Bubble fraction

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. 

In solvent sublation an immiscible liquid is placed atop the main liquid to trap the material deposited by the bubbles as they exit (Sebba, Ion Flotation, Elsevier, New York, 1962). The upper hquid should dissolve or at least wet the material. With appropriate selectivity, the separation so achieved can sometimes be much greater than that with bubble fractionation alone. 

Unless the hquid pool is purposely lengthened vertically in order to give additional separation via bubble fractionation, it is usually taken to represent one theoretical stage. A bubbler submergence or 30 cm or so is usually ample for a solute with a molecular weight that does not exceed several hundred. 

Bubble Fractionation Figure 22-45 shows continuous bubble fractionation. This operation can be analyzed in a simplified way in terms of the adsorbed cariy-up, which furthers the concentration gradient, and the dispersion in the liquid, which reduces the gradient [Lemhch, Am. Inst. Chem. Fng. J., 12, 802 (1966) 13, 1017 (1967)]. 

The escaping bubbles from the top of a bubble-fractionation column can carry off an appreciable quantity of adsorbed material in an aerosol of very fine film drops [various papers, J. Geophys. Res., Oceans Atmos., 77(27), (1972)]. If the residu solute is thus appre-ciablv depleted, Cj in Eq. (22-57) should be replaced with the average residual concentration. 

A small amount of collector (surfactant) or other appropriate additive in the liquid may greatly increase adsorption (Shah and Lemlich, op. cit.). Column performance can also be improved by skimming the surface of the liquid pool or, when possible, by removing adsorbed solute in even a tenuous foam overflow. Alternatively, an immiscible liquid can be floated on top. Then the concentration gradient in the tall pool of main hquid, plus the trapping action of the immiscible layer above it, will yield a combination of bubble fractionation and solvent sublation. 

The C02 is accompanied by radon, which is difficult to separate. The C02 is therefore often stored before counting its 14C activity. A small amount of radon is in the bubble fraction larger amounts of radon are in the purged extractions. The C02 is purified before counting by a series of freezing and unfreezing steps. 

Wang, L.K. Continuous Bubble Fractionation Process. Ph.D. Dissertation Rutgers University, NJ, USA, 1972 171 p. 

Wang, L.K. The Effects of Cationic Surfactant Concentration on Bubble Dynamics in a Bubble Fractionation Column, PB86-197845/AS US Department of Commerce, National Technical Information Service Springfield, VA, 1984 47 p. 

The data of Clark and Blackman for the change with time of the part of the specific surface area attributed to a certain bubble fraction, Fig. 6.6, can serve as a qualitative verification of the validity of the predicted evolution of the bubble distribution function, given... 

Nakajima, M., Harada, M., Asai, M., Yamazaki, R., and Jimbo, G. Bubble fraction and voidage in an emulsion phase in the transition to a turbulent fluidized bed, in Circulating Fluidized Bed Technology III (P. Basu, M. Horio and M. Hasatani, eds.), pp. 79-84. Pergamon Press, 1991. 

Bubble Fractionation Figure 22-45 shows continuous bubble... 

Chiral separation using MIPs can also be achieved by bubble fractionation [63] and with MIP membranes [64-68], MIP particles selective for an amino acid derivative were used as collectors for enantiomeric enrichment by bubble fractionation. The method is envisaged to be a potentially powerful approach to process-scale separations [63]. 

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