Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 10 de 10
Filtrar
Mais filtros

Base de dados
Tipo de documento
Assunto da revista
País de afiliação
Intervalo de ano de publicação
1.
Ecotoxicol Environ Saf ; 268: 115691, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37979359

RESUMO

The slow rate of electron transfer and the large consumption of carbon sources are technical bottlenecks in the biological treatment of wastewater. Here, we first proposed to domesticate aerobic denitrifying bacteria (ADB) from heterotrophic to autotrophic by electricity (0.6 V) under zero organic carbon source conditions, to accelerate electron transfer and shorten hydraulic retention time (HRT) while increasing the biodegradation rate. Then we investigated the extracellular electron transfer (EET) mechanism mediated by this process, and additionally examined the integrated nitrogen removal efficiency of this system with composite pollution. It was demonstrated that compared with the traditional membrane bioreactor (MBR), the BEC displayed higher nitrogen removal efficiency. Especially at C/N = 0, the BEC exhibited a NO3--N removal rate of 95.42 ± 2.71 % for 4 h, which was about 6.5 times higher than that of the MBR. Under the compound pollution condition, the BEC still maintained high NO3--N and tetracycline removal (94.52 ± 2.01 % and 91.50 ± 0.001 %), greatly superior to the MBR (10.64 ± 2.01 % and 12.00 ± 0.019 %). In addition, in-situ electrochemical tests showed that the nitrate in the BEC could be directly converted to N2 by reduction using electrons from the cathode, which was successfully demonstrated as a terminal electron acceptor.


Assuntos
Desnitrificação , Elétrons , Carbono , Processos Heterotróficos , Processos Autotróficos , Nitratos , Nitrogênio/metabolismo , Reatores Biológicos
2.
J Environ Manage ; 323: 116256, 2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-36126592

RESUMO

Defects and vacancies are the essential reasons for the removal of heavy metal ions from wastewater by low-cost biochar materials. This study aimed to use chemically activated hemp stem core alkali extraction residue biochar as an adsorbent to remove nickel (Ni) and copper (Cu) ions from the simulated waste liquid. A large number of defects and vacancies were introduced into the pyrolysis process to study the efficient removal of heavy metal ions Cu and Ni by hemp rod biomass carbon material (HSR-BC) with different carbon base mass ratios and temperatures. The specific surface area of the prepared hemp rod active biochar was highly correlated with the aperture and carbon base ratio and temperature, and reached the maximum value (1429 m2/g) at 600 °C with the ratio of carbon to base (1:3.5). The removal rates of heavy metals Ni(II) and Cu(II) were as high as 94.25% and 99.54%, respectively, and the adsorption capacities were up to 7.85 mg/g and 24.88 mg/g. The adsorption isotherm follows the Langmuir equation and chemo-adsorption was the main adsorption process. Comparing the surface defects and vacancies of biochar materials before and after adsorption showed that the defects of sp-C and oxygen vacancies produced on the edge of the carbon were the main active sites of the biochar material, an amount of carbon defects would become an anchor site for the Lewis acidic groups, the defective acid site strengthened the electron transfer between the functional group and the Ni(II)/Cu(II), promoted the strong cooperation of Ni(II)/Cu(II) ions with -COOH group to enable efficient and rapid adsorption removal. In addition, a large number of carbon-deficient structures could quickly anchor the Ni(II)/Cu(II) due to their local electron deficiency state, which was difficult to desorb. This study provided an in-depth understanding and guidance for the development of low-cost biochar materials with excellent removal performance of heavy metal ions.


Assuntos
Cannabis , Metais Pesados , Poluentes Químicos da Água , Adsorção , Álcalis , Carbono , Carvão Vegetal , Cobre , Íons , Cinética , Metais Pesados/química , Níquel , Oxigênio , Águas Residuárias , Poluentes Químicos da Água/química
3.
J Environ Manage ; 287: 112294, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33714046

RESUMO

A novel heteroatomic N, P and S co-doped core-shell material (MnFe3O4@PZS) was synthesized by a simple polycondensation hydro-thermal method, and used as the cathode to cooperate with electron-catalysis to activate persulfate (S2O82-) (E-MnFe3O4@PZS-PDS) for tetracycline (TTC) degradation. Radical scavenger studies demonstrated that non-radicals including atomic H* and singlet oxygen (1O2) rather than sulfate and hydroxyl radicals were the crucial reactive oxygen species (ROS). Electrochemical analysis indicated that Mn doping could promote electro-catalytic process via diverting pathway from four/two-electron to one-electron to generate non-radical H*/1O2 at the cathode, including one-electron oxygen reduction reaction (1e-ORR) (O2→1O2), and one-electron hydrogen reduction reaction (1e-HRR) (H2O+e-→H∗), as evidenced by the lowest onset potential (0.072 V) together with electron transfer number (n = 1.65). Besides, the regeneration/reduction of FeⅡ/Ⅲ/MnⅡ/Ⅲ/Ⅳ and persulfate will not cause excessive consumption of electron and chemicals due to that could directly get the electron individually from the cathode and anode, and finally TTC could be completely degraded with low energy consumption (0.655 kWh m-3). This study provides new insights into the direct single electron activating PDS to produce non-radical H*/1O2 via core-shell catalytic MnFe3O4@PZS, and displays a promising application in wastewater treatment.


Assuntos
Elétrons , Purificação da Água , Catálise , Eletrodos , Oxirredução , Tetraciclina
4.
Chemosphere ; 352: 141296, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38296214

RESUMO

It is feasible to improve the photodegradation efficiency of organic pollutants by metal-organic frameworks (MOF)-based semiconductors via ligand engineering. In this work, three (Fe/Co)-XBDC-based MOFs were synthesized by introducing different ortho-functional groups X (X = -H, -NO2, -NH2) next to the carboxyl group of the organic ligand (i.e., terephthalic acid). The analysis focused on the influence mechanism of the adjacent functional group effect of the ligand on the physicochemical properties of the material and the actual photodegradation activity of TC. Multiple pieces of evidences suggested that the differences in electron-induced and photocharge-transfer mechanisms of the above ortho functional groups affect the crystal morphology and photocatalytic activity of FeCo-MOF during pyrolysis. Interestingly, (Fe/Co)-NH2BDC exhibited the highest photocatalytic activity under neutral conditions. The results of density functional theory show that the introduction of a strong donor-NH2 group can enhance light absorption and act as an "electron pump" to supply electrons to the iron center, accelerating the separation and efficient transport of photogenerated carriers on the ligand-metal bridge. In conclusion, this study is a proposal for a strategy of structural regulation for the enhancement of the catalytic activity of (Fe/Co)-MOFs in the photodegradation of TC.


Assuntos
Compostos Heterocíclicos , Estruturas Metalorgânicas , Ligantes , Tetraciclina , Antibacterianos , Elétrons
5.
J Hazard Mater ; 466: 133624, 2024 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-38295726

RESUMO

The generation, migration and reaction paths of electrons are the key steps for photodegradation of pollutants. However, efficient operation of the above pathways is still challenging. Herein, by strong coordination and slow pyrolysis, we constructed a narrow band Zn-Mn bimetallic photoactive core-shell material (Mn@Zn-N-C, Eg = 3.38 eV) with abundant oxygen vacancies for enhancing the above electronic paths. The photodegradation experiments of tetracycline hydrochloride (TCH) showed that the formation and transfer of vacancy-induced free electrons in the synthesized Mn@Zn-N-C was the key to improve the photocatalytic activity. The DFT calculation results revealed that the photogenerated electrons can transfer along the Mn-O-Zn bridge in Mn@Zn-N-C, and promote the formation of MnIV, which directly capture the free electrons and reset itself to MnII site. In this case, the introduction of Mn would enhance the separation of h+ and e-. The adjacent vacancies and defects then also trapped the above free electrons and hinder the recombination of photogenerated carriers. Simultaneously, the localized valence electron transfer between the above redox pairs (Mn4+/Mn2+ and Zn2+/Zn0) also promoted the long-term stability of the photocatalytic process. In summary, using vacancy induction strategy to regulate the evolution of valence- and free-electrons is a promising method to improve the production-transfer-utilization efficiency of photogenerated carriers.

6.
Environ Pollut ; 336: 122449, 2023 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-37633439

RESUMO

Although alkaline sulfite activation of ferrate (Fe(VI)) has advantages of fast response and high activity for degradation of organic contaminants, the specific production pathways of active species and the pH conditions still hinder its widespread application. Based on this, our study constructed a novel advanced oxidation process of calcium sulfite (CaSO3) could activated Fe(VI) continuously by Ca2+ buffering and investigated the mechanism under different pH values and CaSO3 dosages with ciprofloxacin as a target organic pollutant. The results showed that Ca2+ stabilized the process at a neutral/weakly alkaline microenvironment of pH 7-8, which could alleviate the hydrolysis of ≡FeIV=O by protons and iron hydroxyl groups. Besides, the removal of pollutants occurred efficiently when sulfate (SO32-) was excessive and had a 3:1 ratio of SO32- to Fe(VI), achieving more than 99% removal of electron-rich phenolic organic pollutants within 2 min. By adding different radical scavengers and combining electrochemical analysis methods and electron paramagnetic resonance spectroscopy techniques to revealed that the main active species in Fe(VI)/CaSO3 process were ≡FeIV=O/≡FeV=O. Furthermore, the reactivity of various sulfate species (such as SO32-, SO3•-, SO4•-, SO5•-) with Fe(VI) was calculated using density functional theory (DFT), and it was found that Fe(VI)-SO32- reaction has a much lower energy barrier (-36.08 kcal/mol), indicating that SO32- can readily activate Fe(VI) and generate ≡FeIV=O to attack the atoms with high Fukui index (f -) in organic pollutants. The above results confirm the feasibility of Fe(VI)/CaSO3 process. Thus, this study can theoretically and practically prove that the main active species is ≡FeIV=O, rather than SO4•- or •OH in Fe(VI)/CaSO3 process.


Assuntos
Cálcio , Poluentes Químicos da Água , Poluentes Químicos da Água/análise , Ferro/química , Oxirredução , Sulfitos , Óxidos de Enxofre , Sulfatos
7.
Int J Biol Macromol ; 237: 124121, 2023 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-36966858

RESUMO

A scheme combining alkali­oxygen cooking and ultrasonic etching cleaning was developed for the short range preparation of CNF from bagasse pith, which has a soft tissue structure and is rich in parenchyma cells. This scheme expands the utilization path of sugar waste sucrose pulp. The effect of NaOH, O2, macromolecular carbohydrates, and lignin on subsequent ultrasonic etching was analyzed, and it was found that the degree of alkali­oxygen cooking was positively correlated with the difficulty of subsequent ultrasonic etching. The mechanism of ultrasonic nano-crystallization was found to be the bidirectional etching mode from the edge and surface cracks of the cell fragments by ultrasonic microjet in the microtopography of CNF. The optimum preparation scheme was obtained under the condition of 28 % NaOH content and 0.5 MPa O2, which solves the problem of low-value utilization of bagasse pith and environmental pollution, providing a new possibility for the source of CNF.


Assuntos
Álcalis , Oxigênio , Oxigênio/química , Álcalis/química , Hidróxido de Sódio/química , Ultrassom , Celulose/química , Carboidratos , Culinária
8.
Wideochir Inne Tech Maloinwazyjne ; 17(2): 289-298, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35707337

RESUMO

Introduction: Peripherally inserted central catheters (PICC) are a type of deep venipuncture, for which the catheter tip malposition rate is high. Aim: To examine the feasibility of preventing catheter tip malposition during PICC placement using an ultrasound-guided finger-pressure method to block the internal jugular vein. Material and methods: We conducted a double-blinded randomized controlled trial (RCT) at a tertiary public hospital in Hubei province, China. A total of 600 patients were recruited and randomly allocated to the ultrasound-guided finger compression method (UGFCM) and traditional partial head method (TPHM) group (n = 300/group). Incidence of catheter tip malposition was assessed as the primary outcome of the study. A systematic literature review and meta-analysis was performed. We searched MEDLINE, EMBASE, Cochrane Library, China-National Knowledge Infrastructure, and Chinese Biomedicine Database and performed publication bias and sensitivity analyses on 10 extracted studies. Results: There were no significant differences in baseline demographic and clinical characteristics between the two groups (p > 0.05). Overall incidence of catheter tip malposition was significantly lower in the UGFCM and TPHM group (1.67% vs. 10.3%) and particularly the incidence of malposition in the internal jugular vein (1% vs. 9%). In the meta-analysis of 10 eligible studies, with 1263 cases using the UGFCM method while 1261 adopted the TPHM method, the results showed that the incidence of catheter tip malposition was significantly lower in the group using the UGFCM method (OR = 0.17, 95% CI: 0.11-0.27, p < 0.01), which is in line with the results of our RCT study. Conclusions: This study may add valuable evidence on adopting the finger-pressure method for blocking neck veins to reduce the incidence of catheter tip malposition, particularly in the internal jugular vein.

9.
J Hazard Mater ; 426: 127794, 2022 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-34810007

RESUMO

As an alternative to noble-metal Pt based catalysts, metal-based single atomic catalytic (SACs) exhibited excellent atom efficiency and catalytic activity via exposing abundant single atomic active centers. Here, we synthesized the monatomic Mn ligands anchored on porous N, P, S- co-doped carbon framework (Mn content over 4.5 wt%) (denoted as Mn-SAC@PZS). The single atomic Mn exhibited super mass activity (11.58 m2 g-1) and kinetic current (1.122×103 µA) with a much lower Tafel slope (4.25 mV dec-1) at 0.792 V (vs. SCE). XANES and EXAFS revealed that the mononuclear Mn were inclined to coordinate with N and S rather than P to form the R space of Mn, in which the first coordination shells backscattered with Mn-N and Mn-S. RRDE revealed that one-electron ORR pathway (72 ~ 100%) dominated at the potential of 0.5 ~ 0.7 V, oxygen molecule was absorbed/activated on site Mn* to form O* intermediate, then further activated to 1O2 via one-electron ORR pathway, while H* was electro activated by non-metallic active sites (i.e. pyri-N, sp-N, -PN and SO). In addition, the Mn-SAC@PZS was capable of highly selectively capturing and effectively degrading CIP in the presence of HA. Fast and complete removal of CIP was achieved within 30 min in the Mn-SAC@PZS-EFLP system, and the apparent rate constant (k) was up to 0.25 min-1. The energy consumption value was 0.453 kWh m-3, much lower than non-single atomic catalyst MnxOy@PZS (0.655 kWh m-3), which was comparable with the state-of-the-art advanced oxidation processes. These findings provided new insights into the maximum release of the atomic activity of the catalyst, and provides a possible way to selectively remove aromatics from multiple pollutants in complex water system.

10.
Chemosphere ; 239: 124743, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31514007

RESUMO

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. In this study, with the same doping level of Co and N, MoO2 and ZIF-67 were used as precursors to prepare MoO2@Co/N and FeC@Co/N electrocatalysts for the modified graphite felt cathodes in heterogeneous-electro-Fenton-like reaction (HEFL) system. The X-ray diffraction and X-ray photoelectron spectroscopy results indicated that both of the catalysts are dominated with pyridinic N (2.42% and 2.82%) upon co-doping Co/N, and FeC@Co/N exhibited an obviously higher additional sp-hybridized nitrogen (sp-N) peak. The co-doping of Co/N induced the lattice modifications to produce more lattice defects, where pyridinic N and sp-N, related with the active sites (C-N, Co-Nx), were formed at near-ring defects along sheet edges through the nitrogen replacement of CC groups. FeC@Co/N demonstrated superior oxygen reduction reaction catalytic activity in terms of Cyclic Voltammetry and Rotating Ring-disk Electrode, and exhibited the remarkably higher current density (30 mA) and lower onset potential (-0.208 V) in Linear Sweep Voltammetry analysis. In the FeC@Co/N/CF modified HEFL system, despite the generated H2O2 concentrations (62.5 mg L-1) is not very high, the reducing reaction of ≡Fe(III)/Co(III)-OH could get the electron directly from the cathode, which would greatly reduce the consumption of H2O2, high utilization efficiency of H2O2 (η: 87.63%) could greatly improve the EDTA-Ni removal (97.5%) and TOC (92.6%). This work demonstrates the feasibility of utilizing FeC@Co/N/CF as a cathode for breaking metal-complex in HEFL process.


Assuntos
Cobalto/química , Ácido Edético/química , Técnicas Eletroquímicas/métodos , Nanopartículas Metálicas/química , Níquel/química , Catálise , Descontaminação , Técnicas Eletroquímicas/instrumentação , Eletrodos , Grafite/química , Peróxido de Hidrogênio/química , Ferro/química , Nitrogênio/química , Oxirredução , Piridinas/química , Eliminação de Resíduos Líquidos/instrumentação , Eliminação de Resíduos Líquidos/métodos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA