The separation of oil in water (O/W) emulsions using polyether sulfone & nitrocellulose microfiltration membranes

The practical and energy efficient treatment of oil-water mixtures, especially those stabilized by surfactants, has proven to be challenging. To cope with this challenge, two commercial microfiltration membranes [Polyester sulfone (PES) and Nitrocellulose (NCL)] were analyzed using a number of characterization methods and used for the separation of micrometer sized oil in water (O/W) emulsions. The emulsions were prepared with hexane-water and dodecane-water, respectively, and stabilized by the surfactant of sodium dodecyl sulfate (SDS). The separation experiments were conducted at the trans-membrane pressure of 0.1 bar. The membranes showed superhydrophilicity and underwater oleophobicity with the oil contact angles of 147 degrees and 137 degrees in water for PES and NCL membranes, respectively. PES membrane obtained a better separation efficiency of 98.9% while NCL membranes achieved a higher flux of 3412.2 L/m(2)/h for separating dodecane O/W emulsion. The cyclic and differential filtration experiments suggested that both membranes can be easily fouled by large oil molecules (dodecane), which may decrease the initial flux by more than half in less than a minute. The results provided benchmarks for future researches on the treatment of produced oily wastewater from industry and daily life.