We have investigated electrochemical treatment of real domestic wastewater coupled with simultaneous production of molecular H2 as useful by-product. The electrolysis cells employ multi-layer semiconductor anodes with electro-active bismuth-doped TiO2 functionalities  and stainless steel cathodes. DC-powered Laboratory-scale electrolysis experiments were performed under static anodic potentials (+2.2 or +3.0 V NHE) using domestic wastewater samples,  with added  chloride ion in variable concentrations. Greater than 95% reductions in chemical oxygen demand (COD) and ammonium ion were achieved within 6 hours. In addition, we experimentally determined a decreasing overall reactivity of reactive chlorine species towards COD with an increasing chloride ion concentration under chlorine radicals (Cl�, Cl2��) generation at +3.0 V NHE. The current efficiency for COD removal was 12% with the lowest specific energy consumption of 96 kWh kg/COD at the cell voltage of near 4 V in 50 mM chloride. The current efficiency and energy efficiency for H2 generation were calculated to range from 34 to 84% and 14 to 26%, respectively. The hydrogen comprised 35 to 60% by volume of evolved gases. The efficacy of our electrolysis cell was further demonstrated by  a 20 L prototype  reactor totally powered by a photovoltaic (PV) panel, which was shown to eliminate COD and total coliform bacteria in less than 4 hours of treatment.

Effects of anodic potential and chloride ion on overall reactivity in semiconductor electrochemical reactors

248th National Meeting (2014)

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