Anodic oxidation of sulphite ions on graphite anodes in alkaline solution

The anodic oxidation of sulphite ions in alkaline 1 M Na2SO4 solution on graphite rotating disc electrodes has been studied over the range from 25 to 60 degrees C. The reaction order with respect to sulphite ions is below 1 at low potentials and 1 at high potentials. The reaction order with respect to hydroxide ions is close to zero. Two Tafel slopes were observed, 0.060 V decade(-1) at low potentials and 0.190.20 V decade(-1) at high potentials. The reaction activation energy was calculated at different potentials. The results obtained, using the potential sweep method, are consistent with those realized using the rotating disc. A possible reaction mechanism has been proposed and the diffusion coefficients of sulphite ions and the diffusion activation energy have been calculated.