BACTERIAL LEACHING OF 2 SWEDISH ZINC-SULFIDE ORES

Two Swedish zinc sulfide ores, from Saxberget (S-ore) and Kristineberg (K-ore), respectively, were compared for bacterial leachability with respect to grain size, and additions of ammonia, iron and phosphate. 87 days of column leaching resulted in 2.4-3.2 g Zn/l in solution and 1.5-1.9 g Cu/l from the K-ore and 1.2-5.3 g Zn/l and 0-0.3 g Cu/l from the S-ore. The highest values were achieved for grain sizes between 16 and 64 mm. Ammonium showed a stimulating effect on bacterial leaching, increasing leached Zn in the K-ore from 27% to 35% and from 7% up to 70% Zn in the S-ore after 53 days of batch leaching. Phosphate additions showed negative effects. Iron additions had a positive effect for the K-ore, increasing the leaching from 48% to 78% Zn at an addition of 6 mg Fe2+.