Surface modified spherical activated carbon for high carbon loading and its desalting performance in flow electrode capacitive deionization
We have synthesized a new type of activated carbon (AC) containing ion selective functional groups, trimethylammonium (AC N) for anodes and sulfonate (AC S) for cathodes, for high carbon loading of flow electrodes. The AC N and AC S were partially covered with a 50 nm thick polymer layer and their surfaces became more hydrophilic than that of bare AC. In the case of bare AC, the maximum carbon concentration in the flow electrodes was 10% while in the case of the surface modified AC (AC N and AC S) it increased to a maximum of 35% and decreased the viscosity due to the electrostatic repulsion. Moreover, with the increase in carbon concentration, the salt removal efficiencies were improved from 8.2% to 27.7% This increase in efficiency was attributed to the formation of percolating networks, which occurred because of high carbon loading. The resulting improvement in electronic conductivity at higher loading led to a higher current, and thus an improved salt removal efficiency. Therefore, we expect that the surface modified AC electrode can be used as a dispersant for hydrophobic AC particles in aqueous solution, as well as in flow electrodes to improve desalting performance in FCDI systems.