Electrochemically-active carbon nanotube coatings for biofouling mitigation: Cleaning kinetics and energy consumption for cathodic and anodic regimes

Abstract

Biofouling is a major obstacle in engineered systems exposed to aqueous conditions. Many attempts have been made to engineer the surface properties of materials to render them resistant to biofouling. These modifications typically rely on passive antimicrobial or anti-adhesive surface coatings that prevent the deposition of bacteria or inactivate them once they reach the surface. However, no surface modification strategy completely prevents biofilm formation, and, over time, surfaces will be fouled and require cleaning. In this work, we demonstrate the capacity of electrochemical carbon nanotube coatings in dispersing biofilms formed on the surface. A systematic analysis of the biofilm removal kinetics in function of applied current density is made to identify the optimal current conditions needed for efficient surface cleaning. Operating the electrochemically active surface as a cathode produces superior results compared to when it is operated as an anode. Specifically, the 5.00 A m^-2 and 2.50 A m^-2 cathodic conditions produced rapid cleaning, with complete biofilm dispersal after 2 min of operation. Surface cleaning is attributed to the generation of microbubbles on the surface that scours the surface to remove the adhered biofilm. Energy consumption analyses indicate that the 2.50 A m^-2 cathodic condition offers the best combination of cleaning kinetics and energy consumption achieving 99% biofilm removal at an energy cost of ~$ 0.0318 m^-2. This approach can be competitive compared to the current chemical cleaning strategies, while offering an opportunity for a more sustainable and integrated approach for biofouling management in engineered systems.

Keywords: Biofouling; Carbon nanotubes; Coatings; Electrochemistry; Self-cleaning.