Foam stabilization mechanisms in blended Short-Chain alcohol and polyether surfactant systems for flotation

Abstract

In flotation process, frothers, typically surfactants, are added to the pulp to reduce the surface tension and create the foam. Nonionic blended surfactants are widely employed as frothers in mineral flotation. In this study, we systematically investigated the foam stabilization mechanisms of blended short-chain alcohol (n-pentanol, 2-octanol) and polyether polymer (polyethylene glycol, PEG) surfactant systems for flotation. A comprehensive set of analytical techniques, including surface tension measurement, dynamic foam stability analysis, bubble morphology observation, foam film drainage measurement, and molecular dynamics simulations, were employed to explore foam properties across macroscopic and microscopic scales in single and blended surfactant solutions. Surface tension measurements revealed that PEG exhibited higher surface activity than both n-pentanol and 2-octanol, and the addition of PEG to short-chain surfactant solution significantly reduced the surface tension. Dynamic foam stability analysis showed that incorporating a small amount of PEG into n-pentanol and 2-octanol solutions substantially enhanced foam stability. Additionally, the introduction of PEG shifted the bubble size distribution curve from a bimodal to a unimodal profile, indicating the significant reduction in bubble size and enhanced inhibition of bubble coalescence. Foam film drainage tests further revealed that the addition of PEG notably slowed the drainage rate and enhanced liquid film stability. This improvement was attributed to a synergistic effect arising from the co-adsorption of n-pentanol (or 2-octanol) and PEG at the gas–liquid interface. It is hypothesized that the surface tension gradient created by differences in surface activity between PEG and the short-chain alcohols induced a stronger Marangoni flow, which promoted surfactant redistribution, enhanced the self-healing capacity of the film, and improved its overall stability. Furthermore, the foam and film stability observed in the n-pentanol/PEG system was notably superior to that in the 2-octanol/PEG system. Molecular dynamics simulations supported this finding by showing that the greater surface activity contrast between PEG and n-pentanol resulted in a more pronounced Marangoni effect, which facilitated more uniform dispersion of PEG molecules and contributed to enhanced film stability.