Alumina inhibits pyrite oxidative dissolution by regulating solid film passivation layer and S, Fe, and Al speciation...

The oxidation of pyrite results in the formation of a solid film passivation layer on its surface. This layer effectively hinders the direct interaction between H₂O, O₂, and the pyrite surface, thereby impeding the oxidation dissolution of pyrite. There are few studies on whether alumina (Al₂O₃), a common aluminum-containing oxide, affects the formation of a solid film passivation layer on the surface of pyrite and inhibits the oxidation dissolution of pyrite. This research investigates the impact of Al₂O₃ incorporation on the speciation transformation of S, Fe, and Al on the surface of pyrite during oxygen pyrite process. The oxidation of pyrite followed the "polysulfide-thiosulfate" complex oxidation pathway. When <1.5 g/L Al₂O₃ was introduced, it increase pyrite oxidation, whereas ≥1.5 g/L Al₂O₃ prevented pyrite oxidation. The process of Al₂O₃ dissolution results in the consumption of H⁺ and the subsequent release of Al³⁺. This, in turn, facilitates the hydrolysis of Fe³⁺ and Al³⁺ to generate a secondary mineral layer on the pyrite surface. As a result of the accumulation of S promotes the formation of polysulfide chemical (FeS_n) or iron deficiency sulfide (Fe_1-xS), resulting in the formation of a solid film passivation layer composed of sulfur film and secondary mineral layer. The results demonstrated that Al₂O₃ can promote the formation of a solid film passivation layer on the surface of pyrite, which has significant implications for controlling the oxidation dissolution process of pyrite and offers a new perspective for the source control of acid mine drainage.