Dynamic Behavior of Colloidal Silica in the Presence of Solid Phase

2002 ◽  
Vol 757 ◽  
Author(s):  
Taiji Chida ◽  
Yuichi Niibori ◽  
Osamu Tochiyama ◽  
Koichi Tanaka
Keyword(s):  
Surface Area ◽  
Dynamic Behavior ◽  
Amorphous Silica ◽  
Colloidal Silica ◽  
Solid Phase ◽  
Size Fraction ◽  
Soluble Form ◽  
Supersaturated Solution ◽  
Colloidal Form ◽  
Soluble Silica

ABSTRACTSince silica undergoes polymerization, precipitation, and dissolution depending on the change in pH or temperature, the chemical behavior of silica would be much complicated when cement for the construction of geological disposal system greatly changes the pH (8 to 13) of groundwater. To clarify the dynamic behavior of silica in such an alkaline solution, the concentrations of silica in both soluble and colloidal form in the supersaturated solution in the presence of solid phase have been traced over a 40-day period. In the experiment, the concentration of silica in a soluble form was determined by the silicomolybdenum-yellow method, and the concentration of silica in soluble plus colloidal forms was determined by adjusting the pH of the solution to 13, where all the silica changes into a soluble form (mainly monomeric). In order to examine the dynamic behavior of colloidal silica with solid phase of silica, this study has used natural quartz and pure commercial amorphous silica, both in a size fraction of 74–149 μm, whose specific surface-area (BET, N2 gas) were respectively 1.0 m2/g and 400 m2/g. The Na2SiO3 solution (250 ml, pH>10, 298 K) was poured into a polyethylene vessel containing quartz or amorphous silica (0.1 g or 0.5 g), HNO3 and a buffer solution. The pH of the solution was set to 8. The silica initially in a soluble form at pH>10 (6.8×10-3 M or 1.2×10-2 M) became supersaturated and either deposited on the solid surface or changed into the colloidal form. The ratio of silica in those form depended both on the initial concentration of soluble-silica and the surface area of the solid. The concentration of colloidal-silica gradually decreased, where the logarithm of its concentration decreased linearly against time after the concentration of soluble-silica decreased to a metastable concentration slightly higher than the solubility of soluble-silica.

Dissolution Rate of Colloidal Silica in Highly Alkaline Solution

2004 ◽  
Vol 824 ◽  
Author(s):  
Taiji Chida ◽  
Yuichi Niibori ◽  
Osamu Tochiyama ◽  
Hitoshi Mimura ◽  
Koichi Tanaka
Keyword(s):  
Dissolution Rate ◽  
Alkaline Solution ◽  
Amorphous Silica ◽  
Colloidal Silica ◽  
Ph Value ◽  
Solid Phase ◽  
Kinetic Property ◽  
Polymerization Process ◽  
Soluble Form ◽  
Soluble Silica

AbstractFor the performance assessment of the radioactive waste repository, it is important to clarify the dynamic behavior of silica (silicic acid and hydrous or unhydrous silicon dioxides). The behavior of silica would be complicated when cement is used for the construction of the repository, since silica takes various forms due to polymerization, precipitation and dissolution with change of pH or temperature. In order to know the fundamental kinetic property of silica, this study has examined the dissolution rate of colloidal-silica.In the experiment, the concentration of silica in a soluble form was determined by the silicomolybdenum-yellow method. In this study, soluble-silica was defined as silica reacting with molybdate reagent and coloring yellow, and colloidal-silica was defined as silica in liquid phase except for soluble-silica. Colloidal-silica was obtained through the polymerization process, where the pH value of silica solution was brought down from over 10 by HNO3 solution. This study examined dissolution rate of colloidal-silica again by setting to 10 or 13 in pH-value and 288 K, 298 K or 313 K in temperature. In the experimental results, the dissolution reaction of colloidal-silica proceeded linearly with time, when the dissolution of colloidal silica was not restricted by the solubility of silica. To estimate the dissolution rate, we assumed df /dt = k*, where f is the soluble-silica fraction defined as the amount of soluble-silica divided by the silica amount introduced into the sample solution, t the time (s) and k* the rate constant (s-1). The activation energy for the dissolution of the colloidal-silica at pH 13 was estimated to be approximately 80 kJ·mol-1which was similar to that for amorphous silica (solid phase) at pH 13. This suggests the same reaction mechanism for the dissolution of colloidal-silica and amorphous silica in highly alkaline solution.

Dependence of the Dynamic Behavior of Supersaturated Silicic Acid on the Surface Area of the Solid Phase

2008 ◽  
Author(s):  
Yuichi Niibori ◽  
Yasunori Kasuga ◽  
Hiroshi Kokubun ◽  
Kazuki Iijima ◽  
Hitoshi Mimura
Keyword(s):  
Surface Area ◽  
Dynamic Behavior ◽  
Silicic Acid ◽  
Solid Phase

Silica-induced cytokine release from A549 cells: importance of surface area versus size

2001 ◽  
Vol 20 (1) ◽  
pp. 46-55 ◽  
Author(s):  
R B Hefland ◽  
P E Schwarzel ◽  
B V Johansen ◽  
T Myran ◽  
N Uthus ◽  
...  
Keyword(s):  
Surface Area ◽  
Health Effects ◽  
Amorphous Silica ◽  
Size Fraction ◽  
A549 Cells ◽  
Surface Reactivity ◽  
Cytokine Release ◽  
Critical Determinant ◽  
Potential Health ◽  
Potent Inducer

Physical and chemical properties such as structure, composition and surface reactivity determine the biological activity of mineral particles. Long-term exposureto crystalline silica is known to cause persistent pulmonary inflammation leading to adverse health effects. There is less information about the potential health effects of amorphous (noncrystal-line) silica. In this study, the inflammatory and cytotoxic potency of crystalline and amorphous silica in relation to particle size and surface area was assessed. Human epithelial lung cells (A549) were exposed to different size fractions of quartz (aerodynamic diameter 0.5,2 and 10 sm) and amorphous silica (diameter 0.3 pm). All particles induced increased release ofthe proinflammatory cytokines interleukin (IL)-6 and IL-8. When cells were exposed to equal masses of quartz, the smallest size fraction was the most potent. These differences, however, disappeared when cytokine release was related to equal surface areas. When amorphous silica and quartz were compared, the amorphoussilicawas mostpotentto induce IL-6 regardless of how exposure was expressed, whereas the smallest size fraction of quartz was the most potent inducer of IL-8. Thus, the surface area seems to be the critical determinant when potency of different sizes of quartz is compared.

Analysis of the system precipitation reactor-separation unit. Porosity of the filtration cake as a function of properties of the solid phase

1981 ◽  
Vol 46 (11) ◽  
pp. 2640-2649 ◽  
Author(s):  
Otakar Söhnel
Keyword(s):  
Linear Function ◽  
Surface Area ◽  
Granulometric Composition ◽  
Solid Phase ◽  
Separation Unit ◽  
Initial Concentration ◽  
Actual Surface ◽  
Suspension Concentration

Porosity of the filtration cake, formed at filtration of model suspensions of CaCO3, BaCrO4 and ZnO is not a function of suspension concentration as long as the solid phase forming the suspension is of the same granulometric composition. The calculated surface area of the solid phase, effective as concerns filtration at ΔP = 30 kPa, is smaller than the actual surface area determined by absorption of nitrogen. Porosity of the filtration cake formed at filtration of suspensions of Mg(OH)2, CaCO3, SrCO3 and BaCO3 prepared by precipitation is a linear function of the initial concentration of precipitated solutions since it is affected by the size and polydispersity of originating particles in dependence on concentration of precipitated solutions. The cakes formed at filtration of precipitated suspensions of CaCO3, SrCO3 and BaCO3 aged for up to 2 hours from the instant of their preparation have a constant porosity which is independent of the time of suspension aging.

scholarly journals Silica and Silica–Titania Xerogels Doped with Iron(III) for Total Antioxidant Capacity Determination

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2019
Author(s):  
Maria A. Morosanova ◽  
Ksenia V. Chaikun ◽  
Elena I. Morosanova
Keyword(s):  
Antioxidant Capacity ◽  
Surface Area ◽  
Total Antioxidant Capacity ◽  
Solid Phase ◽  
Bet Surface Area ◽  
Sensor Material ◽  
Total Antioxidant ◽  
Sensor Materials ◽  
Ascorbic Acids ◽  
Capacity Determination

In order to design a sensor material for total antioxidant capacity determination we have prepared silica and silica–titania xerogels doped with iron(III) and modified with 1,10-phenanthroline. Titanium(IV) tetraethoxyde content in the precursors (titanium(IV) tetraethoxyde and tetraethyl orthosilicate) mixtures has been varied from 0 to 12.5% vol. Iron(III) concentrations in sol has been varied from 1 to 100 mM. The increase of titanium(IV) content has led to a decrease in BET surface area and average pore diameter and an increase of micropore surface area and volume, which has resulted in better iron(III) retention in the xerogels. Iron(III), immobilized in the xerogel matrix, retains its ability to form complexes with 1,10-phenanthroline and to be reduced to iron(II). Static capacities for 1,10-phenanthroline have been determined for all the iron(III) doped xerogels (0.207 mmol/g–0.239 mmol/g) and they are not dependent on the iron(III) content. Sensor materials—xerogels doped with iron(III) and modified with 1,10-phenanthroline—have been used for antioxidants (catechol, gallic and ascorbic acids, and sulphite) solid phase spectrophotometric determination. Limits of detection for catechol, gallic and ascorbic acids, and sulphite equal 7.8 × 10−6 M, 5.4 × 10−6 M, 1.2 × 10−5 M, and 3.1 × 10−4 M, respectively. The increase of titanium(IV) content in sensor material has led to an increase of the reaction rate and the sensitivity of determination. Proposed sensor materials have been applied for total antioxidant capacity (in gallic acid equivalents) determination in soft beverages, have demonstrated high stability, and can be stored up to 6 months at room temperature.

scholarly journals Dynamic crushing behavior of closed-cell aluminum foams based on different space-filling unit cells

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
S. Talebi ◽  
R. Hedayati ◽  
M. Sadighi
Keyword(s):  
Surface Area ◽  
Dynamic Behavior ◽  
Energy Absorption ◽  
Peak Stress ◽  
Absorption Capacity ◽  
Unit Cell ◽  
Lattice Structures ◽  
Energy Absorption Capacity ◽  
Closed Cell ◽  
Unit Cells

AbstractClosed-cell metal foams are cellular solids that show unique properties such as high strength to weight ratio, high energy absorption capacity, and low thermal conductivity. Due to being computation and cost effective, modeling the behavior of closed-cell foams using regular unit cells has attracted a lot of attention in this regard. Recent developments in additive manufacturing techniques which have made the production of rationally designed porous structures feasible has also contributed to recent increasing interest in studying the mechanical behavior of regular lattice structures. In this study, five different topologies namely Kelvin, Weaire–Phelan, rhombicuboctahedron, octahedral, and truncated cube are considered for constructing lattice structures. The effects of foam density and impact velocity on the stress–strain curves, first peak stress, and energy absorption capacity are investigated. The results showed that unit cell topology has a very significant effect on the stiffness, first peak stress, failure mode, and energy absorption capacity. Among all the unit cell types, the Kelvin unit cell demonstrated the most similar behavior to experimental test results. The Weaire–Phelan unit cell, while showing promising results in low and medium densities, demonstrated unstable behavior at high impact velocity. The lattice structures with high fractions of vertical walls (truncated cube and rhombicuboctahedron) showed higher stiffness and first peak stress values as compared to lattice structures with high ratio of oblique walls (Weaire–Phelan and Kelvin). However, as for the energy absorption capacity, other factors were important. The lattice structures with high cell wall surface area had higher energy absorption capacities as compared to lattice structures with low surface area. The results of this study are not only beneficial in determining the proper unit cell type in numerical modeling of dynamic behavior of closed-cell foams, but they are also advantageous in studying the dynamic behavior of additively manufactured lattice structures with different topologies.

Performance Impacts of Tailored Surface Geometry in Li-Ion Battery Cathodes

2013 ◽  
Author(s):  
George J. Nelson
Keyword(s):  
Surface Area ◽  
Solid Phase ◽  
Particle Surface ◽  
Surface Characteristics ◽  
Analytical Models ◽  
Li Ion Battery ◽  
Fractal Structures ◽  
Surface Geometry ◽  
Trade Offs ◽  
Li Ion

Analytical models developed to investigate charge transfer in Li-ion battery cathodes reveal distinct transport regimes where performance may be limited by either microstructural surface characteristics or solid phase geometry. For several cathode materials, particularly those employing conductive additives, surface characteristics are expected to drive these performance limitations. For such electrodes gains in performance may be achieved by modifying surface geometry to increase surface area. However, added surface area may present a diminishing return if complex structures restrict access to electrochemically active interfaces. A series of parametric studies has been performed to better ascertain the merits of complex, tailored surfaces in Li-ion battery cathodes. The interaction between lithium transport and surface geometry is explored using a finite element model in which complex surfaces are simulated with fractal structures. Analysis of transport in these controlled structures permits assessment of scaling behavior related to surface complexity and provides insight into trade-offs in tailoring particle surface geometry.

scholarly journals Experimental Dust Inhalation in Guinea-Pigs

1931 ◽  
Vol 31 (1) ◽  
pp. 96-123 ◽  
Author(s):  
F. Haynes
Keyword(s):  
Aluminium Hydroxide ◽  
Harmful Effect ◽  
Alveolar Epithelium ◽  
Lung Parenchyma ◽  
Magnesium Carbonate ◽  
Soluble Form ◽  
Alveolar Wall ◽  
Inhaled Particles ◽  
Pulmonary Damage ◽  
Soluble Silica

The following dusts produce a fibrosis in the guinea-pig's lung, and are therefore to be classed as dusts whose inhalation in industry would be attended by risks of pneumoconiosis. The most deadly of all dusts examined was precipitated silica. Less dangerous, but all producing fibrosis, were the following, arranged in order of decreasing toxicity: flint, slate, aluminium hydroxide, precipitated chalk, magnesium carbonate and carborundum. In the concentrations used in the experiments calcspar and emery were border-line dusts, indicating that their inhalation in any considerable quantity would cause fibrosis. Wood charcoal inhaled in large amount produces a slight fibrosis, and must, therefore, be placed on the “dangerous” list. Colloidal coal, when inhaled in massive amounts, is potentially dangerous, while shale under similar conditions is rather more dangerous.Haematite, talc, and molecular mixtures of soluble silica with aluminium hydroxide and magnesium carbonate respectively were not found to cause any permanent lesions in the lung.The deductions to be drawn from this work are:1. All inhaled particles are rapidly ingested by certain individual cells belonging to the alveolar epithelium.2. These cells (dust cells or phagocytes) remain in the lung parenchyma until they have ingested an amount of dust constituting the cell's saturation load. This load varies with different dusts.3. A cell having attained its saturation load becomes sooner or later detached from the alveolar wall and either migrates into the lymphatics or becomes free in the alveolus. In the former case it passes into the pulmonary lymphoid tissue and thence to the bronchial lymph glands. In the latter case it passes up the bronchial tree to be either coughed out or swallowed.4. Dust cells which speedily leave the alveolar wall are principally eliminated by the bronchi.5. In the case of a dust cell being eliminated from the lung via the lymphatics, it may be arrested in the periatrial lymphatics on account of its bulk. The dam thus produced offers obstruction to the passage of other dust cells shed into the alveoli. Groups of free dust cells in the obstructed alveoli form plaques, which degenerate and liberate their dust. This is again ingested, and the irritation caused by such a process may lead to fibrosis.6. The continued presence of dust-laden cells in the lymphatics may set up a foreign body irritation, with resulting fibrosis.7. Most inhaled particles contain soluble matter to at least a very small extent. The solute may be either harmlessly active or toxic. If the former, the cell is stimulated to detach itself from the alveolar wall, and so remove the dust. If the latter, the solute effects the viability of the phagocyte, which becomes less able to detach itself. At the same time the solute diffuses into the neighbouring tissues, with irritation to them, and consequent fibrosis.8. The more soluble form of a substance causes greater pulmonary damage than the less soluble. The solute, therefore, plays a large part in the determination of damage.9. While many dusts cause pulmonary fibrosis, silica is the dust par excellence predisposing to tuberculosis. This is doubtless due to its influence in forming a medium suitable not only for the survival but the proliferation of the tubercle bacillus in the lung (Kettle, private communication). The harmful effects of soluble silica may be neutralised by simultaneous administration of basic dusts such as aluminium hydroxide or magnesium carbonate, though the latter are themselves harmful when inhaled alone. It is suggested that their respective solutes combine to form monosilicate. Monosilicates do not appear to have any harmful effect on the lung.10. Heavy inhalations of any dust are liable to cause pulmonary damage.11. The intensity of the initial pulmonary reaction to a dust is very generally in inverse ratio to the degree of eventual damage caused by the dust.

scholarly journals The Amounts of Water Adsorbed to the Surface of Clay Minerals at the Plastic Limit

2017 ◽  
Vol 64 (3-4) ◽  
pp. 155-162
Author(s):  
Aleksandra Gorączko ◽  
Andrzej Olchawa
Keyword(s):  
Surface Area ◽  
External Surface ◽  
Solid Phase ◽  
Water System ◽  
Basal Spacing ◽  
Plastic Limit ◽  
X Ray Diffraction ◽  
External Surface Area ◽  
X Ray ◽  
Water Layers

AbstractThe paper presents results of a study on the amount of water associated with the solid phase of the clay water system at the plastic limit. Two model monomineral clays, namely kaolinite, and montmorillonite, were used in the study. The latter was obtained by gravitational sedimentation of Na-bentonite (Wyoming).The calculated mean number of water molecule layers on the external surface of montmorillonite was 14.4, and water in interlayer spaces constituted 0.3 of the water mass at the plastic limit.The number of water layers on the external surface of kaolinite particles was 63, which was related to the higher density of the surface electrical charge of kaolinite compared to that of montmorillonite.The calculations were made on the basis of the external surface area of clays and the basal spacing at the plastic limit measured by an X-ray diffraction test. The external surface area of clays was estimated by measuring sorption at a relative humidity p/p0 = 0.5.

Experiment on the Attenuation Characteristics of Shock Wave Interacting with Open and Closed Foam

2014 ◽  
Vol 1035 ◽  
pp. 445-452
Author(s):  
Jian Wang ◽  
Bao Gui Wang ◽  
Gang Tao
Keyword(s):  
Shock Wave ◽  
Internal Friction ◽  
Dynamic Behavior ◽  
Solid Phase ◽  
Experimental Results ◽  
Reflection And Transmission ◽  
Attenuation Characteristics

For understanding the dynamic behavior of open and closed foam subject to a shock wave, this paper through experiments, to gain a deeper understanding of the incidence, reflection and transmission of a shock wave when it interacted with cellular foam. Moreover, by analyzing the loss of the peak overpressure and positive impulse, we were able to respectively know the positive impulse of the incidence, reflection and transmission shock wave. The experimental results indicated that the attenuation capability for foam to the shock wave was caused by the internal friction and deformation of solid phase, which would absorb the energy of the shock wave. From the results we gain an understanding that the mechanical phenomenon of open foam to shock wave are not fully consistent with those of closed foam , while the attenuation of open foam to shock wave is more effective than that of closed foam.

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