Reductive transformation of 2,4-dichlorophenoxyacetic acid by nanoscale and microscale Fe3O4 particles |
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Authors: | You B Si Guo D Fang Jing Zhou Dong M Zhou |
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Institution: | 1. School of Resources and Environment , Anhui Agricultural University , Hefei, China;2. State Key Laboratory of Soil and Sustainable Agriculture , Institute of Soil Science, Chinese Academy of Science , Nanjing, China;3. School of Resources and Environment , Anhui Agricultural University , Hefei, China;4. State Key Laboratory of Soil and Sustainable Agriculture , Institute of Soil Science, Chinese Academy of Science , Nanjing, China |
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Abstract: | Reductive transformation of 2,4-dichlorophenoxyacetic acid (2,4-D) by nanoscale and microscale Fe3O4 was investigated and compared. Disappearance of the parent species and formation of reaction intermediates and products were kinetically analyzed. Results suggest that the transformation of 2,4-D followed a primary pathway of its complete reduction to phenol and a secondary pathway of sequential reductive hydrogenolysis to 2,4-dichlorophenol (2,4-DCP), chlorophenol (2-CP, 4-CP) and phenol. About 65% of 2,4-D with initial concentration of 50 μ M was transformed within 48 h in the presence of 300 mg L?1 nanoscale Fe3O4, and the reaction rates increased with increasing dosage of nanoscale Fe3O4. The decomposition of 2,4-D proceeded rapidly at optimum pH 3.0. Chloride was identified as a reduction product for 2,4-D in the magnetite–water system. Reductive transformation of 2,4-D by microscale Fe3O4 was slower than that by nanoscale Fe3O4. The reactions apparently followed pseudo-first-order kinetics with respect to the 2,4-D transformation. The degradation rate of 2,4-D decreased with the increase of initial 2,4-D concentration. In addition, anions had a significant adverse impact on the degradation efficiency of 2,4-D. |
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Keywords: | 2 4-D Fe3O4 nanoparticles dechlorination degradation |
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