Reversal of bubble charge in multivalent inorganic salt solutions—Effect of aluminum

This is the authors' abstract. We don't add key points for this paper.

The charge of bubbles in aqueous solution is important in determining their interactions with particles, droplets, and other bubbles. While bubbles are known to be negatively charged in such media as water and sodium chloride solutions, they are found here to exhibit unusual positive surface charge characteristics in solutions of trivalent aluminum cations. Analysis of the results indicates that the reversal of bubble charge can be attributed to specific adsorption of Al+3 and its hydroxo complexes at the gas-liquid interface in the low pH range and to precipitation of aluminum hydroxide in the intermediate pH range.