Quan Sun

University of New South Wales, Kensington, New South Wales, Australia

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Publications (2)5.25 Total impact

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    ABSTRACT: The oxidation of organic compounds in oxygen saturated aqueous suspensions of nanoparticulate zero valent iron (nZVI) is rapidly becoming an area of important consideration for environmental scientists and engineers. Through the production of reactive oxygen species, oxidative processes do occur but have been shown to be of limited efficiency. To increase efficiency for this process, the addition of electron shuttling molecules have been shown to enhance the oxidative capacity of nZVI. Laboratory experiments were conducted at pH 3.0 over a range of nZVI starting concentrations, and the reaction was monitored by following the oxidation of HCOOH and the production of H(2)O(2) with time. These studies confirm that the addition of the polyoxometallates (POM), sodium polyoxotungstate (Na(3)PW(12)O(40)), enhances the oxidative capacity of nZVI. Based on these results, the mechanism for the enhancement in oxidative capacity of nZVI is through two separate processes: (1) the POM out-competes H(2)O(2) for electrons from Fe(0) thereby increasing the H(2)O(2) concentration, and (2) the reduced form of the POM, PW(12)O(40)(-4), facilitates the cycling of Fe(III) to Fe(II) which enhances the homogeneous Fenton reaction.
    Chemosphere 09/2010; 81(1):127-31. · 3.14 Impact Factor
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    ABSTRACT: It has recently been demonstrated that nano scale zero-valent iron (nZVI) oxidizes the herbicide molinate when it is used in the presence of oxygen. Further batch and column experiments were conducted to investigate the potential application of nZVI for the treatment of contaminants. Results of batch studies reveal a rapid initial degradation of molinate followed by slower degradation over more than a day. Additional insight into the nZVI-mediated process has been obtained from studies of the formation of para-hydroxybenzoic acid (p-HBA) from the oxidative degradation of benzoic acid with slow ongoing production of p-HBA over 24 h observed after an initial pulse of byproduct production. Addition of EDTA enhances the initial pulse by 50% but does not appear to reduce surface passivation over a longer time frame. Oxygen availability during the initial pulse appears to be a limiting factor. Results of column studies reveal that the arrangement of the nZVI, sand and gravel within the column strongly affect the degradation performance despite each column having the identical nZVI loading. Under the optimal column configuration, >90% removal of 100 ppb molinate was observed over a 3 h period. These promising results suggest that nZVI, despite initial rapid oxidation of the particle surface, has sufficient residual oxidizing power to enable it to be incorporated into a continuous treatment process.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 01/2005; 265:88-94. · 2.11 Impact Factor