كليدواژه :
Iron , Anglesite , thiosulphat , Biological catalys , Polysulfide
چكيده لاتين :
Biological catalyst is a simple and effective technology for metal extraction from low-grade contaminated soils and mineral concentrates. Metal removing from sulfide minerals is based on the activity of mesophilic and chemolithotrophic bacteria, the use of microorganis bacteria in the process of lead and iron leaching from sulphid ore investigated. Bioleaching of metal sulfides is caused by astonishingly diverse groups of bacteria. Today, at least 11 putative prokaryotic divisions can be related to this phenomenon. In contrast, the dissolution (bio) chemistry of metal sulfides follows only two pathways, which are determined by the acid-solubility of the sulfides: the thiosulfate and the polysulfide pathway. The bacterial cell can affect this sulfide dissolution by contact and non-contact mechanisms. The non-contact mechanism assumes that the bacteria oxidize only dissolved iron (II) ions to iron III) ions. The latter can then attack metal sulfides and be reduced to iron (II) ions. The contact mechanism requires attachment of bacteria to the sulfide surface. The primary mechanism for attachment to pyrite is electrostatic in nature. In the case of Acidithiobacillus ferrooxidans, bacterial exopolymers contain iron (III) ions, each complexed by two uronic acid residues. The resulting positive charge allows attachment to the negatively charged pyrite. Thus, the first function of complexed iron (III) ions in the contact mechanism is mediation of cell attachment, while their second function is oxidative dissolution of the metal sulfide, similar to the role of free iron (III) ions in the non-contactmechanism. In both cases, the electrons extracted from the metal sulfide reduce molecular oxygen via a complex redox chain located below the outer membrane, the periplasmic space, and the cytoplasmic membrane of leaching bacteria. The dominance of either At. ferrooxidans or Leptospirillum ferrooxidans in mesophilic leaching habitats is highly likely to result from differences in their biochemical iron(II) oxidation pathways, especially the involvement of rusticyanin.
