Recovery of Hydrogen and Sulfur by Indirect Electrolysis of Hydrogen Sulfide

Hydrogen sulfide (H 2 S) absorption and conversion to hydrogen and sulfur were carried out in an acidic aqueous vanadium dioxide (VO 2 ) + solution coupled with indirect electrolysis. In this paper, the mechanisms of absorption and electrochemical reactions of the process are discussed. Parametric studies were conducted to determine the effects of operating parameters on absorption and electrochemical reactions. The results showed that the H 2 S absorption increased with temperature; greater than 90% of H 2 S absorption occurred at 50 °C. The absorption reaction was mass-transfer-limiting. In the electrolysis reaction, the current efficiency reached 97% at 45 °C after an extended electrolysis time. The optimal reaction conditions were at a proton concentration of 7 mol/kg of H 2 O in the electrolyte, (VO 2 ) + concentration of lower than 0.65 mol/kg of H 2 O in the electrolyte, and (VO 2 ) + concentration of higher than 0.55 mol/kg of H 2 O in the absorbent. Sulfur particles that are produced can be easily recovered. Some aspects related to design optimization of the absorption process and electrochemical reactor are also discussed.