Oxidative Degradation of Organic Compounds Using Zero-Valent Iron in the Presence of Natural Organic Matter Serving as an Electron Shuttle

School of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea.
Environmental Science and Technology (Impact Factor: 5.48). 03/2009; 43(3):878-83. DOI: 10.1021/es801705f
Source: PubMed

ABSTRACT This study aims to understand the oxidative degradation of organic compounds utilizing zerovalent iron (ZVI) which is further promoted by the presence of natural organic matters (NOMs) (as humic acid (HA) or fulvic acid (FA)) working as electron shuttle mediators. The main target substrate used was 4-chlorophenol. Both HA and FA can mediate the electron transfer from the ZVI surface to O2, while enhancing the production of Fe2+ and H2O2 that subsequently initiates the OH radical-mediated oxidation of organic compoundsthrough Fenton reaction. The electron transfer-mediating role of NOMs was supported by the observation that higher concentrations of H2O2 and ferrous ion were generated in the presence of NOM. The NOM-induced enhancement in oxidation was observed with NOM concentrations ranging 0.1-10 ppm. Since the reactive sites responsible for the electron transfer action are likely to be the quinone moieties of NOMs, benzoquinone that was tested as a proxy of NOM also enhanced the oxidative degradation of 4-chlorophenol in the ZVI suspension. The NOM-mediated oxidation reaction on ZVI was completely inhibited in the presence of methanol, an OH radical scavenger, and in the absence of dissolved oxygen.

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Available from: Wonyong Choi, Feb 01, 2015
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    • "In this " ocean " of iron oxides, Fe II and H/H 2 are more or less abundant and may act as reducing agents (chemical reaction). Evidently, the papers cited [21] [22] [30] [31] [32] [33] [34] are not clear enough in their explanation to convince many authors of current publications dealing with contaminant removal in Fe 0 /H 2 O systems [35] [36] [37]. Moreover, despite the generalized access to modern scientific search engines (e.g. "
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    ABSTRACT: The interpretation of processes yielding aqueous con-taminant removal in the presence of elemental iron (e.g. Fe0/H2O systems) is subject to numerous complications. A conventional Fe0/H2O system is basically a galvanic cell in which the essential feature is the absence of any external electric current. Fe0 is the anode of this galvanic cell. Fe0 oxidative dissolution induces contaminant removal by several physical processes (e.g. adsorption, enmeshment) as well-documented in internal electrolysis. Recent pro-gresses considering adsorption, co-precipitation and size-exclusion as fundamental contaminant removal mecha-nisms in Fe0/H2O systems have faced a certain skepti-cism. The present communication shows that results from internal electrolysis (IE) using iron as anode and carbon as cathode corroborate the adsorption/co-precipitation concept. It is reiterated that experimental designs using external electrolysis (e.g. voltametric experiments) are not suitable for the investigation of processes in passive remediation Fe0/H2O systems.
    Fresenius Environmental Bulletin 09/2014; 23(10). · 0.53 Impact Factor
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    • "The versatility of nanoscale zerovalent iron (nZVI) has been regarded as one of the most promising permeable barrier materials used for the in-situ remediation of wastewater in environmental engineering due to its large surface area, extremely small particle size and high in-situ reactivity [6]. Therefore, more attentions have extensively focused on NZVI for the rapid removal of organic contaminants [7] [8] [9] [10] [11] [12] and variant valence metals such as chromium [13] [14] [15] [16], arsenic [17] [18] [19] [20] [21], selenium [22] [23] [24] [25], technetium [26] [27] [28] [29], and uranium [30] [31] [32] [33] [34] [35]. It is demonstrated that these metals with high valence can be reduced to low valence metals by Fe 2+ ions, then these metals can also be removed by iron corrosion products [36] [37] [38]. "
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    ABSTRACT: The reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were synthesized by chemical deposition method and were characterized by SEM, high resolution TEM, Raman and potentiometric acid-base titrations. The characteristic results showed that the nZVI nanoparticles can be uniformly dispersed on the surface of rGO. The removal of U(VI) on nZVI/rGO composites as a function of contact time, pH and U(VI) initial concentration was investigated by batch technique. The removal kinetics of U(VI) on nZVI and nZVI/rGO were well simulated by a pseudo-first-order kinetic model and pseudo-second-order kinetic model, respectively. The presence of rGO on nZVI nanoparticles increased the reaction rate and removal capacity of U(VI) significantly, which was attributed to the chemisorbed OH(-) groups of rGO and the massive enrichment of Fe(2+) on rGO surface by XPS analysis. The XRD analysis revealed that the presence of rGO retarded the transformation of iron corrosion products from magnetite/maghemite to lepidocrocite. According to the fitting of EXAFS spectra, the UC (at ∼2.9Å) and UFe (at ∼3.2Å) shells were observed, indicating the formation of inner-sphere surface complexes on nZVI/rGO composites. Therefore, the nZVI/rGO composites can be suitable as efficient materials for the in-situ remediation of uranium-contaminated groundwater in the environmental pollution management.
    Journal of Hazardous Materials 09/2014; 280:399–408. DOI:10.1016/j.jhazmat.2014.08.023 · 4.33 Impact Factor
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    • "In a similar way, HA and FA, by serving as an electron shuttle, enhanced the degradation rate of organic compounds, relating to the role of quinone unit [14]. Kang and Choi [14] reported that both HA and FA can mediate the electron transfer from the zerovalent iron surface to O 2 , while enhancing the production of Fe 2+ and H 2 O 2 that subsequently initiates the "
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    ABSTRACT: Polyhydroquinone, an immobilized quinone, was synthesized by oxidative polymerization of hydroquinone. The polymers obtained were characterized by Fourier-transform infrared spectra and cyclic voltammetry. Polyhydroquinone is a redox-active polymer with quinone/hydroquinone redox active units in the main chain. The influence of polyhydroquinone in the Fe3O4/persulfate system was examined. It was found that the addition of polyhydroquinone in Fe3O4/persulfate system increased the oxidation rate of Rhodamine B (RhB), which was ascribed to their role as an electron shuttle. The presence of polyhydroquinone successfully builds up two cycles, one semiquinone/quinone cycle, another cycle of Fe(III)/Fe(II) induced by quinone. The presence of phenolic and quinonoid moieties in the structure of polyhydroquinone provide for their ability to reduce Fe(III), thereby assisting the redox cycling of Fe and increasing degradation of the target substrate.
    Chemical Engineering Journal 03/2014; 240:338–343. DOI:10.1016/j.cej.2013.11.090 · 4.32 Impact Factor
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