Koh M  Yoo J  Park K  Kim H  Kim H

Vol. 10,  No. 4, pp. 221-228, Dec.  2004

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Ethoxylated Nonyl Phenol Series (NP-series), nonionic surfactants, were applied for forming microemulsions in supercritical CO2. Measurement results of the solubility in supercritical CO2 are in the following; NP-series were high soluble in carbon dioxide in spite of the fact that those were not CO2-philic surfactants traditionally well known. Water in CO2 microemulsions were also formed stably. Acomplexation of hydrophilic lengths for CO2-philic parts of NP-Series surfactants was optimized by NP-4 surfactant(N=4) for forming the microemulsions through the experiments. Formation of microemulsions was confirmed by measuring the UV-Visible spectrum through a spectroscopic method and existence of water in the microemulsions was confirmed as well. In order to apply it for a metal surface treatment or electroplating, an experiment for forming acid(organic, inorganic) solution in CO2 microemulsions was carried out. Ionic surfactant in the reaction to an acid solution became unstable to form microemulsions, however, nonionic surfactant was formed stably in the reaction. Results of the study will be utilized for expanding the application scope of supercritical CO2 which is an environmental-friendly solvent.