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Remediating chloroacetanilide -contaminated water using zerovalent iron
Pesticide spills and discharges can result in ground and surface water contamination. Simple iron treatment provides an effective and inexpensive remediation tool for soil and water contaminated with chloroacetanilide herbicides. We found the effectiveness of zerovalent iron (Fe0) to dechlorinate aqueous metolachlor (2-chloro-N-(2-ethyl-6-methyl phenyl)- N-(2-methoxy-1-methyl ethyl) acetamide) was greatly enhanced in the presence of Al, Fe(II) or Fe(III) salts, with the following order of destruction kinetics observed: Al2(SO4)3 > AlCl 3 > Fe2(SO4)3 > FeCl3. A common observation was the formation of green rusts, mixed Fe(II)/Fe(III) hydroxides with interlayer anions that impart a greenish-blue color. The mechanism responsible for enhanced metolachlor loss may be related to the role these salts play in facilitating Fe(II) release. To investigate this catalytic effect, we characterized changes in Fe0 composition during the treatment of metolachlor. Raman microscopic analysis and X-ray diffraction indicated that the iron source was initially coated with a thin layer of magnetite (Fe3O4), maghemite (γ-Fe 2O3), and wüstite (FeO). Temporal mineralogical analysis indicated akaganeite (β-FeOOH), goethite (α-FeOOH), magnetite, and lepidocrocite (γ-FeOOH) formed in the Fe0-metolachlor suspension when Al2(SO4)3 or FeSO4 were present. Green rust II (Fe6(OH)12SO4) was also transiently identified in Fe0 treatments containing FeSO4. Although conditions favoring green rust formation in a Fe 0-batch system increased metolachlor dechlorination, we determined that green rust itself can only marginally contribute to transforming metolachlor. In contrast, metolachlor dechlorination was observed in a batch system containing magnetite or goethite and FeSO4 at pH 8. These results indicate that creating conditions favoring green rust facilitate Fe0-mediated dechlorination of metolachlor by providing an available source of Fe(II)/Fe(III) and generating iron oxide surfaces that can coordinate Fe(II). This information can be useful in designing and managing Fe0-treatment systems. ^
Agriculture, Soil Science|Environmental Sciences|Engineering, Environmental
Satapanajaru, Tunlawit, "Remediating chloroacetanilide -contaminated water using zerovalent iron" (2002). ETD collection for University of Nebraska - Lincoln. AAI3074099.