MICROSCOPIC CHARACTERIZATION OF OIL DROPLETS REMOVED BY FLOCS AFTER COAGULATION OF OIL–WATER EMULSIONS

ABSTRACT

The objectives of this study were to investigate floc–droplet interactions during coagulation of oil–water emulsions and understand mechanisms of removal for selected hydrocarbons from aqueous solutions by analysis of microscopic images of the flocs formed after coagulation. Image analysis techniques were used to examine and statistically evaluate surface and structural characteristics of the flocs and oil droplets attached on the flocs. The coagulation experiments were conducted using standard jar test procedure to identify the optimum conditions for removal of decane, styrene, toluene and m-xylene from surface water samples. Removal effectiveness of the hydrocarbons was determined by gas chromatography analyses of the water samples before and after coagulation. The size distribution of the droplets which were attached on the flocs showed a significantly skewed pattern towards the smaller diameter droplets indicating that there is a characteristic droplet size range for attachment of droplets on the forming flocs. Percent removal of hydrocarbons increased as a function of log K _ow of the contaminants used in the study. The image analysis techniques used for the examination of flocs provided information on specific floc properties as well as insight on removal mechanisms of droplets from emulsions.

Keywords:

• Coagulation
• Adsorption
• Flocculation
• Emulsions
• Hydrocarbons
• Organic removal
• Floc morphology
• Image analysis
• Microscopy

ACKNOWLEDGMENT

The image analysis system used in this study was acquired by a grant from U.S. Army Research Office.