Immersion Immiscibility

Interfdci l Composite Membra.nes, A method of making asymmetric membranes involving interfacial polymerization was developed in the 1960s. This technique was used to produce reverse osmosis membranes with dramatically improved salt rejections and water fluxes compared to those prepared by the Loeb-Sourirajan process (28). In the interfacial polymerization method, an aqueous solution of a reactive prepolymer, such as polyamine, is first deposited in the pores of a microporous support membrane, typically a polysulfone ultrafUtration membrane. The amine-loaded support is then immersed in a water-immiscible solvent solution containing a reactant, for example, a diacid chloride in hexane. The amine and acid chloride then react at the interface of the two solutions to form a densely cross-linked, extremely thin membrane layer. This preparation method is shown schematically in Figure 15. The first membrane made was based on polyethylenimine cross-linked with toluene-2,4-diisocyanate (28). The process was later refined at FilmTec Corporation (29,30) and at UOP (31) in the United States, and at Nitto (32) in Japan. 

If two immiscible liquids A and B (i.e., possessing very different 8 values) form two layers when brought together, and an elastomer of similar 6 to A is completely immersed in the (denser) B layer (schematically in Eigure 23.5), nevertheless, the elastomer will evenmaUy swell as if immersed completely in A. This arises because each liquid of an immiscible mixture stiU dissolves a minute amount of the other. At equilibrium, the chemical potential p of A will be the same, whether as pure liquid, dissolved in B, or dissolved in the elastomer. At the same temperature, the same p would apply for the elastomer immersed directly in A. However, the kinetics of absorption will be different, being much slower than... 

FIGURE 23.5 Immiscible Uquids with elastomer sample immersed in lower layer. 

The predominant RO membranes used in water applications include cellulose polymers, thin film oomposites (TFCs) consisting of aromatic polyamides, and crosslinked polyetherurea. Cellulosic membranes are formed by immersion casting of 30 to 40 percent polymer lacquers on a web immersed in water. These lacquers include cellulose acetate, triacetate, and acetate-butyrate. TFCs are formed by interfacial polymerization that involves coating a microporous membrane substrate with an aqueous prepolymer solution and immersing in a water-immiscible solvent containing a reactant [Petersen, J. Memhr. Sol., 83, 81 (1993)]. The Dow FilmTec FT-30 membrane developed by Cadotte uses 1-3 diaminobenzene prepolymer crosslinked with 1-3 and 1-4 benzenedicarboxylic acid chlorides. These membranes have NaCl retention and water permeability claims. 

The fiber-taper coupling scheme was applied to liquid-immersed water-droplet microsphere resonators by Hossein-Zadeh and Vahala35. The water droplets of diameter 0.5 1 mm were generated by a syringe and immersed in a low refractive immiscible cladding liquid - an index matching oil with a refractive index of 1.3, and trapped on a silica sphere which was fixed to the bottom of a liquid container... 

Immersion electrodes, 14 27 Immersion freezing, 12 83 Immersion plating, 9 687 24 747 of metal-matrix composites, 16 173 Immiscible hquid-liquid mixing, 16 696-700... 

When a dispersed phase is passed through a nozzle immersed in an immiscible continuous phase, the most important variables influencing the resultant drop size are the velocity of the dispersed phase, viscosity and density of continuous phase, and the density of the dispersed phase (G2, HI, H5, M3, Nl, P5, R3, S5). In general, an increase in continuous-phase viscosity, nozzle diameter, and interfacial tension increases the drop volume, whereas the increase in density difference results in its decrease. However, Null and Johnson (N4) do not find the influence of continuous-phase viscosity significant and exclude this variable from their analysis. Contradictory findings... 

The controlled drop tensiometer is a simple and very flexible method for measuring interfacial tension (IFI) in equilibrium as well as in various dynamic conditions. In this technique (Fig. 1), the capillary pressure, p of a drop, which is formed at the tip of a capillary and immersed into another immiscible phase (liquid or gas), is measured by a sensitive pressure transducer. The capillary pressure is related to the IFT and drop radius, R, through the Young-Laplace equation [2,3] ... 

Dielectrophoretic forces depend on the polarizibility of species, rather than on movement of charges [99]. This allows the movement of any type of droplet being immersed by a dielectrically distinct immiscible carrier medium. Since dielectric forces are generated by spatially inhomogeneous fields, no mechanical actuation is required. In addition to this, dielectrophoretic droplet movement benefits from the general advantages given by droplet microfluidic, i.e. discrete, well-known very small volumes, no need for channels, avoidance of dead volumes and more. 

Fig. 26. Previously synthesized homogeneous material of the quaternary X-Y-phase solid solution series (composition CuFeMo6S9), heated up to 1800 °C, and the melt regulus cooled to room temperature in less than 15 min. The figure shows relics of a darker Cu-Fe-rich sulfidic phase (approx, bornite composition) which separated from the Mo-rich sulfide. Thus, a large region of liquid immiscibility must exist throughout the quaternary system (cf. Figs. 15 and 20). Owing to some vapor loss molybdenum (white) has exsolved and remains in small droplets oriented in the sulfidic groundmass. Oil immersion, x 2500...

Although discrete emulsification can be accomplished with ultrasonic baths, probes are more frequently used for this purpose because they can directly transmit US energy to a liquid-liquid system. Figure 6.7A illustrates a straightfonward procedure for obtaining an ultrasonic emulsion. The sonotrode is immersed either into the continuous phase and the phase to be dispersed is gradually added or into the two-phase system while ultrasonic energy is applied. In the latter case, the tip of the probe can be positioned at the interface [44] between the two immiscible liquids or in the continuous (or dispersed) phase, irrespective of their... 

When an immiscible fluid or a gas is completely immersed in another fluid it assumes a spherical shape of minimum surface area. The curvature of the interface is spherical and (l/r + l/rg) in Equation 4.12 can be replaced by 2/r ... 

Solutions of phosgene in water-immiscible solvents should be destroyed with ethanolic ammonia [1C121]. Decontamination of rubber tubing may be carried out by immersion into aqueous ammonia before disposal [1C121]. 

Lasheras JC, Eastwood C, Martfnez-Bazan C, Montanes JL (2002) A review of statistical models for the break-up of an immiscible fluid immersed into a fully developed turbulent flow. Int J Multiphase Flow 28(2) 247-278... 

The instability of an isolated cylindrical thread of liquid previously analyzed is but one of a large number of related instabilities. The most direct extension is to consider the thread to be immersed in a second immiscible liquid, which was analyzed many years ago by Tomotika.6 Not surprisingly, the same range of wavelengths is unstable, 0 < A < 2na,... 

In order to measure the surface tension of solutions containing surfactants, the maximum bubble pressure, pendant drop and Wilhelmy plate (immersed at a constant depth) methods are suitable capillary rise, ring, mobile Wilhelmy plate, sessile drop and drop weight methods are not very suitable. These methods are not recommended because surfactants preferably adsorb onto the solid surfaces of capillaries, substrates, rings, or plates used during the measurement. In a liquid-liquid system, if an interfacially active surfactant is present, the freshly created interface is not generally in equilibrium with the two immiscible liquids it separates. This interface will achieve its equilibrium state after the redistribution of solute molecules in both phases. Only then can dynamic methods be applied to measure the interfacial tension of these freshly created interfaces. 

Segmented flow microfluidics describes the principle of performing an assay within small liquid droplets immersed in a second immiscible continuous phase (gas or liquid). For process automation, the droplets are handled within microchannels, where they form alternating segments of droplets and the ambient continuous phase. 

In the submarine type, the strip containing buffer is immersed in a liquid immiscible with water, such as chlorobenzene. The purpose is to dissipate heat. Chlorobenzene often is used if paper strips are used, because its density is similar to that of buffer-saturated paper so the paper will stay submerged and won t float. Figure 27-23 shows a commercial apparatus, and Figure 27-24, p. 329, is a diagram of this type of apparatus. 

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