WATER-PERMEATION SWELLING OF EMULSION LIQUID MEMBRANE

Water-permeation swelling resulting from osmotic pressure was studied both theoretically and experimentally. Flat-bed and hollow-sphere models considering the change of permeation area with agitation time were proposed. Mean rate coefficients of water-permeation swelling were obtained from the models. The so-obtained rate coefficients predict the solubility of water in the membrane containing surfactants. The model prediction fits the experimental data well. This model can be used to calculate the permeation-swelling ratio for all swelling cases, such as pure water as inner or outer aqueous phase, or two aqueous phases with different electrolyte concentration. It was found that at the late stage of swelling, the hollow-sphere model gives a better prediction. Experimental studies indicate that control of the swelling can be achieved by surfactants that have lower water solubility, such as EM-301. As for effective factors, increasing surfactant concentration resulted in an increased swelling ratio. Different carriers had different effects on the water-permeation swelling ratio, and addition of all kinds of nonphosphatic carriers to the Span-80 membrane caused severe breakage of the membrane.