Solid‐Liquid Equilibria in the Quinary Na+, K+//Cl−, SO2−4, B4O2−7‐H2O System at 298 K

The solid‐liquid equilibria in the quinary system Na⁺, K⁺//Cl^?, SO^2?₄, B₄O^2?₇‐H₂O at 298 K had been studied experimentally using the method of isothermal solution saturation. Solubilities and densities of the solution of the quinary system were measured experimentally. Based on the experimental data, the dry‐salt phase diagram and water content diagram of the quinary system were constructed, respectively. In the equilibrium diagram of the quinary system Na⁺, K⁺//Cl^?, SO^2?₄, B₄O^2?₇‐H₂O at 298 K, there are five invariant points F1, F2, F3, F4 and F5; eleven univariant curves E1F1, E2F2, E3F3, E4F5, E5F2, E6F4, E7F5, F1F4, F2F4 F1F3 and F3F5, and seven fields of crystallization saturated with Na₂B₄O₇ corresponding to Na₂SO₄, Na₂SO₄·10H₂O, Na₂SO₄·3K₂SO₄ (Gla), K₂SO₄, K₂B₄O₇·4H₂O, NaCl and KCl. The experimental results show that Na₂SO₄·3K₂SO₄ (Gla), K₂SO₄ and K₂B₄O₇·4H₂O have bigger crystallization fields than other salts in the quinary system Na⁺, K⁺//Cl^?, SO^2?₄, B₄O^2?₇‐H₂O at 298 K.     

Preparation,swelling behaviors and application of polyacrylamide/attapulgite superabsorbent composites

A series of superabsorbent composites, polyacrylamide/attapulgite (PAMA), were prepared from acrylamide (AM) and attapulgite micropowder in aqueous solution, using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator and then saponified with sodium hydroxide solution. This paper focuses on swelling behaviors of the PAMA superabsorbent composites in various saline solutions. The results indicate that saline solutions can weaken the swelling abilities of the PAMA compsites greatly. Water absorbency of the PAMA composites with 20 and 40 wt% attapulgite in aqueous chloride salt solutions has the following order: Li⁺ = Na⁺ = K⁺, Mg²⁺ > Ca²⁺ = Ba²⁺ all through the range of concentration investigated. However, swelling properties of the composites are complicated in CuCl_2(aq), AlCl_3(aq) and FeCl_3(aq) solutions and are related to saline solutions concentration. The deswelling behavior of PAMA composites is more obvious in univalent chloride salt solutions than in divalent and trivalent ones. The influence of kind and valence of anions on swelling ability of the composites is limited and almost the same. Moreover, reswelling capability, practical water retention ability in sand soil of the composites and the effect of pH on water absorbency of the PAMA composites were investigated. The PAMA composite shows good water retention and reswelling ability in sand soil, and may be used as a recyclable water‐managing material for the renewal of arid and desert environment. Copyright © 2006 John Wiley & Sons, Ltd.     

The Role of Alkali Cation Intercalates on the Electrochemical Characteristics of Nb2CTX MXene for Energy Storage

The intercalation of cations into layered-structure electrode materials has long been studied in depth for energy storage applications. In particular, Li⁺-, Na⁺-, and K⁺-based cation transport in energy storage devices such as batteries and electrochemical capacitors is closely related to the capacitance behavior. We have exploited different sizes of cations from aqueous salt electrolytes intercalating into a layered Nb₂CT_x electrode in a supercapacitor for the first time. As a result, we have demonstrated that capacitive performance was dependent on cation intercalation behavior. The interlayer spacing expansion of the electrode material can be observed in Li₂SO₄, Na₂SO₄, and K₂SO₄ electrolytes with d-spacing. Additionally, our results showed that the Nb₂CT_x electrode exhibited higher electrochemical performance in the presence of Li₂SO₄ than in that of Na₂SO₄ and K₂SO₄. This is partly because the smaller-sized Li⁺ transports quickly and intercalates between the layers of Nb₂CT_x easily. Poor ion transport in the Na₂SO₄ electrolyte limited the electrode capacitance and presented the lowest electrochemical performance, although the cation radius follows Li⁺>Na⁺>K⁺. Our experimental studies provide direct evidence for the intercalation mechanism of Li⁺, Na⁺, and K⁺ on the 2D layered Nb₂CT_x electrode, which provides a new path for exploring the relationship between intercalated cations and other MXene electrodes.     

Speciation and Structural Properties of Hydrothermal Solutions of Sodium and Potassium Sulfate Studied by Molecular Dynamics Simulations

Aqueous solutions of salts at elevated pressures and temperatures play a key role in geochemical processes and in applications of supercritical water in waste and biomass treatment, for which salt management is crucial for performance. A major question in predicting salt behavior in such processes is how different salts affect the phase equilibria. Herein, molecular dynamics (MD) simulations are used to investigate molecular‐scale structures of solutions of sodium and/or potassium sulfate, which show contrasting macroscopic behavior. Solutions of Na?SO₄ exhibit a tendency towards forming large ionic clusters with increasing temperature, whereas solutions of K?SO₄ show significantly less clustering under equivalent conditions. In mixed systems (Na_xK_2?xSO₄), cluster formation is dramatically reduced with decreasing Na/(K+Na) ratio; this indicates a structure‐breaking role of K. MD results allow these phenomena to be related to the characteristics of electrostatic interactions between K⁺ and SO₄^2?, compared with the analogous Na⁺?SO₄^2? interactions. The results suggest a mechanism underlying the experimentally observed increasing solubility in ternary mixtures of solutions of Na?K?SO₄. Specifically, the propensity of sodium to associate with sulfate, versus that of potassium to break up the sodium–sulfate clusters, may affect the contrasting behavior of these salts. Thus, mutual salting‐in in ternary hydrothermal solutions of Na?K?SO₄ reflects the opposing, but complementary, natures of Na?SO₄ versus K?SO₄ interactions. The results also provide clues towards the reported liquid immiscibility in this ternary system.     

Solubility in K+-Na+-Mg 4 2− aqueous solution at T = 298.15 K

In the salt solubility predictions for K⁺-Na⁺-Mg ₄ ^2? aqueous solution the treatment of thermodynamic data of three-component systems at T = 298.15 K involved the application of the Extended Pitzer’s ion-interaction model for the pure and mixed electrolyte solutions and criteria of phase equilibrium. Osmotic coefficients data of three-component systems were revised according to recently published parameters of the solutions NaCl(aq) and KCl(aq) that served as reference standards in isopiestic measurements. Parameters of the extended ion-interaction model of K₂SO₄(aq) are determined by treatment of experimental and predicted values of osmotic coefficient in supersaturated region obtained by the Zdanovskii-Stokes-Robinson rule. Results of salt solubility prediction were compared to experimental solubility data from literature. The agreement between calculated and experimental solubility data in the systems K₂SO₄ + MgSO₄ + H₂O, Na₂SO₄ + MgSO₄ + H₂O, and Na₂SO₄ + K₂SO₄ + H₂O at T = 298.15 K, was excellent.     

The Oxidation of Luminol an Experiment to Maximize the Efficiency of Chemiluminescence from Luminol

In this work, seven inorganic salts, KCl, Na₂SO₄, MgSO₄-7H₂O, ZnCl₂, Na₂CrO₄, CuSO₄-5H₂O, and K₃[Fe(CN)₆], were used as catalysts to induce chemiluminescent luminol oxidation in alkaline aqueous media. It was observed that simple salts containing either Mg²⁺, Zn²⁺, Na⁺ and K⁺ cations or SO₄^2– and Cl^– anions, are not active as catalysts. On the other hand, the relative order of activity detected for the active chemiluminescent salts containing Fe(III), Cu(II) and Cr(VI) cations is K₃[Fe(CN)₆] < CuSO₄-5H₂O < Na₂CrO₄. The intensity of the emitted light agrees with the standard reduction potentials of the corresponding redox couple and with the presence of paramagnetic species in the aqueous solutions. The inhibition effect of mannitol was also studied.     

二（2-乙基己基）二硫代磷酸溶剂萃取铊的热动力学

在Tl₂SO₄＋Na₂SO₄＋二（2-乙基己基）二硫代磷酸＋n-C₈H₁₈＋水体系中， 测定了0.1－2.0 mol•kg^－1离子强度范围内Tl^＋ 的平衡摩尔浓度。水相中电解质Na₂SO₄ 控制溶液离子强度， 有机相中萃取剂取278.15 K至303.15 K范围内的恒定摩尔浓度。通过外推法和多项式近似得到了不同温度下的标准萃取常数K⁰，计算了萃取过程的热动力学量。     

Characterization of Silicate Complexes in Aqueous Sodium Sulfate Solutions by FAB-MS

When the sodium ion (Na⁺) concentration is increased above 0.5 mol-dm⁻³ (M), the concentrations of dissolved silica in aqueous sodium chloride (NaCl) and sodium nitrate (NaNO₃) solutions decrease because of the salting out effect. On the other hand, the concentration of the dissolved silica in aqueous sodium sulfate (Na₂SO₄) solutions increases monotonously as the concentration of Na⁺ is increased above 0.5 M. The purpose of this study is to determine the reasons why the salting-out effect is not observed in Na₂SO₄ solutions. FAB-MS (Fast Atom Bombardment Mass Spectrometry) was used to sample directly the silica species dissolved in aqueous Na₂SO₄, NaCl, and NaNO₃ solutions. In the FAB-MS spectra of these solutions, the peak intensity ratios of the linear tetramer to the cyclic tetramer largely increased for Na⁺ concentrations between (0.1 and 1) M. This shows that some characteristics of the Na₂SO₄ solutions are similar to those of the NaCl and NaNO₃ solutions. In Na₂SO₄ solutions, however, when the concentration of Na⁺ is higher than 1 M, the peak intensity of the dimer is much higher than those of the other silicate complexes. In Na₂SO₄ solutions, the SO₄²⁻ ion undergoes partial hydrolysis to form HSO⁻₄ and OH⁻ is produced. In particular, in the range where the concentration of SO₄²⁻ is high, the pH of the solution increases slightly. This higher pH yields more dimers from the hydrolysis of silicate complexes. This increase in dimer production agrees with the observation that silica dissolves in sodium hydroxide (NaOH) solutions mainly as a dimer when the concentration of NaOH is less than 0.1 M. In Na₂SO₄ solutions at high concentrations, a salting-out effect is not observed for silica. This is due to the increase in the concentration of OH⁻, which accelerates the hydrolysis of silica and results in dimer formation.     

Enthalpy changes of salting processes of hen-egg white lysozyme in various electrolyte solutions

The enthalpy changes of salting process of hen-egg white lysozyme in buffer acetate solutions (pH=4.25) as a function of concentration of following electrolytes: LiCl, KCl, K₂SO₄, Li₂ SO₄ and (NH₄)₂SO₄ are determined. Obtained data according to McMillan and Mayer’s approach, has been analyzed in the terms of the enthalpic pairwise interaction coefficients: lysozyme – lysozyme h_xx, and lysozyme – salt h_xy. The ability of cations to precipitate lysozyme solution in relation to the concentration of cations can be seen from the series as follows: Li⁺> Na⁺>K⁺>NH₄+⁺     

Die Polytherme des Quinären Systems Na+, K+, Mg2+/Cl−, SO//H2O im Bereich von +25° bis −10°C

Polythermal Curves of the Quinary System Na⁺, K⁺, Mg²⁺/Cl^?, SO//H₂O in Range between +25°C and ?10°C Proceeding from the 0°C, ?5°C and ?10°C isothermal curves of the quinary system Na⁺, K⁺, Mg²⁺/C1^?, SO//H₂O with saturation at NaCl, KCl, and carnallite, respectively, the polythermal curve is represented between 25°C and ?10°C. Within the new defined range of the polythermal curve the invariant five-salt-paragenesis NaCI, KCI, Glauber's salt (Na₂SO₄ · 10 H₂O), bitter salt (MgSO₄ · 7 H₂O), Schoenite (K₂SO₄ · MgSO₄ · 6 H₂O) can be found at ?7,2°C. It represents also the lowest temperature of formation of Schoenite in this system. It was necessary, moreover, to reconsider further univariant and invariant equilibrium solutions in the range between 25° and 0°C.     

Drawing Out the Structural Information About the First Hydration Layer of the Isolated Cl− Anion Through the FTIR-ATR Difference Spectra

The Fourier transform infrared-attenuated total reflectance (FTIR-ATR) difference spectra of aqueous MgSO₄, Na₂SO₄, NaCl and MgCl₂ solutions against pure water were obtained at various concentrations. The difference spectra of the solutions showed distinct positive bands and negative bands in the O–H stretching region, indicating the influences of salts on structures of hydrogen-bonds between water molecules. Furthermore the difference spectra of MgCl₂ solutions against NaCl solutions and those of MgSO₄ solutions against Na₂SO₄ solutions with the same concentrations of anions (Cl^? or SO ₄ ^2? , respectively) allowed extracting the structural difference of the first hydration layer between Mg²⁺ and Na⁺. Using SO ₄ ^2? as a reference ion, structural information of the first hydration layer of the Cl^? anion was obtained according to the difference spectra of MgCl₂ solutions against MgSO₄ solutions and those of NaCl solutions against Na₂SO₄ solutions containing the same concentrations of cations (Mg²⁺ or Na⁺, respectively). The positive peak at ~3,407 cm^?1 and negative peak at ~3,168 cm^?1 in these spectra indicated that adding Cl^? decreased the strongest hydrogen-bond component and increased the relatively weaker one.     

Kinetics of cerium (IV) oxidation of mandelic acid. Ionic strength and specific cation effects

The kinetics of the redox reaction between mandelic acid (MA) and ceric sulfate have been studied in aqueous sulfuric acid solutions and in H₂SO₄? MClO₄ (M⁺ = H⁺, Li⁺, Na⁺) and H₂SO₄? MHSO₄ (M⁺ = Li⁺, Na⁺, K⁺) mixtures under various experimental conditions of total electrolyte concentration (that is, ionic strength) and temperature. The oxidation reaction has been found to occur via two paths according to the following rate law: rate = k[MA] [Ce(IV)], where k = k₁ + k₂/(1 + a)²[HSO₄^?]² = k₁ + k₂/(1 + 1/a)²[SO₄^2?]², a being a constant. The cations considered exhibit negative specific effects upon the overall oxidation rate following the order H⁺ ? Li⁺ < Na⁺ < K⁺. The observed negative cation effects on the rate constant k₁ are in the order Na⁺ < Li⁺ < H⁺, whereas the order is in reverse for k₂, namely, H⁺ ? Li⁺ < Na⁺. Lithium and hydrogen ions exhibit similar medium effects only when relatively small amounts of electrolytes are replaced. The type of the cation used does not affect significantly the activation parameters.     

The synthesis of novel crown ethers,part ix, 3‐phenyl chromenone‐crown ethers

3‐Phenyl‐ and 3‐(p‐methoxyphenyl)‐7,8‐dihydroxy and ‐6,7‐dihydroxychromenones were prepared from ethyl 3‐oxo‐2‐phenylpropanoate, ethyl 3‐oxo‐2‐(4‐methoxyphenyl)‐propanoate and the trihydroxy benzenes in H₂SO₄. 3‐Aryl‐7,8‐ and 3‐aryl‐6,7‐dihydroxy‐2H‐chromenones reacted with the bis‐dihalides of poly‐glycols in DMF/MeCO₃ to afford 12‐Crown‐4, 15‐Crown‐4 and 18‐Crown‐6‐chromenones. The products were identified with IR, 1H NMR, low and high resolution mass spectroscopy and elemental analysis. Some 1:1 cation association constants, K_b, of the 3‐phenyl chromenone crown ethers with Li⁺, Na⁺, K⁺ and Rb⁺ cations were studied by steady state emission fluorescence spectroscopy; K_b chromenone‐crown complexes displayed crown ether‐cation binding selectivity rules properly in acetonitrile.     

电解质水溶液结构研究进展及前景*

叙述盐湖中主要离子Li⁺ 、Na⁺ 、K⁺ 、Mg²⁺ 、Ca²⁺ 、Cl^- 、SO^2-₄ 、NO^-₃ 的水溶液和纯水的结构, 简单介绍了主要的研究方法, 分析讨论了溶液结构研究的现状和发展前景。     

Separation of 97Ru from niobium target using PEG based aqueous biphasic systems

Separation of no-carrier-added (NCA) ⁹⁷Ru from bulk niobium target has been carried out for the first time using green analytical technique, aqueous biphasic system. 50 % (w/v) polyethylene glycol (PEG)-4000, against 2 M solutions of various salts such as Na-citrate, Na-tartarate, Na-malonate, Na₂CO₃, NaHSO₃, Na₂SO₄, Na₂S₂O₃ K₂HPO₄, K₃PO₄, K₂CO₃ and 4 M KOH were employed at room temperature for the extraction of NCA ⁹⁷Ru from bulk niobium. Influence of molecular weight of PEG rich phase as well as pH of some salt rich phase (e.g., Na-tartarate) on the extraction behaviour of NCA ⁹⁷Ru into PEG rich phase was also observed. In the presence of sodium-tartarate salt solution, when volume of PEG-4000: Na-tartarate was 3:1, 91 % of NCA ⁹⁷Ru was extracted into the PEG rich phase without any contamination of niobium target. Dialysis of PEG rich phase containing NCA ⁹⁷Ru was carried out against deionised water to obtained pure NCA ⁹⁷Ru.     

Study on electrochemical performance of activated carbon in aqueous Li2SO4, Na2SO4 and K2SO4 electrolytes

The electrochemical performances of activated carbon (AC) in 0.5 mol/l Li₂SO₄, Na₂SO₄ and K₂SO₄ aqueous electrolytes were investigated. The cyclic voltammetric results at different scan rates show that the rate behaviors of AC in the three electrolytes improve in the order of Li₂SO₄ < Na₂SO₄ < K₂SO₄. This improvement can be mainly ascribed to the following two reasons: (1) the decreasing equivalent series resistance in the order of Li₂SO₄ > Na₂SO₄ > K₂SO₄, which is the main factor influencing the maximum output power, and (2) the increasing migration speed of hydrated ions in the bulk electrolyte and in the inner pores of AC electrode in the order of Li⁺ < Na⁺ < K⁺. Their cycling behaviors do not show any differences in capacitive fading. The above results provide valuable information to explore new hybrid supercapacitors.     

Ion-exchange selectivity of a sulfonic cation exchanger based on immobilized cis-tetraphenylcalix[4]resorcinolarene

The ion-exchange equilibrium of protons in SO₃H groups of a sulfonic cation exchanger based on immobilized cis-tetraphenylcalix[4]resorcinolarene with cations of Li⁺, Na⁺, Ag⁺, Cu²⁺, In³⁺, and protonated 1,3,5,7-tetraazaadamantane in aqueous solutions of electrolytes at 293 K was studied. The corrected coefficients of the cation exchange selectivity were calculated.     

Thermodynamic representation of the NaCl + Na2SO4 + H2O system with electrolyte NRTL model

A comprehensive thermodynamic model based on the electrolyte NRTL (eNRTL) activity coefficient equation is developed for the NaCl + H₂O binary, the Na₂SO₄ + H₂O binary and the NaCl + Na₂SO₄ + H₂O ternary. The NRTL binary parameters for pairs H₂O-(Na⁺, Cl⁻) and H₂O-(Na⁺, SO₄²⁻), and the aqueous phase infinite dilution heat capacity parameters for ions Cl⁻ and SO₄²⁻ are regressed from fitting experimental data on mean ionic activity coefficient, heat capacity, liquid enthalpy and dissolution enthalpy for the NaCl + H₂O binary and the Na₂SO₄ + H₂O binary with electrolyte concentrations up to saturation and temperature up to 473.15 K. The Gibbs energy of formation, enthalpy of formation and heat capacity parameters for solids NaCl_(s), NaCl·2H₂O_(s), Na₂SO_4(s) and Na₂SO₄·10H₂O_(s) are obtained by fitting experimental data on solubilities of NaCl and Na₂SO₄ in water. The NRTL binary parameters for the (Na⁺, Cl⁻)-(Na⁺, SO₄²⁻) pair are regressed from fitting experimental data on dissolution enthalpies and solubilities for the NaCl + Na₂SO₄ + H₂O ternary.     

Water transference through nickel hydroxide precipitate membrane

The transference of water that results from ion migration through the nickel hydroxide precipitate membrane was studied in chloride, perchlorate, nitrate, and sulphate solutions to estimate the transference number of water and the co-ion transport. In the systems of univalent anions, the moles of water transported per mole of electrons in 0.1 N solutions is almost identical to the hydration number of each anion. This water flow decreases gradually as the concentration of external solution increases, because of increase in the co-ion (cation) transport with increasing concentration of the solution. In the system of sulphate solutions the co-ion transport is remarkable, the transport number of Na⁺ ions being 0.03 in 0.01 N, 0.27 in 0.10 N, and 0.50 in 0.5 N Na₂SO₄ solution. This large co-ion transport in Na₂SO₄ solution is attributed to the partical replacement of hydroxyl groups on the membrane by SO^2?₄ ions, which then acts as a negative fixed charge. The order of the selectivity for co-ion transport is K⁺ > Na⁺ > Li⁺ > Ni²⁺ ? Mg²⁺ in sulphate solutions and also in chloride solutions, although the transport number of the cations is much smaller in chloride solution than in sulphate solution.