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1.
Chemosphere ; 241: 124978, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31590023

RESUMO

Metal-organic frameworks (MOFs) have received significant attention as promising precursors or sacrificial templates in the preparation of porous carbon supported catalysts. In this study, N-doped porous carbon supported Ni catalysts (denoted as Ni/NC) were prepared using furfuryl alcohol (FA) loaded Ni-MOF-74 as the precursor followed by NH4OH treatment and pyrolysis under N2 atmosphere. For comparison purpose, Ni catalysts supported on porous carbon (denoted as Ni/C) were also prepared by direct pyrolysis of Ni-MOF-74. The selective gas phase catalytic hydrodechlorination of 1,2-dichloroethane to ethylene was carried out to evaluate the catalytic performances of the catalysts. It was found that for Ni catalysts prepared at the same pyrolysis temperature, Ni particle sizes in Ni/NC catalysts were significantly smaller (20-40% smaller) than that of Ni/C. This reflected that pre-modification of Ni-MOF-74 using FA and NH4OH could effectively increase Ni dispersion in Ni catalysts derived from Ni-MOF-74. Moreover, Ni/NC had a markedly stronger ability to form spillover H2 owing to the enhanced metal-support interactions by N-doping. Accordingly, Ni/NC catalysts exhibited much higher catalytic activities than Ni/C catalysts. The turnover frequencies of Ni/NC catalysts were found to be 1.22-1.65 times higher than Ni/C catalysts. Increasing pyrolysis temperature led to decreased catalytic activities of both Ni/C and Ni/NC catalysts, due to the aggregation of Ni particles at higher treatment temperature. The findings from this study demonstrate that the MOF-mediated synthesis method offers a promising way to prepare Ni-based catalysts for catalytic hydrodechlorination of chlorinated hydrocarbons.

2.
Talanta ; 207: 120299, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31594611

RESUMO

Analysis on mixture toxicity (Mix-tox) of the multi-chemical space is constantly followed with interest for many researchers. Conventional toxicity tests with time-consuming and costly operations make researchers can only establish some toxicity prediction models aiming to a limited sampling dimension. The rapid development of machine learning (ML) algorithm will accelerate the exploration of many fields involving toxicity analysis. Rather than the model calculation capacity, the challenge of this process mainly comes from the lack of toxicology big-data to perform toxicity perception through the ML model. In this paper, a full strategy based a standardized high-throughput experiment was developed for Mix-tox analysis throughout the whole routine, from big-sample dataset design, model building, and training, to the toxicity prediction. Using the concentration variates as input and bio-luminescent inhibition rate as output, it turned out that a well-trained random forest algorithm was successfully applied to assess the mixtures' toxicity effect, suggesting its value in facilitating adoption of Mix-tox analysis.

3.
Chem Commun (Camb) ; 56(7): 1058-1061, 2020 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-31872203

RESUMO

A machine learning (ML) strategy based on color-spectral images for mixed amino acid (AA) analysis is presented. The results showed that a well-trained ML model could accurately predict multiple AAs at the same time, suggesting its value for facilitating quantitative analysis of mixed AA systems.

4.
J Hazard Mater ; : 121745, 2019 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-31796356

RESUMO

In this work, we coated carbon nanotubes (CNT) supported Pt catalyst by conductive carbon layers (labelled as Pt/CNT@C) and the catalyst was further functionalized by surface oxidation (denoted as Pt/CNT@Oxi-C). The textural properties of the catalysts were extensively characterized and liquid phase catalytic hydrogenation reduction of Cu2+ was conducted. Results showed that Pt particles of Pt/CNT@C and Pt/CNT@Oxi-C were completely embedded beneath carbon overcoatings. Furthermore, contrary to Pt/CNT no CO chemisorption was observed on both Pt/CNT@C and Pt/CNT@Oxi-C, indicative of the absence of exposed Pt particles in carbon-coated Pt/CNT. Effective Cu2+ reduction and metallic Cu deposition by catalytic hydrogenation were achieved on catalyst surface. Surface oxidation of Pt/CNT@C resulted in increased surface wetting and functionality content, leading to noticeable enhancement in catalytic activity for Cu2+ reduction. Additionally, Cu2+ reduction on Pt/CNT@Oxi-C proceeded through the Langmuir-Hinshelwood model, suggesting that the reduction of Cu2+ adsorbed on catalyst surface was the rate-determining step. Carbonization of overcoatings exhibited a volcano-type relationship between carbonization temperature and catalytic activity of Pt/CNT@C for Cu2+ reduction. As for catalyst reuse, Pt/CNT lost 92 % of initial activity after five consecutive reaction cycles, whereas Pt/CNT@Oxi-C maintained a high catalytic activity without remarkable deactivation.

5.
Chem Commun (Camb) ; 55(78): 11786-11789, 2019 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-31524203

RESUMO

A novel Pt-based catalyst with fine and homogeneous Pt particles embedded in carbon rods of N-doped CMK-3 was fabricated by a two-step infiltration method using SBA-15 as the template. Due to its fine particle size, N-containing functionality and effective embedment of Pt particles in carbon rods, the catalyst exhibited superior catalytic activity and stability in the liquid phase catalytic hydrogenation of bromate in water.

6.
Anal Chim Acta ; 1078: 70-77, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358230

RESUMO

Solid-phase microextraction (SPME) has been widely used in analysis of trace organic contaminants in environmental samples. Stable, efficient, and selective fiber coating is the key to the development of SPME technique. In this study, an in situ fabricated porous carbon coating that derived from metal-organic frameworks (MOFs) was introduced for solid-phase microextraction (SPME). The carbon coating (denoted as MOF-74-C) was prepared by the direct carbonization of a MOF-74 coating that was in situ grown on stainless steel wire, which was explored for the extraction of odorous organic contaminants for the first time. MOF-74-C coated fiber showed high extraction efficiency (1.1-16.0 times larger than commercial fibers for most tested analytes under the same extraction conditions), as well as good thermal and chemical stability. Furthermore, it can selectively extract the analytes with the simultaneous exclusion of coexisting dissolved organic matter due to the molecular sieve effect invoked by the well-defined micropores. The method based on MOF-74-C coating for analysis of odorants afforded wide linear ranges (more than two orders of magnitude), low detection limits (below the odor threshold concentrations), good intra- and inter-day accuracies (90.1-107.3%) and precisions (relative standard deviations/RSDs below 9.4%) and satisfactory reproducibility (RSDs below 8.7%). Finally, the MOF-74-C coated fiber was successfully applied for the SPME analysis of odorants in real water samples. These results highlight the great potential of in situ fabricated porous carbons derived from MOFs for SPME applications.

7.
J Colloid Interface Sci ; 552: 134-141, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31112809

RESUMO

Although adsorbents can effectively remove phosphate from water, most are difficult to separate from water and their phosphate removal efficiencies are adversely affected by coexisting anions or humic acid. Here, a magnetic core-shell composite with Fe3O4 as the core and carbon as the shell (denoted as MFC) was functionalized with a metal-organic framework, UiO-66, and its phosphate adsorption ability was studied. The composite (denoted as MFC@UiO-66) was effectively separated from water within 1 min under an external magnetic field. The kinetics of phosphate adsorption onto MFC@UiO-66 was controlled by the intraparticle diffusion process, suggesting that the Zr in UiO-66 played an important role in phosphate adsorption. The isotherm for phosphate adsorption onto MFC@UiO-66 was well described by the Freundlich model. The adsorbent exhibited higher affinity toward phosphate than toward coexisting anions (e.g., Cl-, NO3-, and SO42-), reflecting high phosphate adsorption selectivity. The adsorption affinity of MFC@UiO-66 to phosphate increased with the increasing temperature, but decreased with increasing pH. The presence of dissolved humic acid negligibly affected phosphate adsorption onto MFC@UiO-66 because of its size-exclusion effects. The used adsorbent was easily regenerated with NaOH solution, and the sorbent displayed stable phosphate adsorption behavior after five regeneration cycles.

8.
Sci Total Environ ; 663: 673-685, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30731413

RESUMO

Liquid phase catalytic reduction of bromate with supported noble metals as the catalysts is a promising method to remove bromate in water. Magnetic supports provide a feasible way to recover catalysts whose surface properties also strongly influence the catalytic efficiency. In this study, Pd nanoparticles supported on core-shell structured magnetites with varied shells (e.g., carbon, SiO2, polypyrrole, polyaniline, polydopamine and chitosan) were prepared and catalytic reduction of bromate on the catalysts was investigated. The results showed that in comparison with other catalysts Pd/(Fe3O4@polyaniline) exhibited a higher catalytic efficiency due to its higher point of zero charge and surface hydrophilicity. In parallel, bromate reduction on Pd/(Fe3O4@polyaniline) followed the Langmuir-Hinshelwood model, confirming the crucial role of bromate adsorption. At pH 5.6 and a catalyst dosage of 0.05 g/L, 0.4 mM bromate could be completely reduced into bromide within 120 min. Furthermore, the magnetic catalysts could be effectively separated and recovered under an external magnetic field within 3 min. The results of catalyst reuse showed that after five consecutive catalytic reduction cycles Pd/(Fe3O4@polyaniline) retained 87% of its fresh catalyst activity. The present findings indicate that Pd/(Fe3O4@polyaniline) with polyaniline as the shell is a highly active, stable and recyclable catalyst for liquid phase catalytic hydrogenation of pollutants in water.

9.
Chemosphere ; 217: 742-753, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30448754

RESUMO

Liquid catalytic hydrogenation is a green and cost-effective technique for the reductive removal of pollutants in water. Supported noble metals are the most frequently used catalysts in liquid phase catalytic hydrogenation, whereas marked catalyst deactivation is commonly identified. In this study, we coated supported Pd catalyst on carbon nanotube (denoted as Pd/CNT) by different overcoatings (including SiO2, carbon and N-doped carbon) to prevent catalyst deactivation. The activities of the coated catalysts for liquid phase catalytic hydrogenation reduction of hexavalent chromium (Cr(VI)) differed with the overcoating properties. Negligible Cr(VI) conversion was observed on SiO2 coated Pd/CNT, while feasible Cr(VI) reduction was identified on carbon coated (denoted as Pd/CNT@C) and N-doped carbon coated catalysts (denoted as Pd/CNT@CN). Pd/CNT@CN exhibited a much higher catalytic activity than Pd/CNT@C, which was ascribed to the stronger Cr(VI) adsorption on CN overcoating. The catalytic activity of Pd/CNT@CN was positively correlated with the conductivity and hydrophilicity of CN overcoating, which could be optimized by varying carbonization temperature. Furthermore, Pd/CNT@CN retained its initial activity after ten consecutive catalyst cycles without any deactivation, whereas Pd/CNT only retained 8.2% of its initial activity, reflecting much higher catalytic stability of Pd/CNT@CN than Pd/CNT. The findings in the present study highlight that liquid catalytic reduction using Pd/CNT@CN as the catalyst is a highly stable and effective method to remove Cr(VI) in water.


Assuntos
Cromo/química , Hidrogenação , Purificação da Água/métodos , Adsorção , Catálise , Cromo/isolamento & purificação , Nanotubos de Carbono/química , Oxirredução , Paládio/química , Poluentes Químicos da Água/isolamento & purificação
10.
Chemosphere ; 210: 907-916, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30208550

RESUMO

Highly dispersed ZrO2 particles confined in the MIL-101 (denoted as MIL-101@Zr(DS)) with varied ZrO2 loading amounts were prepared by the double solvents method. For comparison, ZrO2 loaded MIL-101 samples were synthesized by the conventional impregnation method (denoted as MIL-101@Zr(I)) and the deposition method (denoted as MIL-101@Zr(D)). The characterization results indicated that for MIL-101@Zr(DS), ZrO2 particles were dominantly confined in MIL-101 with a much higher dispersion as compared with MIL-101@Zr(I) and MIL-101@Zr(D). The maximum phosphate adsorption capacity and ZrO2 content normalized phosphate adsorption capacity of the MIL-101@Zr(DS) were 21.28 mg P·g-1 and 1120.0 mg P·g-1, respectively. Additionally, the ZrO2 content normalized phosphate adsorption capacity was significantly larger than that for MIL-101@Zr(I) and MIL-101@Zr(D) as well as the reported values for other Zr-based adsorbents. The effects of solution chemistry on phosphate adsorption to MIL-101@Zr(DS), MIL-101@Zr(I) and MIL-101@Zr(D) were also examined. Compared with MIL-101@Zr(I) and MIL-101@Zr(D), the adsorption of phosphate on MIL-101@Zr(DS) was less affected by the coexistence of anions and dissolved humic acid. Increasing pH from 3 to 12 led to decreased phosphate adsorption capacity of MIL-101@Zr(DS) from 10.38 mg P·g-1 to 2.03 mg P·g-1. Accordingly, used MIL-101@Zr(DS) could be effectively regenerated under alkaline conditions and exhibited stable adsorption-desorption performance.


Assuntos
Estruturas Metalorgânicas/química , Nanopartículas/química , Fosfatos/química , Zircônio/química , Adsorção
11.
Environ Sci Technol ; 52(18): 10453-10461, 2018 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-30092628

RESUMO

Vegetation fire generates vast amounts of mineral ash annually that can be readily mobilized by water or wind erosion. Little is known about the photoactivity of dissolved mineral ash in aquatic systems and its ability to mediate redox reactions of environmental pollutants. This study reports that dissolved mineral ash derived from pyrolysis of biomass is photoactive under simulated sunlight, generating reactive oxygen species. It can mediate the photoreduction of hexavalent chromium (Cr(VI)) in the presence of electron donors; for example, phenols and dissolved organic matter, at pH 4.7. The reaction kinetics followed the Langmuir-Hinshelwood model, suggesting a heterogeneous photocatalytic reaction. The enhancement of reduction efficiency was linearly correlated with the one-electron reduction potential of phenols. The synergy between dissolved mineral ash and phenols is attributed to the inhibition of electron-hole recombination. The reduction rate decreases with increasing solution pH, owing to the decreased reduction potential and surface adsorption of Cr(VI). The silicon and silicon carbide components are most likely responsible for the photocatalytic activity of dissolved mineral ash. Our results suggest that dissolved mineral ash is a natural photocatalyst that can mediate redox reactions of pollutants in sunlit aquatic systems, playing an overlooked role in natural attenuation and aquatic photochemistry.


Assuntos
Luz Solar , Poluentes Químicos da Água , Adsorção , Cromo , Minerais , Oxirredução , Fotoquímica
12.
Environ Sci Technol ; 52(7): 4040-4050, 2018 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-29505247

RESUMO

Sunlight-induced photoformation of silver nanoparticles (nAg), mediated by natural organic matter (NOM), is significantly affected by the concentration of Ag(I) and chloride. The initial photoformation rates of nAg in Suwannee River humic acid (SRHA) and Suwannee River natural organic matter (SRNOM) solutions were examined under simulated sunlight irradiation. A critical induction concentration (CIC) of Ag(I) (10 mg/L for SRHA and 5 mg/L for SRNOM, respectively) was observed, below which the nAg formation was minimal. The threshold is attributed to the interplay of reduction and oxidation reactions mediated by NOM, reflecting the need to achieve sufficiently fast growth of silver clusters to outcompete oxidative dissolution. The CIC can be reduced by scavenging oxidative radicals or be increased by promoting singlet oxygen and hydrogen peroxide generation. The presence of chloride effectively reduced the CIC by forming AgCl, which facilitates reduction reactions and provides deposition surfaces. SRNOM is more efficient in mediating photoformation of nAg than SRHA, owing to their differed phototransient generation. These results highlight prerequisites for the photoformation of nAg mediated by NOM, in which the photochemistry and solution chemistry are both important.


Assuntos
Nanopartículas Metálicas , Prata , Substâncias Húmicas , Íons , Luz Solar
13.
Environ Sci Technol ; 52(7): 4031-4039, 2018 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-29553250

RESUMO

Nanoscale titanium dioxide ( nTiO2) is one of the most widely used metal oxide nanomaterials. Once released into the environment, nTiO2 may catalyze abiotic transformation of contaminants and consequently affect their fate and effects. Here, we show that the overall catalytic efficiency of nTiO2 for the dehydrochlorination reaction of 1,1,2,2-tetrachloroethane, a commonly used solvent, depends on the crystalline phase and exposed facets of nTiO2, which significantly affect the adsorption capacity and surface catalytic activity of nTiO2. Specifically, under all three pH conditions tested (7.0, 7.5 and 8.0), the overall catalytic efficiency of eight nTiO2 materials (as indicated by the surface-area-normalized reaction kinetic constants) followed the order of rutile > anatase > TiO2(B). For anatase and TiO2(B) materials, the overall catalytic efficiency increased with the increasing percentage of exposed {001} and {010} facets, respectively. Crystalline phase and exposed facets significantly affected adsorption affinities of nTiO2, likely by modulating surface hydrophobicity of nTiO2. Crystalline phase and exposed facets also determined the activity of surface catalytic sites on nTiO2 by dictating the concentration and strength of surface unsaturated Ti atoms, as the deprotonated hydroxyl groups chemisorbed to these reactive Ti atoms served as bases to catalyze the base-promoted reaction.


Assuntos
Nanoestruturas , Titânio , Adsorção , Catálise , Etano/análogos & derivados , Hidrocarbonetos Clorados , Óxidos
14.
Chemosphere ; 197: 485-493, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29407810

RESUMO

As a broad-spectrum preservative, toxic o-phenylphenol (OPP) was frequently detected in aquatic environments. In this study, N-doped mesoporous carbon was prepared by a hard template method using different nitrogen precursors and carbonization temperatures (i.e., 700, 850 and 1000 °C), and was used to activate peroxymonosulfate (PMS) for OPP degradation. For comparison, mesoporous carbon (CMK-3) was also prepared. Characterization results showed that the N-doped mesoporous carbon samples prepared under different conditions were perfect replica of their template. In comparison with ethylenediamine (EDA) and dicyandiamide (DCDA) as the precursors, N-doped mesoporous carbon prepared using EDA and carbon tetrachloride as the precursors displayed a higher catalytic activity for OPP degradation. Increasing carbonization temperature of N-doped mesoporous carbon led to decreased N content and increased graphitic N content at the expense of pyridinic and pyrrolic N. Electron paramagnetic resonance (EPR) analysis showed that PMS activation on N-doped mesoporous carbon resulted in highly active species and singlet oxygen, and catalytic PMS activation for OPP degradation followed a combined radical and nonradical reaction mechanism. Increasing PMS concentration enhanced OPP degradation, while OPP degradation rate was independent on initial OPP concentration. Furthermore, the dependency of OPP degradation on PMS concentration followed the Langmuir-Hinshelwood model, reflecting that the activation of adsorbed PMS was the rate controlling step. Based on the analysis by time-of-flight mass spectrometry, the degradation pathway of OPP was proposed.


Assuntos
Compostos de Bifenilo/química , Modelos Químicos , Peróxidos/química , Poluentes Químicos da Água/química , Adsorção , Compostos de Bifenilo/análise , Carbono/química , Catálise , Nitrogênio/química
15.
Chemosphere ; 194: 405-413, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29223811

RESUMO

Dissolved black carbon (DBC) is ubiquitous in aquatic systems, being an important subgroup of the dissolved organic matter (DOM) pool. Nevertheless, its aquatic photoactivity remains largely unknown. In this study, a range of spectroscopic indices of DBC and humic substance (HS) samples were determined using UV-Vis spectroscopy, fluorescence spectroscopy, and proton nuclear magnetic resonance. DBC can be readily differentiated from HS using spectroscopic indices. It has lower average molecular weight, but higher aromaticity and lignin content. The apparent singlet oxygen quantum yield (Φsinglet oxygen) of DBC under simulated sunlight varies from 3.46% to 6.13%, significantly higher than HS, 1.26%-3.57%, suggesting that DBC is the more photoactive component in the DOM pool. Despite drastically different formation processes and structural properties, the Φsinglet oxygen of DBC and HS can be well predicted by the same simple linear regression models using optical indices including spectral slope coefficient (S275-295) and absorbance ratio (E2/E3) which are proxies for the abundance of singlet oxygen sensitizers and for the significance of intramolecular charge transfer interactions. The regression models can be potentially used to assess the photoactivity of DOM at large scales with in situ water spectrophotometry or satellite remote sensing.


Assuntos
Substâncias Húmicas/análise , Oxigênio Singlete/análise , Fuligem/análise , Luz Solar , Modelos Lineares , Peso Molecular , Imagens de Satélites , Solubilidade , Fuligem/química , Fuligem/efeitos da radiação , Espectrometria de Fluorescência
16.
Environ Pollut ; 226: 379-384, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28457734

RESUMO

The exposures of pharmaceutical antibiotics in water solution caused potential risks for ecological environment and human health. In the present study, porous covalent triazine frameworks (CTFs) were synthesized and the adsorption behavior of sulfamethoxazole (SMX) and tylosin (TL) was investigated. The CTFs were characterized by X-ray diffraction, transform infrared and N2 adsorption/desorption. Sulfamethoxazole displayed much stronger adsorption than tylosin on microporous CTF-1 adsorbent due to the pore-filling effect. While the adsorption of bulky tylosin on microporous CTF-1 was suppressed because of the size exclusion effect. Additionally, the porous CTFDCBP showed stronger adsorption affinity and faster adsorption kinetics than other porous adsorbents, which was attributed to wide pore size distribution and open pore structure. Findings in this study highlight the potential of using porous CTFs as a potential adsorbent to eliminate antibiotics from water, especially for selective adsorption of bulky molecular pollutant.


Assuntos
Antibacterianos/química , Triazinas/química , Poluentes Químicos da Água/química , Adsorção , Antibacterianos/análise , Cinética , Fatores de Transcrição NFI , Porosidade , Sulfametoxazol , Poluentes Químicos da Água/análise , Purificação da Água , Difração de Raios X
17.
Environ Sci Technol ; 51(12): 6877-6886, 2017 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-28510419

RESUMO

Cadmium pigments are widely used in the polymer and ceramic industry. Their potential environmental risk is under debate, being the major barrier for appropriate regulation. We show that 83.0 ± 0.2% of hazardous cadmium ion (Cd2+) was released from the commercial cadmium sulfoselenide pigment (i.e., cadmium red) in aqueous suspension within 24 h under simulated sunlit conditions. This photodissolution process also generated sub-20 nm pigment nanoparticles. Cd2+ release is attributed to the reactions between photogenerated holes and the pigment lattices. The photodissolution process can be activated by both ultraviolet and visible light in the solar spectrum. Irradiation under alkaline conditions or in the presence of phosphate and carbonate species resulted in reduced charge carrier energy or the formation of insoluble and photostable cadmium precipitates on pigment surfaces, mitigating photodissolution. Tannic acid inhibited the photodissolution process by light screening and scavenging photogenerated holes. The fast release of Cd2+ from the pigment was further confirmed in river water under natural sunlight, with 38.6 ± 0.1% of the cadmium released within 4 h. Overall, this study underscores the importance to account for photochemical effects to inform risk assessments and regulations of cadmium pigments which are currently based on their low solubility.


Assuntos
Cádmio , Resíduos Industriais , Nanopartículas , Cerâmica , Luz , Solubilidade , Luz Solar
18.
ACS Appl Mater Interfaces ; 9(22): 19335-19344, 2017 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-28498654

RESUMO

Supported Ni catalysts on three mesoporous SiO2 supports (i.e., SBA-15, MCM-41, and HMS) were prepared using a solid-state reaction between Ni(NO3)2 and organic template-occluded mesoporous SiO2. For comparison, supported Ni catalysts on mesoporous SiO2 synthesized by the conventional impregnation method were also included. The catalysts were characterized by scanning electron microscopy, X-ray diffraction, UV-vis diffuse reflectance spectroscopy, N2 adsorption, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, transmission electron microscopy, and transmission electron microscopy-energy-dispersive X-ray. The catalytic properties of the catalysts were evaluated using gas-phase catalytic hydrodechlorination of 1,2-dichloroethane. The results showed that upon grinding Ni(NO3)2 with template-occluded mesoporous SiO2, strong coordination between Ni2+ and dodecylamine was identified in the Ni(NO3)2-HMS system. Additionally, the results of H2 temperature-programmed reduction revealed that NiO in calcined NiO/HMS was reduced at higher temperature than those in calcined NiO/SBA-15 and NiO/MCM-41, reflecting the presence of a strong interaction between NiO and mesoporous SiO2 in NiO/HMS. Consistently, the average particle sizes of metallic Ni were found to be 2.7, 3.4, and 9.6 nm in H2-reduced Ni/HMS, Ni/SBA-15, and Ni/MCM-41, respectively, indicative of a much higher Ni dispersion in Ni/HMS. For the catalytic hydrodechlorination of 1,2-dichloroethane, Ni/MCM-41 synthesized by the solid-state reaction method exhibited a catalytic activity similar to that prepared by the impregnation method, while higher catalytic activities were observed on Ni/HMS and Ni/SBA-15 than on their counterparts prepared by the impregnation method. Furthermore, a higher conversion was identified on Ni/HMS than on Ni/SBA-15 and Ni/MCM-41, highlighting the importance of template type for the preparation of highly dispersed metal catalysts on mesoporous SiO2.

19.
Environ Pollut ; 216: 884-892, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27389552

RESUMO

Perfluoroalkyl acids (PFAAs) are highly stable, persistent, and ubiquitous in the environment with significant concerns growing with regards to both human and ecosystem health. Due to the high stability to both biological and chemical attack, the only currently feasible approach for their removal from water is adsorbent technology. The main objective of this study was to assess a covalent triazine-based framework (CTF) adsorbent for removal from aqueous solutions of perfluoro C4, C6, and C8 carboxylates and sulfonates including the two C8s most commonly monitored, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Adsorption affinity and capacity were quantified and compared to three commonly used sorbents: pulverized microporous activated carbon, single-walled carbon nanotubes, and Amberlite IRA-400 anion-exchange resin. CTF adsorbent exhibited pronouncedly higher adsorption affinity and capacity of PFAAs than other test sorbents. The remarkably strong adsorption to CTF can be attributed to the favored electrostatic interaction between the protonated triazine groups on the inner wall of the hydrophobic CTF pore and the negatively charged head groups of the PFAAs intercalated between the CTF layers. The homogeneous, nanosized pores (1.2 nm) of CTF hindered adsorption of a large-sized dissolved humic acid, thus minimizing the suppression of PFAA adsorption. Additionally, regeneration of CTF was easily accomplished by simply raising pH > 11, which inhibited the electrostatic adsorptive interaction of PFAAs.


Assuntos
Ácidos Alcanossulfônicos/análise , Caprilatos/análise , Carvão Vegetal/química , Fluorcarbonetos/análise , Nanotubos de Carbono/química , Triazinas/química , Poluentes Químicos da Água/análise , Adsorção , Humanos , Substâncias Húmicas/análise , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Microscopia Eletrônica de Transmissão , Modelos Teóricos , Propriedades de Superfície
20.
J Hazard Mater ; 308: 328-34, 2016 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-26852208

RESUMO

The toxicity of metal oxide nanoparticles (NPs) has aroused great concern over the past few years. However, there still remains the question whether the toxicity of the metal oxide NPs originates from the released ions or the NPs themselves. In this study, the metal ion release of CuO, Fe2O3, ZnO, Co3O4, Cr2O3, and NiO NPs in aqueous media was investigated, and their contributions to the metal oxide NPs' inhibition on the bioluminescence of Photobacterium phosphoreum were studied. It was found that the ions release of the metal oxide NPs in aqueous media was complex, depending on both the dissolution and adsorption processes of the metal oxide NPs. The relationships between the metal oxide NPs' antibacterial effects and their released metal ions could be divided into three categories: (1) the ZnO NPs' antibacterial effect was due solely to the released Zn(2+); (2) the CuO NPs' antibacterial effect originated from both the released Cu(2+),and the CuO particles; and (3) the antibacterial effects of Fe2O3, Co3O4, Cr2O3, and NiO NPs were caused by the NPs themselves. Our findings suggest that the ions release and their contributions to the NPs' toxicity should be considered in the toxicity evaluations of the metal oxide NPs.


Assuntos
Antibacterianos/toxicidade , Íons/toxicidade , Nanopartículas Metálicas/toxicidade , Metais/toxicidade , Óxidos/toxicidade , Poluentes Químicos da Água/toxicidade , Adsorção , Antibacterianos/química , Hidrólise , Íons/química , Luminescência , Nanopartículas Metálicas/química , Metais/química , Óxidos/química , Photobacterium/efeitos dos fármacos , Photobacterium/metabolismo , Solubilidade , Poluentes Químicos da Água/química
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