es9b07012_si_001.pdf (1.42 MB)
Oxidative Degradation of Organic Contaminants by FeS in the Presence of O2
journal contribution
posted on 2020-03-12, 18:34 authored by Dong Cheng, Anke Neumann, Songhu Yuan, Wenjuan Liao, Ao QianReductive
transformation of organic contaminants by FeS in anoxic
environments has been documented previously, whereas the transformation
in oxic environments remains poorly understood. Here we show that
phenol can be efficiently oxidized in oxic FeS suspension at circumneutral
pH value. We found that hydroxyl radicals (•OH) were the predominant
reactive oxidant and that a higher O2 content accelerated
phenol degradation. Phenol oxidation depended on •OH production
and utilization efficiency, i.e., phenol degraded per •OH produced.
Low FeS contents (≤1 g/L) produced less •OH but higher
utilization efficiency, while high contents produced more •OH
but lower utilization efficiency. Consequently, the most favorable
conditions for phenol oxidation occurred during the long-term interaction
between dissolved O2 and low levels of FeS (i.e., ≤1
g/L). Mössbauer spectroscopy suggests that FeS oxidation to
lepidocrocite initially produced an intermediate Fe(II) phase that
could be explained by the apparent preferential oxidation of structural
S(−II) relative to Fe(II), rendering a higher initial •OH
yield upon unit of Fe(II) oxidation. Trichloroethylene can be also
oxidized under similar conditions. Our results demonstrate that oxidative
degradation of organic contaminants during the oxygenation of FeS
can be a significant but currently underestimated pathway in both
natural and engineered systems.