Reactive oxidative species generation in pyrite abiotic-oxidation process: Origins, influencing factors, applications for environmental remediation

Pyrite is the most common sulfur-bearing iron mineral in Earth surface environments. Pyrite is extensively utilized as a catalyst in the advanced oxidation processes (AOPs) for wastewater treatment due to its impressive reductive capacity and high Fe(II) content. However, it is still controversial whether pyrite could play a truly favorable role in the decontamination processes, as most of the pyrite-based AOPs are susceptible to water matrices and prone to deactivation during reactions. Elucidating mechanisms of the pyrite-mediated reactive oxygen species (ROS) generation is crucial for addressing the aforementioned question, but this topic has rarely been systematically summarized so far. In this Critical Review, we first elaborate on the fundamental mechanisms of the pyrite-mediated ROS generation in anoxic/aerobic environments. Afterward, detailed discussions are presented on how the intrinsic nature of pyrite, the secondary iron/sulfur species formed during the oxidation processes, and the conventional water chemistry parameters influence the pyrite-mediated ROS generation process. Furthermore, we summarize the enhancing mechanisms of the recently developed pyrite-based AOPs. Especially, the research focus and experimental design are compared between studies targeting the geo-environmental processes and the environmental engineering systems, since some overlooked but important mechanisms should be mutually informative across different disciplines to advance the comprehension of the environmental behavior of pyrite. Finally, the perspectives and proposals are briefly outlined to stimulate future discussion and interest in developing more rational pyrite-based environmental remediation technologies.