Synthesis mechanisms, property characterization, and environmental applications of biogenic FeS: A review.

Iron sulfide (FeS) exhibits superior reactivity toward a wide range of contaminants, making it a promising candidate for environmental remediation in various media, including surface water, wastewater, soil, and groundwater. Driven by green and sustainable development principles, efficient, low-cost, and environmentally friendly biosynthesis has attracted considerable attention and has great environmental remediation potential. This review provides a comprehensive overview of the recent advances in biogenic FeS (bio-FeS), focusing on its synthesis mechanisms, performance characterization, and environmental applications. To the best of our knowledge, this is the first review exclusively dedicated to this emerging field. This review begins with an in-depth description of the four bio-FeS biosynthetic pathways, the primary actors of which are sulfate-reducing bacteria (SRB), iron-reducing bacteria (IRB), coupled SRB and IRB, and bio-extracts. Notably, SRB account for approximately half of the bio-FeS synthesis. Various characterization techniques, including scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis, have been discussed in depth to better understand the structure and properties of bio-FeS. In terms of morphological structure, the bio-FeS synthesized by SRB exhibited primarily flakes (similar to mackinawite), whereas the bio-FeS synthesized by IRB was chiefly spherical. Bio-FeS transportation, migration, and permeation properties were also explored. Furthermore, bio-FeS application in the removal of various contaminants, including arsenic, chromium, uranium, complex pollutants, rare earth elements, chlorinated hydrocarbons, and antibiotics, and their underlying mechanisms were discussed. Finally, the challenges and future research directions related to bio-FeS environmental applications were discussed. This review aims to provide valuable insights into bio-FeS synthesis and environmental applications, thereby supporting the development of innovative and sustainable technologies for environmental remediation.