Spectroscopic study on biological mackinawite (FeS) synthesized by ferric reducing bacteria (FRB) and sulfate reducing bacteria (SRB): Implications for in-situ remediation of acid mine drainage.

Mackinawite (FeS), widespread in low temperature aquatic environments, is generally considered to be the first Fe sulfide formed in sedimentary environments which has shown effective immobilization of heavy metals and toxic oxyanions through various sorption reactions. The spectroscopic study researches on mackinawite formed by FRB and SRB and its environmental implication for in-situ remediation of acid mine drainage where contains large amounts of Fe3+ and SO4 2- . The XRD result of biologically synthetic particles shows that these particles are mainly composed of mackinawite (FeS0.9 ). The Raman peaks observed at 208, 256, 282, 298cm-1 are attributed to FeS stretching vibrations of mackinawite. The Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR) reveals that the diagnostic bands of low intensity for these FeS particles occur at 412-425cm-1 and 607-622cm-1 , which are assigned to the stretching vibrations of SS and FeS bonds. The Raman and IR vibrations from organic components both confirm that these particles are biogenic origin. The IR spectra of biologically synthesized mackinawite for different aging times show that the nano-sized particles mackinwate will be completely oxidized within 10h. All these findings have good implications for in-situ remediation of acid mine drainage.