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Environmental Engineering Research 2001;6(4): 269-275.
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CHANGES IN THE SURFACE TENSION AND CONTACT ANGLE OF EMULSION ACCORDING TO THE AQUATIC INFLUENTIAL FACTORS |
Sung Hye Shin1, Dong Su Kim1†, Woo-Zin Choi2, and Young-Shik Kwon3 |
1Department of Environmental Science and Engineering, Ewha Womans University, Seoul 120-750, Korea 2Department of Environmental Engineering, University of Suwon, Kyunggi-do 445-743, Korea 3Department of Environmental Engineering, Suwon Science College, Kyunggi-do 445-742, Korea |
Corresponding Author:
Dong Su Kim ,Tel: +82-2-3277-2394, Fax: +82-2-3277-3275, Email: dongsu@mm.ewha.ac.kr |
Received: June 6, 2001; Accepted: September 6, 2001. |
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ABSTRACT |
O/W emulsion constitutes one of the major aquatic pollutants because of its complex behavior and long-lasting stability when it is discharged into receiving water. Also, its relatively low biodegradability requires a careful pre-treatment before disposal, since such a property usually results in adverse effects on aquatic environment including complete consumption of dissolved oxygen. In a general term, o/w emulsion can be considered as a colloidal system and, therefore, its physicochemical properties are governed by interfacial influencing parameters. The aim of this study is focused on the investigation of the changes in the principal interfacial characteristics of o/w emulsion such as surface tension and contact angle, which o/w emulsion forms on a hydrophilic substrate, according to major influential factors like oil concentration, pH, and the existence of surfactant. The surface tension of emulsion was observed to decrease with oil content; whereas, the variation of contact angle for glass surface represented the opposite tendency. Considering the practical situation in aquatic system, the equilibrium contact angles, were estimated using Young-Fox -Girifalco equation and compared with experimental ones. The difference between dynamic and equilibrium contact angles suggested a necessity for the reflection of time-influence on the characterization and treatment of o/w emulsion. The effect of pH on the surface tension and contact angle also has been examined and an interpretation of the results based on charge interactions between oil droplets and substrate was attempted. In addition, the surface tension of emulsion was found to be significantly affected by the addition of surfactant. Thinking of the growing occurrence and the difficulties of handling of emulsion-type wastewater, the findings in this study may work as a supportive fundamental and basis for its proper treatment and management. |
Keywords:
contact angle | o/w emulsion | surface tension | wastewater | Young-Fox-Girifalco equation |
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