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.

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.

scholarly journals Separation of Radionuclides from a Rare Earth-Containing Solution by Zeolite Adsorption

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 20
Author(s):  
Deniz Talan ◽  
Qingqing Huang
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
Contact Time ◽  
Separation Efficiency ◽  
Ph Value ◽  
Solid Phase ◽  
Separation Performance ◽  
Solution Ph ◽  
Zeolite Sample ◽  
Alternative Sources

The increasing industrial demand for rare earths requires new or alternative sources to be found. Within this context, there have been studies validating the technical feasibility of coal and coal byproducts as alternative sources for rare earth elements. Nonetheless, radioactive materials, such as thorium and uranium, are frequently seen in the rare earths’ mineralization, and causes environmental and health concerns. Consequently, there exists an urgent need to remove these radionuclides in order to produce high purity rare earths to diversify the supply chain, as well as maintain an environmentally-favorable extraction process for the surroundings. In this study, an experimental design was generated to examine the effect of zeolite particle size, feed solution pH, zeolite amount, and contact time of solid and aqueous phases on the removal of thorium and uranium from the solution. The best separation performance was achieved using 2.50 g of 12-µm zeolite sample at a pH value of 3 with a contact time of 2 h. Under these conditions, the adsorption recovery of rare earths, thorium, and uranium into the solid phase was found to be 20.43 wt%, 99.20 wt%, and 89.60 wt%, respectively. The Freundlich adsorption isotherm was determined to be the best-fit model, and the adsorption mechanism of rare earths and thorium was identified as multilayer physisorption. Further, the separation efficiency was assessed using the response surface methodology based on the development of a statistically significant model.

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 Analysis of the Chloroacetanilide Herbicides in Water Using SPME with CAR/PDMS and GC/ECD

2005 ◽  
Vol 88 (4) ◽  
pp. 1236-1241 ◽  
Author(s):  
Ying-Ming Hwang ◽  
Yih-Gang Wong ◽  
Wu-Hsiung Ho
Keyword(s):  
Humic Acid ◽  
Ph Value ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Standard Addition ◽  
Electron Capture Detection ◽  
Detection Analysis ◽  
Salt Addition ◽  
Chloroacetanilide Herbicides ◽  
Relative Standard

Abstract The solid-phase microextraction (SPME) technique using a 75 mm film of carboxen/polydimethylsiloxane was applied to the analysis of chloroacetanilide herbicides (acetochlor, alachlor, butachlor, metolachlor, and propachlor) residues. The feasibility of SPME with gas chromatography electron capture detection analysis has been evaluated. The effects of experimental parameters such as magnetic stirring, salt addition, humic acid addition, pH value, and extraction time, as well as desorption temperature and time, were investigated. Analytical parameters such as linearity, repeatability and limit of detection were also evaluated. The inhibition of humic acid to the extraction of chloroacetanilide herbicides was observed. A standard addition method for calibration was recommended to reduce deviations caused by matrix interferences. The proposed method provided a simple and rapid analytical procedure for chloroacetanilide herbicides in water with limits of detection 0.002–0.065 μg/L for deionized water, and 0.005–0.22 μg/L for farm water. The relative standard deviations (n = 5) for analyses of farm water were 7–20% for 0.5 μg/L chloroacetanilide herbicides. This application was illustrated by the analysis of sample collected from farm water in the Chung-hwa area, Taiwan.

An Improved Method for the Quantification of Thiamine (Vitamin B1) in Cocoa-Containing Beverage Powders

2017 ◽  
Vol 100 (5) ◽  
pp. 1511-1515
Author(s):  
Frédéric Martin ◽  
Liliane Meyer ◽  
Konstantinos Zelianos ◽  
Esther Campos Gimenez
Keyword(s):  
Ph Value ◽  
Solid Phase ◽  
Vitamin B1 ◽  
Water Soluble ◽  
Local Market ◽  
Improved Method ◽  
Test Portion ◽  
Beverage Samples ◽  
Water Soluble Vitamin ◽  
Thiamine Content

Abstract The purpose of this work was to understand low recoveries of thiamine (vitamin B1) when extracted from cocoa-containing beverage powders fortified with water-soluble vitamin B1, and to develop and validate a new procedure to improve these results. Based on the literature, previous trials have focused on two main factors: pH value prior to paper filtration and the need for solid-phase extraction (SPE) clean up. We demonstrate that by following European Standard EN 14122, recovery of thiaminein cocoa-containing beverage powders is low and dependent on the test portion (86 and 72% for 0.5 and 1.5 g test portions, respectively). Our improved method resolved this problem by keeping the pH low (around 1) prior to paper filtration, leading to a 96.3% recovery and high precision (RSDr of 3.5%). The use of strong cation-exchange SPE cartridges for cleanup prior to the thiamine oxidation reaction proved to be essential. A comparison between our improved method and EN 14122 on nine cocoa-containing beverage samples available on local market from different manufacturers showed a systematic increase in thiamine content (up to 70%) when the improved methodwas applied. The highest difference was observed forthe sample that contained the highest amount of cocoa. However, for beverage powders that contained bothcocoa and milk, no difference was observed.

scholarly journals The Physicomechanical Deterioration Characteristics and Mesoscopic Damage Analysis of Sandstone under Acidic Environment

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Runke Huo ◽  
Tian Qiu ◽  
Yanling Liang ◽  
Shuguang Li ◽  
Meiting Qian
Keyword(s):  
Elastic Modulus ◽  
Dissolution Rate ◽  
Ph Value ◽  
Acidic Environment ◽  
Quality Change ◽  
Soaking Time ◽  
Rock Samples ◽  
Peak Point ◽  
Function Relationship ◽  
Deterioration Characteristics

The physicomechanical deterioration characteristics of sandstone subjected to H2SO4, HCl, and H2O solutions of different pH values are studied by the method of long-term accelerated immersion. The quantitative relationships between the damage variables based on CT (computer tomographic identification technology) numbers and the immersion time, the uniaxial compressive strength, the peak point strain, and the elastic modulus of rock samples are analyzed. The test results indicate that the pH value of immersion solutions, the dissolution rate of Ca2+ and Na+, and the quality change of rock samples show visible stage characteristics under acidic environment. With the soaking time extended, the pH value of solutions increases gradually, and the quality change of rock samples decreases gradually. The smaller the pH value of immersion solutions is, the higher the dissolution rate of Ca2+ and Na+ is. However, the cation dissolution rate under a weak acid environment with a high pH value has little difference with that under the distilled water (pH = 7). With the increase of the soaking time and the acidity, the compaction stage of rock samples becomes longer, the elastic stage becomes shorter, the deterioration degree of mechanical parameters becomes more extensive, and the destruction of sandstone samples shows ductility characteristics increasingly. The corrosion degree of corroded sandstone samples is quantitatively represented by microscopic damage variables based on CT numbers. The regression analysis results show that damage variables of acid-corroded sandstone samples have a power function relationship with soaking time and an exponential function relationship with peak strength, peak point strain, and elastic modulus.

Mechanical Properties and Corrosion Mechanism of GFRP Rebar in Alkaline Solution

2015 ◽  
Vol 665 ◽  
pp. 217-220
Author(s):  
Ji Ze Mao ◽  
Hong Wei Zhang ◽  
Jian Fu Lv ◽  
Dao Guang Jia ◽  
Shi Kai Ao
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Alkaline Solution ◽  
Concrete Structure ◽  
Ph Value ◽  
Unsaturated Polyester ◽  
Alkali Resistance ◽  
Resin Matrix ◽  
Corrosion Mechanism ◽  
Mechanical Properties And Corrosion

Steel corrosion is one of the main problems of concrete structure durability. Compared with the steel, GFRP rebar has the advantages of high strength, low density and good corrosion resistance. Therefore, GFRP becomes a good choice to replace steel bar in concrete structure. Since GFRP material is susceptible to the alkaline conditions, it is necessary to clarify the mechanical properties and corrosion mechanism of GFRP rebar in such an alkaline environment of interior concrete. In this study, the artificial accelerated corrosion tests of two kinds of GFRP rebar (epoxy and unsaturated polyester resin matrix) were conducted at 60 °C in alkaline solution up to 90 days. Then the tensile strength tests of GFRP rebar were carried out. The solution PH values, the tensile strength and mass loss of GFRP rebar were measured. The testing results show that the mass of GFRP rebar had rarely changed, but the tensile strength reduced about 30% after 90-day immersion test in alkaline solution. During the test, the PH value of the alkaline solution decreased from 13.62 to around 12.85, which indicated that the hydroxyl ions of the alkaline solution had been consumed. The ester bonds in resin matrix may hydrolyze in alkaline solution and the bonding interface between fiber and resin can be damaged progressively. It can cause the performance degradation of GFRP rebar. In addition, the relationship between the loss of tensile strength and the reduction of PH can be determined. That means the durability of GFRP rebar in concrete can be enhanced by controlling or limiting the alkalinity when producing concrete. Finally, the GFRP rebar of epoxy resin matrix shows higher retention values of tensile strength and better alkali resistance than those of UPR matrix rebar after 90d immersion in the alkaline solution. The obtained results in this paper can provide application reference of GFRP materials in civil engineering.

Efficient Expansion of Lymphocytes in a Culture System with Solid Phase Anti-CD3 and Anti-CD28 Monoclonal Antibodies.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3648-3648
Author(s):  
Atsuko Soeda ◽  
Atsushi Kondo ◽  
Hiroaki Makiyama ◽  
Yuriko Morita ◽  
Noriko Takahashi ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Clinical Trials ◽  
Monoclonal Antibodies ◽  
Lymphocyte Proliferation ◽  
Culture System ◽  
Solid Phase ◽  
Soluble Form ◽  
Killing Activity ◽  
Culture Plate ◽  
Phase Culture

Abstract [Background] In vitro cell expansion in culture with solid phase anti-CD3-mab (aCD3mab) is a standard method for lymphocyte proliferation and activation. However, clinical trials using activated lymphocytes with this system provided only minimal efficacy. Recently, aCD3mab/aCD28mab-coated micro-bead (aAPC) was developed as a novel tool to efficiently expand lymphocytes, and has been used in several clinical trials. This study was designed to evaluate the effects of solid phase aCD3mab/aCD28mab on the proliferation and activation of lymphocytes to compare the results with culture using aAPC. [Methods and Results] Parameters to evaluate the efficacy of culture system included magnitude of cell proliferation, killing activity against K562 and various surface markers of cultured cells. Peripheral blood was obtained from healthy volunteers after an informed consent was obtained, and mononuclear cells (PBMNc) were separated by lymphosepal system. Firstly, we cultured PBMNc in system with solid phase aCD3mab/aCD28mab coated to a culture plate (Culture A) or with solid phase aCD3mab coated to a culture plate plus soluble form aCD28mab (Culture B) to seek an optimal condition in the solid phase for lymphocyte proliferation (Figures 1). The results showed that the optimal ratio of aCD3mab:aCD28mab for Culture A is 3:7 to yield fold-expansion of lymphocytes of 12–13, while this in Culture B with the same amount of monoclonal antibodies was 10 (n=6). There was no difference in the expression CD3, CD4 or CD8, and killing activity between expanded cells in Culture A and Culture B. Then, we compared optimized solid phase Culture A with liquid phase culture with aAPC (Culture C). As a result, cell proliferation in Culture A was 1.3–5.6 times higher and the killing activity was 1.1–1.8 times higher than Culture C (Figure 2). In Culture A, the cell expression of CD45RO and GITR was higher and that of CD161 was lower compared to Culture C (Figures 3). Solid phase culture system with aCD3mab/aCD28mab is efficient and easily applicable for the expansion of lymphocytes, however more detail characterization of the expanded cells, especially Treg function and in vivo survival, are necessary. Figure 1. Figure 1. Figure 2. Figure 2. Figure 3. Figure 3.

scholarly journals Preparation and characterization of activated carbon & amorphous silica from rice husk

2015 ◽  
Vol 50 (4) ◽  
pp. 263-270 ◽  
Author(s):  
MT Rhaman ◽  
MA Haque ◽  
MA Rouf ◽  
MAB Siddique ◽  
MS Islam
Keyword(s):  
Activated Carbon ◽  
Rice Husk ◽  
Amorphous Silica ◽  
Ph Value ◽  
Koh Activation ◽  
Silica Sample ◽  
Alkali Extraction ◽  
Sem Image ◽  
Value Measurement ◽  
Mb Adsorption

Activated carbon (AC) was prepared by the conventional carbonization and KOH activation and amorphous silica was extracted by alkali extraction followed by acid precipitation from rice husk on a laboratory scale. The performance of the produced activated carbon and amorphous silica were examined using I2 value measurement, methylene blue (MB) adsorption test, pH measurement, FTIR and SEM-EDX analysis. The optimum temperature for production of AC was obtained at 700 0C. The AC by alkali extraction method was show higher activity than KOH activation. The maximum I2 value, MB adsorption value & pH value shows at 700 0C followed by alkali extraction with 15% NaOH, which were 510.82 mg/g, 61.1 mg/g and 7.32 respectively. The FTIR analysis shows presence of Si-O-Si bond with a strong peak at 1078.28 cm-1. The SEM image of silica sample shows that the most of organic component is burnt out during combustion.Bangladesh J. Sci. Ind. Res. 50(4), 263-270, 2015

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