Arsenic Removal from Water Using Flame-Synthesized Iron Oxide Nanoparticles with Variable Oxidation States

Abstract

We utilized gas-phase diffusion flame (DF) synthesis, which has potential for large-scale production of metal oxide nanoparticles, to produce iron oxide nanoparticles (IONPs) with variable oxidation states. The efficacy of these materials in removal of arsenate (As(V)) from water was assessed. Two different flame configurations, a DF and an inverse diffusion flame (IDF), were employed to synthesize six different IONPs by controlling flame conditions. The IONPs produced in the IDF configuration (IDF-IONPs) had smaller particle diameters (4.8–8.2 nm) and larger surface areas (141–213 m²/g) than the IONPs produced in the DF configuration (29 nm, 36 m²/g), which resulted in their higher adsorption capacities. As(V) adsorption capacities of the IDF-IONPs increased when the IONPs were synthesized in more oxidizing conditions. The fully oxidized IDF-IONPs, maghemite (γ-Fe₂O₃), showed the highest As(V) adsorption capacity, comparable to that of magnetite nanocrystals synthesized by thermal decomposition of iron pentacarbonyl and equivalent to three to four times higher capacity than that of a commonly used goethite-based adsorbent. All IONPs were magnetically responsive, which is of great importance for solid−liquid separation. This study demonstrates that the IONPs synthesized in gas-phase flame, particularly IDF-IONPs, are excellent adsorbents because of their high As(V) sorption capacity, potential for large-scale production, and useful magnetic property.

Copyright 2013 American Association for Aerosol Research

Acknowledgments

The project described was supported by Award Number P42ES004699 from the National Institute of Environmental Health Sciences. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Environmental Health Sciences or the National Institutes of Health. Contributions by M. Kanematsu to the project were supported under contract #06–55254 from the California Department of Public Health, Safe Drinking Water Revolving Fund. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Environmental Health Sciences, the National Institutes of Health, or the California Department of Public Health.

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