Removal of 2,4-D herbicide from aqueous solution by aminosilane-grafted mesoporous carbons

Abstract

2,4-Dichlorophenoxyacetic acid (2,4-D) is the most commonly used herbicide in plant protection products. 2,4-D is poorly biodegradable and it is often found in aquatic environment. The development of an effective way to reduce the amount of this toxic contaminant from aqueous solution became an urgent issue. Therefore, in this study series of aminosilane-grafted mesoporous carbons were synthesized, characterized and then applied as adsorbents for 2,4-D. The impact of various factors such as the contact time (0–360 min) of herbicide with adsorbents, pH (2–11), temperature (25, 45, 60 °C) and initial concentration (6.25–150 mg/l) of the 2,4-D on the sorption capacity of materials was analyzed. The results proved that functionalization of mesoporous carbons with aminosilane increased the sorption capacity (qe = 142–191 mg/g) towards herbicide compared to pristine material (qe = 109 mg/g). The functional groups presented on the surface of materials enhanced the interaction between mesoporous carbons and herbicide. The most effective adsorbent for 2,4-D was the material that had the highest amount of basic groups on the surface (2.79 mmol/g) of all samples tested (0.06–0.52 mmol/g). For all studied materials the Langmuir model was the most suitable to describe the isotherms of 2,4-D adsorption (R2 = 0.999). While the kinetics of herbicide adsorption on the functionalized mesoporous carbons were best fitted to the pseudo-second-order model. The presented study proved that the aminosilane-grafted mesoporous carbons could be promising adsorbents for effective removal of 2,4-D from aqueous environment.