Effects of reagents and solid particles on drainage and stability of liquid film, foam and froth

Abstract

The objective of this study is to explore the interrelated mechanisms governing foam drainage and stability by modeling the foam column kinetics, measuring the interfacial properties of the air-water interface and conducting forced drainage experiments. Studies on foams are usually divided into four length scales: (i) a gasliquid interface (molecular scale), (ii) a liquid film (nanometer scale), (iii) a bubble (millimeter scale), and (iv) a foam (meter scale). Although much progress has been made in each length scale, the correlation between the different length scales remains poorly understood and quantified. The present study seeks to address this problem. In many industrial processes, such as froth flotation and foam fractionation, careful control of the foam or froth stability is required to optimize the process performance. Therefore, an understanding of the correlation between the different length scales is of paramount interest for industrial applications. The present study can be divided into three different parts: (1) foam column kinetics, (2) mechanisms governing foamability and foam stability, and (3) foam drainage in the presence of solid particles.The first part models foam column kinetics to predict the evolution of foam growth, liquid fraction, the transport of liquid and gas in growing foams and foam collapse by analogy with chemical kinetics. First, a modeling framework was formulated to categorize the foam or froth growth models into zeroth, first and second order, according to the dependence of the foam collapse rate on the foam volume or height.Then, a novel kinetic model was developed based on the mass balance of gas and liquid in the foam column to simulate the foam column kinetics. Finally, the simulation results were compared with the reported experimental data. Good agreement between model predictions and published experimental results confirms the validity of the analogy between foam column kinetics and reaction kinetics.Mechanisms governing the foamability and foam stability are crucial to understanding foam behaviors. The foamability and foam stability of surfactant blend and surfactant solutions in different electrolyte concentrations were examined to elucidate the different mechanisms that collectively determine foamability and foam stability. The foam growth kinetic model developed in the previous section was also applied here. First, the foamability of sodium dodecyl sulfate (SDS)-dodecanol (DOH) IIsolutions was investigated to test the conventional theories that apply to a single surfactant of pre-critical micelle concentration (CMC). The remarkable decrease in the foamability of SDS solutions caused by the addition of DOH could not be easily explained by the theories of surface tension and surface viscoelasticity. Instead, alternative mechanisms were proposed. Second, findings regarding the foamability of SDS-DOH solutions were extended to froth flotation, that is, the effect of a nonpolar collector (diesel oil) on the foamability of frother solutions (methyl isobutyl ca...

Experimental Investigation of Foam Flooding Using Anionic and Nonionic Surfactants: A Screening Scenario to Assess the Effects of Salinity and pH on Foam Stability and Foam Height

“…The Marangoni elasticity, also known as the Marangoni effect, comes from the movement of surfactant molecules from the surrounding bulk phase to the interface under the nonequilibrium state of thick foam sheets. 36 It means that owing to film elasticity, it could deform without rupturing, and this phenomenon stabilizes the foam film. Based on this theory, any enhancement of surfactant concentration enhances the foam stability but this enhancement is accomplished up to an extent that is often close to critical micelle concentration (cmc).…”

“…The deterioration of the interstitial surfactant solution causes the film elasticity in the Gibbs process, with the assumption that the lamellae thickness is relatively small. The Marangoni elasticity, also known as the Marangoni effect, comes from the movement of surfactant molecules from the surrounding bulk phase to the interface under the nonequilibrium state of thick foam sheets . It means that owing to film elasticity, it could deform without rupturing, and this phenomenon stabilizes the foam film.…”