Bio-oxidation behavior of pyrite, marcasite, pyrrhotite, and arsenopyrite by sulfur- and iron-oxidizing acidophiles

The oxidation of sulfide minerals is of central importance due to the acid mine drainage (AMD) production. The bio-oxidation of pyrrhotite, pyrite, marcasite, and arsenopyrite was carried out with mesophilic bacteria ( Acidithiobacillus ferrooxidans , A. thiooxidans , and Leptospirillum ferrooxidans ) at 34 °C for 30 days. Bio-oxidation tests showed that marcasite has a high potential in producing AMD compared to pyrrhotite. Arsenopyrite has different behavior in the presence and the absence of additives (i.e., FeSO 4 ·7H 2 O and sulfur). While the absence of additives increased the nickel and zinc dissolution, their presence increased the total iron dissolution. Sulfur and jarosite were observed on the surfaces of pyrrhotite and arsenopyrite. With the formation of these passivation layers, the continuous iron extraction is effectively suppressed. This study is helpful to comparatively evaluate the AMD production of sulfide minerals in an oxidizing environment and to study the effects of passivation layers on their biooxidation in different conditions. • Bio-oxidation of pyrite, marcasite, pyrrhotite and arsenopyrite was studied. • Sulfide minerals show different bio-oxidation behavior in different conditions. • Marcasite has a high potential in producing acid mine drainage compared to pyrrhotite. • Sulfur and jarosite formed passivation layers during bio-oxidation process.