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Distillation
Published in John J. McKetta, Unit Operations Handbook, 2018
Foam fractionation is a technique for partially separating dissolved (or sometimes colloidal) material by adsorption at the surfaces of bubbles that rise through the solution to form a foam that is then removed overhead [58]. If the materia] to be removed (termed the “colligend”) is not surface active itself, it may still be foamed of fby adding a suitable surface-active “collector” to combine with it. This union may occur through the electrical forces of counter-ionic attraction, through the formation of a complex, or in other ways. The colligend-collector product is called the “sublate.” If the colligend is ionic, the technique is sometimes termed ionfiotation [9]. However, when ion flotation gives rise to an insoluble sublate. of ten visible as a scum, it belongs more properly in the next section under mr/croparticulate foam processes [6, 10].
Downstream Processing Extraction of Fermentation Products
Published in Nduka Okafor, Benedict C. Okeke, Modern Industrial Microbiology and Biotechnology, 2017
Nduka Okafor, Benedict C. Okeke
The general principle of foam fractionation is that in a liquid foam system, the chemical composition in the bulk liquid is usually different from the chemical composition in the foam. Foam is formed by sparging the bulk liquid containing the substance to be fractionated with an inert gas. The gas is fed at the bottom (Fig. 10.1) of a tower and the foam created overflows at the top carrying with it the solutes to be fractionated. Surfactants or (surface active substances that reduce surface tension, e.g. teepol) may be added in liquids that do not foam. This method has been used to collect a wide range of microorganisms.
Equalization and Primary Treatment
Published in David H.F. Liu, Béla G. Lipták, Wastewater Treatment, 2020
Ronald G. Gantz, Janos Lipták, David H.F. Liu
Foam fractionation separates a solution containing a surface-active solute into two fractions: the foam fraction containing a high concentration of surface-active solute and a drain fraction depleted of the same solute. Foam formation also collects SS and oils and separates them from the wastewater being treated.
Xanthan gum assisted foam fractionation for the recovery of casein from the dairy wastewater
Published in Preparative Biochemistry & Biotechnology, 2020
Zhaoliang Wu, Hao Yin, Wei Liu, Di Huang, Nan Hu, Chunyan Yang, Xiaomei Zhao
The reported strategies for recovering a protein from its aqueous solution mainly included isoelectric precipitation, salting out, ion-exchange adsorption, membrane separation, and foam fractionation.[10–12] Since the discharge volume of the dairy wastewater was huge but the concentration of casein was low, isoelectric precipitation, salting out and ion-exchange adsorption were not cost-effective. Despite membrane separation could present a satisfactory performance on the concentration of the desired protein, the repugnant membrane fouling resulted in a high regeneration cost. Foam fractionation is a promising process belonging to the adsorptive bubble separation methods, and it uses bubbles as the media for concentrating the desired material based on its favorable thermodynamics.[13] Foam fractionation has the advantages of simple equipment, low energy consumption, easy scale-up, strong operability (batch and continuous modes) and environmental compatibility,[14] even being regarded as the green alternative of solvent extraction. As an early recovery step, foam fractionation has been proposed to be used in the downstream processing of product streams containing diluted desired materials, such as surfactants, proteins, and enzymes.[15,16] There are two premises to ensure the successful operation of foam fractionation: one is that the desired material should be a surfactant or can be adsorbed on the gas–liquid interface through forming complex with some surface-active materials; the other is that the desired material should be isolated from the bulk solution by the rising bubbles, thereby concentrating at the top of the column.[17] Additionally, interfacial adsorption and foam drainage are two critical steps determining the performance of foam fractionation, which is evaluated by the parameters of recovery percentage and enrichment ratio.[18] The surface activity of casein is different from that of the small molecule surfactants with a polar head and a nonpolar tail because casein molecule consists of neutral area constituted by hydrophobic amino acids and charged area constituted by hydrophilic amino acids.[19] Moreover, Farrell et al.[20] have found that in Golgi apparatus, casein monomers could be self-assembled by phosphorus and calcium. Then, the charge screening caused by self-assembly would induce the aggregation of casein molecules, thereby weakening their structural expansion on bubble surface. Thus, the surface activity of casein was weak. For overcoming this obstacle, Maldonado-Valderrama and Langevin[21] had investigated foam fractionation for the recovery of casein from its diluted aqueous solution by using Tween 20 as the foam stabilizer. Despite the recovery percentage of casein in this technology being satisfactory, Tween 20 in the foamate was difficult to be removed and it severely limited the subsequent application of casein product. Thus, it is significant to develop a cost-effective foam fractionation technology for recovering casein from dairy wastewater.