THE EFFECT OF CAPILLARY PRESSURE IN NANOBUBBLES ON THEIR ADHERENCE TO PARTICLES DURING FROTH FLOTATION. PART 5. CURVES OF NANOBUBBLE SPREADING UPON A SURFACE WITH VARIOUS WETTABILITY

For the purpose of improving the accuracy of obtained results, the paper compares two methods for studying wetting and spreading processes upon a solid substrate. The first method utilizes liquid droplets, and the second method utilizes bubbles. When spreading, the shape of droplets and bubbles changes, and this can be assessed quantitatively only by the Laplace equation, though the equation is applied only in the case of bubbles (the second method). For the first method, this excludes control over surface cleanliness of the spreading droplet. The effect of micropollution on the results is considered on the basis of precise calculations carried out for both methods. The paper calculates spreading curves for nanobubbles with initial diameters of 20 and 10 nm on substrates with different wettability, where the wettability is assessed not by the numerical value of the contact angle, but by easily realized samples of such  substrates Г, Ф and Нх corresponding to the contact angle, where х is the fraction of the surface under the bubble, covered with molecules of the ionogenic collector: 0,8; 0,6; 0,4, and 0,2. The spreading curves clearly illustrate the range of possible spreading of nanobubbles, from the limit spreading on the substrate Г to practically zero spreading on the substrate Ф, as well as energy sources of the spreading process and causes of their depletion. The informational value of spreading curves is preconditioned by the fact that more than ten parameters of the bubble and the substrate are used in their calculation. When using reagents, activation of the flotation process can spread to larger bubbles.

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