Influence of n-octanol on the bubble impact velocity, bouncing and the three phase contact formation at hydrophobic solid surfaces

Phenomena occurring during collisions of the rising bubble with hydrophobic surfaces (Teflon and silanized glass) were monitored using a high-speed camera working with a frequency 1040 Hz. The influence of n-octanol concentration on the bubble impact velocity, bouncing amplitude and frequency, the time of three phase contact (TPC) formation (tTPC) and the time of drainage (tD) of the film formed between the colliding bubble and the hydrophobic surfaces was determined. It was found that low n-octanol concentrations caused a decrease in the tTPC in respect to distilled water, due to lowering the bubble impact velocity and bouncing. At high n-octanol concentration the tTPC was prolonged as a result of elongation the film drainage time (tD). Moreover, when the distance between capillary orifice and solid surface was varied then differences in the tTPC were observed. These differences are, in our opinion, related to formation of the dynamic architecture of the adsorbtion layer (DAL) over the rising bubble surface. The explanations of the mechanism of the tTPC prolongation for high concentration of n-octanol and influence of the DAL on the tTPC, are proposed.