A dramatically improved degradation efficiency of azo dyes by zero valent iron powders decorated with in-situ grown nanoscale Fe2B

Abstract Zero valent iron (ZVI) is widely used in azo dye degradation due to the low cost and no secondary pollution. However, its low efficiency limits its wide application. In this paper, nanometer Fe2B particles with more negative open circuit potential and reductivity than Fe were in-situ decorated on the surface of low-cost construction-grade granular iron powders through sintering and improved degradation efficiency was obtained. Fe–Fe2B powders with 17 at% boron content can obtain 29 times decolorization ratio higher than unmodified Fe. The degradation efficiency continuously increases with Fe2B amount until a compact Fe2B coating formed and isolated inner Fe from the pollutant. Fe2B and Fe form galvanic cells to promote the electron transfer and reduction reaction. The compact Fe2B coating can be destroyed during the degradation process and the catalysts with compact Fe2B coating can also obtain a similar final decolorization ratio as other samples in spite of their low initial decolorization ratio. It is the amount, not the morphology of Fe2B plays the key role for the final decolorization reaction. A good catalytic activity when applied as Fenton reagent was also confirmed and a decolorization ratio of about 90% in 30 min was obtained for these new designed catalysts.