Papers by Keyword: Pyrite Oxidation

Abstract: Thermotolerant “Thiobacillus prosperus”-like bacteria were enriched from warm, acidic sediments of the island of Milos in the Aegean Sea. Analysis of 16S rRNA gene sequences indicated at least two thermotolerant species, with at least one of them present in similar niches at Vulcano, Italy. Iron solubilization in a pyrite-enrichment culture at 47°C was most rapid in the presence of NaCl at 30 g.l 1. One of the novel species (strain M7) grew in pure culture on pyrite with NaCl at 50 g.l-1, but iron solubilization was most rapid with 20 g NaCl.l 1 at just below 50°C.

Abstract: The geomicrobiology of sulfidic mine dumps is reviewed. More than 30 microbiological studies of sulfidic mine dumps have been published. Mainly culturing approaches such as most probable number (MPN) or agar plates were used to study the microbial communities. More recently, molecular biological techniques such as FISH, CARD-FISH, Q-PCR, T-RFLP, DGGE, or cloning have been applied to quantify microorganisms and to investigate the microbial diversity. Aerobic Fe(II)- and sulfur compound oxidizing microorganisms oxidize pyrite, pyrrhotite and other metal sulfides and play an important role in the formation of acid mine drainage (AMD). Anaerobic microorganisms such as Fe(III)-reducing microorganisms dissolve Fe(III)(hydr)oxides and may thereby release adsorbed or precipitated metals. Sulfate-reducing microorganisms precipitate and immobilize metals. In addition to the microbial communities several biogeochemical processes have been analyzed in mine dumps. Pyrite or pyrrhotite oxidation rates have been measured by different techniques: Column experiments, humidity cells, microcalorimetry, or oxygen consumption measurements. Analyses of stable isotopes of iron, oxygen and sulfur have yielded valuable information on biogeochemical reactions. The microbiology and the biogeochemical processes in sulfidic mine dumps have to be understood for control and prevention of AMD generation and to provide different possibilities for remediation concepts. Today, remediation measures, e.g. under water storage of the waste or covering of the dumps, focus on the inhibition of pyrite oxidation to keep the toxic compounds inside the mine waste dumps. As an alternative to the inhibition of pyrite oxidation, metals which also have economic value could be extracted from mine dumps by the application of different metal extraction technologies including bioleaching.

Abstract: To enhance our understanding of effects of microbially mediated pyrite dissolution and the influence parameters such as varied metabolism and crystallographic orientation of pyrite surfaces some dissolution experiments were performed. Microbial etching experiments on pyrite surfaces of different orientation, including {111} and {210} were devised. The experiments were performed using two strains of thermophilic Archaea (Sulfolobus metallicus, Metallosphaera sedula). Epifluorescence microscopy observations showed that the strains attach to the mineral surface. Studies with Scanning Electron Microscopy (SEM) showed cell attachment and etching effects after one week of incubation. Surface alteration produced structures following crystallographic orientation up to several 10 μm in size. For all incubated pyrite samples it became apparent that surface alteration was more pronounced with M. sedula than with S. metallicus.