Electrochemical treatment of chromium-containing wastewater has the advantage of simultaneously reducing hexavalent chromium (Cr.sup.VI) and reversibly adsorbing the trivalent product (Cr.sup.III), thereby minimizing the generation of waste for disposal and providing an opportunity for resource reuse. The application of electrochemical treatment of chromium can be often limited by the available electrochemical surface area (ESA) of conventional electrodes with flat surfaces. Here, the preparation and evaluation of carbon nanotube (CNT) electrodes containing of vertically aligned CNT arrays directly grown on stainless steel mesh (SSM). The 3-D organization of CNT arrays increases ESA up to 13 times compared to SSM. The increase of ESA can be correlated with the length of CNTs, consistent with a mechanism of roughness-induced ESA enhancemen, and the increase directly benefits Cr.sup.VI reduction by proportionally accelerating reduction without compromising the electrode's ability to adsorb Cr.sup.III. The results suggest that the rational design of electrodes with hierarchical structures represents a feasible approach to improve the performance of electrochemical treatment of contaminated water.
STATEMENT REGARDING FEDERALLY SPONSORED R&D
 This invention was made with government support under CBET-1033848 awarded by the National Science Foundation and CFP-12-3923 awarded by the Department of Energy. The government has certain rights in the invention.