Microflotation kinetics

Collision Efficiency, Bubble Velocity and Microflotation Kinetics... 

Flotation of large particle is often observed, which is made possible by a sufficiently high rate of expansion of the t.p.c. This fact together with the need of about three orders of magnitude lower expansion rate of the t.p.c. for small particles let us conclude that this process carmot control microflotation kinetics. 

Eq. (10.57) for the kinetic microflotation constant was presented in Section 10.10. The use of bubbles with a, 10 pm instead of bubbles with radius 100 pm makes it possible to decrease the time of flotation extraction of particles by one order of magnitude. The second stage proceeds much faster than the first one and has a small effect on the total rate of the technological process. The constant of the first stage can be estimated to be... 

Scheludko s (1970) statement that slow t.p.c expansion can control flotation kinetics may be important for large particles. Note that one of the decisive differences between flotation and microflotation also consists in the electrostatic barrier. In Section 10.5 it was shown that the weight and the hydrodynamic pressing force of micron particles, in contrast to large particles, are not sufficient to surmount the electrostatic barrier. Thus, electrostatic repulsion can exclude microflotation while it does not affect flotation, and the t.p.c. expansion rate can control flotation kinetics but has probably no influence on microflotation. 

This means that there are no contradictions between the kinetic theory of microflotation by Derjaguin Dukhin, in which the limiting stage is the overcoming of the electrostatic repulsion between bubble and particle, and the capillary theory of flotation by Scheludko in which a special attention is paid to t,p(. and the contact angle. Both models are identical in the... 

With respect to kinetic aspects of flotation and microflotation, a general model could be developed on the basis of both notions. 

Quite different measures are required when the experimentally determined kinetic constant of microflotation K is close to the calculated one. In this case it is necessary to intensify the transport stage either by arranging preliminary aggregation of particles or by applying two-stage microflotation (Section 10.9). 

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