Pure NaCl Solution Research Articles

지표수 조건의 나노여과공정에서 파울링 및 스케일링이 화약류 물질 잔류에 미치는 영향 연구 - 케익층 형성 및 농도분극 영향 분석

The combined impact of Dissolved Organic Matter (DOM) fouling and inorganic (CaSO4,Ca3(PO4)2) scaling on the retention of TNT (2, 4, 6-Trinitrotoluene), RDX (Hexahydro1, 3, 5trinitro1, 3, 5triazine) and HMX (1, 3, 5, 7-Tetranitro-1, 3, 5, 7-tetrazocane) explosive contaminants by nano-filtration membrane were studied, since organic fouling and salt scaling are the major limitations for membrane filtration. Results reported here indicate that DOM fouling layer with a humic acid does not necessarily lead to an immediate loss of permeate flux but can result in a severe impact on the flux loss when both humic acid and inorganic scaltants were presented simultaneously. The Ca3(PO4)2 mixed with humic acid showd most sever flux loss (42%) compared to that of only humic acid presence (8%). It could be a result that the scaling formation of the NF membrane was dominated by cake layer formation of DOM and it was along with pore blocking by the formation of crystals inside the porous active matrix of the NF membrane. In addition, these results indicated that the membrane selectivity of the explosives retention trended correlated with respect to increasing explosives size (listed by MW) based on greater steric interactions and followed the order (MW, g mol; removal, %): HMX (296.15; 83%) >> RDX (222.12; 49%) ≋ TNT (227.13; 32%). Because the scaling and fouling layer could lead to a additional cake-enhanced concentration polarisation effect, the retention of explosives with the presence of humic acid in the feed solution and inorganic scaling formation on top of an organic fouling layer do not differ substantially retention from that of pure DI feed and NaCl solution.

Experimental and modelling study of the solubility of CO2 in various CaCl2 solutions at different temperatures and pressures

Study of the thermodynamic behaviour of CaCl2-H2O-CO2 systems is important in different scientific areas in the chemical and petroleum engineering fields. For example, a system including salt-H2O-CO2 is a common system in CO2 geological storage. During carbonate matrix acidizing, this mixture also appears as the spent acid. Hence, study of the behaviour of this system and the solubility of CO2 in CaCl2 brine in different thermodynamic conditions is critical. In this study, CO2 solubility in 0, 1.90 and 4.80 mol/L CaCl2 solutions at 328.15 to 375.15 K and 68.9 to 206.8 bar were measured. These values are normal for oil reservoirs. A popular thermodynamic model is available in the literature for estimating the CO2 solubility in pure water and NaCl solutions. In this paper, the available model was modified by experimental work to be applicable for CaCl2 as well. Based on the measured data, the component interaction parameters in the base model were adjusted for a CaCl2-H2O-CO2 system. The developed model could predict CO2 solubility in different conditions with remarkable accuracy, particularly for high concentration solutions and at high pressures. This improvement is up to 65% better than in the base model. This model can be used in Darcy scale models for predicting wormhole propagation during carbonate matrix acidizing.

The behavior of polyaniline-coated PVC membrane based on 7,16-didecyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane for ph measurements in highly acidic media

Polyaniline (PANI) chemically coated on poly(vinyl chloride) (PVC) membrane based on a neutral carrier 7,16-didecyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (kryptofix 22 DD) as the active component has been developed for determination of pH values ranging from pH 0.1–1. The effect of experimental parameters such as membrane composition, nature and amount of plasticizer, lipophilic additives and thickness of PANI film on the potential response of the pH electrode was investigated. The electrode has an apparent Nernstian response slope of 54.5 ± 0.4 mV pH−1 (at 20°C). The equilibrium water content of the electrode was determined in pure water and NaCl solution (I = 0.1 mol Kg−1). The electrode had low electric resistance, good potential stability and reproducibility (±1.5 mV, n = 10). It has a rapid potential response to changes of pH (15 s). The excellent performance in terms of linearity, stability and fast response makes this device suitable for pH measurements in highly acidic media.

Effect of Solution Composition on the Energy Production by Capacitive Mixing in Membrane-Electrode Assembly.

In this work, we consider the extent to which the presence of multivalent ions in solution modifies the equilibrium and dynamics of the energy production in a capacitive cell built with ion-exchange membranes in contact with high surface area electrodes. The cell potential in open circuit (OCV) is controlled by the difference between both membrane potentials, simulated as constant volume charge regions. A theoretical model is elaborated for steady state OCV, first in the case of monovalent solutions, as a reference. This is compared to the results in multi-ionic systems, containing divalent cations in concentrations similar to those in real seawater. It is found that the OCV is reduced by about 25% (as compared to the results in pure NaCl solutions) due to the presence of the divalent ions, even in low concentrations. Interestingly, this can be related to the “uphill” transport of such ions against their concentration gradients. On the contrary, their effect on the dynamics of the cell potential is negligible in the case of highly charged membranes. The comparison between model predictions and experimental results shows a very satisfactory agreement, and gives clues for the practical application of these recently introduced energy production methods.

Computer simulation studies of Aβ37-42 aggregation thermodynamics and kinetics in water and salt solution.

In vivo self-assembly of proteins into aggregates known as amyloids is related to many diseases. Although a large number of studies have been performed on the formation of amyloid, the molecular mechanism of polypeptide aggregation remains largely unclear. In this paper, we studied the aggregation of amyloid-forming peptide Aβ37-42 using all-atom molecular dynamics simulations. Using the integrated temperature sampling (ITS) simulation method, we observed the reversible formation of Aβ37-42 oligomers. The free-energy landscape for the polypeptide association was calculated, and aggregated states were then defined based on the landscape. To explore the kinetics and especially salt effects on the process of polypeptide aggregation, normal MD simulations were performed in pure water and NaCl solution, respectively. We then used the transition path theory (TPT) to analyze the transition network of polypeptide aggregation in solution. The dominant pathways of Aβ37-42 aggregation were found to differ significantly in pure water and the salt solution, indicating the change of molecular mechanism of polypeptide aggregation with the solution conditions.

Roadway Deicer Effects on the Germination of Native Grasses and Forbs

Normal seed germination of native herbaceous species can be reduced by high concentrations of deicer products and their constituent salts. Chloride salts are commonly used during the winter months in temperate climates to remove ice and snow. Although these products greatly improve driving conditions, they can have detrimental effects on the vegetation growing along highways. The purpose of this laboratory study was to determine the impact of a magnesium-based deicer product and a sodium-based deicer product and the major salts they contain on the germination and viability of several species of grasses and forbs native to Colorado and planted in revegetation seedings there. Seeds were placed on blotter paper saturated with either a water control, one of three concentrations of each of the deicing solutions, or one of three concentrations of a pure NaCl or MgCl2 solution. Increasing concentrations of salt ions generally resulted in delayed and reduced normal seed germination, especially the sodium- and magnesium-based deicer solutions. Germination for most species was lower when seeds were grown in deicer solution compared with germination percent of seeds grown in the pure salt solutions. Some species were more tolerant of one of the salts and deicers. Species with C4 photosynthetic pathway were more tolerant than C3 species of high concentrations of both deicer products. Those species which attained the highest germination percent under moderate or high solution concentrations included blue grama, buffalograss, little bluestem, mountain brome, and slender wheatgrass.

Effect of Doping Agent on Elution Profile of Tc-99m Generationand Labeling of Tc-99m With

Effect of doping agent on elution profile of Tc-99m generation and labeling of Tc-99m with MDP (Methylene diphosphonate) were carried out and studied. Tc -99m is one of the most talked element of modern radio pharmacy for its multiple application in diagnosis.Tc-99m is produced from Mo-99 through radioactive decay process. In our work two column chromatographic generator were made with Alumina column and loaded with Mo-99 which would be converted into Tc-99m eventually. Elution was taken by passing saline( 1 mL 0.9% NaCl solution and 1 mL 0.9% NaCl solution with 0.0045% NaNO3 as doping agent) each time and the activities of Tc -99m was measured by a Dose Calibrator. Elutions of Tc-99m were carried out several times and each time activity was measured. It is observed that almost 60 -75 % activity can be found in 2nd elution. Studying elution profile it is seen that activity curve reaches at pick in 2nd elution and afterwards gradually slopes down. Each time better activity is achieved by using pure saline. In spite of lower activity, this research resulting highly recommendation of using NaNO3 as a doping agent in NaCl saline in case of using elution because of its higher purity and RCP value . Tc -99m is applied over a biological body as a labeled compound . In this case MDP was used as a labeling compound . With a view of carrying out the RCP value of labeled compound, paper chromatography technique is done with various mobile phases in Whatman No 1 paper. Purity (%) is ranging from 30 – 90 % and NaNO3 doped NaCl radioactive solution shows better purity performance than pure NaCl solution in every different mobile phase . DOI: http://dx.doi.org/10.3329/jce.v27i2.17800 Journal of Chemical Engineering, IEB Vol. ChE. 27, No. 2, December 2012: 41-45

The behaviour of polyaniline-coated Poly(vinyl chloride) membrane based on 7, 16-didecyl-1, 4, 10, 13-tetraoxa-7, 16-diazacyclooctadecane for pH measurements in highly acidic media

Polyaniline (PANI) chemically coated on poly(vinyl chloride) (PVC) membrane based on a neutral carrier 7,16-didecyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (kryptofix 22 DD) as the active component has been developed for determination of pH values ranging from pH 0.1–1. The effect of experimental parameters such as membrane composition, nature and amount of plasticizer, lipophilic additives and thickness of PANI film on the potential response of the pH electrode was investigated. The electrode has an apparent Nernstian response slope of 54.5 ± 0.4 mV pH−1 (at 20°C). The equilibrium water content of the electrode was determined in pure water and NaCl solution (I = 0.1 mol Kg−1). The electrode had low electric resistance, good potential stability and reproducibility (±1.5 mV, n = 10). It has a rapid potential response to changes of pH (15 s). The excellent performance in terms of linearity, stability and fast response makes this device suitable for pH measurements in highly acidic media.

純水およびNaCl溶液の乾湿繰り返し環境におけるAl合金の腐食挙動

純水およびNaCl溶液の乾湿繰り返し環境におけるAl合金の腐食挙動

Potential of brackish water and brine for energy generation by salinity gradient power-reverse electrodialysis (SGP-RE)

Salinity Gradient Power-Reverse Electrodialysis (SGP-RE), tested on brackish water/solar pond brine, resulted in maximum power density of 1.13 W m−2 cell pair, 63% less than that of pure NaCl solutions with comparable salinity.

Experimental study on non-equilibrium fraction of NaCl solution circulatory flash evaporation

Non-equilibrium performance of NaCl solution is different from that of pure water due to boiling point elevation (BPE) of NaCl aqueous solution. It's necessary to conduct experiments for NaCl solution circulatory flash evaporation. Experiments were conducted with flow rates of 400, 600, 800, 1000, and 1200L·h−1, initial water film heights ranging from 100 to 265mm, initial water film concentrations of 0, 5%,10% and at pressures of 7.4, 12.3, 19.9, and 31.2kPa. Two different benchmarks using the saturate temperatures of pure water and NaCl solution were chosen to calculate the non-equilibrium fraction (NEF) for NaCl solution circulatory flash evaporation, and comparison between the two methods was also performed. Results showed that the method using the saturate temperature of NaCl solution was reasonable to reveal the essence of NaCl solution flash evaporation. NEF considering BPE augmented to a peak value at first and decreased monotonously when the superheat increased. The NEF value increased with the increasing initial water film height and concentration but decreased with the increasing mass flow rate and flash chamber pressure. Moreover, the NEF curve of NaCl solution was coincident with that of pure water in presented 10% NaCl solution flash evaporation cases.

Study of membrane fouling in cross-flow vacuum membrane distillation

Membrane fouling is one of the main obstacles to membrane distillation (MD) applications in desalination and other fields. Membrane scaling influences the efficiency and performance of vacuum membrane distillation (VMD). In this study, the process of a periodic membrane scaling experiment was investigated in detail by using a cross-flow hollow fiber membrane module. In the experiment, water flux significantly decreases from 42.5kg/(m2h) to 4.1kg/(m2h) because of membrane scaling; by comparison, water flux decreases from 42.7kg/(m2h) to 30.4kg/(m2h) in the blank experiment which is only affected by concentration and polarization. The blank experiment is performed under the same operating conditions as the periodic membrane scaling experiments, in which pure NaCl solution is used as feed. Scaling deposits form on/in membrane pores. Gas permeability experiments indicate that the membranes exhibit poorer transport properties as a result of aggravation of fouling and have smaller yield of MD. The scaling layer negatively affects heat and mass transfer in the feed near the evaporation surface. Membrane scaling further enhances temperature and concentration polarization, thereby decreasing the permeate flux. Experimental results further indicate that the overall heat transfer coefficient is reduced from 4569.4W/(m2K) to 2346.6W/(m2K) and the mass transfer coefficient in the membrane is reduced from 3.88kg/(m2Pah) to 2.18kg/(m2Pah) as scaling increases. Scanning electron microscopy (SEM) coupled with energy dispersion spectrometry (EDS) was employed to analyze the morphologies and compositions of the deposits formed on/in the membrane. The major component of the deposits is Ca; small amounts of Mg and S are also detected. The different morphologies of the deposits are significantly determined by various feed compositions.Using Bohai seawater, we investigated membrane fouling on the basis of VMD. The results are important for VMD application in seawater desalination.

Helix Formation by Alanine-Based Peptides in Pure Water and Electrolyte Solutions: Insights from Molecular Dynamics Simulations

Specific ion effects on oligopeptide conformations in solution are attracting strong research attention, because of their impact on the protein-folding problem and on several important biological-biotechnological applications. In this work, we have addressed specific effects of electrolytes on the tendency of oligopeptides toward formation and propagation of helical segments. We have used replica-exchange molecular dynamics (REMD) simulations to study the conformations of two short hydrophobic peptides [Ace-(AAQAA)3-Nme (AQ), and Ace-A8-Nme (A8)] in pure water and in aqueous solutions of sodium chloride (NaCl) and sodium iodide (NaI) with concentrations of 1 and 3 M. The average helicities of the AQ peptide have been analyzed to yield Lifson-Roig (LR) parameters for helix nucleation and helix propagation. The salt dependence of these parameters suggests that electrolytes tend to stabilize the helical conformations of short peptides by enhancing the helix nucleation parameter. The helical conformations of longer oligopeptides are destabilized in the presence of salts, however, because the helix propagation parameters are reduced by electrolytes. On top of this general trend, we observe a significant specific salt effect in these simulations. The hydrophobic iodide ion in NaI solutions has a high affinity for the peptide backbone, which reflects itself in an enhanced helix nucleation and a reduced helix propagation parameter with respect to pure water or NaCl solutions. The present work thus explains the computational evidence that electrolytes tend to stabilize the compact conformations of short peptides and destabilize them for longer peptides, and it also sheds additional light on the specific salt effects on compact peptide conformations.

β-Amino Acid and Amino-Alcohol Conjugation of a Nonsteroidal Anti-Inflammatory Drug (NSAID) Imparts Hydrogelation Displaying Remarkable Biostability, Biocompatibility, and Anti-Inflammatory Properties

A well-known nonsteroidal anti-inflammatory drug (NSAID), namely, naproxen (Np), was conjugated with β-alanine and various combinations of amino alcohols and l-alanine. Quite a few bioconjugates, thus synthesized, were capable of gelling pure water, NaCl solution (0.9 wt %), and phosphate-buffered saline (PBS) (pH 7.4). The hydrogels were characterized by rheology and electron microscopy. Hydrogelation was probed by FT-IR and temperature-variable (1)H NMR studies. Single-crystal X-ray diffraction (SXRD) of a nonhydrogelator and a hydrogelator in the series established a useful structure-property (gelation) correlation. MTT assay of the hydrogelators in the mouse macrophage RAW 264.7 cell line showed excellent biocompatibility. The prostaglandin E2 (PGE2) assay of the hydrogelators revealed their anti-inflammatory response, which was comparable to that of the parent NSAID naproxen sodium (Ns).

Mathematical modeling of nanofiltration for concentrated electrolyte solutions

As one of the most newly developed liquid-phase membrane separation processes, nanofiltration (NF) is used in several industrial and environmental applications due to low energy consumption and elevated flux rates. In spite of several attempts for modeling NF separation ranging from rigorous space-charge approaches to simpler irreversible thermodynamics, neither have been totally sufficient either due to extensive computational requirements limiting their application in multi-component systems or oversimplifying assumptions leading to loss of generality. A promising model as a compromise between simplicity and accuracy can then be very helpful in this regard.This paper is an effort for modeling the nanofiltration separation process based on the modified extended Nernst–Planck equation (MENP) for solute transport through membrane active layer which is improved for concentrated electrolyte solutions. Based on simulation results, the effect of high ionic concentrations on the rejection of chloride ion is investigated, in case of pure NaCl solutions. The modified version of ENP, takes into account the variations of activity coefficient and the resulting influence on the retention behavior by increasing the ionic strength. The results show significant reduction of the predicted rejection by increasing the ionic strength.

Study on steam-carrying effect in static flash evaporation

Study on steam-carrying effect in static flash of both pure water and aqueous NaCl solution was present. Properties, including steam-carrying ratio, waterfilm height drop and equilibrium concentration of waterfilm, were measured in experiments. Their dependences on separating height, initial waterfilm concentration and mean pressure difference were analyzed. Particularly, steam-carrying ratio was defined as the mass ratio of be-carried liquid and generated steam. Results suggested that this ratio increased with the decreasing of separating height or the rising of initial waterfilm concentration, and a peak value existed in its evolution versus mean pressure difference. At last, according to experimental results and basic principles a calculating model for steam-carrying effect in static flash was built.

Salting Effects on Protein Components in Aqueous NaCl and Urea Solutions: Toward Understanding of Urea-Induced Protein Denaturation

The mechanism of urea-induced protein denaturation is explored through studying the salting effect of urea on 14 amino acid side chain analogues, and N-methylacetamide (NMA) which mimics the protein backbone. The solvation free energies of the 15 molecules were calculated in pure water, aqueous urea, and NaCl solutions. Our results show that NaCl displays strong capability to salt out all 15 molecules, while urea facilitates the solvation (salting-in) of all the 15 molecules on the other hand. The salting effect is found to be largely enthalpy-driven for both NaCl and urea. Our observations can explain the higher stability of protein's secondary and tertiary structures in typical salt solutions than that in pure water. Meanwhile, urea's capability to better solvate protein backbone and side-chain components can be extrapolated to explain protein's denaturation in aqueous urea solution. Urea salts in molecules through direct binding to solute surface, and the strength is linearly dependent on the number of heavy atoms of solute molecules. The van der Waals interactions are found to be the dominant force, which challenges a hydrogen-bonding-driven mechanism proposed previously.

Thermophysics of the Interfacial Region and Its Impact on Instability and Rupture of Thin Free Liquid Films

Merging of adjacent bubbles is a particularly important process in nucleate boiling heat transfer, bubbly two-phase flow in small tubes, and the mechanisms that dictate the Leidenfrost transition. The merging process is ultimately associated with the rupture of the liquid film separating two bubbles, and the stability of the liquid film dictates whether coalescence is likely to occur. This paper examines two methods of exploring how the molecular-level features of the thin film and its interfaces affect the stability of the film and its subsequent impact on bubble merging. One method is an extended molecular capillarity model that has been developed for a free liquid film bounded by two liquid–vapor interfacial regions. This model predicts that as film thickness diminishes, a point is reached at which the mean centerline density in the film is between the spinodal limits for the fluid, implying that the film core lacks intrinsic stability. This suggests that loss of intrinsic stability may be the mechanism for film rupture in some cases. The second method examined here is use of molecular dynamics simulations to examine film structure and stability. Simulations using a Lennard–Jones interaction potential for non-polar fluids and the SPC/E potential for water and salt water are examined. Results of these explorations indicate that for water–NaCl solution films, surface tension increases with increasing NaCl concentration. These predictions are shown to be consistent with measured surface-tension data for such solutions. The results also indicate that for pure water and NaCl solutions, below a threshold thickness, the surface tension decreases with film thickness. Wave interface stability theory implies that this tends to make the film less stable. The implications of the results of these investigations for bubble merging in two-phase flow and boiling processes are also examined.

Self-diffusion coefficients and orientational correlation times in aqueous NaCl solutions: Complementarity with structural investigations

The dynamical properties of pure water and aqueous NaCl solutions over a wide range of salt concentrations (0–6 m) at ambient conditions are characterized by molecular dynamics (MD) simulations. MD simulations are performed with a flexible SPC water model as a solvent, while the ions are treated as charged Lennard–Jones particles. In this paper, attention has been focused on the self-diffusion coefficients ( D i ) of ions and water molecules and on orientational correlation time of water molecules. It is found that the self-diffusion coefficients decrease with ion concentration. Moreover, the self diffusion coefficients of sodium and chloride at higher salt concentrations are very comparable which may be due to the formation of clusters of these ions. The deduced rotational dynamics speeds up as the salt concentration increases. Some complementarities between dynamical properties and structural ones, recently obtained, are carried out.

Tolérance à la salinité d'une poaceae à cycle court : la sétaire ( Setaria verticillata L.)

The responses of growth, development, and nutrition to salt stress are examined in short-cycle Setaria verticillata. For these, two experiments are led. The first intended to study the effects of various concentrations of NaCl on the parameters of growth and nutrition during the vegetative phase. Fifteen-day-old platelets were grown on commercial peat irrigated with pure NaCl solutions (0 to 300 mM). After three weeks of culture, the plants were collected and divided into roots and shoots. The fresh and dry matter masses of the various bodies are given. The second experiment was intended to study the effect of different concentrations of NaCl on crop plants until maturity. The culture was led under the same conditions as the preceding one, but for three months until the end of the cycle (production and maturation of the seeds). At harvest, the plants were separated in roots, shoots, and grains. During all the development cycle, Setaria vertillata was very sensitive to salinity. The concentration of NaCl that caused an important reduction of dry weight production was about 75 mM. Dry matter deposition was more diminished in roots than shoots. The reduction of the production of growth observed seems associated with a higher accumulation of Na + in shoots and with a deficit alimentation of organs in K +. During the reproductive phase, salt affects the components of the output and induces variability on the level of the production of biomass as significant as that noted during the phase of vegetative growth. Lastly, the capacity of germination of seeds was strongly dependent on the salt concentration of the culture medium of the plants mothers, a total loss of viability appearing on crop plants collected in the presence of NaCl 300 mM. To cite this article: H. Ben Ahmed et al., C. R. Biologies 331 (2008).