Forces between air-bubbles in electrolyte solution

Using potentials from molecular simulation, we calculate the double layer force between two air-bubbles in salt solutions considering different dielectric functions. The result is compared with the attractive van der Waals force and discussed in terms of ion specific bubble coalescence. Ion specificity plays a key role in solution chemistry and many biological processes. However, the classical DLVO theory has not been able to explain the experimentally observed ion specific forces acting between air-bubbles in electrolyte solutions. We resolve this problem by using a generalized Poisson–Boltzmann equation. We demonstrate that inclusion of both short-range potentials obtained from simulation (acting between ions and the air–water interface) and the spatial variation of the local dielectric constant near the air–water interface may be essential to obtain correct results.