The role of the surfactant sodium dodecyl sulfate to dynamically reduce mass transfer resistance of SPEEK coated membrane for oil-in-water emulsion treatment

Membrane fouling during the treatment of produced water containing oil emulsions remains a major technical challenge for the oil and gas industry. Here, we demonstrate the preparation and performance of a fouling resistant hollow fiber membrane using a synthetic saline oil-in-water emulsion. The membrane was prepared by coating commercial polyethersulfone (PES) hollow fibers with a layer of sulfonated polyether ether ketone (SPEEK). The SPEEK coated membrane was significantly more oleophobic than the support PES membrane, possibly due to a non-porous surface, higher hydrophilicity, and more negatively charged SPEEK surface. The SPEEK coated membrane could achieve complete oil rejection without any observable membrane fouling and considerably higher salt, turbidity, and sodium dodecyl sulfate (SDS) rejection than the support PES membrane. An initial increase in water flux was observed with the SPEEK coated membrane. The flux increase observed here could be attributed to the incorporation of SDS molecules into SPEEK polymeric network and subsequent electrostatic interaction amongst charged functional groups leading to conformational changes of the SPEEK layer. Dynamic adsorption and desorption experiments illustrated the interaction between SDS and SPEEK. A strong correlation between the amount of SDS entrapped in the SPEEK polymeric network and water flux was observed. Results from this study illustrated the potential of SPEEK coated membrane as a major breakthrough for oil recovery and wastewater reuse in the oil and gas industry.