Surfactant flow between a Plateau border and a film during foam fractionation

Abstract

A fluid mechanics problem relevant to foam fractionation processes is analysed. Specifically the fluid flow field transporting surfactant from foam Plateau borders (fed with surfactant-rich material) towards comparatively surfactant-lean foam films is considered. The extent to which this surfactant mass transfer is limited by surface viscous effects is studied. Previous work (Vitasari et al., 2015) made assumptions about the likely flow field along the Plateau border surface. These assumptions suggested that ‘high’ surface viscosity (measured by a suitable dimensionless parameter) led to strong suppression of the rate of surfactant mass transfer from Plateau border to film, whereas ‘low’ surface viscosity did not suppress this mass transfer rate in any significant way. More detailed fluid mechanical calculations which are carried out here corroborate the aforementioned assumptions in the ‘high’ surface viscosity regime. However the calculations suggest that in the ‘low’ surface viscosity regime, in contrast to the findings from the previous assumptions, moderate reductions in the rate of surfactant mass transfer are also possible. Counterintuitively these moderate reductions in mass transfer rate potentially have more negative impact on fractionation processes than the aforementioned strong suppression. This is because they tend to arise under conditions for which the efficiency of the fractionation system is particularly sensitive to any reduction whatsoever in the surfactant mass transfer rate

A review of aqueous foam in microscale

“…Hence, Marangoni flow distributes the extra surfactant molecules from PB to the films. Two types of flow are active in the transport of the surfactants: the film drainage from film towards PB due to the lower pressure in the PB and the Marangoni flow from surfactantrich PB towards the films due to a sharp surfactant gradient near the edges of the films [71,72]. The drainage rate of the interfacially mobile films is larger than that of the interfacially rigid films resulting in the film drainage In the first instance we focus on the flow in the film.…”

“…The drainage rate of the interfacially mobile films is larger than that of the interfacially rigid films resulting in the film drainage In the first instance we focus on the flow in the film. We adopt the model already considered by Vitasari et al (2016) in which the film is taken to be perfectly flat (i.e. we ignore the complications associated with possible dimpled shapes of the film near its junction with the Plateau border, Frankel and Mysels, 1962;Joye et al, 1992Joye et al, , 1994Joye et al, , 1996.…”

A meshfree Lagrangian method for flow on manifolds

“…Fluid flow on curved surfaces forms an important aspect in modeling dynamics on biomembranes and other interfacial transport processes, 1,2 in representing surfactant dynamics, 3 in thin film flow and lubrication, 4 and visualization, 5 among other applications.…”

Influence of the Process Parameters on the Foam Fractionation Treatment of Olive Mill Wastewater

“…The foam fractionation of ions is similar to ion otation, but uses an excess of surfactant or a proper frother to produce stable foam [18][19][20]25]. During foam fractionation, gas bubbles are introduced into a liquid, which contains surface-active substances [26]. Foam formation occurs when surface-active molecules attach to the gas-liquid interface of the introduced bubbles.…”

“…For this reason, this process was investigated by means of Design of Experiments (DoE). DoE has shown its bene t in the establishment of foam fractionation in biotechnological applications [21][22][23][24]40] and oxidative treatment of OMW [25][26][27]41], for example. The simultaneous variation of several process parameters combined with statistical analysis is advantageous with regard to the smaller number of experiments compared to the conventional concept of \one factor at a time".…”