The catalytic oxidation of Fe2+ by Acidithiobacillus ferrooxidan (A. ferrooxidans) and the synthesis of
iron sulfate-based secondary minerals is considered to be of great significance to the treatment of
acid mine drainage (AMD). Along these lines, in this work, the shaker experiment was carried out to study the underlying mechanism of the inoculation amount of
fulvic acid (FA) and A. ferrooxidans on the synthesis process of secondary minerals. From the acquired results, it was demonstrated that the oxidation rate of Fe2+ increased with the increase in the concentration of
fulvic acid in the range of 0.1-0.2 g/L. On top of that, the concentration of
fulvic acid in the range of 0.3-0.5 g/L inhibited the activity of A. ferrooxidans. However, A. ferrooxidans retained its activity, and the complete oxidation time of Fe2+ was delayed. When the concentration of
fulvic acid was 0.3 g/L, the
TFe (total
iron) precipitation efficiency was 30.2%. Interestingly, when 0.2 g/L
fulvic acid was added to different inoculum systems, the incorporation of a higher inoculum amount of A. ferrooxidans led to an increased oxidation rate. On the contrary, the lower inoculum amount yielded a more obvious effect of the
fulvic acid. From the mineralogical characteristics, it was also revealed that a
fulvic acid concentration of 0.2 g/L and different inoculation amounts of A. ferrooxidans did not change the
mineral facies, whereas pure
schwertmannite was obtained.