Liquids, immobilized

In the limit of high viscosity, immobile liquid bridges formed from materials such as asphalt or pitch fail by tearing apart the weakest bond. Then adhesion and/or cohesion forces are Lilly exploited, and binding ability is much larger. 

Electrolyte Potassium hydroxide Polymer membrane Immobilized liquid molten carbonate Immobilized hquid phosphoric acid Ion exchange membrane Ceramic... 

Electrolyte Ion Exchange Membranes Mobilized or Immobilized Potassium Hydroxide Immobilized Liquid Phosphoric Acid Immobilized Liquid Molten Carbonate Ceramic Ceramic... 

There is a complication, though a thin (c. cm) layer of solution exists between the electrode and the bulk solution that is relatively immobile. This forms because of the inherent viscous drag of the solution as it moves over the solid electrode. We call this thin film of immobile liquid the diffusion layer, where the latter has a thickness S. The thickness of the layer depends on the rotation speed according to the following ... 

Dispersion free extraction in hollow fiber (HF) membrane utilizes immobilized liquid-liquid interface at the pore mouth of a microporous membrane to effect phase to phase contact and the mass transfer process. HF module can be con-... 

Bridges due to immobile liquids form adhesional and cohesional bridging bonds. Thin adsorption layers are immobile and can contribute to the bonding of fine particles under certain circumstances. 

For volatile materials vapor phase chromatography (gas chromatography) permits equilibration between the gas phase and immobilized liquids at relatively high temperatures. Tire formation of volatile derivatives, e.g., methyl esters or trimethylsilyl derivatives of sugars, extends the usefulness of the method.103104 A method which makes use of neither a gas nor a liquid as the mobile phase is supercritical fluid chromatography.105 A gas above but close to its critical pressure and temperature serves as the solvent. The technique has advantages of high resolution, low temperatures, and ease of recovery of products. Carbon dioxide, N20, and xenon are suitable solvents. 

Following the work of Bloch and Vofsi, other methods of producing immobilized liquid films were introduced. In one approach, the liquid carrier phase was held by capillarity within the pores of a microporous substrate, as shown in Figure 11.3(a). This approach was first used by Miyauchi [7] and by Largman and Sifniades and others [8,9], The principal objective of this early work was to recover copper, uranium and other metals from hydrometallurgical solutions. Despite considerable effort on the laboratory scale, the first pilot plant was not installed until 1983 [10], The main problem was instability of the liquid carrier phase held in the microporous membrane support. 

Figure 11.24 Facilitated transport of hydrogen sulfide through an immobilized carbon-ate/bicarbonate solution [26]. Reprinted with permission from S.L. Matson, C.S. Herrick and W.J. Ward III, Progress on the Selective Removal of H2S from Gasified Coal Using an Immobilized Liquid Membrane, Ind. Eng. Chem., Prod. Res. Dev. 16, 370. Copyright 1977, American Chemical Society and American Pharmaceutical Association...

Supported liquid membrane (SLM) Aqueous solution An immiscible immobilized liquid membrane containing specific metal ion carriers Divalent metal ions Integrative field sampling, preconcentration of trace elements, mimicking biological membranes Days 74... 

Most liquid membranes are less stable than their polymeric counterparts. Although the thin liquid film in the membrane corresponds to a short diffusion path and hence a high mass transfer rate, small amounts of the immobilized liquid can be displaced under pressure. Also, the immobilized liquid may slowly dissolve in the external phases, eventually leading to discontinuities in the liquid... 

FIGURE 37 Mechanisms of carrier-facilitated immobilized liquid membrane extraction, also referred to as coupled transport. The species, R, refers to the carrier component responsible for complexation. 

Adhesion and cohesion forces in the immobile liquid films between individual primary powder particles. These forces may not contribute significantly to the final granule strength once the granules have been dried. These forces arise from the thin liquid layers around particles that may be generated due to moisture uptake by the powders. This immobile liquid film tends to decrease the inter-particle distances leading to an increase in the van der Waals forces between particles. 

In these methods of size enlargement, powders are densified and compacted by application of external force in a confined space. Forces involved to produce a stable agglomerate include solid bridges, immobile liquid bonds, surface forces and mechanical interlocking. The success of the operation depends in part on the effective utilization and transmission of the applied external force and in part on the physical properties of the particulate material. 

Methods which enploy liquid phase treating liquors (spray, transfer rolls and belts, etc.) share a cannon difficulty stemming from the lew volume of liquor in relation to the large surface area of the fibers conprising the substrate to be treated. This difficulty is acerbated when aqueous liquors are to be applied to hydrophilic fibers. Foam coating methods enploy stable foams which allow the thickness of the liquid-air mixture to be controlled by a doctor blade or roll. Conparatively low add-ons can be achieved by virtue of the low density of the foam layer, but the stable nature of such foam, and its immobile liquid phase, inhibit rapid, uniform distribution through the substrate. 

The distinguishing features of gas chromatography are a gaseous mobile phase and a solid or immobilized liquid stationary phase. Liquid stationary phases are available in packed or capillary columns. In the packed columns, the liquid phase is deposited on a finely divided, inert solid support, such as diatomaceous earth or porous polymer, which is packed into a column that typically has a 2- to 4-mm id and is 1 to 3 m long. In capillary columns, which contain no particles, the liquid phase is deposited on the inner surface of the fused silica column and may be chemically bonded to it. In gas-solid chromatography, the solid phase is an active adsorbent, such as alumina, silica, or carbon, packed into a column. Polyaromatic porous resins, which are sometimes used in packed columns, are not coated with a liquid phase. 

It should be noted that an expression similar to (47) was recommended by Budianski [50] and Hill [51] for description of the dependence of the relative modulus of disperse composites on concentration. A more elaborate expression was obtained by Lee [53], who used Vand s concepts of the immobilized liquid for the description of the behavior of dispersions in terms of the mechanics of three bodies ... 

Steinour [40] defined the immobile liquid per unit total volume as a(l- ), where a =... 

A stationary phase, where a solid, a gel or an immobilized liquid is held by a support matrix. 

Shukla, J.P., Sonawane, J.V., Kumar, A., and Singh, R.K., Amine facihtated up-hill transport of plutonium(IV) cations across an immobilized liquid membrane. Ind. J. Chem. Tech., 1996, 3 145-148. 

As for CO2, VOCs can also be removed by using immobilized liquid membranes. Obuskovic et al. [35] immobilized a thin layer of silicone oil in the microporous of the hollow fiber polypropylene membrane beneath the dense-coated skin. The performance of the system has been proved for toluene, methanol, and acetone removal from N2. With respect to the simple hollow fiber, the presence of the oil layer led to a 2-5 VOC more enriched permeate (due to the reduction of nitrogen flux) with a separation factor of 5-20 times higher (depending on the VOC and the feed gas flowrate). The membrane was stable for 2 years. 

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