Preparation and characterization of a new negatively charged polytetrafluoroethylene membrane for treating oilfield wastewater

A novel negatively charged polytetrafluoroethylene (PTFE) membrane has been prepared and characterized. More specifically, the traditional PTFE membrane is pretreated by using the atmospheric pressure glow discharge (APGD) plasma. Then surface of the PTFE membrane after APGD treatment is modified by the photo-induced graft polymerization of 2-acrylamido-2-methyl-propyl-sulfoacid (AMPS). Formation of a polymerized AMPS layer on the PTFE membrane has been detected and confirmed by using the attenuated total reflectance-infrared spectroscopy (ATR-IR) and the scanning electron microscope (SEM) analysis. The optimum grafting efficiency of AMPS is found to achieve at 15.1% volumetric concentration of AMPS monomer, 30 min ultraviolet (UV) irradiation time, and 5.0% volumetric concentration of polymerization initiating agent. The obtained streaming potential and zeta potential of the modified PTFE membrane at various conditions confirm the fact that the modified PTFE membrane is negatively charged. The antifouling test by using oilfield produced water demonstrates that the newly prepared PTFE membrane has an improved antifouling performance compared to the original PTFE membrane.