A study of the mechanism of gas absorption into oil-water emulsions

Abstract

The mechanism of oxygen and argon transfer into aqueous emulsions of n-alkans and of oleic acid was studied both theoretically and experimentally. An apparatus allowing to measure the coefficient of mass transfer from individual bubbles into the turbulent medium of either a single- or multi-phase liquid has been designed and constructed. The effect of the oil phase on the bubble-to-emulsion mass transfer coefficient was investigated. In o/w type emulsions (oil as the dispersed and water as the continuous phase) of n-alkans (the system with negative spreading coefficient) the mass transfer coefficient k L w is not affected by the content of the oil phase, and is equal to the coefficient of mass transfer into a pure aqueous phase. In the w/o type emulsion the k L w value increases proportionately to the volume fraction of n-alkans. In the oleic acid-in-water emulsion (the system with positive spreading coefficient) k L w initially decreases and then increases proportionately to the oil fraction. The initial decrease of k L w is attributed to surface activity effects of oleic acid. The data suggest that the mechanism of gas transfer to the emulsions is as follows: No direct contact between the oil and the gas phase exists in o/w type emulsions with negative spreading coefficient, and the transfer path is gas-water-oil. In w/o type emulsions (both with negative and positive spreading coefficient), however, there is a direct contact between the gas and both the continuous oil phase and the dispersed aqueous phase; there is a parallel transfer of gas to both the phases.