Electrochemical water treatment has potential to be an energy positive process.  Here, we examine the potential of an electrochemical CNT filter towards utilization of wastewater as a sacrificial electron donor for cathodic hydrogen production.  An anodic CNT filter has been observed to be effective and efficient for the degradation of a number of organics, so the talk will focus primarily on cathodic hydrogen production using ferrocyanide as a model, non-adsorbing electron donor.  At low potentials, the cathodic hydrogen production was indirectly determined via simple aqueous effluent measurements of pH, dissolved oxygen, total inorganic carbon, and oxidation products.  Electron and mass conservation indicated that hydrogen production was the predominant cathodic process.  The hydrogen production energy efficiency is greatly improved by use of a CNT filter cathode as compared to a perforated metal cathode.  The potential for the onset of hydrogen production with the CNT cathode is significantly lower than predicted by the Nerst equation and the influent/effluent pH suggesting the effective CNT surface pH is much lower than the bulk.  The electrochemical hydrogen production rate is observed to increase linearly with increasing liquid flow rate due to convective mass transfer enhancements.  The current efficiency is also observed to increase with increasing flow rate, which is likely due to reduction of null cycle current.  Potential of the electrochemical CNT filter for wastewater-to-hydrogen transformation is discussed.

Electrochemical carbon nanotube filter for simultaneous anodic wastewater oxidation and cathodic hydrogen production

245th National Meeting (2013)

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