Abstract: A process for biologically enhancing an iron-based redox process for catalytic oxidation of a sulfide compound such as hydrogen sulfide from a gas in a redox system wherein said catalyst comprises a ferric compound and at least one organic chelant capable of holding ferric and ferrous ions in solution at processing temperatures and conditions suitable for generation and retrieval of elemental sulfur, comprising the steps of oxidation of a sulfide compound by a gas with a redox system comprising ferric ions, removal of elemental sulfur from said system, and reoxidation of ferrous ions in the redox system in the presence of a culture of bacteria comprising Thiobacillus ferrooxidans and leptospirillium ferrooxidans at a pH at least as high as about 7.5.

Abstract: In the removal of hydrogen sulfide from a gas stream by use of a liquid catalyst containing ferric ions, the ferric ions of the liquid catalyst are converted to ferrous ions. Regeneration of the ferric ions can be accomplished by bubbling air through the liquid catalyst. A significant decrease in regeneration time for transforming the ferrous ions back to the original ferric ion state can occur when a culture of Thiobacillus ferrooxidans bacteria is introduced to the liquid catalyst. Optimization indicates a pH range between 6.0 and 9.0, a temperature between 20.degree. C. and 45.degree. C. and a cell concentration of 12.5.times.10.sup.8 cells per liter.