Bioleaching of trace elements from US coals by pyrite-oxidizing bacteria

Pyrite oxidizing bacteria removed a portion of several trace elements from four U.S. coals. Significant percentages of As, Ni, Mn, Co, and Cd were bio leached from Pittsburgh No. 8, Indiana No. 5 and Kentucky No. 9 coals. Pyri te was removed to a greater extent than any of the 13 trace elements studie d. Hg, the trace element most likely to be regulated in the future in power plant emissions, was not removed from any of the coals by bioleaching with mesophilic or thermophilic microorganisms. However, most of the Hg in Pitt sburgh coal could be removed by leaching with HCl following microbial pyrit e oxidation. Hg might be more efficiently removed from coal by physical pro cesses following bioleaching with thermophilic pyrite-oxidizing microorgani sms.