Surface tension film flotation

This method has been employed to measure the critical wetting surface tensions of particles of sulfur, silver iodide, methylated glass beads, quartz, paraffin-wax-coated coal, and surfactant-coated pyrite. Generally. Fuerstenau and coworkers [106-115] found that the film flotation technique is sensitive to the surface hydrophobicity and the heterogeneity of the particles. It was found that particle size, particle shape, particle density, film flotation time, and the nature of the wetting liquids have negligible effects on the results of film flotation. But the liquid and the solid particles used in the experiments must not have any chemical interactions. 

There have been many investigations on surfactant foams, foam films. Plateau border, foam drainage and their physical chemistry. The application of these results to protein foams is only partly possible. Proteins are macromolecules, their adsorption is coupled with a change in conformation at the gas/liquid interface which is a slow process. It takes 15 to 20 h to obtain the equilibrium surface tension. The residence time of the protein molecules in a flotation column is too short to attain the equilibrium surface tension during this time. Therefore, the transport of proteins to the interface and their adsorption at the interface are dynamical processes which are far from equilibrium. Surfactants have well-defined hydrophilic and hydrophobic domains. Thus it is relatively easy to calculate their interaction with the interface. Protein molecules have several hydrophilic and hydrophobic domains, and their interaction with the interface depends on the hydrophilic/hydrophobic character of their surface... 

Foam films are usually used as a model in the study of various physicochemical processes, such as thinning, expansion and contraction of films, formation of black spots, film rupture, molecular interactions in films. Thus, it is possible to model not only the properties of a foam but also the processes undergoing in it. These studies allow to clarify the mechanism of these processes and to derive quantitative dependences for foams, O/W type emulsions and foamed emulsions, which in fact are closely related by properties to foams. Furthermore, a number of theoretical and practical problems of colloid chemistry, molecular physics, biophysics and biochemistry can also be solved. Several physico-technical parameters, such as pressure drop, volumetric flow rate (foam rotameter) and rate of gas diffusion through the film, are based on the measurement of some of the foam film parameters. For instance, Dewar [1] has used foam films in acoustic measurements. The study of the shape and tension of foam bubble films, in particular of bubbles floating at a liquid surface, provides information that is used in designing pneumatic constructions [2], Given bellow are the most important foam properties that determine their practical application. The processes of foam flotation of suspensions, ion flotation, foam accumulation and foam separation of soluble surfactants as well as the treatment of waste waters polluted by various substances (soluble and insoluble), are based on the difference in the compositions of the initial foaming solution and the liquid phase in the foam. Due ro this difference it is possible to accelerate some reactions (foam catalysis) and to shift the chemical equilibrium of some reactions in the foam. The low heat... 

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