A NEW ELECTROCHEMICAL PROCESS FOR TREATING
SPENT EMULSIONS
Dexter D. Snyder, Senior Research Chemist
Electrochemistry Department
Research Laboratories
General Motors Corporation
Warren, Michigan 48090
Robert A. Willihnganz, Senior Engineer
Energy and Environmental Engineering
Manufacturing Development
General Motors Corporation
Warren, Michigan 48090
INTRODUCTION
Breaking of oil-in-water emulsions is a major waste-handling problem for automotive
and other manufacturing plants involved with the cutting, machining and grinding of
metals.   The individual plant wastes-including "soluble oil" emulsions, cutting fluids,
and cleaners-are typically combined and treated with chemicals to separate oil and water.
Acid-alum-lime, the most widely used chemical treatment, generates an oil sludge and
adds dissolved solids to the effluent water.   Regulatory standards for oil in plant effluent
are on the order of 100 ppm total Freon extractables for discharge to a municipal system
and 10 to 25 ppm total Freon extractables for discharge to surface waters.   Standards
are also being formulated to limit dissolved solids in effluent and to tighten control over
landfilling of oily sludge.   These pressures are making nonchemical approaches to emulsion
breaking and oil-water separation, applied at the source of waste, ever more attractive.
Several approaches have been tried to break emulsions and separate oil without the
need for chemical additives, including ultrafiltration [1], electrolysis [2,3], adsorption/
absorption, adsorption flotation, magnetization, layer filtration, centrifuging, heating and
freezing.   Wang has summarized the state-of-the-art and given the pertinent references [4],
Our efforts have focused on electrochemical and ultrafiltration technologies.
Ultrafiltration has proved highly effective in separating water from "soluble oil" emulsions, producing a clear effluent and concentrating the emulsified oil droplets [1,5].
However, since ultrafiltration does not break the emulsion, the concentrate must be further treated to recover or dispose of the oil.   Also, the water flux decreases as the oil
content of the emulsion increases, according to the relation:
J  = k Kn   £• (1)
where       J ■ water flux
k = aqueous phase mass transfer coefficient
C* " constant
C = oil concentration of feed
For one typical "soluble oil" waste treated in a commerical ultrafilter, the water flux became negligible when feed concentration reached about 50 v/o [5].
Electrochemical approaches to separating oil-in-water emulsions have been restricted
to electroflotation for removal of the oil from an emulsion which has been broken with
chemical additives [2].   Bier has exploited the electrophoretic migration of charged particles to purify and concentrate biological particles such as plasma proteins [6].   Anderson
recently described a system for recovering animal fats and oils from wastewater by electro-
lyzing the stream in a tank of special design [3].  Gilchrist has patented a related method
for recovering electrocoating components from waste by transporting them electrophoret-
ically through a porous separator [7].
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