1 research outputs found
Assessing the Effect of Humic Acid Redox State on Organic Pollutant Sorption by Combined Electrochemical Reduction and Sorption Experiments
Natural Organic Matter (NOM) is a major sorbent for organic
pollutants
in soils and sediments. While sorption under oxic conditions has been
well investigated, possible changes in the sorption capacity of a
given NOM induced by reduction have not yet been studied. Reduction
of quinones to hydroquinones, the major redox active moieties in NOM,
increases the number of H-donor moieties and thus may affect sorption.
This work compares the sorption of four nonionic organic pollutants
of different polarities (naphthalene, acetophenone, quinoline, and
2-naphthol), and of the organocation paraquat to unreduced and electrochemically
reduced Leonardite Humic Acid (LHA). The redox states of reduced and
unreduced LHA in all sorption experiments were stable, as demonstrated
by a spectrophotometric 2,6-dichlorophenol indophenol reduction assay.
The sorption isotherms of the nonionic pollutants were highly linear,
while paraquat sorption was strongly concentration dependent. LHA
reduction did not result in significant changes in the sorption of
all tested compounds, not even of the cationic paraquat at pH 7, 9,
and 11. This work provides the first evidence that changes in NOM
redox state do not largely affect organic pollutant sorption, suggesting
that current sorption models are applicable both to unreduced and
to reduced soil and sediment NOM