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Published on: October 18, 2018
Spectroscopic study of dinitrophenol herbicide sorption on smectite
C T Johnston1, G Sheng, B J Teppen
1Department of Crop, Soil and Environmental Sciences, 1150 Lilly Hall, Purdue University, West Lafayette, Indiana 47907-1150, USA. clays@purdue.edu
Environmental Science & Technology
|January 14, 2003
Summary
This study reveals that dinitrophenolic herbicides like DNOC and DINOSEB strongly bind to smectite clay surfaces through interactions with cations and the clay surface. This understanding aids in predicting herbicide behavior in the environment.
Area of Science:
- Environmental Chemistry
- Clay Mineralogy
- Analytical Chemistry
Background:
- Dinitrophenolic herbicides, such as 4,6-dinitro-o-cresol (DNOC) and 4,6-dinitro-2-sec-butylphenol (DINOSEB), are widely used but their environmental fate is influenced by soil components.
- Smectite clays are key soil minerals that can sorb organic contaminants, affecting their bioavailability and transport.
Purpose of the Study:
- To investigate the sorption mechanisms of DNOC and DINOSEB onto smectite clay.
- To quantify the sorption behavior and determine the detection limits of analytical methods for these herbicides in clay matrices.
Main Methods:
- Fourier Transform Infrared (FTIR) spectroscopy to analyze molecular interactions and vibrational modes.
- High-Performance Liquid Chromatography (HPLC) for quantitative analysis of herbicide concentrations.
- Quantum chemical calculations to model and predict spectral shifts.
Main Results:
- DNOC and DINOSEB exhibit high affinity for smectite surfaces, driven by interactions with exchangeable cations and van der Waals forces.
- Cation coordination to the nitro groups (-NO2) was confirmed by shifts in vibrational modes, consistent with quantum chemical predictions.
- FTIR-derived sorption isotherms and molar absorptivity values for DNOC on K-SWy-2 smectite agreed well with HPLC measurements, establishing a detection limit of approximately 5 μg DNOC/g clay.
Conclusions:
- The sorption of dinitrophenolic herbicides to smectite is primarily governed by cation exchange and surface interactions, rather than the specific type of smectite.
- FTIR spectroscopy provides a reliable method for quantifying herbicide sorption and determining detection limits, linking molecular-level interactions to macroscopic observations.
