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1.
PLoS One ; 15(9): e0239034, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32946514

RESUMO

Manganese oxide (MnO) nanoparticles (NPs) can serve as robust pH-sensitive contrast agents for magnetic resonance imaging (MRI) due to Mn2+ release at low pH, which generates a ~30 fold change in T1 relaxivity. Strategies to control NP size, composition, and Mn2+ dissolution rates are essential to improve diagnostic performance of pH-responsive MnO NPs. We are the first to demonstrate that MnO NP size and composition can be tuned by the temperature ramping rate and aging time used during thermal decomposition of manganese(II) acetylacetonate. Two different temperature ramping rates (10°C/min and 20°C/min) were applied to reach 300°C and NPs were aged at that temperature for 5, 15, or 30 min. A faster ramping rate and shorter aging time produced the smallest NPs of ~23 nm. Shorter aging times created a mixture of MnO and Mn3O4 NPs, whereas longer aging times formed MnO. Our results indicate that a 20°C/min ramp rate with an aging time of 30 min was the ideal temperature condition to form the smallest pure MnO NPs of ~32 nm. However, Mn2+ dissolution rates at low pH were unaffected by synthesis conditions. Although Mn2+ production was high at pH 5 mimicking endosomes inside cells, minimal Mn2+ was released at pH 6.5 and 7.4, which mimic the tumor extracellular space and blood, respectively. To further elucidate the effects of NP composition and size on Mn2+ release and MRI contrast, the ideal MnO NP formulation (~32 nm) was compared with smaller MnO and Mn3O4 NPs. Small MnO NPs produced the highest amount of Mn2+ at acidic pH with maximum T1 MRI signal; Mn3O4 NPs generated the lowest MRI signal. MnO NPs encapsulated within poly(lactide-co-glycolide) (PLGA) retained significantly higher Mn2+ release and MRI signal compared to PLGA Mn3O4 NPs. Therefore, MnO instead of Mn3O4 should be targeted intracellularly to maximize MRI contrast.


Assuntos
Compostos de Manganês/química , Nanopartículas Metálicas/química , Óxidos/química , Meios de Contraste/química , Imagem por Ressonância Magnética/métodos , Nanopartículas/química , Temperatura , Fatores de Tempo
2.
Chemosphere ; 261: 127778, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32739692

RESUMO

Vibration is one of the most prevalent energy sources in natural environment, which can also be harvested and utilized to drive chemical reaction. Herein, mechanical vibration is used for enhancing the catalytic decomposition of formaldehyde at ambient temperature with the assistance of four well-defined morphologies α-MnO2 (nanowire, nanotube, nanorod and nanoflower). In particular, α-MnO2 nanowire exhibits the best catalytic activity, which can completely mineralize formaldehyde into carbon dioxide at ambient temperature by harvesting the vibration energy. To the best of our knowledge, this may be the first report that α-MnO2, as a non-noble metal catalyst, can completely decompose formaldehyde to carbon dioxide at ambient temperature. The characterization results show that α-MnO2 nanowire has a much higher oxygen vacancy concentration than other three catalysts. In addition, thermal effect generated from friction between nanoparticles induced by ultrasonic vibration may enhance its catalytic activity. More importantly, it is the vibration that effectively promotes the activation of O2 adsorbed on the surface oxygen vacancy to produce more , thus increasing the catalytic decomposition performance. The strategy presented herein demonstrates a new approach for efficient use of mechanical vibration to improve catalytic activity of traditional catalysts.


Assuntos
Poluentes Atmosféricos/química , Formaldeído/química , Compostos de Manganês/química , Nanoestruturas/química , Adsorção , Carcinógenos , Catálise , Nanopartículas , Nanotubos/química , Nanofios , Oxirredução , Óxidos/química , Oxigênio/química , Temperatura , Vibração
3.
Nature ; 583(7816): 453-458, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32669693

RESUMO

Manganese is one of the most abundant elements on Earth. The oxidation of manganese has long been theorized1-yet has not been demonstrated2-4-to fuel the growth of chemolithoautotrophic microorganisms. Here we refine an enrichment culture that exhibits exponential growth dependent on Mn(II) oxidation to a co-culture of two microbial species. Oxidation required viable bacteria at permissive temperatures, which resulted in the generation of small nodules of manganese oxide with which the cells associated. The majority member of the culture-which we designate 'Candidatus Manganitrophus noduliformans'-is affiliated to the phylum Nitrospirae (also known as Nitrospirota), but is distantly related to known species of Nitrospira and Leptospirillum. We isolated the minority member, a betaproteobacterium that does not oxidize Mn(II) alone, and designate it Ramlibacter lithotrophicus. Stable-isotope probing revealed 13CO2 fixation into cellular biomass that was dependent upon Mn(II) oxidation. Transcriptomic analysis revealed candidate pathways for coupling extracellular manganese oxidation to aerobic energy conservation and autotrophic CO2 fixation. These findings expand the known diversity of inorganic metabolisms that support life, and complete a biogeochemical energy cycle for manganese5,6 that may interface with other major global elemental cycles.


Assuntos
Bactérias/metabolismo , Crescimento Quimioautotrófico , Manganês/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Ciclo do Carbono , Dióxido de Carbono/metabolismo , Técnicas de Cocultura , Perfilação da Expressão Gênica , Isótopos , Manganês/química , Compostos de Manganês/química , Compostos de Manganês/metabolismo , Oxirredução , Óxidos/química , Óxidos/metabolismo , Filogenia
4.
Chemosphere ; 259: 127503, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32645597

RESUMO

Fe-Mn nodules affect the speciation, transformation and migration of arsenic (As) via redox and adsorption reactions. However, few studies have been concerned with their interaction in the presence of dissolved oxygen. In this work, the interaction mechanism of As(III) and Fe-Mn nodules was studied in different atmospheres. The influence of pH, dissolved oxygen concentration and chemical composition of nodules on the reaction was also investigated. The results indicated that manganese oxides and iron oxides in nodules respectively contribute to As(III) oxidation and As(III,V) adsorption. Under oxic conditions, Fe-Mn nodules acted as a catalyst to accelerate the oxidation of Mn(II) to Mn(III,V) oxides, which significantly enhanced As(III) oxidation. In the system containing 10 mg L-1 As(III) and 1.0 g L-1 Fe-Mn nodules, the maximum oxidation capacity of As(III) reached 3.22, 3.48 and 3.71 mg g-1, and the corresponding As(III,V) adsorption capacity reached 2.49, 2.40, and 2.39 mg g-1 in nitrogen, air and oxygen atmosphere, respectively. The oxidation capacity of As(III) increased and decreased with increasing dissolved oxygen concentration and pH, respectively. This work clarifies the mechanism of As(III) oxidation by soil Fe-Mn nodules in various systems and contributes to a better understanding of the behaviors and fate of As in environments.


Assuntos
Arsênico/química , Arsenitos/química , Compostos Férricos/química , Compostos de Manganês/química , Óxidos/química , Oxigênio/química , Adsorção , Catálise , Oxirredução
5.
Chemosphere ; 260: 127500, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32688308

RESUMO

Lithium (Li+) is used in various applications involving pharmaceuticals, textile dyes, and batteries. Therefore, the demand for environmentally friendly and effective materials for Li+ uptake and recovery continues to increase. Herein, rice husk (RH) and coconut shell (CS) biomasses were used to fabricate honeycomb-networked biochar (BC) precursors via slow pyrolysis. RHBC- and CSBC-based MnO2 composites were synthesized by depositing MnO2 in various ratios onto RHBC and CSBC by varying the KMnO4 concentration (2%, 3%, and 4%), followed by simple ultrasonication and heat-treatment methodologies. The structural and physicochemical properties of all of the fabricated composites were analyzed using several different instrumental methods. The batch adsorption experiments were performed for comparative Li+-adsorption studies of RHBC-Mnx and CSBC-Mnx composites by optimizing several parameters (pH, adsorbent dose, Li+ initial concentration, and contact time). The comparative adsorption analysis revealed that the RHBC-Mnx composites exhibited stronger Li+-adsorption ability than the CSBC-Mnx composites and that increasing the MnO2 deposition to 3% in both cases led to maximum Li+ adsorption capacities (62.85 mg g-1 and 57.8 mg g-1), respectively. The kinetic studies show that Li+ adsorption proceeds through the pseudo-second-order mechanism. Li+ recovery was successfully carried out using HCl (eluting agent), thereby demonstrating the benefits of synthesized composites at the industrial scale. The current work indicates that the fabricated RHBC-Mnx and CSBC-Mnx composites may have potential for use as economical composites in eco-friendly applications such as Li+ adsorption and recovery from aqueous media.


Assuntos
Carvão Vegetal/química , Cocos/química , Lítio/análise , Compostos de Manganês/química , Oryza/química , Óxidos/química , Poluentes Químicos da Água/análise , Adsorção , Fontes de Energia Elétrica , Íons , Cinética , Resíduos Sólidos/análise
6.
J Vis Exp ; (160)2020 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-32628168

RESUMO

For biomedical applications, metal oxide nanoparticles such as iron oxide and manganese oxide (MnO), have been used as biosensors and contrast agents in magnetic resonance imaging (MRI). While iron oxide nanoparticles provide constant negative contrast on MRI over typical experimental timeframes, MnO generates switchable positive contrast on MRI through dissolution of MnO to Mn2+ at low pH within cell endosomes to 'turn ON' MRI contrast. This protocol describes a one-pot synthesis of MnO nanoparticles formed by thermal decomposition of manganese(II) acetylacetonate in oleylamine and dibenzyl ether. Although running the synthesis of MnO nanoparticles is simple, the initial experimental setup can be difficult to reproduce if detailed instructions are not provided. Thus, the glassware and tubing assembly is first thoroughly described to allow other investigators to easily reproduce the setup. The synthesis method incorporates a temperature controller to achieve automated and precise manipulation of the desired temperature profile, which will impact resulting nanoparticle size and chemistry. The thermal decomposition protocol can be readily adapted to generate other metal oxide nanoparticles (e.g., iron oxide) and to include alternative organic solvents and stabilizers (e.g., oleic acid). In addition, the ratio of organic solvent to stabilizer can be changed to further impact nanoparticle properties, which is shown herein. Synthesized MnO nanoparticles are characterized for morphology, size, bulk composition, and surface composition through transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy, respectively. The MnO nanoparticles synthesized by this method will be hydrophobic and must be further manipulated through ligand exchange, polymeric encapsulation, or lipid capping to incorporate hydrophilic groups for interaction with biological fluids and tissues.


Assuntos
Hidroxibutiratos/química , Compostos de Manganês/química , Manganês/química , Nanopartículas Metálicas/química , Óxidos/química , Pentanonas/química , Temperatura , Vidro/química , Interações Hidrofóbicas e Hidrofílicas , Nanopartículas Metálicas/ultraestrutura , Nitrogênio/química , Tamanho da Partícula , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Água/química , Difração de Raios X
7.
Chemosphere ; 258: 127334, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32540536

RESUMO

Herein, MgO cathode and graphene Mn-Ce bimetallic oxide were utilized to jointly enhance the removal of toluene in pulsed discharge plasma (PDP). Compared to the common cathode, the MgO cathode enhanced the density of high energy electrons, and then induced to higher removal of toluene. However, the removal of toluene by PDP/MgO system was still insufficient, and there was a large amount of underutilized O3 in the products. Based on this, Mn-Ce/graphene catalysts were introduced into PDP/MgO system. The Mn-Ce (8:1)/graphene catalyst had the highest catalytic activity. Under the discharge power of 2.1 W, toluene degradation rate and CO2 selectivity increased by 27.5% and 22.0%, respectively. This was ascribed to the synergistic effect of the solid solution formed between MnOx and CeOx, increasing the proportion of Oads on the surface of the catalyst. The higher Oads/Olatt ratio lead to the better catalytic activity, which was conducive to the complete transformation of the intermediate products to CO2 and H2O. According to the detected products, the degradation pathway and the mechanism of toluene degradation were proposed finally. The PDP itself, field emission effect of MgO cathode and catalytic effect of Mn-Ce/graphene for jointly improve the toluene removal and CO2 selectivity.


Assuntos
Técnicas Eletroquímicas/métodos , Grafite/química , Óxido de Magnésio/química , Tolueno/isolamento & purificação , Dióxido de Carbono , Catálise , Cério/química , Eletrodos , Compostos de Manganês/química , Óxidos/química , Água
8.
Chemosphere ; 258: 127329, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32540535

RESUMO

Due to the neutral charge of As(III) oxy-ions that make approaching the traditional adsorbent very improbable compared to the As(V) case, making it harder to be separated. To enhance the adsorption of As(Ш), the FeOOH coated cellulose acetate (CA) membrane doped with MnO2 nanoparticles (FeOOH@MnO2@CAM) was fabricated and then to removes As(Ш) in water through the synergistic effect of oxidation and adsorption, and the maximum adsorption capacity can reach 50.34 mg/g. FeOOH@MnO2@CAM was fabricated with CA as a substrate by dipping-precipitation phase inversion and hydrothermal method. Langmuir and pseudo-second-order model showed that As(Ш) was adsorbed by chemical interactions through the monolayer and thermodynamic showed that As(Ш) adsorption was an exothermic and spontaneous process. The results of the pH study showed that as the pH increases from 3 to 11, the adsorption capacity of As(Ш) decreases from 50.34 to 14.32 mg/g, which was attributed to the acidic environment promoting the protonation of the surface of FeOOH@MnO2@CAM, which increases the electrostatic attraction, and the alkaline environment increases electrostatic repulsion due to deprotonation. The competitive ions exhibited the PO43- significantly reduce the adsorption capacity of As(Ш),and as the PO43- content increases, the adsorption capacity of As(Ш) decreases from 29.76 to 18.57 mg/g, which was attributed to the similar chemical properties of PO43- and arsenate. Importantly, FeOOH@MnO2@CAM still maintains an adsorption capacity of 20.19 mg/g after seven cycles, demonstrating that it is a kind of environmentally friendly material to remove As(Ш) in the water environment.


Assuntos
Arsênico/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Compostos de Manganês/química , Oxirredução , Óxidos/química , Água
9.
Food Chem ; 331: 127090, 2020 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-32593035

RESUMO

Chlorothalonil is a class of 2B carcinogen which is widely used in the prevention and treatment of fungal diseases in food samples. Its residual problem has been increasingly concerned by society. In this paper, a fast and simple colorimetric assay based on Manganese dioxide nanosheets (MnO2 NSs)-oxidize 3,3',5,5'-tetramethylbenzidine (TMB) platform was used to detect residual pesticide chlorothalonil in food samples. Under optimal conditions, the half maximal inhibitory concentration and the limit of detection of chlorothalonil were 3.27 and 0.024 ng/mL. There were no obvious cross-reactivity between chlorothalonil and interference substances. The recoveries shown the satisfactory results. The results of colorimetric assay for the authentic samples were largely consistent with gas chromatography. Therefore, the proposed method would be convenient and satisfactory analytical methods for the monitoring of chlorothalonil. Furthermore, the MnO2 - TMB system was used to produce test strips for quick and convenient visual detection of chlorothalonil with good performance.


Assuntos
Colorimetria/métodos , Análise de Alimentos/métodos , Compostos de Manganês/química , Nanoestruturas/química , Nitrilos/análise , Óxidos/química , Benzidinas/química , Colorimetria/instrumentação , Análise de Alimentos/instrumentação , Contaminação de Alimentos/análise , Fungicidas Industriais/análise , Limite de Detecção , Oxirredução , Oxirredutases/química
10.
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
11.
Chemosphere ; 253: 126623, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32302916

RESUMO

Monensin, an ionophore antibiotic, is commonly administered as a feed additive to cattle and poultry. A large percentage of the administered dose is excreted in animal waste, which is often applied to agricultural fields as fertilizer. The objective of this work is to gain insight into the fate of monensin in soil by investigating the interactions between monensin and common soil minerals, including sorption and transformation to unmonitored partial oxidation products. Batch sorption experiments across varying conditions (i.e., pH, ionic strength) and desorption experiments (i.e., methanol, PO43-, methyl tert-butyl ether) were used to determine the extent to which a selection of common redox-active soil minerals [birnessite (δ-MnO2), goethite (α-FeOOH), hematite (α-Fe2O3)] can bind and transform monensin. Monensin was bound by hematite (pH < 7.5, up to 7.5 mmol kg-1), goethite (pH < 7.5, up to 3.4 mmol kg-1), and birnessite (pH < 7, up to 0.1 mmol kg-1). Combined sorption and transformation were the greatest for hematite and the lowest for birnessite. Sorption to hematite was more reversible than to goethite. Each desorption from goethite recovered <10% of sorbed monensin, whereas desorption from hematite recovered up to 69% of sorbed monensin, dependent on the solution. The potential for iron and manganese (hydr)oxides to abiotically transform monensin through reductive dissolution to partial oxidation products was evaluated by mass spectral analysis following sorption experiments. Additionally, the dominant sorption mechanism was inferred through ATR-FTIR spectroscopy, via examination of the carboxylate peak separation differences, on goethite and hematite to be bridging bidentate.


Assuntos
Modelos Químicos , Monensin/química , Adsorção , Animais , Bovinos , Compostos Férricos , Concentração de Íons de Hidrogênio , Ferro/química , Compostos de Ferro , Manganês , Compostos de Manganês/química , Minerais , Óxidos/química , Solo
12.
Ecotoxicol Environ Saf ; 196: 110561, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32276163

RESUMO

A ternary catalysis system was investigated to evaluate the comparative degradation of toxic fungicide metabolite 3,5-dichloroaniline (3,5-DCA) by laccase and MnO2 with mediators. In this study, copper based fungal enzyme laccase (Trametes versicolor origin) and metal catalyst MnO2 with various combinations of phenolic mediators (catechol, syringaldehyde, syringic acid, caffeic acid and gallic acid) were monitored to optimize and screen the better one for 3,5-DCA degradation assay. Catechol showed better potentiality in reduction of 3,5-DCA among the studied mediators. Catechol (2mM) showed the highest reduction rate (99-100%) followed by syringaldehyde (40.51%) with 2U/mL of laccase at 25 °C within 24 h reaction time. Similarly, complete degradation of 3,5-DCA was obtained by catechol (2mM) with 2 mg/mL of MnO2 in MnO2-mediator assay. The notable finding of current study indicated the triggering of catechol for better 3,5-DCA degradation at higher pH condition but inertness in laccase-mediator assay due to laccase destabilization. The reaction pathways of optimized mediator-based catalysis for laccase and MnO2 were proposed. Finally, the optimized laccase-catechol based degradation was considered as a pioneer green catalysis approach to reduce the toxic metabolite 3,5-DCA concentrations in aqueous medium as compared to MnO2-catechol catalysis.


Assuntos
Compostos de Anilina/análise , Fungicidas Industriais/análise , Lacase/metabolismo , Compostos de Manganês/química , Óxidos/química , Trametes/enzimologia , Compostos de Anilina/metabolismo , Benzaldeídos/química , Catálise , Catecóis/química , Fungicidas Industriais/metabolismo , Fenóis/química
13.
Food Chem ; 322: 126719, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32283377

RESUMO

In this study, a sensitive immunoassay using immunomagnetic nanobeads (MNBs), manganese dioxide nanoflowers (MnO2 NFs) and quantum dots (QDs) was developed for simultaneous detection of E. coli O157: H7 and Salmonella typhimurium. MnO2 NFs were synthesized, functionalized and incubated with QDs to obtain QDs@MnO2 nanocomposites, followed by modification with antibodies (pAbs) to obtain pAb-QDs@MnO2 nanocomposites (QM NCs). Target bacteria were first conjugated with MNBs and QM NCs to form MNB-bacteria-QM complexes. Then, QDs were quickly released from the complexes using glutathione to reduce MnO2 to Mn2+. Finally, fluorescent intensity at characteristic wavelength was measured by optical detector to determine target bacteria. This immunoassay could simultaneously and quantitatively detect E. coli from 1.5 × 101 to 1.5 × 106 CFU/mL with detection limit of 15 CFU/mL and Salmonella from 4.0 × 101 to 4.0 × 106 CFU/mL with detection limit of 40 CFU/mL in 2 h. The mean recovery for both bacteria in spiked chicken samples was ∼96%.


Assuntos
Escherichia coli O157/isolamento & purificação , Imunoensaio/métodos , Compostos de Manganês/química , Óxidos/química , Pontos Quânticos/química , Salmonella typhimurium/isolamento & purificação , Escherichia coli O157/crescimento & desenvolvimento , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Imunoensaio/instrumentação , Limite de Detecção , Salmonella typhimurium/crescimento & desenvolvimento
14.
Chemosphere ; 253: 126595, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32278904

RESUMO

The α-MnO2, ß-MnO2 and γ-MnO2 samples were prepared by the hydrothermal method and were used for the degradation of ciprofloxacin (CIP) wastewater in a combined DBD-catalytic process. The physical and chemical properties of the samples were systematically studied by several analytical techniques including BET, XRD, SEM, HRTEM, XPS, and H2-TPR. The combination of DBD with α-MnO2 showed the highest CIP degradation efficiency, and the efficiency could reach 93.1% after 50 min, which was 10.8% and 18.1% higher, respectively, than those of ß-MnO2 and γ-MnO2 catalysts in the plasma-catalytic system. According to the model of response surface methodology, the contribution of key experimental parameters on the CIP degradation decreased in the order: peak voltage > air flow rate > initial concentration > initial pH. The optimum operating parameters were peak voltage 17 kV, air flow rate 2.5 L min-1, an initial concentration 5 mg L-1 and an initial pH 6.9. The quenching experiments of active species showed that OH and O2- were critical to the CIP degradation. The generated O3 might be adsorbed by the α-MnO2 catalyst and resulted in more OH generation. The intermediate products of CIP degradation in DBD+α-MnO2 system were analyzed by LC-MS, and three possible degradation pathways were proposed. This research provides an insight into the use of the crystallographic structures in discharge plasma system for antibiotics in water.


Assuntos
Ciprofloxacino/química , Poluentes Químicos da Água/química , Adsorção , Antibacterianos , Catálise , Compostos de Manganês/química , Nanopartículas , Óxidos/química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos
15.
Phys Chem Chem Phys ; 22(14): 7537-7545, 2020 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-32219231

RESUMO

Understanding how electrons and protons move in a coupled manner and affect one another is important to the design of proton-electron conductors and achieving biological transport in synthetic materials. In this study, a new methodology is proposed that allows for the quantification of the degree of coupling between electrons and protons in tyrosine-rich peptides and metal oxide hybrid films at room temperature under a voltage bias. This approach is developed according to the Onsager principle, which has been thoroughly established for the investigation of mixed ion-electron conductors with electron and oxide ion vacancies as carriers at high temperatures. Herein, a new device platform using electron-blocking electrodes provides a new strategy to investigate the coupling of protons and electrons in bulk materials beyond the molecular level investigation of coupled proton and electron transfer. Two Onsager transport parameters, αi* and σe', are obtained from the device, and the results of these transport parameters demonstrate that the coupled transport of electrons and protons inside the hybrid film plays an important role in the macroscopic-scale conduction. The results suggest that an average of one electron is dragged by one proton in the absence of a direct driving force for electron movement ∇ηe.


Assuntos
Técnicas de Química Analítica/instrumentação , Transporte de Elétrons/fisiologia , Elétrons , Compostos de Manganês/química , Óxidos/química , Peptídeos/química , Prótons , Transporte Biológico/fisiologia
16.
Chemosphere ; 250: 126329, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32126334

RESUMO

The increasing contamination of lead ions (Pb(II)) in groundwater has become a serious environmental issue, which provides the impetus for intense research on Pb(II) removal. ε-MnO2 nanoflowers were successfully fabricated through a simple decomposition reaction. And the obtained ε-MnO2 nanoflowers were employed to remove Pb(II) from water. The detailed microstructure and surface properties of ε-MnO2 were systematically characterized. The results indicate that the pure ε-MnO2 phase was obtained and the specific surface area is 96.33 m2 g-1. Batch adsorption experiments of Pb(II) were carried out, and the ε-MnO2 nanoflowers exhibited outstanding adsorption performance. The maximum adsorption capacity for Pb(II) and Cd(II) achieved to 239.7 mg g-1 and 73.6 mg g-1 at the dosage of 0.2 g L-1. Besides, the prepared ε-MnO2 nanoflowers show much higher removal efficiency toward Pb(II) compared with commercial MnO2. The XRD results reveal the stability of ε-MnO2 nanoflowers, and the XPS results suggest that both the electrostatic interaction and structural tunnels are responsible for the removal mechanisms of Pb(II). This work finds a facile method to synthesize ε-MnO2 nanoflowers, showing great potential for Pb(II) removal.


Assuntos
Chumbo/química , Compostos de Manganês/química , Nanoestruturas/química , Óxidos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Água Subterrânea , Íons , Propriedades de Superfície , Águas Residuárias/química , Água , Poluentes Químicos da Água/análise
17.
Chemosphere ; 250: 126251, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32113100

RESUMO

Sorption onto clays (montmorillonite and kaolinite), oxidation and sorption by manganese oxides (synthesized MnO and natural MnO), and coupled sorption-oxidation experiments were conducted for the removal of antibiotics sulfadiazine (SDZ) and ciprofloxacin (CIP) at pH 5 and 8. Individual sorption and oxidation modelling were carried out using the first-order kinetic model. A coupled sorption-oxidation kinetic model was developed to predict the simultaneous sorption and oxidation process. The coupled sorption-oxidation enhanced the antibiotic sorption, with the first-order sorption rate constants in the simultaneous presence of clays and manganese oxides (ksorp) being higher than those with clays only (ksorp0). In contrast, a depression was observed; the first-order oxidation and sorption combination rate constants in the simultaneous presence of manganese oxides and clays (kMnO) were lower than those with manganese oxides only (kMnO0). In the coupled sorption-oxidation reaction, 13.5-62.5% of SDZ and CIP removal was attributed to the sorption. The SDZ and CIP species distributions at pH 5 affected the coupled sorption and oxidation systems more than those at pH 8. The best removal efficiency was achieved by the montmorillonite-synthesized MnO combination, mainly due to the higher surface area (ABET) and pore size of montmorillonite and synthesized MnO combination compared to other clays and manganese oxides combinations.


Assuntos
Ciprofloxacino/química , Compostos de Manganês/química , Modelos Químicos , Óxidos/química , Sulfadiazina/química , Adsorção , Antibacterianos/química , Bentonita , Argila/química , Recuperação e Remediação Ambiental/métodos , Caulim , Cinética , Manganês , Oxirredução
18.
Inorg Chem ; 59(7): 4909-4923, 2020 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-32162905

RESUMO

Photodynamic therapy (PDT) is commonly employed in clinics to treat the cancer, but because of the hypoxic tumor microenvironment prevalent inside tumors, PDT therapeutic efficiency is not adequate hence limiting the effectiveness of PDT. Therefore, we designed a nanocomposite consisting of reduced nanographene oxide (rGO) modified with polyethylene glycol (PEG), manganese dioxide (MnO2), upconversion nanoparticles (UCNPs), and Chlorin e6 (Ce6) to spark oxygen production from H2O2 with the aim of relieving the tumor hypoxic microenvironments. For in vivo tumor PDT and photothermal therapy (PTT), UCNPs-Ce6-labeled rGO-MnO2-PEG nanocomposites were used as a therapeutic agent, augmenting the therapeutic efficiency of PDT via redox progression through the catalytic H2O2 decomposition pathway and further achieving excellent tumor inhibition. It is important to mention that degradation of MnO2 in an acidic cellular microenvironment leads to the creation of a massive volume of Mn2+ which was employed as a contrast mediator for magnetic resonance imaging (MRI). Our research postulates an approach to spark O2 formation through an internal stimulus to augment the efficiency of MRI- and computerized tomography (CT)-imaging-guided PDT and PTT.


Assuntos
Antineoplásicos/uso terapêutico , Nanocompostos/uso terapêutico , Nanopartículas/uso terapêutico , Neoplasias/tratamento farmacológico , Fármacos Fotossensibilizantes/uso terapêutico , Porfirinas/uso terapêutico , Animais , Antineoplásicos/química , Linhagem Celular Tumoral , Feminino , Fluoretos/química , Fluoretos/efeitos da radiação , Fluoretos/uso terapêutico , Gadolínio/química , Gadolínio/efeitos da radiação , Gadolínio/uso terapêutico , Grafite/química , Grafite/uso terapêutico , Humanos , Raios Infravermelhos , Compostos de Manganês/química , Compostos de Manganês/uso terapêutico , Camundongos , Nanocompostos/química , Nanopartículas/química , Óxidos/química , Óxidos/uso terapêutico , Oxigênio/metabolismo , Fotoquimioterapia/métodos , Fármacos Fotossensibilizantes/química , Polietilenoglicóis/química , Polietilenoglicóis/uso terapêutico , Porfirinas/química , Porfirinas/efeitos da radiação , Microambiente Tumoral/fisiologia , Ensaios Antitumorais Modelo de Xenoenxerto
19.
Ecotoxicol Environ Saf ; 192: 110326, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32066004

RESUMO

Adsorption represents an attractive mean to remediate polluted water. Unfortunately, the surface positive charges, low surface area and complicated separation procedures inhibit the usability of poly (m-phenylenediamine) (PmPD) as an adsorbent for heavy metal removing. To overcome these drawbacks, a magnetic MnO2@Fe3O4/PmPD core-shell adsorbent was designed to remove heavy metals from water. The MnO2 shell, came from the redox reaction between KMnO4 and PmPD, increased the surface area and changed the surface electronegativity. MnO2@Fe3O4/PmPD could be easily separated from water. It showed a significant increase in heavy metals removal efficiency, with maximum capacities of 438.6 mg/g for Pb(II) and 121.5 mg/g for Cd(II), respectively. The affinity between heavy metals and MnO2@Fe3O4/PmPD were mainly due to electrostatic attraction, ion exchanges and coordinated interaction. Density functional theory (DFT) calculations further confirmed that Pb and Cd were bonded with O atoms. The calculated adsorption energy indicated that the (111) MnO2 facet presented stronger adsorption affinity toward Pb(II) than Cd(II). Additionally, FM150 (150 mg) could regenerate 22 L Pb(II) wastewater upon single passage through the filterable column with a flux of 20 mL/min. Thus, the present work demonstrates the promising potential of using MnO2@Fe3O4/PmPD for efficiently removing heavy metals from wastewater.


Assuntos
Óxido Ferroso-Férrico/química , Compostos de Manganês/química , Metais Pesados/química , Óxidos/química , Fenilenodiaminas/química , Águas Residuárias/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Troca Iônica , Fenômenos Magnéticos , Eletricidade Estática
20.
Ecotoxicol Environ Saf ; 191: 110234, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-32006869

RESUMO

Imidacloprid is a widely used neonicotinoid insecticide worldwide, and has attracted great concerns due to its potential threat to human and environment. Much effort was thus spent on developing the effective way for removing imidacloprid from water, but might also produce various degradation products with unknown risks. The hypothesis was then proposed that permanganate oxidation was probably the appropriate tool for eliminating imidacloprid and its toxicity through selective oxidation of specific groups. To that end, we studied the kinetics of permanganate/imidacloprid reaction by considering the effects of pH (5.0-9.0), temperature (15-35 °C), ionization strength (0.05-0.20 M), typical anions (Cl-, Br-, I-) and humic acid. Based on the identified products from mass spectrometer, the main reaction pathway was found to be the hydroxylation of C-H bond at imidazole ring, leading to the decreased toxicity evaluated by ECOSAR program. Our results demonstrate that permanganate oxidation should be a very promising technique for controlling imidacloprid contamination by effective detoxification through highly selective partial oxidation. Moreover, this study has also paved the way toward applying permanganate oxidation for in situ chemical remediation of imidacloprid, though the corresponding standards need to be established in advance.


Assuntos
Inseticidas/análise , Compostos de Manganês/química , Neonicotinoides/análise , Nitrocompostos/análise , Óxidos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Substâncias Húmicas/análise , Inseticidas/química , Cinética , Modelos Teóricos , Neonicotinoides/química , Nitrocompostos/química , Oxirredução , Poluentes Químicos da Água/química
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