Immiscible phases

The pelobischofite-surfactant mixtures emulsifying ability was estimated by measurements of the phase immiscibility time for standard oil in water emulsion. The measurements of emulsion particles size were also carried out. The experiments showed the essential increase of phase immiscibility time with the pelobischofite contents increase. Some decrease in average particles size of standard emulsion was also registered. The emulsifiability of other magnesium containing preparations was at least twice worse. 

Table 7.89 lists the main characteristics of MDHPLC (see also Table 7.86). In MDHPLC the mobile-phase polarity can be adjusted in order to obtain adequate resolution, and a wide range of selectivity differences can be employed when using the various available separation modes [906]. Some LC modes have incompatible mobile phases, e.g. normal-phase and ion-exchange separations. Potential problems arise with liquid-phase immiscibility precipitation of buffer salts and incompatibilities between the mobile phase from one column and the stationary phase of another (e.g. swelling of some polymeric stationary-phase supports by changes in solvents or deactivation of silica by small amounts of water).

Separation of two liquid phases, immiscible or partially miscible liquids, is a common requirement in the process industries. For example, in the unit operation of liquid-liquid extraction the liquid contacting step must be followed by a separation stage (Chapter 11, Section 11.16). It is also frequently necessary to separate small quantities of entrained water from process streams. The simplest form of equipment used to separate liquid phases is the gravity settling tank, the decanter. Various proprietary equipment is also used to promote coalescence and improve separation in difficult systems, or where emulsions are likely to form. Centrifugal separators are also used. 

DNAPLs have higher densities than water, most between 1 and 2 g/mL, some are near 3 g/mL, for example, bromoform, which has a density of 2.89 g/mL. They have limited water solubilities, and are usually found as the free-phase immiscible with water or as residuals trapped by soil. Most DNAPLs are volatile or semivolatile Pankow82 has listed information on their physical and chemical properties, such as molecular weight, density, boiling points, solubility in water, vapor pressure, sediment/water partition coefficient, viscosity, Henry s law constant, and so on (see Tables 18.8 and 18.9). 

This section describes catalytic systems made by a heterogeneous catalyst (e.g., a supported metal, dispersed metals, immobilized organometaUic complexes, supported acid-base catalysts, modified zeolites) that is immobilized in a hydrophilic or ionic liquid catalyst-philic phase, and in the presence of a second liquid phase—immiscible in the first phase—made, for example, by an organic solvent. The rationale for this multiphasic system is usually ease in product separation, since it can be removed with the organic phase, and ease in catalyst recovery and reuse because the latter remains immobilized in the catalyst-philic phase, it can be filtered away, and it does not contaminate the product. These systems often show improved rates as well as selectivities, along with catalyst stabilization. 

It is known that, in a water phase, immiscible liquids such as gasoline or other petroleum products may form multicomponent droplets of various forms and sizes, under dispersive conditions. These droplets are transported by convection and diffusion, which contributes to the contamination of fresh water systems. However, during droplet transport, more volatile substances partition to the gas phase at the droplet surface, leaving less volatile material that volatilizes more slowly. More volatile material still exists in the droplet interiors, and it tends to diffuse toward the surface because of concentration gradients created by prior volatilization. Different components in a droplet have different volatilization rates, which may vary significantly during droplet transport, and as a result, the contamination of fresh water is affected accordingly. 

The addition of a dispersed liquid phase (immiscible organic solvent) changes the rate of transfer of the solute gas across the boundary layer. Physical properties (density, viscosity, gas solubility and gas diffusivity) of the liquid mixture are changed and the gas-liquid characteristics (possible pathway for mass transfer and gas-liquid interfacial area) can be changed owing to the interfacial proper-... 

HPL/PMMA Blends. Blend Structure. All blends of HPL and PMMA revealed a two-phase (immiscible) morphology regardless of solvent, weight fraction, molecular weight (of PMMA), or method of preparation (9). Extruded HPL/PMMA blends exhibited a less obvious two-phase morphology (9), and this was attributed to differences in the rate of vitrification (9). 

Factors leading to insolubility in water were discussed in Section 10.2.1.1. Provided they are not highly polymerized, such hydrophobic substances are generally soluble in non-aqueous solvents. In a two-phase system formed by an aqueous phase and a second phase immiscible with it a solute will partition between them until its activity is the same in both. The Nernst partition isotherm quantifies this relationship in the form... 

We assume that the fluid component and the adsorbate in the fluid phase, present in a very low concentration, have the same kinematics given by the common velocity field Vf, so that there is no flux of molecular diffusion in the fluids. Thus we can reduce to consider an atypical two-phase immiscible mixture of a solid with big pores, of subscript s, and a particular bi-component fluid, of subscript / (see 8.4 of [11]). 

Suppose T = 300 K and P = 5 bar. The preceding condition then requires < 12 > 9977 cm3 mol-1 for vapor-phase immiscibility. Such large positive values for < 12 are unknown for real mixtures. (Examples of gas/gas equilibria are known, but at conditions outside the range of applicability of the two-term virial EOS.)... 

Finally, in the cool-down section, in which the process stream temperatures are reduced below the critical temperature of water for product separation and recovery, precipitated inorganics may redissolve, but gas phase immiscibility will rise. 

Much of the SO3 is present at the clinkering temperature in a separate liquid phase, immiscible with the main clinker liquid. The alkali cations are distributed between the two liquids and the alite and belite. During cooling, some redistribution of alkali cations and sulphate ions between the liquids may be expected to occur, the sulphate liquid finally solidifying below 900 C to yield alkali or potassium calcium sulphates. 

Two early studies of the phase equilibrium in the system hydrogen sulfide + carbon dioxide were Bierlein and Kay (1953) and Sobocinski and Kurata (1959). Bierlein and Kay (1953) measured vapor-liquid equilibrium (VLE) in the range of temperature from 0° to 100°C and pressures to 9 MPa, and they established the critical locus for the binary mixture. For this binary system, the critical locus is continuous between the two pure component critical points. Sobocinski and Kurata (1959) confirmed much of the work of Bierlein and Kay (1953) and extended it to temperatures as low as -95°C, the temperature at which solids are formed. Furthermore, liquid phase immiscibility was not observed in this system. Liquid H2S and C02 are completely miscible. 

One of the interesting features of the system hydrogen sulfide + methane is liquid-phase immiscibility. The H2S-rich and CH4-rich liquids are immiscible. However, this occurs at temperatures well below those of interest in acid gas injection. Unusual looking phase diagrams are often obtained for mixtures rich in H2S and CH4 because the algorithms typically are not designed for multiple... 

At temperatures below the critical point of C02 (31°C), C02 and TEG exhibit liquid phase immiscibility. This can be seen for the 25°C isotherm shown on figure 7.2. At temperatures greater than 31°C, C02 + TEG mixtures have a miscibility gap. Thus, it is possible to dehydrate C02 at high pressures. 

Extraction is the process of transferring a substance from a solid to a liquid phase or from a liquid to another liquid phase (immiscible with the former). From a practical viewpoint, the process can be achieved by leaching, which is transfer of compoimds from a solid phase to a solution (solid-liquid extraction, SEE) or by extraction via direct (liquid-liquid extraction, LEE) or indirect (SPE or solid phase microextraction, SPME) transfer of a substance from one liquid phase to another [75]. The efficiency of the extraction process is expressed as the percentage of extraction, which takes into accoimt the affinity of the investigated compoimds for both phases. In practice, a commonly used concept is that of recovery, understood as the degree of transition of a substance from one phase to another, expressed as a percentage. There are multiple methods for determining recovery. They can be divided into two classes ... 

In many of these studies the structure of the middle phase is not established, but it is clearly immiscible in water or oil and its electrical conductivity is closer to water than oil. Phase diagram studies of oil-water-emulsifier systems Ekwall, (5), indicate that surfactant-rich phases immiscible in oil or wa"ter have rodshaped or lamellar micelles with some degree of optical anisotropy or flow birefringence, and these phases have much greater elec-rical conductivity than oil. Figure 1 illustrates that the middle phase composition varies smoothly from a water-rich composition to an oil-rich composition as the emulsifier partition changes from mostly water-soluble to mostly oil-soluble. If lamellar structures are present the relative thickness of oleophilic and hydrophilic layers must vary smoothly from the water-rich compositions to the oil-rich compositions. 

Extraction Partitioning between phases Immiscible liquid... 

Coacervation, a fourth type of aggregation, in which the silica particles are surrounded by an adsorbed layer of material that makes the particles less hydrophilic, but does not form bridges between particles. The particles aggregate as a concentrated liquid phase immiscible with the aqueous phase. 

The computation of phase immiscibility involves two steps, (1) estimating the occurrence of immiscibility, and (2) determining the solubility limits. The first aspect may be solved by observing that the curve AG , is concave in the two liquid phases region. This may be expressed mathematically as ... 

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