Adsorption property and mechanism of glutaraldehyde-crosslinked chitosan for removal of 2,4-dichlorophenoxyacetic acid from water

Abstract

In this work, glutaraldehyde-crosslinked chitosan (GCC) was prepared and its ability to remove 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions was systematically studied. Batch experiments on adsorption conditions, isotherm models, kinetic models, and thermodynamics were performed to evaluate the ability of GCC for 2,4-D removal from aqueous solution. Under optimal adsorption conditions, the adsorption capacity for 2,4-D reached 252.55 mg g⁻¹ with a dosage of 500 mg L⁻¹ at pH 3. The adsorption isotherm of 2,4-D could be represented by the Freundlich model due to the high R² (0.9986). Adsorption kinetics could be better represented by pseudo-second order kinetics (R² > 0.99). The effect of temperature and thermodynamic experiments illustrated that the adsorption was exothermic and spontaneous. For other two phenoxycarboxylic acid herbicides (4-chlorophenoxyacetic acid and 2-(2,4-dichlorophenoxy)propionic acid), GCC also showed good adsorption performance under identical experimental conditions. Meanwhile, GCC can remove 75.2% of 2-chlorophenoxyacetic acid (2-CPA), 77.9% of 4-CPA, and 87.2% of 2,4-D from diluted industrial effluent. The reusability experiments indicated that GCC retained its usability after being regenerated with ethanol for five cycles.