The process in which the ore particles are in contact with the bubbles and achieves attachment is essentially a process in which the surface free energy of the mineral-bubble body is changed. The free energy of the mineral surface is produced by the physicochemical composition and crystal structure of the ore particles. The free energy of the surface of the bubble is mainly stored by a hydrated membrane molecule in a state of imbalance. According to the second theorem of thermodynamics, whether the free energy can be reduced on the surface of the ore and the surface of the bubble after collision between the bubble and the ore.
During the flotation process, due to the agitation of the flotation machine impeller and the collision and contact between the ore particles and the bubbles caused by the falling of the ore particles, when the ore particles gradually approach the bubble, the hydration layer and the surface of the ore particles on the surface of the bubble are firstly The water layer begins to contact. (The figure above) OX 1 is the thickness of the two-layer hydrated film. At this point, the interface of the system can be at point a. To make the ore particles further close to the bubbles, it is necessary to disturb the water molecules aligned in the two layers of water film. Under the action of external work, the floatable ore particles can rise to the peak point b and the thickness of the hydration layer is reduced to OX 2 . At this point, the order of the water molecules in the hydration layer has been disrupted and must be rearranged, so the attraction between the molecules plays a leading role at this time, so the ore particles and the bubbles are close to each other by their own forces, and the hydrated film is very Fast thinning. The system interface crosses the energy peak and automatically drops from point b to point c. The distance between the ore and the bubble moves to OX3. At this point, the hydrated film ruptures, leaving the residual hydrated film on the surface of the ore particles, and the ore particles are tightly bonded to the bubbles to achieve adhesion. Hydrophilic ore particles have a strong affinity for water molecules due to their surface, and the water layer molecules adhere to the surface of the ore particles tightly and firmly, and the arrangement order is difficult to be disturbed even under external action. Therefore, when the hydrophilic ore particles approach the bubble, the interfacial energy of the system rises steadily. As shown in the curve I above, the process cannot proceed spontaneously. The hydrated film becomes a barrier to further contact between the ore particles and the bubbles, so the hydrophilic ore particles are difficult to adhere to the bubbles. on.
As mentioned above, it takes a certain time for the ore particles to adhere to the bubbles. We call this time the attachment time, and the ore particles collide with the bubbles and have a collision contact time. Obviously, only when the attachment time is less than the contact time, the ore particles can be attached to the bubbles. The shorter the attachment time and the more pleasant the adhesion rate, the more likely the ore particles will float with the bubbles.
In order to make the mineralized bubbles float up to the foam layer on the upper surface of the slurry, it is also necessary to prevent the mineralized bubbles from falling off the bubbles due to the mechanical force during the floating process. This requires the ore particles to adhere to the bubbles to be firm and have a certain strength. The larger the adhesion area and the contact angle, the greater the adhesion strength of the ore particles on the bubbles, and the less likely the ore particles are to fall off the bubbles.
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