DEM modelling of particle-bubble capture through extended DLVO theory

作者：Gao Ya; Evans Geoffrey M; Wanless Erica J; Moreno Atanasio Roberto^*

来源：Colloids and Surfaces A: Physicochemical and Engineering Aspects , 2017, 529: 876-885.

DOI：10.1016/j.colsurfa.2017.06.082

• Discrete Element Method
• Flotation
• Hydrophobic force
• Extended DLVO theory
• Particle-bubble attachment

This work presents a computational study based on Discrete Element Method (DEM) to investigate the capture of particles by bubbles in the presence of electrical double layer repulsion. In the DEM model a fully mobile boundary condition was assumed for the gas-liquid (bubble) interface. The forces acting on the particle were gravitational, buoyancy, hydrodynamic, as well as elastic and damping forces if/when the particle penetrated inside the bubble. Surface forces were considered and were evaluated through the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. A preliminary theoretical analysis of the surface forces was carried out in order to determine the possibility of particle capture. This analysis included the determination of the interaction potential energy. Five different types of interaction energy curves were found. They were characterised by (1) a monotonic increase with distance; (2) the presence of a primary minimum; (3) the presence of an energy barrier and a primary minimum, (4) the presence of an energy barrier and a primary and a secondary minimum, and (5) a monotonic decrease with distance. DEM modelling was conducted to investigate the induction time for a single particle-bubble system. It was found that the induction time decreased with increasing contact angle and decreasing height of the energy barrier. In contrast, the primary minimum had very limited impact on induction time. Additionally, modelling of a more complex system consisting of a single bubble and multiple particles was also carried out. The multiple particle-single bubble simulation results showed that a decrease in induction time considerably enhanced collection efficiency. Finally, the concept of "contactless" flotation, which occurs in the case in which only a primary minimum exists, was also demonstrated through the use of DEM modelling.

• 出版日期2017-9-20