Permeable solid

Wells, S. A. and Dick, R. I. (1993) "Permeability, Solid and Liquid Velocity, and Effective Stress Variations in Compressible Cake Filtration," Proceedings, American Filtration Society Conference on System Approach to Separation and Filtration Process Equipment, Chicago, Illinois, May 3-6, pp. 9-12... 

Thermoplastic stabilization/solidification (S/S) is a technology for the ex situ treatment of radioactive, mixed, and hazardous wastes. It is a process that uses thermoplastic polymers to physically immobilize the hazardous constituents of contaminated soils, sludges, sediments, or even liquid wastes. The idea is to prevent the migration of contaminants into the environment by forming a low-permeability solid mass. The goal of this technology is to immobilize contaminants within the existing medium, rather than to try and remove them via chemical and/or physical treatments. 

Research related to the use of vanadium phosphates or V2O5 as oxidants of gases such as CO and SO2 in commercial processes shows that solid vanadyl sulfate can serve as a gas-permeable solid-phase electrolyte [102]. Two reversible redox features are observable at slow scan rates (20-150 mV s ) by CV in a gas-tight two-electrode cell packed with powdered VOSO4 3H2O between a 10-mm carbon disk and a 3-mm glassy carbon electrode. The V(IV/V) couple was observed at 0.55 V versus C, and the V(IV/III) couple was observed at —0.97 V. Unlike in aqueous solution where vanadyl sulfate is reduced to [V(H20)6] ", the V=0 bond in the solid remains intact. The oxidation of CO(g) can be observed when it is introduced into this cell. 

Constant-volume batch diafiltration is the most efficient process mode. Sequential batch diafiltration is a series of dilution-concentration steps. Continuous diafiltration practiced in one or more stages of a cascade system has the same volume turnover relationship for overall recoveries as sequential batch diafiltration. The residence time however is dramatically reduced. If recovery of permeable solids is of primary importance, the permeate from the last stage may be used as diafiltration fluid for the previous stage. This countercurrent diafiltration arrangement results in higher permeate solids at the expense of increased membrane area. 

Membrane-retained components are collectively called concentrate or retentate. Materials permeating the membrane are called filtrate, ultrafiltrate, or permeate. It is the objective of ultrafiltration to recover or concentrate particular species in the retentate (eg, latex concentration, pigment recovery, protein recovery from cheese and casein wheys, and concentration of proteins for biopharmaceuticals) or to produce a purified permeate (eg, sewage treatment, production of sterile water or antibiotics, etc). Dia.filtra.tion is a specific ultrafiltration process in which the retentate is further purified or the permeable solids are extracted further by the addition of water or, in the case of proteins, buffer to the retentate. 

Leaching is the removal of a soluble fraction, in the form of a solution, from an insoluble, permeable solid phase with which it is associated. The separation usually involves selective dissolution, with or without diffusion, but in the extreme case of simple washing it consists merely of the displacement (with some mixing) of one interstitial liquid by another with which it is miscible. The soluble constituent may be solid or liquid and it may be incorporated within, chemically combined with, adsorbed upon, or held mechanically in the pore structure of the insoluble material. The insoluble solid may be massive and porous more often it is particulate, and the particles may be openly porous, cellular with selectively permeable cell walls, or surface-activated. 

Leaching is the removal of a soluble fraction, in the form of a solution, from an insoluble, usually permeable, solid phase with which it... 

Definition Solid-liquid extraction is the use of a solvent to dissolve and remove a soluble fraction (called the solute) from an insoluble, permeable solid. 

Y. Teraoka, T. Nobunaga, K. Okamoto, N. Miura and N. Yamazoe, Influence of constituent metal cations in substituted LaCoOs on mixed conductivity and oxygen permeability. Solid State Ionics, 48 (1991) 207-212. 

In practice, a solid catalyst is most conveniently modeled as a quasi-homo-geneous phase. Even if the catalyst particle is porous, visualize it as a homogeneous, but permeable solid. Mass transfer in its interior is retarded by two effects obstruction of part of the cross-sectional area by the solid material, and diffusion paths that are longer because molecules have to wind their way around the obstructions (tortuosity effect). In the quasi-homogeneous model, the retardation is accounted for by the use of appropriately smaller "effective mass-transfer or diffusion coefficients. 

In some solid-bed leaching the solvent is volatile, necessitating the use of closed vessels operated under pressure. Pressure is also needed to force solvent through beds of some less permeable solids. A series of such pressure tanks operated with countercurrent solvent flow is known as a diffusion battery. 

In other situations the solute is distributed through a more or less permeable solid. Here the rate of leaching is largely governed by the rate of diffusion through the solid, as discussed in Chap. 21. 

The efficiency of a stage or plate in a distillation, absorption, or extraction operation is a function of the mass-transfer rates and transfer coefficients. When material is removed from a permeable solid, as in leaching or drying operations, the transfer rates and sometimes the stage efficiencies can be estimated from diffusion theory. 

We have considered that Al t = i-C- the total interfacial area of the liquid is equal to the total interfacial area of the solid. Noting that fluxes are different from 0 only at permeable solid surfaces, in a closed system the only permeable surfaces are those corresponding to the catalyst. Therefore ... 

The use of complementary experimental techniques as a numerical and visual basis in the formulation of more realistic and applicable pore structure characterisation models has become widespread. Examples of the use of these techniques include mercury porosimetry [9] in the study of entrapment hysteresis in porous media, and in the characterisation of permeable solids [7], the use of NMR (nuclear magnetic resonance) in the heterogeneous and hierarchical stractural modelling of porous media [8,10], and flie use of SEM imaging techniques [7,11]. 

According to equation (12.8) the flux is inversely proportional to the thickness of the film. A thicker film is therefore less permeable. Solids, such as Ti02, that are added to paints as fillers or pigments tend to reduce the flux of oxygen or water, provided they exhibit good adhesion to the polymer matrix. The particles increase the effective length of the diffusion path because the diffusing species must pass around them. 

The study of porous crystalline materials has recently become an area of intense research activity, but, in the context of permeable solids, should we refer to the uptake of... 

Teraoka Y, Nobunaga T, Okamoto K, Miura N, Yamazoe N, Influence of Constituent Metal Cations in Substituted LaCoOs on Mixed Conductivity And Oxygen Permeability, Solid State Ionics, 4S, 207-212(1991). 

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