Physicochemical Properties Of Aqueous Solutions Research Articles

Protective action of water-soluble fullerene adducts on the example of an adduct with l-arginine

We present radioprotective, antiglycating, and photoprotective properties of a water-soluble C60 fullerene derivative with l-arginine (C60-Arg) and composite films based on collagen containing C60-Arg. The synthesis of these materials is described. The identification of the synthesised materials was carried out using modern physicochemical methods of analysis. The physicochemical properties of aqueous solutions of C60-Arg, such as, particle size distribution, zeta potentials, distribution coefficient in the octan-1-ol–water system were measured. The computer simulation of the process of C60-Arg association in aqueous and isotonic solutions was carried out using Molecular Dynamics. Composite films based on collagen containing C60-Arg demonstrate significant improvement in mechanical properties, cell adhesion, and cell proliferation when the nano-modifier is added. This shows high potential for the use of the C60-Arg adduct in biomedicine.

EFFECT OF THE FORM OF ELECTRIC DISCHARGE ON PHYSICOCHEMICAL PROPERTIES OF PLASMA-ACTIVATED DISTILLED AND GROUND WATERS

A comparative study of some physicochemical properties of aqueous solutions resulted from the treatment of distilled and ground waters by pulsed discharges has been performed. Changes in the pH value, the conductivity of the solution, and the content of NO3¯ anions and Ca++, Mg++, K+, and Na+ cations were studied. Water bodies were affected by active particles formed in the air under the action of a pulsed discharge, which is implemented in two options. The first option is conventionally called ‘bubble discharge’ since it assumes the ignition of a discharge in an air bubble in direct contact with a liquid. The second option is the case when active particles, which are formed in an air stream under the action of a barrier discharge, are blown into a liquid. It is shown that the bubble discharge in ground water gives the maximum performance for the NO3¯ anions, while in the case of barrier discharge the best performance in the formation of NO3¯ anions is observed in distilled water. The pH value for ground water increases from 8.1 to 8.6 in the course of a 10-minute treatment using both discharges. However, in the case of distilled water treatment an inverse relationship is observed, so its value decreases from 7.5 to 3.5 pH. A multiple increase in the content of Ca++ and Mg++ cations in the water sample is observed when groundwater treating. Presumably, their increase in solution is associated with the transition of insoluble salts of calcium and magnesium carbonates (constant water hardness) into water-soluble nitrates (temporary hardness). In addition to magnesium and calcium ions, potassium and sodium cations were monitored in water samples. Their concentration in water was insignificantly affected by the treatments with discharges.

Correlation between biological activity and physicochemical properties of sodium dodecylbenzenesulfonate in aqueous solutions

The purpose of this study was to establish a correlation between the effect of the pollutant content on the dimensional and physicochemical characteristics of the investigated solutions and its effect on aquatic organisms. To this end, the surface tension, electrical conductivity, pH, and redox potential of aqueous solutions of sodium dodecylbenzenesulfonate were measured in a wide concentration range (10–710–2 М). The change in the size and number of optical inhomogeneities was investigated using the small-angle reflection method in the micron range. In addition, the behavior of aquatic biological objects (Daphnia Magna) was studied in the investigated solutions. It was shown that the investigated concentration dependences (including the behavior of biological objects) are non-linear: they have either a stepped character or clearly expressed extremes and are well correlated with each other. A comfortable concentration range of sodium dodecylbenzenesulfonate for daphnia (all daphnia are active within 58 hours of the experiment) was established (0.018–0.037 mM). The correlation and nature of the concentration dependences indicate that at critical concentrations, structural rearrangements occur in sodium dodecylbenzenesulfonate solutions, not only the formation of micelles and pre-micelles, but also structural rearrangements of the solvent (water) itself. Thus, it has been experimentally shown that the change in the structure of water during interaction with pollutants can significantly affect both the physicochemical properties of aqueous solutions and the behavior of aquatic biological objects.

Effect of anions and cations on the self-assembly of ionic liquid surfactants in aqueous solution

Ionic liquid surfactants have shown increasing promise for substituting the traditional amphiphiles due to their flexible tunability and superior physicochemical properties. However, the effect of cationic structure and anion type on the surface properties of ionic liquid surfactants remains unclear. Herein, four ionic liquid surfactants [C12mim][BF4], [PyC12][Br], [C12mim][Br] and [PyC12][BF4] with the same alkyl side chain length were designed and synthesized. Their surface properties, such as micelle-free energy (ΔGmθ), surface tension reduction efficiency (ПCMC), and adsorption efficiency (pC20), and the influence of the type and structure of the anion and cation on their micellar physicochemical properties in aqueous solution were discussed according to the data. The proposed approach demonstrates that the critical micelle concentration (CMC) is determined by combining electrostatic and hydrophobic effects. When the anion is BF4−, the ionic liquid has a lower CMC, and BF4− has a superior hydrophobic effect, which allows the ionic liquid to form micelles more easily. In addition, the ionic liquid of tetrafluoroborate has higher interfacial activity (larger pC20) at the same temperature and its aqueous solution has lower surface tension, making it a more desirable surfactant. All four types of ionic liquids have negative values of ΔGmθ, implying that micelle formation is a spontaneous process. The surface activity of imidazolium- and pyridinium-based ionic liquids was slightly different from the critical micelle concentration under the same anion and carbon chain length. Imidazole and pyridine have highly similar hydrophobic and electrostatic effects, and the cation may not be the most critical factor affecting the surface properties.

Micelle Formation of Dodecanoic Acid with Alkali Metal Counterions.

Alkali series with different atomic numbers affect the physicochemical properties of aqueous solutions. The micellar properties of aqueous solutions of dodecanoate as surfactants were measured by changing the counterions (C12-Na, C12-K, C12-Rb, and C12-Cs). A plot of Krafft temperature vs. alkali metal atomic number showed a downward convex curve, with its minimum temperature (20°C) in the C12-K system. By contrast, a plot of the critical micelle concentration (CMC) vs. alkali metal atomic number exhibited an upward convex curve with the maximum CMC (25.6 mmol L-1) at C12-K. Furthermore, the minimum surface tension (γ min ) of the solution at the CMC increased with increasing atomic number (C12-Na ≈ C12-K < C12-Rb < C12-Cs). The size of the dodecanoate micelles decreased with increasing atomic number. The ionization degree of the micelles also increased with increasing atomic number of the alkali metal. Small-angle X-ray scattering (SAXS) measurements revealed that alkali dodecanoate micelles formed spherical to ellipsoidal structures. In addition, micelles from the shell region showed large electrostatic repulsion, judging from the shape of the spectrum in the higher Q -1 region. From the measurement results of the solubilization of naphthalene into the micelles, the size of the micelles corresponded to the maximum solubilization quantity of naphthalene.

Effects of different solutes on the physical chemical properties of aqueous solutions via rearrangement of hydrogen bonds in water

The Attenuated Total Reflection – Fourier Transform Infrared (ATR-FTIR) spectra of the OH-stretch band in aqueous solutions of inorganic salts and organic materials; Na2SO4, NaCl, NaClO4, NaSCN, trimethylamine N-oxide, urea, poly(ethylene glycol), polyvinylpyrrolidone, and copolymer of ethylene glycol and propylene glycol (Ucon) were studied at various concentrations. The decomposition of the band into four Gaussian components peaking at 3080, 3230, 3400, and 3550 cm−1 fits every compound examined here with essentially flat residuals. These components were viewed as representing four different subpopulations of water with different H-bond arrangements. The experimentally estimated relative contributions of these components depend on solute type and concentration, and correlate strongly with previously reported experimentally measured solvent features of water such as solvent dipolarity/polarizability, π*, solvent H-bond donor acidity, α, and solvent H-bond acceptor basicity, β. We suggest that water includes an ensemble of four different subpopulations of molecules with various hydrogen bond strengths, geometry, and bond defects depending on the solute. This assumption is obviously oversimplified, but for the wide range of solutes examined here we find that a given solute changes the relative amounts of these subpopulations and hence the above solvent features of water. The solvent features, π* and α, in particular, describe a variety of physicochemical properties, such as water activity, osmotic coefficient, relative viscosity, permittivity, and surface tension, of aqueous solutions of various compounds. It follows therefore that all these physicochemical properties of aqueous solutions are determined by the relative amounts of the above subpopulations of water molecules.

Equilibrium States in Aqueous Solutions of Some Ionic Liquids

Abstract—Physicochemical properties of aqueous solutions of a number of proton ionic liquids (electrical conductivity, dissociation parameters, pH, and concentration functions) are determined using specially designed equipment and the techniques of computer resistometry. The correlations between the physicochemical properties of water–organic mixtures and a possible structure of the organic phase are established.

Ecological Cutting Fluids.

This study deals with metalworking fluids (MWFs). According to DIN 51385, depending on their base, the fluids are divided into oil and water fluids. The oil bases include, among others, mineral, synthetic, vegetable and paraffin oils. This division does not comprise surfactant solutions which can be successfully used in metalworking. Due to the fact that this type of fluid was not qualified, a new type of lubricant based on the aqueous solutions of surfactants has been proposed. Two new notions have been introduced: surfactant working fluids (SWFs) for working fluids and surfactant lubricants (SLs) for all kinds of lubricants as a broader term. The effect of the physicochemical properties of aqueous solutions of sodium lauroyl sarcosinate (SLS), also known as sodium N-dodecanoyl-N-methyl glycinate, on tribological properties determined using a four-ball machine (Tester T-02) (Łukasiewicz Research Network—The Institute for Sustainable Technologies, Radom, Poland) was analyzed. On the basis of aqueous SLS solutions a composition of working fluids was developed and their functional properties were verified by means of tribological and stand tests as well as during operation. The test results obtained clearly indicate that functional properties of 2% solutions of sodium lauroyl sarcosinate with a foam inhibitor (0.05%) and a biocide (0.1%) are comparable to those of a quality commercial hydraulic fluid.

The origins of binding specificity of a lanthanide ion binding peptide

Lanthanide ions (Ln3+) show similar physicochemical properties in aqueous solutions, wherein they exist as + 3 cations and exhibit ionic radii differences of less than 0.26 Å. A flexible linear peptide lanthanide binding tag (LBT), which recognizes a series of 15 Ln3+, shows an interesting characteristic in binding specificity, i.e., binding affinity biphasically changes with an increase in the atomic number, and shows a greater than 60-fold affinity difference between the highest and lowest values. Herein, by combining experimental and computational investigations, we gain deep insight into the reaction mechanism underlying the specificity of LBT3, an LBT mutant, toward Ln3+. Our results clearly show that LBT3-Ln3+ binding can be divided into three, and the large affinity difference is based on the ability of Ln3+ in a complex to be directly coordinated with a water molecule. When the LBT3 recognizes a Ln3+ with a larger ionic radius (La3+ to Sm3+), a water molecule can interact with Ln3+ directly. This extra water molecule infiltrates the complex and induces dissociation of the Asn5 sidechain (one of the coordinates) from Ln3+, resulting in a destabilizing complex and low affinity. Conversely, with recognition of smaller Ln3+ (Sm3+ to Yb3+), the LBT3 completely surrounds the ions and constructs a stable high affinity complex. Moreover, when the LBT3 recognizes the smallest Ln3+, namely Lu3+, although it completely surrounds Lu3+, an entropically unfavorable phenomenon specifically occurs, resulting in lower affinity than that of Yb3+. Our findings will be useful for the design of molecules that enable the distinction of sub-angstrom size differences.

Effect of Mechanical Shaking on the Physicochemical Properties of Aqueous Solutions.

Long-lived luminescence in the blue region was found to occur in deionized water saturated with atmospheric gases following mechanical shaking. Luminescence intensity decreased exponentially after the cessation of stress. During vigorous mechanical shaking, we observed gas bubbles in solution, and the liquid–gas interface area increased noticeably. At the same time, the concentration of molecular oxygen decreased, which could not be attributed to the water warming up with exposure to mechanical stress. However, deaerated water rapidly became saturated with gases following mechanical stress. The recommendation that cell culture media should be mixed after they are removed from the fridge in order to allow saturation with oxygen is probably misleading. It was shown that gases existed in water both in the form of individual molecules and nanobubbles. Mechanical stress did not influence the number or size of nanobubbles. While gas nanobubbles were absent in freshly prepared deaerated water, they appeared following exposure to mechanical stress. In addition, in mechanically treated gas-saturated water, there was seemingly an equilibrium shift towards the decomposition of carbonic acid to water and carbon dioxide. At the same time, the pH of water tended to increase immediately after mechanical stress. It was demonstrated that reactive oxygen species (ROS) form in gas-saturated water under mechanical stress (30 Hz, amplitude of 5 mm). The relative generation rate of hydrogen peroxide and of the hydroxyl radical was 1 nM/min and 0.5 nM/min, respectively. It was found that with an increase in the frequency of mechanical action (f), the rate of ROS generation increased in proportion to f 2. The major pathways for hydrogen peroxide generation are probably associated with the formation of singlet oxygen and its further reduction, and the alternative pathway is the formation of hydrogen peroxide as a result of hydroxyl radical recombination.

Experimental and Theoretical Insights to Physicochemical Properties of Aqueous Solutions of 1, 2-Ethanediol and 1, 2, 3-Propanetriol at Different Temperatures

Water is designated as “Universal solvent” due to its physical and chemical attributes. Water becomes attracted to different types of molecules due to the polar arrangement of oxygen and hydrogen atoms having partial negative and positive charges. The density (ρ), ultrasonic velocity (U), viscosity (η) and refractive index (nD) of the aqueous solutions of 1, 2-ethanediol / 1, 2, 3-propanetriol have been determined at three different temperatures. Derived properties such molar volume (V), isentropic compressibility (ᵝs), acoustic impedance (Z) and free length (Lf) have been calculated using density, ultrasonic velocity and refractive index values at the measured temperatures. To evaluate various, inter and intra-molecular associations present in the systems, the excess properties (VE, ᵝsE, ZE, Lf E, ηE and ∆nD) are estimated. The excess values obtained experimentally have been fitted to the Redlich -Kister polynomial equation. Multiple linear regression and mixing rules have been adopted to calculate the viscosity and refractive index for the aqueous solutions at 298.15, 308.15 and 318.15K.

The Dependence of Spontaneous Charge Generation in Water on its Flow Rate in a Flow-Based Analytical System

Highly sensitive biosensor systems are particularly sensitive to the charge state of an analyte. This charge state can have either a positive (for instance, in case of increasing the efficiency of fishing of low-abundant proteins) or negative effect (for instance, in case of the appearance of charge jumps upon the injection of analyte solution into a measuring cell, what can cause undesirable parasitic signals). Previously, it was demonstrated that upon the pumping of analyte solution through polymeric communications of biosensors with a peristaltic pump at a low (~1 mL/min) flow rate, an accumulation of charge, transferred by the liquid drops from the feeding system into the measuring cell, is observed. At this point, the time dependence of charge accumulation has a linear-stepwise form. In the present study, the influence of the flow rate of water on the parameters of the time dependence of the accumulation of charge in such a system—including the influence on the stepwise charge accumulation—has been investigated. The measurements have been performed with a highly sensitive electrometer sensor at 38 °C, which corresponds to a pathological state of a human body. It has been found that a linear-stepwise time dependence of charge accumulation is observed in a wide range of water flow rates (V= 0.9 to 7.2 mL/min). At that point, upon increasing the flow rate with the transition from the drop-by-drop mode of water supply (0.9 mL/min) to the jet flow (7.2 mL/min), an increase in the absolute value of accumulated charge is observed, but the magnitude of the charge jumps does not change significantly. Thus, the amount of charge accumulated in the cell ambiguously depends on the water flow rate—i.e., this dependence can be non-linear. Accounting for the discovered phenomenon is important in the development of new, more accurate models describing physicochemical properties of aqueous solutions and hemodynamics. This effect should also be taken into account in the development of highly sensitive diagnostic systems intended for the detection of single biomarkers of pathologies in humans and crops, as well as in other living systems. In low-concentration systems, the occurrence of a charge can become a significant factor affecting the efficiency of detection of biomolecules and the reliability of the data obtained. The detection of biomolecules present in the solution at low concentrations is in high demand in medical diagnostics for the revelation of biomarkers at the early asymptomatic stage of various diseases, including aggressive forms of cancer.

Solid-State Synthesis of Water-Soluble Chitosan-g-Hydroxyethyl Cellulose Copolymers.

Graft copolymers of chitosan with cellulose ether have been obtained by the solid-state reactive mixing of chitin, sodium hydroxide and hydroxyethyl cellulose under shear deformation in a pilot twin-screw extruder. The structure and composition of the products were determined by elemental analysis and IR spectroscopy. The physicochemical properties of aqueous solutions of copolymers were studied as a function of the composition, and were correlated to the mechanical characteristics of the resulting films to assess the performance of new copolymers as coating materials, non-woven fibrous materials or emulsifiers for interface stabilization during the microparticle fabrication process.

Sharp changes in properties of aqueous sodium chloride solution at “critical” concentrations of the salt

It was shown that some physicochemical properties of aqueous solutions of sodium chloride (contact angle, surface tension, pH, and others) demonstrate a nonlinear dependence on the salt concentration. The maxima or minima in the graphs are most frequently observed near the concentrations of NaCl we call "critical": 3, 5, 7, 12, 17, and 21 g/L. Similar nonlinear peak-shape dependence of the property on salinity was observed in more complex systems containing NaCl (sedimentation rate of mineral suspensions, viscosity of clay pastes, rate of a redox reaction of periodate with amine). We hypothesized that the said critical points of salt concentration may exist when the clusters of water molecules rearrange themselves upon the addition of a definite quantity of salt. The obtained results were used in the discussion of avalanche sedimentation of suspended particulate matter and colloids transported by rivers through the river mixing zones (estuary, delta) and the critical salinity under which the river biota gives place to marine biota.

About changes in the physicochemical properties of aqueous solutions used as a liquid electrolyte cathode

The gas discharge between liquid electrolyte cathode and metal anode was experimentally investigated. Aqueous solutions of sodium chloride, potassium chloride, sodium sulfate, sodium hydroxide, and potassium hydroxide were used as the electrolyte cathode. Decrease aqueous solution was compensated by adding distilled water (solvent) in a continuous mode in the discharge burning process. It was found that, despite the significant dilution with a solvent, the specific electrical conductivity of aqueous solutions of alkali metal salts and alkalis varies slightly.

Syntheses, surface activities and aggregation morphologies of a series of novel itaconic acid based asymmetrical gemini surfactants

A series of novel itaconic acid based asymmetrical gemini surfactants containing two long alkyl chains, two selfsame nonionic groups along with an anionic moieties covalently attached by an itaconic acid spacer group (polyoxyethylene laurinol ether sodium sulfoitaconate: PLSS-n) have been synthesized through esterification and sulfonation reaction using itaconic anhydride (IAn) and polyoxyethylene alkyl ethers. The chemical structures of the PLSS-n homologs were confirmed through FT-IR, 1H NMR spectra and elemental analysis (EA). And their physico-chemical properties in aqueous solutions were further investigated. The PLSS-n species have lower equilibrium surface tension (γCMC) and critical micelle concentration (CMC), lower Krafft points (Tk), good wettability and foaming properties. The γCMC and CMC values of PLSS-n are decreased with the increase of the temperature. The PLSS-n homologs exhibit high surface activities even at lower temperature. The PLSS-n homologs all exhibit smaller values of areas per molecule (Amin) and larger values of maximum excess surface concentration (Γmax). The rheological behaviors of the PLSS-n solutions show that only PLSS-3 shows shear thinning feature with the increasement of shear rate. The average diameters of the PLSS-n aggregations were studied by Dynamic light scattering (DLS) at 25 °C. Cryogenic transmission electron microscopy (cryo-TEM) results of the PLSS-n indicate that these gemini surfactants can form various micellar behaviors, which are affected by different combined factors. The Small angle X-ray scattering (SAXS) measurements provide evidence of the anisotropic lamellar structure.

Self-Organization and Physicochemical Properties of Aqueous Solutions of the Sodium Salt of Azosulphonate Calix[4]arene

Self-Organization and Physicochemical Properties of Aqueous Solutions of the Sodium Salt of Azosulphonate Calix[4]arene

The Effect of Polar Head and Chain Length on the Physicochemical Properties of Micellization and Adsorption of Amino Alcohol‐Based Surfactants

In this work, we have synthesized a series of quaternary ammonium from amino alcohols and n‐bromoalkanes. The compounds are referred to as CnEtOH, CnPrOH, and CniPrOH (where n = 12 and 14 carbons, EtOH = ethanol, PrOH = propanol, iPrOH = iso‐propanol). Their structures were checked using the usual spectroscopic methods [1H, 13C nuclear magnetic resonance (NMR) and infrared (IR)]. Their physicochemical properties in aqueous solution were studied using conductivity, surface tension, and ultra violet (UV)–visible absorption spectroscopy measurements. This study was conducted to show the effect of the linear hydrophobic chain and the location of the OH polar group with respect to the N+ quaternary ammonium on the physicochemical properties of the surfactants. The comparison between the physicochemical properties of the surfactants studied shows a distinct effect of the position of the OH group on the critical micelle concentration (CMC), the ionization degree (α), the area occupied at the interface (Amin), the free energy of adsorption (), and the free energy of micellization (). The intermolecular interaction between the synthetic surfactants and the methyl orange (OM) dye is related to the degree of hydration of the micelle, proven by the hypsochromic displacement of OM wavelength (λmax) and ionization (α) of the micelles. The CMC, the degree of ionization, and the degree of hydration of the micelle follow the same trend.

Modulation of physical properties of microfluidized whey protein fibrils with chitosan

There is an increasing market for food and beverage products enriched in proteins and dietary fibers due to their potential health benefits. In this study, the effect of heating (85 °C, 20 min), microfluidization (20,000 psi), and pH (2 to 6.5) on the physicochemical properties of aqueous solutions containing mixtures of whey protein fibrils (7.5%; WPF) and chitosan (0.5%; CN) were examined. Heating of the mixed systems increased their turbidity and apparent viscosity, which was attributed to the formation of protein-rich particles. Interestingly, heating the mixed systems and then applying microfluidization led to phase separation and a lower apparent viscosity, which was attributed to high-pressure disruption of the whey protein fibrils. The pH of the systems significantly influenced their appearance, turbidity, particle size, and apparent viscosity, with high turbidity and viscosity, and large particle size occurring from pH 3.5 to 5.5. These effects were attributed to protein aggregation close to its isoelectric point (pH 5) coupled with electrostatic attraction between anionic groups on the whey protein and cationic groups on the chitosan. The addition of chitosan increased the net isoelectric point from pH 5 for pure whey protein to pH 6 for the mixed system. Overall, this study showed that the appearance and rheological properties of protein-dietary fiber mixtures could be manipulated by heating, microfluidization, and pH adjustment. This information may be useful for designing protein and fiber enriched food and beverage products with desirable physical and sensory properties.

Physicochemical Properties of Aqueous Solutions of Binary Mixtures of Lignin Derivatives and Sodium Dodecyl Sulfate

Physicochemical properties of aqueous solutions of binary mixtures of lignosulfonates and sodium dodecyl sulfate were studied. Introduction of sodium dodecyl sulfate into solutions of high-molecular-mass lignosulfonates at certain ratios causes macrophase separation of the systems with the formation of loose precipitates. A synergistic effect of a decrease in the surface tension is observed in the mixed solutions. This effect increases with increasing lignosulfonate molecular mass and temperature. The revealed relationships are caused by hydrophobic interactions of hydrocarbon radicals of sodium dodecyl sulfate with hydrophobic segments of lignosulfonate polymer chains with the formation of micellar associates. Aqueous solutions of binary mixtures of lignosulfonates (сLS ≥ 0.2 g dm–3) and sodium dodecyl sulfate (сDSNa ≥ 0.08 g dm–3) can be recommended for use as surfactant formulations for high-temperature autoclave leaching of polymetal ores.