Development of New Surfactant for Liquid Surfactant Membrane

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To develop and design a liquid surfactant membrane (LSM) process, it is important to elucidate the role of a surfactant on the behavior of LSM, that is, the membrane stability, the permeation rate of metals, and the demulsification rate of emulsions.In this study, a series of surfactants (nonionic, anionic, cationic, amphoteric) having two long alkyl chains were synthesized. The effect of new surfactants on the behavior of LSM was investigated, and the following results were obtained.1. Synthesized surfactants gave more stable emulsion at a lower concentration compared with commercial surfactants of Span 80 and Polyamine. Among them, a derivative of glutamic acid dioleyl ester formed the most stable LSM.2. Using the newly synthesized surfactants, metal extraction by LSM was carried out in a stirred tank. The extraction rate of copper by LSM was explained by means of the interfacial reaction model. The surfactant strongly affects the permeation rate of metal ions in the LSM process. New phosphoric and sulfonic acid surfactants accelerated the extraction rate of copper because of the electrostatic interaction. On the other hand, when another extractant (PC-88A) was used in the extraction of rare earth metals, the extraction rate and separation factor were enhanced by use of new cationic suractant.3. Demulsification of W/O emulsions was carried out by a continuous electrical coalescer. The demulsification rate was influenced by the properties of W/O emulsion, applied voltage, and mean residence time, and the experimental equation taking these contributions into account was presented.