Chlorine-free electrochemical disinfection using graphene sponge electrodes

TL;DR

This study demonstrates chlorine-free electrochemical disinfection of E. coli using nitrogen-doped reduced graphene oxide sponge electrodes, achieving high removal efficiency without toxic byproducts, and optimizing energy use with capacitive properties.

Contribution

Introduces a novel nitrogen-doped graphene sponge electrode for chlorine-free bacterial inactivation, enhancing efficiency and reducing energy consumption in electro-disinfection.

Findings

Achieved 5 log E. coli removal with the NRGO sponge anode.

Discovered electrosorption and electroporation as key inactivation mechanisms.

Reduced energy consumption by 75% using intermittent current.

Abstract

Graphene sponge electrodes were employed for chlorine-free inactivation of Escherichia coli from low conductivity water. The nitrogen-doped reduced graphene oxide (NRGO) sponge anode bearing more positive charge achieved complete E. coli inactivation (i.e., 5 log removal) in the anode-cathode configuration at 115 A m-2, versus 2.6 log removal using boron-doped reduced graphene oxide sponge anode. The bacteria were mainly inactivated via electrosorption and electroporation, as confirmed by the scanning electron microscopy. Storage of the electrochemically treated samples revealed further killing of the bacteria due to the damaged cell membranes. When using real tap water, 5.5 log E. coli removal required 5.70 kWh m-3, which was drastically lowered to 1.38 kWh m-3 using intermittent current and thus exploiting the capacitive properties of graphene. The developed graphene sponge anode does not form any chlorine, chlorate, or perchlorate, and holds great promise for efficient electro-disinfection without forming toxic disinfection byproducts.