CHEMICAL DEMULSIFICATION OF OIL-IN-WATER EMULSION USING AIR-FLOTATION- THE IMPORTANCE OF FILM THICKNESS STABILITY

The thickness stability of the film between air bubble/oil drop and oi l/oil drops in an induced air flotation process in the presence of flo cculent was analyzed. A cationic, high molecular weight, polymeric flo cculent was used in the demulsification of a crude oil-in-water emulsi on. A novel capillary force balance technique in conjunction with the him interference microscopy was used to study the film thickness stabi lity of an emulsion Nm formed between oil drops and pseudoemulsion fil m formed between air bubbles and oil drops. It has been found that fil m thickness stability is related to the formation of dark spots (thinn er area) inside the him. The formation of dark spots inside the thinni ng film has been explained by the local osmotic depletion-destabilizat ion effect. It has been found that in the presence of the flocculent t he emulsion film is less stable than the pseudoemulsion film, and the efficiency of the oil separation process by air flotation is therefore governed by the stability of the water emulsion film. The flocculent improves oil spreading on the water-air surface, thereby enhancing sep aration efficiency.