Biodegradation mechanism of arsenopyrite mine tailing with Acidithiobacillus ferrooxidans and influence of ferric supplements

Microbial mobilization of arsenopyrite minerals under oxic conditions are well known; however, little is known about how the metals can be mobilized through biodegradation of mine tailings. Therefore, the role of inoculated Acidithiobacillus ferrooxidans on the mobility of arsenic and iron was examined for a sample of South Korean mine tailing. Two modes of interactions (i) direct contact, and (ii) non-contact were examined along with the monitoring of Eh-pH values and cell density. Direct contact of Acidithiobacillus ferrooxidans could mobilize metal ions more efficiently than the non-contact mode of interaction albeit revealed that the overall interaction was governed by a co-operative mechanism. A direct-contact biotic study resulted in the higher mobilization of arsenic (similar to 69%) than the non-contact biotic system (similar to 44%), but the maximum mobilization (similar to 80%) could be achieved with 6 g/L ferric supplement to the direct-contact system. The ferric-improved mobilization was higher up to seven days from the starting time, thereafter, the surface passivation [KFe3(SO4)(2)(OH)(6 )and S-0] sieged the mobilization progress. Finally, the interaction mechanism proposed in this study suggests that the storage with intact coating on tailings can limit the microbial degradation to prevent arsenic mobilization to the environment.