Surface tension of nanoparticles in electrolyte solutions*

The equilibrium surface tension of nanoparticles (NPs) in both deionized water and electrolyte solutions is mathematically modeled. The concept of Gibbs dividing surface is revisited in order to include the effect of dipole-dipole interaction and oscillatory energy.

NPs in deionized water behave like electrolytes. The Li and Lu method [Chemical Engineering Science, 56(8):2879-2888, 2001] is combined with the Debye-Hückel constants to estimate the mean activity coefficient for calculating the surface tension of NPs in deionized water.

NPs in an electrolyte solution behave different than mixed electrolyte solutions. Their behavior is similar to surface active agents. The Borwankar and Wasan technique [Chemical Engineering Science, 43(6):1323-1337, 1988] is extended by considering the effect of dipole-dipole interaction and oscillatory energy. In order to take into account the adsorption of NPs, the resulting equation is combined with the Langmuir approach to calculate the surface tension of NPs in an electrolyte solution. The proposed model is compared and validated with experimental data from previous studies.