Henrys constant

Table 4.19 gives the Henry constants for a few common gaseous components. The chemical nature is also a dominant factor. The effect of temperature is moderate note that the solubility passes through a minimum that depends on the hydrocarbon in question and that it is around 100°C. 

Measurement of the retention time (tl) under known flow conditions thus provides a simple means of determining the equihbrium constant (Henry constant) ... 

Many simple systems that could be expected to form ideal Hquid mixtures are reasonably predicted by extending pure-species adsorption equiUbrium data to a multicomponent equation. The potential theory has been extended to binary mixtures of several hydrocarbons on activated carbon by assuming an ideal mixture (99) and to hydrocarbons on activated carbon and carbon molecular sieves, and to O2 and N2 on 5A and lOX zeoHtes (100). Mixture isotherms predicted by lAST agree with experimental data for methane + ethane and for ethylene + CO2 on activated carbon, and for CO + O2 and for propane + propylene on siUca gel (36). A statistical thermodynamic model has been successfully appHed to equiUbrium isotherms of several nonpolar species on 5A zeoHte, to predict multicomponent sorption equiUbria from the Henry constants for the pure components (26). A set of equations that incorporate surface heterogeneity into the lAST model provides a means for predicting multicomponent equiUbria, but the agreement is only good up to 50% surface saturation (9). 

On the other hand, the dependence of the Henry constant upon can be represented as [63]... 

Henry constant F can be evaluated by the method of Tsvitering and Krevelyn (see [105]) based on the concept of mean lifetime of a molecule absorbed on a surface proposed by De Boer [106]. The number of molecules adsorbed on a surface is... 

Ha or Hh Henry constant for gas A or hydrogen related to molar fraction MPa... 

Absorption - desorption - N-octanol/water coefficient - Henry constant - Biodegradation and/or abiotic degr. disappearance coef. - Bioaccumulation - Aquatic Ecotox Fish 24 to 96 hours Daphnia 24 to 48 hours - Air/soil/sediment Ecotox ... 

In principle, this system of 20 equations can be solved provided the equilibrium constants, activities, Henry-constants and fugacities are available. While some results for most of these properties are available, there exists no approved method for calculating activities in concentrated aqueous solutions of weak electrolytes therefore, several approximations were developed. ... 

Henry constant (mmol-L -bar ) acidity constant of the couple (C02-Bicarbonate) composition of gas in A (%) liquid-gas exchange constant (day ) standard deviation of the variable A... 

Aieta, E.M. and Roberts, P.V. Henry constant of molecular chlorine in aqueous solution. /. Chem. Eng. Data, 31(l) 51-53, 1986. 

PhC properties most investigated by scientists to date are their water solubility (s, mg/mL), volatility (correlated to the Henry constant H) (pg m atr/pg m wastewater), biodegradability (correlated to pseudo-first-order degradation constant bioi L gSS d ), acid dissociation constant K, distribution and sorption (through the sludge-water distribution coefficient K, expressed in L gSS or the octanol-water partition coefficient Kg ). The main focus has been to find any correlations between these parameters and to determine PhC removal rates during the different treatment steps. Thus, different properties have been quantified for many compounds, and software, such as EPl Suite 4.00 [54], consenting their estimation, is available. 

The rate of mass transfer of a snbstance across a water-gas bonndary is controlled by the diffnsion film model as well. Gas transfer from a water sonrce is faster than from a solid sonrce, and the chemical does not nndergo a chemical reaction during the transfer process. Under these conditions, the interface concentration may be interpreted in terms of the Henry constant (K ), which indicates whether the controlling resistance is in the liqnid or the gas film. When 5, a water film is the controlling factor, while a gas film controls the behavior when K >500. 

Mass transfer coefficients In the mass transfer calculations, we need the Henry constant of oxygen in water at 30 °C, which can be evaluated using the relevant correlations presented in Section 1.3.2, Appendix I, and is equal to 34.03. The next parameter we need is the diffusion coefficient of oxygen in water at 30 °C, which can be also found in Table 1.10, Appendix I. The correction for the temperature has been also presented in eq. (1.28) Appendix I. The evaluated diffusion coefficient is 2.5 X 10-9 m2/s. 

Recall that Kiti is commonly referred to in environmental literature as the Henry s law constant. The dimensionless Henry constant is denoted Kixv/ and is related to by (Eq. 6-6) ... 

For the sorption of hydrocarbons in type-A zeolites at ordinary temperatures, the region of linearity of the isotherm is limited to very low pressures, and Henry constants are usually obtained by extrapolation from measurements outside the linear region. 

The temperature dependence of the Henry constants is governed by the usual van t Hoff equation... 

In principle, the Henry constant may be predicted theoretically by evaluation of the configuration integral for an occluded molecule. Such calculations are subject to the considerable uncertainties implicit in theoretical potential calculations (17), and the utility of this approach is now limited to simple spherical molecules such as the inert gases (18, 19). A fair estimate of the standard entropy of sorption or of the value of K0 may, however, be obtained from a simple idealized model. 

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