Fe2O3 nanorods on carbon nanofibers induce spontaneous reductive transformation of inorganic contaminants in ambient aerated water

This work reports an unconventional example that Fe2O3 nanorods loaded on carbon nanofiber sheet (Fe2O3/ CNF) enable the spontaneous reductive transformation of recalcitrant inorganic contaminants (e.g., CrO42-, Fe (CN)63-, IO3-, HSO5-, ClO3-, BrO3-, Ag+, and Pt4+) in ambient aerated solutions without using any external energy and chemicals. Fe2O3/CNF exhibited notable reductive activities for a variety of inorganic ions and transition metal ions (13 inorganic substances) which could be spontaneously reduced whereas Fe2O3 or CNF alone did not induce any conversion. The quantitative conversions to reduced products on Fe2O3/CNF were demonstrated for the cases of Fe(CN)63-, IO3-, ClO3-, and BrO3-. The reductive transformation was further confirmed by measuring the cathodic current generation on Fe2O3/CNF electrode upon spiking the target inorganic species. The spontaneous reductive processes were little hindered by the presence of dissolved O2, which makes the application practically viable as it does not require an energy-consuming deaeration process. The surface characterizations suggest that the spontaneous electron transfer is initiated upon introducing reducible inorganic substrates which electrons are transferred from the oxygen-containing functional groups on CNF to the inorganic substrates through Fe2O3 nanorods. The Fe2O3/CNF nanocomposite that reductively removes various inorganic substrates is proposed as a novel reactive nanomaterial that can control low-level contaminants.