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1.
Chemosphere ; 240: 124940, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31574446

RESUMO

Charged ultrafiltration (UF) membranes can repel electrically charged molecules that are smaller than the size of the membrane pores and display high rejection of solutes, high flux, and low operation pressures compared to uncharged UF, nanofiltration (NF) and reverse osmosis (RO). Here, a charged UF membrane composite (PANI/PVDF) was prepared and regulated via electrochemically reversible control in portions of amine/imine functional groups of PANI. As a result, the permeability and rejection ratios of CR2- on charged PANI/PVDF, with PVDF as a control, increased from 19.6 to a maximum of 183.3 L m-2 h-1 bar-1 and from 3.4% to 74%, which expands the trade-off confine benefited from surface potential change from -12.21 mV to -25.26 mV, furtherly, the rejection ratio of CR2- on PANI/PVDF reached up to 93% via the electrochemical regulation. Finally, a fixed-charge model was built that well describes the steric and electric repulsion effects on membrane performance and the important roles of the electrochemically controllable surface charge. Moreover, the contour map of rejection ratios containing the ratio of molecular size vs the average pore size of the membrane (r/R = 0.2-1.0) and the zeta potential (-10 to -60 mV) were taken into account, which can be used to visually understand the rejection performance of membranes. This model is also appropriate for varying molecular sizes and for molecules with different charges. Our work opens a new horizon for the design of electrochemically controllable charged membranes to remove charged compounds.


Assuntos
Corantes/análise , Técnicas Eletroquímicas/métodos , Ultrafiltração/métodos , Purificação da Água/métodos , Eletricidade , Membranas Artificiais , Propriedades de Superfície
2.
Front Chem ; 7: 743, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31803713

RESUMO

Planar-chiral pillar[5]arenes bearing ß-D-galactose substituents on both rims have been successfully synthesized and effectively separated by silica gel chromatography with a high yield. The obtained (S p )- and (R p )-ß-D-galactose functionalized pillar[5]arenes [(S p-D )-GP5 and (R p-D )-GP5] exhibit the S p and R p planar chirality. Furthermore, (S p-D )-GP5 and (R p-D )-GP5 can not racemize according to dynamic 1H NMR and CD spectra. Notably, GP5 is able to capture a guest molecule (DNS-CPT) to form a host-guest supramolecular amphiphile, which can further self-assemble into chiral nanoparticles with the S p and R p planar chirality of (S p-D )-GP5 and (R p-D )-GP5 still being retained, suggesting GP5 could be as reliable chiral sources to transfer the S p and R p planar chirality.

3.
Environ Sci Technol ; 52(21): 12602-12611, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30351032

RESUMO

The simultaneous reduction and sequestration of Cr(VI) from wastewater is desirable as a cost-effective and environmentally friendly approach. In this study, we execute a one-step facile synthesis strategy on polyaniline (PANI) composites based on aniline adsorption and polymerization on pores of millimeter-scale polystyrene balls (PANI@PS). The well-defined PANI@PS increased the removal capacity of Cr(VI) by 5.4 times, going from 43.6 (bulky PANI) to 233.7 mg g-1 near neutral pH (6.0) instead of the pH 1-3 documented in other reports, which was higher than that of many reported adsorbents due to its porous structure, numerous interaction sites, and confinement effects in the polymer. Most importantly, PANI@PS could efficiently sequester positive Cr(III) after reducing Cr(VI) to Cr(III) due to its negative surface created by confinement effects confined to the nanopores of PS. Conversely, positively charged bulky PANI repelled electrostatically positive Cr(III); thus, additional precipitation or adsorption treatments were needed in practical applications. Moreover, a coating of PANI can protect PS, as a substrate and a composite, from irreversible damage due to the strong oxidation capacity of Cr(VI), which is another major concern in adsorbing strong oxidants using polymers. A novel strategy to regenerate the exhausted PANI@PS was efficiently executed based on the electrochemical redox reversibility of PANI. Finally, the comprehensive adsorption/reduction/sequestration of Cr on PANI@PS was elucidated in detail.


Assuntos
Poliestirenos , Poluentes Químicos da Água , Adsorção , Compostos de Anilina , Cromo
4.
Biosens Bioelectron ; 86: 129-134, 2016 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-27344608

RESUMO

The hollow-spherical Co/N-C nanoparticle, which is synthesized via a simple hydrothermal reaction followed by heat treatment, is firstly used as electrocatalyst for oxygen reduction reaction (ORR) in air-cathode microbial fuel cell (MFC). The maximum power density of MFC with 10% Co/N-C air-cathode is as high as 2514±59mWm(-2), which is almost 174% higher than the control. The exchange current density (i0) of cathode equipped with 10% Co/N-C is 238% higher than that of untreated AC. While the total resistance of treated samples decreases from 13.017 to 10.255Ω. The intensity ratio of Raman D to G band (ID/IG) decreases from 0.93 (N-C) to 0.73 (Co/N-C), indicating the catalyst forms graphite structure. Both XRD and XPS testify that Co is bonded to N within graphitic sheets and serves as the active sites in ORR. The four-electron pathway of the Co/N-C also plays a crucial role in electrochemical catalytic activity. As a result, it can be expected that the as-synthesized Co/N-C, with extraordinary electro-catalytic performance towards ORR, will be a promising alternative to the state-of-the-art non-precious metal ORR electro-catalysts for electrochemical energy applications.


Assuntos
Fontes de Energia Bioelétrica/microbiologia , Cobalto/química , Eletrodos , Nanosferas/química , Nanotubos de Carbono/química , Nitrogênio/química , Catálise , Transferência de Energia , Desenho de Equipamento , Análise de Falha de Equipamento , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Nanoporos/ultraestrutura , Nanosferas/ultraestrutura , Nanotubos de Carbono/ultraestrutura , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Esgotos/microbiologia
5.
Bioresour Technol ; 206: 285-289, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26898678

RESUMO

In order to improve the performance of microbial fuel cell (MFC), iron-nitrogen-activated carbon (Fe-N-C) as an excellent oxygen reduction reaction (ORR) catalyst was prepared here using commercial activated carbon (AC) as matrix and employed in single chamber MFC. In MFC, the maximum power density increased to 2437±55 mW m(-2), which was 2 times of that with AC. The open circuit potential (OCP) of Fe-N-C cathode (0.47) was much higher than that of AC cathode (0.21 V). The R0 of Fe-N-C decreased by 47% from 14.36 Ω (AC) to 7.6 Ω (Fe-N-C). From X-ray photoelectron spectroscopy (XPS), pyridinic nitrogen, quaternary nitrogen and iron species were present, which played an important role in the ORR performance of Fe-N-C. These results demonstrated that the as-prepared Fe-N-C material provided a potential alternative to Pt in AC air cathode MFC for relatively desirable energy generation and wastewater treatment.


Assuntos
Fontes de Energia Bioelétrica , Carvão Vegetal/química , Ferro/química , Nitrogênio/química , Ar , Catálise , Eletroquímica , Eletrodos , Espectroscopia Fotoeletrônica , Propriedades de Superfície
6.
Biosens Bioelectron ; 74: 989-95, 2015 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-26264265

RESUMO

Cathodic catalyst is one of the key materials in microbial fuel cell (MFC). The addition of non-stoichiometric nano Fe3O4 in activated carbon (NSFe3O4/AC) air cathode was beneficial to boosting the charge transfer of the cathode accompanying with the enhancement of power performance in MFC. The air cathode modified by NSFe3O4 (5%, Wt%) increased the maximum power density by 83.3% from 780 mW/m(2) to 1430 mW/m(2) compared with bare air cathode. The modified cathodes showed enhanced electrochemical properties and appeared the maximum exchange current density of 18.71×10(-4) A/cm(2) for oxygen reduction reaction. The mechanism of oxygen reduction for the NSFe3O4/AC catalyst was a 4-electron pathway. The oxygen vacancy of the NSFe3O4 played a crucial role in electrochemical catalytic activity. The great catalytic performance made NSFe3O4 have a promising outlook applied in MFC.


Assuntos
Fontes de Energia Bioelétrica/microbiologia , Carbono/química , Eletrodos/microbiologia , Nanopartículas de Magnetita/química , Ar , Catálise , Condutividade Elétrica , Transporte de Elétrons , Transferência de Energia , Nanopartículas de Magnetita/ultraestrutura
7.
Bioresour Technol ; 195: 154-61, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26122090

RESUMO

Three kinds of three-dimensional (3D) CuxO catalysts were prepared to modify activated carbon air-cathode using a facile electrochemical method with addition of surfactants. The maximum power density of MFC using SC-Cu air cathode (added sodium citrate into the electrolyte solution in electrodeposition process) was 1550±47 mW m(-2), almost 77% higher than AC cathode. Specifically, the charge transfer resistance significantly decreased by 89% from 9.3980 Ω to 1.0640 Ω compared to the control. Lumphy and mutually embedded filmy sheet structure were observed in SEM, which provided sufficient active sites for oxygen adsorption and diffusion. In XRD and TEM result, CuxO with mixed facets showed special structure which had a better performance. Crystallization condition of electrodeposited materials played a significant role in their nature electrochemical properties, morphology controlled by surfactant of CuxO exhibited high properties on the air-cathode MFC.


Assuntos
Ar , Fontes de Energia Bioelétrica , Cobre/química , Óxidos/química , Eletricidade , Técnicas Eletroquímicas , Eletrodos , Oxigênio/análise , Termodinâmica
8.
Bioresour Technol ; 195: 180-7, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26112347

RESUMO

Commercial Co3O4 and ortho-hexagon spinel nano-Co3O4 (OHSNC) were doped in the AC at a different percentage (5%, 10% and 15%) to enhance the performance of microbial fuel cell (MFC). The maximum power density of MFC with 10% OHSNC doped cathode was 1500±14 mW m(-2), which was 97.36% and 41.24% higher than that with the bare AC air cathode and commercial Co3O4 respectively. The electrocatalytic behavior for their better performance was discussed in detail with the help of various structural and electrochemical techniques. The OHSNC was characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results showed that the improved performance owed to the enhancement of both kinetics activity and the number of electron transfer in the ORR, and the internal resistance was largely reduced. Therefore, OHSNC was proved to be an excellent cathodic catalyst in AC air cathode MFC.


Assuntos
Ar , Óxido de Alumínio/química , Fontes de Energia Bioelétrica , Carvão Vegetal/química , Cobalto/química , Óxido de Magnésio/química , Nanopartículas/química , Óxidos/química , Catálise , Eletricidade , Técnicas Eletroquímicas , Eletrodos , Cinética , Nitrogênio/química , Oxigênio/química
9.
Bioresour Technol ; 187: 299-304, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25863207

RESUMO

A novel n-type Cu2O doped activated carbon (AC) air cathode (Cu/AC) was developed as an alternative to Pt electrode for oxygen reduction in microbial fuel cells (MFCs). The maximum power density of MFCs using this novel air cathode was as high as 1390±76mWm(-2), almost 59% higher than the bare AC air cathode. Specifically, the resistance including total resistance and charge transfer resistance significantly decreased comparing to the control. Tafel curve also showed the faster electro-transfer kinetics of Cu/AC with exchange current density of 1.03×10(-3)Acm(-2), which was 69% higher than the control. Ribbon-like Cu2O was deposited on the surface of AC with the mesopore surface area increasing. Cubic Cu2O crystals exclusively expose (111) planes with the interplanar crystal spacing of 2.48Å, which was the dominate active sites for oxygen reduction reaction (ORR). N-type Cu2O with oxygen vacancies played crucial roles in electrochemical catalytic activity.


Assuntos
Fontes de Energia Bioelétrica/microbiologia , Carvão Vegetal/química , Cobre/química , Eletrodos/microbiologia , Ar , Catálise , Materiais Revestidos Biocompatíveis/síntese química , Impedância Elétrica , Transferência de Energia , Desenho de Equipamento , Análise de Falha de Equipamento
10.
Bioresour Technol ; 170: 379-384, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25151475

RESUMO

To observe the influence of P-doped activated carbon (AC) in air-cathode microbial fuel cells (MFCs), AC was treated with H3PO4 (1M) at 80°C and 400°C respectively, and then was used as catalyst layer in the air-cathode. The maximum power densities were: 1096±33mW/m(2) (SP2, AC treated at 400°C), 954±36mW/m(2) (SP1, AC treated at 80°C), which were 55%, 35% higher than the control (708±27mW/m(2), untreated AC), respectively. The results of electrochemical impedance spectroscopy (EIS) and the Brunauer-Emmett-Teller (BET) showed that the total resistance was decreased and the pore structure was changed. The analysis of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) demonstrated that P-doped functional group was produced in SP2, which caused the 15% greater power density than SP1 by increasing O2 adsorption. What is more important, the chemically modified method is simple and economical.


Assuntos
Fontes de Energia Bioelétrica , Carbono/química , Ácidos Fosfóricos/química , Catálise , Espectroscopia Dielétrica , Eletrodos , Temperatura Alta , Espectroscopia Fotoeletrônica , Espectroscopia de Infravermelho com Transformada de Fourier
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