Behavior of Alkali Metal and Ammonium Salts in Nanofiltration of Their Aqueous Solutions

Radiochemistry - The behavior of salts (chlorides, nitrates, sulfates, phosphates, borates, ferri- and ferrocyanides) of various alkali metals (Li, Na, K, Cs) and ammonium in the course of...     

AZ61镁合金在不同pH值溶液中腐蚀行为研究

采用动电位极化扫描的方法研究了AZ61镁合金在水溶液中的腐蚀溶解行为,并用扫描电子显微镜和能谱仪对表面形貌和元素组成进行了观察和分析.结果表明,随着扫描电位的增大,镁合金依次经历阴极极化区、钝化区和阳极极化区.在阴极极化区,极化电流密度随极化电位的增大而减小;钝化区极化电流密度接近零,镁合金几乎不被腐蚀(氧化和溶解);在阳极极化区极化电流密度随极化电位的增大迅速增大,镁合金的溶解氧化与表面析氢加剧.而随着溶液pH值的升高,镁合金的腐蚀溶解及析氢速度降低,能谱分析显示,表面生成的Mg(OH)2覆盖膜,在酸性、中性和弱碱性溶液中,Mg(OH)2不能稳定存在;当溶液的pH值高于10后,Mg(OH)2是完全热力学稳定的,镁合金的钝化区电位范围随之变宽.     

Influence of Aging on the Physical-Mechanical Properties of Acrylic Resin Films Cast from Aqueous Dispersions and Organic Solutions

The physical-mechanical properties of the enteric copolymers, poly(methacrylic acid, ethyl acrylate) Eudragit® L100-55, and Eudragit® L30D have been investigated. Free films of the copolymer containing varying levels of glyceryl triacetate (triacetin) and citrate ester (Citroflex®) plasticizers were prepared by both aqueous and solvent casting techniques. Conditioned films were stored at different humidities and temperatures for predetermined time periods prior to testing. Free films with plasticizer concentration ranging from 0 to 30% by weight of the polymer demonstrated that physical aging at room temperature resulted in physical-mechanical changes as the stress-strain curves indicated a decrease in the percent elongation with increases in the tensile strength. Films prepared from the aqueous latex approached a constant state of equilibrium at a faster rate than films prepared from isopropyl alcohol, where the mechanical properties approach a relatively constant value. Free films containing varying amounts of the plasticizer, triethyl citrate, were stored under different humidity and temperature conditions. In addition, a headspace-gas chromatography (HSGC) method was developed to correlate solvent residues with mechanical properties. The results indicated that an increase in temperature and humidity accelerated the rate of solvent evaporation as a function of time. High vacuum and low humidity conditions were demonstrated to be ineffective conditions for solvent removal. Solvent residues were found in all films after 48 hours of exposure to temperatures up to 60°C and/or exposure to relatively high humidity conditions. A direct relationship between plasticizer content and rate of solvent evaporation from the film was established. Higher concentrations of the plasticizer were found to augment the evaporation of the solvents. This enhanced evaporation was due to the stronger molecular interaction forces between the polymer and the plasticizer than between the polymer and the solvent.     

Change in the pH of Solutions and the Cathodic Passivation of Metals under the Conditions of Electrochemical Protection in Aqueous Media

We propose a method for the computation of changes in pH^S of an electrolyte near the electrode in the cathodic reduction of dissolved oxygen. We show that, in the course of oxygen reduction with the limiting current in relatively acidic aqueous solutions (pH⁰3), an abrupt increase in pH^S (by 5–8 pH units) is possible. We describe the influence of a base electrolyte (KCl) and the thickness of the diffusion layer on the degree of alkalization of the electrolyte. In addition, we discuss the possible ways of practical application of the developed method.     

Mutual Influence of Lanthanides(III) in Their Joint Extraction from Aqueous Multicomponent Solutions with a Toluene Solution of Trialkylbenzylammonium Naphthenate

Extraction of lanthanides(III) [Sm(III)-Lu(III), including also yttrium(III)] from their aqueous multicomponent solutions with a toluene solution of trialkylbenzylammonium naphthenate was studied at 298 K and pH 3. Physicochemical and mathematical models describing distribution and mutual influence of lanthanides(III) [Ln(III)] in their joint extraction from multicomponent aqueous solutions were developed. Distribution of Ln(III) was studied as a function of the total concentration and composition of Ln(III) mixture in the aqueous phase taking into account that the Ln(III) extractable complexes (R₄N)₂[Ln(NO₃)₃A₂] (A is naphthenate anion) are formed in the organic phase.     

Ph值对BaTiO3水悬浮液性质的影响

研究了pH值对BaTiO3水悬浮液的颗粒带电特性、颗粒尺寸分布及流变特性的影响。找到了制备高分散的、稳定的BaTiO3悬浮液的最佳pH值。     

羟乙基纤维素溶液的触变性与反触变性

对于高分子流体流动特性的研究不仅能够判断该流体的应用价值,而且还可以用于分析流体内部的结构特点和结构演变过程,建立流体的结构与性能关系.以羟乙基纤维素(HEC)为研究对象,研究了HEC在水-乙醇和水-乙二醇溶液体系中的流动性质.结果表明,HEC/水-乙醇溶液会发生从触变性到反触变性的转变,溶液稳态黏度随着乙醇体积分数的增加先升后降;HEC/水-乙二醇溶液的流动特性更加复杂,虽然也会发生从触变性到反触变性的转变,但是,相对低浓度的HEC溶液的稳态黏度随乙二醇体积分数的增加线性增长,而相对高浓度的HEC溶液的稳态黏度却在乙二醇体积分数为15％和40％处出现两个极大值.结果表明:在体系中引入乙醇和乙二醇后,由于非溶剂效应以及两种醇分子与HEC分子间的氢键作用,使得HEC在溶液中产生了不同的聚集状态,该聚集状态在持续剪切的作用下又不断发生改变,从而影响了溶液的流动性质.     

Bulk Properties of the Aqueous Solutions of Barium Chloride

Experimental investigations of the density of the aqueous solutions of BaCl₂ at temperatures of 298–573 K and pressures up to 40 MPa have been carried out with the method of a constantvolume piezometer. The error of experimental data does not exceed 0.06%. The equation of state has been composed and the coefficients of thermal expansion and isothermal compressibility and the partial molar volumes of the electrolyte have been calculated on its basis.     

Thermodynamics of Aqueous Solutions of Alkyl p-Aminobenzoate

The solubilities of a series of alkyl p-aminobenzoates were determined in water at three temperatures. The solutes chosen were the methyl through the n-butyl p-aminobenzoates and the temperatures studied were 25°, 33° and 40°. These compounds present a chemically related series differing by methylene additions in incremental steps. The solubility determinations at various temperatures enabled calculation of thermodynamic elements in aqueous systems.

A recurrent non-linear pattern was obtained in the calculated and experimentally derived thermodynamic values of enthalpy, entropy, and free energy. However, an approximately linear relationship of chemical structure and the partial excess free energy for these solutes was found for these aqueous solutions.     

Thermal Conductivity of Aqueous Potassium Chloride Solutions

This paper presents new absolute measurements of the thermal conductivity of aqueous potassium chloride solutions using the transient coated-hot-wire technique. The data cover the range from 295 to 360 K at pressures slightly above the vapor pressures and over a concentration range of 0 to 3 mol·kg^–1. The instrument can be used to measure the thermal conductivity with a reproducibility of better than 0.2%, and a comparison of the present results with data available in the literature indicates that the uncertainty of the present data is better than 0.5%. An empirical correlation that reproduces the data within the claimed uncertainty is presented.     

Electrohydrodynamic 3D Printing of Aqueous Solutions

Among the various electrohydrodynamic (EHD) processing techniques, electrowriting (EW) produces the most complex 3D structures. Aqueous solution EW similarly retains the potential for additive manufacturing well-resolved 3D structures, while providing new opportunities for processing biologically derived polymers and eschewing organic solvents. However, research on aqueous-based EHD processing is still limited. To summarize the field and advocate for increased use of aqueous bio-based materials, this review summarizes the most significant contributions of aqueous solution processing. Special emphasis has been placed on understanding the effects of different printing parameters, the prospects for 3D processing new materials, and future challenges.     

Thermal Transitions in Gelatin and Aqueous Gelatin Solutions

On the basis of the characteristic enthalpy changes associated with glass transformation, the glass transition (T_g) in gelatin can be detected readily, in addition to the helix-to-coiltransition, by difTerential scanning calorimetry, and the effects of water content on these transitions can be measured directly. The thermal behaviour of aqueous, deionized bone-gelatin systems with up to about 20 wt";' water is typical of amorphous or partially amorphous polymer-diluent systems depending upon the amount of gelatin structural order developed. Extrapolations of the T_g data to the T_g reported for water and of the helix-to-coiltransition data to that reported for aqueous gelatin solutions containing 90 wt% water are reasonable. Further, the T_g data suggest that the equilibrium water contents of aqueous gelatin systems containing gelatin structural order are higher than those of structureless systems at corresponding relative humidities.     

Effect of Zinc-Ion on Indomethacin Degradation in Alkaline Aqueous Solutions

Kinetic studies have revealed that indomethacin degradation in the presence or absence of zincion at different temperatures in alkaline aqueous solutions followed an apparent firstorder rate constants. The rate constant-hydroxideion concentration profile was linearj _with a positive slope, suggesting the following rate lawt: k _obs = k₁ [OH]. There was no significant difference in activation energy and other parameter values calculated for indomethacin degradation in the presence or absence of zincion. Hence, zincion was found to have no effect on its degradation.     

Nanofiltration Extraction of Uranium and Thorium from Aqueous Solutions

Radiochemistry - The behavior of uranium and thorium ions in nanofiltration (NF) from aqueous solutions has been studied. It was shown that the retention capacity (R) of the NF membrane for uranium...     

Effect of Zinc-Ion on Indomethacin Degradation in Alkaline Aqueous Solutions

Abstract

Kinetic studies have revealed that indomethacin degradation in the presence or absence of zincion at different temperatures in alkaline aqueous solutions followed an apparent firstorder rate constants. The rate constant-hydroxideion concentration profile was linearj with a positive slope, suggesting the following rate lawt: k _obs = k₁ [OH]. There was no significant difference in activation energy and other parameter values calculated for indomethacin degradation in the presence or absence of zincion. Hence, zincion was found to have no effect on its degradation.     

Thermophysical Properties of Aqueous Solutions Near the Equilibrium Freezing Temperature

Measurements of the surface tension, viscosity, and thermal conductivity of LiBr and LiSCN aqueous binary solutions have been performed to determine the thermophysical properties near the equilibrium freezing temperature. A differential capillary-rise method for surface tension and the transient hot-wire method for thermal conductivity were employed. Furthermore, a rotational viscometer was utilized for the measurement of viscosity. Correlation equations for the data of the aqueous binary test solutions as a function of temperature and concentration are presented.     

分散剂对纳米LiBr溶液稳定性的影响

文章在论述分散剂增强纳米流体分散稳定性的基础上,通过添加E414和C6H5O7（NH4）,验证分散剂增强纳米LiBr溶液的分散稳定性,通过测量分别添加异辛醇（C8H18O）、壬醇（C9H20O）和癸醇（C10H220）基液的表面张力,发现分散剂也能增强纳米LiBr溶液表面张力的稳定性,主要因为表面张力和汽化成核临界功之间存在相关性,因此,分散剂同样能增强纳米LiBr溶液沸腾温度的稳定性。