Liquid absorption solubility parameter

Selection of the solvent select lowest molai mass liquid whose solubility parameters are similar to those of target species in the gas. Choose a solvent in which the target species are highly soluble. >700 mg/g solvent Henry s law constant <10 kPa/mol fraction or HTU(/HTUi) Fi/Fg) prts,s,urt, kPa/Henry s constant) >20 then gas phase controls mass transfer. This is most likely for many absorptions. 

Polyformaldehydes (polyoxymethylenes, polyacetals) These are physically similar to general purpose nylons but with greater stiffness and lower water absorption. There are no solvents, but swelling occurs in liquids of similar solubility parameter. Poor resistance to u.v. light and limited thermal stability are two disadvantages of these materials. 

When a polymer absorbs a liquid or gas, that results in plasticization or swelling of the thermoset network, physical corrosion has taken place. For a cross-linked thermoset, swelling caused by solvent absorption will be at a maximum when the solvent and polymer solubility parameters are exactly matched. 

It might be possible to absorb or scrub the methane from Streams 8 and 17 into a hydrocarbon liquid. In order to determine which liquids, if any, are suitable for this process, we must conpare the solubility parameters for both methane and hydrogen in the different liquids. This information is available in Walas nil. Because of the low boiling point of methane, it would require a low tenperature and high pressure for effective absorption. 

The swelling, crazing, and cracking behavior of PMMA, PVC, and PSU in contact with some 70 different liquids was analyzed by Vincent and Raha [123]. They considered not only the solubility parameter 65 but also the value of the hydrogen bonding parameter Hqd based on the displacement of the OD infra-red absorption band in CH3OD in presence of the particular liquid and benzene. Better (but still no unique), correlation between the mode of failure and 63 and Hqd was obtained. 

In this case it is assumed that a pure gas A is being absorbed in a solvent eontaining a chemically inert component B. Both the solvent and B are not volatile and the fraction of A in the liquid bulk equals zero. The binary mass transfer coefficient Kij between A and the solvent in eq. (4) is given a typical value of 1 X lO" m/s, whereas the total concentration of the liquid Cr is set to 1 x 10 mol/m, also a typical value. Parameters to be chosen are the solubility of A, x i, the fraction of B in the solvent Xg, the mass transfer coefficient between A and B, K/ g and the mass transfer coefficient between B and the solvent, Kg. The results of the calculations are presented in Table 1. Since both the solvent and component B possess a zero flux. Kgs has no influence on the mass transfer process and has therefore been omitted. The computed absorption rate has been compared with the absorption rate obtained from analytical solutions for the following cases. 

Both the mass transfer kinetic parameters (diffusion in the phases, D, D j, surface renewal frequency, s) and chemical reaction rate constants (kg, kj) strongly influence enhancement of the absorption rate. The particle size, dp, the dispersed liquid holdup, e and the partition coefficient, H can also strongly alter the absorption rate [42-44,46,48]. Similarly, the distance of the first particle from the gas-liquid interface, 6q is an essential factor. Because the diffusion conditions are much better in the dispersed phase (larger solubility and, in most cases, larger diffusivity, as well) the absorption rate should increase with the decrease of the (5g value. 

Liquid-Phase Transfer. It is difficult to measure transfer coefficients separately from the effective interfacial area thus data is usually correlated in a lumped form, eg, as k a or as Hv These parameters are measured for the liquid film by absorption or desorption of sparingly soluble gases such as 02 or C02 in water. The liquid film resistance is completely controlling in such cases, and k a may be estimated as KQLa since xi x (Fig. 4). This is a prerequisite because the interfacial concentrations would not be known otherwise and hence the driving force through the liquid film could not be evaluated. 

Arguably the most important parameter for any surfactant is the CMC value. This is because below this concentration the monomer level increases as more is dissolved, and hence the surfactant chemical potential (activity) also increases. Above the CMC, the monomer concentration and surfactant chemical potential are approximately constant, so surfactant absorption at interfaces and interfacial tensions show only small changes with composition under most conditions. For liquid crystal researchers, the CMC is the concentration at which the building blocks (micelles) of soluble surfactant mesophases appear. Moreover, with partially soluble surfactants it is the lowest concentration at which a liquid crystal dispersion in water appears. Fortunately there are well-established simple rules which describe how CMC values vary with chain length for linear, monoalkyl surfactants. From these, and a library of measured CMC values (35-38), it is possible to estimate the approximate CMC for branched alkyl chain and di- (or multi-) alkyl surfactants. Thus, most materials are covered. This includes the gemini surfactants, a new fashionable group where two conventional surfactant molecules are linked by a hydrophobic spacer of variable length (38). 

By suitably choosing the solubility, the concentration of the reactant and the rate of reaction, either the mass transfer coefficients, or the interfacial area or both groups of parameters can be deduced from the overall rate of absorption (lA). Generally but not always, a steady flow of each phase through the reactor is assumed. Indeed the competition between the phsyical and chemical kinetics at the level of mass transfer between gas and liquid (the mass transfer reaction regime where the reaction belongs) may allow for the choice of the type of gas-liquid contactor (I). This is clearly shown in Fig. I that represents schematically the concentration profiles for A and B on each side of the interface. 

The parameters D and or cr can also be determined experimentally by immersion tests. In an immersion test a geomembrane test specimen is immersed in a liquid ehemieal or its aqueous solution with a specified constant concentration cq. Absorption of the chemical by the test specimen with a mass G is measured by its gradual increase in mass AG f). If the solubility of the ehemieal in the geomembrane material is limited, a saturation value for increase in mass AG(< ) develops over the course of time. In a diffusion process obeying Pick s laws with a constant diffusion coefficient D, the slope of mass change as a function of time t is proportional to (Z)t) " up to about 2/3 of the saturation value. The proportionality factor depends on the shape of the test specimen. It holds for a plate with a large area compared to its thickness d (Crank and Park 1968) ... 

To design such a process, the McCabe-Thiele method may be used to determine the number of theoretical separation stages, as examined in Sections 3.3.2-3.3.4 for distillation, absorption (gas scrubbing), and liquid-liquid-extraction. Thus, we obtain the number of theoretical extraction stages of a countercurrent extraction column based on the equilibrium curve (solubility of extract in the solvent for a given content in the solid) and the operating line. The latter depends on the extract content of the solid feed and residue, and on the in- and outlet extract concentration in the solvent The extract content of the feed is fixed, and the value of the residue is specified by the required degree of extraction. The inlet content of the extract in the solvent is also fixed, as either pure solvent is used or the value is specified by separation of the extract from the used solvent after the extraction. Therefore, the only parameter that is left is the outlet concentration of the extract in the solvent, which depends on the ratio of the solvent flow to the feed rate of the solid feedstock (mass balance). 

The performance of a guest-host LCD is greatly dependent on the dye parameters (such as UV stability, solubility, order parameter, absorption, etc.), the host liquid crystal properties (such as viscosity, dielectric anisotropy, birefringence, order parameter, temperature range, stability, etc.), and the compatibility of the dye and the host [12-17, 42-58]. 

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