Adsorption and Sustained‐Release Capacity of Glyphosate on Microporous Corn Starch
2021
Dong, Xiaoting | Bai, Yifan | Ma, Xian | Xue, Pengli | Zhang, Yan | Bian, Liujiao
Glyphosate is a non‐selective, residue‐free herbicide that can pollute soil and water sources due to its extensive use and long‐term accumulation. The adsorption and release processes of glyphosate on corn microporous starch microspheres are studied. The results reveal that the adsorption capacities of glyphosate on native corn starch, corn microporous starch, and corn microporous starch with xanthan gum increase in turns. Further, the maximum adsorption capacity of the corn microporous starch with xanthan gum reaches 138.89 mg g⁻¹ at 283 K. Moreover, the adsorption of glyphosate follows the Langmuir isothermal adsorption equation and quasi‐secondary adsorption kinetic model on the three corn starches, which are all spontaneous exothermic processes controlled by enthalpy change. In the desorption process, glyphosate is slowly released on corn microporous starch with the addition of 0.02% xanthan gum with a cumulative release of ≈61% ± 3.17% after 48 h. The release kinetics follows the Ritger–Peppas release model, which is consistent with the Fick diffusion mechanism. These results indicate that the corn microporous starch with 0.02% xanthan gum is a well controlled‐ and sustained‐release carrier of glyphosate. This study provides some useful insight into the development of glyphosate sustained‐release preparations with high loading and long sustained‐release performance.
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