Elsevier

Applied Clay Science

Volume 46, Issue 3, November 2009, Pages 314-318
Applied Clay Science

Adsorption of herbicides 2,4-D and acetochlor on inorganic–organic bentonites

https://doi.org/10.1016/j.clay.2009.08.032Get rights and content

Abstract

Inorganic–organic bentonites were prepared by co-adsorption of cetyl trimethylammonium (CTMA) ions onto bentonites intercalated by poly(hydroxo aluminum) or poly(hydroxo iron) cations. The inorganic–organic bentonites adsorbed much more anionic herbicide 2,4-D than the inorganic and organic bentonites. For bentonites modified with poly(hydroxo iron) and CTMA ions, the enhancement may be attributed not only to the van der Waals interaction between 2,4-D and the organic cations, but also to the strong bonding of 2,4-D on the inorganic cations, which was confirmed by desorption studies, XRD measurements and FTIR analysis. The inorganic–organic bentonites did not show higher adsorption of acetochlor compared to the organo-bentonite. For such a nonionic herbicide, the van der Waals interaction dominated the adsorption, and the inorganic modification did not make an obvious contribution to the adsorption.

Introduction

Pesticides are recognized as an important source of potential pollution to soil and water due to their mobility and degradation in soils (Nir et al., 2006, Arias-Estévez et al., 2008). Among these pesticides, 2,4-D (2,4-dichlorophenoxyacetic acid) is an anionic herbicide whereby the water solubility depends on the pH of solution. It is widely used on wheat, maize and rice to control broad-leaf weeds. As most anionic contaminants, 2,4-D is weakly adsorbed by soil particles and poses a threat of surface and ground water contamination. Acetochlor (2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl) acetamide) is a nonionic herbicide that inhibits the protein synthesis of weeds in cropland. It is widely used in China and many other countries, and considered as an herbicide with a high leaching potential, and easily transported into water bodies (Rebich et al., 2004).

Clay minerals have high specific surface areas associated with their small particle size. After surface modification with inorganic or organic cations, they can be used as adsorbents for many hazardous herbicides to eliminate these pollutants from water (Hermosín and Cornejo, 1992, Pal and Vanjara, 2001, Yaron-Marcovich et al., 2004, Neitsch et al., 2006). The modified clay minerals are also used in formulations of pesticides to control the release of active ingredients and decrease the environmental impact of herbicides (Gerstl et al., 1998, Undabeytia et al., 2000, Fernández Pérez et al., 2000, Lagaly, 2001, Celis et al., 2002, Nir et al., 2006, Flores Céspedes et al., 2007, Li et al., 2008). Recently, inorganic–organic clay minerals, namely clay minerals modified with both inorganic and organic cations, demonstrated higher adsorption of organic pollutants (Bouras et al., 2001, Bouras et al., 2007, Wu et al., 2001, Zhu and Zhu, 2007). The present work is aimed to develop adsorbents having enhanced adsorption of the anionic herbicide 2,4-D and the nonionic herbicide acetochlor. For this purpose, inorganic–organic bentonites were prepared by intercalation of poly(hydroxo aluminum) or poly(hydroxo iron) cations, followed by intercalation of cetyl trimethylammonium (CTMA) ions.

Section snippets

Materials

Technical grade herbicides 2,4-D (98.2% pure) and acetochlor (96.2% pure) (Fig. 1) were purchased from Hangzhou Qingfeng Agrochemicals Co. Ltd., China. The bentonite (denoted Na-bent) consisting mainly of Na+-montmorillonite was purchased from Zhejiang, China. It was produced by ion exchange of calcium-bentonite with Na2CO3 by the manufacturer. The product was washed and dried at 115 °C before use in our experiments. The cation exchange capacity (CEC) of the dried Na-bent was 0.570 mmol g 1. Cetyl

Characterization of bentonites

The specific surface area of Al-bent and Fe-bent was enhanced in comparison with the original Na-bent (Table 1). The basal spacing was also increased, indicating that the interlayer space of montmorillonite was partly occupied by poly(hydroxo metal) cations. As reported previously (Bottero et al., 1988, Michot and Pinnavaia, 1992), Al13 polycations [Al13O4(OH)24(H2O)12]7+ predominate in the hydrolyzed Al3+ solutions when a [OH]/[Al3+] molar ratio of 2.0–2.4 was used. These Al13 species may

Conclusions

Pillared bentonites with subsequent adsorption of cetyl trimethylammonium ions showed enhanced 2,4-D adsorption in comparison with organo-bentonites but did not show higher adsorption of acetochlor. Thus, inorganic–organic bentonites are a good choice for removing certain pollutants from water and potential carriers for controlled release.

Acknowledgements

This work was supported by the Natural Science Foundation of Zhejiang Province (Y506288) and the Natural Science Foundation of China (30500387).

References (36)

Cited by (65)

  • Rapid and efficient removal of acetochlor from environmental water using Cr-MIL-101 sorbent modified with 3, 5-Bis(trifluoromethyl)phenyl isocyanate

    2020, Science of the Total Environment
    Citation Excerpt :

    The result showed that PC value of Cr-MIL-101-BTP was 356.14 mg/g/μM at a lower concentration of 5 mg/L ACT, which was found as the outperformer in all tested subjects. According to the above results, Cr-MIL-101-BTP exhibited efficient performance at both low and high concentrations of ACT which reveals the great advantage of our strategy by using Cr-MIL-101-BTP as potential adsorbents for ACT cleanup (Li et al., 2009; Wang et al., 2018a). To further demonstrate the potentiality of Cr-MIL-101-BTP with high sorption capacity, column sorption experiment was undertaken to explore the sorption performance under flowing status.

View all citing articles on Scopus
View full text