Salting-in/Salting-out Mechanism of Carbon Dioxide in Aqueous Electrolyte Solutions

The solvation of carbon dioxide in sea water plays an important role in the carbon circle and the world climate. The salting-out/salting-in mechanism of CO2 in electrolyte solutions still remains elusive at molecule level. The ability of ion salting-out/salting-in CO2 in electrolyte solution follows Hofmeister Series and the change of water mobility induced by salts can be predicted by the viscosity B-coefficients. In this work, the chemical potential of carbon dioxide and the dynamic properties of water in aqueous NaCl, KF and NaClO4 solutions are calculated and analyzed. According to the viscosity B-coefficients, NaClO4 （0.012） should salt out the carbon dioxide relative to in pure water, but the opposite effect is observed for it. Our simulation results suggest that the salting-in effect of NaClO4 is due to the strongly direct anion-CO2 interaction. The inconsistency between＂ Hofmeister Series and the viscosity B-coefficient suggests that it is not always right to indicate whether a salt belongs to salting-in or salting-out just from these properties of the salt solution in the absence of solute.

Correlation and Prediction of Salt Effect on Vapor Liquid Equilibrium for the System of 2-Propanol/Water

Binary vapor liquid equilibrium （VLE） data were measured for the systems of 2-propanol/ ethanediol and ethanediol/potassium acetate （KAc）. VLE data for the system of propanol/ethanediol was tested using thermodynamic consistency test. The average values of Ayj and A P were 0.0776 and 0.1542 kPa, respectively. The above two sets of VLE data were correlated with the NRTL model. Ternary VLE data for the system of 2-propanol/water/KAc was used to obtain the more suitable parameters of NRTL model for binary systems of 2-propanol/KAc and water/KAc （called TDCM）. For multicomponent systems, ternary and quaternary, the VLE values predicted by the NRTL model agreed well with the literature data. Influence of KAc, ethanediol, and the mixture of KAc and ethanediol on volatility between 2- propanol and water was investigated respectively. The results showed that the above-mentioned materials and mixture had different influence on volatility between 2-propanol and water. The method for correlation and prediction of salt-containing VLE is simple and effective for the said system.

The remarkable effect of organic salts on 1,3,5-trioxane synthesis

The effects of organic salts on 1,3,5-trioxane synthesis were investigated through batch reaction and continuous production experiments. The organic salts used include sodium methanesulfonate（CH3NaO3S）, sodium benzenesulfonate（C6H5NaO3S）, sodium 4-methylbenzenesulfonate（C7H7NaO3S）, and sodium 3-nitrobenzene sulfonate（C6H4NNaO5S）. It was shown that the effects of organic salts on the yield of 1,3,5-trioxane in reaction solution and distillate follow the order CH3NaO3S ／C6H5NaO3S／C7H7NaO3S／C6H4NNaO5S, which is inversely related to the charge density of the anions of the organic salts. In comparison with Cl–-based salts such as magnesium chloride, organic salts have the advantages of less formic acid generation and low corrosion. Studies on water activity revealed that the effect of organic salts on the activity of water was quite small at low concentration of organic salts. UV–visible spectroscopy and vapor–liquid equilibrium experiments were performed to uncover the mechanisms that govern such effects. The results showed that the effect of organic salts on the yield of 1,3,5-trioxane relies primarily on their ability to increase the catalytic activity of sulfuric acid and increase the relative volatilities of 1,3,5-trioxane and water and of 1,3,5-trioxane and oligomers.

Salt Effect on the Liquid-Liquid Equilibrium of （Water ＋ Propionic Acid ＋ Cyclohexanol） System at T=（298.2,303.2,and 308.2） K

Effects of salt and temperature on the liquid phase equilibrium of the(water + propionic acid + cyclohexanol) system were investigated.The liquid-liquid equilibrium data in the presence of KCl for various salt ionic strength of 0.5,1.0,1.5,2.0,and 2.5 mol·dm3 and in absence of the salt at T=(298.2,303.2,and 308.2)K were determined.The experimental results were correlated based on the Othmer-Tobias equation and Pitzer ion-interaction model.Thermodynamic properties such as distribution coefficients and activity coefficients of propionic acid in water + cyclohexanol were determined.In addition,the separation factor,S,of the chosen solvent was obtained for the investigated system.

Salt-Containing Extractive Distillation of 1-Propanol/Water System 1.Prediction of Salt Effect on Vapor Liquid Equilibrium

This paper has studied the vapor-liquid equilibrium （VLE） for the salt-containing extractive distillation of the 1-propanol/water system. Binary VLE data were measured for the systems of 1-propanol （1）/KAc （4）, ethanediol （3）/KAc （4）, and 1-propanol （1）/ethanediol （3）, with the VLE data correlated with the NRTL model in order to obtain the model parameters of these binary systems. The binary VLE data cited in technical literature were correlated to obtain the model parameters for other binary systems. VLE data of ternary and quaternary systems predicted by the NRTI.： model agreed well with the literature data. The influence of KAc, ethanediol, and the KAc/ethanediol mixture on volatility between 1-propanol and water was investigated respectively. Test results showed that the above-mentioned materials （KAc, ethanediol） and their mixture （KAc and ethanediol） have different influence on the volatility. When x3=0.5, and x4=0.05, the azeotropic point can be elimi- nated. The NRTL model method of salt-containing VLE is simple and effective for the prediction of the system＇s VLE data.

Effect of Dissolved Cadmium Chloride and Ammonium Chloride Salts on the Enthalpy of Mixing of the Methanol＋Benzene System at 303.15 K

The effect of two dissolved inorganic salts,cadmium chloride CdCl2 and ammonium chloride NH4Cl,on the excess enthalpy of mixing(HE) of the binary system methanol + benzene measured at 303.15 K using an iso-thermal displacement calorimeter with vapor space is investigated in the present work. Compared to the salt-free system,a decreasing trend in the endothermicity of HE values is significant with the addition of CdCl2 salt but the decrease in the HE values is insignificantly smaller with the addition of NH4Cl salt. The experimental values of the enthalpy of mixing are fitted into a Redlich-Kister equation and the deviations in the values and the parameters are reported. The importance of the solute-solvent interactions and the solvent-solvent interactions are demonstrated from the increasing excess enthalpy of mixing values in the positive direction with the increase of salt concentration.

Infrared Absorption Intensity Analysis as a New Tool for Investigation of Salt Effect on Proteins

The native protein structures in buffer solution are maintained by the electrostatic force as well as the hydrophobic force, salt ions play an important role in maintaining the protein native structures, and their effect on the protein stability has attracted tremendous interests. Infrared spectroscopy has been generally used in molecular structure analysis due to its fingerprint resolution for different species including macromolecules as proteins. However spectral intensities have received much less attention than the vibrational frequencies. Here we report that the spectral intensities of protein amide I band, the finger prints for the protein secondary structures, are very sensitive to the local electric field known as Onsager reaction field caused by salt ions. IR absorbance thermal titrations have been conducted for a series of samples including simple water soluble amino acids, water soluble monomeric protein cytochrome c and dimeric protein DsbC and its single-site mutant G49R. We found that at lower temperature range （10-20℃）, there exists a thermal activated salting-in process, where the IR intensity increases with a rise in the temperature, corresponding to the ions binding of the hydrophobic surface of protein. This process is absent for the amino acids. When further raising the temperature, the IR intensity decreases, this is interpreted as the thermal activated breaking of the ion-protein surface binding. Applying Van＇t Hoff plot to the thermal titration curves, the thermodynamic parameters such as AH and AS for salting-in and ion unbinding processes can be derived for various protein secondary structural components, revealing quantitatively the extent of hydrophobic interaction as well as the strength of the ion-protein binding.

Salt Effect on the Phase Transition Behavior of Thermo-sensitive Polyamide

Phase transition behavior and influence of ions on the thermo-sensitive polyamide with polyethylene glycol as the main chain were studied in detail. By measuring the light transmission rates of polymer solutions, the change of its lower critical solution temperature （LCST） in the salt solution was investigated. It was found that a reversible phase transition of the polyamide occurred at the LCST and finished in a narrow temperature range. The LCST was associated with species of ions in salt solution. Anions had a great impact on the phase transition performance of the thermo-sensitive polyamide, while the cations had a slight influence on the phase transition. Different anions had different coagulation ability to ‘salt-out＇ the polyamide. The order was： CO2-3〉SiO2-3〉HPO2-4〉OH-〉Cl-〉HCO3-〉HSOa-〉NO2-〉NO3-.

Efficient Separation of Butyric Acid by an Aqueous Two-phase System with Calcium Chloride

One of the bottlenecks for bioproduction of butyric acid as bulk chemical is the difficulty in separating butyric acid from the fermentation broth,compared with the petroleum-based chemical synthesis method.In the present work,a novel separation methodology was developed based on an aqueous two-phase system with inor-ganic salts.Calcium chloride was screened out for effective separation of butyric acid from butyric acid-water-salt systems.Within appropriate concentration range of butyric acid and salt,butyric acid was enriched in the upper phase and most of calcium ions remained in the lower phase.This"salting out"effect is very efficient to separate butyric acid from the simulated butyrate fermentation broth,which consists of butyric acid and acetic acid with concentration ratio of 4︰1,so that the final ratio of butyric acid/acetic acid in the upper phase is improved to 9.87. The aqueous two-phase system was used to separate butyric acid from the actual fermentation broth with satisfac-tory result.

Determination of Vapor Pressures for Binary and Ternary Mixtures Containing Ionic Liquid 1-propyl-3-methylimidazolium Bromide

Vapor pressure values of binary systems water ＋ ethanol, water ＋ ionic liquid 1-propyl-3- methylimidazolium bromide （[PMIM] [Br]）, ethanol ＋ [PMIM] [Br] and ternary system water ＋ ethanol ＋ [PMIM] [Br] at different temperatures were measured by using a modified boiling point method in various concentrations of （16.66%, 33.7%）, （17.4%, 33.9%） and （16.5%, 32%） mass percent of ionic liquid, respectively. The experimental vapor pressures of solvent were well correlated by the Antoine-type equation, and the overall average absolute deviation （AAD） was found to be 0.39%. The experimental results for mixtures containing ionic liquid indicate that the vapor pressure of the solvents can be decreased noticeably to different extent due to the affinity difference between ionic liquid and solvent, which is similar to the salt effect of common inorganic salts. As a result, ionic liquid may find industrial applications in extractive distillations for the system with a low separation factor or even for an azeotropic mixture.

Experimental results for the vapor-liquid equilibria of 0(formaldehyde+1,3,5-trioxane+methanol+salt+water)systems and comparison with predictions

The salt effect on the vaporliquid phase equilibrium(VLE)of solvent mixtures is of significant interest in the industrial production of 1,3,5trioxane.Experimental data for the VLE of quinary systems(formaldehyde+1,3,5trioxane+methanol+salt+water)and their ternary subsystems(formaldehyde+salt+water),(1,3,5trioxane+salt+water),and(methanol+salt+water)were systematic measured under atmospheric pressure.The salts considered included KBr,NaNO_(3),and CaCl_(2).The extended UNIFAC model was used to describe the VLE of the saltcontaining reactive mixtures.The model parameters were determined from the experimental VLE data of ternary systems or obtained from the literature,and then were used to predict the VLE of systems(1,3,5trioxane+KBr+water),(methanol+KBr+water),(formaldehyde+KBr+water),and(formaldehyde+1,3,5trioxane+methanol+salt+water)with salt=KBr,NaNO_(3),and CaCl_(2).The predicted results showed good agreements with the measured results.Furthermore,the model was used to uncover the salt effect on the VLE of these multisolvent reactive systems.

Experimental study on geochemical characteristic of methane hydrate formed in porous media

The natural occurrence of methane hydrates in marine sediments has been intensively studied over the past decades, and geochemical charac-teristic of hydrate is one of the most attractive research fields. In this paper, we discussed the geochemical anomaly during hydrate formation in porous media. By doing so, we also investigated the temperature influence on hydrate formation under isobaric condition. It turns out that sub-cooling is an important factor to dominate hydrate formation. Larger subcooling provides more powerful driving force for hydrate formation. During the geochemical anomaly research, six kinds of ions and the total dissolved salt （TDS） were measured before and after the experiment in different porous media. The result is that all kinds of ionic concentration increased after hydrate formation which can be defined as salting out effect mainly affected by gas consumption. But the variation ratio of different ions is not equal. Ca^2＋ seems to be the most significantly influenced one, and its variation ratio is up to 80%. Finally, we theoretically made a model to calculate the TDS variation, the result is in good accordance with measured one, especially when gas consumption is large.

Interaction of cetyltrimethylammonium bromide with drug in aqueous/electrolyte solution:A combined conductometric and molecular dynamics method study

Interaction between beta-lactum antibiotic drug ciprofloxacin hydrochloride(CFH)and cationic surfactant cetyltrimethylammonium bromide(CTAB)was performed conductometrically in aqueous as well as in the occurrence of different salts(NaCl,KCl as well as NH_4Cl)over the temperature range of 298.15–323.15 K at the regular interval of 5 K.CFH drug has been suggested for the treatment of bacterial infections such as urinary tract infections and acute sinusitis.A clear critical micelle concentration(CMC)was obtained for pure CTAB as well as(CFH+CTAB)mixed systems.The decrease in CMC values of CTAB caused by the addition of CFH reveals the existence of the interaction between the components and therefore it is the indication of micelle formation at lower concentration of CTAB and their CMC values further decrease in attendance of salts.A nonlinear behavior in the CMC versus T plot was observed in all the cases.The ΔG_m^0 values are found to be negative in present study systems demonstrated the stability of the solution.The values of ΔH_m^0 and ΔS_m^0 reveal the existence of hydrophobic and electrostatic interactions between CFH and CTAB.The thermodynamic properties of transfer for the micellization were also evaluated and discussed in detail.Molecular dynamic simulation disclosed that environment of water and salts have impact on the hydrophobic interaction between CFH and CTAB.In water and salts,CTAB adopts spherical micelle in which charged hydrophilic groups are interacted with waters whereas hydrophobic tails form the core of the micelle.This hydrophobic core region is highly conserved and protected.In addition,micelle formation is more favorable in aqueous Na Cl solution than other solutions.

Corrosion Behavior of a Titanium Alloy in Hot Nitric Acid Condensate

The corrosion behavior of a titanium-5% tantalum alloy （Ti-STa） in hot nitric acid condensate was investigated to understand aging behavior ofreprocessing equipments. On the basis of long-term immersion tests, it was determined that the corrosion of Ti-STa in nitric acid condensate is accelerated with an increase in the concentration. The corrosion rate was nearly constant during the immersion test and the coupons suffered from uniform corrosion. In addition, it is important to note that the nitric acid concentration in the condensate increased on addition of metal salts to the heated nitric acid solution. The larger valence of metal ions was contributed to the increase in the concentration of nitric acid condensate. Consequently, the metal salt in the heated nitric acid solution accelerates the corrosion of Ti-STa in the condensate. Therefore, the nitric acid condensate condition should be carefully considered for the corrosion environment of titanium and its alloys.

Experimental Study on Liquid-Liquid Equilibria of Alcohol- Ester-Water-CaCl_2 System

The binary liquid-liquid equilibrium(LLE) data for salt-containing systems of 1-butanol+water+CaCl2, n-butyl acetate+water+CaCl2 and ethyl acetate+acetic acid+water+CaCl2 were determined and the salt effect was analyzed. The results showed that an obvious salt effect could be identified for the systems of 1-butanol+water+CaCl2 and ethyl acetate+acetic acid+water.

Fluorescence Spectra of Model Compounds for Light-emitting Alternating Copolymers in Heterogeneous Environments

In this paper, the fluorescence spectra of model compounds of light-emitting alternating copolymers. M (TPA-PPV) and M (TPA-PAV) (Scheme 1) were studied and the effect of KNO3 on the interaction between model compounds and ionic micelle-watts interface was also investigated. It is found that (I) The fluorescence changes of M (TPA-PPV) are related to the state of CTAB and SDS solution. (II)Aggregated state can be formed in M (TPA-PAV) solution at low concentration of CTAB. (III) Higher concentration of KNO3 may affect the interaction between model compounds and ionic micelle-water interface.

Study on Salt-Containing Extractive Distillation for the 2-Propanol/Water System

The salt-containing extractive distillation column and the salt-containing agent recovery column for the 2-propanol/water/ethanediol/KAc system were simulated by the NRTL model and the modified Rose Relaxation method. The simulation results showed that prediction of the salt effect in vapor-liquid equilibrium and the correlation method （TDCM） of NRTL parameters were suitable for the said system. Four different distillation technology processes were investigated; the results showed that the salt-containing extractive distillation process was the best one. The simulating design of the extractive distillation column was performed under the conditions of different total stage number, feeding location, reflux ratio, amount of mixed agent and concentration of KAc. The results showed that such factors as 17 stages, a feeding location at the 9th stage, a reflux ratio of 1.2, and a mixed agent feeding rate of 1.141 kmol/h, might be the best suited operating conditions. The simulating design was also done for the column for recovering the salt-containing agent. The simulation method of the salt-containing extractive distillation is simple and effective in this work.

LSER-based modeling vapor pressures of(solvent+salt) systems by application of Xiang-Tan equation

The study deals with modeling the vapor pressures of(solvent + salt) systems depending on the linear solvation energy relation(LSER) principles. The LSER-based vapor pressure model clarifies the simultaneous impact of the vapor pressure of a pure solvent estimated by the Xiang-Tan equation, the solubility and solvatochromic parameters of the solvent and the physical properties of the ionic salt. It has been performed independently two structural forms of the generalized solvation model, i.e. the unified solvation model with the integrated properties(USMIP) containing nine physical descriptors and the reduced property-basis solvation model. The vapor pressure data of fourteen(solvent + salt) systems have been processed to analyze statistically the reliability of existing models in terms of a log-ratio objective function. The proposed vapor pressure approaches reproduce the observed performance relatively accurately, yielding the overall design factors of 1.0643 and1.0702 for the integrated property-basis and reduced property-basis solvation models.

Quasi-Horizontal Arrangement of Solar Panels in Equatorial Zones： Problems and Proposed Solutions

Solar panels are oriented to the North （South） when the site is in the South （North） with a tilt angle close to the latitude. In the equatorial zone, the panels are quasi-horizontally arranged. This situation caused some problems： the panel is more rapidly covered with dust or salty mud that decreases its performance and degrades the protective glass. To overcome these difficulties, we evaluated theoretically and practically the energy lost by an incorrect tilt. The results are rather encouraging. Just 1.5% of total energy is lost when we tilted the panel at 10.0°. In practice, we realized that the loss of energy is fewer than we calculated it because of the reflected solar rays.

Effect of Different Salts on the Solubilities of Benzene and Diphenyl in t-Butyl Alcohol-Water Mixture and Hydrophobic Interaction

The solubilities of benzene and diphenyl in mixed solvents of t-butyl alcohol(TBA) and water with different salts have been determined at T = 298.15, 303.15, 308.15 and 313.15K. The molar fraction of TBA [x(TBA)] in mixed solvent is 0.045, and the molality of the salts (m_s)in mixed solvents are 0.000, 0.250, 0.500, 0.750 and 1.000 mol/kg, respectively. The standard Gibbsenergies of solution of benzene and diphenyl in the mixed solvents have also been calculated basedon the solubility data. The effects of different salts on the hydrophobic interaction (HI) forbenzene-benzene pair in the systems were discussed.