In the froth flotation process, a large amount of foam is generated after the flotation machine is added. The foam interacts with the material particles, and this interaction is based on two methods: thermodynamic and kinetic. Each method has its own characteristics and advantages. Xinshengrun’s research shows that effectively combining the two can produce unexpected results.

High-speed photography demonstrates that during flotation, after particles contact bubbles, they slide downwards along the bubble surface to the bottom, where they oscillate. Gravity, inertial centrifugal force, and fluid force cause them to desorb from the bubble surface, but surface hydrophobicity, surface tension, and residual hydrostatic pressure maintain the stability of the particle-bubble aggregate. During the flotation process of the particle-bubble aggregate and within the foam layer, bubble coalescence and rupture due to collisions or other reasons also lead to desorption. The main reason why coarse particles are difficult to float is their easy desorption from the bubble surface. Researchers seek to achieve a rapid transition to a relatively static flotation environment after collision between bubbles and particles under turbulent conditions to reduce the desorption of hydrophobic particles. Of course, an effective method to resist adsorption is to enhance the surface hydrophobicity of the particles to be floated, thereby expanding the periphery of the three phases and improving the adhesion strength. Assuming the bubbles do not deform before and after contacting the particles, and neglecting the residual hydration film, the change in free energy before and after adhesion is calculated. It is assumed that, except for completely hydrophilic particles (contact angle of zero degrees), bubble-particle adhesion is spontaneous (free energy less than zero). The stronger the hydrophobicity of the mineral particles, the larger the contact angle, and the stronger the spontaneous tendency.

It is worth noting that bubble mineralization requires 10 minutes or longer to reach an equilibrium contact angle. During flotation, the collision and contact time between bubbles and particles is only 5-8 ms, making it impossible to reach equilibrium. Furthermore, the hydration film presents an energy barrier; neglecting the change in the free energy of the hydration film is impractical. Therefore, some thermodynamic inferences must be treated with caution.