Enhanced reductive degradation of carbon tetrachloride by biogenic vivianite and Fe(II)

We demonstrated that reductive dechlorination of carbon tetrachloride (CT) can be enhanced by iron-bearing soil minerals (IBSMs) in the presence of Shewanella putrefaciens CN32 (CN32) due to the formation of biogenic vivianite and Fe(II). The bioreduction efficiency of magnetite was the highest (51.1%), followed by lepidocrocite (25.7%), goethite (3.6%), and hematite (1.8%). The dechlorination kinetic of CT by lepidocrocite (0.043 d−1) in the presence of CN32 was three times faster than that by microbial transformation with CN32 (0.014 d−1). Chloroform (16.1–29.4%), carbon monoxide (2.4–23.8%), and formate (0–58.0%) were measured as main products for the degradation of CT by magnetite and lepidocrocite in the presence of CN32. X-ray diffraction and electron microscope analyses revealed that the biogenic vivianite can form during the CT degradation in magnetite and lepidocrocite suspensions with CN32. The dechlorination kinetics of CT by chemogenic vivianite was much faster than that by magnetite and lepidocrocite with CN32. The highest formate production (84.2%) was observed during a full degradation of CT by the chemogenic vivianite. The experimental results showed that biogenic vivianite and sorbed Fe(II) formed during the bioreduction of IBSMs played a pivotal role for the reductive dechlorination of CT.