Effect of capillary pressure in nanobubbles on their adhesion to particles under foam flotation. Part 3

The energy possibility of the transition of free bubbles A to adherent bubbles M , or the A → M (TAM) transition, is calculated on substrates with different wetting abilities: extremely hydrophilic (Φ), extremely hydrophobic (Γ), and with incomplete wetting ability ( H x ), where x is the substrate surface fraction covered by a monolayer of collector molecules). Calculations of TAM for bubbles with a diameter ( d e ) of 2 mm to 20 nm on Φ, Γ, and H x substrates showed that the change in specific energy (Δ G / V ) in a bubble in the case of TAM depends on the value of d e , substrate wetting ability, and surface area of its contact with the bubble. According to the results of studies, high capillary pressure ( P c ) in nanobubbles M promotes their instantaneous spreading over the substrate. Herewith, P c decreases considerably. The adhesion and spreading processes occur as a single process, irreversibly, one-way, and fast, because they are not complicated by counterprocesses. Upon a decrease in equatorial diameter d e and wetting ability of the substrate, the decrease in G / V reaches several million J/m 3 . The actual simultaneity of the processes of bubble adhesion and spreading is illustrated by microphotographs of larger bubbles with a luminescent apolar reagent eliminating the effect of wetting hysteresis that is easily overcome in nanobubbles in the case of high P c values.