Henry's Law Solubility Research Articles

Sorption isotherms, sorption enthalpies, diffusion coefficients and permeabilities of water in a multilayer PEO/PAA polymer film using the quartz crystal microbalance/heat conduction calorimeter

Sorption isotherms, sorption enthalpies, and diffusion coefficients for water in an 11 μm thick PEO/PAA multi-layer film have been measured at 30, 40, and 60 °C for relative humidities between 0 and 70%. All quantities were measured on the same film using the quartz crystal microbalance/heat conduction calorimeter. Water diffusion coefficients in the film are several orders of magnitude lower than in the separate components. Sorption isotherms are of type III at 30 and 40 °C and linear at 60 °C. Water vapor permeabilities are calculated as the product of Henry's law solubility and diffusion coefficient. The permeability of the PEO/PAA multilayer film is exceedingly low compared to other polymer films used as membranes. The enthalpy of water sorption determined from the sorption isotherms using the van’t Hoff relation is 32.9 ± 0.3 kJ/mol. Calorimetric enthalpies of water sorption range from 42 to 34 kJ/mol at 30 and 40 °C over the humidity range studied. The change in motional resistance, a quantity proportion to the loss compliance of the film, has also been recorded at all three temperatures, and a common trend is an increase in loss compliance with increasing relative humidity, indicating plasticization of the film by water.

Heterogeneous chemistry of octanal and 2, 4‐hexadienal with sulfuric acid

Recent experimental studies using the environmental chamber have suggested that acid‐catalyzed particle‐phase reactions of organic carbonyls lead to multifold increases in secondary organic aerosol (SOA) mass, but the kinetics and mechanism of the heterogeneous chemistry of carbonyls with sulfuric acid remain largely uncertain. We report the first measurements of heterogeneous uptake of octanal and 2, 4‐hexadienal on liquid H2SO4 in the acid range of 60 to 85 wt % and between 250 and 298 K. Octanal was physically absorbed by sulfuric acid without undergoing irreversible reaction. From the time‐dependent uptake the effective Henry's law solubility constant (H*) was determined. Irreversible reactive uptake was observed for 2, 4‐hexadienal, and the uptake coefficient decreased with decreasing acid concentrations. The uptake of octanal and 2, 4‐hexadienal on liquid H2SO4 is explained by aldol condensation, dependent on acidity. The results suggest that aldol condensation of the aldehydes can be important in the upper troposphere, but may not significantly contribute to secondary organic aerosol formation in the lower troposphere.

Measurement of the Henry's law coefficient and first order loss rate of PAN in n‐octanol

The Henry's Law solubility and first order loss rates of PAN (peroxyacetic nitric anhydride, CH3C(O)OONO2) in a model non‐polar solvent, n‐octanol, were measured for a range of temperatures pertinent to the lower troposphere (273–298 °K). The solubility was found to be factors of 6 to 12 higher than those measured previously for pure water, ranging between 110 ± 7.5 M/atm at 273°K and 34 ± 1.7 M/atm at 298°K. The loss rates were found to vary from below 0.5 × 10−5 sec−1 at 273°K to 5.2 ± 1.9 × 10−5 sec−1 at 298°K. Several simple approaches were used to estimate that the uptake of PAN on organic aerosol has a negligible impact on ambient PAN concentrations.

Vapor sorption in plasma polymerized vinyl acetate and methyl methacrylate thin films

Vapor sorption isotherms of vinyl acetate (VAc) and methyl methacrylate (MMA) plasma polymer thin films are measured and compared with those for cast films of the conventionally polymerized analogs. Sorption isotherms are collected for methanol, acetone, hexane, and water at 30°C using a Quartz Crystal Microbalance (QCM). The isotherms are analyzed using both Dual-Mode and Flory–Huggins sorption models. In general, plasma polymer sorption isotherms approximate those of the conventional polymer analogs, but exhibit an enhanced Langmuir-type sorption component at low activity. Accordingly, Dual-Mode model parameters show roughly equivalent Henry's Law solubility coefficients with the Langmuir-type capacity parameters (CH′) being 5–20-fold higher than those for the conventional polymer materials.

Kinetics of the reactive uptake of ozone on oleic acid aerosols

Heterogeneous reactions involving particles and gas-phase species can alter important chemical and microphysical properties of aerosols, complicating modeling efforts to assess their effects on climate and human health. Organic aerosols are common in the troposphere; precursors include vegetation, the ocean surface, and various combustion processes. Ozone is an important oxidant in the troposphere (Finlayson-Pitts and Pitts, 1997), often in concentrations sufficient to cause adverse effects on human health and vegetation. Oleic acid is one of a group of organic species proposed as an important tracer species for use in source characterization of ambient aerosols (Rogge et al., 1991). However, the relative fraction of these species may change as the particle ages, and new product species are likely to be introduced. Little is known about the kinetics of organic species in atmospheric aerosols. Such knowledge is necessary for quantitative assessment of field studies as well as for use in climate models. With this motivation, we have chosen oleic acid (one of the simplest condensed phase organics with atmospheric relevance) as the first species to be used in a series of experiments aimed at investigating the dynamic evolution of the composition and size of organic particles in the presence of ozone. Our experimental setup includes an atmospheric pressure flow reactor, in which oleic acid particles of a pre-selected size are allowed to interact with ozone for a controlled time, coupled to a newly developed aerosol mass spectrometer (AMS), (Jayne et al., 2000), which monitors changes in the size distribution and composition of the aerosols. This AMS/flow reactor system permits a new approach to kinetic studies in that the depletion of the particle-phase reactant (rather than the gas-phase reactant) is monitored. In the present study we report the size dependent rate of reactive uptake of ozone by three different sizes of oleic acid particles. Depletion of oleic acid, appearance of product species, and the growth of particle size are all observed simultaneously. With interaction times from 2 to 11 seconds, a given run takes place at nearly constant ozone concentration. The figure below indicates the fraction of oleic acid remaining in a particle as a function of ozone exposure time. We are developing an uptake model which allows determination of the following fundamental physico-chemical parameters: Henry's Law solubility constant for ozone in oleic acid, H, the liquid phase diffusion coefficient for ozone in oleic acid, D, and the second order rate coefficient for ozone reacting with oleic acid, k 2. The plotted curves show a preliminary fit to the size dependent reaction data, yielding the values shown at 293°K. These parameters allow calculation of the reactive collision probability, γ, which ranges from about 10 −3 to 10 −5 (decreasing with a decrease in oleic acid concentration). Our data also show a dependence in the uptake on the purity of the oleic particles, an increase in viscosity upon reaction, and an increase in particle diameter as the interaction time increases. These effects (including those of secondary reaction of products) are currently being modeled in order to assess aerosol phase oleic acid atmospheric lifetimes.

Heterogeneous Chemistry of Acetone in Sulfuric Acid Solutions: Implications for the Upper Troposphere

The uptake of acetone vapor by liquid sulfuric acid has been investigated over the range of 40−87 wt % H2SO4 and between the temperatures 198 and 300 K. Studies were performed with a flow-tube reactor, using a quadrupole mass spectrometer for detection. At most concentrations studied (40−75 wt %), acetone was physically absorbed by sulfuric acid without undergoing irreversible reaction. However, at acid concentrations at or above 80 wt %, reactive uptake of acetone was observed, leading to products such as mesityl oxide and/or mesitylene. From time-dependent uptake data and liquid-phase diffusion coefficients calculated from molecular viscosity, the effective Henry's law solubility constant (H*) was determined. The solubility of acetone in liquid sulfuric acid was found to increase with increasing acid concentration and decreasing temperature. In the 75 wt % and 230 K range, the value for H* was found to be ∼2 × 106 M/atm. This value suggests that acetone primarily remains in the gas phase rather than absorbing into sulfate aerosols under atmospheric conditions.

Sorption of Gases and Vapors in an Amorphous Glassy Perfluorodioxole Copolymer

Gas and vapor sorption properties of a random copolymer of 87 mol % 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole and 13% tetrafluoroethylene (AF2400) are reported. Using both pressure decay and inverse gas chromatography (IGC) methods, a wide range of solutes was studied: He, N2, O2, CO2, C1−C13 n-alkanes, CF4, C2F6, C6F6, and C6F5CF3. These solutes have critical temperatures ranging from 5 to 677 K. AF2400 has very large solubility coefficients, S, relative to other glassy and rubbery polymers. Only poly(1-trimethylsilyl-1-propyne), the most permeable polymer known, exhibits higher solubility coefficients. The large solubility coefficients in AF2400 are mainly due to high Henry's law solubility coefficients. Fluorocarbon solutes exhibit higher solubility than their hydrocarbon analogues. A novel linear correlation between the logarithm of S and Tc2, where Tc is the solute critical temperature, was observed. On the basis of IGC results, the microcavity size in this perfluoropolymer is larger than in conventional hydrocarbon-based glassy polymers.

Chemistry at and near the Surface of Liquid Sulfuric Acid: A Kinetic, Thermodynamic, and Mechanistic Analysis of Heterogeneous Reactions of Acetone

The interactions of gas-phase acetone with liquid sulfuric acid solutions are described. The solutions were prepared as 0.05−0.10 μm thick films deposited on single-crystal metal substrates. Experiments were carried out over broad ranges of acid composition (70 − >96 wt % H2SO4), temperature (180−220 K), and acetone pressure (10-7−10-3 Pa). Two types of measurements are reported: the time-dependent acetone uptake probability, and the infrared spectra of absorbed acetone and its reaction products. From the infrared measurements, a reaction scheme is identified in which gas-phase acetone is taken up by sulfuric acid to form protonated acetone. In solutions containing more than 70 wt % H2SO4, protonated acetone undergoes a self-condensation/dehydration reaction to form mesityl oxide. In films that contain 85 wt % or more H2SO4, a second reaction sequence occurs, ultimately resulting in the formation of trimethylbenzene. The uptake probability measurements are consistent with the infrared data. In 70 wt % H2SO4, the acetone uptake probability rapidly decreases from an initial value near unity to a steady-state value of zero, due to the formation of a saturated acetone + sulfuric acid solution. The Henry's law solubility constants of acetone in 70 wt % H2SO4 were obtained from the integrated uptake measurements. The temperature dependence of the measurements implies that the standard-state enthalpy and entropy changes of acetone solution in 70 wt % sulfuric acid are −66 kJ mol-1 and −249 J mol-1 K-1, respectively. In the more concentrated films, the steady-state uptake probability is never measured to be zero, since absorbed acetone goes on to form the condensation/dehydration products. A two-step kinetic scheme is proposed to account for the reactions of acetone in sulfuric acid. By fitting the data to the model predictions, the Henry's law solubility constants and the reaction rate constants may be estimated.

Oxygen transfer characteristics of multiple-phase dispersions simulating water-in-oil xanthan fermentations

A water-in-oil (W/O) cultivation technology has the potential of overcoming the problems related with high broth viscosity in xanthan fermentations. The aqueous broth is dispersed in a continuous oil phase. Consequently, the broth thickening mechanisms are confined within the aqueous droplets without significantly increasing the overall viscosity. To better characterize the mixing and oxygen transfer in the complex multiple-phase (G-O-W) systems involved, the W/O dispersions of xanthan solutions in either n-hexadecane or vegetable oil were examined in this study. The experiments with n-hexadecane indicated that the coefficient for oxygen transfer from gas bubbles to the oil, i.e., (k L a)g/o, was much smaller than that for transfer from the bulk oil phase to the droplet surface, i.e., (k L a)o/w. The oxygen partial pressure at the surface of aqueous droplets, p R , was therefore close to that in the bulk oil phase. The experiments with vegetable oil were conducted under various combinations of operating conditions: agitation speed (N) – 400, 600, and 775 rpm; aeration rate (G/V) – 0.25, 0.5, and 0.875 vvm; aqueous-phase volume fraction (φw) – 0.2, 0.3, 0.4 and 0.5; and aqueous-phase xanthan concentration (Xn) – 10, 20, and 40 kg/m3. The correlations developed for the power input of agitation (P g, in W), droplet diameter (d p , in μm), and (k L a)g/oHo (in kg mol/m3 s atm) are: where Ho is the Henry's law solubility for oxygen in the oil phase (kg mol/m3 atm) and v s is the superficial gas velocity. The dependencies associated with P g, d p , and N are consistent with those reported in the literature for simpler systems although no previous correlations exist for complex G-L-L systems. The dependencies associated with Xn are intuitively plausible while the responsible mechanisms for the observed dependencies on φw are less clear.

Transport Mechanisms of Gases in Annealed Linear Low Density Polyethylene Films

The effect of the pressure difference on the permeability of carbon dioxide, oxygen, and nitrogen through annealed LLDPE films is studied. The isotherms showing the dependence of the permeability coefficient on the pressure of the upstream chamber, po, exhibit an anomalous decrease in the low-pressure region whose location is shifted to lower values of po as the temperature of the isotherms decreases. The diffusion coefficient increases with po, the increase being larger the higher is the temperature. The curves showing the dependence of the solubility coefficient on the pressure of the upstream chamber exhibits the same pattern as that of the permeability coefficient. The strong dependence of the diffusive characteristics of gases on po in the low-pressure region was interpreted in terms of the dual mode theory. The values of the apparent diffusion coefficients for the molecules in the dissolved and the trapped modes are estimated. In the same way, the Henry's law solubility coefficient, kD, and the Langmuir sorption capacity, C‘H, are obtained. The values of kD and C‘H for different gases are somewhat lower than those reported for glassy membranes. A detailed study on the effect of po on the activation energies associated with both the permeability and the diffusion coefficients is reported.

3D-modelling and prediction by WHIM descriptors. Part 9. Chromatographic relative retention time and physico-chemical properties of polychlorinated biphenyls (PCBs)

Physico-chemical properties of polychlorinated biphenyls (PCBs) congeners have been extensively studied searching for quantitative structure–property relationships (QSPR). The chemical description of PCBs structure is made in terms of WHIM descriptors, which are 3D molecular descriptors taking into account size, shape, symmetry and atom distribution of the molecules. The regression models have been obtained by optimizing their prediction power and by selecting the best subset of descriptors by genetic algorithm. The results confirm the capability of this approach to give predictive models for important physico-chemical properties, such as relative retention time, log K ow, melting point, total surface area, Henry's law constant, solubility, and aqueous activity coefficients.

Solubility of nitrous acid (HONO) in ammonium sulfate solutions

The Henry's law solubility of nitrous acid (HONO) has been studied in ammonium sulfate solutions as a function of salt concentration in the range 5–39.2 wt.% and temperature between 263 and 298 K by measuring the distribution of HONO between the gas and liquid phases using a bubbler-type gas–liquid reactor. Gas phase concentrations have been measured by tuneable diode laser spectrometry, whereas the liquid phase has been analysed by ion chromatography.An exponential dependence of the Henry's law constant (KH) on c(NH4)2SO4 has been observed with increasing ammonium sulfate concentration caused by the salt effect which is described by the Setschenow equation. The values of ΔHsol and ΔSsol for the dissolution of HONO have been determined as a function of ammonium sulfate concentration from the temperature dependence of KH. The results were fitted to a two-parameter equation that allows the calculation of the solubility of HONO in the temperature and concentration ranges studied. The Henry's law constant of HONO in ammonium sulfate solutions is well described by: KH = A(T) exp(B(T)c(NH4)2SO4) mol kg−1 bar−1 with A(T) = 3.06 × 10−6 exp(4932T−1) mol kg−1 bar−1B(T) = 17.6T−1 − 0.083 wt.%−1 and c(NH4)2SO4 in wt.% and T in K. From the calculated values it can be concluded, that for a tropospheric ammonium sulfate aerosol scenario most HONO will be found in the gas phase.

Heterogeneous interaction of formaldehyde with cold sulfuric acid: Implications for the upper troposphere and lower stratosphere

Laboratory studies of formaldehyde uptake on thin sulfuric acid films indicate that HCHO can be taken up for long periods of time without saturation. Initial Henry's law solubility coefficients are large (H* = 106–107 M atm−1) at stratospheric temperatures. This uptake is due to rapid formation of HCHO(aq), CH2(OH)2, and possibly HOCH2OSO2(OH) in solution. Over a longer time period, steady‐state uptake continues with γ≈0.002 due to formaldehyde polymerization. Although uptake by stratospheric sulfate aerosols will not provide a significant sink for atmospheric formaldehyde, it may lead to high condensed‐phase concentrations of HCHO and polymerization in solution. Reaction of condensed HCHO with nitric acid in sulfuric acid has also been observed, converting HNO3 to odd nitrogen (NOx) and formaldehyde to formic acid. This reaction may have considerable impact on the HNO3/NOx ratio, as its rate is likely comparable to the HNO3 photolysis rate.

Heterogeneous Chemistry of HO2NO2 in Liquid Sulfuric Acid

The interaction of HO2NO2 (peroxynitric acid, PNA) vapor with liquid sulfuric acid was investigated for acid contents ranging from 53 to 74 wt % and at temperatures between 205 and 230 K, using a fast-flow reactor coupled to a chemical ionization mass spectrometer. PNA was observed to be physically taken up by liquid sulfuric acid, without undergoing irreversible aqueous-phase reactions. From the time-dependent uptake, the quantity H* (that is, the product of the effective Henry's law solubility constant and the square root of the liquid-phase diffusion coefficient) was obtained. The effective Henry's law solubility constant H* of PNA in liquid sulfuric acid was derived by estimating the liquid-phase diffusion coefficient based on a cubic cell model. In general, the solubility was found to increase with decreasing acid content and decreasing temperature. The heterogeneous reaction between PNA and HCl in liquid sulfuric acid was also examined and was found to be very slow (γ < 1 × 10-4). The measured solub...

Heterogeneous interaction of peroxyacetyl nitrate with liquid sulfuric acid

The uptake of peroxyacetyl nitrate (PAN) on liquid sulfuric acid surfaces has been investigated using a fast‐flow reactor coupled to a chemical ionization mass spectrometer. PAN was observed to be reversibly adsorbed on sulfuric acid. From the time‐dependent uptake, Henry's law solubility constant of PAN in sulfuric acid was obtained. The measured solubility constant was found to depend strongly on temperature (199–226 K), but weakly on acid composition (46–72 wt%). On 72 wt% H2SO4, for example, the effective Henry's law solubility constant was determined to be about 5.6×104 and 3.1×103 M atm−1 at 208 and 222 K, respectively. Heterogeneous reactions of PAN with HCl, Cl, ClO, and OClO on liquid sulfuric acid were also investigated and found to be very slow (γ&lt;1×10−4). Atmospheric implications of the present results are discussed.

Solubility measurements of methane and ethane in water at and near hydrate conditions

The isobaric solubility of pure methane and ethane gases in liquid water was measured under different conditions, including hydrate formation points, using a ramping method in which measurements are made through the entire and continuous hydrate formation/decomposition cycle. The work was conducted for methane at 3.45 MPa (500 psia) and temperatures ranging from 17.0 to 0.0°C (290.2 to 273.2 K), and for ethane at 0.66 MPa (95 psia) and a temperature range of 17.0 to 0.0°C (290.2 to 273.2 K). The isobaric solubilities obtained show a significant divergence from (normal) Henry's law solubility as the temperature is lowered. The increase in the solubility is presumably the result of the onset of a sorption process that traps the gas molecules in the water structure. Several sub-processes were observed as the hydrate formation was taking place: (1) the dissolution of the gas in the liquid water, or interstitial solubility, (2) the onset of the sorption sub-process and build-up of the hydrate precursors, (3) the catastrophic formation and the existence of the solid phase with its slushy characteristics, and (4) the solidification of the hydrates, therefore causing the total plugging of the experimental cell.

Solubility data requirements and new experimental methods in atmospheric aerosol research

Abstract

Solubility of alcohols in ethylene-vinyl alcohol copolymers by inverse gas chromatography

Sorption isotherms of alcohols in EVOH copolymers were determined by inverse gas chromatography below and above the glass transition temperature. The sorbates studied were : methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, and t-butanol. From the sorption isotherms, Henry's law solubility coefficients (S) were evaluated and correlated to size, condensability, and OH position in the molecule as well as on temperature. Molecular dimension was an important factor, affecting the solubility via two contrary effects : molecular size and condensability. When comparing alcohols of the same size, primary alcohols were sorbed more than secondary alcohols and these more than tertiary alcohols at every temperature in the study. At low temperatures, the larger the size the greater the solubility, contrary to what was observed at high temperatures. Temperature effect on solubility was also tested applying Van't Hoff's equation. Since S behaved differently below and above T g for every sorbate two values of the enthalpy of solution were obtained, positive above T g and negative below T g .

On pressure dependence of the parameters of the dual-mode sorption model

Sensitivity of the parameters of the dual-mode sorption (DMS) model on the pressure range, in which sorption of gases in polymers have been studied, was analyzed. Different “gas-polymer” systems were considered but the most detailed analysis was performed for sorption of argon and nitrogen in poly[5,5-difluoro-6,6-bis(trifluoromethyl)] norbornene and polysulfone. It was shown that the model parameters depend upon the range of gas pressure studied. Expanding of the pressure range (0-pi) results in an increase in the Langmuir adsorption capacity C′H and in reduction of Henry's law solubility coefficient kD and Langmuir affinity parameter b. These behaviors does not depend on a choice of an experimental apparatus or software and procedure of nonlinear least squares treatment of the data. As statistical analysis indicated, a systematic error of the measurement cannot call forth the observed dependencies of the model parameters. Different physical reasons of these behaviors were considered, among them: the pressure dependence of the affinity parameter, and the dilation of a polymer. The results obtained showed that although the DMS model, as a rule, gives an excellent fit of the experimental curves, and, hence, can be used as a form of compact storage of information on gas sorption in polymers, one should be careful in using it outside the pressure range in which its parameters have been determined. © 1996 John Wiley & Sons, Inc.

On pressure dependence of the parameters of the dual‐mode sorption model

Sensitivity of the parameters of the dual-mode sorption (DMS) model on the pressure range, in which sorption of gases in polymers have been studied, was analyzed. Different “gas-polymer” systems were considered but the most detailed analysis was performed for sorption of argon and nitrogen in poly[5,5-difluoro-6,6-bis(trifluoromethyl)] norbornene and polysulfone. It was shown that the model parameters depend upon the range of gas pressure studied. Expanding of the pressure range (0-pi) results in an increase in the Langmuir adsorption capacity C′H and in reduction of Henry's law solubility coefficient kD and Langmuir affinity parameter b. These behaviors does not depend on a choice of an experimental apparatus or software and procedure of nonlinear least squares treatment of the data. As statistical analysis indicated, a systematic error of the measurement cannot call forth the observed dependencies of the model parameters. Different physical reasons of these behaviors were considered, among them: the pressure dependence of the affinity parameter, and the dilation of a polymer. The results obtained showed that although the DMS model, as a rule, gives an excellent fit of the experimental curves, and, hence, can be used as a form of compact storage of information on gas sorption in polymers, one should be careful in using it outside the pressure range in which its parameters have been determined. © 1996 John Wiley & Sons, Inc.