Foam separation processes

Y. Okamoto and E.J. Chou, Foam separation processes, in Handbook of Separation Techniques for Chemical Engineers (P. A. Schweitzer, Ed.), McGraw-Hill, New York, 1979, pp. 2.183-2.197. 

A number of physicochemical characteristics are used to evaluate the effectiveness of foam separation processes, such as the degree of extraction, accumulation ratio (enrichment factor), selectivity coefficient, carry-away of the liquid, etc. [22,23,45,46]. 

To estimate the efficiency of surfactant extraction during foam separation process, it is expedient to introduce a parameter /characterising the quantity of the substance extracted with the foam (G ) per unit volume of the gas consumed (Vg) [51]... 

A positive effect of the internal collapse on the accumulation ratio due to internal reflux of the solution has been found experimentally in foam separation processes carried out with NaDoBS and lysozyme at cm < < cr, [67,84]. 

The role of various parameters on the course of the VF IVg dependence as well as the error of a given method for determination of the lowest residual concentration can be estimated on the basis of the analysis of the equation of material balance of the surfactant, water and gas during the foam separation process (Eq. (10.28)). If it is assumed that at low concentrations the surfactant extraction continues to the same final concentration (cml ), then in the case of cLr = cLF = Cmin, Eq. (10.28) and Eq. (10.25) yield... 

The gas volume in the foam can be expressed by the foam volume that is easier to be measured during foam separation process... 

Flotation is the term used to describe a process in which the species being separated from the bulk liquid media are insoluble particulates. Froth flotation is another one of the two foam separation processes. It also involves the production of foam in a heterogeneous aqueous system, and has a great deal of potential for the water and wastewater treatment. Froth flotation can be subdivided into at least seven categories (42,43,84), including precipitate flotation, ion flotation, molecular flotation, microflotafion, adsorption flotation, ore flotation, macroflotation, and adsorbing colloid flotation. They are described separately below. 

Foam separation process involves the selective adsorption of the surface-active pollutants at the gas-liquid interfaces of fine air bubbles in a foam separation column. The surface-active pollutants, which are adsorbed on the surfaces of the rising bubbles, can be carried upward to the top of the foam separation column and thus removed from the aqueous system as condensed foam. Foam separation can be used for both waste treatment and water purification. This section presents the data on the feasibility of removing various organics and inorganics by the foam separation processes. A general survey of foam separation process and its fundamental principles are also presented. 

For foam separation processes, adsorption takes place in solution, the essential basis exists for solute separation by foaming. Foam consists of gas bubbles separated by thin liquid films. The liquid films are often formed by the mutual approach of two already existing liquid surfaces (e.g., two bubbles below the surface). Foam structures may vary between two extreme situations. The first is wet foam, which consists of nearly spherical bubbles separated by rather thick liquid films. The second is dry foam, which may develop from the first type as a result of drainage (i.e., foam drainage). 

There are four modes for the continuous foam separation process the simple mode, the stripping mode, the enriching mode, and the combined mode. Only the first two... 

P. E. Wace, Foam Separation Process Design, Chemical Engineering Progress Symposium Series, 65 (91), 18-19 (1969). 

R. K. Wood and T. Tran, Surface adsorption and the effect of column diameter in the continuous foam separation process. The Canad. J. Chem. Engineer. 322-326 (1966). 

L. J. King, Pilot Plant Studies of the Decontamination of Low Level Process Waste by a Scavenging Precipitation Foam Separation Process, U.S. Atomic Energy Commission, ORNL-3808, 57 pages, 1968. 

D. Bhattacharyya, Foam Separation Processes, Ph.D.Thesis, Illinois Institute of Technology, IL, 1966. 

R. E. Wilson and M. H. S. Wang, Removal of lignin by foam separation processes. 

Boonyasuwat et al. (2003) suggested a multi-stage foam separation process based on surfactant waste streams to not only concentrate surfactants but also use foam fractionation to remove non-surfactant components from the effluent. With the developed process, anionic and cationic surfactant foam can be concentrated, liquefied and recycled. 

Hossain M, Fenton G 1998. Application of Foam Separation Processes for Protein Extraction/Stripping. Australas Biotechnol 8 289-295. 

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