Fundamental Studies on the Removal
of Emulsified Oil by Chemical
Flocculation
DON   E.   BLOODGOOD
Professor of Sanitary Engineering
WILLIAM   J.   KELLEHER
Graduate Research Assistant
Purdue University, W. Lafayette, Indiana
The National Lime Association is at the present time sponsoring
research at Purdue University with the viewpoint in mind of finding
uses for lime in the treatment and disposal of oil wastes. A rather
extensive survey of the literature concerning oil wastes indicated that
a major problem is caused by the presence of emulsified oil in waste
waters from refineries and metalworking plants. The survey of the
literature further indicated that chemical flocculation has proven successful in some cases for treating wastes containing emulsified oil. It
was thought that since chemical flocculation will often involve the use
of lime, basic laboratory studies on the chemical flocculation of oil
emulsions would prove of benefit. There does not seem to be too
much known about this subject. Before discussing the laboratory
studies that were made, it would perhaps be best to briefly review the
subjects of emulsions and chemical flocculation.
An emulsion may be defined as a mixture of two immiscible liquids,
one of the liquids being dispersed throughout the other in the form of
very fine droplets. If oil is dispersed throughout water the result is
an oil-in-water emulsion (o/w), or if the water is dispersed throughout
the oil the result is a water-in-oil emulsion (w/o). For most emulsions
there is a third constituent necessary, that being an emulsifying agent
which is adsorbed on the surface of the emulsified particles rendering
the emulsion stable. It is possible to have pure o/w emulsions; these
are known as oil hydrosols because the diameter of the emulsified
particles are in the range of 10"5 centimeters. The stability of oil
hydrosols is believed to be caused by the preferential adsorption of
hydroxyl ions with a resulting negative charge on each of the dispersed
oil droplets.
The type of emulsifying agent that stabilizes the emulsion is probably the most important property as far as the stability of emulsions is
concerned.    Sutheim (1) has given an excellent classification as to the
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