Activated Carbon as a Cathode for Water Disinfection through the Electro-Fenton Process

Unlike many other water disinfection methods, hydroxyl radicals (HO^•) produced by the Fenton reaction (Fe²⁺/H₂O₂) can inactivate pathogens regardless of taxonomic identity of genetic potential and do not generate halogenated disinfection by-products. Hydrogen peroxide (H₂O₂) required for the process is typically electrogenerated using various carbonaceous materials as cathodes. However, high costs and necessary modifications to the cathodes still present a challenge to large-scale implementation. In this work, we use granular activated carbon (GAC) as a cathode to generate H₂O₂ for water disinfection through the electro-Fenton process. GAC is a low-cost amorphous carbon with abundant oxygen- and carbon-containing groups that are favored for oxygen reduction into H₂O₂. Results indicate that H₂O₂ production at the GAC cathode is higher with more GAC, lower pH, and smaller reactor volume. Through the addition of iron ions, the electrogenerated H₂O₂ is transformed into HO^• that efficiently inactivated model pathogen (Escherichia coli) under various water chemistry conditions. Chick-Watson modeling results further showed the strong lethality of produced HO^• from the electro-Fenton process. This inactivation coupled with high H₂O₂ yield, excellent reusability, and relatively low cost of GAC proves that GAC is a promising cathodic material for large-scale water disinfection.