Active demulsification of stable emulsions using light

16^th International Conference on Emerging Materials and Nanotechnology

March 22-23, 2018 | London, UK

Yukishige Kondo

Tokyo University of Science, Japan

Scientific Tracks Abstracts: J Material Sci Eng

Abstract :

Emulsions are metastable systems where one liquid (dispersoid) is dispersed as particles in another liquid (dispersion medium), and have been used in many fields, including cosmetics and paints. Many research has focused on the enhancement of emulsion stability. On the other hand, Demulsification, which is a phase separation phenomenon of stable emulsions, also plays an important role in industry. For example, aqueous waste fluids containing hazardous substances can be mixed with an oil to obtain an emulsion, and then the emulsion is demulsified to extract hazardous substances into the oil phase. This process is called â�?�?emulsion liquid membrane extractionâ�?. Demulsification has been so far performed by adding chemicals or by physical techniques such as the application of high electrical fields, or mechanical external forces and the variation of temperature. In this work, we will focus on the control over the stability of emulsions by an external stimulus, which is light. As a photo-responsive surfactant, a cationic gemini surfactant having an azobenzene group (C7-azo-C7) has been synthesized. C7-azo-C7 exhibits photo-isomerization between trans and cis isomers. When mixtures of trans-C7-azo-C7 aqueous solution and n-octane were homogenized, stableemulsions were obtained in a specific region of weight fractionand surfactant concentration. Fluorescence microscopy observations using a small amount of fluorescent probes showedthat the stable emulsions were oil-in-water (O/W)-type. As can be seen in Figure 1, UV irradiation of stable O/W emulsions promoted the cis isomerization of trans-C7azo-C7 and led to the demulsification. Dynamic interfacial tension between aqueous C7azo-C7 solution and octane temporarily increased with UV light irradiation. From these results, the cis isomerization of transC7-azo-C7 molecules at the O/W interface on UV irradiation leads to direct contact between the water and octane phases, because of the reduction of molecular area at the interface, and subsequently makes the emulsions demulsified.

Biography :

Yukishige Kondo received his B. Eng. in Chemical Engineering from the Tokyo University of Science (TUS) and earned his Dr. Eng. for his doctoral thesis concerning “Solubilization of organic compounds using surfactant vesicles”. His professional career started by joining the faculty at the Department of Industrial Chemistry, TUS. After he worked as a visiting assistant professor at University of Wisconsin–Madison from 2004 to 2005, he was promoted to Professor in 2015. He is working on “the synthesis of novel surfactants and their solution properties” and “preparation of metal-lustrous crystals using organic compounds” along with 24 students. He has a fascination for aircraft; he enjoys watching airplanes at airports and traveling by air.
Email:ykondo@rs.tus.ac.jp