Carbon Nanotube/Graphene Composite Membrane for Self-Cleaning of Biofouling Via Bubble Generation

Biofouling is a major operational problem in membrane-based filtration processes owing to the formation of intractable biofilms. Recently, electrically conductive membranes have attracted significant interest for fouling mitigation by membrane self-cleaning. However, the water flux due to electrochemical self-cleaning using bubble generation on the cathode does not achieve complete water flux recovery, and the cause of this was not clearly identified. In this study, we fabricated a carbon nanotube (CNT)/graphene membrane that exhibits high stability even under high voltage (i.e., 15 V). The self-cleaning effect was investigated under applied voltages and self-cleaning times and evaluated by water flux recovery and quantitative biofilm analysis. The developed self-cleaning membrane achieved more than 4 log viable cell removal and 95.2% total EPS removal in 10 min on the membrane surface. Through filtration and self-cleaning cycles, 100% water flux recovery was achieved, and the stability of the CNT/graphene membrane was verified. It was confirmed that the insufficient recovery of self-cleaning through conventional water electrolysis is due to the residual biofilm matrix, and the water flux recovery efficiency was improved using high voltage, suggesting that this can be overcome by a combination of physical cleaning method