Two-phase separator

A membrane is defined as an intervening phase separating two phases forming an active or passive barrier to the transport of matter. Membrane processes can be operated as (1) Dead-end filtration and (2) Cross-flow filtration. Dead-end filtration refers to filtration at one end. A problem with these systems is frequent membrane clogging. Cross-flow filtration overcomes the problem of membrane clogging and is widely used in water and wastewater treatment. 

Richter, H. J., 1983, Separated Two-Phase Flow Model, Application to Critical Two-Phase Flow, Int. J. Multiphase Flow 9(5) 511-530. (5)... 

When two condensed phases A and B are brought into contact, as shown in Fig. 4-6, the surface charge, o, the inner potential, <, and the outer potential, tf(o), of the initially separate two phases are changed to values characteristic of the joined solid A/B on the other hand, the surface potential, Xcd ), at the free surface of each phase remains unchanged except, of course, for the joining surface. The outer potential, if, of the free surface of the two phases is given by Eqn. 4-2, whether or not the two phases are in contact ... 

Adhesion is created by primary and secondary forces according to the theory of adsorption interaction. This theory is applied the most widely for the description of interaction in particulate filled or reinforced polymers [30]. The approach is based on the theory of contact wetting and focuses its attention mainly on the influence of secondary forces. Accordingly, the strength of the adhesive bond is assumed to be proportional to the reversible work of adhesion (W ), which is necessary to separate two phases with the creation of two new surfaces. 

Why is it that insects like beetles can walk on water Why do the bristles of a brush immersed in water cling together as the brush is pulled out Phenomena such as these arise because of a special property of interfaces that separate two phases. Let us consider another example first. Everyone has had the experience of pouring more beverage into a cup or glass than that container could hold. In addition to the spills this causes, such an experience provides an opportunity to observe surface tension. Most liquids can be added to a vessel until the liquid surface bulges above the rim of the container. The liquid behaves as if it had a skin that prevents it —up to a point —from overflowing. Stated technically, a contractile force, which tends to shrink the surface, operates around the perimeter of the surface. This is what we mean when we talk about the surface tension of a liquid. All phase boundaries behave this way, not just liquid surfaces however, the evidence for this is more apparent for deformable liquid surfaces. 

WA Thermodynamic work of adhesion required to separate two phases in an inert medium... 

Elementary Theory. The theory of the bulging method assumes that the maximum pressure is reached when it is just hemispherical (I). Implicit in the theory, an interfacial tension (yi) exists in every thin film separating two phases (liquid, solid, or gaseous). Further, the interfacial... 

Interfaces separate two phases such as a and / . An interface reaction can mean 1) component fluxes cross the stationary interface or 2) the interface moves due to a chemical reaction between the phases a and / at the interface (phase boundary). Catalytic reactions are excluded from this discussion. 

An interface is the area which separates two phases from each other. If we consider the solid, liquid, and gas phase we immediately get three combinations of interfaces the solid-liquid, the solid-gas, and the liquid-gas interface. These interfaces are also called surfaces. Interface is, however, a more general term than surface. Interfaces can also separate two immiscible liquids such as water and oil. These are called liquid-liquid interfaces. Solid-solid interfaces separate two solid phases. They are important for the mechanical behavior of solid materials. Gas-gas interfaces do not exist because gases mix. 

Anytime a generic boundary layer or semipermeable barrier separates two phases or zones at different electrolyte concentrations a junction ( )) or a Donnan (En) potential is established, the value of which can be estimated in accordance with Boniardi et al. (1996), Prentice (1991), and Vetter (1967). 

Two current approaches to explain the process of micellization are law of mass action and phase separation. In the law of mass action, micellization is treated as an equilibrium process between the progressive association and dissociation of the monomers (Figure 4.20). In phase separation, two phases (i.e., surfactant monomers in aqueous phase and micelles) are in equilibrium above the c.m.c. In this model, micellization takes place as a one-step process. 

Interface — In chemistry and physics interface means the two-dimensional plane separating two phases. The general thermodynamic requirement for the stability of an interface between two phases is a positive Gibbs energy of formation, because otherwise the interface... 

Membrane — Thin, typically planar structure or material separating two phases. It has finite volume. Membranes can selectively control the mass transport between different phases. Some membranes exert ion selectivity. In this case the -> membrane potential arises. Refs. [i] Koryta / (1982) Ions, electrodes and membranes. Wiley, New York [ii] Buck RP, Lindner E (1994) Pure Appl Chem 66 2527 [iii] http /www. iupac.org/goldbook/M067878... 

The effect of this is that the charged defects are independent of one another and can form domain walls that separate two phases of opposite orientation and identical energy. These are called solitons and can sometimes be neutral. Solitons produced in polyacetylene are believed to be delocalised over about 12 CH units with the maximum charge density next to the dopant counterion. The bonds closer to the defect show less amount of bond alternation than the bonds away from the centre. 

Quantum phenomena at the vacuum interface have been postulated in analogy with known effects at physico-chemical interfaces. To be consistent, special properties of the latter are therefore implied. A physical interface is the boundary surface that separates two phases in contact. These phases could be two solid phases, two liquid phases, solid-liquid, solid-gas or liquid-gas phases. What they all have in common is a potential difference between the two bulk phases. In order to establish equilibrium at the interface it is necessary that rearrangement occurs on both sides of the interface over a narrow region. Chemical effects within the interfacial zone are unique and responsible for the importance of surfaces in chemical systems. At the most fundamental level the special properties of surfaces relate to the difference between isolated elementary entities and the same entities in a bulk medium, or condensed phase. 

This method allows for the accurate determination of K i only within the -1000 to +1000 region or approximately within six orders of magnitude span. These experiments could be complicated by solubility and equilibration kinetics and the properties of a substance. For example, if a studied compound has a property of nonionic surfactant, it will be mainly accumulated at the water-organic interface, and shaking of this two-phase system will create a stable emulsion difficult for analytical sampling. The ultracentrifugation at speed of 14,000 rpm for 15-20 min can be enough in most cases to separate two phases. Actual equilibration of the system is tested by several measurements of the equilibrium concentration at different time intervals. 

The isotherm (plot of pressure versus volume) at the temperature Tc plays a special role in the theory of the states of matter. An isotherm behaves in accordance with the gas laws slightly below T. At certain pressure, a liquid condenses from gaseous state and is distinguishable from it by the presence of a visible interface. If, however, the compression takes place at a surface separating two phases does not appear and the volumes at each end of the horizontal part of the isotherm have merged to a single point, critical point of the gas. The temperature, pressure, and molar volume at the critical point are called the critical temperature T, critical pressure P, and critical molar volume of the substance respectively. Collectively,... 

A membrane can essentially be defined as a barrier that separates two phases and selectively restricts the transport of various chemicals. It can be homogenous or heterogeneous, symmetric or asymmetric in structure, solid or liquid, and can carry a positive or negative charge, or be neutral or bipolar. Transport across a membrane can take place by convection or by diffusion of individual molecules, or it can be induced by an electric field or concentration, pressure or temperature gradient. The membrane thickness can vary from as little as 100 p.m to several millimeters. 

The membrane is essentially a barrier, that separates two phases and restricts transport of various chemicals in a selective maimer. A membrane can be homogeneous or heterogeneous, symmetric or asymmetric, sofid or liquid it can carry positive or negative charges or can be neutral. Transport through a membrane can be affected by convection or by diffusion of individual molecules, and induced by the chemical gradient or electrical gradient. 

According to a definition given by the European Membrane Society, the membrane is an intervening phase separating two phases and/or acting as an active or passive barrier... 

The correct term to describe the force required to separate two phases in a centrifuge is relative centrifugal force (RCF), also called relative centrifugal field. Units are expressed as number of times greater than gravity (e.g., 500 X g). 

Hollow fiber contactors use membranes to separate two phases and transport is due to diffusion, chemical reaction, or chemical potential rather than pressure. The main examples of hollow fiber contactors are found in dialysis, gas adsorption/deadsorption, and solvent extraction. Use of hydrophilic and hydrophobic fiber materials controls the wetting of the pores. Typically, the phase that has higher mass transfer is allowed to wet the pores in order to minimize overall mass transfer resistance. 

When the temperature of the solution is again lowered, we can observe that the solution which was limpid and transparent becomes turbid. Then, if the temperature remains constant, a meniscus appears after some time and separates two phases in the sample. We have demixtion, and this is the second characteristic effect. Precise measurements of the demixtion temperature have been made, in particular by the Japanese school. 

The predictions of three-phase equilibria considered so far were done as two separate two-phase calculations. Although applicable to the examples here, such a procedure cannot easily be followed in a three-phase flash calculation in which the temperature or pressure of a mixture of two or more components is changed so that three phases are formed. In this case the equilibrium relations and mass balance equations for all three phases must be solved simultaneously to find the compositions of the three coexisting phases. It is left to you (Problem 11.3-7) to develop the algorithm for such a calculation. 

Here we shall only consider some of the basic principles. We have already seen (Chapter 5, page 73) that the pressure difference across a curved surface separating two phases a and /i (Figure 12.2) is given by the Laplace equation. In the ease ol a soap film this is... 

The work of adhesion IKjj needed to separate two phases A and B (see Chapter 3) is given by... 

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