Zeolite Fibers Research Articles

Potential Toxicity of Natural Fibrous Zeolites: In Vitro Study Using Jurkat and HT22 Cell Lines

An emerging problem for human health is the exposure to non-regulated mineral fibers with an asbestos-like crystal habit, particularly fibrous zeolites. This study aimed to determine if and how selected fibrous zeolites (erionite, mesolite, and thomsonite) induce toxicity effects on two different in vitro cellular models, the adherent murine hippocampal (HT22) and human immortalized T lymphocyte (Jurkat) cell lines. Before proceeding with the cellular tests, the three zeolite samples were investigated using scanning electron microscopy–energy-dispersive spectroscopy and X-ray powder diffraction techniques. The cells were treated with 0.1 µM and 1 µM of fibrous erionite, mesolite, and thomsonite for 12, 24, and 48 h. Results showed a cytotoxic effect of erionite in both cellular models and revealed different toxic behaviors of the mesolite and thomsonite fibers, suggesting other potential mechanisms of action. The outcome of this study would be a first step for further research on fine biochemical interactions of zeolite fibers with cells and future in vivo investigations.

Effect of the Thermal Etching Temperature and SiO2/Al2O3 Ratio of Flexible Zeolite Fibers on the Adsorption/desorption Characteristics of Toluene

Effect of the Thermal Etching Temperature and SiO2/Al2O3 Ratio of Flexible Zeolite Fibers on the Adsorption/desorption Characteristics of Toluene

High surface area flexible zeolite fibers based on a core-shell structure by a polymer surface wet etching process

Flexible zeolite fibers based on a core-shell fiber structure were prepared by an electrospinning method, and then the surface of the as-spun fiber was partially etched by a wet etching process. Zeolite porous ceramic particles were embedded in the core-shell fiber structure of poly(vinylidene fluoride) (PVDF)/polyvinylpyrrolidone (PVP), and the adsorption sites of the zeolite began to be exposed by partially wet etching of the hydrophilic PVP polymer in the shell parts. The specific surface area increased significantly by exposing the adsorption sites of the zeolite on the surface, and at the same time, flexibility and strength were maintained by the existing hydrophobic PVDF polymer acting as a skeleton. The morphology of the partially etched surface of the flexible zeolite fibers was observed by field-emission scanning electron microscopy (FE-SEM) and atomic force microscope (AFM), and the specific surface area was measured by N2 adsorption/desorption isotherm. The improved adsorption/desorption characteristics of the flexible zeolite fiber filters were observed by gas chromatography (GC).

The preparation and analysis of ceramic fibers with deposited catalytic particles by plasma technology

In this work, the ceramic micro- and nanofibers were formed using atmospheric pressure thermal plasma reactor. The catalytic (copper, titanium) particles and their mixtures were deposited on the surface of zeolite fibers during their formation. The prepared catalytic fibers were analyzed using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), BET (Brunauer–Emmett–Teller) surface area measurements and Energy-dispersive X-ray spectroscopy (EDS). The SEM analysis showed that the obtained fiber diameters are in the range from 10 μm to few hundred nanometers. Some of the catalytic particles were deposited without changes and some were melted or burst. The XRD analysis showed that the zeolite fiber without the catalytic particles is amorphous as there are no crystal phase peaks. After the deposition of catalytic particles the peaks of the catalytic metals and their oxides appear. The BET method showed that the surface area of the catalytic fiber is 13-18 m2/g. The EDS analysis showed that the quantity of catalytic particles in the catalytic fiber is 7-18 %.

Hierarchical nano zeolite-Y hydrocracking composite fibers with highly efficient hydrocracking capability.

In this work, a hydrocracking catalyst, nano zeolite Y-NiO-WO3 is reshaped into nanofibrous form. This novel composite fiber show good mechanical strength together with a uniform elemental distribution for both the acidic and hydrogenation components as confirmed through scanning transmission electron microscopy. The catalyst is tested for n-heptane hydrocracking in a continuous flow fixed-bed reactor at reaction temperatures of 350 °C and 400 °C with a time on stream of 180 minutes. The fibers produced from nano zeolite-Y show superior performance with a total conversion of 98.81 wt% and 96.8 wt% at 350 °C and 400 °C respectively. In addition, a low amount of coke (0.40 wt% and 1.05 wt% at 350 °C and 400 °C respectively) was formed with the nano zeolite Y fibers. This superior performance is related to the enhanced accessibility due to the nanofiber shape where the non-woven mesh/network of catalytic fibers prevents the agglomeration of the nanoparticles. Agglomeration is a major cause of hindered accessibility of the reactants to the catalyst active sites. The zeolite particle size, and the shape of the fibrous catalyst, together with its mesoporous character (as confirmed through BET analysis) enhances diffusion and improves accessibility for the reactants to react on the catalytic active sites as proven by the high total n-heptane conversions and high hexane and iso hexane selectivity for n-heptane hydrocracking.

EPR, TEM and cell viability study of asbestiform zeolite fibers in cell media

Human monocyte U937 cell line was used as a model to verify the toxicity of erionite and offretite asbestiform zeolite fibers. As a presumed non-toxic reference, a fibrous scolecite zeolite was also used. To analyze the process of fiber ingestion into cells and the cells-fibers interactions, a spin-probe electron paramagnetic resonance (EPR) analysis was performed supported by transmission electron microscopy (TEM) and cell viability measurements as a function of the incubation time. Erionite fibers were fast internalized in the membrane mainly as aggregates with radical-solution drops trapped inside, and were found in the cytosol and at the nucleus. In 24h, first erionite fibers rich in sodium and potassium, and then calcium-rich erionite fibers, induced cell necrosis. The offretite fibers formed rounding electron-dense filaments which transformed in curved filaments, initially perturbing the cell structure and interacting at the external surface more than erionite fibers. Such interactions probably diminished the toxic effect of offretite on cells. Interestingly, the presumed non-toxic scolecite fibers were partially internalized, inducing formation of swollen mitochondria and squared cells. Overall, the toxic effect of the fibrous zeolites was related to fiber morphology, chemical distribution of sites, structural variations and formation of aggregates.

Electropsun Ni-W/zeolite composite fibers for n-heptane hydrocracking and hydroisomerization

Nickel oxide-tungsten oxide/zeolite hydrocracking fibers were prepared by the electrospinning method and compared with the hydrocracking particles prepared by wet impregnation method. Scanning electron microscope, BET and XRD were used to characterize the two catalysts. The two catalysts were tested in a continuous flow fixed-bed reactor under 5 bars hydrogen pressure at 400 °C for n-heptane hydrocracking and hydroisomerization. The fibers registered a higher BET surface area compared to the particles as well as promising catalytic activity with C3 and iC4 formed as major cracking products; a higher conversion by 17 wt. % and 6 wt. % during the first 60 and 120 min on stream respectively compared to the hydrocracking particles. Apart from providing the hydrogenation function, the addition of the metallic component provided superior mechanical strength to the fibers when compared with the pure zeolite fibers. In addition, less coke was formed with the fibers. These novel composite fibers showed a uniform elemental distribution which is beneficial for a hydrocracking catalyst, providing close proximity of the acidic and hydrogenation sites. The latter which was reflected in less olefin formation and superior n-heptane isomerization. This study paves the way for promising research on utilizing zeolites in the form of fibers for various catalytic applications.

Electron paramagnetic resonance and transmission electron microscopy study of the interactions between asbestiform zeolite fibers and model membranes

ABSTRACTDifferent asbestiform zeolite fibers of the erionite (termed GF1 and MD8, demonstrated carcinogenic) and offretite (termed BV12, suspected carcinogenic) families were investigated by analyzing the electron paramagnetic resonance (EPR) spectra of selected surfactant spin probes and transmission electron microscopy (TEM) images in the presence of model membranes—cetyltrimethylammonium (CTAB) micelles, egg-lecithin liposomes, and dimyristoylphosphatidylcholine (DMPC) liposomes. This was undertaken to obtain information on interactions occurring at a molecular level between fibers and membranes which correlate with entrance of fibers into the membrane model or location of the fibers at the external or internal membrane interfaces. For CTAB micelles, all fibers were able to enter the micelles, but the hair-like structure and chemical surface characteristics of GF1 modified the micelle structure toward a bilayer-like organization, while MD8 and BV12, being shorter fibers and with a high density of surface interacting groups, partially destroyed the micelles. For liposomes, GF1 fibers partially penetrated the core solution, but DMPC liposomes showed increasing rigidity and organization of the bilayer. Conversely, for MD8 and BV12, the fibers did not cross the membrane demonstrating a smaller membrane structure perturbation. Scolecite fibers (termed SC1), used for comparison, presented poor interactions with the model membranes. The carcinogenicity of the zeolites, as postulated in the series SC1<BV12<MD8<GF1, may be related to the structural modifications of the model membranes when interacting with these zeolite fibers.

CO 2 , CH 4 and N 2 separation with a 3DFD-printed ZSM-5 monolith

Abstract A new method for producing zeolitic monoliths is used to produce a ZSM-5 based monolith for gas separation. The new method involves the 3DFD (Three Dimensional Fiber Deposition) printing of several layers of zeolite fibers on top of each other in a well-defined way, resulting in an open monolithic structure with open and inter-connected channels. The monolithic structure, consisting of ZSM-5 zeolite, was characterized with SEM, Ar and Hg porosimetry. Single component isotherms of CO 2 , CH 4 and N 2 were recorded on the 3DFD-printed ZSM-5 monolith, at different temperatures (283 K, 291 K, 302 K and 309 K) using a gravimetric method. Isosteric heats of adsorption show that CO 2 is the most strongly adsorbing component, in order followed by CH 4 and N 2 . The monolithic structure was subjected to breakthrough separation experiments with CO 2 /N 2 and CO 2 /CH 4 gas mixtures. Excellent separation performance is achieved. Moreover, the ZSM-5 monolith can be easily regenerated in isothermal conditions.

The Fabrication of Ga2O3/ZSM-5 Hollow Fibers for Efficient Catalytic Conversion of n-Butane into Light Olefins and Aromatics

In this study, the dehydrogenation component of Ga2O3 was introduced into ZSM-5 nanocrystals to prepare Ga2O3/ZSM-5 hollow fiber-based bifunctional catalysts. The physicochemical features of as-prepared catalysts were characterized by means of XRD, BET, SEM, STEM, NH3-TPD, etc., and their performances for the catalytic conversion of n-butane to produce light olefins and aromatics were investigated. The results indicated that a very small amount of gallium can cause a marked enhancement in the catalytic activity of ZSM-5 because of the synergistic effect of the dehydrogenation and aromatization properties of Ga2O3 and the cracking function of ZSM-5. Compared with Ga2O3/ZSM-5 nanoparticles, the unique hierarchical macro-meso-microporosity of the as-prepared hollow fibers can effectively enlarge the bifunctionality by enhancing the accessibility of active sites and the diffusion. Consequently, Ga2O3/ZSM-5 hollow fibers show excellent catalytic conversion of n-butane, with the highest yield of light olefins plus aromatics at 600 °C by 87.6%, which is 56.3%, 24.6%, and 13.3% higher than that of ZSM-5, ZSM-5 zeolite fibers, and Ga2O3/ZSM-5, respectively.

Electrospun zeolite-Y fibers: Fabrication and morphology analysis

Zeolite is an interesting microporous material. It has potential applications ranging from catalysts for petroleum refining to gas sensing. Recently, fibrous form of zeolite has attracted much attention due to its high aspect ratio and promising performances. In the present work, we report the fabrication of zeolite-Y fibers through the electrospinning method. Zeolite-Y fibers were electrospun into fibers using a precursor of zeolite particles and polyvinylpyrrolidone solution with different concentrations. An optimum concentration was then studied in details with respect to fiber morphology. The solution was electrospun with a constant flow of rate 0.5 ml/h under different electrospinning voltages (10–28 kV) and nozzle to collector distances (10 cm and 15 cm). The fibers were characterized for their morphology using scanning electron microscopy. Microscopic analysis revealed that fiber diameter and fiber continuity were greatly influenced by the process parameters. The electrospinning technique gave flexibility and control over the formed fiber morphology. An optimum combination of the process parameters resulted in coherent and continuous zeolite fibers. The fabrication of zeolite-Y fibers through electrospinning opens new doors for further exploration with respect to fibrous zeolites for potential new applications.

Morpho-chemical characterization and surface properties of carcinogenic zeolite fibers

Erionite belonging to the zeolite family is a human health-hazard, since it was demonstrated to be carcinogenic. Conversely, offretite family zeolites were suspected carcinogenic. Mineralogical, morphological, chemical, and surface characterizations were performed on two erionites (GF1, MD8) and one offretite (BV12) fibrous samples and, for comparison, one scolecite (SC1) sample. The specific surface area analysis indicated a larger availability of surface sites for the adsorption onto GF1, while SC1 shows the lowest one and the presence of large pores in the poorly fibrous zeolite aggregates. Selected spin probes revealed a high adsorption capacity of GF1 compared to the other zeolites, but the polar/charged interacting sites were well distributed, intercalated by less polar sites (Si–O–Si). MD8 surface is less homogeneous and the polar/charged sites are more interacting and closer to each other compared to GF1. The interacting ability of BV12 surface is much lower than that found for GF1 and MD8 and the probes are trapped in small pores into the fibrous aggregates. In comparison with the other zeolites, the non-carcinogenic SC1 shows a poor interacting ability and a lower surface polarity. These results helped to clarify the chemical properties and the surface interacting ability of these zeolite fibers which may be related to their carcinogenicity.

Fabrication of electrospun LTL zeolite fibers and their application for dye removal

Zeolites are potential adsorbents for dyes removal in wastewater; however, separation of the zeolite particles from the wastewater after adsorption is tedious. Structured zeolites in the form of fibers offer faster and easier adsorbent separation. Herein, we applied electrospinning (ES) technique to fabricate LTL zeolite fibers. To improve the mechanical stability of the zeolite fibers, aluminum chloride was added in the suspension prior to ES. Thermal analyses of the as-spun fibers suggest that calcination at 700 °C is sufficient to decompose polymers and chloride ions. After calcination, the fibers contain (ca. 66 %) of LTL zeolite and (ca. 34 %) of alumina phases, while the diameter is below 1 µm. The alumina phase is very dense; the surface area of the fibers depends mainly on the zeolite content. Dyes sorption studies show that while the fibers exhibit significant adsorption toward cationic methylene blue (MB), it is ineffective for anionic orange G. The maximum MB adsorption capacity (Q m) for the zeolite fibers was found to be 30 mg g−1 lower than bare zeolite powder (72 mg g−1). The fibers fibrous nature was retained to certain degree after sorption makes them easier and faster for separation and reuse.

Hierarchical macro-meso-microporous ZSM-5 zeolite hollow fibers with highly efficient catalytic cracking capability.

Zeolite fibers have attracted growing interest for a range of new applications because of their structural particularity while maintaining the intrinsic performances of the building blocks of zeolites. The fabrication of uniform zeolite fibers with tunable hierarchical porosity and further exploration of their catalytic potential are of great importance. Here, we present a versatile and facile method for the fabrication of hierarchical ZSM-5 zeolite fibers with macro-meso-microporosity by coaxial electrospinning. Due to the synergistic integration of the suitable acidity and the hierarchical porosity, high yield of propylene and excellent anti-coking stability were demonstrated on the as-prepared ZSM-5 hollow fibers in the catalytic cracking reaction of iso-butane. This work may also provide good model catalysts with uniform wall thickness and tunable porosity for studying a series of important catalytic reactions.

Fabrication of molecular sieve fibers by electrospinning

Molecular sieves, such as zeolites and mesoporous materials, have been widely used in the fields of catalysis, adsorption, ion-exchange, and are finding new applications in optics, electronics, magnetism, medicine, etc. Molecular sieves with different morphologies or aggregation states, such as spheres, films, and fibers have been prepared to fulfil the need for various applications. Electrospinning offers a simple and straightforward way for generating ultrafine fibers with diameter in the range of nanometres to micrometres from a variety of materials. In recent decades, electrospinning has been introduced to prepare molecular sieve fibers. In this review, fibrous molecular sieves including zeolite fibers, siliceous and nonsiliceous mesoporous fibers prepared by electrospinning are summarized, and their prominent applications in optics, adsorptions, catalysis, etc. are highlighted.

Dry gel conversion synthesis of shape controlled MFI type zeolite materials

Acid treated silica fibers, coming either from asbestos cord waste or calcium aluminosilicate glass, were engaged as reactants to product MFI type zeolite fibers applying a dry gel conversion (DGC) type synthesis. The impact of amorphous silica fiber shape and synthesis conditions on morphology of the final product was investigated. Enhanced zeolite nucleation and restricted crystal growth are necessary to maintain the initial fiber morphology. Whereas a DGC type crystallization in hydroxide media results in the formation of zeolite fibers, the use of fluoride ions leads to the formation of large individual zeolite particles. Synthesis conditions have to be adapted to form zeolite particles with an average size smaller than the silica fiber diameter to allow a good conservation of the fiber morphology. Final zeolite fibers have textural properties comparable to a standard zeolite product and are promising for adsorption applications.

Prospective Study of Mesothelioma Mortality in Turkish Villages With Exposure to Fibrous Zeolite

Mesothelioma incidence is high in certain villages on the Anatolian plateau in Turkey, where environmental exposure includes erionite, a form of zeolite fibers, from the local volcanic tuff. Previous studies of this exposure were cross-sectional or with a follow-up period of only a few years. A prospective study of residents of two exposed and one nearby control village was initiated in 1979 and continued through December 31, 2003. A total of 891 men and women, aged 20 years or older, were included, 230 of them residing in the village without known exposure to erionite. Mortality data were obtained from hospital records and death certificates. During the 23-year follow-up, 372 deaths occurred; 119 of these were from mesothelioma, which was the cause of 44.5% of all deaths in the exposed villages. Seventeen patients had peritoneal mesothelioma; the rest had pleural mesothelioma. Only two cases of mesothelioma, one of each type, occurred in the control village-both in women born elsewhere. When standardized to the world population, the pleural mesothelioma incidence was approximately 700 and 200 cases per 100,000 people annually in the two exposed villages and about 10 cases per 100,000 people in the control village. When we used Danish data for comparison, the standardized pleural mesothelioma mortality rate was 485 (95% confidence interval = 395 to 590). Our results emphasize the severity of the mesothelioma endemic in erionite-exposed areas of Turkey and call for intensified prevention of mesothelioma by limiting environmental exposures to these fibers.

Fabrication of analcime zeolite fibers by hydrothermal synthesis

Analcime (ANA) zeolite fibers with an average diameter of 300–600 nm were prepared for the first time by means of the in situ TPAOH template electrostatic self-assembly technique. In this paper, the conditions of its formation such as pH of synthesis sol and effect of α-Al 2O 3 plates have been described in detail. The structure and thermal stability of the fibers have been confirmed by means of XRD, FT-IR, and DTA analyses. The surface morphology, size distribution, and elemental composition of ANA nanoparticles have been characterized by HRTEM and SEM-EDX approaches.

Phosphorimetric Determination of Polycyclic Aromatic Hydrocarbons in Clinoptilolite-Filled Fibers at Room Temperature

The phosphorescence of polycyclic aromatic hydrocarbons (PAHs) adsorbed on natural zeolite (clinoptilolite) and clinoptilolite-filled acrylic fibers was studied at room temperature. The optimal conditions were selected for the phosphorescence of PAHs extracted from water and water–dioxane solutions at room temperature using clinoptilolite-filled fibers. The phosphorescence of PAHs in the clinoptilolite-filled fibers at room temperature is characterized by a high quantum yield and long lifetimes of PAH triplet states, as was the case at low temperatures (77 K). The results obtained indicate that the adsorbents used offer promise for the analytical chemistry of PAHs.

Electrophoretic assembly of nanozeolites: zeolite coated fibers and hollow zeolite fibers

Download options Please wait... Supplementary files SEM images DOC (529K) XRD patterns DOC (159K) Article information DOI https://doi.org/10.1039/B010197O Article type Communication Submitted 20 Dec 2000 Accepted 16 Mar 2001 First published 03 Apr 2001 Download Citation Chem. Commun., 2001, 783-784 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Electrophoretic assembly of nanozeolites: zeolite coated fibers and hollow zeolite fibers C. Ke, W. L. Yang, Z. Ni, Y. J. Wang, Y. Tang, Y. Gu and Z. Gao, Chem. Commun., 2001, 783 DOI: 10.1039/B010197O To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author C. Ke W. L. Yang Z. Ni Y. J. Wang Y. Tang Y. Gu Z. Gao