Abstract: Understanding the effects of chloride ions (Cl^-) on the biooxidation of pyrite is beneficial for revealing the formation mechanism of acid mine drainage (AMD). Meanwhile, uncovering the biomineralization behavior in wastewater system has implication for clarifying the regulation of AMD production by biomineralization behavior. In this study, the effects of Cl^- on the pyrite biooxidation were investigated (the liquid medium required for microorganism growth was notadded into systems). The synthetic behavior of secondary iron minerals in the wastewater system was examined through flask experiment. Results showed that there was no significant difference of pyrite biooxidation efficiency between the treatments without Cl^- addition and with 8.2 mmol·L^-1 of Cl^- addition. The biooxidation efficiency of pyrite was promoted when the initial Cl^- concentration was 16.5 mmol·L^-1. The biooxidation efficiency of pyrite was significantly inhibited when the initial Cl^- concentration reached 49.4-65.8 mmol·L^-1. For example, the total Fe concentrations were 1204.56, 1218.09, 1431.50 and 796.48 mg·L^-1 at day 68 when the initial concentrations of Cl^- were 0, 8.2, 16.5, and 65.8 mmol·L^-1, respectively. There were obvious microbial erosion pits on the surface of biooxidized pyrite in all treatments. However, no secondary iron minerals were observed on the surface of biooxidized pyrite. After the pyrite biological oxidation in different treatments, 54.3%-79.5% of total Fe ions mainly presented as Fe²⁺ type. The filtrate obtained by filtering in different treatments was cultured and the systems eventually produced secondary iron minerals (such as jarosite) when Fe²⁺ was gradually oxidized completely. Thus, Cl^- concentrations played a role in regulating biological oxidation of pyrite. When the Fe ions are separated from the pyrite system and Fe²⁺ gradually are oxidized to Fe³⁺, a large amount of secondary iron minerals can be synthesized in systems. Our results provide theoretical support for clarifying the formation of AMD and the synthesis of secondary iron minerals in the AMD system.

Key words: large jellyfish, podocyst production., strobilation, budding