Field-Induced Redistribution of Surfactants at the Oil/Water Interface Reduces Membrane Fouling on Electrically Conducting Carbon Nanotube UF Membranes

Environmental Science & Technology
Xiaobo ZhuDavid Jassby

Abstract

Membrane-based treatment of oily wastewater remains a significant challenge, particularly under high salinity conditions. The main difficulty associated with this separation process is membrane fouling, mostly caused by wetting and coalescence of emulsified oil droplets on the membrane surface. In this study, electrically conducting carbon nanotube-based ultrafiltration membranes were used to treat an emulsified oil suspension at ionic strengths as high as 100 mM. By tuning the electrical potential applied to the membrane surface, we demonstrate how fouling can be dramatically reduced, even under high salinity conditions. Permeate water quality is shown to improve upon application of a negative potential. Using optical microscopy, we observed dramatic changes in the shape of oil droplets at the membrane/water interface in response to the applied electric potential; this change is associated with a redistribution of charged surfactant molecules at the oil/water interface in response to the external electric field. Specifically, using the membrane as a cathode repels surfactant molecules away from the oil/membrane interface, while anodic conditions lead to increased surfactant concentrations. We speculate that this change in surf...Continue Reading

Citations

Aug 6, 2019·ACS Applied Materials & Interfaces·Ping Li, Qingchun Ge

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