Why are the van der Waals forces repulsive for interactions of bubbles with solid-water interface?

Understanding interactions of bubbles with surfaces in water is critical to a variety of engineered applications and environmental concerns such as delivery of the nanobubbles for in-situ soil remediation and use of flotation in water treatment. van der Waals (VDW) force is one of the main forces controlling the interaction between a colloid and a surface in electrolyte solution. It has been recognized that the VDW force is repulsive between a solid surface and a colloid if it is a bubble. Thus, the bubbles did not stick to walls in water. However, it is still not very clear about the mechanisms controlling the repulsive VDW interactions between bubbles and walls to date. Here we used the Hamaker approach to develop an analytical model to quantify the interaction between bubbles and surfaces in water. We provided explanation for why the bubble-surface interaction is repulsive in water. Our findings have important implication to undertanding the natural and engineered processes that involve bubbles in aqutic environments.