In flotation, the role of air bubbles is particularly important, so it is necessary to have a comprehensive understanding of their formation and nature. Air bubble is a flotation device of dispersion system formed by air in dispersion medium such as water, and it has strong hydrophobicity. The water molecules around the bubble can be divided into three levels: hydration layer, diffusion layer and ordinary water layer; their number, size, distribution (space, time) have a great influence on the flotation process. In mineral flotation, various techniques for generating bubbles are very different, because the mechanism for generating bubbles is different. Therefore, the bubble generation technology can be divided into three categories: bubble generation by entrained air, bubble precipitation by dissolved gas, and bubble generation by electrolysis. The size of the bubble is related to the bubble generation method, liquid flow state, foamer structure device, surface tension, and the type and amount of surfactant added. Bubble size not only affects the flotation speed and recovery rate, but also affects the flotation selectivity.
Bubbles float up in the water due to buoyancy and interface hydrophobicity. The speed of ascent depends on the size and number of bubbles, the state of fluid movement, the pressure of the fluid, the shape of the bubbles, the dissolved substances and suspended matter in the water, etc. If the bubbles generated in the flotation column can have more collision chances with the ore particles, and can generate a plurality of bubbles adhered to a particle of gas-solid floc, reducing the probability of bubbles and particles falling off.
Bubble merger is one of the important behavioral characteristics of bubbles in ore pulp. Bubbles tend to merge and merge immediately after generation to reduce the total surface area and thus reduce the total free energy of the system. Moreover, the bubble merger is more likely to occur between bubbles of different sizes. The common form is that large bubbles merge with small bubbles. As the formation and number of microbubbles continue to increase, the clustering of bubbles will occur in the ore pulp, and the clustering of bubbles and particles is extremely beneficial to flotation.
