Adsorption of sodium iodine at air/water interface

The change in surface potential was measured for NaI solutions. The modelled surface charge was then calculated and compared with molecular simulations. It was found that I− was enhanced at the air/water interface more than Na+. The result, which was confirmed by simulations, was opposite to the previous observation with NaCl. The trend is also consistent with anionic effects: larger and more polar anions adsorbed stronger at the air/water interface. The theoretical model was applied successfully to describe the changes for both systems, which are positive for NaCl and negative for NaI, respectively. The combined results of the two systems also revealed that the self-ionization of pure water induced a positive surface charge at 16.9 mV.