(Electro)catalytic oxidation of sulfide and recovery of elemental sulfur from sulfide-laden streams

MnxOy coated over TiO2 nanotube array substrate was doped with Mo and polyaniline (PANI) and applied for electrochemical desulfurization of concentrated sulfide (HS-) solutions at basic pH, typical of biogas scrubbing solutions and industrial wastewater. Mo and PANI co-dopants significantly enhanced the anode activity towards sulfide oxidation and ensured its complete stability even in highly corrosive sulfide solutions (e.g., 200 mM HS-). This was due to the increased electrochemically active surface area, improved coating conductivity and reduced charge transfer resistance. The (electro)catalytic oxidation of HS- demonstrated robust performance with very limited impact of different operational parameters (e.g., dissolved oxygen, anode potential, HS- concentration). Due to the formation of elemental sulfur (S0) layer at the anode surface at basic pH, longer term anode usage requires its periodic removal. Chemical dissolution of S0 with toluene allows its rapid removal without affecting the anode activity, and easy recrystallization and recovery of pure sulfur.

Automated summary

MnxOy coated TiO2 nanotube array substrate doped with Mo and PANI exhibited excellent activity and stability for electrochemical desulfurization in basic pH conditions. The introduction of Mo and PANI co-dopants increased the electrochemically active surface area, improved coating conductivity, and reduced charge transfer resistance. The catalytic oxidation of sulfide showed minimal impact from different operational parameters, and long-term anode usage requires periodic removal of the formed sulfur layer.