Biochemical removal of HAP precursors from coal. Technical progress report, January--March 1996

Shake flask bioleaching tests were conducted with Pittsburgh NO. 8 and Indiana No. 5 coal. Bacteria removed pyritic sulfur from both coals at maximum rates of 5 to 9% per day, which was about 20 times the abiotic rate of pyrite oxidation. Concentrations of inorganic hazardous air pollutant (HAP) precursor elements in starting coal, bioleached coal and in leach solutions were measured. Of the 13 HAP precursors, significant amounts of arsenic, cobalt, cadmium, manganese, and nickel were removed from both coals by bacterial activity and also by the acidic leach solutions in control flasks. Little or no mercury, lead, beryllium, chromium, antimony, fluorine or chlorine was removed from the coals. Selenium was bioleached from both coals as determined by analysis of Se in leach solutions. However, analyses of Se in starting coal and in coal residues remains problematic. With very few exceptions, mass balances for the HAP precursors ranged from 80 to 120%. Improved analytical methods were developed for measuring concentrations of Hg, Se, As, and Sb in coal. Shake flask tests with pyrite oxidizing bacteria were conducted on Pittsburgh No. 8 and Indiana No. 5 coal. Concentrations of HAP precursors in the starting coal, leach solutions, and final coal residues were measured. A column leaching-rotating biological contactor (RBC) unit was assembled and a column leach test with Pittsburgh No. 8 coal was begun