The surfactant addition mode on the collision and attachment of bubbles on hydrophilic quartz and hydrophobic methylated quartz

The collision between bubbles and methylated/hydrophilic quartz was explored under three surfactant addition modes: dissolve surfactant in water, inject surfactant vapor into bubble, and synchronously add surfactant in the water and bubble. [Display omitted] •Novel addition mode injects surfactant vapor into the bubbles.•Vapor addition mode presents smaller induction time and collision frequency.•Bubble-methylated quartz collision presents larger contact angle than bubble-quartz collision.•DDA, MIBC and 2-octanol present different performances on bubble-quartz/methylated quartz collision. In order to improve the utilization efficiency of surfactants, a novel addition mode injects surfactant vapor into the bubbles has been proposed. The effect of the cationic surfactant dodecylamine (DDA) and the frothers methyl isobutyl carbinol (MIBC) and 2-octanol on the collision between bubbles and hydrophilic/hydrophobic quartz was evaluated under three surfactant addition modes namely as: 1) vapor in air, 2) dissolved in water, and 3) vapor in the air and dissolved in water. When the surfactants were added as vapor in the air the induction time and collision frequency were smaller than those when surfactants were dissolved in water and added partially dissolved in water and as vapor in air. This is independently of the surfactant sort and quartz surface property. Of these three surfactants, when added as vapor, DDA showed smaller collision frequency and induction time as compared to MIBC and 2-octanol. When the surfactants were dissolved in water and added partially dissolved in water and as vapor mixed with the air, the induction time and collision frequency were larger with DDA as compared to MIBC and 2-octanol. The induction time increased nearly linearly with the collision frequency, independently of the surfactant sort, surface property and surfactant addition mode. The contact angle decreased as the induction time increased on the hydrophobic methylated quartz surface while it was almost constant as the induction time increased on the hydrophilic quartz surface. The results may provide valuable insight into the development of surfactant utilization and waste mitigation in flotation.