Degradation Characteristics of Nicosulfuron in Water and Soil by MnO2 Nano-Immobilized Laccase.

Abstract

As a typical sulfonylurea herbicide, nicosulfuron is mainly used to control grass weeds and some broadleaf weeds in corn fields. However, as the amount of use continues to increase, it accumulates in the environment and eventually becomes harmful to the ecosystem. In the present study, a new metallic nanomaterial, δ-MnO2, was prepared, which not only has a similar catalytic mechanism as laccase but also has a significant effect on pesticide degradation. Therefore, the bicatalytic property of MnO2 can be utilized to improve the remediation of nicosulfuron contamination. Firstly, MnO2 nanomaterials were prepared by controlling the hydrothermal reaction conditions, and immobilized laccase was prepared by the adsorption method. Next, we investigate the effects of different influencing factors on the effect of immobilized laccase, MnO2, and free laccase on the degradation of nicosulfuron in water and soil. In addition, we also analyze the metabolic pathway of nicosulfuron degradation in immobilized laccase and the bicatalytic mechanism of MnO2. The results demonstrated that the degradation rate of nicosulfuron in water by immobilized laccase was 88.7%, and the optimal conditions were 50 mg/L, 25 h, 50 °C, and pH 5. For nicosulfuron in soil, the optimal conditions for the degradation by immobilized laccase were found to be 151.1 mg/kg, 46 °C, and pH 5.9; under these conditions, a degradation rate of 90.1% was attained. The findings of this study provide a theoretical reference for the immobilized laccase treatment of sulfonylurea herbicide contamination in water and soil.