Ultrafiltration of oil-in-water emulsion stabilized with surfactants

Abstract

Application of ultrafiltration membrane in the separation of oil-in-water emulsion has a consequence of fouling formation and relate to significantly flux reduction. Filtration of oil-in-water emulsions is challenging since both oil and surfactant have interaction with the membranes. In addition, there is a possibility of droplet deformation to enter the membrane pores. This research was focused on the effect of surfactant type on the ultrafiltration performance. Models of oil-in-water emulsion consisted of crude oil, diesel oil and lubricant oil as dispersed phase and mixture of distilled water with the addition of 0.1% of Tween 80 or Alkyl Benzene Sulfonate as the continuous phase. Flat-sheet Polyethersulfone having 10 kDa molecular weight cut-off was selected as the membrane. The result showed that there were fluxes decline during 2 hours of operation in ultrafiltration of oil-in-water emulsion stabilized with a non-ionic surfactant (Tween 80). On the other hand, when oil-in-water emulsion was stabilized with anionic surfactant (Alkyl Benzene Sulfonate), the fluxes were relatively constant during 2 hours filtration. The COD rejection was in the range of 98-97%, 94-96% and 90-94% for oil types of crude oil, diesel oil and lubricant oil respectively. Total oil content rejection was found as 98-99% for both crude oil and lubricant oil and 98-97% for the diesel oil. Based on Scanning Electron Microscopy, images of the membrane after filtration of oil-in-water emulsion stabilized with Tween 80 showed foulant deposit which was predicted as oil and surfactant. However, when filtering oil-in-water stabilized surfactant only less deposit on the membrane surface was observed.