Biological desulfurization of coal by mesophilic and thermophilic microorganisms

The biological desulfurization of coals was studied with pure cultures of mesophilic (Thiobacillus ferrooxidans and T. thioodixans) or thermophilic (Sulfolobus brierleyi) bacteria and acid mine water. These microorganisms were used with coals ranging in sulfur contents from 2 to 6%. The extent of removal of sulfur, ash and iron from coal was analyzed in terms of total sulfur, pyritic sulfur, organic sulfur, ash content, and liquid phase iron concentration. With S. brierleyi, CO₂-enriched air resulted in a substantial increase in initial desulfirization rate of pyrite. With acclimated S. brierleyi, 15 to 20% organic sulfur removal was observed. Low-temperature Mössbauer spectroscopy data on iron phases in biotreated coal established that superparamagnetic iron oxyhydroxide (FeOOH) and jarosite were reprecipitated from solution onto the coal particles.