Regulation mechanism and kinetic characteristics of pyrite oxidation mediated by aluminum-bearing minerals

• Optimal inhibitory concentration (Al 2 O 3 : 20mmol/L; clay: 30mmol/L) • The inhibitory effect of clay is better than that of Al 2 O 3 (with the same Al 3+ equivalent). • The oxidation kinetics of pyrite conforms to the solid film shrinkage nucleation kinetics model. As the most prevalent metal sulfide mineral in mining environments, pyrite readily undergoes oxidation under surface conditions to generate acid mine drainage, resulting in a series of environmental pollution issues. During pyrite oxidation, a solid passivation film forms on its surface, which impedes the diffusion and mass transfer of water and oxygen, thereby inhibiting further pyrite oxidation and dissolution. The dissolution of Al-bearing minerals that coexist or are associated with pyrite leads to the release of Al 3+ , producing high-aluminum acid mine water. However, the surface oxidation mechanism of pyrite and the kinetic effects induced by Al-bearing minerals remain poorly documented. This study utilized A.ferroxidans bacteria to systematically explore the mechanism of Al 2 O 3 and native alumina clay on the oxidation process of pyrite through experimental simulation and kinetic analysis, providing key scientific basis and new directions for the development of low-cost source control technology for acidic mine water. The results indicated that the addition of Al 2 O 3 and clay increased the pH of the reaction system, thereby inhibiting the activity of A.ferrooxidans . This promoted the hydrolysis of Fe 3+ and Al 3+ to form secondary minerals, which deposited as a passive solid film on the pyrite surface and consequently suppressed the oxidation and dissolution of pyrite. The oxidation rate of pyrite was significantly affected by the equivalent concentration of Al 3+ , with an obvious critical threshold. In the Al 2 O 3 system, significant inhibition was achieved at an Al 3+ equivalent concentration of 20 mmol/L, with a pyrite oxidation rate of 19.68%. In the clay system, notable inhibition occurred at an Al 3+ equivalent concentration of 30 mmol/L, yielding a pyrite oxidation rate of 3.10%. The oxidation and dissolution of pyrite followed the solid film shrinkage kinetic model, with correlation coefficients R 2 all above 0.85. Both Al 2 O 3 and clay facilitated the formation of a solid film on the pyrite surface. Under the same Al 3+ dosage, clay was more favorable for the formation of a solid film on pyrite than Al 2 O 3 .