Bubbles foam fractionation

A separation can sometimes be obtained even in the absence of any foam (or any floated floe or other surrogate). In bubble fractionation this is achieved simply by lengthening the bubbled pool to form a vertical column [Dorman and Lemlich, Nature, 207, 145 (1965)]. The ascending bubbles then deposit their adsorbed or attached material at the top of the pool as they exit. This results in a concentration gradient which can serve as a basis for separation. Bubble fractionation can operate either alone or as a booster section below a foam fractionator, perhaps to raise the concentration up to the foaming threshold. 

The droplet analogs to the adsubble methods have been termed the adsoplet methods (from adsorptive droplet separation methods) [LeiTilich, Adsorptive Bubble Separation Methods, Ind. E/ig. Chem., 60(10), 16 (1968)]. They are omitted from Fig. 22-41, since they involve adsorption or attachment at liquid-liquid interfaces. Among them are emulsion fractionation [Eldib, Foam and Emulsion Fractionation, in Kobe and McKetta (eds.). Advances in Petroleum Chemistry and Refining, vol. 7, Interscience, New York, 1963, p. 66], which is the analog of foam fractionation and droplet fractionation [Lemlich, loc. cit. and Strain, J. Phys. Chem., 57, 638... 

Excess collector can also reduce the separation by forming micelles in the bulk which adsorb some of the colhgend, thus keeping it from the surface. This effect of the micelles on Ki for the colhgend is given theoretically [Lemhch, Principles of Foam Fractionation, in Periy (ed.). Progress in Separation and Purification, vol. 1, Interscience, New York, 1968, chap. 1] by Eq. (22-44) [Lemlich (ed.). Adsorptive Bubble Separation Techniques, Academic, New York, 1972] if F, is constant when C, > C-... 

By using an anionic collector and external reflux in a combined (enriching and stripping) column of 3.8-cm (1.5-in) diameter with a feed rate of 1.63 ni/n [40 gal/(h ft )] based on column cross section, D/F was reduced to 0.00027 with C JCp for Sr below 0.001 [Shou-feld and Kibbey, Nucl. AppL, 3, 353 (1967)]. Reports of the adsubble separation of 29 heavy metals, radioactive and otheiwise, have been tabulated [Lemlich, The Adsorptive Bubble Separation Techniques, in Sabadell (ed.), Froc. Conf. Traces Heavy Met. Water, 211-223, Princeton University, 1973, EPA 902/9-74-001, U.S. EPA, Reg. 11, 1974). Some separation of N from by foam fractionation has been reported [Hitchcock, Ph.D. dissertation. University of Missouri, RoUa, 1982]. 

It has been suggested the methods of separation involving adherence of particles of different dispersity on bubble surface as a result of adsorption or adhesion, to be named adsorptive-bubble (adsubble) methods [27,28]. The methods of surface separation are termed differently in the different publications in the case of surfactant extraction they are referred to as adsorption flotation, foam flotation, foam fractionation, foam separation or adsorptive accumulation in the case of ion extraction, they are called ion flotation, foam flotation of hydrophobic precipitates, etc. 

Porous Septa In the quiescent regime porous plates, tubes, disks, or other shapes that are made by bonding or sintering together carefully sized particles of carbon, ceramic, polymer, or metal are frequently used for gas dispersion, particularly in foam fractionators. The resulting septa may be used as spargers to produce much smaller bubbles than will result from a simple bubbler. Figure 14-95 shows a com-... 

Lemlich, R., Adsubble Processes Foam Fractionation and Bubble Frac-... 

J = 1 1 1 1 1 1 1 - 4> 0.97 0.95 L A r no rigure viscosity as a lunc-tion of shear stress for an aqueous polymer-surfactant foam at the bubble volume fractions 0 shown. (From Khan et al. 1988, with permission... 

According to the collection procedure for the enriched gas-liquid and/or gas-solid interfaces, adsorptive bubble separation processes or techniques can also be divided into two large categories (a) foam separation, which involves the production of foam in the process, and (b) nonfoaming adsorptive bubble separation, which involves no production of foam. Foam separation can be further subdivide into foam fractionation and flotation. Nonfoaming adsorptive bubble separation, however, can be further subdivided into bubble fractionation, solvent sublation, and noirfoaming flotation. Lemlich (84) and Wang (1,75) provided the definitions of these technical terms in their books. 

Bubble fractionation is similar to foam fractionation except that there is no foam produced in the system thus, it is applied to dilute surface-active solutions that do not foam while foam fractionation is applied to surface-active solutes at high concentration (76,77). Technically speaking, bubble fractionation represents an operation in which gas is bubbled up through a vertical bubble reactor containing the surface-active solute(s)... 

Type of flow pattern(s) involved in an adsorptive bubble separation system depends on the type of process used. For example, bubble fractionation involves two-phase (gas-phase and liquid-phase) bubble flow, while solvent sublation involves multiphase bubble flow in their vertical bubble cells. Foam fractionation involves a two-phase bubble flow in the bottom bubble cell, and a two-phase froth flow in the top foam cell. However, all froth flotation processes (i.e., precipitate flotation, ion flotation, molecular flotation, ore flotation, microflotation, adsorption flotation, macroflotation, and adsorbing colloid flotation) involve multiphase bubble flow and multiphase froth flow. 

D.O. Harper, Bubble and Foam Fractionation, PhD Thesis, University of Cincinnati, Cincinnati, OH 1967. 

A way to separate many nonvolatile compounds is to form a foam and have the desired material attach itself to the surface of the gas bubble. The compounds attached are not sufficiently large to be classified as a solid. An example of this is the removal of detergents from waste water by bubbling a gas through the water and collecting the detergent in the foam that is formed. This is known as foam fractionation. Chapter 34. 

Chapters 33 and 34 involve the application of bubbles of gas to effect a separation. In Chapter 33 diffusion of a volatile compound into a gas bubble is the operating principle (purge and trap). Chapter 34 discusses foam fractionation in which the gas bubbles are coated with a surfactant. Dissolved compounds adhere to the surface and are removed as a foam. Later on in Chapter 34 flotation, in which small solid particles are coated such that gas bubbles adhere to them and they are lifted out of the solution, is discussed. 

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