Particle size effects in bioleaching of pyrite by acidophilic thermophile Sulfolobus metallicus (BC)

The effect of mineral particle size on the bioleaching of pyrite by the aci dophilic thermophile Sulfolobus metallicus was investigated in a batch bior eactor. Decreasing the particle size from a mean diameter of 202 micron (si ze fraction: 150-180 micron) to a mean diameter of 42.5 micron (size fracti on: 25-45 micron) enhanced the bioleaching rate from 0.05 kg m(-3) h(-1) to 0.098 kg m(-3) h(-1). The particle size distribution of the mineral in thi s range did not influence the morphology and growth kinetics of the cells. The values of specific growth rate (mu) and yield factor (Y) were 0.018-0.0 25 h(-1) and 0.67 x 10(-11)-1.45 x 10(11) cells (g iron)(-1), respectively. Decreasing the particle size of the mineral to a mean diameter of 6.40 mic ron (size fraction <25 micron) adversely influenced the activity of the cel ls. The presence of fine particles apparently damaged the structure of the cells, resulting in their inability to oxidise pyrite.