Perchlorate Reduction by Nanoscale Iron Particles

We report herein the near complete reduction of perchlorate (ClO \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{4}^{-}$$\end{document}) to chloride by nanoscale iron particles. The nanoparticles also reduce chlorate (ClO \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{3}^-$$\end{document}), chlorite (ClO \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{2}^-$$\end{document}) and hypochlorite (ClO \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{-}$$\end{document}) to chloride. No reaction was observed with microscale iron powder under identical conditions. The temperature sensitivity of the perchlorate-nanoparticle reaction is evidenced by progressively increasing rate constant values of 0.013, 0.10, 0.64 and 1.52 mg perchlorate per g nanoparticles per hour (mg-g-1-hr-1), respectively, at temperatures of 25, 40, 60 and 75°C. The activation energy of perchlorate-iron reaction was calculated to be 79.02 ± 7.75 kJ/mole. Despite favorable thermodynamics, the relatively large activation energy for this reaction suggests that perchlorate reduction is limited by the slow kinetics. The nanoscale iron particles may represent a potential treatment method for perchlorate-contaminated water.