scholarly journals Uniform synthesis of palladium species confined in a small-pore zeolite via full ion-exchange investigated by cryogenic electron microscopy

2021 ◽  
Author(s):  
Yongwoo Kim ◽  
Jongbaek Sung ◽  
Sungsu Kang ◽  
Jaeha Lee ◽  
Min-Ho Kang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Ion Exchange ◽  
Small Pore ◽  
Catalytic Applications

Uniformly dispersed palladium species in small-pore zeolite are successfully prepared for catalytic applications, and are investigated by advanced microscopic methods.

Embedding Procedure for Water Swollen Samples

1970 ◽  
Vol 28 ◽  
pp. 504-505
Author(s):  
Ann M. Thomas ◽  
Virginia Shemeley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Exchange ◽  
Structural Changes ◽  
Cross Linking ◽  
Ion Exchange Resins ◽  
Transmission Electron ◽  
First Pass ◽  
Exchange Resins

Those samples which swell rapidly when exposed to water are, at best, difficult to section for transmission electron microscopy. Some materials literally burst out of the embedding block with the first pass by the knife, and even the most rapid cutting cycle produces sections of limited value. Many ion exchange resins swell in water; some undergo irreversible structural changes when dried. We developed our embedding procedure to handle this type of sample, but it should be applicable to many materials that present similar sectioning difficulties.The purpose of our embedding procedure is to build up a cross-linking network throughout the sample, while it is in a water swollen state. Our procedure was suggested to us by the work of Rosenberg, where he mentioned the formation of a tridimensional structure by the polymerization of the GMA biproduct, triglycol dimethacrylate.

Effectiveness of Calcium Deficiency in Nanosized Hydroxyapatite for Removal of Fe(II), Cu(II), Ni(II) and Cr(VI) Ions from Aqueous Solutions

2019 ◽  
Vol 56 ◽  
pp. 17-27
Author(s):  
Van Dat Doan ◽  
Van Thuan Le ◽  
Hoang Sinh Le ◽  
Dinh Hien Ta ◽  
Hoai Thuong Nguyen
Keyword(s):  
Electron Microscopy ◽  
Ion Exchange ◽  
Aqueous Solutions ◽  
Calcium Deficiency ◽  
Exchange Mechanism ◽  
Precipitation Method ◽  
X Ray ◽  
Transmission Electron ◽  
Bet Method ◽  
Langmuir Isotherm Model

In this work, nanosized calcium deficient hydroxyapatite (nCDHA) was synthesized by the precipitation method, and then utilized as an adsorbent for removal of Fe (II), Cu (II), Ni (II) and Cr (VI) ions from aqueous solutions after characterizing it by various techniques as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and BET method. A possible structure of synthesized nCDHA was proposed. The adsorption study indicated that the adsorption equilibrium is well fitted with Langmuir isotherm model with the maximum adsorption capacities followed the order of Fe (II) > Cu (II) > Ni (II) > Cr (VI) with the values of 137.23, 128.02, 83.19 and 2.92 mg/g, respectively. The ion-exchange mechanism was dominant for the adsorption of metal ions onto nCDHA at initial metal concentrations lower than 0.01 mol/L. Along with the ion-exchange mechanism, there was an additional precipitation occurred on the surface of nCDHA in the case of Fe (II) and Cu (II) at initial concentrations higher than 0.01 mol/L.

scholarly journals K-paracelsian (KAlSi3O8·H2O) and identification of a simple building scheme of dense double-crankshaft zeolite topologies

IUCrJ ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 66-71 ◽  
Author(s):  
Cristian-R. Boruntea ◽  
Peter N. R. Vennestrøm ◽  
Lars F. Lundegaard
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Phase Space ◽  
Ex Situ ◽  
Zeolite Synthesis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Synthesis Conditions ◽  
Small Pore ◽  
Scanning Electron

During screening of the phase space using KOH and 1-methyl-4-aza-1-azoniabicyclo[2.2.2]octane hydroxide (1-methyl-DABCO) under hydrothermal zeolite synthesis conditions, K-paracelsian was synthesized. Scanning electron microscopy, energy dispersive X-ray spectroscopy and ex situ powder X-ray diffraction analysis revealed a material that is compositionally closely related to the mineral microcline and structurally closely related to the mineral paracelsian, both of which are feldspars. In contrast to the feldspars, K-paracelsian contains intrazeolitic water corresponding to one molecule per cage. In the case of K-paracelsian it might be useful to consider it a link between feldspars and zeolites. It was also shown that K-paracelsian can be described as the simplest endmember of a family of dense double-crankshaft zeolite topologies. By applying the identified building principle, a number of known zeolite topologies can be constructed. Furthermore, it facilitates the construction of a range of hypothetical small-pore structures that are crystallo-chemically healthy, but which have not yet been realized experimentally.

Determination of the Thicknesses and Visualization of Ion-Exchange Waveguides in Glasses by Scanning Electron Microscopy

2019 ◽  
Vol 64 (3) ◽  
pp. 418-421 ◽  
Author(s):  
A. I. Lihachev ◽  
A. V. Nashchekin ◽  
R. V. Sokolov ◽  
S. G. Konnikov
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Ion Exchange ◽  
Scanning Electron

scholarly journals The Preparation and Catalytic Properties of Nanoporous Pt/CeO2 Composites with Nanorod Framework Structures

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 683 ◽  
Author(s):  
Haiyang Wang ◽  
Dong Duan ◽  
Chen Ma ◽  
Wenyu Shi ◽  
Miaomiao Liang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Catalytic Properties ◽  
Structural Parameters ◽  
Active Oxygen Species ◽  
Pt Nanoparticles ◽  
Strong Interactions ◽  
X Ray ◽  
Small Pore ◽  
Melt Spun

Pt/CeO2 catalysts with nanoporous structures were prepared by the facile dealloying of melt-spun Al92−XCe8PtX (X = 0.1; 0.3 and 0.5) ribbons followed by calcination. The phase compositions and structural parameters of the catalysts were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The specific surface area and pore size distribution were characterized by N2 adsorption–desorption tests. The catalytic properties were evaluated by a three-way catalyst (TWC) measurement system. The results revealed that the dealloyed samples exhibited a nanorod framework structure. The Pt nanoparticles that formed in situ were supported and highly dispersed on the CeO2 nanorod surface and had sizes in the range of 2–5 nm. For the catalyst prepared from the melt-spun Al91.7Ce8Pt0.3 ribbons, the 50% CO conversion temperature (T50) was 91 °C, and total CO could be converted when the temperature was increased to 113 °C. An X-ray photoelectron spectroscopy (XPS) test showed that the Pt0.3/CeO2 sample had a slightly richer oxygen vacancy; and a H2 temperature-programmed reduction (H2-TPR) test demonstrated its superior adsorption ability for reduction gas and high content of active oxygen species. The experiments indicated that the catalytic performance could be retained without any attenuation after 130 h when water and CO2 were present in the reaction gas. The favorable catalytic activities were attributed to the high specific areas and small pore and Pt particle sizes as well as the strong interactions between the CeO2 and Pt nanoparticles. The Pt nanoparticles were embedded in the surface of the CeO2 nanorods, inhibiting growth. Therefore, the catalytic stability and water resistance were excellent.

scholarly journals Characterization and Adsorption Behavior of Strontium from Aqueous Solutions onto Chitosan-Fuller’s Earth Beads

Healthcare ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 52 ◽  
Author(s):  
Shameem Hasan ◽  
A. Iasir ◽  
Tushar Ghosh ◽  
Bhaskar Sen Gupta ◽  
Mark Prelas
Keyword(s):  
Electron Microscopy ◽  
Ion Exchange ◽  
Photoelectron Spectroscopy ◽  
Exchange Process ◽  
Equilibrium Concentration ◽  
Bet Surface Area ◽  
Ion Exchange Process ◽  
Adsorption Capacities ◽  
Transmission Electron ◽  
Fuller’S Earth

Fuller’s earth spherical beads using chitosan as a binder were prepared for the removal of strontium ions from aqueous solution. The adsorbents were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed the porous nature of the beads. The Brunauer–Emmett–Teller (BET) surface area of the beads was found to be 48.5 m2/g. The adsorption capacities of the beads were evaluated under both batch and dynamic conditions. The adsorption capacity was found to be ~29 mg/g of adsorbent at 298 K when the equilibrium concentration of strontium in the solution was 925 mg/L at pH 6.5. The X-ray photoelectron spectroscopy (XPS) data suggest that strontium uptake by the beads occurs mainly through an ion-exchange process. Kinetic data indicate that the sorption of strontium onto the beads follows anomalous diffusion. Thermodynamic data suggest that the ion-exchange of Sr2+ on the bead surface was feasible, spontaneous and endothermic in nature.

AlPO4 Molecular Sieves Modified with Metal Chelate Complexes

1992 ◽  
Vol 57 (4) ◽  
pp. 774-780 ◽  
Author(s):  
Stanisłav Kowalak ◽  
Kenneth J. Balkus
Keyword(s):  
Ion Exchange ◽  
Metal Complexes ◽  
Molecular Sieves ◽  
Metal Chelate ◽  
New Method ◽  
Cyclohexene Oxidation ◽  
Chelate Complexes ◽  
Pore System ◽  
Catalytic Applications ◽  
Exchange Properties

A new method for modification AlPO4 molecular sieves has been presented. Lack of ion-exchange properties makes the modification of aluminium phosphates for catalytic applications difficult. We have developed a method that involves the crystallization of AlPO4 molecular sieves around metal complexes. This results in encapsulation of the complexes within the intracrystalline pore system. Several metallophthalocyanines have been successfully encapsulated into AlPO4-5 and subsequently tested as catalysts for cyclohexene oxidation. Significant differences in activity result from the presence of different metallophthalocyanines.

scholarly journals INTESTINAL CAPILLARIES

1969 ◽  
Vol 41 (1) ◽  
pp. 33-58 ◽  
Author(s):  
F. Clementi ◽  
G. E. Palade
Keyword(s):  
Electron Microscopy ◽  
Horseradish Peroxidase ◽  
Intestinal Mucosa ◽  
Intercellular Junctions ◽  
Post Injection ◽  
Pore System ◽  
Blood Capillaries ◽  
Large Pore ◽  
Small Pore ◽  
Histochemical Procedure

Horseradish peroxidase (mol. diam. ≃50 A) and ferritin (mol. diam. ≃110 A) were used as probe molecules for the small and large pore system, respectively, in blood capillaries of the intestinal mucosa of the mouse. Peroxidase distribution was followed in time, after intravenous injection, by applying the Graham-Karnovsky histochemical procedure to aldehyde-fixed specimens. The tracer was found to leave the plasma rapidly and to reach the pericapillary spaces 1 min post injection. Between 1 min and 1 min 30 sec, gradients of peroxidase reaction product could be demonstrated regularly around the capillaries; their highs were located opposite the fenestrated parts of the endothelium. These gradients were replaced by even distribution past 1 min 30 sec. Ferritin, followed directly by electron microscopy, appeared in the pericapillary spaces 3–4 min after i.v. injection. Like peroxidase, it initially produced transient gradients with highs opposite the fenestrated parts of the endothelium. For both tracers, there was no evidence of movement through intercellular junctions, and transport by plasmalemmal vesicles appeared less efficient than outflow through fenestrae. It is concluded that, in the blood capillaries of the inintestinal mucosa, the diaphragms of the endothelial fenestrae contain the structural equivalents of the small pore system. The large pore system seems to be restricted to a fraction of the fenestral population which presumably consists of diaphragm-free or diaphragm-deficient units.

The adsorption of methylene blue on montmorillonite from acid solutions

Clay Minerals ◽  
2011 ◽  
Vol 46 (3) ◽  
pp. 461-471 ◽  
Author(s):  
Z. Klika ◽  
P. Pustková ◽  
M. Dudová ◽  
P. Čapková ◽  
Ch. Kliková ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Methylene Blue ◽  
Ion Exchange ◽  
Powder Diffraction ◽  
Acid Solutions ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Adsorption Wave ◽  
Scanning Electron

AbstractThe adsorption of methylene blue (MB) on montmorillonite from acid solutions has not yet been studied in detail. In this paper the adsorption of this dye on Ca/SAz montmorillonite from 0.32, 0.80 and 1.60 M HCl solutions at ambient temperature and after 2 hours leaching was carefully studied and evaluated. Under the above conditions the MB/SAz intercalates formed are practically insoluble. In contrast to the adsorption of methylene blue on montmorillonite from aqueous solutions, the adsorption from acid solutions consists of two adsorption waves. The intercalated samples from the first and second waves were studied using X-ray powder diffraction (XRD), FTIR, Vis spectroscopy, and scanning electron microscopy (SEM) equipped with a microprobe system. The adsorption of MB in the first wave is attributed to ion exchange of the dye cationic species (MB+, MB22+, H-aggregates, MBH2+ and H+) for the original interlayer cations of montmorillonite. The percentages of MBH2+ and H+ based on total adsorbed MB were estimated for varying HCl concentrations. The second adsorption wave is linked to the precipitation of MB species on the outer MB/SAz surface.

Sign in / Sign up

Export Citation Format

Share Document