ELECTROCHEMICAL WASTE-WATER TREATMENT USING HIGH OVERVOLTAGE ANODES .1. PHYSICAL AND ELECTROCHEMICAL PROPERTIES OF SNO2 ANODES

The electrochemical performance of SnO2 as an anode material with high oxygen gas-evolution over-potential was investigated in view of its application for electrochemical oxidation of bio-refractory organics in waste waters. The influence of the doping agent (Sb, F, Cl) and doping level on the oxygen-evolution reaction was studied in terms of Tafel slope, oxygen-overpotential and exchange current densities for the Ce3+ --> Ce4+ reaction. Tafel slopes of about 300 mV decade-1 were found and the oxygen evolution overpotential was 600 mV higher than that of platinum. While the doping level had no significant influence of Tafel slopes and oxygen overpotentials the stability of the SnO2 electrode increased with charge carrier density. The oxidation of phenol was investigated as a test for the oxidizing power of the new anode material when compared to Pt or PbO2. The rate of phenol removal was much higher for SnO2 than for PbO2 or Pt.