Characterization of aqueous rubidium chloride as an equitransferent ultraconcentrated salt bridge

From e.m.f. measurements on the concentration cells Ag|AgCl|RbCl (m)RbCl (m _f)|AgCl|Ag and Rb-amalgam|RbCl (m _f)RbCl (m)Rb-amalgam, the ion and solvent transference numbers have been determined for aqueous RbCl solutions at molalities up to 7 mol kg^–1 over the temperature range from 25 to 55°C. From the ionic transference numbers found, aqueous RbCl emerges as the most closely equitransferent salt bridge ever characterized. Considering also its high solubility (7.8 mol kg^–1 at 25°C), RbCl is recommended as a built-in salt bridge for reference electrodes, in view of replacing the insufficiently equitransferent KCl bridges so far adopted by manufacturers.     

The removal of radioactive caesium contaminants from simple aqueous solutions

Cs ions can be removed from aqueous solutions by forming a precipitate of copper ferrocyanide which, having occluded the Cs ions, can in turn be floated by means of an anionic collector. Collection was achieved with either α-sulphopalmitic acid or sodium dodecyl sulphate depending on what interfering ions were initially present in the solution. Recoveries of 98–99% were obtained on batch scale experiments and 97.5–98.5% on continuous scale operation. The investigations of the flotation parameters of pH, gas-rate, concentrations of precipitating reagents and collector, as well as the interference effects of other ions are discussed. Using data obtained in batch scale tests, continuous scale experiments were designed and operated.     

Characterization of a chiral menthyldimethyltin molybdate and its use as an olefin epoxidation catalyst

Vibrational spectroscopy and EXAFS studies of an organotin molybdate with the formula [((Me)₂(menthyl)Sn)₂MoO₄(H₂O)_3.5] reveal that the compound is polymeric and contains [MoO₄]²⁻ tetrahedra coordinated to [R₃Sn]⁺ cationic spacers. The compound can be used as a recyclable solid catalyst for the selective epoxidation of cyclooctene by tert-butylhydroperoxide. In the epoxidation of prochiral olefins such as trans-β-methylstyrene, the corresponding epoxide isomers are obtained with fairly good to excellent selectivity, albeit with low enantiomeric or diastereomeric excesses.     

Formulation of caesium based and caesium containing geopolymers

Abstract

Cement encapsulation is widely used as a low- and intermediate level radioactive waste immobilisation process. Among these wastes, caesium ions are poorly immobilised by Portland cement based materials. This work consists of an experimental investigation into the ability of geopolymers to effectively encapsulate this chemical species and to determine the impact of caesium incorporation on the geopolymer properties. Geopolymers were synthesised with several compositions based on the activation of metakaolin with an alkali hydroxide solution containing caesium. The setting time, mineralogy, porosity and mechanical properties of the samples were examined for one month. Leach tests were conducted during the same period to determine the immobilisation efficiency. The results depend to a large extent on the composition of the activation solution in terms of soluble silica content and alkali used. These parameters determine both the degree of condensation and the geopolymer composition.     

Oxygen depolarized electrolysis of sodium chloride by the use of a β-alumina-molten salt system

This paper is concerned with oxygen depolarized electrolysis of NaCl by the use of-alumina solid electrolyte and molten salts. In the electrolysis, dry chlorine gas and pure molten sodium hydroxide are produced from sodium chloride, oxygen and water. Because the oxygen reduction proceeds very smoothly in the molten sodium hydroxide, this process is very promising for the future. The theoretical decomposition voltage of this process is estimated to be 1.5 V, which is lower than that of the process without an oxygen cathode by 1.1 V. The model cell study shows that a terminal voltage of 3 V at 50 A dm^–2 is attainable.     

Surface analysis and adsorption behavior of caffeine as an environmentally friendly corrosion inhibitor at the copper/aqueous chloride solution interface

Abstract

Corrosion inhibitors based on environmentally friendly and harmless products are currently being studied and developed. The corrosion inhibition properties of caffeine (1,3,7-trimethylxanthine) on copper corrosion in aqueous chloride solution (3.5?wt.% NaCl) are analysed here using stationary and transient electrochemical methods, and a theoretical study based on density functional theory is carried out. Caffeine is a very competitive compared to the chemical inhibitors that are often used for copper protection. Electrochemical and impedance experiments reveal that the protective efficiency of caffeine reaches a value of 96% at a concentration of 10^?2?mol L^?1. Based on these results, the Langmuir model appears to be the best representation of the adsorption of caffeine onto the copper surface. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD) were used to determine the surface morphology and the chemical composition of the copper surface in chloride media, in the absence and presence of caffeine. The results show the development of a mechanism of corrosion inhibition. In order to confirm the correlation between the inhibitory effect and the molecular structure of caffeine, quantum chemical parameters are used to calculate its electronic properties.     

Synthesis and characterization of aqueous cationomeric polyurethanes and their use as adhesives

Aqueous cationomeric polyurethanes (ACPU) were synthesized by a multistep reaction process. The alipathic diisocyanate, e.g., hexamethylene diisocyanate (HDI), was reacted with polyol, e.g., polypropylene glycol (PPG400) to form a prepolymer and it was chain-extended by reacting it with N-methyldietanolamine (N-MEDA). Quarternization was then carried out by using dimethyl sulfate (DMS), acetic acid (HAc), or hydrochloric acid (HCI). The resultant cationomers were self-emulsified with deionized water. The effect of different percentages of N-MEDA in the polymer backbone on the structure and properties of ACPU were studied. Viscosity, thermal properties, electrolytic stability, and pH stability of the cationomeric polyurethanes were also studied along with the adhesion strengths between flexible and rigid surfaces. © 1996 John Wiley & Sons, Inc.     

Characterization of functionalized multiwalled carbon nanotubes and application as an effective filter for heavy metal removal from aqueous solutions☆

Filtration efficiency of Ni(II) from aqueous solution using pristine and modified MWCNTs filters was investigated as a function of Ni(II) ion concentration, pH, and filter mass. MWCNTs were synthesized by CVD method and modified using two complementary treatments, purification (using a mixture of hydrochloric acid and hydrogen peroxide) and functionalization (using nitric acid). The effect and mechanism of each treatment on the structural integrity of pristine MWCNTs has been studied. Morphology of the pristine and modified filters was investigated by Raman Spectrometry (RS), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared (FTIR) spectrometry and Thermogravimetric analysis. It was found from Raman spec-tra that the ratio of the intensity of D-band to that of G-band decreased by purification process, and increased by functionalization process. The adsorption mechanism of Ni(II) onto the surface functional groups of modified MWCNTs was confirmed by FTIR spectrum. The filtration results showed that the removal efficiency of Ni(II) is strongly dependent on pH and could reach 85%at pH=8. Also, modified MWCNT filters can be reused through many cycles of regeneration with high performance. Functionalized MWCNTs filters may be a promising adsor-bent candidate for heavy metal removal from wastewater.     

丁酸在含氯化钙双水相体系中的有效分离(英文)

One of the bottlenecks for bioproduction of butyric acid as bulk chemical is the difficulty in separating butyric acid from the fermentation broth,compared with the petroleum-based chemical synthesis method.In the present work,a novel separation methodology was developed based on an aqueous two-phase system with inor-ganic salts.Calcium chloride was screened out for effective separation of butyric acid from butyric acid-water-salt systems.Within appropriate concentration range of butyric acid and salt,butyric acid was enriched in the upper phase and most of calcium ions remained in the lower phase.This"salting out"effect is very efficient to separate butyric acid from the simulated butyrate fermentation broth,which consists of butyric acid and acetic acid with concentration ratio of 4︰1,so that the final ratio of butyric acid/acetic acid in the upper phase is improved to 9.87. The aqueous two-phase system was used to separate butyric acid from the actual fermentation broth with satisfac-tory result.     

Studies on an araldite-based membrane of copper hexacyanoferrate (III) as a caesium ion-sensitive electrode

Solid membranes of copper hexacyanoferrate (III) in araldite are evaluated as a caesium ion-sensitive electrode. The electrode can be used for caesium determination in the concentration range of 10⁻¹ to 10-⁴M . The potentials generated across the membrane are reproducible and steady potentials are attained in about 1 to 2min. The same electrode can be used over a period of 6 months without significant change in potential. The electrode can be used in the pH ranges 2.5–6.0 at 10⁻² M Cs⁺ and 3.0–6.0 at 10⁻³ M CS⁺, and in presence of a number of interfering ions. Potentiometric titration of caesium nitrate with 12-moIybdophosphoric acid was also carried out using the membrane as an end point indicator.     

A study of stripping uranium complex from an amine extract with aqueous salt solutions

The organic phase produced by extraction of a uranium leach liquor with Amberlite LA-2 in kerosene was stripped of uranium in laboratory tests with solutions of NaCl and H₂SO₄ or solutions of Na₂SO₄. It was found that NaCI-H₂SO₄ stripping reduced considerably the effectiveness of the solvent for subsequent extraction, whereas Na₂SO₄ stripped the uranium content without any deleterious effect. Optimum Na₂SO₄ concentration and pH for stripping were determined. Phase separation time and entrainment losses appear satisfactory.     

MgCl_2水溶液分子动力学模拟

采用分子动力学的方法 ,对无限稀释 Mg Cl2 水溶液进行了模拟。计算了包括 3个超临界点在内的 7个状态下无限稀释 Mg Cl2 水溶液中 Mg2 + - O,Mg2 + - H ,Cl- - O与 Cl- - H的径向分布函数 ,Mg2 + -水 (质心 )和 Cl- -水 (质心 )的配位数。采用均方位移与速度自相关函数两种方法计算了 Mg2 + 、Cl- 的扩散系数。计算结果表明 ,Mg2 + 有较强的第二层水化。超临界状态下 ,Mg2 + 与 Cl- 间有着较强的缔合作用。模拟得到的扩散系数与仅有的常温下实验数据相一致     

The conductivity of aqueous zinc chloride solutions

The conductivity of aqueous zinc chloride reaches a maximum of 10.7 ^–1 m^–1 at 3.7 M ZnCl₂. Measurements on chlorinated ZnCl₂ showed that at low chlorine concentrations, the conductivity increased linearly with the square root of the chlorine concentration. The increase was due to the three species: dissolved chlorine, Cl ₃ ^– and HClO. Ammonium chloride additions increased the conductivity of aqueous zinc chloride substantially.     

钠钙氯化物在乳糖水中热力学性质的确定

在298.15 K时利用电动势法确定四元体系氯化钠-氯化钙-乳糖-水不同组成(乳糖质量分数分别为0,5%,10%和15%)时的热力学性质。利用Pitzer离子作用模型拟合实验数据,获得了氯化钠和氯化钙在乳糖水混合溶剂中的Pitzer模型参数。进一步计算了氯化钠和氯化钙从纯水到乳糖水混合溶剂中的迁移吉布斯函数。获得了氯化钠和氯化钙混合电解质在乳糖水混合溶剂中的混合参数θ(Na Ca)和ψ(Na Ca Cl)。计算了298.15 K时四元体系中氯化钠和氯化钙的平均离子活度系数。结果发现:利用Pitzer高阶静电作用模型计算混合电解质在混合溶剂中的平均离子活度系数,能获得较为满意的结果。     

氯化镁盐分析方法试验研究

氯化镁盐主要成分是氯化镁、氯化钾镁及其水化物,常含有氧化镁、氢氧化镁、硫酸镁等杂质。氯化镁盐常规分析方法是采用化学分析。采用化学分析方法经常出现2个问题：1）氯化镁盐极易吸潮,定量分析困难;2）分析出的镁含量包含了非氯化镁盐中的镁,如氧化镁、氢氧化镁中的镁。针对以上问题提出了一种综合分析方法,主要利用X射线衍射仪进行测试,配合常规的物理、化学分析手段。实验结果表明,该方法操作较为简便,定量效果较好,能够满足工业生产需要,是一种较为理想的分析方法。     

Synthesis of cationic flocculant by radiation-induced copolymerization of methyl chloride salt of N,N-dimethylaminoethyl methacrylate with acrylamide in aqueous solution

The radiation-induced copolymerization of the methyl chloride salt of N,N-dimethylaminoethyl methacrylate (DMAEM·MC) with acrylamide (AAm) was used to prepare a cationic polymer flocculant. The polymerization rate increased with increasing dose rate, polymerization temperature, monomer concentration and mole fraction of AAm in the monomer mixture. The molecular weight of the copolymer was also found to increase with monomer concentration and mole fraction of AAm, but at high concentration and fraction of AAm, intermolecular crosslinking tends to occur during the polymerization to form water-insoluble copolymer. A water-soluble copolymer having various molecular weights and cationic strengths can be synthesized by selecting suitable reaction conditions; i.e., this radiation process can provide a much higher molecular weight copolymer with a wide range of cationic strength. The flocculation effect was evaluated using sludge from wastewater of sugar manufacture. It was found that the radiation-polymerized copolymer DMAEM·MC–AAm has an excellent flocculation effect.     

Molar volumes of aqueous acetic acid-ammonium salt solutions

The mean apparent molar volumes φ_v of the CH₃COOHNH₄X(X  Cl, Br, NO₃) solutions have been determined at 40° from precise density measurements. The modified Young's rule for electrolyte-nonelectrolyte mixtures has been used to predict mean apparent molar volume, φ_v, from the pure water data. The modified Young's rule was found to be applicable for the CH₃COOHNH₄X systems to some extent. The deviations from the Young's rule approximation are studied as excess volumes of mixing of CH₃COOH and NH₄X solutions.