Electrically Conducting Carbon Nanotube Polymer Composite Nanofiltration Membranes for Biofouling and Scaling Control

Electrically conducting carbon nanotube – polyamide composite thin-film membranes are demonstrated to have anti-biofouling and anti-scaling properties when an external voltage is applied to the membrane surface. Here, we describe a simple route towards the creation of these membranes, along with detailed material and surface characterization, as well as performance characteristics. The carbon nanotubes are covalently bound through ester bonds with the polyamide salt-rejecting layer to form a polymer nanocomposite that combines the salt rejection characteristics of tight nanofiltration membranes together with the electrical conductivity of carbon nanotubes. The membranes boast high electrical conductivity (400 S/m), good NaCl rejection (>95%), and high water permeability. To test the membrane’s ability to prevent biofouling, we exposed them to very high concentrations of Pseudomonas aeruginosa (10⁸ – 10¹² cell/ml) in 10% LB in a cross-flow filtration setup. Results demonstrate that the applied voltage (1.5 V block current at 16 mHz) stopped the growth of a biofilm over a period of 150 hours. Control experiments demonstrate that it is the presence of an electric charge that foiled biofilm formation. Additionally, we demonstrate that by using the membrane as an anode, CaSO₄ scale formation is effectively slowed on the membrane surface, without the use of anti-scaling chemicals. These membranes potentially offer significant benefits in the areas of wastewater reuse and brackish groundwater desalination.