An investigation into the mechanism of the three-phase contact formation at fluorite surface by colliding bubble

Mechanism of the three-phase contact (TPC) formation and phenomena occurring during collisions of the ascending bubble with a solid and flat surface were studied. Three fluorite samples of different origins and surface roughness and smooth mica plates were investigated. It was found that the time-scale and the mode of air bubble/flat fluorite surface bouncing and attachment significantly depended on the surface roughness. For smooth fluorite surfaces the time of the TPC formation and the bubble attachment was over 150 ms while for rough surfaces it was 5 to 45 ms. It was also shown that the TPC formation at fluorite and mica surfaces was determined mainly by the electrical charge of the interacting interfaces. A small amount of cationic surfactant (n-octyltrimethylammonium bromide) was used to reverse the sign of electrical charge of the bubble surface. In n-octyltrimethylammonium bromide presence there was no TPC formation at the fluorite Surface due to repulsions between positively charged interfaces, but the bubble attachment to negatively charged mica surface was observed due to attractive electrostatic interactions, It was also determined that there was no TPC formation at pHs when the signs of zeta potentials of the solution/gas and solution/fluorite interfaces were the same. (C) 2008 Elsevier B.V. All rights reserved.