A feasibility study on the reclamation of coal waste dumps by bacterial leaching
Brogan coal containing mean averages of 6,93% w/w total sulphur (1.1% sulphate sulphur, 1.6% organic sulphur and 4.24% pyritic sulphur) and 16.34% mineral ash was used as the test coal in these studies.
Shake-culture leaching studies on seven size fractions of the coal, ranging in size from 0.045 mm to 1.7 mm, showed that the rate of pyrite leaching was inversely proportional to the particle size. As the use of continuous stirred tank reactors would be uneconomical for the reclamation of waste coal, column leaching studies were initiated on coal sieved to > 6.35 mm to < 12.7 mm. The leachate was monitored for all metal ions and the release of iron was used to monitor the rate of pyrite oxidation. Measurable amounts of Zn, Co, Ni, Mn, and V, all of which can replace iron in the pyrite crystal structure, were released during the initial stages of leaching. Further, high concentrations of Al, Ca and Sr and trace amounts of Sn, As, Se, B, Ca, Cr, Si, and Ti were detected in the column effluents.
These studies suggest that bacterial leaching will remove the pyrite and qualitative amounts of environmentally undesirable trace metals from the coal if such a process is developed for waste coal reclamation.
Coal reclamation, Waste dumps, Bacterial leaching, Acid mine drainage.