Continuous separation and recovery of high viscosity oil from oil-in-water emulsion through nondispersive solvent extraction using hydrophobic nanofibrous poly(vinylidene fluoride) membrane

Abstract

Membrane separation has been considered as a promising technology for oily wastewater treatment. However, membrane fouling significantly limited its practical applications especially for oils with high viscosity and concentration. In this study, we propose membrane based nondispersive solvent extraction for continuous separation and recovery oils with high viscosity and concentration from oil-in-water emulsion. In this process, oil-in-water emulsion and extraction solution (hexane) was separated by a porous hydrophobic poly (vinylidene fluoride) (PVDF) nanofibrous membrane and flowed on each side of the membrane. The strong affinity of PVDF membrane and high solubility of hexane towards oil (e.g., lubricant oil) endowed continuous transfer of oil from emulsion side to hexane side. Different from conventional physical sieving, fouling enhanced transfer of lubricant oil in this process. Lubricant oil flux was up to about 336 g/m2 when 1% lubricant oil-in-water emulsion was used and increased to 935 g/m2 in case of 10%. Moreover, lubricant oil can be easily recovered through hexane evaporation both in low (17oC) and relative high temperature (67oC). Water content of recovered oil (0.10 ± 0.02%) was almost the same as original samples (0.11 ± 0.02%). Strategy proposed in the current study offers an effective way for treating oil-in-water emulsion with high viscosity and concentration.