Many oxyanion-forming metals (As, Sb, Se, Tc, etc.) can be removed from water by adsorption and/or redox reactions involving iron oxides, including the oxides associated with zerovalent iron (ZVI). The rate of antimonite (Sb(III) hydrolysis species) removal by ZVI was determined in open, well-mixed batch reactors as a function of experimental factors including aging of the ZVI, addition of Fe(II), Sb dose, mixing rate, pH, initial concentrations of Sb(III), etc. However, the largest effect observed was the roughly 7-fold increase in Sb(III) removal rate due to the application of a weak magnetic field (WMF) during the experiments. The WMF effect on Sb removal arises from stimulated corrosion and delayed passivation of the ZVI, as evidenced by trends and correlations in “geochemical” properties (DO, total Fe, Eh, and pH) measured synchronously in each experiment. The removal of Sb under the conditions of this study involved oxidation of Sb(III) to Sb(V) and adsorption onto the iron oxides formed from accelerated corrosion of ZVI, as evidenced by Sb K-edge XANES, EXAFS, and XPS. The degree of the WMF enhancement observed in this study for Sb(III) was compared to previously reported data on the WMF with Sb(V), As(III), As(V), and Se(VI). The ratio of rates constants with and without WMF was almost always in the range of 2-8, with only a few cases with significantly larger effects that appear to be anomalous.

Sequestration of antimonite by zerovalent iron: Using weak magnetic field effects to enhance performance and characterize reaction mechanisms

251st National Meeting (2016)

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