1 research outputs found
Iron(III)-Bearing Clay Minerals Enhance Bioreduction of Nitrobenzene by <i>Shewanella putrefaciens</i> CN32
Iron-bearing clay minerals are ubiquitous
in the environment, and
the clay–FeÂ(II)/FeÂ(III) redox couple plays important roles
in abiotic reduction of several classes of environmental contaminants.
We investigated the role of Fe-bearing clay minerals on the bioreduction
of nitrobenzene. In experiments with <i>Shewanella putrefaciens</i> CN32 and excess electron donor, we found that the Fe-bearing clay
minerals montmorillonite SWy-2 and nontronite NAu-2 enhanced nitrobenzene
bioreduction. On short time scales (<50 h), nitrobenzene reduction
was primarily biologically driven, but at later time points, nitrobenzene
reduction by biologically formed structural FeÂ(II) in the clay minerals
became increasingly important. We found that chemically reduced (dithionite)
iron-bearing clay minerals reduced nitrobenzene more rapidly than
biologically reduced iron-bearing clay minerals despite the minerals
having similar structural FeÂ(II) concentrations. We also found that
chemically reduced NAu-2 reduced nitrobenzene faster as compared to
chemically reduced SWy-2. The different reactivity of SWy-2 versus
NAu-2 toward nitrobenzene was caused by different forms of structural
clay-FeÂ(II) in the clay minerals and different reduction potentials
(<i>E</i><sub>h</sub>) of the clay minerals. Because most
contaminated aquifers become reduced via biological activity, the
reactivity of biogenic clay–FeÂ(II) toward reducible contaminants
is particularly important