Changes in texture and retorting yield in oil shale during its bioleaching by Bacillus Mucilaginosus

Abstract

Bioleaching of oil shale by Bacillus mucilaginosus was carried out in a reaction column for 13 d. The pH value of the leaching liquor decreased steadily from 7.5 to 5.5 and the free silicon dioxide concentration reached approximately 200 mg/L in it. Scanning electron microscopy(SEM) observations revealed that a mass of small particles separated from the matrix of oil shale. Energy dispersive spectrometry(EDS) analysis implied that the total content of Si,O, Al was decreased in the particle area of the matrix. These facts indicate that the silicate was removed, leading to the structural transformation of oil shale. Comparison of the shale oil yields before and after bioleaching illustrated that approximately 10% extra shale oil was obtained. This finding suggests that the demineralisation of the oil shale by silicate bacteria improves shale oil yield.