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.     

Measurements of the Solid–Liquid Equilibria in the Quaternary System NaCl–NaBr–Na2SO4–H2O at 323 K

Phase equilibria of the quaternary NaCl–NaBr–Na₂SO₄–H₂O system at 323 K were studied by the isothermal dissolution equilibrium method. The solubilities of salts and densities of saturated solutions were determined. Solid solutions [Na(Cl, Br)] were found in the experiments. The phase diagram of the quaternary system has no invariant point, but has one univariant curve at the boundary of Na(Cl, Br) and Na₂SO₄ crystallization fields. The experimental results show that an increase of the NaBr concentration is accompanied by an obvious increase of the solution density and the decrease of the solubilities of NaCl and Na₂SO₄.     

Biodegradation of Mixed Phenolic Compounds Under High Salt Conditions and Salinity Fluctuations by <Emphasis Type="Italic">Arthrobacter</Emphasis> sp. W1

High salt concentration and salinity fluctuations in wastewater challenge the efficiency of microbial strains used for cleanup of pollutants. In this study, it was investigated that the new isolated Arthrobacter sp. W1 degraded mixed phenolic compounds under complex salt conditions. The results showed that Arthrobacter sp. W1 was able to utilize various phenolic compounds as carbon source under high salt conditions. It can degrade phenol and p-cresol mixture at 10% NaCl, although rates of degradation and cell growth were lower compared to 5% NaCl. The presence of trace p-cresol significantly inhibited phenol biodegradation. When salinity fluctuations were between 1% and 10% NaCl, strain W1 was able to degrade substrates and survived. It was also suggested that the presence of salts (i.e., NaCl, KCl, Na₂SO₄, and K₂SO₄) had almost no effects on the microbial growth and biodegradation process. Therefore, Arthrobacter sp. W1 would be a promising candidate for bioremediation of phenolic compounds under complex salt conditions.     

Fabrication of the polyethersulfone/functionalized mesoporous carbon nanocomposite nanofiltration membrane for dyes and heavy metal ions removal: Experimental and quantum mechanical simulation method

The presence of industrial pollutants, especially salts, heavy metals ions, and dyes in water and wastewater is considered a serious environmental issue. To eliminate these pollutants, a high-performing nanofiltration (NF) membrane was prepared by blending the functionalized mesoporous carbon CMK-5 (F-CMK-5) nanofiller. This membrane was synthesized by introducing the active groups of sulfonyl and amide to the surface of mesoporous carbon CMK-5 through covalent functionalization. Characterizations were conducted to study the membranes' physical properties and separation performance in terms of antifouling properties and rejection of salts, heavy metal ions, and dyes. The interactions between the active sites of the nanocomposite membrane and the studied solutes, including dyes and heavy metal ions in aqueous solutions, were studied by the density functional based tight binding method and structural optimization was carried out. Insertion of the F-CMK-5 nanofiller was eventuated in a remarkable increase in surface hydrophilicity, pure water flux, and antifouling properties. For all membranes, the lowest and the highest salt rejection was obtained for NaCl and Na₂SO₄, respectively, exhibiting the characteristics of NF membranes. Moreover, M_0.3 with 0.3 wt% nanofiller showed the highest rejection for heavy metal ions (Fe²⁺ = 99.9%, Zn²⁺ = 99.9%, Cu²⁺ = 99.7%, and Pb²⁺ = 99.2%) and dyes (RB5 = 99.21, DR16 = 98.87, and MB = 98.12%), as well as high separation performance for filtration of multipollutant solutions. The reusability and 144 h uninterrupted filtration experiments for M_0.3 confirmed the stability of the membrane. The findings suggest that the PES/F-CMK-5 nanocomposite NF membrane is a promising candidate for water and wastewater treatment.     

Activation and Stabilization of Olive Recombinant 13-Hydroperoxide Lyase Using Selected Additives

The stabilization of olive recombinant hydroperoxide lyases (rHPLs) was investigated using selected chemical additives. Two rHPLs were studied: HPL full-length and HPL with its chloroplast transit peptide deleted (matured HPL). Both olive rHPLs are relatively stable at 4 °C, and enzyme activity can be preserved (about 100% of the rHPL activities are maintained) during 5 weeks of storage at ?20 or at ?80 °C in the presence of glycerol (10%, v/v). Among the additives used in this study, glycine (2.5% w/v), NaCl (0.5 M), and Na₂SO₄ (0.25 M) provided the highest activation of HPL full-length activity, while the best matured HPL activity was obtained with Na₂SO₄ (0.25 M) and NaCl (1 M). Although the inactivation rate constants (k) showed that these additives inactivate both rHPLs, their use is still relevant as they strongly increase HPL activity. Results of C6-aldehyde production assays also showed that glycine, NaCl, and Na₂SO₄ are appropriate additives and that NaCl appears to be the best additive, at least for hexanal production.     

Interaction Between Two Similar Plane Parallel Double Layers for (NH4)2Fe(SO4)2 or (NH4)2Cu(SO4)2 Type Complex Salt Electrolytes at Positive Surface Potential

Interaction energies between two similar plane parallel double layers for (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ type complex salt electrolytes at positive surface potential were expanded in a power series and accurate numeral results were given for 0.1 ≤ y _e  < y ₀ ≤ 20. The general expressions were given for the interaction energies of A _ν +B _ν′ +C_ν? type complex salt electrolytes at y > 0. The interaction energies for simple salts NaCl, CaCl₂, Na₂SO₄, FeCl₃, Na₃PO₄, Mg₃(PO₄)₂, Al₂(SO₄)₃, and complex salts (NH₄)₂Fe(SO₄)₂ or (NH₄)₂Cu(SO₄)₂ at y ₀ = 1 were compared. There was hardly difference between these simple salts and this complex salt for the interaction energies. The interaction energy for complex salt (NH₄)₂Fe(SO₄)₂ was close to that for simple salt Na₃PO₄.

Supplemental files are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.     

Swelling behaviors of polyelectrolyte hydrogels containing sulfonate groups

Series of maleate monoester and diester monomers based on poly(ethylene glycol) monomethyl ether (MPEG) were copolymerized using the ionizable 2‐acrylamido‐2–methyl propane sulfonic acid (AMPS) via different dose rate of electron‐beam irradiation (40–150 kGy). The crosslinking of the copolymers were carried out in aqueous acidic solutions at pH 1 or in the presence of 1% N,N‐methylene bisacrylamide (MBA) as crosslinking agent. The final equilibrium water content and swelling capacities for the prepared hydrogels were determined in aqueous solutions at pH 1, 6.8, and 12 and in aqueous salt solutions at 298 K. Swelling equilibria for prepared hydrogels were determined in different molar salt solutions of NaCl, KCl, CaCl₂, Na₂SO₄, K₂SO₄, and CaSO₄. The swelling ratios of gels in pure water and in the salt solutions were found to depend on the counterion species in the increasing sequence of Ca²⁺, Na⁺ and K⁺. Copyright © 2002 John Wiley & Sons, Ltd.     

Bulk properties and hydration numbers of components of water–salt,water–urea,and water–urea–salt systems

With an increase in the concentration of additives, the hydration numbers of compounds decrease. Thus, in a saturated 54.6% solution, urea loses approximately 3/4 of the initial amount of water, forming an aquacomplex of the composition (NH₂)₂CO?H₂O. In a supersaturated 44% solution, the sodium chloride aquacomplex is dehydrated by 2/3, and in a supersaturated 67% solution, sodium sulfate is dehydrated by 5/6. The density of these solutions is 1.354÷1.360 g/cm³ (44% NaCl) and 1.800÷1.849 g/cm³ (67% Na₂SO₄). In a saturated urea solution, NaNO₃, NaCl, and Na₂SO₄ complexes lose 53÷55% of hydration water. It is shown that the interactions in the binary water–urea system somewhat increase the hydration number of the salts (structural hydration). The hydration water density, a structurally important characteristic, increases in the series of solutions of urea, NaNO₃, NaCl, and Na₂SO₄. In the same series of additives, the excess volume of binary water–urea and water–salt systems becomes more negative.     

A combined method for investigating solubility and determining the composition of equilibrium solid phases saturating eutonic solutions in a NaCl-Na2SO4-Na2CO3-H2O system at 50°C

The composition of equilibrium solid phases NaCl, Na₂SO₄, Na₂CO₃ · 2Na₂SO₄ (berkeyite) and NaCl, Na₂CO₃ · H₂O, Na₂CO₃ · 2Na₂SO₄ (without preparative determination), saturating E₁ and E₂ eutonic solutions respectively, was established via nonvariant area boundary determination in a NaCl-N₂SO₄- Na₂CO₃-H₂O system at 50°C with the use of a combined method.     

Liquid–Liquid Equilibrium of Water + 1-Butanol + Inorganic Salt Systems at 303.15, 313.15 and 323.15 K: Experiments and Correlation

Liquid–liquid equilibria (LLE) and tie-line data of systems containing 1-butanol, water and NaCl, Na₂SO₄, NH₄Cl or (NH₄)₂SO₄ were investigated at 303.15, 313.15 and 323.15 K and atmospheric pressure. The salt decreases mutual solubilities of these two solvents leading to a higher degree of phase separation at equilibrium. The effect is more pronounced at high salt concentration. Temperature in the studied range had a minor effect on LLE behavior of these mixtures. Experimental data were correlated using a modified extended UNIQUAC model. Satisfactory agreement between the calculated and measured mass fractions of the components was achieved.     

Swelling of dextran gel and osmotic pressure of soluble dextran in the presence of salts

The swelling of dextran gels (Sephadex) in salt solutions with a water activity of 0.937, compared with the swelling in pure water, exhibited anion specificity as evidenced by an increased swelling ratio in the following order: Na₂SO₄ < H₂O < NaCl < NaSCN. The swelling ratio showed a good linear correlation with the osmotic pressure of dextran (500 kD) in these solutions. The salt‐concentration difference (imbalance) between the polymer‐solution side of the membrane and the polymer‐free permeate side during the osmotic‐pressure measurements positively correlated with the effect of the salt on the polymer osmotic pressure. These phenomena conform to Hofmeister‐type (or lyotropic) behavior. The diminishing augmentation of dextran osmotic pressure and the change in the salt‐concentration imbalance with rising NaSCN concentration imply a positive preferential interaction and adsorption of the salt onto the polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2740–2750, 2001     

Untersuchungen an Systemen aus Salzen und gemischten Lösungsmitteln. VI. Das Verhalten des reziproken Salzpaares Na2SO4 + 2 KCl ⇌ K2SO4+2 NaCl in Methanol-Wasser-Mischungen

The solubility isotherms of the system Na₂SO₄? K₂SO₄? CH₃OH? H₂O at 25,40 and 55°C and the solubilities in the system of the metathetic salt reaction Na₂SO₄+ + 2KCl ? K₂SO₄ + 2NaCl in methanol-water mixtures at 10 and 25°C have been determined and the nature of the solid phases established. The addition of methanol causes an enlargement of the sulphatic existence fields. A flow sheet for the industrial application of the results is communicated.     

Radiation effects on polymers—XIII. The application of cellulose acetate-g-polyacrylamide membranes in the process of water desalination by reverse osmosis

Using computerized programs, the water flux and salt rejection properties in reverse osmosis of cellulose acetate-g-acrylamide membranes are determined. Comparisons are made with ungrafted commercial cellulose acetate membranes, using 0.1 and 1.0 M sodium chloride, sodium sulphate and ammonium sulphate solutions. The grafted cellulose acetates show improved water flux but reduced NaCl rejection. However, they show promising prospects in bigger ion separation as for Na₂SO₄ and (NH₄)₂SO₄ solutions.     

The application of DTA to hot corrosion studies of chromium and nickel powders and nimonic 80A

DTA has been successfully employed to study the hot corrosion behaviour of chromium and nickel powders and Nimonic 80A alloy samples in the presence of corrodants such as NaCl and Na₂SO₄. The DTA data indicate a large high-temperature exotherm due to oxidation in air; the onset of oxidation occurs at much lower temperatures when additional oxidants are added. The results also show that NaCl attacks chromium much more aggressively than does either Na₂SO₄ or the salt mixture. The reverse has been observed for nickel, i.e. enhanced corrosion in the presence of Na₂SO₄ and the mixtures. Both Cr and Ni are oxidized to their respective oxides, via chloride formation in the presence of NaCl, and via sulphide formation in the presence of Na₂SO₄. Sodium chromate formation was confirmed with chromium in addition to the above compounds in the presence of sodium salts. On the other hand, the DTA results on Nimonic 80A alloy samples indicate that the corrosion attack is negligible as long as the salt is in the solid form, but once the salt is molten it triggers catastrophic corrosion. The mechanism of hot corrosion is discussed.     

Salt Effects on Aqueous Cationic/Anionic Surfactant Two‐Phase Regions

The influence of added salts (KCl, NaF, NaCl, NaBr, Na₂SO₄, Na₃PO₄) on aqueous cetyltrimethylammonium bromide (CTAB)/sodium dodecyl sulfonate (AS) two‐phase regions were studied. For KCl, the concentration dependence of salt effect on aqueous two‐phase regions was investigated. When brine substitutes pure water as a solvent, the positions of aqueous two‐phase regions in the phase diagram change. The results indicate that for aqueous two‐phase systems with excess anionic surfactant (ATPS‐A), the salt effect was mainly dependent on the cationic inorganic counterions, whereas for aqueous two‐phase systems with excess cationic surfactant (ATPS‐C), the salt effect was mainly dependent on the anionic inorganic counterions. The shift of aqueous two‐phase region is strengthened following the Hofmeister series. All the experiments were performed at 318.15 K.     

Study on the non-isothermal kinetics of decomposition of 4Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>·2H<Subscript>2</Subscript>O<Subscript>2</Subscript>·NaCl

The non-isothermal decomposition kinetics of 4Na₂SO₄·2H₂O₂·NaCl have been investigated by simultaneous TG-DSC in nitrogen atmosphere and in air. The decomposition processes undergo a single step reaction. The multivariate nonlinear regression technique is used to distinguish kinetic model of 4Na₂SO₄·2H₂O₂·NaCl. Results indicate that the reaction type Cn can well describe the decomposition process, the decomposition mechanism is n-dimensional autocatalysis. The kinetic parameters, n, A and E are obtained via multivariate nonlinear regression. The n ^th-order with autocatalysis model is used to simulate the thermal decomposition of 4Na₂SO₄·2H₂O₂·NaCl under isothermal conditions at various temperatures. The flow rate of gas has little effect on the decomposition of 4Na₂SO₄·2H₂O₂·NaCl.     

Salt resistivity of poly (4-vinyl benzoic acid) gel

Salt resistivity of poly (4-vinyl benzoic acid) (P4VBA) gel was investigated to compare with the super salt-resistivity that was found for poly (4-vinyl phenol)(P4VPh) gel containing an acidic proton and π-electron system. Poly(acrylic acid) (PAA) gel was also prepared and used as a reference gel containing only an acidic proton. P4VBA gel showed a moderate salt resistivity, which was less significant than that for P4VPh gel, in many kinds of inorganic salt solutions (MgCl₂, LiCl, NaCl, KCl, CsCl, KI, KSCN, Na₂SO₄). On the other hand, PAA gel showed a drastic deswelling in the presence of concentrated MgCl₂, LiCl, Na₂SO₄, and (NH₄)₂SO₄ solutions, and a significant swelling for KSCN solution. These contrastive behaviors between P4VBA and PAA gels strongly suggest that the combination of acidic proton and π-electron system is essential and necessary for polymer gels to be endowed with the salt resistivity.     

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.     

Diffusion in the Diaphragm Cell: Continuous Monitoring of the Concentrations and Determination of the Differential Diffusion Coefficient

We present a method to monitor continuously the electrical conductivity of the solutions in both compartments of a diaphragm cell in which diffusion is occurring. This allows a much smaller initial concentration difference to be applied across the diaphragm rather than the usual larger initial concentration difference. Together with an improved filling procedure and a more reproducible stirring device, these improvements lead to the determination of differential diffusion coefficients with accuracies comparable to those of the precise optical interferometric methods. This is shown for aqueous solutions of NaCl, KC1, Na₂SO₄, and MgSO₄ at 25 °C. By using aqueous solutions of HC1, the H⁺-exchange properties of the diaphragm and its influence on the measurements become detectable.     

Hydrolysis of (CH3)3Sn+ in Various Salt Media

The hydrolysis of trimethyltin(IV) has been studied by potentiometry (H⁺ -glass electrode) and calorimetry in various salt media (NaNO₃, NaCl, KCl, Na₂SO₄, and NaNO₃—NaCl mixtures). The effect of ionic strength on the hydrolysis constants is accounted for by a simple Debye–Hückel type equation and by Pitzer equations. The results allow us to obtain H for hydrolysis and the temperature dependence of the Pitzer parameters. The resulting coefficients can be used to examine the speciation of (CH₃)₃Sn⁺ in multicomponent electrolyte solutions, such as natural waters, over a wide range of temperature and ionic strength.