Efficient catalytic As(III) oxidation on the surface of ferrihydrite in the presence of aqueous Mn(II).

摘要: Arsenic is a carcinogenic element that exists primarily as arsenate [As(V)] and arsenite [As(III)] in the nature environment, with As(III) being more toxic mobile of two species. In addition, ferrihydrite, which widely distributed soils aquatic environments, can catalyze oxidation Mn(II) accelerate formation high-valence Mn, significantly influence speciation, toxicity, mobility As when these species co-exist. this context, we herein explored mechanism presence ferrihydrite using kinetic approach combined multiple spectroscopic techniques, including X-ray absorption near edge spectroscopy, situ horizontal attenuated total-reflectance Fourier transform infrared quick scanning spectroscopy. Our results indicate efficient by dissolved O2 occurs on surface aqueous Mn(II). Compared Mn oxides (i.e., oxides/hydroxides), degree ferrihydrite-Mn(II) system was higher, majority generated As(V) adsorbed mineral ferrihydrite) surface. Furthermore, enhanced upon increasing both molar ratio Mn(II)/As(III) solution pH. The greater mainly attributed to strong oxidant instantaneous intermediate Mn(III) via under catalysis Moreover, occurred accompanied regeneration Mn(II), thereby rendering it recyclable. These therefore provide new insights into surfaces Fe oxides/hydroxides) well details regarding electron transfer mechanisms between As(III)-Mn(II, III)-O2 at surface, could lead novel approaches for contaminant remediation environment.