Electrically conducting duplex-coated gold-PES-UF membrane for capacitive organic fouling mitigation and rejection enhancement
Recent studies showed that the application of an electrical potential onto an ultrafiltration membrane surface exhibit several advantages with respect to the fouling and rejection behaviour. Sputter deposition of ultra-thin metal layers onto commercial flat sheet membranes proved to be a simple way of producing conductive metal-polymer-composite membranes. Adopting the novel approach of duplex-coating the active and support layer of a flat sheet membrane eliminates the need for an additional counter electrode and significantly simplifies module design for conductive flat sheet systems. Cross-flow filtration experiments were conducted with organic model foulants such as sodium alginate, bovine serum albumin (BSA), humic acids as well as with natural organic matter (NOM) from Hohloh lake water. The duplex-coating induced an additional electric field through the membrane itself, resulting in enhanced performance not only for cathodic but also for anodic charging of the active membrane layer. Hohloh lake water fouling experiments showed decreased permeability of 47% for the uncharged membrane to 16% and 38% for the cathodic and anodic charging, respectively. Moreover, a significant increase in NOM-rejection was observed with 27% for the uncharged membrane and 72% and 49% for the cathodic and anodic potentials, respectively. Finally, the effectiveness of externally charged duplex-coated membranes was demonstrated by comparing rejection and fouling rates with conventional membrane-electrode vs. counter electrode configuration, showing an almost similar enhancement in performance.