Treatment of chemical warfare agents by zero-valent iron nanoparticles and ferrate(VI)/(III) composite

Highlights: ► Ferrate(VI) has been found to be highly efficient to decontaminate chemical warfare agents. ► Fast degradation of sulfur mustard, soman and compound VX by ferrate(VI). ► Nanoscale zero-valent iron particles are considerably less efficient in degradation of studied warfare agents compared to ferrate(VI). - Abstract: Nanoscale zero-valent iron (nZVI) particles and a composite containing a mixture of ferrate(VI) and ferrate(III) were prepared by thermal procedures. The phase compositions, valence states of iron, and particle sizes of iron-bearing compounds were determined by combination of X-ray powder diffraction, Mössbauer spectroscopy and scanning electron microscopy. The applicability of these environmentally friendly iron based materials in treatment of chemical warfare agents (CWAs) has been tested with three representative compounds, sulfur mustard (bis(2-chlorethyl) sulfide, HD), soman ((3,3′-imethylbutan-2-yl)-methylphosphonofluoridate, GD), and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX). Zero-valent iron, even in the nanodimensional state, had a sluggish reactivity with CWAs, which was also observed in low degrees of CWAs degradation. On the contrary, ferrate(VI)/(III) composite exhibited a high reactivity and complete degradations of CWAs were accomplished. Under the studied conditions, the estimated first-order rate constants (∼10−2 s−1) with the ferrate(VI)/(III) composite were several orders of magnitude higher than those of spontaneous hydrolysis of CWAs (10−8–10−6 s−1). The results demonstrated that the oxidative technology based on application of ferrate(VI) is very promising to decontaminate CWAs.