To recover metals as sulfide concentrates from contaminated waste streams using hydrogen sulfide (H2S) generated by the bacterial digestion of waste organic materials.
The goal of this research is to develop a treatment method for metal mine effluents that will rival the cost and convenience of conventional lime treatment, and that will provide better effluent water quality, result in less expensive sludge disposal, and allow for the selective recovery of metals.
How it works
In this method (fig. 1), indigenous sulfate-reducing bacteria are used to generate H2S gas in an anaerobic bioreactor containing sulfate-rich mine water and inexpensive, degradable organic matter such as food processing wastes or primary sewage sludge. As H2S is formed, it is sparged from the bioreactor by an inert carrier gas to create a gas stream containing about 0.3 pct H2S. When the gas comes in contact with a metal-contaminated mine effluent, the heavy metals precipitate as relatively insoluble sulfides. Elemental sulfur (S°) also may be formed. By adjusting the pH, the composition of the precipitated concentrates of metal sulfide can be manipulated. For example, the pH of mine water containing Cu, Zn, Fe, Al, and Mn