In a previous paper, the authors have given correlations for seawater thermophysical properties as functions of temperature and salinity, but only for near atmospheric pressures. Seawater reverse ...osmosis (SWRO) systems operate routinely at pressures of 6MPa or more; however, experimental data for seawater properties at elevated pressures (P=0.1–12MPa) are limited to a salinity of 56g/kg. To accurately model and design SWRO and thermal desalination systems, a reliable method of estimating the effect of pressure on seawater properties is required. In this work, we present this method and new correlations for seawater thermophysical properties that are valid within the range: t=0–120°C, S=0–120g/kg, and P=0–12MPa. Seawater isothermal compressibility data, available until a salinity of 56g/kg, were used to develop a correlation for compressibility that is extrapolated to 160g/kg. Thermodynamic identities were then used to develop accurate pressure dependent correlations for seawater: density, isobaric expansivity, specific heat capacity, enthalpy, entropy and Gibbs energy. New correlations were proposed for seawater: vapor pressure, thermal conductivity and activity of water. Recent work on seawater surface tension and osmotic coefficient were reviewed. Uncertainty bounds were calculated for each correlation.
•New pressure-dependent correlations for seawater properties: κ, β, ρ, cP, h, s and g•Correlations are valid for: t=10–120°C, S=0–120g/kg and P=0–12MPa.•New correlations for seawater properties: pv, k, and aw•Review of recent work on seawater properties: γ, φ, and π•Uncertainty bounds predicted using thermodynamics and statistical methods
The serum osmolarity mainly results from the inorganic ions and the small molecules and only in small extent from the protein ions. In serum sodium, potassium, chloride, bicarbonate, urea and glucose ...are the only components present in high enough concentrations to individually affect the osmolality. There are several different formulas for the calculation of human serum osmolarity. It has not been demonstrated which of the formulas is most effective for serum from various animal species. The goal of this study is to estimate the serum osmolarity in pigs from the concentrations of the main electrolytes and the glucose and urea content, and to establish the contribution of each osmotic component. Linear regression analysis was carried out to determine the best predictors of serum osmolarity in chickens. Two equations were also deduced for calculating serum osmolarity using manual regression analysis: y = 1.8117 Na + Urea + Glucose + 26.05 and y = 1.8933 (Na+K) + Urea + Glucose + 4.93.
The thermo-osmotic coefficient of a porous medium is the ratio of the mass flow rate and the temperature difference that drives the flow. Thermo-osmotic coefficients of the Millipore DuraPore HVHP, ...GVHP and VVHP membranes have been measured using a new apparatus designed to provide accurate mass flux measurements with tightly controlled temperatures, pressures, and compositions on the feed and distillate side. To properly analyze the experimental data, recommendations on data reduction procedures anchored in non-equilibrium thermodynamics are discussed. An expression is presented for the apparent energy of activation of the transport process in terms of the derivative of the thermo-osmotic coefficient with respect to the inverse mean temperature. The expression is shown to accurately predict the temperature dependence of the thermo-osmotic coefficients from experiments. The expression is next used to explain observations in similar porous systems from the literature. Based on this, an optimization scheme to find the optimal mean pore radius to maximize the power density of a pressure-retarded membrane distillation (PRMD) process is presented. For membranes with properties similar to the Durapore XXHP series membranes, the optimal pore radius is found to be between 1 and 10 nm. It is shown that the power density can benefit greatly from a narrow pore size distribution and from membrane surface treatments that increase the liquid-solid contact angle, potentially exceeding a benchmark minimum power density of 5 W/m2 (set for the feasibility of pressure-retarded osmosis). An assessment of the second law efficiency of the PRMD process is also presented. A critical part of the process is due to the inevitably smaller water flux through smaller pores, required to maintain a high pressure difference and a feasible power density. This can only be alleviated by increasing the temperature difference across the membrane. We conclude that membranes designed for the PRMD process need increased overall thermal resistance to enhance performance.
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•New apparatus and recommended methodology for measuring thermo-osmotic coefficients.•Temperature-dependence of thermo-osmotic flux through membranes analyzed in detail.•Mechanical power density from pressure-retarded membrane distillation (PRMD) discussed.•Present limitations of PRMD analyzed. Membrane properties identified as limiting factors.•Specific recommendations for membrane optimization for PRMD are provided.
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•CRMs of LiCl solution for water activity were prepared using gravimetric method.•Purity of LiCl was determined using mass balance approach and potentiometric titration, then molality ...(m) of solution was calculated.•Osmotic coefficient (ϕ) of LiCl was calculated using m and standard data expressed as the Debye–Hückel equation.•Certified value was calculated using an exponential function of the product of ϕ, m, and M.•Certified values of two CRMs were 0.250 ± 0.006 and 0.500 ± 0.007.•CRMs can be used to calibrate water activity meters.
Water activity (a) is used to assess the microbiological stability, shelf life, and safety of food. Water activity meters using electric humidity sensors can measure water activity conveniently. To calibrate water activity meters, certified reference materials (CRMs) of lithium chloride (LiCl) solution for water acidity were prepared by using the gravimetric method. Both the mass balance approach and potentiometric titration were combined to determine the purity of LiCl, and the molality (m) was calculated. The osmotic coefficient (ϕ) was calculated using m and the standard data for ϕ expressed as the Debye–Hückel equation. The certified value of a was calculated using an exponential function of the product of ϕ, m, and molecular mass of water. The certified values and uncertainty (U, k = 2) of two CRMs were 0.250 ± 0.006 and 0.500 ± 0.007, respectively. These two CRMs can be used to calibrate water activity meters and validate analytical methods.
•Method for the evaluation of activity coefficients of multicomponent solutions.•Based on the resolution of the Gibbs-Duhem equation for osmotic coefficient.•Contributions of the binary systems and ...of a mixing effect.•Applied to a ternary aqueous solution with an electrolytic and a molecular solute.
Starting from the solution of the Gibbs-Duhem equation for multicomponent systems on terms of the osmotic coefficient, a method was developed to evaluate the activity coefficients of the electrolytic and molecular solutes of a ternary aqueous solution. An analytical expression of the osmotic coefficient was proposed for the accurate description of experimental data, which is in agreement with the behaviour of the binary systems at the corresponding limiting concentrations. Then the expressions of the activity coefficients of the two solutes were derived, which satisfy the condition of state function through the equality of the cross partial derivatives. Finally, such expressions were applied to the systems water(1)-NaCl(2)-sucrose(3) and water(1)-tetrabutylammonium bromide(2)-urea(3), verifying the accuracy of the proposed method.
•Some concentration-dependent properties were obtained, especially RDF, diffusion property, NCE, etc.•The excess Raman spectra and polarized Raman spectra were used in the analysis of aqueous ...solution structure.•The correlation between the osmotic coefficient and the hydrogen bonds network was preliminary studied.•The experimental results fits well with the simulated methods.
The NH4Cl aqueous solution ranging from 1.00 wt.% to 22.00 wt.% have been studied by molecular dynamic simulation, Raman spectroscopy and polarized Raman spectroscopy. Radial distribution function (RDF), diffusion property, structure of hydrogen bond network, excess Raman spectroscopy and non-coincidence effect (NCE) were obtained. The contact ion pairs of cation and anion appeared in NH4Cl solution of 15.00 wt.%, leading to fundamental changes in hydrogen bonds and the hydrated shell. The evolution of hydrogen bond with mass fraction in solution was described. The osmotic coefficient of NH4Cl aqueous solution was obtained by thermodynamic calculation, and its linear relationship with double donor single acceptor hydrogen bond (DDA-OH) was preliminarily summarized. Moreover, the experimental results are in good agreement with the simulation results.
•Formalism to evaluate the activity coefficients of ternary molecular solutions.•Calculation from experimental osmotic coefficient data correlation.•Description of the contributions of the binary ...systems and of a mixing effect.•Resolution of the Gibbs-Duhem differential equation for ternary systems.
A method is proposed for the evaluation of the activity coefficients of a solution constituted by a solvent (1) and two non-volatile molecular solutes (2,3) from the experimental dependence of the osmotic coefficient of the ternary solution (1,2,3) on composition. A generalized analytical expression is derived to describe such dependence, based on the sum of the weighted contributions of both binary systems and the contribution due to the mixing effect. With the resulting expression and using the solution of the Gibbs-Duhem differential equation for ternary systems, the equations that allows the evaluation of the corresponding experimental activity coefficients of both solutes in ideal dilute solution reference state (molality scale) are derived. From the comparative analysis and discussion of the results obtained for three ternary systems, it was possible to verify that the proposed methodology provides a rigorous alternative to evaluate suitable values of activity coefficients from experimental data of osmotic coefficients. Finally, in order to facilitate the correlation of these values with equations originated in molecular solution modelling (NRTL, UNIQUAC, etc.), the relationships between the corresponding reference states and concentration scales were established.
•SPB theory successfully applied to a PM electrolyte containing 7 ion species at 273.15 K and 298.15 K.•SPB requires 7 coupled equations to be solved, HNC integral equation requires 28.•DH, SPB, MSA ...thermodynamics of a 7-ionic species PM sea-water model compared with MC.•MSA, SPB predict MC osmotic and activity coefficients closely, DH shows deviations.•SPB approach can be improved by using modified Poisson-Boltzmann theory.
A symmetric Poisson-Boltzmann theory is applied to a primitive model electrolyte solution containing 7 different ion species. Only 7 coupled equations need to be solved for the mean electrostatic potential around the ions once the uncharged hard sphere radial distribution function is specified. Comparison is made with the individual activity and osmotic coefficients of a simulation study of a sea water mixture. Good overall agreement is found with the simulation results.
•Determination of the thermodynamic properties of the system {yNH4Cl+(1-y)NH4H2PO4}(aq) at 25 °C.•Application of the PSC model to describe the thermodynamic behavior of aqueous solutions.•Calculation ...of NH4Cl and NH4H2PO4 activity coefficients in the system {yNH4Cl+(1-y)NH4H2PO4}(aq).•Prediction of NH4Cl and NH4H2PO4 solubilities in aqueous solution.
The mixed aqueous electrolyte system ammonium chloride and ammonium di-hydrogen phosphate has been studied with the hygrometric method at the temperature 298.15 K. The water activities, osmotic coefficient and solubilities are deduced from measurements of relative humidities of this system against total molality ranging from 0.4 mol.kg−1 to about saturation, and for different ionic-strength fractions y of NH4H2PO4 (y = INH4H2PO4/INH4H2PO4 + INH4Cl) of 0, 1/4, 1/3, 1/2, 2/3, 3/4 and 1. Experimental results are compared to Dinane rule by the Extended Compound Additivity Law (ECA), Leitzke-Stoughton (LS II) and Lin et al. equation. The obtained results were correlated using the PSC model to predict the solute activity coefficients in the mixture for different compositions of the system and are also used to calculate the solubility and excess Gibbs energy in the studied molality range.
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