Dramatically enhanced aerobic atrazine degradation with Fe@Fe2O3 core-shell nanowires by tetrapolyphosphate

In this study, the effects of an inorganic ligand tetrapolyphosphate on the molecular oxygen activation and the subsequent aerobic atrazine degradation by Fe@Fe2O3 core-shell nanowires were investigated systematically at a circumneutral to alkaline pH range (pH 6.0-9.0). We interestingly found that the addition of tetrapolyphosphate could enhance the aerobic atrazine degradation rate 955 times, which was even 10 times that of the traditional organic ligand ethylenediamine tetraacetate. This tetrapolyphosphate induced dramatic aerobic atrazine degradation enhancement could be attributed to two factors. One was that the presence of tetrapolyphosphate strongly suppressed hydrogen evolution from the reduction of proton by Fe@Fe2O3 core-shell nanowires through proton confinement, leaving over more electrons for the reduction of Fe(III) to Fe(II) and the subsequent molecular oxygen activation. The other was that the complexation of tetrapolyphosphate with ferrous ions not only guaranteed enough soluble Fe(II) for Fenton reaction, but also provided another route to produce more •OH in the solution via the single-electron molecular oxygen reduction pathway. We employed gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry to identify the atrazine degradation intermediates and proposed a possible aerobic atrazine degradation pathway. This study not only sheds light on the promotion effects of ligands on the molecular oxygen activation by nanoscale zerovalent iron, but also offers a facile and green iron-based method for the oxidative atrazine removal.