Abstract
Drift deposition of emerging and carcinogenic contaminant dicamba (3,6-dichloro-2-methoxy benzoic acid) has become a major health and environmental concern. Effective removal of dicamba in aqueous medium becomes imperative. This study investigates the adsorption of a promising adsorbent, MIL-101(Cr) metal-organic framework (MOF), for the removal of dicamba in aqueous solution. The adsorbent was hydrothermally synthesized and characterized using N2 adsorption-desorption isotherms, Brunauer, Emmett and Teller (BET), powdered X-ray diffraction (XRD), Fourier Transformed Infrared (FTIR) and field emission scanning electron microscopy (FESEM). Adsorption models such as kinetics, isotherms and thermodynamics were studied to understand details of the adsorption process. The significance and optimization of the data matrix, as well as the multivariate interaction of the adsorption parameters, were determined using response surface methodology (RSM). RSM and artificial neural network (ANN) were used to predict the adsorption capacity. In each of the experimental adsorption conditions used, the ANN gave a better prediction with minimal error than the RSM model. The MIL-101(Cr) adsorbent was recycled six times to determine the possibility of reuse. The results show that MIL-101(Cr) is a very promising adsorbent, in particular due to the high surface area (1439 m2 g−1), rapid equilibration (~25 min), high adsorption capacity (237.384 mg g−1) and high removal efficiency of 99.432%.
Highlights
Anthropogenic activities such as crop cultivation, industrial processes and sewage discharge result in the contamination of surface and ground water resources [1]
The BET surface area of the metal-organic framework (MOF) is 1439 m2 g−1, as highlighted in Table 1 and Figure 1a, which is typical of highly porous materials
The diffraction pattern of the MIL101(Cr) (Figure 1b) adsorbent indicates peaks that are in agreement with those reported in previous studies [30,31], confirming a well-formed crystallite structure of the MOF
Summary
Anthropogenic activities such as crop cultivation, industrial processes and sewage discharge result in the contamination of surface and ground water resources [1]. Herbicides such as dicamba (3,6-dichloro-2-methoxy benzoic acid) are widely used to selectively kill broad leave weeds that affect crop areas, gardens and road sides [2]. Drift deposition of dicamba to non-intended areas has become a major environmental concern, as it directly affects vulnerable crops even at low concentrations [4]. States of America (USA), an estimate of 1.5 million hectares of non-target soybeans were destroyed by dicamba herbicides in 2017 due to uncontrolled drift and extend to 2018.
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