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Enhancing Metolachlor Destruction Rates with Aluminum and Iron Salts during Zerovalent Iron Treatment
Author(s) -
Satapanajaru T.,
Comfort S. D.,
Shea P. J.
Publication year - 2003
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2003.1726
Subject(s) - metolachlor , chemistry , zerovalent iron , environmental remediation , inorganic chemistry , aqueous solution , iron sulfate , kinetics , salt (chemistry) , aluminium , environmental chemistry , nuclear chemistry , adsorption , pesticide , contamination , sulfate , organic chemistry , ecology , atrazine , physics , quantum mechanics , agronomy , biology
Pesticide‐contaminated soil may require remediation to mitigate ground and surface water contamination. We determined the effectiveness of zerovalent iron (Fe 0 ) to dechlorinate metolachlor [2‐chloro‐ N ‐(2‐ethyl‐6‐methylphenyl)‐ N ‐(2‐methoxy‐1‐methyl ethyl) acetamide] in the presence of aluminum and iron salts. By treating aqueous solutions of metolachlor with Fe 0 , we found destruction kinetics were greatly enhanced when Al, Fe(II), or Fe(III) salts were added, with the following order of destruction kinetics observed: Al 2 (SO 4 ) 3 > AlCl 3 > Fe 2 (SO 4 ) 3 > FeCl 3 A common observation was the formation of green rusts, mixed Fe(II)–Fe(III) hydroxides with interlayer anions that impart a greenish‐blue color. Central to the mechanism responsible for enhanced metolachlor loss may be the role these salts play in facilitating Fe(II) release. By tracking Al and Fe(II) in a Fe 0 + Al 2 (SO 4 ) 3 treatment of metolachlor, we observed that Al was readily sorbed by the corroding iron with a corresponding release of Fe(II). The manufacturing process used to produce the Fe 0 also profoundly affected destruction rates. Metolachlor destruction rates with salt‐amended Fe 0 were greater with annealed iron (indirectly heated under a reducing atmosphere) than unannealed iron. Moreover, the optimum pH for metolachlor dechlorination in water and soil differed between iron sources (pH 3 for unannealed, pH 5 for annealed). Our results indicate that metolachlor destruction by Fe 0 treatment may be enhanced by adding Fe or Al salts and creating pH and redox conditions favoring the formation of green rusts.