Sulfide mineral oxidation in freshly processed tailings from Boliden
Proceedings of Securing the Future International Conference on Mining and the Environment June 25 – July 1 2001 Skellefteå Sweden
This work focuses on sulfide mineral oxidation under oxic conditions in freshly processed pyrite-rich tailings from the tailings mill in Boliden, northern Sweden. Freshly processed tailings are chemically treated to kill bacteria and to obtain raised metal yields, resulting in a high pH level of 10-12 when discharged from the plant. Different batch experiments (abiotic oxidation by dissolved oxygen in untreated tailings, acid abiotic oxidation by dissolved oxygen and acid microbial oxidation), containing the Boliden tailings, were performed at room temperature under oxic conditions (0.21 atm O2) for three months. The results showed that microbial oxidation of pyrite (1.9 x 10-10 mol m-2 s-1) was 4.4 times more rapid than acid abiotic oxidation (4.3 x 10-11 mol m2 s-1) and 7.3 times more rapid than oxidation in untreated tailings (2.6 x 10-11 mol m-2 s-1).