Effect of the Hydrophobic Force Strength on Particle- Bubble Collision Kinetics: A DEM Approach

The capture of solid particles by air bubbles is a complex process influenced by hydrodynamic and surface forces. Computer simulation provides an alternative way to experimental approaches to give an insight into the phenomenon of particle capture. In this paper, the threedimensional Discrete Element Method (DEM) has been applied to simulate the interactions between fine particles and a central bubble in a quiescent liquid. A system, consisting of 200 monodisperse silica particles and a stationary air bubble, was considered. Drag, buoyancy, hydrodynamic resistance, hydrophobic and gravitational forces have been included in the simulations. The attractive hydrophobic forces between the particles and the bubble was estimated through a single exponential decay law which depends on two parameters, K and λ. K is related to the maximum strength of the hydrophobic force, while λ is the length that indicates how fast the hydrophobic force decays with particle-bubble distance. The results have shown that a decrease in the ratio of maximum hydrophobic force to particle weight from 5.2×10 to 5.2 produced a decrease in the capture efficiency by 42.6% for λ=1 μm and by 12.5% for λ=1 nm. KeywordsDiscrete Element Method; flotation; hydrophobic force