Henry-distribution coefficient

In the range of operating temperatures and compositions, the equilibrium relations are monotonic functions of temperature of the MSA. This is typically true. For instance, normally in gas absorption Henry s coefficient monotonically decreases as the temperature of the MSA is lowered while for stripping the gas-liquid distribution coefficient monotonically increases as the temperature of the stripping agent is increased. 

At the interface, the relation between Pco i and Cco>i is given by the distribution coefficient, called Henry s constant (H) for gas-liquid systems. Thus,... 

Equilibrium data correlations can be extremely complex, especially when related to non-ideal multicomponent mixtures, and in order to handle such real life complex simulations, a commercial dynamic simulator with access to a physical property data-base often becomes essential. The approach in this text is based, however, on the basic concepts of ideal behaviour, as expressed by Henry s Law for gas absorption, the use of constant relative volatility values for distillation and constant distribution coefficients for solvent extraction. These have the advantage that they normally enable an explicit method of solution and avoid the more cumbersome iterative types of procedure, which would otherwise be required. Simulation examples in which more complex forms of equilibria are employed are STEAM and BUBBLE. 

Organic compounds released into the vadose zone exist in four closely interrelated forms free-phase NAPL, attenuated to surface of soil grains, dissolved in water retained on and between the soil particles, and present as a gaseous phase. The mass distribution of each of these phases is controlled by such factors as concentration gradients, distribution coefficients, and Henry s law constants. 

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 partition or distribution coefficient between a gas and a liquid is constant at a given temperature and pressure. The relative volatility is used in defining the equilibrium between a volatile liquid mixture and the atmosphere. The partition coefficient expresses the relative volatility of a species A distributed between a vapor phase (Al) and a liquid phase (A2). Henry s law applies to the distribution of dilute solutions of chemicals in a gas, liquid, or solid at a specific ambient condition. Equilibrium is defined by... 

In Section 19.2 we treated the phase problem by choosing a reference system (for instance, water) to which the concentrations of the chemicals in other phases are related by equilibrium distribution coefficients such as the Henry s law constant. Here we employ the same approach. The following derivation is valid for an arbitrary wall boundary with phase change. The mixed system B is selected as the reference system. In order to exemplify the situation, Fig. 19.9 shows the case in which system A represents a sediment column and system B is the water overlying the sediments. This case will be explicitly discussed in Box 19.1. 

Transfer velocity across gaseous boundary layer typically between 0.1 and 1 cm s"1 (up to 5 cm s 1, see Fig. 20.2). Km is the nondimensional liquid/gas distribution coefficient (for air-water interface inverse nondimensional Henry s law coefficient, i.e., Jfr w) with typical values between 10-3 and 103. DA is the molecular gaseous diffusivity, typical size 0.1 cm2s . 

Of course, the first question is, where must the system go This is formally answered by chemical thermodynamics in terms of equilibrium-distribution coefficients or Henry s Law constants. For our purposes these are well described from the elementary viewpoint by MacDougall (8) and from the viewpoint of practical application by Norman (9). 

Selection of Solubility Data Solubility values are necessary for design because they determine the liquid rate necessary for complete or economic solute recovery. Equilibrium data generally will be found in one of three forms (1) solubility data expressed either as weight or mole percent or as Henry s law coefficients (2) pure-component vapor pressures or (3) equilibrium distribution coefficients (K values). 

Henry s law constant for solute in feed liquid phase Henry s law constant for solute in solvent liquid phase equilibrium constant distribution coefficient molecular weight of feed without solute molecular weight of solvent without solute interfacial surface tension from Fig. 7.12, dyn/cm partial pressure of solute, atm raffinate density, column section 1, lb/ft3 entering solvent, lb... 

Hs = Henry s law constant for solute in solvent liquid phase Kd = equilibrium constant distribution coefficient... 

We have looked at four KD equilibrium resources laboratory data, triangular equilibrium data from publications, Henry s law constants, and operating field data. All four are reliable data sources if applied with limitations as described. All can be applied to the rectangular equilibrium curve (the distribution coefficient equilibrium curve) as shown in Fig. 7.2, which includes a listing of laboratory data for the extraction process shown. Please notice the data table in the boxed area of columns... 

Equation (75) may be derived more simply by using an alternative measure of escaping tendency, the partial pressure of i above the solution. This partial pressure must be equal above the two solutions between which the distribution of i is equilibrated (Problem 18). Extraction is not a colligative property because it is the solute, not the solvent, that is distributing between the two phases. The distribution coefficient, like the Henry s law constants, depends on the identity of the solutes, as well as that of the solvent. 

Vr(csi) is the analyte retention as a function of the eluent concentration, Vo is the total volume of the liquid phase in the column, y Cei) is the volume of adsorbed layer as a function of eluent composition, Kp(cei) is the distribution coefficient of the analyte between the eluent and adsorbed phase, S is the adsorbent surface area, and is the analyte Henry constant for its adsorption from pure organic eluent component (adsorbed layer) on the surface of the bonded phase. 

Material balance calculations on separation processes follow the same procedures used in Chapters 4 and 5. If the product streams leaving a unit include two phases in equilibrium, an equilibrium relationship for each species distributed between the phases should be counted in the degree-of-freedom analysis and included in the calculations. If a species is distributed between gas and liquid phases (as in distillation, absorption, and condensation), use tabulated vapor-liquid equilibrium data, Raoult s law, or Henry s law. If a solid solute is in equilibrium with a liquid solution, use tabulated solubility data. If a solute is distributed between two immiscible liquid phases, use a tabulated distribution coefficient or equilibrium data. If an adsorbate is distributed between a solid surface and a gas phase, use an adsorption isotherm. 

The quantities in brackets represent activies of ions in solution and of components in the solid phase. Application of the defining equation directly would require knowing activity coefficients for the ions in solution and also the Henry s law coefficient for the trace carbonate in solid solution. A practical approach is to rewrite equation (13) in terms of an effective or empirical distribution coefficient... 

Each term on right side of Equation 2.2 represents an individual resistance as depicted in Figure 2.4. Hollow fiber diameters are rfoux and The term H is the Henry coefficient (liquid-gas equilibrium constant) for the species in question. In the case of liquid-liquid contact, the term H in Equation 2.2 should be replaced by mo, the equilibrium distribution coefficient between tube side liquid and shell side liquid. 

In a type 1 extraction system, the distribution coefficient is functionally similar to a Henry s law constant in an air stripping operation. For most organic chemicals of environmental concern, the distribution coefficient between an organic phase and water may be assumed to be a constant due to the generally low solubility of organics in water. 

Since the impurities in SoG-Si feedstock are normally multidimensional in nature, it is important to estimate the influence of other impurities on the distribution coefficient of one impurity in pure Si. A simple relation has been derived for the effects of secondary impurities, j, on the distribution coefficient of i in pure Si, if the Henry s activity coefficients, 7, are available ... 

In the simplest case the adsorption isotherm is of the Langmuir type with a steep slope at the initial part and reaching a saturation value at higher amounts of adsorbed solute. The slope of the isotherm corresponds to the distribution coefficient K, discriminating two parts of the isotherm the linear and nonlinear parts. In the linear range K is equal to the Henry constant. For the nonlinear part K becomes... 

Where H is Henry s Law constant for a VOC in water, atm/unit concentration in the aqueous phase P is the total pressure, atm and y is the VOC mole fraction in the gas phase. The product P y is the partial pressure of the VOC above the liquid phase. Henry s Law constants are specific to both the solute and the solvent. The higher the value of H q, the easier it is to remove the VOCs from the aqueous phase. In the nonvolatile solvent, the Henry s Law constant of the VOC (H jj = H q/D) is lowered relative to water due to the greater affinity of the organic solvent for the VOC as measured by the large distribution coefficient. Substituting equation 2 into equation 3 yields ... 

As shown in Table n, chloroform and carbon tetrachloride have about the same Henry s Law constant above oil, even though carbon tetrachloride is considerably more volatile above water than chloroform. The high distribution coefficient for carbon tetrachloride significantly reduces the Henry s Law constant for the oil phase. The relatively high partial pressure of tetrachloroethylene above water is significantly reduced in oil due to the large distribution coefficient... 

AT Vapor-liquid distribution coefficient kfi Henry s law constant... 

Insofar as the distribution coefficient, Kp- or Dp is constantf and not a function of composition, then Nemst s law [35] is obeyed, especially for nomeactive, simple systems. The lack of a composition dependence may be taken as an indication that a particnlar system is not reactive. In snch cases, the distribution of solute between the two phases is primarily determined by its solnbility in each phase hence Henry s law and/or the Lewis and Randall rule apply. 

---