Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 2.470
Filtrar
1.
J Photochem Photobiol B ; 203: 111774, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31931386

RESUMO

Zeolitic imidazole framework (ZIF) is an emerging class of metal organic frameworks exhibiting unique features such as crystalline nature with tunable pore size, large surface area and biocompatible nature. Exceptional thermal and chemical stabilities of ZIF-L make it a suitable candidate for biomedical applications. The present study has focused on the single step fabrication of catechin encapsulated ZIF-L and evaluation of its antibiofilm efficiency, larvicidal activity and dye degradation ability. The as- prepared CA@ZIF-L nanocomposite was characterized by spectroscopic and microscopic techniques. The results revealed that the CA@ZIF-L showed significant toxicity against mosquito larvae in a dose dependent manner with the IC50 63.43±1.25 µg/mL. CA@ZIF-L showed dose dependent reduction of biofilm formation in both ATCC and clinical MRSA strains. In addition, CA@ZIF-L exhibited excellent photocatalytic activity with around 92% degradation of methylene blue under direct sunlight. Overall, the present work highlights the possibility of employing the multifunctional CA@ZIF-L nanocomposite as a suitable material for biomedical and photocatalytic applications.


Assuntos
Biofilmes/efeitos dos fármacos , Catequina/química , Estruturas Metalorgânicas/química , Nanocompostos/toxicidade , Zeolitas/química , Animais , Catálise , Culicidae/efeitos dos fármacos , Culicidae/crescimento & desenvolvimento , Imidazóis/química , Larva/efeitos dos fármacos , Luz , Staphylococcus aureus Resistente à Meticilina/fisiologia , Azul de Metileno/química , Nanocompostos/química , Tamanho da Partícula , Fotólise/efeitos da radiação
2.
Chemosphere ; 241: 124981, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31606579

RESUMO

Photocatalytic degradation of toxic pollutants is an efficient technique to completely remove the toxic pollutants from water bodies. In the present investigation, photocatalytic degradation of pollutants was studied over porous g-C3N4/H-ZSM-5 nanocomposite under visible light irradiation. The composite g-C3N4/H-ZSM-5 was synthesized by mixing an aqueous solution of H-ZSM-5 zeolite (increases surface area and provides active sites for degradation) with melamine (precursor of g-C3N4) for 10-12 h followed by calcinations at 550 °C. The photocatalyst was characterized by XRD, BET, HRTEM, FESEM, EDS and elemental mapping analysis. These techniques confirmed that, g-C3N4/H-ZSM-5 composite have layered and porous structure with uniform distribution of g-C3N4 on H-ZSM-5 surface. The BET N2 adsorption-desorption analysis verified that the catalyst has high surface area (∼175 m2/g) having mesopores and micropores. The prepared catalyst was then used for the photodegradation of a model dye, Methylene Blue (MB) and an endocrine disrupting compound, Fipronil (FIP). Effects of various parameters such as pH, catalyst dose and scavengers were also studied. The % photocatalytic degradation of MB and FIP were around ∼92% and ∼84% with a high rate constants of 0.00997 and 0.00875 min-1, respectively. From the scavenger study, OH (hydroxyl radical) and radical was found to be the major reactive species for MB and FIP degradation. From these studies it is revealed that, the catalyst is visible active, easy to prepare and an efficient photocatalyst for toxic pollutant degradation.


Assuntos
Disruptores Endócrinos/química , Luz , Nanocompostos/química , Fotólise , Zeolitas/química , Adsorção , Catálise , Disruptores Endócrinos/efeitos da radiação , Azul de Metileno/química , Microscopia Eletrônica de Transmissão , Porosidade
3.
Sci Total Environ ; 704: 135260, 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-31780159

RESUMO

How to achieve stable nitrite accumulation was still a huge challenge for low-carbon and energy-saving biological nitrogen removal of low-strength ammonium wastewater. This study proposed a new way to solve this problem with zeolite biological fixed bed (ZBFB) by cycle operation of adsorption and biological desorption. In order to evaluate nitritation performance of this reactor, the influence of operational temperature on nitrite accumulation stability was investigated by 126 cycles operation in four parallel ZBFB reactors for low-strength ammonium wastewater (50 mg/L NH4+-N). It was found that higher operational temperature (i.e., 36.0 °C), rather than other temperature (i.e., 27.0 °C, 30.0 °C, 33.0 °C), could maintain stable nitrite accumulation with nitrite production rate of 0.312 kg NO2--N·m-3 zeolite·day-1 and nitrite accumulation ratio higher than 95.0% after biological desorption. High-throughput sequencing analysis results showed that bacterial structure significantly changed in ZBFB under different operational temperature, and obvious enrichment of genus Nitrosomonas (AOB) and gradually enhanced free ammonia (FA) inhibition on genus Nitrospira and Nitrobacter (NOB) were found by elevation of operational temperature, leading to different nitrite accumulation performance in ZBFB reactors. The mechanism for stable nitrite accumulation performance by ZBFB might be attributed to overwhelming growth rate of AOB than NOB, faster ammonium desorption and enhanced FA inhibition on NOB under operational temperature (i.e., 36.0 °C). All in all, keeping high temperature for biological desorption step should be extremely crucial for stable nitrite accumulation by ZBFB, which could facilitate further low-carbon and energy-saving biological nitrogen removal for low-strength ammonium wastewater treatment.


Assuntos
Compostos de Amônio/análise , Nitritos/análise , Eliminação de Resíduos Líquidos/métodos , Adsorção , Amônia , Bactérias , Biofilmes , Reatores Biológicos , Nitrobacter , Nitrogênio , Temperatura Ambiente , Águas Residuárias/química , Zeolitas/química
4.
Ecotoxicol Environ Saf ; 188: 109887, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31706237

RESUMO

To investigate the removal mechanisms of cadmium (Cd) by Zn-layer double hydroxides-modified zeolites substrates in constructed rapid infiltration systems (CRIS), the ZnAl-LDHs and ZnFe-LDHs were synthesized and in-situ coated on the original zeolites through co-precipitation method. The prepared Zn-LDHs-modified and original zeolites were characterized by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) methods, whose results provided the evidences that the Zn-LDHs were successfully coated on the original zeolites. From the results of purification experiments, the average Cd removal rates of ZnAl-LDHs-modified, ZnFe-LDHs-modified and original zeolites were 88.40, 86.00 and 32.52%, respectively; demonstrating that the removal rates of zeolites could significantly improve. Additionally, the modification of Zn-LDHS could enhance the theoretical adsorption ability. According to the results of isothermal adsorption and desorption tests, the desorption rates of Zn-LDHs-modified zeolites were higher than that of original zeolites. Cd adsorption capacity of ZnFe-LDHs-modified zeolites was 1428.57 mg kg-1 and original zeolites was 434.783 mg kg-1. In the adsorption kinetic studies, the pseudo-second-order models were used to well describe the experimental results of Zn-LDHs-modified zeolites, indicating that their adsorption types were attributed to be more stable chemisorption. Besides, the relevant microbial tests also confirmed that microbial enzymatic activity and extracellular polymeric substances (EPS) were significantly promoted on surface of Zn-LDHs-modified zeolites. The contents of EPS on the surface of zeolites were as following: ZnAl-LDHs-modified zeolites (78.58128 µg/g) > ZnFe-LDHs-modified zeolites (71.85445 µg/g) > original zeolites (68.69904 µg/g). Meanwhile, the results of high-throughput sequencing showed that modification by Zn-LDHs improved microbial diversity and relative abundance. The Proteobacteria was the dominant phylum and the Acidobacteria was conducive to Cd removal. Overall, it could be concluded that ZnAl-LDHs-modified zeolites might be applied as an efficient substrate for Cd removal in CRIS.


Assuntos
Cádmio/isolamento & purificação , Hidróxidos/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Zeolitas/química , Zinco/química , Acidobacteria/química , Acidobacteria/metabolismo , Adsorção , Proteínas de Bactérias/metabolismo , Cádmio/química , Cinética , Poluentes Químicos da Água/química , Purificação da Água/instrumentação , Purificação da Água/normas
5.
J Appl Microbiol ; 128(1): 202-208, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31536673

RESUMO

AIMS: Fibre membranes containing metals have attracted great attention because of their high antibacterial efficiency. However, comparison of antibacterial activity of fibres with multi-metals in air samples has remained understudied. METHODS AND RESULTS: Different ion exchanged nano-zeolite Y (IE-NZY) of Ag, Zn and Cu was studied. Polyvinylpyrrolidine/polyvinylidene fluoride nanofibres containing various IE-NZY were synthesized according to electrospinning technique. The presence of metal ions was confirmed using XRF. The morphological properties of nanofibres were characterized by SEM. Zone of inhibition was seen between 10·1 and 12 mm against Staphylococcus aureus and 11·5-14·57 for Escherichia coli. IE-NZY containing Ag, Zn and Cu had the highest antibacterial efficiency. In the air samples, there were any colonies on the media under the Ag/Cu-NZY and Zn/Cu/Ag-NZY nanofibres. CONCLUSIONS: The bacterial inhibition for nanofibres containing a three metal nano-zeolite Y (TM-NZY) is higher than bimetals (BM-NZY) types while for monometals nano-zeolite Y (MM-NZY), it was lower compared to the others. SIGNIFICANCE AND IMPACT OF THE STUDY: The results indicate significant antibacterial activity of ion-exchanged NZY in air sampling.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Metais/química , Zeolitas/química , Zeolitas/farmacologia , Antibacterianos/síntese química , Cobre/química , Cobre/farmacologia , Escherichia coli/efeitos dos fármacos , Metais/farmacologia , Testes de Sensibilidade Microbiana , Nanofibras/química , Nanofibras/ultraestrutura , Prata/química , Prata/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Zinco/química , Zinco/farmacologia
6.
Environ Sci Pollut Res Int ; 26(35): 35913-35923, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31707609

RESUMO

Mixed matrix membranes (MMMs) provide a unique pathway to treat hazardous industrial effluents. MMMs containing zeolitic imidazolate framework-8 (ZIF-8) as filler in polydimethoxysilane (PDMS) matrix were synthesized. ZIF-8 was prepared using a modified recipe and characterized by different techniques to evaluate its morphology, thermal stability, surface area, pore volume, and other characteristics. The performance of membranes was evaluated for their application in industrial dye-stuff wastewater treatment and solvent-resistant nanofiltration. The results demonstrated that increase in the percentage of ZIF-8 loading in PDMS led to simultaneous increase in the solvent permeability as well as solute rejection from wastewater. The permeability of MMMs increased up to 32% as compared with neat PDMS membrane. The organic dye rejection was achieved more than 87% with MMMs incorporated with 20% loading of nanofillers. Rejection of MMMs was 22% higher than that of unfilled PDMS membrane due to the effect of reduced polymer swelling and size exclusion of the nanofillers. Membrane swelling tests with toluene and isopropanol demonstrated that nanofiller amount has inverse relation with membrane swelling, which implied that nanofillers were in good interaction with polymer and allowed defect free membranes with higher solute rejections and reduced membrane swelling.


Assuntos
Substâncias Perigosas/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Substâncias Perigosas/análise , Membranas Artificiais , Permeabilidade , Polímeros , Sonicação , Águas Residuárias , Poluentes Químicos da Água/análise , Zeolitas/química
7.
Environ Sci Pollut Res Int ; 26(36): 36845-36856, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31745796

RESUMO

This study investigated the impact of adding zeolite (F), superphosphate (G), and ferrous sulfate (L) in various combinations on reducing greenhouse gas (GHG) emission and improving nitrogen conservation during factory-scale chicken manure composting, aimed to identify the combination that optimizes the performance of the process. Chicken manure was mixed with F, G, FL, or FGL and subjected to windrow composting for 46 days. Results showed that global warming potential (GWP) was reduced by 21.9% (F), 22.8% (FL), 36.1% (G), and 39.3% (FGL). Further, the nitrogen content in the final composting product increased by 27.25%, 9.45%, and 21.86% in G, FL, and FGL amendments, respectively. The fertilizer efficiency of the compost product was assessed by measuring the biomass of plants grown in it, and it was consistent with the nitrogen content. N2O emission was negligible during composting, and 98% of the released GHGs comprised CO2 and CH4. Reduction in GHG emission was mainly achieved by reducing CH4 emission. The addition of FL, G, and FGL caused a clear shift in the abundance of dominant methanogens; particularly, the abundance of Methanobrevibacter decreased and that of Methanobacterium and Methanocella increased, which was correlated with CH4 emissions. Meanwhile, the changes in moisture content, NH4+-N content, and pH level also played an important role in the reduction of GHG emission. Based on the effects of nitrogen conservation, fertilizer efficiency improvement, and GHG emission reduction, we conclude that G and FGL are more beneficial than F or FL and suggest these additives for efficient chicken manure composting.


Assuntos
Compostagem , Difosfatos/química , Fertilizantes/análise , Gases de Efeito Estufa/análise , Esterco , Zeolitas/química , Animais , Galinhas , Aquecimento Global , Metano/análise , Nitrogênio/análise , Óxido Nitroso/análise , Solo
8.
Molecules ; 24(19)2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31581744

RESUMO

Obtaining enantiomerically-enriched photoproducts from achiral reactants has been a long-sought goal. The various methods developed to achieve chiral induction in photoproducts during the last fifty years still suffer from a lack of predictability, generality, and simplicity. With the current emphasis on green chemistry, obtaining enantiomerically enriched products via photochemistry is a likely viable alternative for the future. Of the various approaches developed during the last three decades, the one pioneered in the author's laboratory involved the use of commercially-available and inexpensive achiral zeolites as the media. This approach does not use any solvent for the reaction. Examples from these studies are highlighted in this article. Since no chiral zeolites were available, when the work was initiated in the author's laboratory, commercially-available zeolites X and Y were modified with chiral inductors so that the reaction space becomes chiral. The results obtained established the value of chirally-modified, commercial zeolites as media for achieving chiral induction in photochemical reactions. A recent report of the synthesis of a chiral zeolite is likely to stimulate zeolite-based chiral photochemistry in synthesizing enantiomerically-pure organic molecules. The availability of chiral zeolites in future is likely to energize research in this area. Our earlier observations on this topic, we believe, would be valuable for progress of the field. Keeping this in mind, I have summarized the work carried out in our laboratory on chiral photochemistry on chirally-modified zeolites. This review does not include examples where high chiral induction has been obtained via a strategy that examines molecules appended with chiral auxiliary within achiral and chirally-modified zeolites. The latter approach yields products with diastereomeric excess >80%.


Assuntos
Química Verde/métodos , Zeolitas/química , Cristalização , Processos Fotoquímicos , Estereoisomerismo
9.
Chem Commun (Camb) ; 55(85): 12869-12872, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31599274

RESUMO

A hierarchical USY zeolite has been produced using the surfactant-templating method and used as a catalyst for the production of two important active pharmaceutical ingredients. The presence of intracrystalline mesoporosity in the zeolite results in a significant increase in both the activity (up to 30 fold increase in TOF) and reusability for Friedel-Crafts alkylation and aldol condensation steps.


Assuntos
Nanoestruturas/química , Preparações Farmacêuticas/química , Tensoativos/química , Zeolitas/química , Catálise
10.
Environ Sci Pollut Res Int ; 26(32): 33478-33493, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31529345

RESUMO

In this paper, the adsorption behavior of zinc onto magnetic zeolite/cellulose nanofibers (MZNF) was studied. The prepared adsorbent was characterized by SEM, FTIR, and VSM analyses. The mass ratio of adsorbent in composite, pH, contact time, adsorbent dosage, initial Zn+2 concentration, temperature, and agitation speed were investigated in batch experiments. The results showed that zeolite played an important role in the prepared nanocomposite due to its great surface area. pH 7 exhibited the highest Zn+2 removal efficiency. Rapid adsorption at the first 30 min of the reaction is one of the advantages of the prepared adsorbents. Moreover, increase at temperature led to higher efficiency and maximum efficiency was attained at 30 °C. Under optimum conditions, MZNF showed removal efficiency of 96% and maximum adsorption capacity of 9.45 mg/g. The presence of the competing ions did not reduce the efficiency of the process and adsorption efficiency was higher than 93%. The calculated RSD of 1.42% exhibits the suitability of the process. Equilibrium data were examined by various isotherms and kinetics equations. It was concluded that Pseudo second-order model and Langmuir models described the adsorption process well. Based on these results, MZNF obtained in this work can be served as a promising candidate for Zn+2 removal in wastewater.


Assuntos
Poluentes Químicos da Água/química , Zinco/química , Adsorção , Celulose , Concentração de Íons de Hidrogênio , Íons/análise , Cinética , Fenômenos Magnéticos , Magnetismo , Modelos Químicos , Nanocompostos/química , Nanofibras , Temperatura Ambiente , Termodinâmica , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Zeolitas/química , Zinco/análise
11.
ACS Appl Mater Interfaces ; 11(39): 36081-36089, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31508936

RESUMO

Anthrax spores have been a determining risk to human beings and animals across the world. As such, the qualitative monitoring toward dipicolinic acid (DPA), the unique biomarker of bacillus anthracis, is highly desired and being moved forward in health management. Herein, a breathing zeolite-like supramolecular assembly (ZSA), with the sra topology and 1D hexagon channel, is designed by controlling the bridging angle of the ditopic ligand after systematic analysis in topology. The solvent-dependent dynamic behavior is illustrated by powder X-ray diffraction and reflected in tunable luminescent emission based on solvent polarity parameters. According to the structural result and theoretical analysis, Eu3+ is anchored within the framework to form a ratiometric luminescent sensor successfully because of the abundant potential active site. After DPA addition, the resulting composite shows a sensitive and selective response in the linear range of 0-7.0 µM stemmed from absorbance energy-transfer emission and preferential coordination. The work we presented here may enrich the sensing platforms containing lanthanides and expand the potential application of ZSAs in clinical analysis.


Assuntos
Antraz/diagnóstico , Bacillus anthracis , Európio/química , Medições Luminescentes , Ácidos Picolínicos/análise , Zeolitas/química , Biomarcadores
12.
Environ Sci Pollut Res Int ; 26(32): 32928-32941, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31512128

RESUMO

In this study, MgAl-LDHs and MgFe-LDHs were synthesized via co-precipitation method and in situ coated on pre-washed zeolites through dipping process in beaker. The obtained modified zeolites and original zeolites were utilized as substrates of constructed rapid infiltration systems (CRIS) to remove hexavalent chromium (Cr(VI)) in wastewater. Micro-morphology features and chemical composition of zeolites before and after modification were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray fluorescence spectrometer (XRF). The SEM, XRD, and XRF results demonstrated the feasibility of LDHs coated on the surface of the original zeolites. Purification experiments in simulated CRIS showed that the Cr(VI) removal rates of zeolites/MgAl-LDHs increased by 110.03% on average every concentration (0.5-16 mg L-1) compared with the original zeolites under 24-h HRT. The adsorption capacity of zeolites/MgAl-LDHs reached 66.98 mg kg-1 at 32 mg L-1 initial Cr(VI) concentration, which is nearly twice that of the original zeolites (33.24 mg kg-1) and 1.5 times higher than that of zeolites/MgFe-LDHs (42.01 mg kg-1). Isothermal adsorption tests showed that the Freundlich isotherm equations gave better fitting to the adsorption process. And zeolites/MgAl-LDHs showed a best fit with pseudo-second-order model which meant that the adsorption of Cr(VI) by zeolites/MgAl-LDHs was dominated by chemisorption. Thermodynamic parameters showed that the process of adsorption for the three substrates was spontaneous and endothermic intrinsically. Zeolites/MgAl-LDHs also displayed nearly 60% desorption rate with low concentration eluent (0.01 mol L-1 NaCl). Therefore, zeolites/MgAl-LDHs were chosen out as an optimal substrate for removing Cr(VI) from wastewater in CRIS. Graphical Abstract.


Assuntos
Cromo/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Zeolitas/química , Adsorção , Cromo/química , Cinética , Hidróxido de Magnésio/química , Microscopia Eletrônica de Varredura , Espectrometria por Raios X , Termodinâmica , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Poluentes Químicos da Água/química , Difração de Raios X
13.
ACS Appl Mater Interfaces ; 11(40): 36347-36358, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31525886

RESUMO

Photodynamic therapy (PDT) has been introduced as a photochemical process for treatment by causing cancer cell death and necrosis, with higher accuracy and few side effects. However, the hydrophobicity of most photosensitizers and hypoxia at the tumor sites are two crucial problems to be solved to achieve a successful PDT. Herein, we designed and constructed a novel metal-organic framework-based drug delivery system (BSA-MnO2/Ce6@ZIF-8) with tumor microenvironment controllability. In our system, the hydrophobic photosensitizer chlorin e6 (Ce6) was one-pot incorporated into the matrix of zeolitic imidazolate framework 8 (ZIF-8) to form the Ce6@ZIF-8 compound, which can efficiently keep the Ce6 molecules isolated and avoid them self-aggregate, and the loading rate of Ce6 was high up to 28.3 wt %. The bovine serum albumin (BSA)-MnO2 nanoparticles (NPs) with catalase-like activity were loaded onto the surface of ZIF-8, having the capacity for self-sufficiency of O2 under the circumstance of H2O2 in acid solution, relieving hypoxia in cancer cells and thereby improving the PDT efficiency greatly when irradiated by low power density (230 mW/cm2) 650 nm light. Moreover, the MnO2 NPs react with H2O2 in acid solution to produce Mn2+, granting the system the qualification of a contrast agent for magnetic resonance imaging. Therefore, our nanoplatform would further contribute to the treatment of hypoxic tumors in clinical practice.


Assuntos
Sistemas de Liberação de Medicamentos , Interações Hidrofóbicas e Hidrofílicas , Estruturas Metalorgânicas/química , Oxigênio/análise , Fotoquimioterapia , Fármacos Fotossensibilizantes/administração & dosagem , Animais , Catalase/metabolismo , Células HeLa , Humanos , Imagem por Ressonância Magnética , Camundongos , Oxirredução , Porfirinas/administração & dosagem , Zeolitas/química
14.
Molecules ; 24(19)2019 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-31554209

RESUMO

A general strategy for preparing shaped toluene methylation catalysts with enhanced para-selectivity and stability is developed by extruding ZSM-5 zeolite with attapulgite as a binder. The novel attapulgite/ZSM-5 extrudate exhibited significantly higher para-selectivity and stability in comparison to the conventional alumina-bound ZSM-5 extrudate. The catalyst samples have been characterized by in situ X-ray diffraction, scanning electron microscope (SEM), NH3 temperature programmed desorption (TPD), thermogravimetric analysis (TGA) as well as n-hexane/cyclohexane physical adsorption. The enhanced catalytic performance of attapulgite/ZSM-5 extrudate is correlated with the in-situ modification of acid sites in the catalyst by mobile alkaline species, which is introduced via extrusion with attapulgite. Moreover, a higher para-selectivity was obtained over attapulgite-bound modified ZSM-5 extrudate. Such facile and universal strategy of extruding ZSM-5 catalysts with attapulgite as binder could pave a way for preparation of shaped zeolite-base catalyst with enhanced catalytic performance.


Assuntos
Tolueno/química , Xilenos/química , Zeolitas/química , Adsorção , Catálise , Compostos de Magnésio/química , Metilação , Compostos de Silício/química , Difração de Raios X
15.
Environ Pollut ; 255(Pt 2): 113119, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31546080

RESUMO

The aim of this work was to develop a new modified graphite felt (GF) as carbonaceous cathode for electro-Fenton (EF) application loaded with nitrogen-doped porous carbon (NPC) carbonized by zeolitic imidazolate framework-8 (ZIF-8) nanocrystals as carbon precursor. At initial pH 7, the highest generation rate of H2O2 was 0.74 mg h-1 cm-2 by applying 12.5 mA cm-2 by modified cathode, but in the same condition, the GF only had 0.067 mg h-1 cm-2. The production efficiency increased 10 times. Additionally, phenol (50 mg L-1) could be largely removed by NPC modified cathode, the mineralization ratio and TOC reached 100% and 82.61% at 120 min of optimization condition, respectively. The NPC cathode kept its stability after 5 cycles. The materials were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and linear sweep voltammetry (LSV). The results demonstrated that a homogenous NPC covered the carbon-based material GF. The existing graphitic-N and sp2 carbon of NPC promoted the electron transfer between carbon surface and oxygen molecules, as well as accelerated the oxygen reduction reaction (ORR) and the modified graphite felt had much higher electrocatalytic activity. In this work, several manufacturing parameters like the current, pH and load of NPC were optimized. The optimized design could improve the efficiency of new cathode with in situ electro-chemical production of H2O2 and significantly offer a potential material for degradation of organic pollutants.


Assuntos
Grafite/química , Peróxido de Hidrogênio/química , Zeolitas/química , Carbono , Eletrodos , Modelos Químicos , Nanopartículas , Nitrogênio , Porosidade
16.
Artigo em Inglês | MEDLINE | ID: mdl-31499294

RESUMO

The ionic liquid (IL) was introduced to the synthesis system of magnetic zeolite imidazolate framework-8 (M/ZIF-8), which was benefit to the formation of binary imidazole and the co-modification of M/ZIF-8. The morphology and textural properties of ILM/ZIF-8 were characterized by SEM, TEM, BET and BJH. The crystal structural shape and size of MZIF-8 was unvaried with the interventional of IL. The ILM/ZIF-8 was applied to the concentration and determination of aflaoxins (AFB1, AFB2, AFG1 and AFG2) in milk samples based on magnetic solid phase extraction (MSPE) coupled with ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The experimental parameters of the MSPE, including amount of ILM/ZIF-8, pH, type and amount of desorption solvent, extraction time and sample volume were investigated by a univariate method and orthogonal screening. The four AFs were concentrated from the 20 mL milk when 90 mg ILM/ZIF-8 was used as magnetic adsorbent. The extraction efficiency of AFs was higher than 80.0% within 15 min. The limits of quantitative and detection were 7.5-26.7 and 2.3-8.1 ng/L, respectively. The proposed method was applied to the determination of milk samples containing trace amounts of AFs and the recoveries ranged from 79.0% to 102.5%, with RSD below 7.7%.


Assuntos
Aflatoxinas/análise , Nanopartículas de Magnetita/química , Leite/química , Extração em Fase Sólida/métodos , Zeolitas/química , Animais , Cromatografia Líquida de Alta Pressão/métodos , Imidazóis/química , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes , Espectrometria de Massas em Tandem/métodos
17.
Mater Sci Eng C Mater Biol Appl ; 104: 109943, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500025

RESUMO

The main objective of this work was to reduce the inhibitory effects of high contents of organics, ammonia, and heavy metals in an anaerobic buffled reactor (ABR), and to prevent the sludge wash-out using zeolites as media. In this work, a pilot scale of ABR with 8 compartments and a working volume of 14.4 L was used, and the last four ABR compartments were filled with a zeolite. The bioreactor was operated at HRTs of 3, 4, and 5 days, zeolite filling ratios of 10, 20, and 30%, and influent chemical oxygen demand (COD) concentrations of 10,000, 20,000, and 30,000 mg/L. The results obtained showed that the maximum removal efficiencies of COD and BOD5 reached 78 and 68%, respectively. The maximum removal was observed at a HRT of 5 days, a 30% medium filling ratio, and a COD of 10,000 mg/L. Increasing the filling ratio in the reactor increased the removal efficiencies of COD and BOD5 but increasing the concentration of the influent COD and decreasing HRT reduced the removal efficiency of the reactor. The initial BOD5/COD ratio was equal to 0.36, which increased by 46% when the medium filling ratio was elevated to 30%. The maximum biogas yield was 0.23 L/g of CODRemoved, and the specific methanogenic activity test verified the toxicity effect of the leachate on the gas-producer organisms. The results of scanning electronic microscopy and EDS showed that the zeolite medium immobilized the microorganisms and a biofilm was formed. Also the zeolite, as a well-known ion exchanger, decreased the concentrations of the major inhibitors (ammonia and heavy metals) and improved the reactor efficiency.


Assuntos
Anaerobiose/efeitos dos fármacos , Biodegradação Ambiental/efeitos dos fármacos , Zeolitas/química , Amônia/química , Biofilmes/efeitos dos fármacos , Biocombustíveis , Análise da Demanda Biológica de Oxigênio/métodos , Reatores Biológicos , Metais Pesados/química , Oxigênio/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química
18.
J Synchrotron Radiat ; 26(Pt 5): 1769-1781, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31490169

RESUMO

Two in situ `nanoreactors' for high-resolution imaging of catalysts have been designed and applied at the hard X-ray nanoprobe endstation at beamline P06 of the PETRA III synchrotron radiation source. The reactors house samples supported on commercial MEMS chips, and were applied for complementary hard X-ray ptychography (23 nm spatial resolution) and transmission electron microscopy, with additional X-ray fluorescence measurements. The reactors allow pressures of 100 kPa and temperatures of up to 1573 K, offering a wide range of conditions relevant for catalysis. Ptychographic tomography was demonstrated at limited tilting angles of at least ±35° within the reactors and ±65° on the naked sample holders. Two case studies were selected to demonstrate the functionality of the reactors: (i) annealing of hierarchical nanoporous gold up to 923 K under inert He environment and (ii) acquisition of a ptychographic projection series at ±35° of a hierarchically structured macroporous zeolite sample under ambient conditions. The reactors are shown to be a flexible and modular platform for in situ studies in catalysis and materials science which may be adapted for a range of sample and experiment types, opening new characterization pathways in correlative multimodal in situ analysis of functional materials at work. The cells will presently be made available for all interested users of beamline P06 at PETRA III.


Assuntos
Catálise , Ciência dos Materiais/instrumentação , Microscopia Eletrônica , Elétrons , Desenho de Equipamento , Ouro/química , Síncrotrons , Temperatura Ambiente , Raios X , Zeolitas/química
19.
J Environ Sci (China) ; 85: 177-188, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31471025

RESUMO

The effect of preparation parameters on the performance of zeolite for ammonium (20-300 mg N/L) adsorption from simulated wastewater is reported. It was found that the ratios of Na2O/SiO2 and Si/Al had a more important influence than crystallization time on zeolite adsorption properties. Relatively low Na2O/SiO2 ratios were beneficial for fabrication of zeolites with high proportions of micropore area and volume, which led to the surface adsorption mechanism being dominated by surface free energy and pore effects. However, with decreasing Si/Al ratios, the effect of ion-exchange was more prominent due to the high negative surface potential of zeolite. In addition, the concentration of weak acid sites on the zeolites was increased with lower ratios of Na2O/SiO2 and Si/Al, which may promote ammonium removal. Therefore, the most effective zeolite for ammonium removal, which was fabricated at Na2O/SiO2 = 1.375, Si/Al = 4 and crystallization time of 48 hr, exhibited the cooperative effects of adsorption, ion-exchange and a large amount of weak acid sites. The maximum ammonium adsorption capacity (35.06 ±â€¯0.98 mg/g) and the removal efficiency (94.44% ±â€¯4.00%) were obtained at the dosage of 4.0 g/L zeolite NaX at ammonium concentrations of 300 mg N/L and 20 mg N/L, respectively. The Freundlich isotherm and pseudo-first-order kinetics models provided excellent fitting for the ammonium adsorption process. In addition, zeolite NaX showed about 1.23-3.2 times the ammonium adsorption capacity of clinoptilolite. The stable and efficient reusability of zeolite NaX after five regeneration cycles demonstrated that this adsorbent has considerable potential for practical industrial applications.


Assuntos
Compostos de Amônio/química , Modelos Químicos , Zeolitas/química , Adsorção
20.
Molecules ; 24(17)2019 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-31484400

RESUMO

We report a varying temperature infrared spectroscopic (VTIR) study with partial deuterium isotopic exchange as a method for characterizing proton mobility in acidic materials. This VTIR technique permits the estimation of activation energies for proton diffusion. Different acidic materials comprising classical proton-conducting materials, such as transition metal phosphates and sulfonated solids, as well as different zeolites, are tested with this new method. The applicability of the method is thus extended to a vast library of materials. Its underlying principles and assumptions are clearly presented herein. Depending on the temperature ranges, different activation energies for proton transfer are observed irrespective of the different materials. In addition to the well-studied transition metal phosphates, Si-rich zeolites appear to be promising proton-transfer materials (with Eact < 40 kJ mol-1) for application in high-temperature (>150 °C) PEM fuel cells. They significantly outperform Nafion and sulfonated silica, which exhibit higher activation energies with Eact ~ 50 and 120 kJ mol-1, respectively.


Assuntos
Espectrofotometria Infravermelho/métodos , Zeolitas/química , Adsorção , Prótons , Temperatura Ambiente
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA