Effect of adding surfactant in the leaching solution on the growth and activity of microorganisms in a heap bioleaching system

摘要

The presence of surfactants in the lixiviant solution has the potential to improve solution penetration into the small pores and cracks of large ore particles by decreasing surface tension, thereby enhancing access of lixiviant to internal mineral grains and associated metal recovery from low grade sulphide ores. The influence of surfactant on the growth and activity of microorganisms implicated in bioleaching must also be considered, because they are required for the regeneration of leach reagents and control of the leaching reaction products. The effect of surfactant addition on ferrous iron oxidation and microbially-mediated leaching of chalcopyrite by a mixed thermophilic microbial culture was investigated using five non-ionic surfactants: Tween~R 20, Tween~R 80, Plurafac~R LF 120, Plurafac~R LF 600, and Lutensol~R XL 90 at concentrations of 5, 10 and 20 mg/L. The addition of 5 and 10 mg/L Tween~R 20 showed no negative effect on microbial ferrous iron oxidation and chalcopyrite bioleaching. Further, its presence was observed to reduce the initial leaching lag time. Microbial ferrous iron oxidation was inhibited in the presence of 10 mg/L Plurafac~R LF 120 while there was partial inhibition in the system containing 10 mg/L Lutensol~R XL 90. Plurafac~R LF 600 at 5 and 10 mg/L and Tween~R 80 at 10 mg/L inhibited microbial growth completely, and thereby leaching.