Anodic oxidation of sulfide ions from chloride brines

The anodic oxidation of sulfide ions from chloride brines at graphite electrodes is shown to produce elemental sulfur, that was identified using XPS and EDS measurements. The process is controlled by charge transfer at the interface and diffusion of the sulfide ions in the electrolyte. Potentiostatic current transients reveal exponential decay of the current with time accompanied by gradual increase of the polarization resistance of the interface, at a rate which increases with increase of the potential in the noble direction. This behavior is attributed to passivation of the electrode by the elemental sulfur which deposits on its surface.