Value In Pure Water Research Articles

Evaluation of Groundwater Quality for Drinking Purpose using Different Water Quality Indices in Parts of Gautam Budh Nagar District, India

Water Quality Index (WQI) is a mathematical value for quality of water, which includes the concentration of a number of constituents present in it. Chemical and biological measures of water quality are used to represent water quality index. Measured value of the selected parameters, ideal concentration of that parameter in pure water and standard value given by different quality control organizations are used to determine this number. In the present study, three indexing methods; Weighted Arithmetic Water Quality Index (WAWQI), Groundwater Quality Index (GWQI) and Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) were used to calculate water quality index of groundwater. A hydrochemical analysis of 22 groundwater samples was conducted to evaluate the quality of groundwater for drinking purpose. Ten hydrochemical parameters were selected for computing WQIs of groundwater samples and BIS standards were used for standardization. Analytical results show that 100 % of samples have magnesium and total hardness above the acceptable limit of BIS (10500, 2012). The mean concentration of nitrate was found 196.96 ± 9.3.18 mg/L. Spatial distribution of various parameters shows that south-east part of study area has contaminated groundwater. The results of water quality index shows that drinking water quality of 82 % (WAWQI), 95 % (GWQI) and 77 % (CCME WQI) of groundwater samples were poor to unsuitable type. Water quality index map also reveals that groundwater of village Badhpura, Dhoom Manikpur, Dairy Maccha, Khera Dharampura, Bisrakh road, Duryai and Dujana of district Gautam Budh Nagar of India, was not fit for human consumption.

Determination of the Critical Micelle Concentration of Imidazolium Ionic Liquids in Aqueous Hydrogen Peroxide.

The critical micelle concentrations (CMCs) of several imidazolium-based ionic liquids (ILs) in aqueous H2O2 (50 wt % in H2O) were determined by tensiometry, conductometry, and the rate of catalytic epoxidation of cis-cyclooctene. CMC values in aqueous H2O2 were significantly lower compared to values in pure water. In both H2O2 solution and water, the CMC of all ILs decreases with an increasing alkyl chain length and increases with a rising temperature. The degree of micelle ionization of 1-methyl-3-octylimidazolium tetrafluoroborate ([OMIM][BF4]) was calculated by conductometry in a temperature range of 22-70 °C.

Experimental Vapor-Pressures and Derived Thermodynamic Properties of Geothermal Fluids from Baden-Baden Geothermal Field (Southeastern Germany)

Background: In the present study, vapor-pressures of three geothermal fluids from Baden-Baden geothermal field (Kirchenstollen, Friedrichstollen, and Murquelle, southeastern region of Germany) were measured over the temperature range of 274–413 K. The combined expanded uncertainty of the temperature and vapor-pressure measurements at 95% confidence level with a coverage factor of k = 2 were estimated to be 0.01 K and 1–3 Pa at low and 10–30 Pa at high temperatures, respectively. The measured values of vapor-pressure were used to calculate other crucial derived thermodynamic properties of these geothermal fluid samples, such as enthalpy and entropy of vaporization and the heat capacity. Methods: The measurements were performed using two different methods and experimental apparatus: (1) absolute and differential static method which was used at low temperatures ranging from 274.15 to 323.15 K; and (2) absolute static method which was used at elevated temperatures ranging from 323.15 to 413.15 K. Results: The data obtained from the measurements were utilized to formulate Antoine and Wagner-type vapor-pressure equations. The effects of various ion species on the vapor-pressure of the geothermal fluids were studied. In addition, the measured vapor-pressure values were utilized to develop Riedel’s type correlation model for natural geothermal fluids in order to estimate the contributions of the various ion species to the total experimentally-observed values of vapor-pressure. It was observed that the anions were increasing the vapor-pressure, while the cations were decreasing it, with the rates (magnitudes) of these increases and decreases being different and strongly dependent on the chemical nature of the ion species involved. Using the measured vapor-pressure data, the other key thermodynamic properties, such as enthalpy and entropy of vaporization and the heat capacity) of the geothermal fluid samples were calculated. Conclusions: The measured vapor-pressure values of the geothermal fluids were higher than the pure water values (IAPWS standard data) by 5.5%–25.4% for Kirchenstollen, 3.0%–11.4% for Friedrichstollen, and 5.3%–14.8% for Murquelle, depending on the temperature. The largest deviations (up to 11%–25%) were observed at low temperatures (approximately 277 K), while at high temperatures, the deviations were within the range of 3.0% to 5.5%. This could be attributed to the effects of soluble gas in the geothermal fluids. The soluble gases were observed to be strongly affecting the measured vapor-pressure of the geothermal fluids. The experimentally observed vapor-pressure was the result of the competition between the opposite effects of the anion and cation contributions.

Cerebrospinal fluid T1 value phantom reproduction at scan room temperature.

The T1 value of pure water, which is often used as a phantom to simulate cerebrospinal fluid, is significantly different from that of in‐vivo cerebrospinal fluid. The purpose of this study was to develop a phantom with a T1 value equivalent to that of in‐vivo cerebrospinal fluid under examination room temperature (23°C–25°C). In this study, 1.5 and 3.0 T magnetic resonance imaging scanners were used. We examined the signal intensity change in relation to pure water temperature, the T1 values of acetone‐diluted solutions (0–100 v/v%, in 10 steps), and the correlation coefficients obtained from volunteers and the prepared phantoms. The T1 value was close to the value reported in the literature for cerebrospinal fluid when the acetone‐diluted solution was 70 v/v% or higher at scan room temperature. The value at that time was 3532.81–4704.57 ms at 1.5 T and it ranged from 4052.41 to 5701.61 ms at 3.0 T. The highest correlation with the values obtained from the volunteers was r = 0.993 with pure acetone at 1.5 T and r = 0.991 with acetone 90 v/v% at 3.0 T. The relative error of the best phantom‐volunteer match was 32.61 (%) ± 6.71 at 1.5 T and 46.67 (%) ± 4.31 at 3.0 T. The T1 value measured by the null point method did not detect a significant difference between in vivo CSF and acetone 100 v/v% at 1.5 T and acetone 90 v/v% at 3.0 T. The T1 value of cerebrospinal fluid in the living body at scan room temperature was reproduced with acetone. The optimum concentration of acetone for cerebrospinal‐fluid reproduction was pure acetone at 1.5 T and 90 v/v% at 3.0 T.

Thermodynamic study of the solubility of ethylparaben in acetonitrile + water cosolvent mixtures at different temperatures

The thermodynamic analysis of the solubility of ethylparaben (1) in acetonitrile (1) + water (2) cosolvent mixtures at 9 temperatures, 10 cosolvent mixtures and the 2 pure solvents, water and acetonitrile, is reported herein. The solution thermodynamic functions were calculated from the experimental solubility data, using the van't Hoff and Gibbs equations, following the approach proposed by Krug et al. Thus, the solubility of ethylparaben is thermo-dependent, reaching its minimum value in pure water at 278.15 K and its maximum value in the cosolvent mixture w1 = 0.90 at 318.18 K. The enthalpy of solution is positive in all cases, which is an indication of the endothermic process, with an enthalpy-driven mixing process in mixtures rich in water and by entropy mixtures rich in acetonitrile.

Detection of P. polymyxa biofilm, dairy biofouling and CIP-cleaning agents using low-field NMR

The accumulation of unwanted deposits in food-processing equipment may cause significant production downtime, add to expenses for cleaning agents and wastewater disposal, as well as food contamination. Nuclear magnetic resonance (NMR) is considered as a promising non-invasive tool for the monitoring of processes in food industry. In this work, two deposit models and cleaning agents are investigated by low-field 1H NMR: (1) Paenibacillus polymyxa biofilm, (2) dairy biofouling and (3) clean-in-place (CIP) cleaning agents. The transverse relaxation times T2 obtained by inverse Laplace transform as well as diffusion coefficients DS of the samples are studied. The obtained results reveal that low-field NMR can be used for the detection and identification of selected deposit models and CIP-cleaning agents. Transverse relaxation times T2 demonstrate characteristic relaxation behavior of flexible tubing, differently structured deposits, and liquid phases. Moreover, with increasing biofouling thickness (up to 406.2 mg/cm2), transverse relaxation times T2 shift toward slower relaxation rates up to T2 111.9 ms. In addition, significant differences in the diffusion behavior of water are noted in each sample group of the deposit models and CIP-cleaning agents. The diffusion coefficient of water in dairy biofouling and in microbial biofilm matrix corresponds to approximately 65% and 75% of the value in pure water, respectively. In addition to the NMR results, the biofilm and biofouling identification is validated through microbiological methods and by microscope images.

Reaction between Zinc and Hydrochloric Acid in Solutions Containing Alkyltrimethylammonium Bromide CnTAB (n = 8, 10, and 12) Cationic Surfactants: Influence of Surfactant Chain Length

AbstractThe influence of CnTAB cationic surfactant chain length (n = 8, 10, and 12) on the reaction rate of zinc powder and 0.1 M HCl hydrochloric acid in aqueous solutions was determined at room temperature. Solutions of single surfactants consisting of dodecyl, decyl, and octyl‐trimethyl‐ammonium bromide surfactants CnTAB were prepared at room temperature. From the surface tension and conductivity measurements, the critical micelle concentration (CMC) values of the three surfactants were obtained in the presence and absence of the acid. No significant change was observed for CMC values in pure water and in 0.01 M HCl. Adsorption of CnTAB surfactants onto 1% wt./vol zinc (in powder form), using surface tension measurements, was then investigated. The adsorption tendency of CnTAB surfactants onto zinc powder followed the order: C8TAB > C10TAB > C12TAB. The role of surfactants in the reaction rate between zinc powder and 0.1 M M HCl was then investigated using conductivity measurements. A significant difference in the reaction rate was found depending on the surfactant chain length. Reaction times of 3830, 4963, 14,172, and 20,053 s were found for the zinc reaction with (0.1 M HCl), (0.1 M HCl + 40 mM C8TAB), (0.1 M HCl + 40 mM C10TAB), and (0.1 M HCl + 40 mM C12TAB), respectively, suggesting a significant dependency of the reaction rate on the CnTAB chain length. Finally, some corrosion parameters such as the corrosion rate, corrosion inhibition efficiency, and their dependency on CnTAB chain length were presented and discussed.

Interactions of Some Hofmeister Cations with Sodium Dodecyl Sulfate in Aqueous Solution

AbstractIn this work, we have investigated the influence of some alkali metal ions on the Krafft temperature (TK) and critical micelle concentration (CMC) of a classical ionic surfactant, sodium dodecyl sulfate (SDS), over a wide range of temperature. The alkali metal cations such as Li+, Na+, Cs+, and K+ are found to affect the solubility and hence the TK of the surfactant. It was observed that kosmotropic Li+ lowers the TK of the surfactant. Due to the common ion effect, the solubility of SDS decreases in the presence of Na+, resulting in an increase in the TK. On the other hand, chaotropic K+ and Cs+, capable of forming contact ion pairs with the chaotropic dodecyl sulfate ion, lower the solubility and hence elevate the TK. In terms of decreasing the TK, the ions follow the trend: Li+ > Na+ > Cs+ > K+ except for 0.0025 M CsCl. The added cations screen the charge of the micelle surface and facilitate closer packing of the surfactant with a consequent decrease in the CMC. In terms of the effectiveness in lowering the CMC, the ions follow the order: Cs+ > K+ > Na+ > Li+. In the presence of added electrolytes, the γCMC values are found to be lower than the corresponding values in pure water. The thermodynamic parameters (Gibbs free energy, enthalpy, and entropy changes) of micellization were calculated to gain insights into the mechanism of the process.

High performance graphene oxide nanofiltration membrane prepared by electrospraying for wastewater purification

A high performance graphene oxide nanofiltration membrane (GO NFM) was prepared using the electrospraying technique instead of the traditional vacuum filtration method, which is a facial and scalable method to prepare GO NFMs with diameter of 100 mm. The permeate performance of this novel nanofiltration membrane was evaluated using a dead end filtration device, which gave us a high flux value for pure water (11.13–20.23 L m−2 h−1 bar−1) even under an extremely low external pressure (1.0 bar). The GO(120) NFM demonstrated high organic dyes rejection rate (98.88%, 98.97%, 100%, and 99.99%, for BF, MB, MO, and EB, respectively). The rejection mechanism for charged dyes was discussed and the results revealed that physical size sieving and electrostatic interaction dominated the rejection mechanism. The rejections rate of GO NFMs for the Na2SO4, NaCl, MgSO4, and MgCl2 were 63.13%, 27.86%, 41.82%, and 15.00%, respectively, based on the mechanism of Donnan exclusion theory and steric hindrance effect. Furthermore, the GO NFM shows high flux recovery ratio (FRR) values (89.58% and 95.54% for SA and HA), suggesting that the GO NFM is easier to be recovered by DI water washing due to the smooth and hydrophilic surface.

A modified RP-HPLC method for the determination of the pKa values of synthesized β-hydroxy-β-arylalkanoic acids

The pKa values of twelve ?-hydroxy-?-arylalkanoic acids and ibuprofen were determined using a modified RP-HPLC method. The stationary phase was octadecyl modified (C-18) silica gel, and the mobile phases were mixtures of methanol and one of ten different buffers (60:40 volume ratio). The mean retention time of each compound was plotted against the pH of each of the ten used mobile phases. The inflection point of the obtained sigmoidal curve represents the s w pKa of a compound. Using s w pKa in previously established equations for the specific methanol/buffer mixture, the w w pKa values (in pure water) were calculated. The obtained w w pKa values for the synthesized compounds were in a range from 3.40 to 3.74, and the w w pKa for ibuprofen was 4.27. The Predicted pKa values for this type of compounds in the MarvinSketch 5.11.5. Program were in poor correlation with the experimental results, while in ACD/ /I-Labs pKa values were calculated as a wide range.

Interactions of Cationic, Anionic and Nonionic Surfactants with Cresol Red Dye in Aqueous Solutions: Conductometric, Tensiometric, and Spectroscopic Studies

Abstract The interaction of cresol red (CR) with cetylpyridinium bromide (CPB), sodium dodecyl sulphate (SDS), and Triton X-100 (TX-100) was studied in aqueous solutions employing conductometric, tensiometric, and spectroscopic methods. Various micellar and interfacial parameters were calculated in absence and in presence of CR. The interactions suggest the formation of a CR-CPB adduct, an association of CR with the micelle of TX-100 while no adduct is formed between CR and SDS. Appreciably low critical micelle concentration, CMC value of TX-100 compared with those of CPB and SDS in pure water and drastic reduction of CMC of CPB (about one-twelfth of its value in pure water) than SDS and TX-100 in the presence of CR were observed. Higher negative values of Gibbs free energy of micellization, ΔG m 0, for all the three surfactants indicate that micellization process is spontaneous. The values of maximum surface excess concentration, Γ max, and minimum area per molecule, A min, suggest that in the presence of CR, the air-solution interface is closely packed and the orientation of surfactant molecules is almost perpendicular to the surface. UV-visible spectra suggest the formation of ion-pair complex between the dye CR and the monomers of CPB in the pre-micellar region, while above the CMC a breaking up of the ion-pair complex takes place and the dye is solubilized in the micelles of CPB. In the case of SDS the absorption spectra indicate weak interaction between CR and SDS molecules formation of H-bonding, short range dispersive forces, and hydrophobic interactions between CR and TX-100 molecules in the solution.

Impact of trehalose on the activity of sodium and potassium chloride in aqueous solutions: Why trehalose is worth its salt

Trehalose is revered for its multiple unique impacts on solution properties, including the ability to modulate the salty and bitter tastes of sodium and potassium salts. However, the molecular mechanisms underlying trehalose’s effect on taste perception are unknown. Here we focus on the physico-chemical effect of trehalose to alter the activity of monovalent salts in aqueous solution. Using a modified isopiestic methodology that relies on contemporary vapor pressure osmometry, we elucidate how trehalose modifies the thermodynamic chemical activity of sodium and potassium chloride, as well as the effect of the salts on the sugar's activity. We find that trehalose has a specific impact on potassium chloride that is unlike that of other sugars or polyols. Remarkably, especially at low salt concentrations, trehalose considerably elevates the activity (or chemical potential) of KCl, raising the salt activity coefficient as high as ∼1.5 its value in the absence of the sugar. Moreover, in contrast to their action on other known carbohydrates, both KCl and NaCl act as salting-out agents towards trehalose, as seen in the elevated activity coefficient compared with its value in pure water (up to ∼1.5 higher at low sugar and salt concentrations). We discuss the possible relevance of our findings to the mechanism of trehalose taste perception modification, and point to necessary future directed sensory experiments needed to resolve the possible link between our findings and the emerging biochemical or physiological mechanisms involved.

Viscometry of polyelectrolyte solutions: Star-like versus linear poly[[2-(methacryloyloxy)ethyl] trimethylammonium iodide] and specific salt effects

The intrinsic viscosities, [η], of the 3-arm star polyelectrolyte in pure water are for a given molar mass considerably lower than for the linear product because of the higher monomer concentration and charge density in isolated coils. These effects are much more pronounced than in the case of uncharged macromolecules. Extra salt (NaCl, NaI, CaCl2) reduces the solution viscosities of the 3-arm star polymer less than of the linear product. The transition of [η] from the value in pure water to the minimum saturation value at high salt concentrations follows a Boltzmann sigmoid. In saline solvents the changes of the viscosities with rising polymer concentration depend strongly on the chemical nature of the salt and on the molecular architecture of the solute. The present findings demonstrate the necessity to account for thermodynamic interactions between all components of the mixture, in addition to the usual electrostatic considerations. These considerations should turn out helpful for a better understanding of salt induced topological transitions of charged biopolymers.

Help from a Hindrance: Using Astigmatism in Round Capillaries To Study Contact Angles and Wetting Layers.

Round glass capillaries are a basic tool in soft-matter science, but often are shunned due to the astigmatism they introduce in micrographs. Here, we show how refraction in a capillary can be a help instead of a hindrance to obtain precise and sensitive information on two important interfacial properties: the contact angle of two immiscible fluids and the presence of thin films on the capillary wall. Understanding optical cusps due to refraction allows direct mesurement of the inner diameter of a capillary at the meniscus, which, with the height of the meniscus cap, determines the contact angle. The meniscus can thus be measured without intrusive additives to enhance visibility, such as dyes or calibrated particles, in uniform, curved, or even tapered capillaries or under demanding conditions not accessible by conventional methods, such as small volumes (μL), high temperatures, or high pressures. We further elicit the conditions for strong internal reflection on the inner capillary wall, involving the wall and fluid refractive indices and the wall thickness, and show how to choose the capillary section to detect thin (submicron) layers on the wall, by the contribution of total internal reflection to the cusps. As examples, we report the following: (i) CO2-water or -brine contact angles at glass interfaces, measured at temperatures and pressures up to 200 °C and 600 bar, revealing an effect apparently so far unreported-the decrease in the water-wet character of glass, due to dissolved salts in brine, is strongly reduced at high temperatures, where contact angles converge toward the values in pure water; (ii) A tenuous gas hydrate layer growing from the water-guest contact line on glass, invisible in transmission microscopy but prominent in the cusps due to total internal reflection.

Concentration effects on turbulence in dilute polymer solutions far from walls.

We report measurements of the modification of turbulence far from any walls by small concentrations of long-chain polymers. We consider a range of statistical properties of the flow, including Eulerian and Lagrangian velocity structure functions, Eulerian acceleration correlation functions, and the relative dispersion of particle pairs. In all cases, we find that the polymer concentration has a strong effect on the extent to which the statistical properties are changed compared to their values in pure water. These effects can be captured by the recently proposed energy flux-balance model (when suitably extended into the time domain for Lagrangian statistics). However, unlike previous measurements, which found that the concentration effect could be completely scaled out, we consistently find that our data collapse onto two different master curves, one for small concentration and one for larger concentration. We suggest that the difference between the two may be related to the onset of interactions among polymer chains, which is likely to be more easily observed at the small Weissenberg numbers we consider here.

Study of dependence between thermal diffusivity and sample concentration measured by means of frequency-resolved thermal lens experiment

This paper describes experimental results of thermal diffusivity measurements performed on different concentrations of aqueous Tartrazine solutions. The measurements are performed using the frequency-resolved thermal lensing technique and the results are compared with the thermal diffusivity value of pure water used as a solvent or host liquid. The results show that at low concentrations, the thermal properties of the solution are roughly equal to those of the water. However, when the concentration is increased, the thermal properties of the solutions diverge from that of the host liquid.

Measurements of the density, speed of sound, viscosity and derived thermodynamic properties of geothermal fluids from south Russia Geothermal Field. Part II

Density, (ρ), speed of sound, (W), and viscosity, (η) of natural geothermal fluids from south Russia Geothermal Fields (Dagestan, Caspian seashore) have been measured over the temperature range from (277–353) K at atmospheric pressure. The measurements were made using the Anton Paar DMA4500 densimeter and Stabinger SVM3000 viscodensimeter for four geothermal fluid samples from the various hot-wells Izberbas (No. 68 and 129), Ternair (No. 27T and No. 38T). A sound-speed analyzer (Anton Paar DSA 5000) was used for simultaneously measurement of the speed of sound and density of the same geothermal fluid samples. The average differences between the measured geothermal fluids densities and viscosities and pure water values (IAPWS formulation) are within (0.1–1.77) % and (0.13–2.1) %, respectively, which are considerably higher than their experimental uncertainties. This differences are caused by the high concentrations of some type of ion species, such as (Na+: 7.7 g/l (#38T); Cl−1:7.7 g/l (#38T); SO4−2: 0.75 g/l (#68); S+: 0.24 g/l (#68); K+:0.15 g/l (# 27T); Ca+2: 0.074 g/l (#27T); B+:0.06 g/l (#38T); and Mg +2: 0.033 g/l (#38T)), in the geothermal fluids, which strongly effect on salt concentration dependence of the measured properties. Measured values of density and speed of sound were used to calculate other derived thermodynamic properties such as adiabatic coefficient of bulk compressibility (βS), coefficient of thermal expansion (αP), thermal pressure coefficient (γV), isothermal coefficient of bulk compressibility (βT), isochoric heat capacity (CV), isobaric heat capacity (CP), enthalpy difference (ΔH), partial pressure derivative of enthalpy (∂H∂P)T, and partial derivatives of internal energy (internal pressure) (∂U∂V)T, of the geothermal fluid samples. Measured values of density, viscosity, and speed of sound were used to develop correlation models for the temperature and ion species concentration dependences, which reproduced the measured values within 0.03% (density), 2.47% (viscosity), and 0.20% (speed of sound). To confirm the accuracy and predictive capability of the developed correlation models for density, speed of sound, and viscosity, we have applied the models to well-studied binary aqueous salt solutions (H2O + NaCl). The prediction of the density and viscosity of aqueous sodium chloride solutions based on the developed models were very close to their experimental uncertainties (within 0.03% for density and 1.56% for viscosity). The measured properties at atmospheric pressure have been used as a reference data for prediction of the high-pressure thermodynamic behavior. The predictive capability of the model has been checked on reliable experimental data for binary aqueous NaCl solutions at high pressures reported by Kestin and Shankland (1984) and Rogers and Pitzer (1982). The prediction for density and viscosity is within 0.03% and 1.57%, respectively.

Dynamic interfacial tension in water/n-pentane system: An experimental study using the oscillating-jet method

The interfacial tension working at an interface created by sudden contact of liquid water with saturated common vapors of n-pentane and water under atmospheric pressure (0.101MPa) was experimentally studied, focusing on the behavior of its relaxation to an equilibrium value in response to the progress of the adsorption of n-pentane molecules onto the interface. The oscillating-jet method was used to measure the dynamic interfacial tension, i.e., the interfacial tension varying with time during a short relaxation period (less than 0.1s) after the creation of the interface. It was observed that during the first ~50ms after the creation of the interface, the tension quasi-exponentially decreased from the normal surface-tension value for pure water (70.5mN/m) to the equilibrium value (61.5mNm) which had been obtained in a previous study using the pendant-drop method. An attempt was made to correlate the obtained “interfacial tension versus time” data based on an adsorption/desorption kinetics model.

Hygroscopic properties and cloud condensation nuclei activation of limonene-derived organosulfates and their mixtures with ammonium sulfate

Abstract. Organosulfates have been observed as constituents of atmospheric aerosols in a wide range of environments; however their hygroscopic properties remain uncharacterised. Here, limonene-derived organosulfates with a molecular weight of 250 Da (L-OS 250) were synthesised and used for simultaneous measurements with a hygroscopicity tandem differential mobility analyser (H-TDMA) and a cloud condensation nuclei counter (CCNC) to determine the hygroscopicity parameter, κ, for pure L-OS 250 and mixtures of L-OS 250 with ammonium sulfate (AS) over a wide range of humidity conditions. The κ values derived from measurements with H-TDMA decreased with increasing particle dry diameter for all chemical compositions investigated, indicating that κH-TDMA depends on particle diameter and/or surface effects; however, it is not clear if this trend is statistically significant. For pure L-OS 250, κ was found to increase with increasing relative humidity, indicating dilution/solubility effects to be significant. Discrepancies in κ between the sub- and supersaturated measurements were observed for L-OS 250, whereas κ of AS and mixed L-OS 250/AS were similar. This discrepancy was primarily ascribed to limited dissolution of L-OS 250 at subsaturated conditions. In general, hygroscopic growth factor, critical particle diameter and κ for the mixed L-OS 250/AS particles converged towards the values of pure AS for mixtures with ≥ 20 % w / w AS. Surface tension measurements of bulk aqueous L-OS 250/AS solutions showed that L-OS 250 was indeed surface active, as expected from its molecular structure, decreasing the surface tension of solutions with 24 % from the pure water value at a L-OS 250 concentration of 0.0025 mol L−1. Based on these surface tension measurements, we present the first concentration-dependent parametrisation of surface tension for aqueous L-OS 250, which was implemented to different process-level models of L-OS 250 hygroscopicity and CCN activation. The values of κ obtained from the measurements were compared with κ calculated applying the volume additive Zdanovskii–Stokes–Robinson mixing rule, as well as κ modelled from equilibrium Köhler theory with different assumptions regarding L-OS 250 bulk-to-surface partitioning and aqueous droplet surface tension. This study is to our knowledge the first to investigate the hygroscopic properties and surface activity of L-OS 250; hence it is an important first step towards understanding the atmospheric impact of organosulfates.

Enthalpic pairwise self-association of l-carnitine in aqueous solutions of some alkali halides at T = 298.15 K

Knowledge of the influence of ions of various nature on intermolecular hydrophilic and hydrophobic interactions in solutions is required in many research fields. In this paper, dilution enthalpies of zwitterion l-carnitine in aqueous NaCl, KCl and NaBr solutions of various molalities (b=0 to 3.0mol·kg−1) have been determined respectively at T=(298.15±0.01)K and p=(0.100±0.005)MPa by isothermal titration calorimetry (ITC). In light of the MacMillan–Mayer theory, the 2nd virial enthalpic coefficients (h2) have been calculated. The h2 coefficients increase gradually with increasing molality (b) of the three aqueous alkali halides solutions, from small negative values in pure water to relatively larger positive values in solution. The trends of h2 coefficients are ascribed to the salt effects on the balance between hydrophilic and hydrophobic interactions in pairwise self-associations. It is considered that the size of cations and anions exert influences on h2 coefficients through their surface charge densities and hydration (or dehydration) abilities.