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Abstract

A carbon fiber electrode is coated with a noble metal oxide to create a noble metal oxide electrode with a very large surface area. According to a presently preferred embodiment, the noble metal oxide is iridium oxide. A method of making the electrode includes preparing a solution of iridium chloride and isopropyl alcohol, dipping a carbon fiber electrode into the solution, drying the electrode in the presence of nitrogen and heat, and heat treating the electrode in the presence of oxygen. An apparatus for removing nitrates from water includes an electrochemical flow cell through which the aqueous solution containing nitrates flows or a holding tank cell into which the solution is introduced and then released after processing, and an electrode system including an anodic iridium oxide coated carbon fiber electrode as described above, a carbon fiber cathodic electrode and a reference electrode. All of the electrodes are immersed in the aqueous solution and coupled to an electronic control circuit which impresses a voltage across the electrodes such that the voltage causes electrochemical reduction/oxidation reactions on the surface of the cathodic electrode. The electrodes are at a potential wherein nitrates are reduced but hydrogen, oxygen, and chlorine are not produced. Electrodes having different geometries are also provided.

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