Sorption and Desorption of Atrazine on Natural Bentonite and Organically Modified Bentonite

Document Type : Original Article

Authors

1 Water Resources and Desert Land Division, Desert Research Center, Cairo, Egypt.

2 Soil and Water Sciences Dept., Faculty of Agric., Alexandria University, Egypt.

Abstract

In order to increase the effectiveness of bentonite clay in the retention of atrazine, natural bentonite clay was modified using humic acid and hexadecyltrimethylammonium bromide (HDTMA) as the intercalation agent and a cationic surfactant at 100 % of the cation exchange capacity. Such organic modification changes the nature of clay from hydrophilic to hydrophobic, which insures surfactant loading. The performance of the natural and modified bentonite was evaluated in terms of elemental analysis, BET surface area, X-ray diffraction (XRD), FTIR spectroscopy, and thermogravimetric analysis (TGA). The batch equilibrium technique was applied to conduct atrazine adsorption/desorption isotherms with the natural and the modified bentonite. The data fitted well to the simple linear and Freundlich adsorption isotherms while desorption data agreed with Freundlich adsorption only. Desorption kinetic was successfully fitted with the first order reaction model. Natural bentonite was a poor adsorbent of atrazine with distribution coefficient of Kd = 3.07 ± 0.04 L kg-1. The complexion with humic acid did not improve atrazine adsorption on bentonite, Kd = 2.15 ± 0.14 L kg-1, whereas, the HDTMA-bentonite exhibited high affinity to sorb atrazine with Kd value of 197.97 + 0.77 L kg-1. Natural bentonite and humic-bentonite clearly exhibited nonsingularity of sorption/desorption isotherms. The desorption curve of HDTMA-bentonite revealed that the sorption of atrazine is reversible with no hysteresis. These results indicate the potentiality of HDTMA-bentonite for environmental applications.

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