es9b03214_si_001.pdf (575.37 kB)
Water Flow Variability Affects Adsorption and Oxidation of Ciprofloxacin onto Hematite
journal contribution
posted on 2019-08-23, 15:03 authored by Lian Zhou, Sébastien Martin, Wei Cheng, Laurent Lassabatere, Jean-François Boily, Khalil HannaThe
mobility of pharmaceuticals in environmental systems is under
great scrutiny in the scientific literature and in the press. Still,
very few reports have focused on redox-driven transformations when
these compounds are bound to mineral surfaces, and how their transport
is affected under flow-through conditions. In this study, we examined
the adsorption and electron transfer reactions of ciprofloxacin (CIP)
in a dynamic column containing nanosized hematite (α-Fe2O3). CIP binding and the subsequent redox transformation
were strongly dependent on inflow pH and residence time. These reactions
could be predicted using transport models that account for adsorption
and transformation kinetics. Our results show that flow interruption
over a 16 h period triggers oxidation of hematite-bound CIP into byproducts.
These reactions are likely facilitated by inner-sphere iron–CIP
complexes formed via the sluggish conversion from outer-sphere complexes
during interrupted flow. When intermittent flow/no-flow conditions
were applied sequentially, a second byproduct was detected in the
column effluent. This work sheds light on a much overseen aspect of
redox transformations of antibiotics under flow-through conditions.
It has important implications in adequately predicting transport,
and in developing risk assessments of these emerging compounds in
the environment.