Electrochemical sulfide oxidation from domestic wastewater using mixed metal-coated titanium electrodes

Hydrogen sulfide generation is a major issue in sewer management. A novel method based on electrochemical sulfide oxidation was recently shown to be highly effective for sulfide removal from synthetic and real sewage. Here, we compare the performance of five different mixed metal oxide (MMO) coated titanium electrode materials for the electrochemical removal of sulfide from domestic wastewater. All electrode materials performed similarly in terms of sulfide removal, removing 78 ± 5%, 77 ± 1%, 85 ± 4%, 84 ± 1%, and 83 ± 2% at a current density of 10 mA/cm2 using Ta/Ir, Ru/Ir, Pt/Ir, SnO2 and PbO2, respectively. Elevated chloride concentrations, often observed in coastal areas, did not entail any significant difference in performance. Independent of the electrode material used, sulfide oxidation by in situ generated oxygen was the predominant reaction mechanism. Passivation of the electrode surface by deposition of elemental sulfur did not occur. However, scaling was observed in the cathode compartment. This study shows that all the MMO coated titanium electrode materials studied are suitable anodic materials for sulfide removal from wastewater. Ta/Ir and Pt/Ir coated titanium electrodes seem the most suitable electrodes since they possess the lowest overpotential for oxygen evolution, are stable at low chloride concentration and are already used in full scale applications.

► There was no significant impact of electrode coating on the electrochemical sulfide oxidation in domestic wastewater using 5 different MMO coated titanium electrodes.
► The average sulfide removal efficiency was ∼80% and appeared independent of electrode material used.
► Elevated chloride concentrations did not have a significant impact on the sulfide removal efficiency and final products of oxidation.
► Scaling of the membrane and the electrode was observed in the cathode chamber due to transport of bivalent cations such as calcium through the cation exchange membrane.