Dramatically Enhanced Aerobic Atrazine Degradation with Fe@Fe₂O₃ Core–Shell Nanowires by Tetrapolyphosphate

Abstract

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.

Oxidation of organic contaminants in water by iron-induced oxygen activation: A short review

“…The addition of TPP accelerated the degradation of organic target compounds such as atrazine and pentachlorophenol [39,40] as well as significantly increasing the oxidant yields for both the nZVI/O2 and the Fe(II)/O2 systems (unpublished Results) ( Table 1). The primary role of TPP is the formation of soluble complexes by iron-chelation that prevents the precipitation of iron at neutral pH.…”

“…Recently, tetrapolyphosphate (TPP) has been suggested as a stable inorganic ligand resistant to oxidation [39,40]. The addition of TPP accelerated the degradation of organic target compounds such as atrazine and pentachlorophenol [39,40] as well as significantly increasing the oxidant yields for both the nZVI/O2 and the Fe(II)/O2 systems (unpublished Results) ( Table 1).…”

“…The primary role of TPP is the formation of soluble complexes by iron-chelation that prevents the precipitation of iron at neutral pH. However, TPP was also suggested to improve the electron availability of ZVI by promoting electron transfer from the ZVI core to Fe(III)-TPP (both surface-bound and soluble species) and subsequently regenerates Fe(III)-TPP into Fe(II)-TPP [40].…”

“…Several investigators have demonstrated the degradation of organic contaminants such as phenolic compounds, herbicides, pharmaceuticals and diagnostic agents, and dyes by the ZVI/O2 and the Fe(II)/O2 systems with or without additives [13,39,40,[45][46][47][48][49][50]. Table 2 summarizes those literature results reported in terms of the type of iron, the target compound, initial concentrations, conditions, and degradation efficiency.…”

Enrofloxacin Transformation on Shewanella oneidensis MR-1 Reduced Goethite during Anaerobic–Aerobic Transition

“…11 It has been reported in recent studies that several synthetic mixed-valence iron oxides, such as Fe@Fe 2 O 3 nanowires, could activate the dissolved molecular oxygen by electron transfer to generate reactive oxygen species (ROS), which can be used for the oxidative degradation of organic contaminants. 17,18 Considering the ubiquitous distribution of iron oxides and DIRB, we hypothesize that the surface process involving DIRB-mediated Fe(III) reduction followed by aerobic Fe(II) oxidation is an important natural pathway for the biotransformation of antibiotics.…”