Study of the Evaporation of a Brine Involving the System Na+, Mg2+, K+, Cl−, S 4 2− –H2O: Crystallisation of oceanic salts

The evaporation of a Tunisian brine sample involving the system Na⁺, Mg²⁺, K⁺, Cl^–, S ₄ ^2– –H₂O was studied under atmospheric pressure and at ambient temperature. The selective densities of precipitation of halite (NaCl) and of co-precipitation of halite and astrakanite (Na₂Mg(SO₄)₂·4H₂O), halite and kaïnite (MgSO₄·KCl·H₂O) and epsomite MgSO₄·7H₂O were determined.During the evaporation of the studied brine, calculations related to the hypothetical composition of the solution in terms of the simple salts NaCl, MgSO₄, KCl and MgCl₂.This revised version was published online in November 2005 with corrections to the Cover Date.     

Enthalpies of mixing of some aqueous electrolytes at 373.15 K

The enthalpies of mixing of a variety of aqueous electrolytes at an ionic strength of 1.000 mol·kg^?1 have been measured at 373.15 K. The mixtures studied were LiBr + KBr, NaBr + KBr, KBr + (C₄H₉)₄NBr, NaCl + Na₂SO₄, NaCl + MgCl₂, MgSO₄ + Na₂SO₄, MgCl₂ + MgSO₄, NaCl + MgSO₄, and MgCl₂ + Na₂SO₄. In contrast to most previous enthalpies of mixing of alkali halides, the mixtures with multivalent ions studied here often have large temperature dependences. The results for the mixtures involving MgSO₄ are consistent with a higher degree of ion pairing as the temperature increases. The present measurements, together with Gibbs energies of mixing at 298.15 K, allow the calculation of Gibbs energies of mixing at the higher temperature. This appears to be the most accurate and convenient method available for determining Gibbs energies of mixing at high temperatures.     

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.     

Effects of Surfactant and Salt Species in Reverse Micellar Forward Extraction Efficiency of Isoflavones with Enriched Protein from Soy Flour

Suitability of reverse micelles of anionic surfactant sodium bis(2-ethyl hexyl) sulfosuccinate (AOT) and sodium dodecyl sulfate (SDS), cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) and nonionic surfactant polyoxyethylene p-t-octylphenol (TritonX-100) in organic solvent isooctane for extraction of soy isoflavone-enriching proteins was investigated. The results showed that the order of combined isoflavone contents was SDS>CTAB>Triton X-100>AOT, while the order of protein recovery was SDS>AOT>TritonX-100>CTAB. As compared with ACN-HCl extraction, the total amount of isoflavones was lower than reverse micellar extraction. Ion strength was one of the important conditions to control extraction of isoflavone-enriching proteins with AOT reversed micelles. For the six salt systems, KNO₃, KCl, MgCl₂, CaCl₂, NaCl, and Na₂SO₄, extracted fraction of isoflavone-enriching proteins was measured. Salt solutions greatly influenced the extraction efficiency of isoflavones in an order of KNO₃>MgCl₂>CaCl₂>KCl>NaCl>Na₂SO₄, while protein in an order of MgCl₂>CaCl₂>NaCl>KNO₃>Na₂SO₄>KCl.     

Interference of salts on the determination of lead by electrothermal atomic absorption spectrometry. Ion chromatographic study

The influence of various salts on the atomization signal of lead has been examined by using a transverse heated atomic absorption spectrometer. To get more information about interference mechanisms, volatilization of salts has been studied by ion chromatographic analysis of the residue left on the furnace after drying or charring. The use of a Pd/Mg chemical modifier in these model solutions has also been examined. In 0.1 M chloride medium, NaCl, MgCl₂ and CaCl₂ do not interfere significantly. However, their different behaviour in the furnace, and particularly hydrolysis of MgCl₂ influence greatly the charring curves of Pb. The use of a Pd/Mg modifier appears interesting only in the case of NaCl. Indeed, Pd stabilizes Pb sufficiently to permit the removal of NaCl by charring. In the case of MgCl₂, Pb is not sufficiently stabilized to remove chloride through hydrolysis of MgCl₂ or volatilization of MgCl₂. In the presence of CaCl₂, the Pb signal is delayed and coincides with the background absorption signal of CaCl₂; the stabilization effect is not sufficient to eliminate CaCl₂ by charring before atomization. At 0.1 M nitrate concentration, the presence of NaNO₃, Mg(NO₃)₂, and particularly Ca(NO₃)₂, greatly modifies the atomization signal shape of Pb. Pb is more stabilized in nitrate medium, but losses are observed at the decomposition step of nitrate salts. In this medium, the stabilization effect of Pd leads to a single peak signal and permits elimination of nitrate decomposition products before atomization. Interference effects are more important in the presence of 0.1 M sulphate salts and increase with the acidity of the medium. Na₂SO₄, which is reduced to Na₂S on the graphite, does not interfere significantly. However, the decomposition products of MgSO₄ and CaSO₄ induce an important interference effect on the determination of Pb which is stabilized in the furnace. In the case of Na₂SO₄, the use of the Pd/Mg modifier delays the atomization signal which coincides with the background absorption signal, leading to an important interference effect which cannot be eliminated by charring. In the presence of MgSO₄ and CaSO₄, the stabilizing effect of Pd permits the elimination of decomposition products of sulphate salts before atomization and suppresses the chemical interference effect.     

Calculation of the osmotic and activity coefficients of seawater at 25°C

The equation of Reilly, Wood, and Robinson was used to predict the osmotic coefficient of seawater and of its concentrates at molal ionic strengths of 0.5 to 6.0 at 25°C. The results agree closely with experimental data at ionic strengths below 5. The average difference in osmotic coefficients over the entire concentration range is 0.0014. The only serious discrepancy is at an ionic strength of 6, where a difference of 0.0068 is found. The accuracy of the predictions of osmotic coefficients prompted the calculation of the activity coefficients of NaCl, Na₂SO₄, MgCl₂, MgSO₄, KCl, and K₂SO₄ in the mixture. The calculated activity coefficients of NaCl and Na₂SO₄ agree within experimental error with previous measurements. This agreement demonstrates the prediction of activity and osmotic coefficients for complex mixtures.     

Influence of ionic composition in aqueous solution on wettability of rock surface-experiment and economics evaluation

In this study, the influence of different ionic composition in aqueous solution on the minerals surface wettability was studied. The differences effect of monovalent ion and divalent ions onto the wettability alteration were studied. The anions were Cl^- and SO₄^2-. The SO₄^2- could make the minerals surface more hydrophilic. Besides, the influence of NaCl, MgCl₂, CaCl₂, Na₂SO₄, K₂SO₄ and MgSO₄ on the mineral wettability alteration were studied. The results indicated that divalent ions showed significant impact on the minerals wettability alteration, compared with monovalent ion. The reasons were due to the fact that divalent ions showed higher ions adsorption than monovalent ion, and divalent ions have higher effect on compressing the electric double layer. The static contact angle and dynamic contact angle were measured. Different heavy oils were studied, including heavy oil with 100 ppm, heavy oil, heavy oil without resins, heavy oil without asphaltenes. The results showed that the asphaltenes would make it difficult for the heavy oils to liberate from minerals, thus decreasing the oil drops contact angle. Then the resins would decrease the heavy oil contact angles. CaCl₂/MgCl₂ and K₂SO₄ have synergistic effect on the change of the minerals surface wettability. Atomic force microscope (AFM) measurement indicated that the ions would effectively decrease the interaction force on the surface of heavy oil-minerals, which was beneficial to the heavy oil liberation. The roughness measurement indicated that the different ions would effectively increase the minerals surface wettability.     

Solvation of the Electrolytic Components of Seawater

A new modification of the adiabatic compressibility method of investigating solvation in solutions is presented and applied to the analysis of the following structurally-related characteristics of hydrated complexes of seawater electrolytes (NaCl, KCl, MgCl₂, CaCl₂, Na₂SO₄, MgSO₄) at different concentrations (0.1 to 5.0 mol⋅kg⁻¹) and temperatures (278.15 to 308.15 K): solvation numbers (h) and their dependences on concentration, volumes of stoichiometric mixtures of ions without their hydration shells (V _2h ), compressibilities (β _1h ) and molar volumes of water in their solvation shells (V _1h ), their dependences on concentration and temperature, etc.     

Direct determination of traces of molybdenum in synthetic sea water by atomic absorption spectrometry with electrothermal atomization and selective volatilization of the salt matrix

A simple and rapid method is described for the direct determination by graphite-furnace atomic absorption spectrometry (HGA-2100) of traces of molybdenum (O.1–4 ng) in synthetic sea water. It is shown that the salt matrix can be removed completely by selective volatilization at 1700–1850°C, but the original presence of NaCl, Na₂SO₄, and KCl causes a considerable decrease in molybdenum absorbance, and MgCl₂ and CaCl₂ a pronounced enhancement. The presence of MgCl₂ prevents the depressive effects. Samples of less than 50 μl can be analyzed directly without using a background corrector, with a precision of<10%.     

老山汉墓土遗址盐分调查与分布规律探索

老山汉墓土遗址中可溶-微溶盐导致遗址表面酥碱、起甲、泛白和块状脱落等病害较为严重.利用X射线荧光光谱(XRF)、X射线衍射仪(XRD)、X射线光电子能谱(XPS)以及离子色谱(IC)等方法测定了老山汉墓遗址不同取样位置及距遗址表面不同深度处可溶盐的成分及含量,并分析了盐分对遗址破坏的可能机制.结果表明,该遗址的主要有可溶盐有Na2SO4、Na2SO4·10H2O、Na Cl、Na12Mg7(SO4)13·15H2O,微溶盐有Ca SO4、Ca SO4·2H2O,此外还含有少量的Ca Cl2、KNO3、KCl、Mg Cl2、K2SO4、Mg SO4等盐分.随着取样深度增加,各盐分的种类及含量有所减少,此分布规律可能与可溶盐的赋存环境及水分运移有关.试验结果对于老山汉墓土遗址的保护措施具有一定的参考价值.     

Suppression of interferences in the determination of lead in natural and drinking waters by graphite-furnace atomic absorption spectrometry

The problem of matrix interference encountered in the determination of lead in natural and drinking waters by graphite furnace atomic absorption spectrometry is examined by looking at the individual effects of various constituent salts (NaCl, KCl, MgCl₂ and CaCl₂, Na₂SO₄, KH₂PO₄ and Mg(NO₃)₂), of which MgCl₂ and Na₂SO₄ interfered most severely. The use of the L'vov platform decreased the sulphate interference, but was not successful in removing the other interferences. The mixture of 0.05% (w/v) lanthanum (as LaCl₃) and 1% (v/v) nitric acid previously proposed for wall atomisation was found to be effective in controlling the interferences. Nitric acid alone removed almost completely the effects of MgCl₂ and CaCl₂, but had little effect on the interference of sulphate, which required the addition of lanthanum for suppression. The removal of interferences in real water samples by the lanthanum/nitric acid mixture is demonstrated by comparison of results obtained by this approach with those obtained by atomic fluorescence spectrometry and by flame atomic absorption spectrometry after preconcentration by evaporation.     

High temperature thermogravimetry of chlorides and sulphates : A study of the application to soils

Quantitative volatilization of NaCl and KCI occurs between 900 and 1200°. CaCl₂ and MgCl₂ are converted to the oxides at lower temperatures. CaSO₄, Na₂SO₄ and K₂SO₄ require the admixture of quartz to catalyse their decomposition with a total loss of SO₃ between 1150 and 1335°. MgSO₄ does not require quartz for its decomposition. The catalytic effects of Al₂O₃ and Fe₂O₃ on sulphate decomposition were also examined. The findings were applied to the analysis of saline soils. The thermogravimetric determination of chlorides in soils is subject to several interferences, but the conditions are more favourable for sulphates.     

Equilibria in the system containing chloride and sulphates of potassium and magnesium

Reciprocal salt-pair system 2KC1 + MgSO₄ ⇌ K₂SO₄ + MgCl₂ has been studied at 35° C to eliminate the discrepancies reported by different workers and for correlating the experimental data with natural evaporation of brine (without NaCl) so as to recover potash salts.     

The PVT properties of concentrated aqueous electrolytes. VIII. The volume changes for mixing the major sea salts at an ionic strength of 3.0 from 5 to 95°C

The densities of mixtures of the six possible combinations of the four major sea salts (NaCl, Na₂SO₄, MgCl₂, and MgSO₄) have been measured at a constant ionic strength of I=3.0 at the temperatures 5, 25, 55, and 95°C. The results have been used to determine ΔV_m, the volume change for mixing the major sea salts, which were fitted to equations of the from $$\Delta V{\text{m = }}y2y3I^2 \left[ {v0 + v1\left( {1 - 2y{\text{3}}} \right)} \right]$$ where y₁ is the molal ionic strength fraction of solute i, and v_o and v₁ are parameters related to the interaction of like-charge ions. The cross-square rule was verified at each of the temperatures of study, but the rule did not hold as well at the higher temperatures. The temperature dependence of the volume change for mixing ΔV_m was examined for each of the six mixtures. It was found that the two mixtures NaCl?Na₂SO₄ and MgSO₄?MgCl₂ showed little or no variation of ΔV_m with temperature, while the other mixtures showed considerable temperature dependence. These results indicate that the anion-anion interactions of Cl^? and SO ₄ ^2? do not vary with temperature, while the cation-cation interactions of Na⁺ and Mg²⁺ are temperature sensitive. Explanations for these results based on ion-water inter actions are presented.     

Sea salt deliquescence and crystallization in atmosphere: an in situ investigation using x‐ray phase contrast imaging

X‐ray phase contrast imaging (PCI) based on synchrotron radiation was introduced for the first time as an in situ imaging way to investigate sea salt phase change, i.e. deliquescence and crystallization in atmospheric environment. A performance on the deliquescence of pure NaCl, which is the dominant component in sea salt, demonstrated that this technique can directly observe the change of core particle and differentiate the outer water layer clearly in solid‐aqueous system of ~100 µm scale. The imaging results showed that sea salt particle deliquesced on a large scale of relative humidity (RH) between 34 and 97% RH as a solid–liquid drop, while no clear deliquescence RH was observed during the process. According to the drop size growth curve, sea salt deliquescence can be divided into three steps, namely water accumulating step (34–75% RH), bulk melting step (75–86% RH) and delay dissolving step (>86% RH), which are most probably dominated by grouped components as MgCl₂/CaCl₂/MgSO₄, NaCl and Na₂SO₄/KCl/K₂SO₄, respectively. Instead at a sole RH, the crystallization of sea salt solution occurred at a range of 46–58% RH, which well agreed with the theory proposed by Ge et al. The aqueous‐solid condition provided by sea salt deliquescence and crystallization may greatly enhance the heterogeneous chemical reactions in atmosphere. Copyright © 2012 John Wiley & Sons, Ltd.     

Isopiestic Investigation of the Osmotic and Activity Coefficients of {yMgCl2+(1−y)MgSO4}(aq) and the Osmotic Coefficients of Na2SO4⋅MgSO4(aq) at 298.15 K

Isopiestic vapor-pressure measurements were made for {yMgCl₂+(1−y)MgSO₄}(aq) solutions with MgCl₂ ionic strength fractions of y=(0,0.1997,0.3989,0.5992,0.8008, and 1) at the temperature 298.15 K, using KCl(aq) as the reference standard. These measurements for the mixtures cover the ionic strength range I=0.9794 to 9.4318 mol⋅kg⁻¹. In addition, isopiestic measurements were made with NaCl(aq) as reference standard for mixtures of {xNa₂SO₄+(1−x)MgSO₄}(aq) with the molality fraction x=0.5000 that correspond to solutions of the evaporite mineral bloedite (astrakanite), Na₂Mg(SO₄)₂⋅4H₂O(cr). The total molalities, m _T=m(Na₂SO₄)+m(MgSO₄), range from m _T=1.4479 to 4.4312 mol⋅kg⁻¹ (I=5.0677 to 15.509 mol⋅kg⁻¹), where the uppermost concentration is the highest oversaturation molality that could be achieved by isothermal evaporation of the solvent at 298.15 K. The parameters of an extended ion-interaction (Pitzer) model for MgCl₂(aq) at 298.15 K, which were required for an analysis of the {yMgCl₂+(1−y)MgSO₄}(aq) mixture results, were evaluated up to I=12.075 mol⋅kg⁻¹ from published isopiestic data together with the six new osmotic coefficients obtained in this study. Osmotic coefficients of {yMgCl₂+(1−y)MgSO₄}(aq) solutions from the present study, along with critically-assessed values from previous studies, were used to evaluate the mixing parameters of the extended ion-interaction model.     

PVT properties of concentrated aqueous electrolytes. II. Compressibilities and apparent molar compressibilities of aqueous NaCl,Na2SO4, MgCl2, and MgSO4 from dilute solution to saturation and from 0 to 50°C

The relative sound velocities (U-U°) of aqueous NaCl, Na₂SO₄, MgCl₂, and MgSO₄ solutions were measured from 0.05m to saturation and from 0 to 45°C. The sound speeds were combined with our earlier work and fitted to a function of molality and temperature to standard deviations within 0.3 m-sec^–1. The adiabatic compressibilities, _s, were determined from the sound speeds and used to calculate adiabatic apparent molar compressibilities, K_,s, isothermal compressibilities, , and apparent molar compressibilities, K, were determined from the adiabatic values using literature data for expansibilities and heat capacities. The values of K have been extrapolated to infinite dilution using an extended limiting law. The resulting K⁰ at various temperatures are in reasonable agreement with literature values. The results of this study have been combined with our earlier results to derive a secant bulk modulus equation of state for NaCl, Na₂SO₄, MgCl₂, and MgSO₄ solutions valid from 0 to 50°C and 0 to 1000 bar.     

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.     

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.