Study on the Strengthening Mechanism of a MIBC–PEG Mixed Surfactant on Foam Stability

In the flotation process, the frother, which is typically a surfactant, can be added to the pulp to reduce the surface tension and create stable foam. Currently, the nonionic mixed surfactant is widely employed as the frother for fine coal flotation. In this study, we focused on examining the foam properties of a mixed surfactant comprising short-chain methyl isobutyl carbinol (MIBC) and long-chain polyethylene glycol-1000 (PEG). Analytical techniques such as surface tension measurement, dynamic foam stability measurement, bubble morphology observation, and foam film drainage measurement were used to investigate the foam properties in single and mixed surfactant solution from a macroscopic scale to a microscopic scale. The surface tension results indicated that PEG exhibited higher surface activity than MIBC, and the addition of PEG to MIBC resulted in a significant reduction in solution surface tension. The dynamic foam stability analysis revealed that the incorporation of a small amount of PEG into MIBC solution notably improved foam stability. Furthermore, the addition of PEG to the MIBC solution led to a shift in the bubble size distribution curve from a "double peak" to a "single peak" shape. This shift indicated a substantial reduction in bubble size, indicating an enhanced inhibition of bubble coalescence. Additionally, the liquid film drainage rate was significantly slowed down, and the stability of the liquid film was improved upon the addition of PEG to MIBC. This improvement can be attributed to the synergistic effect of MIBC and PEG molecules adsorbed at the gas-liquid interface. The synergistic effect of mixed MIBC-PEG was due to the additional surface tension gradient created by the difference in surface activity between PEG and MIBC. This surface tension gradient enhances the Marangoni flow of surfactant molecules, thereby improving the self-healing ability of the liquid film and increasing its stability.