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

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An experimental technique has been developed to study the electrokinetic behavior of gas bubbles in aqueous electrolyte solutions. It was found that bubbles are negatively charged in NaCl solutions whereas, under certain conditions, they become positively charged in MgCl2 solutions. The observed charge reversal in the pH range of 9 to 11 is attributed to the precipitation of Mg(OH)2(s) at the gas-liquid interface while the reduction in the magnitude of the zeta potential of the bubble observed in the acidic pH range is considered to be due to the specific adsorption of Mg+2.