Abstract:Forming a three-phase contact line (TPC) by contacting and colliding between bubbles and mineral particles is a very important step in the flotation process. The bubble collision test, contact angle measurement and atomic force microscopy (AFM) test were used to study the effect of dodecylamine (DDA) on the formation of TPC on bubbles and hydrophobic talc and its mechanism. The results show that talc can form TPC in both deionized water and DDA solution, and the TPC formation time (t_TPC) increases with the increase of DDA concentration. The formation time of three-phase contact line (t_TPC) between bubbles and hydrophobic talc surface is the sum of the required time for the collision and rebound of the bubbles and talc (t_B) and the liquid film drainage time (t_D) between the bubble and talc. The rupture of the liquid film between bubbles and minerals is the necessary condition for the formation of TPC, so the stability of the liquid film is very important to the formation of TPC. The more stable the liquid film, the longer t_D and longer t_TPC. The stability of the liquid film between bubbles and talc is determined by the hydrophobic force on the talc surface and the interaction force between the bubbles and the nano-/micro-bubbles on the talc surface. The hydrophobic force is gravitational force. As the concentration of DDA increases, the hydrophobicity of talc increases, which tends to weaken the stability of the liquid film. There is a repulsive force between bubbles and nano-/micro-bubbles. As the concentration of DDA increases, the stability of the liquid film increases.

Key words: three-phase contact; talc; dodecylamine; flotation