Immiscibility, zones

Most of these properties can be examined in the effective conditions in wfaidi the solvent is used, particularly temperature, which affects the solvent power, selectivity, the immiscibility zone etc. (see diagram a of Fig. 4.4). 

One of the most serious obstacles in the phase equilibrium studies of polymer blends is the viscosity of the system. At temperahires limited by the degradation the self-diffusion coefficient of macromolecules is of the order of magnitude 10 to 10 m /s [Kausch and Tirrell, 1989]. As a result the phase separation is slow. To accelerate the process a low speed centrifuge, the centrifugal homogenizer (CH), with PICS has been used [Koningsveld et al, 1982]. In short, centrifugation within the immiscibility zone permits determination of binodal and critical points, while the use of PICS mode allows location of the spinodal. 

When an impeller is rotated in an agitated tank containing two immiscible Hquids, two processes take place. One consists of breakup of dispersed drops due to shearing near the impeller, and the other is coalescence of drops as they move to low shear zones. The drop size distribution (DSD) is decided when the two competing processes are in balance. During the transition, the DSD curve shifts to the left with time, as shown in Figure 18. Time required to reach the equiHbrium DSD depends on system properties and can sometimes be longer than the process time. 

Schwille, F., 1985, Migration of Organic Fluids Immiscible in Water in the Unsaturated and Saturated Zones In Proceedings of Second Canadian/American Conference on Hydrogeology (edited by B. Hitchon and M. Trudell), Banff, Alberta. 

In addition to water, NAPLs, such as petroleum, oils, tars, and biological fluids, are often present in the subsurface. When more than one fluid is present, there is a need to describe how well they mix, referred to as their miscibility. Water and vegetable oil are immiscible fluids. Many of the NAPLs are immiscible with water and will occur as separate fluid bodies, droplets, zones, etc. in the subsurface environment. 

Three Phase —Two Immiscible Liquids and Air in the Unsaturated Zone... 

Faust, C. R., Guswa, J. H., and Mercer, J. W., 1989, Simulation of Three Dimensional How of Immiscible Fluids within and below the Unsaturated Zone Water Resources Research, Vol. 25, No. 12, pp. 2449-2464. 

Schwille, F., 1984, Migration of Organic Fluids Immiscible with Water in the Unsaturated Zone Pollutants in Porous Media In Ecological Studies (edited by B. Yarn, G. Dagan, and J. Goldshmidt), Springer-Verlag, New York, pp. 27-48. 

Since hydrocarbon and water are immiscible fluids, free-phase recoverable LNAPL can simplistically be viewed as being perched on the capillary fringe above the actual water table with the understanding that what is being referred to as actual NAPL thickness is what one could perceive as being equivalent to the approximate thickness of that portion of the zone of hydrocarbon saturation that is considered mobile. The physical relationships that exist are illustrated in Figure 6.5. This discrepancy can be a result of one or a combination of factors or phenomena. Some of the more common factors or phenomena are schematically shown in Figure 6.6 and include ... 

It receives the two streams of immiscible phases and combines them into a single flow with alternate and regular zones of the two phases (solvent segmenter). 

Fig. 5.7 Illustration of a water immiscible liquid trapped in the vadose zone immediately after a spill. The dashed line represents the water table region (Schwille 1984)...

Schwille F (1984) Migration of organic fluids immiscible with water in the unsaturated zone phenomenon. In Yaron B, Dagan G and Goldschmid J (eds) Pollutants in porous media. Springer,... 

Contaminant redistribntion in the subsurface, as a result of transport (in dissolved form, as an immiscible-with-water phase, or adsorbed on colloids) is discussed in Part IV. These phenomena do not occur in a static domain, and contaminants are redistributed, usually by flowing water, from the land surface, through the partially saturated subsurface down to the water table, and within the fully saturated aquifer zone. After a basic presentation of water movement in the subsurface environment (Chapter 9), we focus on transport of passive contaminants (Chapter 10) and reactive contaminants (Chapter 11). 

Details of this experiment may be found in Ref. 1. The interfacial polymerization method to prepare polyamides involves the reaction of a diacid dichloride with a diamine between two immiscible liquids as the reaction zone (with or without stirring). The method is useful where the reactants are sensitive to high temperature and where the polymer degrades before the melt point is reached (as in melt polymerization techniques). 

Immiscible phase — Contaminants are present as nonaqueous-phase liquids (NAPLs), primarily in unsaturated zones. 

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