Biocrystallization for elemental sulfur recovery

Summary

This thesis studied a biotechnological process in which naturally occurring microorganisms, let’s call them ‘desulfurizers’, convert toxic and corrosive hydrogen sulfide (H₂S) gas to solid, reusable, and easily recoverable elemental sulfur crystals. H₂S needs to be removed from (bio)gas to prevent sulfur dioxide formation during combustion to avoid the formation of acid rain. By studying the biocrystallization mechanism of biologically formed sulfur, the settleability of the formed crystals was improved. A simple solution was discovered to do so: portion of the H₂S is used to partially dissolve the elemental sulfur crystals. In this process, a soluble sulfur component is formed: polysulfide. Polysulfide formation, and subsequent conversion back to elemental sulfur makes the crystals more prone to agglomeration, which improves their recovery efficiency. The recovered sulfur has many applications, such as reuse in agriculture as fertilizer or fungicide, but also is suitable to apply in industrial processes.