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Comparative Study of Various Preparation Methods of Colloidal Silica

Engineering（科研） 2010年第12期2卷 998-1005页

作者： Hyung Mi Lim Jinho Lee Jeong-Hwan Jeong Seong-Geun Oh Seung-Ho Lee 不详

Colloidal silica can be prepared by various methods and starting materials including ion exchange of aqueous silicates, hydrolysis and condensation of silicon compounds, direct oxidation of silicon, and milling and peptization of silica powder. Various silica sols having particle sizes of 10-60 nm prepared by these methods and the preparation methods have been compared on the basis of their shape, size uniformity, sphericity, stability against pH variation, cation concentration, and price, etc. Silica sol prepared from tetraethoxysilane affords uniform size control and growth, and high purity, despite the relatively high costs. Silica sol prepared from liquid silicates affords relatively easy size and shape control;however, it is difficult to lower the alkali content to a level that is appropriate for carrying out semiconductor chemical mechanical polishing processes;in addition, the waste water treatment carried out for recovering the ion exchange resin gives rise environmental consideration. The properties of colloidal silica prepared from fumed silica powder by milling and dispersion depend on the starting silica source and it is relatively difficult to obtain monodispersed particles using this method. Colloidal silica prepared from silicon by direct oxidation has a monodispersed spherical shape and purity control with reasonable prices. It generates less waste water because it can be directly produced in relatively high concentrations. The cation fraction located in the particle relative to the free cation in the fluid is relatively lower in the silica sol prepared by the direct oxidation than others. A careful comparison of colloidal silica and the preparation methods may help in choosing the proper colloidal silica that is the most appropriate for the application being considered.

关键词： Colloidal Silica Comparison Preparation Methods Shape cation Location

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The Effects of Zinc and Other Divalent cations on M-Current in Ventral Tegmental Area Dopamine Neurons

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Journal of Biomedical Science and Engineering 2014年第14期7卷 1075-1087页

作者： Susumu Koyama Munechika Enjoji Mark S. Brodie Sarah B. Appel Department of Physiology and Biophysics University of Illinois at Chicago College of Medicine Chicago USA Department of Physiology and Biophysics University of Illinois at Chicago College of Medicine Chicago USA Department of Clinical Pharmacology Faculty of Pharmaceutical Sciences Fukuoka University Fukuoka Japan

Ventral tegmental area dopamine (DA VTA) neurons are important for the reinforcing effects of drugs of abuse such as ethanol and nicotine. We have previously shown that M-current (IM) regulates the excitability of DA VTA neurons. Zinc (Zn2+) contributes to the regulation of neuronal excitation as a neuromodulator. In the present study, we investigated zinc effect on the properties of IM and the spontaneous firing frequency of DA VTA neurons. The standard deactivation protocol was used to measure IM during voltage-clamp recording with a hyperpolarizing voltage step to ﹣40 mV from a holding potential (VH) of ﹣25 mV. Zn2+ (100 μM) inhibited IM amplitude and IM recovered completely from the inhibition after the washout of Zn2+. Zn2+ inhibited IM in a concentration-dependent manner (IC50: 5.8 μM). When hyperpolarizing voltage steps were given to ﹣65 mV (in 10 mV increments) from a VH of ﹣25 mV, Zn2+ (100 μM) reduced IM amplitude at each voltage and zinc inhibition of IM was not voltage-dependent. Zn2+ increased the spontaneous firing frequency of DA VTA neurons in a concentration-dependent manner, suggesting that Zn2+ causes excitation of DA VTA neurons through an action on IM. IM of DA VTA neurons was inhibited by 100 μM divalent cations in increasing order of potency: Ba2+ (16%) 2+ (25%) 2+ (40%) 2+ (59%) 2+ (67%). These results suggest that Zn2+ may exert physiologically significant regulation of neuronal excitability in DA VTA neurons.

关键词： Divalent cation Dopaminergic Nystatin-Perforated Patch Recording Zinc

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Implication of Electrostatic Forces on the Adsorption Capacity of a Modified Brick for the Removal of Divalent cations from Water

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American Journal of Analytical Chemistry 2015年第1期6卷 11-25页

作者： Oscar Allahdin Michel Wartel Joseph Mabingui Abdel Boughriet Chaire Unesco “On the Management of Water” Lavoisier Laboratory of Hydrosciences Faculty of Sciences University of Bangui Bangui Central African Republic Laboratory of Geosystems and Analytical and Marine Chemistry University of Lille UMR CNRS 8217 BatC8 59655 Villeneuve d’Ascq cedex France Department of Chemistry I.U.T of Béthune University of Lille Northern France Rue de l’Université B.P.819 62408 Béthune Cedex France

Adsorption properties of brick for the removal of divalent cations increased significantly after this material were pre-activated by HCl and subsequently impregnated with ferrihydrite. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis demonstrated that ferrihydrite was preferentially attached to clays (mainly to metakaolinite) and possessed Na atoms at levels higher than those observed in iron-poor aggregates. Sodium is bound to hydroxyl groups which have a function as reactive sites and give rise to surface charge. Zeta potential measurements were conducted to determine the isoelectric point (IEP) and salt-addition method was used to assess the point of zero charge (PZC) of this brick. Modified brick has a positive charge in water up to pH ≈ 3.2 and negative charge above this pH. Moreover, pH was found to be the most important factor affecting the adsorption process, suggesting the possible implication of electrostatic forces at the brick-water interface. The complexation model proposed by James and Healy was applied to our system: theoretical data on free-energy changes due to effects associated both with electrostatic attraction and solvation, were found to be in agreement with those determined from kinetic experiments. Column experiments permitted further to show that adsorption reactions were strongly inhibited by addition of an inert electrolyte (like NaNO3). Under this condition, ionic strength increased and most surface sites of the brick would be occupied by Na+ ions, leading to a charge neutralization and thereby a depletion of electrostatic forces.

关键词： Brick Divalent cation Adsorption Electrostatic Forces Free Energy Coulombic Solvation

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Influence of Mg2+, Fe2+and Zn2+cations on 13C-18O Bonds in Precipitated Aragonite, Calcite and Dolomite: An ab InitioStudy

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Open Journal of Geology 2015年第5期5卷 254-267页

作者： Jie Yuan Key Laboratory of Earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Science Beijing China

The influence of metal cations on 13C-18O bonds in carbonates is still under debate. This paper used ab initio method to investigate this kind of influence of Mg2+, Fe2+ and Zn2+ cations on 13C-18O bonds in precipitated aragonite, calcite and dolomite. The polynomials of Δ47 and reduced partition function ratios (RPFRs) for 13/12C, 14/12C and 18/16O of these minerals were given within temperatures ranging from 260 to 1500 K. We found that these cations significantly decreased the Δ47 values at the level of 10-3 - 10-2 per mil, comparing with pure crystals;and that if the Δ47 values were used to reconstruct the temperatures Ts, the deviation of T was about 7.2°C for, for instance, zinc-enriched aragonite, as discussed in our paper. It was suggested that due to such influence, researchers would better use a proper thermometer according to the main impurity metal cations in carbonates. We also found that according to the probability theory, the theoretical value of the influence of phosphoric acid on Δ47 of CO2 degassed from different carbonates was zero.

关键词： Metal cation 13C-18O Bond Δ47 Phosphoric Acid ab Initio Calculation

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An Appraisal of Fluoride Distribution and Ionic Balance in Ground Water of Mundaragi Taluk, Gadag District, Karnataka, India: A Case Study

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Journal of Geoscience and Environment Protection 2021年第10期9卷 1-13页

作者： Aswini Arali K. Lokesh S. Manjappa B. Suresh Department of Civil Engineering Tontadarya College of Engineering Gadag Karnataka India Department of Chemistry University BDT College of Engineering Davangere Karnataka India Department of Civil Engineering Bapuji Institute of Engineering & Technology Davangere Karnataka India

A total, 25 different ground-water samples collected in Mundaragi taluk in of Gadag district, Karnataka, India to appraise the distribution of Fluoride. pH of collected groundwater is shown alkaline in nature and ranged between 7.18 and 9.32 with a mean value of 8.36. Fluoride content ranged between 0.86 to 4.63 mg/L in ground water samples, with minimum value 0.86 mg/L (MGK24) and maximum value 4.63 mg/L (MGK20). 48% of samples indicated fluoride content below 1.4 mg/L and 32% samples indicated fluoride content in between 2.0 and 3.0 mg/L. Followed by 8% of the samples showed fluoride content ranges above 3.1. The public from villagers have been used high fluoride-bearing groundwater for drinking prolonged period and suffering from fluorosis. Analytical values also predict that occurrence of minerals like apatite, fluorspar, topaz and mica gets processed naturally and releases fluoride into the lithosphere and percolates into ground water. The present study also helps find out a suitable adsorbent for removal of Fluoride in ground water. However, with respect to chemistry of water, the cation and anion balance of all the 25 groundwater samples were inside the recognized limit of ±10%. The fluoride content is maximum in Na+- type and low in Ca2+- type groundwater in the Mundaragi Taluk. Furthermore,

Fluoride cation Anion Behaviour Mundaragi Karnataka India

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The primary research on the environmental climatic records of the two snow pits recovered from Princess Elizabeth Land, Antarctica

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Chinese Journal of Polar Science 1999年第1期10卷 63-68页

作者：张明军李忠勤秦大河李军

Snow samples collected from two snow pits (2.5 m and 3.5 m deep) along the route of the 1996/1997 Chinese Antarctic Inland Expedition in Princess Elizabeth Land, East Antarctica, have been analyzed for chemical composition and oxygen isotope ratio. Annul accumulation layers can be well identified based on fluctuations of major anions (especially Cl -) and δ 18 O. However, no obvious seasonal variations of cation concentrations were found in the profiles. The results provide a useful tool for dating the snow stratum in this region. High sulfate (SO 2- 4) concentrations found in the two snow pit profiles for the periods of 1992 1995 may be due to the June 1991 Pinatubo (Philippines) volcanic eruption and August 1991 Cerro Hudson eruption in Chile.

关键词： Princess Elizabeth Land anion cation δ 18 O volcanic eruption.

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Comparative Study of Copper Adsorptivity and Selectivity toward Zeolites

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American Journal of Analytical Chemistry 2014年第7期5卷 395-405页

作者： Ponyadira Kabwadza-Corner Moses Wazingwa Munthali Erni Johan Naoto Matsue Laboratory of Applied Chemistry for Environmental Industry Faculty of Agriculture Ehime University Matsuyama Japan

The objectives of the study were to find the type and species of zeolite which gives optimum adsorption of copper, provide an explanation of the mechanism involved in the adsorption process and establish the selectivity sequence among zeolites. Adsorption of Cu onto zeolites and mont-morillonite as a reference was conducted at an initial Cu concentration range of 0 - 0.60 mM in the presence of 100 mM NH4NO3 at initial pH of 5. Langmuir and Freundlich models were used in analyzing the equilibrium data and a selectivity sequence derived from the Langmuir calculation was A4 > faujasite X > modernite > Na-P1 ≈montmorillonite ≈faujasite Y > clinoptilolite. Zeolites A4 and faujasite X had high adsorptive capacities of 1429 mmol·kg﹣1 and 909 mmol·kg﹣1, respectively. Zeolite A4 has the highest CEC among all the samples (6150 mmol·kg﹣1), and the adsorption capacity of Cu was largely influenced by the CEC of the samples. The adsorption mechanism was based on the exchange of Cu from solution with mostly Na which was the main exchangeable cation available. These results are important in selecting the most effective and suitable adsorbent for Cu removal from polluted environments.

关键词： Heavy Metals Cu Adsorption Selectivity Precipitation cation Exchange

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Al-Pillared Ghassoulite Clay as a New Green Catalyst for the Synthesis of Benzothiazoles and Benzimidazoles: Effect of Amine/CEC Ratio

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International Journal of Organic Chemistry 2013年第2期3卷 151-157页

作者： Rachid Azzallou Rachid Mamouni Kimberly Stieglitz Nabil Saffaj Mohammadine El Haddad Said Lazar Department of Science Technology Engineering and Mathematics (STEM) Biotechnology Division Roxbury Community College Boston USA Equipe de Chimie Analytique & Environnement Faculté Polydisciplinaire Université Cadi Ayyad Safi Morocco Equipe de Chimie Bio-Organique Appliquée Faculté des Sciences Université Ibn Zohr Agadir Morocco Laboratoire de Biochimie Environnement & Agroalimentaire URAC 36 Université Hassan II-MohammediaMohammedia Morocco Laboratoire de Chimie Faculté Polydisciplinaire Ouarzazate Morocco

The following article has been retracted due to the investigation of complaints received against it. The Editorial Board found that substantial portions of the text came from other published papers. The scientific community takes a very strong view on this matter, and the International Journal of Organic Chemistry treats all unethical behavior such as plagiarism seriously. This paper published in Vol.3 No.2, 151-157 (pages), 2013, has been removed from this site. Title: Al-Pillared Ghassoulite Clay as a New Green Catalyst for the Synthesis of Benzothiazoles and Benzimidazoles: Effect of Amine/CEC Ratio Authors: Rachid Azzallou,?Rachid Mamouni,?Kimberly Stieglitz,?Nabil Saffaj, Mohammadine Said

关键词： cation Exchange Capacity (x CEC) Benzimidazole Benzothiazole Catalyst Pillared

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New Method for Measurement of Plant Roots Specific Surface

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American Journal of Plant Sciences 2013年第5期4卷 1088-1094页

作者： Grzegorz , Jozefaciuk Malgorzata Lukowska Institute of Agrophysics of Polish Academy of Sciences Lublin Poland.

To provide enough space to carry all surface charges responsible for high cation exchange capacity of plant roots, large area of the root specific surface is necessary, however all experimental methods used up to date give too small surface area values. In this paper, we propose to measure the plant roots surface area using water vapor adsorption isotherm. This method gives roots specific surface areas compatible to CEC. Methodical aspects of the measurements are described along with theoretical background for calculating specific surface area on the example of roots of barley grown in nutrient solution.

关键词： Adsorption Isotherm Plant Roots Specific Surface Area cation Exchange Capacity

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Impact of Sulphate Counter Ion in the Migration of Sodium Ion through Soils

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Materials Sciences and Applications 2010年第2期1卷 46-52页

作者： P. V. Sivapullaiah Maya Nayak P. Hari Prasad Reddy J. Sumalatha 不详

Laboratory advection-diffusion tests are performed on two regional soils-Brown Earth and Red Earth-in order to assess their capacity to control contaminant migration with synthetic contaminant solution of sodium sulphate with sodium concentration of 1000 mg/L. The test was designed to study the transport/attenuation behaviour of sodium in the presence of sulphate. Effective diffusion coefficient (De) that takes into consideration of attenuation processes is used. cation exchange capacity is an important factor for the attenuation of cationic species. Monovalent sodium ion cannot usually replace other cations and the retention of sodium ion is very less. This is particularly true when chloride is anion is solution. However, sulphate is likely to play a role in the attenuation of sodium. cation exchange capacity and type of exchangeable ions of soils are likely to play an important role. The effect of sulphate ions on the effective diffusion coefficient of sodium, in two different types of soils, of different cation exchange capacity has been studied. The effective diffusion coefficients of sodium ion for both the soils were calculated using Ogata Bank’s equation. It was shown that effective diffusion coefficient of sodium in the presence of sulphate is lower for Brown Earth than for Red Earth due to exchange of sodium with calcium ions from the exchangeable complex of clay. The soil with the higher cation exchange retained more sodium. Consequently, the breakthrough times and the number of pore volumes of sodium ion increase with the cation exchange capacity of soil.

关键词： cation Exchange Capacity Clays Effective Diffusion Coefficient Hydraulic Conductivity Porous Media Sodium Sulphate

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