An Aqueous Thermodynamic Model for the Complexation of Sodium and Strontium with Organic Chelates Valid to High Ionic Strength. I. Ethylenedinitrilotetraacetic Acid (EDTA)

An aqueous thermodynamic model is developed, which accurately describes the effects of Na⁺ complexation, ionic strength, carbonate concentration, and temperature on the complexation of Sr²⁺ by ethylenedinitrilotetraacetic acid (EDTA) under basic conditions. The model is developed from the analysis of literature data on apparent equilibrium constants, enthalpies, and heat capacities, as well as on an extensive set of solubility data on SrCO₃(c) in the presence of EDTA obtained as part of this study. The solubility data for SrCO₃(c) were obtained in solutions ranging in Na₂CO₃ concentration from 0.01 to 1.8 m, in NaNO₃ concentration from 0 to 5 m, and at temperatures extending to 75C. The final aqueous thermodynamic model is based upon the equations of Pitzer and requires the inclusion of a NaEDTA^3– species. An accurate model for the ionic strength dependence of the ion-interaction coefficients for the SrEDTA^2– and NaEDTA^3–aqueous species allows the extrapolation of standard state equilibrium constants for these species, which are significantly different from the 0.1 m reference state values available in the literature. The final model is tested by application to chemical systems containing competing metal ions (i.e., Ca²⁺) to further verify the proposed model and indicate the applicability of the model parameters to chemical systems containing other divalent metal-EDTA complexes.     

Thermodynamic Studies of the Complexation between Neodymium and Acetate at Elevated Temperatures

Complexation of neodymium (III) with acetate in 2.2 mol-kg^-1 NaClO₄ solution was studied at elevated temperatures (45 and 70°C) by potentiometry, calorimetry, and optical spectroscopy. The formation constants of the consecutive complexes, Nd(OOCCH₃),²⁺ Nd(OOCCH₃) ₂ ⁺ , and Nd(OOCCH₃)₃, and the molar enthalpies of complexation at these temperatures were determined. The stability of the three complexes increases with increased temperatures, because of increased positive entropy change at higher temperatures, which exceeds the increased values of the positive (endothermic) enthalpy. The molar heat capacity changes of complexation C_p,m(MLj) (J-K^-1-mol^-1) for Nd(OOCCH₃) _j ^(3-j)+ in the temperature range from 25 to 70°C were calculated to be: 102 ± 13 (j = 1); 122 ± 19 (j = 2); and 239 ± 27 (j = 3). The effect of temperature on the complexation is discussed in terms of the electrostatic model.     

Application of Pitzer's Equations for Modeling the Aqueous Thermodynamics of Actinide Species in Natural Waters: A Review

A review of the applicability of Pitzer's equations to the aqueous thermodynamics of actinide species in natural waters is presented. This review includes a brief historical perspective on the application of Pitzer's equations to actinides, information on the difficulties and complexities of studying and modeling the different actinide oxidation states, and a discussion of the use of chemical analogs for different actinide oxidation states. Included are tables of Pitzer ion–interaction parameters and associated standard state equilibrium constants for each actinide oxidation state. These data allow the modeling of the aqueous thermodynamics of different actinide oxidation states to high ionic strength.     

Spectrophotometry and Luminescence Spectroscopy of Acetohydroxamate Complexes of Trivalent Lanthanide and Actinide Ions

The complexation chemistries of acetohydroxamic acid (HA) with the trivalent Eu, Tb and Cm ions have been probed by combinations of Optical Absorbance Spectroscopy (OAS), Time Resolved Laser Induced Fluorescence Spectroscopy (TRLIFS) and emission spectroscopy, with some rather unexpected trends being observed. The formation of four complexed species was established for all three metal cations by OAS. The magnitudes of the formation constants of the respective M(A) _n ³⁻ⁿ complexes suggested a much stronger binding efficiency of HA for the first two complexation steps than the third and fourth steps. Tb(III) and Eu(III) TRLIFS data both suggested a final octadentate tetrakis-hydroxamato complex in which the metal ion is close to being fully dehydrated. Step-wise dehydration of Tb(III) by successive ligands did not appear to proceed as expected for a bidentate ligand. Of the EuA _n complexes, only the tetrakis species was found to luminesce, with HA causing an unusually strong quenching effect for all other Eu species. Cm(III) complexation appeared similar to the lanthanide analogs.     

An Aqueous Thermodynamic Model for the Complexation of Sodium and Strontium with Organic Chelators Valid to High Ionic Strength. II. N-(2-Hydroxyethyl)ethylenedinitrilotriacetic Acid (HEDTA)

This is the second paper in a two part series on the development of aqueous thermodynamic models for the complexation of Na⁺ and Sr²⁺ with organic chelators. In this paper, the development of an aqueous thermodynamic model describing the effects of ionic strength, carbonate concentration, and temperature on the complexation of Sr²⁺ by HEDTA under basic conditions is presented. The thermodynamic model describing the Na⁺ interactions with the HEDTA^3–chelate relies solely on the use of Pitzer ion-interaction parameters. The exclusive use of Pitzer ion-interaction parameters differs significantly from our previous model for EDTA, which required the introduction of a NaEDTA^3– ion pair. Estimation of the Pitzer ion-interaction parameters for HEDTA^3– and SrHEDTA^– with Na⁺ allows the extrapolation of a standard-state equilibrium constant for the SrHEDTA^– species, which is one order of magnitude greater than the 0.1 M reference state value available in the literature. The overall model is developed from data available in the literature on apparent equilibrium constants for HEDTA protonation, the solubility of salts in concentrated HEDTA solutions, and from new data on the solubility of SrCO₃(c) obtained as part of this study. The predictions of the final thermodynamic model for the Na-Sr-OH-CO₃-NO₃-HEDTA-H₂O system are tested by application to chemical systems containing competing metal ions (i.e., Ca²⁺).     

Responsive Polyelectrolyte Multilayers Assembled at High Ionic Strength with an Unusual Collapse at Low Ionic Strength

Responsive polyelectrolyte multilayers (PEMs) of poly(diallyl dimethyl ammonium chloride) (PDADMAC) and poly(styrene sodium sulfonate) (PSS) with thicknesses between 350 and 400 nm for 11 deposited polyelectrolyte layers were fabricated assembling the polyelectrolytes at 3 M NaCl. When the 3 M NaCl bulk solution is replaced by water, the PEMs release water, approximately a 46% of the total mass, and experience a thickness reduction of more than 200 nm. Changes in thickness and water content are fully reversible. The film recovers its original thickness and water content when it is exposed again to a 3 M NaCl solution. A responsive polymer film is achieved with the capability of swelling at high ionic strength and collapsing in water with variations in thickness of hundred of nanometers.     

核苷酸与β-环糊精及硼酸盐的络合作用在高效毛细管电泳分离核苷酸中的应用

核苷酸和β-环糊精(β-CD)及硼酸盐之间存在络合作用，可应用于核苷酸的高效毛细管电泳分离，在10mmol/L β-CD和20mmol/L硼酸盐存在时，实现了8种单磷酸核苷酸的分离测定；讨论了pH值、β-CD浓度、硼酸盐浓度及分离电压对分离和络合作用的影响。     

Development of Accurate Chemical Equilibrium Models for Oxalate Species to High Ionic Strength in the System: Na—Ba—Ca—Mn—Sr—Cl—NO<Subscript>3</Subscript>—PO<Subscript>4</Subscript>—SO<Subscript>4</Subscript>—H<Subscript>2</Subscript>O at 25 °C

The development of an accurate aqueous thermodynamic model is described for oxalate species in the Na—Ba—Ca—Mn—Sr—Cl—NO₃—PO₄—SO₄—H₂O system at 25 °C. The model is valid to high ionic strength (as high as 10 mol·kg⁻¹) and from very acid (10 mol·kg⁻¹ H₂SO₄) to neutral and basic conditions. The model is based upon the equations of Pitzer and co-workers. The necessary ion-interaction parameters are determined by comparison with experimental data taken from the literature or determined in this study. The proposed aqueous activity and solubility model is valid for a range of applications from interpretation of studies on mineral dissolution at circumneutral pH to the dissolution of high-level waste tank sludges under acidic conditions.     

室温离子液体中乙酸钠和氯苄催化合成乙酸苄酯

在多种1,3-二烷基咪唑和烷基吡啶室温离子液体中考察了较温和条件下乙酸 钠和氯化苄作用合成乙酸苄酯反应。在反应温度下（60 ℃）,熔融的三水合乙酸 钠与离子液体相混溶,氯苄同乙酸钠作用得到乙苄酯,它与四氟硼酸1-乙基-3-甲 基咪唑离子液体不溶而分层。反应结束后产物乙酸苄酯可直接倾析得到,乙酸苄酯 产率达到90%,纯度超过99%。此离子液体催化体系简化了产物分离,离子液体可以 重复使用。     

Thermodynamic Studies on the Complexation of Cobalt(II) with Dopamine in a Cosolvent System

Equilibrium constants for formation of a cobalt(II) complex with the bidentate ligand dopamine have been studied with spectrophotometric methods in water + ethanol cosolvent systems at 15, 25, and 35 (±0.1) °C and an ionic strength of 0.2 mol⋅dm⁻³. The ionic strength was maintained using sodium chloride and a phosphate buffer. The stability constants of the complex and the resulting Gibbs energy changes are obtained. The results are discussed in terms of the effect of solvent on protonation and complexation.     

氯化介质中PbS固体表面的氯络合-溶解行为

对硫化铅固体表面的氯络合-溶解行为进行了研究。溶液化学计算考察颗粒表面固体反应产物(PbCl2)的生成与溶解情况表明,饱和氯化钠介质中PbCl2主要以[PbCl4]2-络合物的形式存在于溶液中,氯离子组分总浓度[Cl-]T=0·918mol/L时,PbCl2能较好地呈固态晶体析出,[Cl-]T>0·918mol/L时PbCl2晶粒因氯络合作用而溶解。通过Tafel实验进一步分析了PbS固体表面的腐蚀溶解行为,结果显示,当CFe3 ≤6×10-4mol/L时,腐蚀速度对Fe3 存在很强的依数性,浓度增加,腐蚀速度快速提高;CFe3 >6×10-4mol/L,有钝化现象发生。NaCl的加入,溶液相Cl-活度增加,PbCl2快速溶解,腐蚀反应加快。     

离子液体/乙烯-醋酸乙烯共聚物复合材料的制备与性能

分别将离子液体三正丁基甲铵(双三氟甲磺酰)亚胺盐([TBMA][NTf₂])和1-乙基-3-甲基咪唑四氟硼酸盐([EMIM][BF₄])与乙烯-醋酸乙烯共聚物弹性体(EVM)熔融共混制备复合材料,研究了离子液体与EVM的相容性及抗静电性能。 样品宏观透明性和SEM测试结果显示,[TBMA][NTf₂]与EVM具有较好的相容性,相应的EVM/[TBMA][NTf₂]复合材料的抗静电效果更好;热重分析(TGA)结果表明,[TBMA][NTf₂]促进EVM热解,而[EMIM][BF₄]对EVM的热稳定影响较小。 室温下在EVM中填加[TBMA][NTf₂]的共混物表现出较好的柔性,当[TBMA][NTf₂]质量分数为20%时,EVM/[TBMA][NTf₂]复合材料的模量为0.58 MPa,断裂伸长率可达到2997%。     

Ionic Strength Dependence of Formation Constants and Complexation of Glutamine with Dioxovanadium(V)

The dependence of L-glutamine protonation and its complexation with dioxovanadium(V) on ionic strength (I) is reported in sodium perchlorate solution as a background salt. The measurements have been performed at 25 ± 0.1°C and various ionic strengths in the range 0.1 to 1.0 mol/l, using a combination of potentiometric and spectrophotometric techniques. The overall analysis of the present and the previous data dealing with the determination of stability constants at different ionic strengths allowed us to obtain a general equation, by which a formation constant determined at a fixed ionic strength can be calculated, with a good approximation, at another ionic strength, if 0.1 I 1.0 mol/l (NaClO₄).     

高离子强度下可溶盐浮选机理

基于表面化学性质,泡沫浮选已成为一种分离非均质固体混合物的有效手段,并被广泛应用于原矿分离及其他化学工业。在浮选过程中,捕收剂往往对矿物表面进行选择性吸附以调控矿物表面的亲疏水性。目前,大部分可溶盐的生产,尤其是钾盐工业生产,主要采用泡沫浮选的方法。尽管可溶盐实际浮选体系很复杂,但主要包含矿物晶体、捕收剂、气泡和高离子强度的饱和盐溶液四种组分。实际上,浮选能否完成是这四种组分相互作用的结果。因此,大量的可溶盐浮选机理研究工作都集中于浮选体系中各组分之间的相互作用。本文对高离子强度下可溶盐浮选机理的主要研究成果进行了综述,重点介绍了可溶盐的溶液化学性质,捕收剂在饱和盐溶液中的胶体性质,捕收剂在矿物晶体表面的选择性吸附机制和吸附行为,矿物晶体/饱和盐溶液界面性质以及气泡在浮选过程中作用机理,并对高离子强度下可溶盐浮选机理研究的发展趋势进行了展望。     

中空纤维膜液相微萃取-高效液相色谱法测定醋酸氯己定痔疮栓中的醋酸氯己定

建立了中空纤维膜液相微萃取-高效液相色谱（HPLC）测定醋酸氯己定痔疮栓中醋酸氯己定含量的方法。将样品用醋酸水溶液萃取5次,配成样品溶液,然后用装有正辛醇的中空纤维膜进行液相微萃取,萃取液用高效液相色谱测定。醋酸氯己定的质量浓度为0.5 ～ 16 mg/L时与其峰面积呈良好的线性关系,加样回收率大于98.0%,相对标准偏差低于4.0%。该方法样品处理简单、快速,灵敏度与不经过液相微萃取的HPLC方法相比提高了约24倍,醋酸氯己定痔疮栓中的其他物质对测定无干扰。     

Potentiometric Study of Aluminium-Fluoride Complexation Equilibria and Definition of the Thermodynamic Model

Complexation constants of the Al³⁺/F⁻ system were determined at different ionic strengths in a NaClO₄ (1.0, 2.0 and 3.0 mol⋅dm⁻³) ionic medium by means of a potentiometry using two electrode systems: an ion fluoride selective electrode as well as a glass electrode. All the experimentation was performed at 25 °C. The main species in the complexation equilibria were determined as AlF²⁺, AlF₂⁺, AlF₃⁰, AlF₄⁻, AlF₅²⁻ and AlF₆³⁻. The differences found in the complexation constants for the ionic strength considered were explained by the different behavior of the interaction parameters for the AlF _n ³⁻ⁿ species. These parameters were calculated using the Modified Bromley’s Methodology (MBM). The corresponding thermodynamic quantities were also determined. From all the results obtained, it can be concluded that pH, fluoride concentration and ionic strength influenced the distribution of the fluoride-aluminium complexes.     

Voltammetry and EQCM Investigation of Glutathione Monolayer and Its Complexation with Cu2+

The glutathione (GSH) self‐assembled monolayer and its compexlation with Cu²⁺ were studied by using voltammetry and EQCM. It was found that the monolayer could rearrange during the redox process of Cu²⁺/Cu⁺. The protonating, or not, of the carboxyl terminates of the adsorpted GSH molecules influence the compexlation interaction significantly for they are the key binding sites. The GSH monolayer had the capacity to accumulate Cu²⁺ and the monolayer modified gold electrode was employed to detect the low levels of Cu²⁺ with a limit of 1.0×10^?10 mol L^?1.     

由苯经水促高选择性阳极乙酰氧化法一步合成乙酸苯酯

One-step anodic acetoxylation of benzene to phenyl acetate was studied in acetic acid-water solution using a one-compartment electrochemical cell in galvanostatic mode. Compared to the anhydrous system, the addition of water improved the current efficiency for the electro-synthesis of phenyl acetate. The maximum efficiency reached 4.8% with the selectivity of 96% to phenyl acetate when the electrolysis was carried out under the optimal conditions. The investigation also indicated that the concentration of phenyl acetate increased linearly in 12 h and reached 1.07 g/L with the selectivity of 95%. Cyclic voltammetry experiments showed that the adsorption of benzene at Pt anode enhanced by the addition of water was critical to the formation of phenyl acetate. An activated benzene mechanism was proposed for the anodic acytoxylation, and the analysis of gas products demonstrated that Kolbe reaction was the main side reaction.     

Molecular Interactions and Thermodynamic Aspects of the Complexation Reaction between Gentian Violet and Several Cyclodextrins

The complexation process between gentian violet (CV+) and four different cyclodextrins (-, -, -, and HP--CDs) has been investigated under different reaction conditions (pH, solvent, and temperature) by electronic absorption and 1H NMR (NOE and NOESY) spectroscopies. All the binding constants were determined by the direct spectroscopic method. The H and S complexation values have been evaluated and discussed according to the diverse factors that affect the chemical interactions in these systems. A simple association takes place between the secondary hydroxyl or the hydroxypropyl groups of and HP--cycloamyloses, respectively, with the amine group of the gentian violet, while the binding between CV+ and - or -CDs corresponds to a real inclusion. Also, a CV22+ dimmeric species within the -CD cavity was detected in aqueous solution, while two molecules of -CD react with one molecule of gentian violet in DMSO at 294 K. In all the reaction media the -CD forms 1 : 1 complexes, but in the buffered aqueous solution at pH 7.5 the inclusion is deeper than in the other solvents. It is important to point out that the solvophobic effect is the most important binding factor in the complexation of the CV+ with the - and HP--CDs, while the complexes with -, and -cyclodextrins are mainly stabilized by van der Waals interactions between the guest and the host cavity. In all cases, the inclusion orientation is probably determined by the ion-dipole interactions between gentian violet and the solvent.     

Thermodynamic modeling of high salinary phosphate solutions II. Ternary and higher systems

A comprehensive set of ternary interaction Pitzer parameters for solutions of the system Na–K–Cl–SO₄–PO₄–HPO₄–H₂PO₄ was calculated from water activity and solubility data acquired from an extensive literature review and water activity data obtained from isopiestic experiments. This work is a continuation of part I, wherein results concerning binary phosphate systems are presented.