Electrochemical Carbon Nanotube Filter for Adsorption, Desorption, and Oxidation of Aqueous Dyes and Anions

An electrochemically active multiwalled carbon nanotube (MWNT) filter is observed to be effective toward the adsorptive removal and electrochemical oxidation of the aqueous dyes, methylene blue and methyl orange, and the oxidation of the aqueous anions, chloride and iodide. In the absence of electrochemistry, the MWNT filter completely removed all dye from the influent solution until a near monolayer of dye molecules adsorbed to the MWNT filter surface. Electrochemical filtration at 2 V resulted in > 98% oxidation of the influent dye during a single pass through the 41 mu m thin porous MWNT network with a <= 1.2 s residence time. The electrochemical MWNT filter was also able to oxidize aqueous chloride and iodide with minimal overpotential. However, the oxidation of these anions was limited by the number of electrochemically active MWNT surface sites. These results show the potential of an electrochemical MWNT filter for the adsorptive removal and oxidative degradation of aqueous contaminants.