Immiscible liquids and solids

The interfacial area between gases and hquids, immiscible liquids, and solids and hquids may be enlarged or reduced by these viscous and inertia forces when interacting with interfacial forces such as surface tension. 

The separation of immiscible liquids and solids is performed by gravity separation in API Separators (or equivalent) or even the wastewater stripper feed drum. The purpose is to remove as much of the nondissolved organics from the wastewater as possible prior to biological treatment. Settleable solids are also removed by air flotation after stripping to further reduce the load on the biological treatment unit. 

Preliminary discussion on reaction equilibria involving gases together with immiscible liquids and solids... 

Wastewater can be treated by several physical processes. In some cases, simple density separation and sedimentation can be used to remove water-immiscible liquids and solids. Filtration is frequently required, and flotation by gas bubbles generated on particle surfaces may be useful. Wastewater solutes can be concentrated by evaporation, distillation, and membrane processes, including reverse osmosis, hyperfiltration, and ultrafiltration. Organic constituents can be removed by solvent extraction, air stripping, or steam stripping. 

The term three-phase fluidization requires some explanation, as it can be used to describe a variety of rather different operations. The three phases are gas, liquid and particulate solids, although other variations such as two immiscible liquids and particulate solids may exist in special applications. As in the case of a fixed-bed operation, both co-current and counter- current gas-liquid flow are permissible and, for each of these, both bubble flow, in which the liquid is the continuous phase and the gas dispersed, and trickle flow, in which the gas forms a continuous phase and the liquid is more or less dispersed, takes place. A well established device for countercurrent trickle flow, in which low-density solid spheres are fluidized by an upward current of gas and irrigated by a downward flow of liquid, is variously known as the turbulent bed, mobile bed and fluidized packing contactor, or the turbulent contact absorber when it is specifically used for gas absorption and/or dust removal. Still another variation is a three-phase spouted bed contactor. 

Centrifugation, for immiscible liquid or solid separation and recovery... 

Complex heterogeneous process (two immiscible liquids and decomposing solid) Air Products Chemicals Latshaw (1994)... 

Fig. 1. Schematic diagram illustrating the analogies between dispersion of immiscible liquids and dispersed solids.

Large-scale ultrasonic irradiation is extant technology. Liquid processing rates of 200 liters/minute are routinely accessible from a variety of modular, in-line designs with acoustic power of several kW per unit (83). The industrial uses of these units include (1) degassing of liquids, (2) dispersion of solids into liquids, (3) emulsification of immiscible liquids, and (4) large-scale cell disruption (74). While these units are of limited use for most laboratory research, they are of potential importance in eventual industrial application of sonochemical reactions. 

Other uranium binary systems de-mixing in the liquid state are U-Pb and U-Bi and several uranium-lanthanides systems which are characterized by nearly complete immiscibility in the liquid and solid state. 

In Fig. 1.2, phase transformations are pnt into their context of physical processes used for separation of mixtures of chemical compounds. However, the figure has been drawn asymmetrically in that two Uqnids (I and II) are indicated. Most people are familiar with several organic Uqnids, Uke kerosene, ether, benzene, etc., that are only partially miscible with water. This lack of miscibility allows an equilibrium between two liquids that are separated from each other by a common phase boundary. Thus the conventional physical system of three phases (gas, liquid, and solid, counting all solid phases as one), which ordinarily are available to all chemists, is expanded to four phases when two immiscible liquids are involved. This can be of great advantage, as will be seen when reading this book. 

Three-Phase Transformations in Binary Systems. Although this chapter focuses on the equilibrium between phases in binary component systems, we have already seen that in the case of a entectic point, phase transformations that occur over minute temperature fluctuations can be represented on phase diagrams as well. These transformations are known as three-phase transformations, becanse they involve three distinct phases that coexist at the transformation temperature. Then-characteristic shapes as they occnr in binary component phase diagrams are summarized in Table 2.3. Here, the Greek letters a, f), y, and so on, designate solid phases, and L designates the liquid phase. Subscripts differentiate between immiscible phases of different compositions. For example, Lj and Ljj are immiscible liquids, and a and a are allotropic solid phases (different crystal structures). 

Rates of gas-liquid, liquid-liquid, and solid-liquid mass transfer are important and often control the overall rates in bioprocesses. For example, the rates of oxygen absorption into fermentation broth often control the overall rates of aerobic fermentation. Ihe extraction of some products from a fermentation broth, using an immiscible solvent, represents a case of liquid-liquid mass transfer. Solid-liquid mass transfer is important in some bioreactors using immobilized enzymes. 

SURFACE CHEMISTRY. This topic deals with the behavior of matter, where such behavior is determined largely by forces acting at surfaces. Since only condensed phases, i.e., liquids and solids, have surfaces, studies in surface chemistry require that at least one condensed phase be present in the system under consideration, The condensed phase may be of any size ranging from colloidal dimensions to a mass as large as an ocean. Interactions between solids, immiscible liquids, liquids and solids, gases and liquids, gases and solids, and different gases on a surface fall within the province of surface chemistry. 

The mechanisms of mixing of miscible and immiscible liquids and soft agglomerates are depicted in Fig. 7.5, and that of hard solid agglomerates in Fig. 7.6. In the former, elongational and shear stretching is the dominant mechanism, whereas, the latter is shear stress dominated. 

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