Adsorption of isoxaflutole degradates to aluminum and iron hydrous oxides.

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摘要：

Isoxaflutole (IXF) is a pre-emergence herbicide that has been marketed as a substitute for atrazine. It is rapidly transformed to a more stable and soluble diketonitrile degradate (DKN) after field application and, subsequently, DKN can be further degraded to a benzoic acid derivative (BA) within soil. However, no previous research has been conducted to investigate DKN and BA sorption to metal oxide minerals. The primary objective of this research was to elucidate the interactions of DKN and BA with variable-charged soil solid phase constituents to further understand how these IXF degradates are retained by metal oxides. The DKN and BA degradates were adsorbed to hydrous aluminum and iron oxides, and the data were well described by the Freundlich model (R**2 > 0.91) with N values ranging from 0.89 – 1.2. Adsorption isotherms and Kd values demonstrate BA is adsorbed to HFO to a greater extent than previously observed for other IXF degradate–mineral reactions. The degree of hysteresis between adsorption/desorption isotherms was characterized as slight (Hysteresis Index values < 1.7), suggesting weak degradate retention to Fe and Al oxide surfaces. Degradate adsorption was observed to greatly diminish as suspension pH increased. Attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectra show no evidence that DKN or BA adsorb to mineral surfaces as inner-sphere complexes under hydrated conditions. Instead, DKN and BA adsorb to positively-charged metal oxide surfaces as outer-sphere or diffuse ion swarm complexes via electrostatic attraction. This research indicates that metal oxides can serve as important adsorbents for DKN and BA in acidic soils enriched with metal oxides.

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关键词：

Atmospheric aerosols Absorption coefficients Angstrom absorption exponent UV

DOI：

10.2134/jeq2010.0338

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年份：

2011