares/análise , Fluoretos/química , Metabolômica/métodos , Animais , Bile/química , Ácidos e Sais Biliares/química , Cromatografia Líquida de Alta Pressão/métodos , Colite/induzido quimicamente , Colite/metabolismo , Colo/metabolismo , Vesícula Biliar/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Dodecilsulfato de Sódio , Espectrometria de Massas por Ionização por Electrospray/métodos , Sulfassalazina/farmacologia
20.
Chemosphere ; 236: 124324, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31310972

RESUMO

Plants benefit from the simultaneous uptake of nitrate (NO3-) and ammonium (NH4+), which can influence the bioaccumulation of heavy metals. Nevertheless, there are no studies on the effect of nitrogen forms on grasses used for cadmium (Cd) phytoextraction. The objective was to evaluate the response of Panicum maximum cv. Tanzania to NO3-/NH4+ ratios and Cd levels. A 3 × 3 factorial experiment was conducted under greenhouse conditions, in a randomized complete block design replicated three times, with three NO3-/NH4+ ratios (100/0, 70/30 and 50/50) and three Cd levels (0.0, 0.5 and 1.0 mM). Although it increased plant total nitrogen concentration, Cd exposure reduced shoot and root growth. Moreover, it altered nitrogen metabolism and induced the accumulation of NO3- and NH4+ mainly in shoots. The supply of 50/50 disturbed glutamine synthetase activity and changed root morphology under Cd toxicity. However, while the exclusive use of NO3- mitigated toxicity symptoms, by favoring Cd accumulation in roots and maintaining normal nitrogen metabolism, plants grown with 50/50 showed increased uptake, transport and accumulation of this metal. Thus, Cd uptake and accumulation are strongly related to the form of nitrogen available, and the supply of 50/50 increases the phytoextraction of this metal.


Assuntos
Compostos de Amônio/química , Cádmio/toxicidade , Nitrogênio/química , Raízes de Plantas/química , Tanzânia
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