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1.
Water Sci Technol ; 81(3): 518-528, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-32385205

RESUMEN

Graphitic carbon nitride (g-C3N4) has attracted a large amount of research, mainly being used as a photocatalyst, but its Fenton-like catalytic performance has been overlooked. In this paper, the dark Fenton-like catalytic performance of g-C3N4 was evaluated by degrading rhodamine B over a wide pH range. The results showed that the g-C3N4, which was synthesized by conventional urea pyrolysis without any modification, was an efficient metal-free heterogeneous Fenton-like catalyst. The highest activity occurred under a weakly alkaline condition of about pH 10. The experiment of catalyst recycling indicated that g-C3N4 had long-term stability. The reactive oxidizing species of HO·, generated by the g-C3N4 activating H2O2, was identified by EPR and further supported by a scavenging experiment of HO· using isopropanol as the scavenger. The HNO3 oxidation of g-C3N4 resulted in catalytic deactivation, implying the catalytic activity originated from the surface reduced groups of g-C3N4. The structure of synthesized g-C3N4 before and after the HNO3 oxidation was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, and a possible catalytic mechanism was proposed.


Asunto(s)
Contaminantes Ambientales , Grafito , Peróxido de Hidrógeno , Nitrilos , Compuestos de Nitrógeno
2.
J Environ Manage ; 267: 110629, 2020 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-32349954

RESUMEN

The modified multifunctional electrodes for electro-Fenton (EF) process are suggested to be promising cathodes for in situ electro-generation and activation of H2O2 to produce hydroxyl radicals (•OH). However, heterogeneous EF process still faces the challenges of limited catalytic activity and releasing of massive amounts of transition metals to the solution after removal of organic pollutants. The main aim of the present investigation was to prepare a cathode containing carbon nanotubes (CNTs) and CuFe nano-layered double hydroxide (NLDH) for degradation and mineralization of cefazolin antibiotic through electro-Fenton process. Structural and electrochemical analyses demonstrated that CuFeNLDH-CNTs nanocomposite was successfully incorporated on the surface of graphite cathode. Due to the increased formation of •OH in the reactor, the incorporation of CNTs into NLDH matrix with a catalyst loading of 0.1 g substantially improved the degradation efficiency of cefazolin (89.9%) in comparison with CNTs-coated (28.7%) and bare graphite cathode (22.8%) within 100 min. In the presence of 15 mM of ethanol, the degradation efficiency of cefazolin was remarkably decreased to 43.7% by the process, indicating the major role of •OH in the destruction of target molecules. Acidic conditions favored the degradation efficiency of cefazolin by the modified EF process. Mineralization efficiency of the bio-refractory compound was obtained to be 70.1% in terms of chemical oxygen demand (COD) analysis after 300 min. The gas chromatography-mass spectroscopy (GC-MS) analysis was also implemented to identify the intermediate byproducts generated during the degradation of cefazolin in the CuFeNLDH-CNTs/EF reactor.


Asunto(s)
Grafito , Nanotubos de Carbono , Contaminantes Químicos del Agua , Cefazolina , Electrodos , Peróxido de Hidrógeno , Oxidación-Reducción
3.
Water Sci Technol ; 81(1): 178-189, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-32293601

RESUMEN

This study aims to explore the photocatalytic potential of graphene-oxide-based metal ferrites for the degradation of acetamiprid (an odorless neonicotinoid pesticide). Metal (Mn and Ni) ferrites (along with their graphene oxide composites) were prepared by the hydrothermal method while graphene oxide (GO) was synthesized using a modified Hummer's method. The composites were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The photocatalysts were studied for their Fenton-like advanced oxidation process to degrade acetamiprid. The composites showed excellent activity against acetamiprid degradation (>90%) in 60 min under UV irradiation. The detailed optimization study was carried out to investigate the influential variables (such as pH, catalyst dose, pollutant concentration, irradiation time, oxidant dose, etc.) to achieve enhanced degradation efficiency. Moreover, the findings were endorsed by central composite design (CCD). It was concluded that degradation was enhanced in an appropriate combination of photocatalyst and hydrogen peroxide. The magnetic character of the metal ferrites and their composites played an important role in the easy separation and reusability of these materials. The present findings result in highly effective, easy to handle and stable heterogeneous photo-Fenton materials for wastewater remediation.


Asunto(s)
Grafito , Compuestos Férricos , Neonicotinoides
4.
Bioresour Technol ; 308: 122935, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32247947

RESUMEN

Accelerated denitrification is an essential problem in the biological treatment of nitrogenous wastewater. In this study, we report that denitrification is accelerated by micro-graphite particles (MGPs). The denitrification rate was increased by 83.4% or 11.1% in synthetic (with 0.16 g/L MGPs) or industrial nitrogenous wastewater (with 0.12 g/L MGP), respectively. The mechanism was revealed via a quantitative polymerase chain reaction (q-PCR), high-throughput sequencing, and scanning electron microscopy (SEM). The abundance of denitrifying bacteria Paracoccus in the sludge was increased by micro-graphite particles. The number of denitrifying bacteria with the nirS gene was increased significantly (75.6%). To the best of our knowledge, this is the first report that MGP could enhance denitrification via the sludge. MGP can denitrify in industrial applications.


Asunto(s)
Desnitrificación , Grafito , Bacterias , Reactores Biológicos , Nitrógeno , Aguas del Alcantarillado , Aguas Residuales
5.
Water Res ; 176: 115735, 2020 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-32224330

RESUMEN

Graphene oxide (GO) sheets are unstable in aqueous environments, and the effect of photo-transformation on GO toxicity to freshwater algae (Chlorella pyrenoidosa) was investigated. Our results demonstrated that GO underwent photo-reduction under 25-day sunlight irradiation, and the transformation was generally completed at Day 8. The toxicological investigation showed that 8-day sunlight irradiation significantly increased growth inhibition of GO (25 mg/L) to algal cells by 11.2%, due to enhanced oxidative stress and stronger membrane damage. Low molecular weight (LMW) species were produced during the 8-day GO transformation, and they were identified as two types of aromatic compounds, which played a crucial role in increasing toxicity. The combined toxicity of GO and Cu2+ ions before and after light irradiation was further investigated. Antagonistic effect was observed between the toxicity of pristine GO and co-existing Cu2+ ions. After co-irradiation of GO and Cu2+ ions for 8 days, their combined toxicity was unexpectedly lower or insignificant in comparison with the treatments of pristine GO, or pristine GO in the presence of Cu2+ ions. Two mechanisms were revealed for this finding: (1) Cu2+ ions suppressed the photo-transformation of GO; (2) the toxicity of free Cu2+ ions was decreased through the adsorption/retention of Cu2+ ions and formation of Cu-based nanoparticles (e.g., Cu2O and Cu2S) on the photo-transformed GO. The provided data are helpful for better understanding the environmental process and risk of GO under natural conditions.


Asunto(s)
Chlorella , Grafito , Contaminantes Químicos del Agua , Agua Dulce , Iones , Metales
6.
ACS Nano ; 14(4): 5135-5142, 2020 04 28.
Artículo en Inglés | MEDLINE | ID: mdl-32293168

RESUMEN

Coronavirus disease 2019 (COVID-19) is a newly emerging human infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, previously called 2019-nCoV). Based on the rapid increase in the rate of human infection, the World Health Organization (WHO) has classified the COVID-19 outbreak as a pandemic. Because no specific drugs or vaccines for COVID-19 are yet available, early diagnosis and management are crucial for containing the outbreak. Here, we report a field-effect transistor (FET)-based biosensing device for detecting SARS-CoV-2 in clinical samples. The sensor was produced by coating graphene sheets of the FET with a specific antibody against SARS-CoV-2 spike protein. The performance of the sensor was determined using antigen protein, cultured virus, and nasopharyngeal swab specimens from COVID-19 patients. Our FET device could detect the SARS-CoV-2 spike protein at concentrations of 1 fg/mL in phosphate-buffered saline and 100 fg/mL clinical transport medium. In addition, the FET sensor successfully detected SARS-CoV-2 in culture medium (limit of detection [LOD]: 1.6 × 101 pfu/mL) and clinical samples (LOD: 2.42 × 102 copies/mL). Thus, we have successfully fabricated a promising FET biosensor for SARS-CoV-2; our device is a highly sensitive immunological diagnostic method for COVID-19 that requires no sample pretreatment or labeling.


Asunto(s)
Betacoronavirus/aislamiento & purificación , Técnicas Biosensibles , Infecciones por Coronavirus/diagnóstico , Neumonía Viral/diagnóstico , Transistores Electrónicos , Técnicas de Laboratorio Clínico , Grafito , Humanos , Nanotecnología/instrumentación , Cavidad Nasal , Pandemias , Manejo de Especímenes
7.
Water Sci Technol ; 81(2): 228-240, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-32333656

RESUMEN

A magnetic graphene oxide nanocomposite modified by the ionic liquid 1-amino-3-methylimidazole chloride (LI-MGO) was prepared by the chemical coprecipitation method as a phenol adsorbent for the treatment of contaminated aqueous environments. The structure of the prepared nanocomposite was investigated using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The prepared nanoparticles exhibited a BET (Brunauer-Emmett-Teller) specific surface area of 110.44 m2 g-1 and total pore volume of 0.2839 cm3 g-1. The results revealed that the adsorption process had the highest phenol removal percentage (95.3%) under optimum conditions (pH = 3, nanocomposite concentration = 0.04 g/l at room temperature). Kinetic studies showed a significant fit to the pseudo-second-order kinetic model (R2 > 0.9997) giving an equilibrium rate constant (K2) of 0.000119 gmg-1 min-1 for phenol loaded. The experimental adsorption data were better fitted with the Langmuir isotherm model than with the Freundlich isotherm model. To further investigate the phenol removal optimization process of the modified magnetic nanoparticles, and to determine the effect of each parameter on the adsorption process, the Taguchi optimization approach was used. The adsorption of these synthesized nanocomposites is among the low-cost, high-efficiency processes that can be used for the reduction/elimination of environmental pollutants, especially in aqueous environments.


Asunto(s)
Grafito , Líquidos Iónicos , Nanocompuestos , Nanopartículas , Contaminantes Químicos del Agua , Adsorción , Cinética , Fenómenos Magnéticos , Óxidos , Fenol , Espectroscopía Infrarroja por Transformada de Fourier
8.
Chemosphere ; 250: 126177, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32114336

RESUMEN

A novel superhydrophobic gas diffusion electrode based on carbon black (CB)- polytetrafluoroethylene (PTFE) modified graphite felt cathode was prepared to increase oxygen mass transfer efficiency and produce hydrogen peroxide at the gas-liquid-solid three-phase interface without aeration. The gas diffusion electrode system was further tested for the degradation of sulfamethazine (SMT) by electro-Fenton (EF) and photoelectro-Fenton (PEF). In the EF process, SMT was removed effectively, but the mineralization degree was not high due to the generation of organic acids which were difficult to be further degraded. While in the PEF process, organic contaminant can be destroyed by the combined action of Fe2+/H2O2, UV/H2O2 and UV radiation, and more efficient mineralization (>83.5%) at low current (50 mA) was attained, which might be attributed to the high H2O2 utilization (70-90%), rapid regeneration of Fe2+ and photolysis of intermediates. In addition, it was verified that the PEF system had a good adaptability to pH and pollutant concentration. Compared with aeration system, the use of this active gas diffusion cathode in electrochemical advanced oxidation processes significantly reduced energy consumption.


Asunto(s)
Sulfametazina/toxicidad , Contaminantes Químicos del Agua/toxicidad , Difusión , Electrodos , Grafito/química , Peróxido de Hidrógeno/química , Hierro/química , Oxidación-Reducción , Fotólisis , Rayos Ultravioleta , Contaminantes Químicos del Agua/análisis
9.
Environ Monit Assess ; 192(4): 222, 2020 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-32146527

RESUMEN

The determination of trace metal contents directly from a solid sample is a trend in modern atomic spectrometry. The aim of this study was to develop an analytical method for the routine determination of Cd in lichens using solid sampling graphite furnace atomic absorption spectrometry (SS-GF-AAS). For the determination of Cd, the temperature program of the graphite furnace was optimized using a mixed matrix modifier (Pd + Mg (NO3)2 + Triton X-100). The limit of detection and the limit of quantification were 0.9 µg/kg and 3 µg/kg, respectively. The analytical method for Cd determination in the plant matrix was verified by the analysis of certified reference materials of lichens, seaweed, and rye grass. The developed procedure was applied to the study of Cd distribution in thalli of Usnea antarctica lichen from James Ross Island, Antarctica. The SS-GF-AAS analytical method is particularly suited for use in environmental studies and plant physiology (the microanalysis of anatomical structures).


Asunto(s)
Cadmio , Contaminantes Ambientales , Grafito , Líquenes , Regiones Antárticas , Cadmio/análisis , Monitoreo del Ambiente , Contaminantes Ambientales/análisis , Islas , Líquenes/química , Espectrofotometría Atómica
10.
J Environ Manage ; 261: 110189, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32148265

RESUMEN

The removal of styrene from wastewater by pervaporation was investigated by using composite PDMS membranes filled with reduced graphene oxide on PES support layers. Graphene oxide was synthesized through modified Hummers' method and then chemically reduced. The filler was characterized by TEM, SEM, XRD, and AFM. The top layers with different PDMS molecular weights were cast on the PES supports, which were prepared by phase inversion method. The characterizations of prepared membranes were investigated by SEM, AFM, contact angle measurement, TGA, and DSC. It was observed that presence of the filler in the polymeric matrix controls the swelling of the membrane and enhances its solubility parameter in favor of styrene. Moreover, it significantly improves the thermal stability of the membranes. The mechanism of separation in the process was found to be affected mainly by enhancing in the membrane's solubility rather than in its diffusivity. The pervaporative performance of prepared membranes showed their great affinity toward styrene so that the separation factor of the optimum membrane (M2/S) was increased about 250% (600.4 in comparison to 241.4 for the unfilled membrane) while its total flux was decreased from 772.5 g m-2.h-1for the unfilled membrane to 321.9 g m-2.h-1. Increasing the molecular weight of PDMS lowered the optimal rGO content due to the complexity of the diffusion path and occupation of free volume by longer polymer chains. Accordingly, a lower total flux (124.7 g m-2.h-1 for high MW compared to 718.0 g m-2.h-1 for low MW) and higher separation factor (822.5 for high MW compared to 230.8 for low MW) were yielded for the same filler content (0.1 wt% rGO).


Asunto(s)
Grafito , Aguas Residuales , Membranas Artificiales , Estireno
11.
Chemosphere ; 250: 126262, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32114342

RESUMEN

As an attractive alternative to radioactive cesium removal, we introduced an adsorptive filtration method using a composite membrane consisting of potassium copper hexacyanoferrate (KCuHCF) and graphene-based support. Polyethyleneimine-grafted reduced graphene oxide (PEI-rGO), used as an immobilizing matrix, was effective not only in distributing KCuHCF inside the composite with the aid of abundant amino-functionality, but also in achieving high water flux by increasing the interlayer spacing of the laminar membrane structure. Due to the rapid and selective cesium adsorption properties of KCuHCF, the fabricated membrane was found to be effective in achieving complete removal of cesium ions under a high flux (over 500 L m-2 h-1), which is difficult in a conventional membrane utilizing the molecular sieving effect. This approach offers strong potential in the field of elimination of radionuclides that require rapid and complete decontamination.


Asunto(s)
Cesio/química , Ferrocianuros/química , Grafito/química , Eliminación de Residuos Líquidos/métodos , Aguas Residuales/química , Contaminantes Químicos del Agua/química , Adsorción , Cobre/química , Filtración , Polietileneimina/química , Potasio , Agua
12.
J Environ Sci (China) ; 90: 395-407, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32081335

RESUMEN

In this work, we proposed a green and cost-effective method to prepare a graphene-based hyper-cross-linked porous carbon composite (GN/HCPC) by one-pot carbonization of hyper-cross-linked polymer (HCP) and glucose. The composite combined the advantages of graphene (GN) and hyper-cross-linked porous carbon (HCPC), leading to high specific surface area (396.93 m2/g) and large total pore volume (0.413 cm3/g). The resulting GN/HCPC composite was applied as an adsorbent to remove 2,4-dichlorophenol (2,4-DCP) from aqueous solutions. The influence of different solution conditions including pH, ionic strength, contact time, system temperature and concentration of humic acid was determined. The maximum adsorption capacity of GN/HCPC composite (calculated by the Langmuir model) could reach 348.43 mg/g, which represented increases of 43.6% and 13.6% over those of the as-prepared pure GN and HCPC, respectively. The Langmuir model and pseudo-second-order kinetic model were found to fit well with the adsorption process. Thermodynamic experiments suggested that the adsorption proceeded spontaneously and endothermically. In addition, the GN/HCPC composite showed high adsorption performance toward other organic contaminants including tetracycline, bisphenol A and phenol. Measurement of the adsorption capability of GN/HCPC in secondary effluent revealed a slight decrease over that in pure water solution. This study demonstrated that the GN/HCPC composite can be utilized as a practical and efficient adsorbent for the removal of organic contaminants in wastewater.


Asunto(s)
Clorofenoles/química , Grafito/química , Contaminantes Químicos del Agua/química , Adsorción , Carbono , Cinética , Porosidad
13.
Chemosphere ; 247: 125910, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-32069715

RESUMEN

The photocatalytic degradation of the antibiotic ciprofloxacin in water was carried out with nanosheets of graphitic carbon nitride (g-C3N4) as catalyst and visible light irradiation using low-power (4 × 10 W) white light LEDs. The aim of this study was to identify the intermediate by-products formed during the degradation and to propose a pathway for CIP degradation. To achieve this goal, photocatalytically degraded CIP solutions were analysed by liquid chromatography coupled to high-resolution mass spectrometry using a QTOF instrument. The accurate mass and the MS/MS data of the detected ions allowed us to determine the elementary composition of eight by-products and to propose the chemical structures for seven of them. Three of these by-products have been reported for the first time and the elementary composition of a fourth one that had been wrongly reported in the literature was accurately established. CIP degradation followed a pseudo-first order kinetics with a pseudo-first order kinetic constant of 0.035 min-1. In addition, a study of the influence of several scavengers showed that only the presence of triethanolamine dramatically reduced the pseudo-first order kinetic constant (0.00072 min-1), pointing out that the reactive species were the holes produced in the catalyst. Finally, the main pathway of CIP degradation seems to be the attack to the piperazine group by ·OH radicals, following heterocycle breakup and the subsequent loss of two of its carbon atoms as CO2 molecules, and then defluorination, oxidation and cleavage of the cycles of this intermediate.


Asunto(s)
Ciprofloxacino/química , Grafito/química , Compuestos de Nitrógeno/química , Contaminantes Químicos del Agua/química , Antibacterianos/química , Carbono/química , Catálisis , Cromatografía Liquida , Cinética , Luz , Oxidación-Reducción , Espectrometría de Masas en Tándem , Contaminantes Químicos del Agua/análisis
14.
Anal Bioanal Chem ; 412(7): 1509-1520, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-32002580

RESUMEN

Highly specific enrichment of N-linked glycopeptides from complex biological samples is crucial prior to mass spectrometric analysis. In this work, a hydrophilic metal-organic framework composite is prepared by the growth of UiO-66-NH2 on graphene sheets, followed by its post-synthetic modification to attach boronic acid to form GO@UiO-66-PBA. The fabrication of graphene oxide-MOF composite results in enhanced surface area with improved thermal and chemical stability. The synthesized MOF nanocomposite is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and BET. A crystalline structure with high porosity offering large surface area and good hydrophilicity of the nanocomposite assists as an enrichment tool in glycoproteomics. The GO@UiO-66-PBA nanocomposite selectively enriches N-linked glycopeptides from tryptic digests of horseradish peroxidase (HRP) and immunoglobulin (IgG). GO@UiO-66-PBA nanoparticles show a low detection limit (1 fmol) and good specificity (1:200), reusability and reproducibility for N-linked glycopeptide enrichment from IgG digest. The binding capacity of GO@UiO-66-PBA is 84 mg/g for protein concentration, with a good recovery of 86.5%. A total of 372 N-linked glycopeptides corresponding to different glycoproteins are identified from only 1 µL of human serum digest. Thus, the presented research work can be an efficient separation platform for N-linked glycopeptide enrichment from complex samples, which can be extended to cost-effective routine analysis. Graphical abstract.


Asunto(s)
Ácidos Borónicos/química , Glicopéptidos/química , Estructuras Metalorgánicas/química , Grafito/química , Peroxidasa de Rábano Silvestre/química , Humanos , Microscopía Electrónica de Rastreo , Reproducibilidad de los Resultados
15.
Chemosphere ; 248: 126008, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32006836

RESUMEN

The endless introduction of toxic heavy metals through industrialization has worsened the heavy metal pollution in the environment. Thus, the need for its effective removal has become more crucial than before. Studies on graphene-based nanomaterials and their use in removing heavy metals are gaining tremendous traction over the past decade. The properties of graphene oxide (GO), such as large surface areas, desired functional groups and excellent mechanical properties are advantageous. Nevertheless, due to its tendency to agglomerate and difficulty in phase separation after treatment, the functionalization of GO using various materials of different surface functional groups is an ongoing study. The surface modification of GO is done by using various materials to introduce heteroatoms, which have high affinity for heavy metals. This review summarizes the utilization of different surface functional groups, such as oxygen-containing, nitrogen-containing, and sulphur-containing functionalized graphene oxide composites in the adsorption of cationic and oxyanionic heavy metals. The toxicity of these heavy metals is also addressed. Furthermore, the interactions between adsorbents and heavy metals which are influenced by pH and surface functional groups, are also discussed in detail. This is followed by the review in adsorption isotherms and kinetics. Future research needs are also offered.


Asunto(s)
Contaminantes Ambientales/química , Grafito/química , Metales Pesados/química , Nanoestructuras/química , Adsorción , Iones , Cinética , Purificación del Agua
16.
Chemosphere ; 248: 125929, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32014635

RESUMEN

This research was conducted to evaluate the effect of co-transport of different-sized microorganisms on graphene oxide nanoparticles (GONPs) transport and retention in saturated pristine and biofilm-conditioned limestone columns. The transport and retention behavior of GONPs was studied in columns in the presence of MS2 -as a nano-sized- and Escherichia coli (E.coli) -as a micro-sized- microorganisms at low and high ionic strength conditions. Results showed no changes in GONPs transport and retention at high ionic strength in the presence of MS2 or E. coli, which was attributed to the effect of high concentration of divalent cation on aggregation of nanoparticles and microorganisms. Furthermore, simultaneous enhanced transport and decreased retention of GONPs in column was observed in the co-presence of microorganisms at low ionic strength. Results revealed that the main mechanism governing increasing GONPs transport in porous media was occupation of reactive surface sites of collectors by microorganisms, which prevented attachment of nanoparticles. The pre-saturation of columns with MS2 and E. coli caused increasing transport of GONPs in the columns, due to the occupation of surface reactive sites. Moreover, conditioning limestone collectors with natural biofilm resulted in the same rates of nanoparticle elution and retention (i.e., in the presence or absence of microorganisms) by straining of GONPs in the inlet end of columns which shows that the biofilm acts as a bio-filter against discharging nanoparticles into the effluents. Finally, from the obtained results, it can be postulated that the presence of microorganisms in a MAR site causes risk of groundwater pollution by toxic nanoparticles.


Asunto(s)
Carbonato de Calcio/química , Grafito/química , Nanopartículas/química , Microbiología del Agua , Biopelículas , Escherichia coli , Agua Subterránea , Concentración Osmolar , Porosidad , Dióxido de Silicio/química
17.
Sci Total Environ ; 716: 136893, 2020 May 10.
Artículo en Inglés | MEDLINE | ID: mdl-32059295

RESUMEN

Arsenic (As) is one of the most widespread contaminants; it is found in almost every environment. Its toxic effects on living organisms have been studied for decades, but the interaction of this metalloid with other contaminants is still relatively unknown, mainly whether this interaction occurs with emerging contaminants such as nanomaterials. To examine this relationship, the marine shrimp Litopenaeus vannamei was exposed for 48 h to As, graphene oxide (GO; two different concentrations) or a combination of both, and gills, hepatopancreas and muscle tissues were sampled. Glutathione S-transferase (GST)-omega gene expression and activity were assessed. As accumulation and speciation (metabolisation capacity) were also examined. Finally, a molecular docking simulation was performed to verify the possible interaction between the nanomaterial and GST-omega. The main finding was that GO modulated the As toxic effect: it decreased GST-omega activity, a consequence related to altered As accumulation and metabolism. Besides, the molecular docking simulation confirmed the capacity of GO to interact with the enzyme structure, which also can be related to the decreased GST-omega activity and subsequently to the altered As accumulation and metabolisation pattern.


Asunto(s)
Penaeidae , Animales , Arsénico , Glutatión Transferasa , Grafito , Simulación del Acoplamiento Molecular
18.
Chemosphere ; 249: 126160, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32065996

RESUMEN

Graphene oxide (GO) is widely used in different applications, however once released into the environment it can change its structure and affect the transport of important contaminants such as arsenic. In this work we show that UV radiation, even in the range of 28-74 µW/cm2 of irradiance up to 120 h of exposure, can induce important changes in the structure of graphene oxide, by eliminating -OH and CO functional groups. This reduction affected the stability of graphene oxide in water by decreasing its zeta potential from -41 to -37 mV at pH=7 with the increase of the exposure time. Our results showed that after 24 and 120 h of UV exposure, As(III) adsorption capacity decreased from 5 mg/g to 4.7 and 3.8 mg/g, respectively, suggesting a lower capacity to transport contaminants with time. Computer modelling showed that even a degraded GO structure can have an interaction energy of 223.84 kJ/mol with H3AsO3. Furthermore, we observed that the cytotoxicity of graphene oxide changed after being irradiated at 74 µW/cm2 for 120 h, showing 20% more cell viability compared to as-produced GO. Our results stress the importance of considering the microstructural and compositional changes that GO undergoes even under low irradiance and short periods, when studying its fate and behavior in the environment and possible applications in water treatment.


Asunto(s)
Arsénico/toxicidad , Grafito/química , Rayos Ultravioleta , Contaminantes Químicos del Agua/toxicidad , Adsorción , Arsénico/química , Modelos Químicos , Óxidos/química , Fenómenos Físicos , Agua , Contaminantes Químicos del Agua/química , Purificación del Agua
19.
Ecotoxicol Environ Saf ; 192: 110304, 2020 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-32066006

RESUMEN

The environmental release of graphene oxide (GO) will certainly induce the GO exposure to plants. To date, the influence of GO on the intracellular structures and the endophytic bacterial ecology of plants have been rarely reported. In the present study, the rice seedlings were exposed to GO (5 mg/L) under hydroponic condition for fifteen days with periodic stir. The cellular structures damage, GO deposition and oxidative stress were found in rice root after GO exposure. A Illumina analysis based on the bacterial 16 S rRNA gene showed that the richness, evenness and diversity of endophytic bacterial communities of rice root decreased due to GO exposure. The relative abundance of beneficial endophytic bacterial populations decreased after GO exposure. Out of potential phenotypes predicted by BugBase, the relative abundance of Gram negative, stress-tolerant and biofilm-forming phenotypes, presented an increase trend after GO exposure.


Asunto(s)
Grafito/toxicidad , Microbiota/efectos de los fármacos , Oryza/microbiología , Contaminantes Químicos del Agua/toxicidad , Bacterias/clasificación , Bacterias/efectos de los fármacos , Bacterias/genética , Bacterias/aislamiento & purificación , Endófitos/clasificación , Endófitos/efectos de los fármacos , Endófitos/genética , Endófitos/aislamiento & purificación , Grafito/metabolismo , Hidroponia , Oryza/efectos de los fármacos , Oryza/metabolismo , Estrés Oxidativo/efectos de los fármacos , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/metabolismo , Raíces de Plantas/microbiología , Plantones/efectos de los fármacos , Plantones/metabolismo , Plantones/microbiología , Contaminantes Químicos del Agua/metabolismo
20.
PLoS One ; 15(2): e0228322, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32012195

RESUMEN

This study investigates the effects of stirring duration on the synthesis of graphene oxide (GO) using an improved Hummers' method. Various samples are examined under different stirring durations (20, 40, 60, 72, and 80 h). The synthesized GO samples are evaluated through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The GO sample with 72 h stirring duration (GO72) has the highest d-spacing in the XRD results, highest atomic percentage of oxygen in EDX (49.57%), highest intensity of oxygen functional group in FTIR spectra, and highest intensity ratio in Raman analysis (ID/IG = 0.756). Results show that GO72 with continuous stirring has the highest degree of oxidation among other samples. Electrochemical impedance spectroscopy analysis shows that GO72-titanium dioxide (TiO2) exhibits smaller charge transfer resistance and higher electron lifetime compared with the TiO2-based photoanode. The GO72 sample incorporating TiO2 nanocomposites achieves 6.25% photoconversion efficiency, indicating an increase of more than twice than that of the mesoporous TiO2 sample. This condition is fully attributed to the efficient absorption rate of nanocomposites and the reduction of the recombination rate of TiO2 by GO in dye-sensitized solar cells.


Asunto(s)
Colorantes/química , Suministros de Energía Eléctrica , Grafito/química , Energía Solar
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